THE UNIVERSITY OF TEXAS BULLETIN No. 3232: August 22, 1932 THE GEOLOGY OF TEXAS Volume 1 Stratigraphy By E. H. SELLAROS, W. S. ADKINS, AND F. B. PLUMMER Bureau of Economic Geology E. H. Sellards, Director PUBLISHED BY THE UNIVERSITY OF TEXAS AUSTIN Publications of The University of Texas Publications Committees: GENERAL: FREDERIC DUNCALF C. H. SLOVER J. F. DOBIE G. W. STUMBERG J. L. HENDERSON A. P. WINSTON H. J. MULLER OFFICIAL: E. J. MATHEWS L. L. CLICK C. F. ARROWOOD C. D. SIMMONS E. C. H. BANTEL BRYANT SMITH The University publishes bulletins four times a month, so numbered that the first two digits of the number show the year of issue and the last two the position in the yearly series. (For example, No. 3201 is the first bulletin of the year 1932.) These bulletins comprise the official publica­tions of the University, publications on humanistic and scientific subjects, and bulletins issued from time to time by various divisions of the University. The following bureaus and divisions dü;tribute bulletins issued by them; communications concerning bulletins in these fields should be addressed to The University of Texas, Austin, Texas, care of the bureau or division issuing the bulletin: Bureau of Business Research, Bureau of Economic Geology, Bureau of Engineering Research, Interscholastic League Bureau, and Division of Extension. Communications concerning all other publications of the University should be addressed to University Publications, The University of Texas, Austin. Additional copies of this publication may be procured from the Bureau of Economic Geology, The University of Texas, Austin, Texas THE UNIVERSITY OF TEXAS PRES! ~ No. 3232: Aupst 22, 1932 THE GEOLOGY OF TEXAS Volume 1 Stratigraphy By E. H. SEI!LARDS, W. S. ADKINS, AND F. B. PLUMMER Bureau of Economic Geology E. H. Sellards, Director PUaL18HED aY THIE UNIVERSITY FOUR TIMES A MONTH AND ENTERED A8 8ECOND•CLAU MATTER AT THE POSTOFFICE AT AUSTIN, TEXAS, UNDER THE ACT OF AUGUST 24, 1912 The University of Texas Bulletin No. 3232 PAGB El Paso and Van Horn regions----------------------------------------------------------62 Bliss formation --------62 Van Horn formation..______________________________________ __ _______________ 63 Marathon and Solitario uplifts 64 Dagger Flat formation_________________________________________________ 64 Solitario uplift ----------------------------------------65 Underground position of the Cambrian in Texas_______________________ 66 Cambrian seas in the Texas region___________________________ 67 Relation of the Texas Cambrian to that of the adjoining states_______ 68 Ordovician system -----------···-·-------------------------------------------------------------69 Llano region --------------------------------------------------------------------------------------70 Ellenburger group --------------------------------------------------------------------70 Gasconade equivalent ------·---------·-------------------------------- --------------------70 Roubidoux equivalent --------------------------------·-----------------------------71 Jefferson City and Cotter _equivalents.--------------------------------------------72 Van Horn and El Paso regions·-----------------------------------------------------------74 El Paso fonnation ··------------·--------------------------------------------------------------74 Montoya formation ---------------------------------------------------------------75 Marathon arid Solitario regions.---------------------------------------------------·-----------76 Marathon formation ------------------------------------------------------------------76 Alsate formation -----------------------------------------------------------------------77 Fort Peña formation -----------------------------------------------------------------77 Woods Hollow formation____ _____________________________________ _ _________________ 78 Maravillas formation ---------------------··----------------------------78 Underground position of the Ordovician in Texas _____________________________ 80 Ordovician seas in the Texas region____________ _________________________ _ _______ 81 Relation of the Texas Ordovician to that of the adjoining states___ 83 Silurian system -------------------------------------------------------------------------------------------84 El Paso and Van Horn regions_________________________________ _____________ 84 Fusselman formation -------------------------··-···----------------------84 Underground position of the Silurian in Texas . ---------------------------------85 Silurian seas in the Texas region ---------------------------------------------------------85 Relation of the Texas Silurian to that of adjoining states -----------------86 Devonian system -----·------------------------------------------------------------------------------86 Marathon and Solitario regions -----------------·-------------------------------87 Caballos formation -----·-------------------------------------------------------------87 El Paso and Van Horn regions ---------------------------------------------------------88 Percha formation -----------------------------------------------------------------88 Underground position of the Devonian in Texas -------------------------------89 Devonian seas in the Texas region ---------------------------·-------------------------89 . !le~ati?n of the Texas Devonian to that of the adjoining states ______ 90 M1ss1ss1pp1an system -----------------------------------------------------------------90 Llano region ---------------------------------------------------··-----------------------91 Osage group ----------------------------------------------------------------------·----91 Chappel formation ---------------------------------------------------------91 Chester group -----------------------------------------------··----------------92 Barnett formation -----------------------------------------------92 Hueco Mountains ------------------------------------------------------------------------94 Helms group -------------------------------···----------------·-·--94 Marathon and Solitario regions..------------------------------------------95 U'!-d~rg;i-ou?d positi?n of the Mississ~ppian in Texas_______________________ 95 M1ss1ss1ppian seas m the Texas reg1on ----------------------·--------------------96 Relation of the Texas Mississippian to that of the adjoining states .... 97 Pennsylvanian system ------------------------------···--··--------------98 Llano region ----------------------------------------------------------99 Bend group ------··------------------------------------··-··-·----------------------------100 Marble Falls formation -·-··---------------------------------------------------------100 Smithwick formation ------------------------------------------------------101 Contents PACE Osage Plains region of north-central Texas--------------------------101 Strawn group ------------------------------------106 Millsap Lake formation.________________ _____________________________ 107 Garner formation ----------------------------------------100 Mineral Wells formation -----------------------------------------108 Canyon group ------------------------------------110 Palo Pinto formation____________________________________________ 110 Graford formation --------------------------------111 Brad formation -------112 Caddo Creek formation.._ ______________ ___________ 112 Cisco group ---------------113 Graham formation -----------------------------------------113 Thrifty formation -----------------------------------------------114 Harpersville formation -----------------------------------------------------115 Pueblo formation ------------------------------------------------------------115 Hueco Mountains --------------------------------------------------------------------115 Bend and Magdalena groups__________________________________________________ 116 Diablo Mountains -----------------------------------------------------------------------------116 Bend group ------------------------------------------------------------------------------117 Magdalena group --------------------------------------------------------------------------117 Marathon and Solitario regions___________________________________________________________ 117 Tesnus formation --------------------------------------------------118 Dimple formation -------------------------------------------------------------------------120 Haymond formation ------------------------------------------------------------120 Gaptank formation -------------------------121 Underground position of the Pennsylvanian in Texas_____________ 122 Pennsylvanian seas in the Texas region______________________________________ 125 Relation of the Texas Pennsylvanian to that of adjoining states______ 127 Paleozoic of the Llanoria geosyncline_______________________________________ ________ ____ 127 Pennsylvanian-Permian contact -----------------------------------------------------------14-0 Permian system ------------------------------------------------------------------------------145 Glass Mountains ------------------------------------------------------------------------------146 Wolfcamp formation ---------------------------------------------------------------------148 Hess formation ---------------------------------------------------149 Leonard formation ---------------------------------------------------------150 Word formation ----------------------------------------------------------151 Capitan formation ---------------------------------153 Bissett formation --------------------------------------------------------154 Sierra Madera Dome--------------------------------------155 Guadalupe, Delaware, and Apache Mountains____ ______________ _______________ 156 Leonard formation -------------------------------------------------------------157 Delaware Mountain formation_____________________________ _ 158 Capitan formation --------------------------------------------------------159 Castile formation ------------------------------------------------------------------160 Rustler formation --------------------------------------------------------161 Diablo Plateau -------------------------------------------------------------------------162 Chinati Mountains -----------------------------------------------------------163 Cieneguita formation -------------------------------------------------------------164 Alta formation -----------------------------------------------------------------------165 Cibolo formation ------------------------------------------------------------------165 Osage Plains region-------------------------------------------165 Wichita group --------------------------------------------------------------------170 Moran formation --------------------------------------------------------171 Putnam formation -------------------------------------------------------------172 Admiral formation ----------_____ 172 Belle Plains formation_________________ _____________________ 173 Clyde formation --------------------------173 Lueders formation --------------------------------174 PAGE c1~~~;;:r~r*~!f~~::::=:=:::=::::::=:=:==::::::::=::=::=::=::::::=:=::::::=::=::=::: ~~i Choza formation -------------------------------------------------------------------------176 Double Mountain group__ __ _ ________ _ ______________________ __________________________ 177 San Angelo formation-----------------------------------------------------------------------178 Blaine formation -------------------------------------------------------------------------178 Whitehorse-Cloud Chief-Quartermaster formations ---------------------179 Underground position of the Permian in Texas ________ ___ __________________ 180 Permian seas in the Texas region_ ______________________ ____ __ ___________________ 185 Relation of the Texas Permian to that of the adjoining states -----------186 _ Close of the Paleozoic___ __ _ _____________________________ _____________________________ _:____ 186 Stratigraphic data from wells ___ ---------------------------------------------------------187 Wells entering Paleozoic of the Llanoria geosyncline -----------------------------187 Wells entering pre-Pennsylvanian formations, foreland facies _____________ 192 Illustrations of sorne Paleozoic fossils__________ _ ________ _______________________________ 230 Explanation of Plates 11-VL_________________ _ ________________________________________ 231 Part 2 THE MESOZOIC SYSTEMS IN TEXAS, by W. S. Adkins ____________________ __ __ __ 239 Triassic system ________ ------------------------------------------------------------------------------240 Dockum group --------------------------------------------------------------------------------------242 Areal geology ------------------------------------------------------------------------2iW Southern Llano Estacado_____________________________________________________ _____ 249 Central Llano Estacado_______________________________ _ ________________ _ ______ 251 Northern Llano Estacado_ ___ ____ _ _ _____ _ ______________ _ __ ---------------------252 J urassic system ----------------------------------------------------------------------------------------253 Marine Jurassic in Texas ________________________________________________________ __ ______ 254 Malone formation (restricted) ___________________________________________________ 254 Nbers in the bibliograpby. lO'J'be temi Llanoria has aleo been used. However, an inquiry made in 1930 indicates preference on the part of geolocista most directly concemed for the term Llanoria. The University of Texas. Bulletin No. 3232 ably from a land mass in northem Mexico (Columbia). The geo­syncline bordering Llanoria, trending southwest, curved westward and united with the geosyncline bordering Columbia. On this sub­ject more exact data will doubtless accumulate as well drilling continues. Additional information on the sedim~nts that accumu­lated in this geosyncline is given subsequently in the description of the Paleozoic of the Llanoria geosyncline. While the northwestern margin of the land mass Llanoria is thus to sorne extent located, the southeastern extent is not so well known. Whether the land mass occupied the whole of the present Gulf region, or only a part of the Coastal Plain, or, as is probable, varied in extent in the successive Paleozoic periods, is at this time but imperfectly known. That the land mass was large and was suc~ cessively re-elevated is evident from the quantity of sediments de­rived from it during the severa! Paleozoic periods. Columbia.-A land area in northern Mexico adjacent to, and probably extending into, Texas has been described by Schuchert under the name Columbia (1382b, p. 470), and by Willis under the name Mexia (176le, plate facing p. 301)_. The Marathon and Solitario basins of Texas are within a geosyncline at the north mar­gin of this land mass. Eastward, Columbia is adjacent to, and may have been continuous with, Llanoria. Siouxia.-The Paleozoic land area Siouxia ( also written Siouis), is defined by Schuchert (1385b, p. 1224), as occupying in early Pal­eozoic time much of the Great Plains area, extending west to Colo­rado, Wyoming, and New Mexico, south into Texas, and east into lowa. Near its western margin, mountain ranges described as the Ancestral Rockies were raised in late Paleozoic time.11 That the land mass Siouxia supplied sediments to the Texas seas cannot at present be shown, and its extension into Texas may he questioned. On the other hand, the land areas, Llanoria and Columbia, supplied a large amount of sediments into the Texas region during Paleozoic time. Paleozoic Seas.-The region of Paleozoic deposition in Texas was the broad depression between Llanoria on the southeast and Siouxia llA.mong publications relating to Siouxia and the Ancestral Rock.fes are the following, listed in the bibliography: Lee, 978, 978a; Melton, 1087a; Schuchert, 1382b, 1383, 1385b; Ver Wiebe, 1694. The Geology of Texas-Introduction on the northwest. In early Paleozoic time, immediately adjacent to Llanoria and its westward extension, Columbia, was the narrow trough already referred to as probably extending entirely across Tex­as from the Ouachita region of Oklahoma-Arkansas to the Marathon­Solitario region of west Texas. This trough will be referred to as the Llanoria geosyncline. North and west of this trough was a hroad depression through central Texas which Schuchert has called the Ouachita embayment (1382g, p. 181). At times the seas were probahly entirely withdrawn from both the Ouachita emhayment and the Llanoria geosyncline, and at other times flooded extensive areas. An inward migration of folding is recognized (Ulrich, 1674b, p. 435, 597; Cheney, 246), by which, in late Paleozoic, this depressed area was moved westward, receiving thick Pennsylvanian and Permian deposition. This broad depression to the west and north of these land masses is then the principal theater of Paleozoic deposition in Texas. MESOZOIC LANDS AND SEAS The Mesozoic witnessed great changes in the pos1tion of land masses in Texas. Early Mesozoic (Triassic) was a time of conti· nental elevation in this region and no marine Triassic is known in the state. The non-marine deposits found in west Texas indicate extensive land masses at this time, to the east in Texas and to the west in New Mexico. This condition of continental elevation seems to have extended into Jurassic time since no deposits of early Jurassic age are known in the state. Since marine deposits are not known to have been laid down in Texas during approximately the first half of the Mesozoic, it is probable that during this time the -continent stood at such elevation as to exclude the sea from the Texas region. The Gulf margin of Texas, however, is so deeply buried by later deposits that the presence or ahsence of early Mesozoic cannot he determined. It is not impossible that early Mesozoic seas encroached on the Gulf margin hut no records are at present available. In late Jurassic time an invading sea extended northward through Mexico into Texas, the deposits from this sea now exposed at the surface heing found in Hudspeth County. Whether or nota Jurassic sea also entered Texas on the Gulf margin at this time, is unde­termined from lack of records. The University of Texas, Bulletin No. 3232 Progressive inundation brought the seas during the Cretaceous northwards entirely across Texas. These changes of both lands and seas are more fully discussed in the chapter on Mesozoic stratig­raphy. For the purpose of this introductory chapter, it is sufficient to bear in mind that at sorne time following the close of the Paleozoic, and probably by or before late Jurassic, a fundamental change in land distribution had occurred by which the coastal belt of Texas, which had stood relatively high through Paleozoic, was depressed and gradually became submerged by a sea encroaching from the south and southwest. As a result of this profound change of land level, drainage in the Texas region was reversed. lnstead of a northwestward drainage into inland Paleozoic seas, drainage was thereafter southeastward towards the advancing Cretaceous seas. The flooding reached its maximum in early Upper Cretaceous time, largely withdrew at the close of Cretaceous, and was followed by the great Laramide revolution which brought into existence the Rocky Mountain system. Thus the Mesozoic witnessed a complete change in the position of land masses in the Texas region. The extensive high lands of the eastern part of the state, inherited from Paleozoic time, continued into early Mesozoic, but by depression passed into the low lying coastal belt of late Mesozoic time. On the other hand, the central and western parts of the state, which had been the great theater of Paleozoic deposition, although extensively flooded in late Mesozoic, yet emerged at the close of the era as a great continental land mass. These profound changes in elevation, with the resulting reversal of drainage, give for the last half of Mesozoic and later time an entirely di:fferent theater of accumulation of sediments to that of Paleozoic time. CENOZOIC LANDS AND SEAS In distribution of land and seas, the Cenozoic records an approach to, and final merging into, modero conditions. The Gulf of Mexico then as now controlled drainage, and the incursions of the sea may be regarded as enlargements of the Gulf of varying extent overlapping onto the adjacent margins. In a large way the Mesozoic and Cenozoic may be looked upon as a unit development in the Texas region, recording depression to such extent as at first to lower a great land mass to submerged condition, and subsequently, The Geology of Texas-lntroduction in part through fluctuation hut in the main through continued suhsidence, to hury the land mass by sediments to a depth, at its gulfward side, of many thousand, prohahly more than twenty thousand feet. By reversa} of drainage, much of the rock detrital that had heen moved westward during Paleozoic time was returned eastward during late Mesozoic and Cenozoic time. The flow of streams and the quantity and kind of materials carried were affected by fluctuations in elevation, which will he more fully descrihed in the chapters on Mesozoic and Cenozoic stratigraphy. Profound among these changes in elevation were those by which the present Rocky Mountains were made. The long interval represented by the accumulation of these sedi­ments and by the changes in land distribution witnessed likewise slow hut amazing changes in organic life upon the face of the earth. The imperfectly known organisms of the Archeozic and Proterozoic were succeeded by the relatively simple, wholly marine invertehrates of the early Paleozoic, and these in turn are followed by the rich marine and land faunas and floras of the later Paleozoic. Air hreathing, as distinct from water breathing; land hahitat, as distinct from water hahitat; the bony structure of vertehrates; and the vascular structure and seed-hearing habit of plants are among the outstanding advances of the late Paleozoic. Mesozoic time witnessed profound changes, notably in the more complete occupation of the land by reptilian faunas; the diversity of insects, and the resulting development of the flowering plants; the advent of flying reptiles and of hirds; and hefore the close of the era the appearance of the primitive mammalian stock. The Cenozoic leads to the present through the development of a magnificent mammalian fauna; the appearance and dominance of man; and the dwarfing of this great fauna to which unhappy result man on the American as well as on the European continents has so largely contrihuted. Summarizing, it may be said that for the long pre-Camhrian but little is known of land distribution, although thick sediments accumulated, now concealed except in limited exposures. In Paleozoic time a land mass giving origin to a great mass of accumu­lating sediments lay in east Texas, and drainage was westward into the fluctuating seas of central and west Texas. Early Mesozoic was a time of continental emergence, the entire Texas region, so far The University of Texas Bulletin No. 3232 as known, being land. Drainage at this time was still westward in a part at least oí east and central Texas, and was eastward from the Ancestral Rocky Mountains and other land masses. By this drainage continental Triassic deposits were accumulated in a remnant oí the Paleozoic basin. By middle or late Mesozoic fundamental changes had occurred, the land to the east was depressed, the drain­age reversed, and a vast region inundated by the great flooding of Cretaceous time'. Cenozoic was a time of marine deposition on the fluctuating margins of the Gulf oí Mexico and oí continental deposi­tion and stream terracing inland . . Such is the framework on which the stratigraphic history of Texas is built. This history is more fully given in the chapters which follow. Fig. 2. A geologic excursion into the Delaware mountain reiion of Texas. Third Texas Field conference, 1927. Geologists of Oklahoma, New Mexico, and Texas. View at the base of Guadalupe Point. Photo by C. N. Gould. THE PRE-CAMBRIAN SYSTEMS OF TEXAS (ARCHEOZOIC AND PROTEROZOIC) The oldest rocks of Texas exposed at the surface are believed to belong to either the Archeozoic or the Proterozoic era. In most parts of the world these very ancient rocks have been greatly altered from their original condition, whatever fossils they may have con­tained having been for the most part destroyed. Only rarely do these rocks escape such alteration. For this reason it is often difficult to separate the rocks of the Archeozoic from those of the Proterozoic or from later greatly altered rocks. There is sorne probability that the oldest rocks exposed in Texas are Archeozoic. However, since their age is not definitely known, they are here discussed under the indeterminate heading of pre-Cambrian. Rocks helieved to be of pre-Cambrian age are exposed in Texas in three regions, as follows: the Llano uplift, the Van Horn region, and the Franklin Mountains near El Paso. The lithology of the rocks does not aflord sufficient hasis for correlation of the pre-Cambrian of these several regions. For this reason the use of separate forma­tion names is required for each of the areas, and no correlation within the pre-Cambrian is attempted. That sorne of the formations here referred to the pre-Cambrian may in fact he Lower Cambrian is possihle. In addition to these areas of exposed rocks, pre­Cambrian is known from well drilling over parts of the state, as descrihed in the section on underground records. While no fossils have heen found in the pre-Camhrian of Texas, except possihly sorne cryptozoans in the Van Horn region (King, 396h), there is, nevertheless, very good evidence that organisms were present at that time. In the sediments of the Llano uplift, graphite occurs widely, and in places is of sufficient quantity to he produced commercially. Graphite originates, in sorne instances at least, from carbonaceous materials by metamorphism, and its presence in the rocks may or may not he indicative of life at the time the rocks were accumulating. The iron ore of these formations, found as magnetite and hematite, may likewise be associated in origin with organic processes, although it is not impossible that these minerals have sorne other origin. The limestones which occur in the formations here referred to the pre-Cambrian may or may not be associated with organic processes. IOG IOS 104 10?> 10'1. 101 . 100 Fig. 3. lndex map showing location of some of the regions in Texas west of the 100 meridian referred to in the description of formations. 1, Franklin Mountains; la, Hueco bolson; 2, Diablo Plateau; 2a, Salt Flat; 3, Van Horn region; 4, Pecos uplift or Central Basin P.latform; 5, Amarillo uplift; 6, Soli· tario uplift; 7, Marathon uplift; 8, Red River uplift; 9, Toyah basin; 10, High Plains; 11, Osage Plains. The stippling indicates uplifts now concealed by later formations. Fig. 4. lndex map showing the location of some of the regions in Texas east of the 100 meridian referred to in the description of formations. Legend as in Fig. 3. The University of TexaSJ Bulletin No. 3232 The pre:..Cambrian formations recognized in surface exposures in the state are as follows: Llano Region Van Horn Region El Paso Region Granites Packsaddle Millican forma-Rhyolite schist tion Lanoria quartzite Valley Spring Carrizo Mountain gneiss formation LLANO REGION OR UPLIFT The Llano region in central Texas, also known as the Central Mineral region, indudes ali of Llano County and part of · Brown, Mason, McCulloch, San Saba, Lampasas, Blanco, Gillespie, and Kimble counties (fig. 4). Structurally the region is a dome on which the pre-Cambrian, which in the adjacent region is 4,000 or 5,000 feet below sea level, is more than 1,000 feet above sea level, the total doming being 5,000 or 6,000 feet. While the area of exposed Paleozoic and pre-Paleozoic is small, the area affected by the doming is large, a region of 100 miles or more in width being affected. In this great dome the Paleozoic and pre-Paleozoic forma­tions are seen, due to the removal of a Cretaceous blanket that formerly covered them. There is thus found in thís region a window of older rock coming up through the Cretaceous. The Llano. Basin.-Although structurally a dome, topographically the· area of these exposed pre-Cambrian rocks is now a basin, which may be designated as the Llano basin. This basin is the result of the erosion of the overlying formations from the crest, a rim of Paleo­zoic and Cretaceous rocks having been left. Projecting ridges of these later formations extend at places . into the basin. A prominent ridge capped by Paleozoic, projecting from near Burnet, is known as "Backbone Ridge." Similar, although usually less conspicuous, promontories of Paleozoics project into the basin elsewhere around its margins. Within the basin itself are numerous hills capped with Paleozoic rocks representing outlying remnants -of these forma­tions which formerly extended aci-oss the dome. One of the largest of these hills in the basin in Llano County is formed by Wiley and Cedar mountains. Cheney is of the opinion that the Central Mfueral region is a part of a structurally ancient feature which he has called the Concho divide, and that the exposures of the pre-Cambrian formations The Geology of Texas-Pre-Cambrian Systems 31 have resulted from the northwestward tilting of this ancient table­land (247c). The pre-Camhrian of this region, although now highly altered, originally included largely such sediments as sandstones, shales, and a limited amount of limestone. lnto these altered sedimentary rocks, igneous rocks, chiefly acidic in character, have been intruded. These intruded rocks appear now largely as granites, although sorne diorite and other basic rocks are present. Sorne of the rocks of the pre-Camhrian series are altered by metamorphism to such an extent that it is difficult to determine their origin, whether from igneous or sedimentary materials. In the main, however, the pre­Camhrian of this area represents altered sedimentary rocks. LLANO SERIES To the series of altered sedimentary rocks exposed in this uplift, Walcott in 1884 applied the term Llano group (1702). This group, or series, has since been subdivided into two formations, Valley Spring gneiss and Packsaddle schist.12 These formation names were proposed by Comstock (271), and were subsequently re-defined and applied in their present usage by Paige (1172). The rocks of this series when first described by W alcott were referred by him to the Camhrian. Subsequently, however, they were referred by Paige to the Algonkian (Proterozoic). In the ahsence of fossils, which if originally present would have heen largely obliterated by metamorphism, the conclusion that the series is of pre-Camhrian age rather than Camhrian rests on the fact that there is evidence, from angular unconformity, erosion, and intrusion of granites, of an extremely long interval of time between the deposition of these sediments and the deposition of the next over­lying Upper Camhrian sediments. On the other hand, the assumption that the formations are not as old as Archeozoic (Archean) rests merely on inference derived from the character of the sediments, which include carbonaceous shales and sorne limestones. Computa­tions of the age from the radioactive minerals, as revised by Arthur Holmes, indicate a: probable early Middle pre-Camhrian age for 12Throughout this Yolume formation1 of a group or aeriee, when Usted in the te:a:t, are amm1ed in order beginning with the oldeet íormation or member. On the other hand, in tables, meuured aectiona, and graphic sections. the oldeet formation or memher is placed at the bottom of the table or eection and the youqeat at the top, this being in accordance with established -e. The University of Texas Bulletin No. 3232 these minerals which are found Ín pegmatite veins in the granite (837a, p. 438) .13 The sediments are necessarily older than the granites, although how much older is not determined.14 The time that has elapsed since the formation of the minerals in the pegmatite dikes as deduced by Holmes from the lead ratios in the radioactive minerals is 1100 million years (837a, p. 351). VALLEY SPRING GNEISS The older of these two formations in the classification proposed by Paige is prevailingly a gneiss, which for the most part is light in color, consisting of a predominance of feldspathic and quartzitic minerals. According to Paige, the gneiss originating from sedi­mentary rocks is with difficulty separable, and in places is inseparable, from that which has been derived from the intruded granite. Quartzites are present, representing altered sandstones. The original limestones, which were present in limited amounts, are now chiefly the calcium silicate, wollastonite. More or less schist is associated with and included in the gneiss. The separation of this formation from the overlying Packsaddle schist is based in part on the more massive character of the gneiss, and in part upon its greater content of acidic materials. The gneiss, however, not pnly contains schist, but grades into the schist in such a way as to make definite separation at many localities difficult or impossible. The gneiss is exposed chiefly in the anticlines which here trend northwest. The formation is greatly intruded by granite. Stenzel, who has recently re-studied this formation, is of the opinion that the Valley Spring gneiss is igneous in origin, having been intruded into the Packsaddle schist. Under this interpretation there is but the one sedimentary formation in the pre-Cambrian of this region, the Packsaddle schist next to be described (1525c). 13In this publication references to the literature in the text and footnotes, and in the eubject index, include usually only the number assigned to the ·puhlication aa liated in the accompanying bibliography. The full citation to the publication in question may then be obtained from the bibliography. t•Publicationa listed in the accompanying bibliography relating to ·the stratigraphy, atructure, and minerals of the Llano series in elude the following: Barrell, 59; Baatin, 77; Becker, 84a; Boltwood, 138a; Buckley, 170, 173; Comotock, 271, 273, 274, 275, 276; Gentb, 574; Harrod, 671; Heoa, 710, 711; Hidden and Mackintooh, 715; Hidden, 716, 717, 718, 720; Hidden and Hillebrand. 719; Hidden and Warren, 721; H'ill, 743; Hillebrand, 828, 829; lddingo, 868; Paige, 1170, 1171, 1172, ll73; Phillipo, 1209a; Powero, 1254; Roemer, 1328, 1330, 1331; Schaller, 1367; Stenzel, 1525c; Uddeo, 164la; Walcott, 1702, 1702a; B. Willia, 176lc. The Geology of Texas-Pre-Cambrian Systems 33 Type locality: Valley Spring in Llano County; thickness unde· termined. PACKSADDLE SCHIST The Packsaddle schist includes a great, although unmeasured, thickness of metamorphosed sediments, originally consisting chiefly of shales with smaller amounts of sandstones and limestones into which were intruded acidic and sorne basic igneous rocks. The original sediments, having been metamorphosed, became schists, including mica, hornblende, amphibole, and graphite schists, accord­ing to the character of the rocks from which they were derived. The sandstones were altered to gneiss or gneissoid schists, and the limestones to marble or wollastonite. Graphite now found in the schist in considerable quantity may have been derived from the organic matter of the sediments. The schists cleave readily, the direction of cleavage being in agreement, or essentially so, with the original bedding planes. The numerous beds of limestones now changed to marble alternate with the schist and are interbedded with, or parallel to, the cleavage planes in the schist. The sandstones, now quartzitic or gneissoid, are likewise interbedded with the schists. The schists for the most part overlie the gneisses and are found in the synclines, having been removed from the crests of the anticlines except in the southeastern part of the area where exposure of the schists is general. Type locality: Packsaddle Mountain, Llano County. This forma· tion is extremely thick, measuring not less than several thousand feet. GRANITE AND OTHER IGNEOUS ROCKS The pre-Cambrian sedimentary formations have been extensively intruded by igneous rocks, the great body of these intrusives being granites. However, in addition to the granite there are smaller intrusives of more hasic rocks including diorite and gabbro. The largest masses of the basic rock intrusives are in the southeastern part of the Llano Quadrangle. Probably derived from these intrusives are the amphibolites, tale, and serpentine, which are found more particularly in the Packsaddle schist. Felsite occurs to a limited extent as dikes in the schist. Paige (1171, p. 21) expresses the opinion that the gabbro-diorite group of rocks is of earlier age than the granites. The University of TexM. Bulletin No. 3232 Granite intrudes the sedimentaries extensively, occurring as batholiths and as smaller masses, including innumerable dikes, sills, and pegmatites. So extensive are the granite masses that probably between one-third and one-half of the surface exposures within the area are of granite. The granites present considerable variation, in texture from coarse to fine, and in color from pink or red to gray. The very coarse granites are for the most part red or pink owing to the large potash feldspar crystals. Between these large crystals, and making up the remainder of the rock, is quartz, biotite, and other minerals in smaller amounts. The fine-grained granites vary from pink to gray in color and from fine to medium coarse in texture. They consist of feldspar (microcline, orthoclase, and albite~orthoclase), quartz, biotite, and hornblende. An unusual rock of local occur­rence is a quartz-feldspar porphyry. This porphyry is of later age than the granites and occurs as a dike, cut.ting both the granite and the schist. To this rock Dr. Joseph P. lddings in 1905 applied the name Ilanite ( 1209a). The trade name in com.mon use; how­ever, is opaline granite, quartz phenocrysts in the rock reflecting light in such a way as to resemble opal. STRUCTURAL CONDJTIONS Attitude o/ the Strata.-The pre-Cambrian strata in the Central Mineral region, both of the Valley Spring and the Packsaddle formations, dip for the most part at high angles. The rate of dip is determinable, not only from the cleavage planes in the schist, but also from the bands of marble, quartzite, wollastonite, and graphite schists. Measurements made at a number of localities indicate that dips of from 30 to 60 degrees prevail, although dips of both greater and lesser amounts occur. Regional Structural Features.-The major structural features of the eastern part of the Llano-Burnet region have been described by Paige (1172). In the Llario Quadrangle pronounced folds .in the pre-Cambrian rocks trend in a northwest-southea:st direction, plung­ing to the southeast. These folds aflect the pre-Cambrian only, not being reflected in the Paleozoic or later rocks. The folds had been truncated by erosion previous to déposition of the Paleozoics. In addition to folds of a northwest-southeast trend, the region is profoundly aflected by faults which, althóugh vai:ying in direction, The Geology of Texas-Pre-Cambrwn Systems 35 have prevailingly a northeast-southwest trend. These faults affect not only the pre-Camhrian but the Paleozoic as well, and will be more fully described in connection with the Paleozoic systems. The faults, together with the folds, bring about repetitions of the section, increasing the difficulty of estimating the thickness of the pre-Camhrian formations. PRE-CAMBRIAN HISTORY OF THE REGION The pre-Camhrian history of the region can in part be determined. Much of the gneisses and schists, as already indicated, is derived from a great series of sediments. That these sediments are of marine origin seems probable, as indicated by the succession of limestones, sandstones, and carbonaceous shales which they contain. Evidence from organisms, however, is wanting, fossils that may have been present having been later destroyed by metamorphism. After the deposits had become, at least in a measure, indurated, they were extensively intruded by igneous magmas. The earlier and more limited intrusions were probably basic, giving rise on cooling to gabbro, diorites, and other basic rocks. At a later time carne much larger intrusions of more acidic magmas, giving rise to the granites. Probably the latest of the intrusives is that from which the dikes of "opaline" porphyry were formed. That these granite intrusives were earlier than the overlying Paleozoic is indicated by the fact that at no place do they cut into the later rocks. Moreover, where the Cambrian rests directly upon the granite, evidence of pre-Camhrian disintegration and decay of the granite may be observed. Reworked granite likewise is found in the Camhrian sediments. The time of intrusion of the igneous rocks, therefore, is subsequent to the formation of the sedimentary series, but previous to the deposition of the overlying Cambrian. The thickness of sediments that originally accumulated was much in excess of that which now remains in this region. This is indicated by thc fact that the magmas from which the granites were formed, originally rested (as evidenced by the crystalline character of the rocks) far below the surface. The sediments themselves were sufficiently intruded to undergo re-crystallization and metamorphism. During this time, possibly in connection with the intrusion of the batholiths, pronounced folding was developed, the trend of the folds being northwest-southeast. The University of Texas Bulletin No. 3232 Following the intrusion of the igneous rocks and the folding, the region was subjected to extensive erosion. During this period of erosion the uppermost rocks were removed, the folds leveled off, and the granite exposed. Upon these exposed granites and truncated folds the Cambrian sediments were deposited. Since the overlying sediments are of Upper Cambrian age, it is possible that this interval of erosion may have been largely or entirely within Cam­brian time. The history of the region up to the time of the Upper Cambrian, including deposition of sediments, extensive intrusions of igneous rocks, folding and profound erosion, is obviously one of long duration marked by complexity of events. The igneous rock, now exposed at the surface, shows by its coarsely crystalline char­acter that for the most part it is from igneous intrusions once deeply buried under sediments which have since been removed by erosion. This period of great erosion, as well as the diastrophic activity which folded and altered the rocks, took place previous to the deposition of the overlying Upper Cambrian. TYPICAL EXPOSURES The locality visited by W alcott, by whom the name of the _series was proposed, is on the west side of Packsaddle Mountain about 14 miles southeast of Llano. At this locality on Honey Creek are fine exposures of the Packsaddle schist. These deposits when first examined by Walcott were described by him as exhibiting at Pack­saddle Mountain but little evidence of metamorphism, and were then referred to the Cambrian ( 1702, p. 431) . By following the public road from Honey Creek south and south­east out of the basin, severa! miles of Packsaddle schist are traversed, in which exposures are frequent and in which the dip in the strata varíes in direction from southwest to southeast, and in steepness of dip from 30° to 80°. Although, owing to faulting and folding, the actual thickness of sediments crossed in this section cannot be determined, the exposures afford a conception of the evidently gr.eat thickness of the schist series. This road crosses an anticline in the pre-Cambrian which trends northwest-southeast and plunges to the 'southeast. The Valley Spring gneiss may be seen a few miles west or southwest of Llano, where it is greatly intruded by granite, or at The Geology of Texas-Pre-Cambrian Systems 37 the type locality about 12 miles northwest of Llano. The very coarse-grained granites are typically developed in the southwestern part of the Llano Quadrangle 15 or 18 miles southwest of Llano. The fine-grained granites which are widely distributed, are extensively quarried near Llano. The porphyry {llanite) is exposed on the Llano-San Saba puhlic road 10 miles north of Llano, at which place the road crosses a dike of this rock. The Camhrian-pre-Camhrian contact may be well seen on Peder­nales River ahout one mile upstream from McDougall Crossing in Blanco County, and in Burnet County near the puhlic road ahout one mile east of Kingsland; also near the lead prospects on Beaver and Spring creeks, Burnet County. VAN HORN REGION The term Van Horn region is here used to apply to a somewhat indefinitely defined area in the vicinity of Van Horn including parts of Culherson, Hudspeth, and Jeff Davis counties. This region is southeast of the Diablo Platean and may he regarded a5 the somewhat hroken southeastern extension of this platean. In the Van Horn region are included pre-Camhrian exposures in the Van Horn, Wylie, and Eagle mountains to the southeast, south, and southwest of Van Horn, and at the south margin of the Diablo Platean west to near Finlay {region No. 3 of fig. 3, p. 28). Structurally the Van· Horn region is a dome representing the maximum uplift found in Trans-Pecos Texas. The structural condi­ tions in this dome are complicated. The pre-Camhrian rocks were subjected to mountain-making movements in pre-Camhrian time, and doubtless were affected by the late Paleozoic mountain-making disturhances. Again in relatively recent geologic time, prohably within the Cenozoic, this region was highly faulted and now includes a great series of tilted hlocks. These hlocks are at the margin of the great holson or graben known as Salt Flat, which extends in a north­ south direction for more than a hundred miles. At the east side of this holson are the Guadalupe and Delaware mountains, while at the west are the Diablo Platean and the fault hlocks of the Van Horn region including Baylor, Beach, and Carrizo mountains. The pre-Camhrian of the Van Horn region includes two forma­ tions or series, the Carrizo of Streeruwitz and the Millican, hoth of The University of Texas Bulletin No. 3232 which represent almost entirely sedimentary rocks. That the Milli· can formation is probably of pre-Cambrian age was first suggested by Dumble (491). The reference of the series to the pre-Cambrian is based on the degree of alteration of the rocks, their structural complexity, unconformity with the overlying formations, and other evidence of a long erosion interval between these formations and the next later rocks of the region which are probably of Upper Cambrian age. 15 CARRIZO MOUNTAIN FORMATION The term Carrizo has been applied to two Texas formations. Car­rizo sandstone was used in a formational sense in the First Report of Progress of the Texas Geological Survey ( 454, p. 70), applying to an Eocene sandstone exposed in Dimmit County, Texas. Subse­quently, in the Second Annual Report of the Texas Geological Sur­vey ( 458, p. 783) , Streeruwitz applied the name Carrizo to an en­tirely different formation, namely, the pre-Cambrian schists of the Carrizo Mountains. The term Carrizo was used by Streeruwitz in 1889, although apparently not in a formational sense. At a later date Richardson (1314, p. 3) defined more fully the Carrizo forma­tion of the Van Horn region. In conformity with usage adopted by the United States Geological Survey for the state map, and to obviate this conflict in names, the term Carrizo Mountain formation is here used for the schists in the Carrizo Mountains, The rocks involved are varied in character and it is probable that when described in detail they will be regarded as constituting a series rather than a single formation. The Carrizo Mountain formation consists of quartzites, schists, slates, and some igneous intrusives. The rocks are for the most part of fine textlire. The quartzites break with conchoidal fracture and are not foliated. The schists, on the other hand, are foliated and cleave readily. They include mica, quartz-mica, amphibolite, chlorite, epidote, hornblende, and quartz schists. Pegmatite, graphic granite dikes, and quartz veins are present. The slates which are interbedded with the quartzites are of fine texture. These varieties of rocks occur successively in the formation, resulting in alternating :lSPublicatiom relating to the pre-Cambrian of the Van Hom region liated in the accompanying bibliography includo tbo following: Baker, 46; Dumble, 454, 458, 459, 491; OllllllD, 1161; Ricbard­oon, 1304, 1305, 1310, 1314; Streeruwitz, 1559, 1560, 1561, 1564, 1566. Tke Geology of Texas-Pre-Cambrian Systems 39 bands. The color of the sediments on fresh exposure is prevailingly gray, although varying to dark or black. Sorne dark chloritic schists in the formation, according to Richardson (1314), are probably de· rived from sills of basic igneous rocks. The Carrizo Mountain formation is exposed in the Carrizo Moun­tains southwest of Van Horn and in the Van Horn Mountains west of Lobo and south of the Southern Pacific Railroad. An exposure of the Carrizo Mountain formation in the northeast front scarp of Eagle Mountains is described by Baker ( 46, p. 7). The rocks here include quartzites, quartz schists, cherts, and dark intrusives. There are also exposures of this formation at the west margin of Wylie Mountains, at Bass Canyon, and north of Eagle Flat section house, between Allamoore and Sierra Blanca. The rocks consist of a great variety of schists, including pegmatite, granite, and quartz dikes. Type locality: Carrizo Mountains, Culberson County; thickness undetermined. MILLICAN FORHATION The Millican formation, named by Richardson in 1914 (1314, p. 4), consists of sandstone, conglomerate, and limestone. The sand­stone is prevailingly red and consists of very fine sand stained by iron oxide. In contrast to the smallness of the grain of the sand­stone, the conglomerate is coarse and includes pieces of limestone, sandstone, igneous and other rocks, varying from very small to a foot or more in diameter, usually well cemented in a very mixed matrix of small rock fragments. The conglomerate, according to Richardson, does not occur at a single stratig.raphic level but is at various levels in the formation. The limestone, as well as the con­glomerate, makes up a subordinate amount of the formation as com­pared to the sandstone. The limestone is gray and somewhat cherty. Locally, it has been altered to a white marble. Streeruwitz named the sandstone of this formation "Diablo," and Dumble proposed for it the name "Hazel" (1314). The largest body of conglomerate is near the base of the formation and approximates 1,000 feet in thickness. The Millican formation is exposed north of the Texas and Pacific Railroad and at the southeast side of the Diablo scarp, passing under the Diablo Plateau. Exposures occur in dis­connected areas from northwest of Eagle Flat to Allamoore and The University of Texas Bulletin No. 3232 thence at the base of the escarpment for sorne miles northeastward. The area of exposure of the Millican does not overlap that of the Carrizo Mountain. The base of neither formation is exposed and both are in angular unconformity with the overlying Paleozoic. The Millican, however, is not so completely metamorphosed as is the Carrizo Mountain, and for that reason is regarded as probably later in age. King has observed also that sorne fragments of the Carrizo schists are included in the Millican formation ( 396b) . In most places the two series are separated by severa! miles of Paleozoic or late Cenozoic deposits. King reports, however, that just north of Eagle Flat section house the two series have been brought into contact by thrust faulting, the Carrizo being here thrust over the Millican, the fault plane dipping south. Type locality: Millican Ranch, 10 miles northwest of Van Horn; thickness exposed, 2000-3000 feet. IGNEOUS ROCKS lgneous rocks are but little developed in the Van Horn region. In the Carrizo Mountain formation, as already mentioned, are sorne bands of chlorite schist which may be derived from basic igneous sills. Both the Carrizo Mountain and Millican formations are cut by massive diabase dikes and sills. The sills which give rise to the chlorite schist indicate by the extent to which they are metamorphosed that they were intruded in pre-Cambrian time. The diabase dikes, however, are said by Rich­ardson to be of later origin. With these dikes are associated the silver and copper of the Millican formation. STRUCTURAL CONDITIONS Attitude of Strata.-In the Carrizo Mountains the quartzite, schist and slate bands of the Carrizo Mountain formation representing the original strata, dip to the southeast, the amount of dip varying from 25º to 60°. North of the Texas and Pacific Railroad, in the area of exposure of the Millican formation, the strike is prevailingly east-west. However, in the northwestern part of the area of ex­posure of the Millican formation the strike is northwest-southeast with southwest dip. The dips are determined in the Millican forma­tion chiefly by the position of the limestones and conglomerates, the bedding in the sandstone being obscure. In addition to this The Geology of Texas-Pre-Cambrian Systems 41 prevailing trend in the Millican fonnation, there are minor folds which affect direction of dip. Near the thrust fault contact of the two series, the rocks of the Millican formation are sharply folded and overturned to the north. Farther to the north away from this contact they flatten and the formation near Sierra Diablo is only gently tilted. The pre-Cambrian of the Eagle Mountains, according to Baker (46), strikes N. 70° E. and dips steeply S.SE., while that of the Wylie Mountains dips 20° to 30° south. The schists of the Van Horn Mountains dip on the average eastward to southward. Over­thrusting of the Carrizo onto the Millican has been described above. Regional Structura/, Features.-The Van Horn area is a region of extreme faulting. A late fault system of this region has a north­northwest trend. The salt basin is itself a result of faulting and folding. In addition to the north-south faults are others diverging from this trend, being in places at right angles to it. The result of these main and cross faults is the formation of blocks at the mar­gins of the valley and occasionally within the valley itself. The Carrizo Mountains are a block set off on all sides by faulting or folding. A down block at the north of the exposures of the Carrizo Mountain fonnation, separating this area from that of the Millican formation, brings the Paleozoic, and locally even the Cretaceous, in contact with pre-Cambrian. The exposed areas of the Carrizo Moun­tain formation occupy, therefore, up-faulted blocks. The exposure of the Millican formation, north of the Carrizo Mountains, is affected by faulting, although in a less pronounced degree. Just off the margins of the Diablo Plateau east of the Millican exposures are partly foundered blocks in the valley, such as Baylor and Beach mountains. These blocks, however, expose Pale­ozoic only, the pre-Cambrian, which underlies the Paleozoics, heing submerged. The regional structural features, therefore, affecting formations to as late as the Cretaceous, include block faulting ad­j acent to a graben. PRE-CAMBRIAN HJSTORY OF THE REGION As already indicated, the Carrizo Mountain and Millican forma­tions contain sedi.ments including sandstones, silt-stones, shales, con­glomerates, and li.mestones. The alteration processes by which these The University of Texasi Bulletin No. 3232 sediments were changed to quartzites, schists, slate, and marble, op· erated previous to the deposition of the next latest formations of this region, which are probably Upper Cambrian. To this period also belong the conditions of pressure and stress which resulted in a development of schistosity and slaty cleavage involving the regroup· ing of the minerals; and the time of folding which in the main pro­duced the high dips of the Carrizo Mountain and the Millican forma­tions. The rate of dip may have been to sorne extent altered, either increased or decreased, by the extensive block faulting in relatively late geologic time. That the folding was initiated and chiefly devel· oped previous to deposition of the overlying formations is indi­cated by the pronounced angular unconformity, as well as by the much greater complexity of the pre-Cambrian structural features as compared to those of the later formations. As elsewhere stated, the metamorphism is more pronounced in the Carrizo Mountain forma· tion than in the Millican formation, and to that extent the inference of pre-Cambrian age for the Carrizo Mountain is stronger than for the Millican. The long period of erosion indicated by the unconformity at the top of this series may be partly or entirely within the Camhrian, the next overlying formations heing prohably of late Camhrian age. TYPICAL EXPOSURES Typical exposures of the Carrizo Mountain formation may be seen generally throughout the Carrizo Mountains south of the Texas and Pacific Railway. The Texas and Pacific Railway from Van Horn west approximately follows a fault at the north side of the moun­tains and in places passes over exposures of the Carrizo Mountain formation. The new public road, south of the railroad, affords good exposures of the Carrizo Mountain formation. The Millican forma­tion is well exposed and may be readily seen at and near the Hazel and other silver-copper mines 10 to 20 miles northwest of Van Horn, and also at many localities north and northeast of Allamoore. The erosiona! features of the Millican formation are dístinctive. The sandstones, or silt-stone, disintegrate rapidly and forro small hills. The surface in the exposed area of this formation can scarcely be said to have a soil, and supports no more than a meager growth of vegetation. Tke Geology of Texas-Pre-Cambrian Systems 43 EL PASO REGION The Franklin Mountains extend from El Paso slightly west of north into New Mexico, where they connect with the Organ and San Andres ranges. Structurally the mountains are a great fault block which dips westward, its east margin being a fault scarp. Imme­diately east of the mountains is a partially filled bolson or graben. Beyond the valley eastward are the Hueco Mountains, which consti­tute the west-facing escarpment of the Diablo Plateau (fig. 3, p. 28). The pre-Cambrian of the Franklin Mountains includes altered sedi­mentary rocks, the Lanoria quartzite, and, overlying this formation, rhyolitic igneous rock. The exposures of these formations are found in the east-facing scarp. The same formations may be under the scarp at the east side of the valley, but if so are but little exposed. However, King (396b) has recently described red granite exposures at the south end of the Hueco Mountains regarded by him as pre­Cambrian in age. Sorne of these exposures are noted by Richardson (1304, p. 57), who regarded them as dikes. The exposures are found south and !routheast of the entrance to Padre Mine Canyon.16 LANORIA FORMATION The Lanoria formation consists very largely of quartzite with smaller amounts of slaty rock and with sorne intruded diabase. The quartzite is of fine texture, the quartz grains being embedded in a matrix of silica, sericite, and kaolin. It is hard and is cut by thin sills and dikes of diabase. The contact of the formation with the Cambrian is not seen, as the two formations are separated by rhyo• litic igneous rock. The dip of the two series, however, is essentially the same in direction and amount ( 1312) . No fossils have been found, and the formation is referred to the pre-Cambrian because of its position under the Upper Cambrian, this position being com­parable to that of the other pre-Cambrian formations previously descrihed. Type locality: Lanoria settlement, El Paso County; thickness, 1,800 feet exposed, full thickness unknown. The formation was named by Richardson ( 1312) . Up¡¡¡,licationa liated in the accompany_ing bibliography relating to the pre·Cambrian oí the El Paso region include the followiug: Richardson, 1304, 1305, 1307, 1308, 1309, 1310, 1311, 1312, 1313. The University of Texas< Bulletin No. 3232 IGNEOUS ROCKS The pre-Cambrian igneous rocks of the Franklin Mountains, aside from diabase sills and dikes, consist of rhyolite porphyry and associated pyroclastic rock. The porphyry is a massive red rock consisting of a fine textured ground-mass in which are phenocrysts of quartz and feldspar. Although prevailingly red, the rock varíes to a black ground-mass, in which case the phenocrysts are largely of feldspar. The thickness of the rhyolite is 1500 feet (1312). . At the base of the igneous rocks is an agglomerate of rhyolite, including pieces of rock from the underlying quartzite, indicating an erosiona! unconformity between the igneous rock and the Lanoria formation. While this agglomerate is not present everywhere, in places it attains a thickness of as much as 400 feet. The overlying formation, the Bliss sandstone, contains inclusions from the rhyo­lite, indicating that there is also an erosiona! unconformity between the rhyolite and the Cambrian·. According to N. H. Darton, sorne of the granite of the Franklin Mountains, mapped as prn;¡t-Paleozoic, is unconformable below the Bliss sandstone, and is of pre-Cambrian age. Other rhyolitic rocks extensively exposed in the Franklin Mountains were intruded subsequent to the Cambrian. Granite, as previously stated, is reported .at the south end of the Hueco Mountains. STRUCTURAL CONDITIONS Attitude of Strata.-The Lanoria quartzite in the Franklin Moun­tains dips westward at about the same angle as the Paleozoic rocks, that is, between 20° and 45°. The formation has been little affected by folding, although the rocks are altered from sandstone to quartzite. Regional Structural Features.-The regional structural features affecting these formations are those of the Franklin Mountains as a ' whole. The mountain, as already stated, is a great fault block steeply tilted westward and forming a pronounced east-facing scarp. As in the Van Horn region the main trend of the faulting is north­south. In addition, however, there are faults which are transverse or oblique to the main line of faulting, by which the mountain mass is cut into blocks of lesser displacement. The age of this great fault system is relatively late in geologic time, and the faults cut ali of the formations of the mountains. The Geology of Texas-Pre-Cambrian Systems 45 PRE-CAMBRIAN HISTORY OF THE REGION The pre-Cambrian history of this region includes several recog­nizable periods. The first is that during which the Lanoria sedi­ments accumulated. At a later time these sediments were intruded by sills and dikes of igneous rock and were uplifted and eroded. Following this period of erosion there occurred lava flows, which now make up the rhyolite. At the base of the lava is an agglom­erate, which in places reaches a thickness of 400 feet. The top of the lava in turn was eroded previous to the invasion of the sea and deposition of Cambrian sediments. TYPICAL EXPOSURES The Lanoria quartzite and overlying rhyolite are exposed in small areas on the eastern slope of the scarp of the Franklin Mountains. The rhyolite forms the summit and sides of the highest peaks in the mountains. The quartzite, on the other hand, may underlie the Diablo Plateau, representing an extension of the pre-Cambrian of the Van Horn region under somewhat changed lithologic conditions. UNDERGROUND POSITION OF THE PRE-CAMBRIAN IN TEXAS The pre-Cambrian is known not only by surface exposures but also, ata number of places, by well cores and cuttings. Wells have been drilled to the pre-Cambrian in counties adjoining or near the Llano uplift, on the Red River uplift, on the Pecos uplift, in the Amarillo region, and on the Diablo Plateau.17 LLANO UPLIFT AND ADJACENT REGION East of the Llano uplift in the old Luling oil field in Caldwell County, wells have reached schists ata depth slightly less than 5,000 feet. In this oil field three wells have been drilled through the Cre­taceous and into the underlying rocks. These wells entered schists at depths in feet as follows: Taber farm, 4,796; Tiller farm, 4,807; Kelly farm, 4, 728. On the Tiller farm these schists were drilled into to depth 7,504 feet, and on the Kelly farm to 7,859 feet. The rock of the Taber well is a calcite quartz-sericite schist with pink il7Publicationa relating directly or indirectly to the underground poaition of the pre-Cambrian in Teu.1 liated. in the bibliography include the following: Bauer, 78, 79¡ Hager, 64Ia¡ Harrison, 670; Powen, 1254; Pratt, 1264; Sellards, 1423, 1424. The University of Texas¡ Bulletin No. 3232 bands due to garnets. The two most abundant minerals are quartz and sericite, which make up about 75 per cent of the rock, sericite predominating. Other minerals are calcite or dolomite, garnet, tremolite or actinolite, and apatite. Essentially similar rock is found in the other two wells. In the Kelly well chlorite schists are found at depth 7,240 feet. In the Tiller well seams, apparently of kaolinite, occur in schists at a depth of 7,169 feet, and a graphitic schist is found at depth 7,483 feet. The schist drilled into in these wells is closely similar to that of the Llano uplift. Additional in­formation on these rocks in Caldwell County is given on page 132. To the west and south of the Llano region, knowledge of the posi­tion of the pre-Cainbrian has been somewhat extended by well records in Gillespie and Mason counties. In Gillespie County three wells drilled through the Cretaceous all entered granite at moderate depth, the deepest being at 1,182 feet. This granite is evidently a south­ward extension of the granites of the Llano uplift exposed in north­ern Gillespie County. In northwestern Mason County a well has beeil drilled into the pre-Cambrian at depth of 1,490 feet or less. The rock as indicated by the cuttings is a schist not unlike that exposed in eastern Mason County. In McCulloch County, northwest of the Llano uplift, two wells have been drilled into the pre-Cambrian. One of these, in the western part of the county, reached schists at depth 2,982 feet. The rock at this locality is a hornblende schist. In the northern part of this county the pre-Cambrian is reached at depth 3,309 feet and is here a granite. Directly north of the Llano uplift in San Saba County granite was encountered at depth 1,655 feet. In Lampasas County three wells ha ve entered· granite. From a well on the Wittenberg farm in the western part of the county samples of pink granite were obtained from depth 3,580 feet to 4,180 feet. In Taylor County one well has been drilled into pre-Cambri~m sediments reached at a. depth of 5,809 feet. In Eastland County a well located north of Cisco · entered, at depth 5,425 feet, conglomeratic material from granites or gneiss, and possibly terminated in pre-Cambrian bedrock at depth 5,591 feet. These records may all be regarded as extending the known posi­ tion of the pre-Cambrian of the Llano uplift. By interpolating the known thickness of the older Paleozoic formations the depth to this The Geology of Texas-Pre-Cambrian Systems 4 7 facies of the pre-Camhrian may reasonably be indicated somewhat farther, particularly westward and northward, as has been done on the accompanying map ( fig. 5). O K LA H O l'I 11 o "lO 60 Em Pll<.AI<" ""'" u~u Q Mtl~•l"":' \IKOU!U#l.Y"'°'LUl'l.OIC: C9 Plll-<..t.MUWI 0M0U UTL P..U.O'LOIC. CID PQC~~ ·;iu tll"l~I c:J OV'Ol"tOP•!-~141<\llU)lTU-l:I \OS 'º 95 Fig. 5. MAp of Texas and parts of adjoining states showing surface ex­posures and underground position of the pre-Cambrian. RED RIVER UPLIFT The Red River uplift, or series of uplifts, consists of buried moun­tains which affect the structural conditions adjacent to the Red River in north Texas through severa} counties from Denton and Cooke on the east to Wichita, Wilbarger, and Foard on the west. The uplift has been discovered by drilling, the formations involved being not now exposed. The uplift was first described by Hager in 1919 (64la) and at that time was known to affect Cooke, Mon­tague, Clay, and Wichita counties. Subsequent drilling has shown The University of Texas, Bulletin No. 3232 that it extends southeastward into Denton County and that this, or a similar uplifted area, extends westward through Wilbarger and Foard counties. Whether or not it reaches farther to the west or northwest is not known. The Red River uplift is defined as the uplift, or series of uplifts, extending through severa} counties adja­cent to the Red River in Texas and having an approximately east­west trend (fig. 5, p. 47, and region No. 8 of fig. 4, p. 29). In these severa} counties adjacent to the Red River, from Denton and Cooke on the east to Wilbarger and Foard on the west, igneous rocks and schists of the Llano facies have been reached in drilling. The depth varies as does also the character of the rock. At places . within this region the pre-Cambrian is within 2,000 feet or less of the surface and elsewhere is reached at a depth in excess of 4,200 feet. In Den ton County gneiss was identified in a well on the W aide farm at dept 1,882 feet. This rock, as determined by J. T. Lonsdale, con­tains quartz, feldspar, and biotite, with apatite, epidote, titanite, and other minerals. On the Yeatts farm, Denton County, a sample of dark schist was obtained at depth 2,013 feet. In Cooke County, on the Whaley farm, ~ark green schists were reached at depth 2,312 feet. On the Yosten farm near Muenster at depth 2,750 feet are similar schists, which, according to Lonsdale, contain as predominating minerals quartz, hornblende, and biotite. In Montague County granitic rocks are recorded in two or more wells, and schists in one. The granite of the Lemon well in Montague County at depth 2,707 feet to 2,913 feet as described by T. L. Bailey, is variable, consisting of pink and red granite and greenish-black diabase. In Clay County granite was reached in Byers 41 of The Texas Company at depth 4,240 feet. In Foard County on Mathews' land schists were reached at depth 2,215 feet. A similar schist is reported to have been reached in another well on the same farm at depth 2,465 feet. From the Miller well an arkosic material including igneous pieces was ob­tained at depth 4,950 feet. In Wichita County a well of the Mag­nolia Petroleum Company on the Beech lease reached altered rock at 3,000 feet. On the Schakenberg farm a well reached igneous or metamorphic rocks at 3,575 feet. In Wilbarger County on the Stephens ranch ignéous rock, identified by F. C. Sealey as diorite, was obtained at 3,007 feet. From the log it appears that similar The Geology of Texas-Pre-Cambrian Systems 49 rock was reached at depth 2,970 feet. On the Zipperle farro in this county gneiss was found at depth 2,881 feet. History of the Red River U plift.-Although the Red River uplift is a buried structural feature and can be studied only through well records and samples, not a little of its history may be determined or inferred. The pre-Cambrian rocks are similar to those of the Llano uplift. In both regions the original shales and sandstones were altered to schists and quartzites; both were extensively intruded by igneous rocks, largely acidic, which formed chiefly granites; both regions were intensely eroded in late pre-Cambrian or early Cam­brian time. The Upper Camhrian and Lower Ordovician seas crossed at least the eastern part of the Red River uplift. Farther to the west less is known of the early Paleozoic sediments, which are wanting, either through non-deposition or owing to subsequent ero­sion. The presence of the Bend series over at least a part of the Red River uplift indicates partial, if not complete, suhmergence during early Pennsylvanian time. The Marble Falls limestone of the Bend series rests disconformably on the older rock. The upper Pennsylvanian, in turn, rests with an angular unconformity on the Marhle Falls formation. The period of intense dynamic activity, which metamorphosed the pre-Cambrian sediments and intruded the granites in hoth regions, antedates the deposition of the overlying Paleozoic, which is unaltered. The uplift, however, differs from the Llano uplift in that instead of a single great doming it consists of a series of ridges with en échelon arrangement. The principal orogenic movement creating this uplift is believed to be of mid-Pennsylvanian age, thus agreeing in time with an uplift in the Llano region. AMARILLO UPLIFT The Amarillo uplift as now known extends from Wheeler County, near the Oklahoma-Texas line, westward or slightly north of west, 100 or more miles. Aside from this main anticline are partially isolated domes in Potter, Oldham, and perhaps other counties. This uplift, particularly in its western part, is reflected in the Permian formations at the surface, and drilling for oil and gas was orginially begun on domes on this uplift. As developments progressed, drill­ing revealed the presence of igneous rocks underneath the oil and The University of Texas, Bulletin No. 3282 gas producing sedimentaries. Frequently also wells have entered or passed through arkosic rocks which prohahly are not greatly re· moved from their original source. In these wells not a little diffi­culty has heen experienced in differentiating hetween granite con­glomerate as found in well cuttings and original granite or other igneous rocks ( 670, 1264) . The well records now available reveal an uplift by which pre­Cambrian rocks were hrought near enough to the surface to he within reach of the drill in severa! counties. This great uplift ex· tends across the Panhandle from Oklahoma into New Mexico. The uplift as a whole is prohahly a platform of irregular surface from which peaks project. The arkosic materials have accumulated at the sides of such peaks and may in sorne instances he very local (78, p. 739). The counties, for which records of igneous rock, either in place or as arkosic material are availahle, are Carson, Col­lingsworth, Gray, Hartley, Hutchinson, Oldham, Potter, and Wheeler. These counties form a helt extending entirely across the Panhandle. Doubtless additional similar rock will he found in other counties adjoining these (fig. 5, p. 47, and region No. 5 of fig. 3, p. 28). Several wells in Carson County have entered igneous rock. A well on the McConnell ranch encountered either diorite or diahase containing plagioclase, augite, biotite, and magnetite or ilmenite. Samples of this rock were obtained from depths 2,685 feet,18 2,966 feet, 3,005 feet, and 3,050 feet.19 The rock at 3,060 to 3,084 feet is identified by Bailey as diahase and is regarded by him as coming from a dike. Granite wash is reported from severa! other wells in the county at depth 2, 700 to 3,094 feet. In Gray County a well 7 miles west of Pampa reached igneous rock at depth 2,985 feet. The abundant minerals, as determined by T. L. Bailey, are lahradorite and hornhlende with sorne magnetite, the rock heing classed as a gabbro or gabbro-diahase. On the Beavers ranch in this county fresh granite is reported at depth 3,305 feet, ahove which for 500 or 600 feet is granitic reworked material interhedded with shales. In Hutchinson County a well on the McGee ranch is re­ported in the driller's log to have entered granitic material at depth 3,135 feet. No samples have heen seen from the well. Granite 18Determination by C. S . Roes, 1924. Letter to Sidney Powere. 11'Examined by T. L. Bailey and C. S. Ross. The Geology of Texas-Pre-Cambrian Systems 51 wash is reported in several wells in Oldham County at depth 2,380 to 2,590 feet, and solid granite may have heen reached in sorne of the wells. The Landegrin well in this county was drilled to 5,015 feet without reaching granite wash or pre-Cambrian rock. In Potter County a well drilled by the Emerald Oil Company on the Master­son ranch 20 miles north of Amarillo entered gneiss at depth 2,000 feet and terminated in similar rock at 2,148 feet. Several other wells in the county, after drilling arkosic rock at greater depth, passed through limestones and shales. The log of a well on the George ranch in Wheeler County indicates granitic material, probably con­glomerate or arkose, at 2,408 feet and diabase at 2,492 feet. Sam­ples from within the upper interval are seemingly unaltered diabase and granite. Of the rock in the lower interval no samples are at hand. On the Kockelhofler ranch granitic material is found at depth 2,155 to 2,393 feet. From a well on the Wetzel ranch samples were received from depth 2,248 feet which contained fresh appear­ ing orthocla~, quartz magnetite, and zircon. Additional records on this uplift are given in the table of wells. The age of the oldest rock of this uplift can be determined only by inference and analogy. As already stated, the uplift is believed to be connected with, and a part of, the Wichita Mountains of Okla­homa. In the eastern mountains of the Wichita chain, Upper Cam­brian and Lower and Middle Ordovician are found exposed and rest­ing unconformahly on the older series.20 Well drilling has demon­strated that the Pennsylvanian is present around these mountains although not exposed.21 In the belief that the Amarillo uplift is the westward extension of the Wichitas, the rocks at the core of the uplift are referred to the pre-Cambrian. History of the pre-Cambrian of the Amarillo Region.-Assuming a connection between the Amarillo uplift and the Wichita Moun­tains, the history of the pre-Cambrian of the two regions may be inferred to be essentially the same. During Upper Cambrian and Lower and Middle Ordovician, the Wichitas proper were covered in part or completely by a shallow foreland sea. The westward limit 9>Taff., ]. A., Preliminary report on the geology of the Arbuckle and Wicbita mountaios of Indian Territory aud Oldahoma, U. S. Geol. Surv., Prof. Paper 31, 1904. 11Howell, J. V . ., Notes on the Pre-Permian Paleozoica of the Wichita Mountain Area, Bull. Amer. Aaoc. Petrl. Geol., Vol. 6, pp. 41H2S, 1922. The University of Texas Bulletin No. 3232 of this sea is unknown, and it has not been determined whether or not it covered the Panhandle region. If the Panhandle region was under sea at this time, the sedimerits have been removed from at least the higher peaks where Permian or Pennsylvanian now rests on pre-Cambrian. The Pennsylvanian sea, in which sediments were deposited around the Wichitas, extended westward into the Pan· handle, as is indicated by the presence of Pennsylvanian at the side of the uplift. The Wichita-Amarillo uplift thus presents a close analogy to the Red River uplift with which it is doubtless closely connected. An early uplift of the Wichitas occurred, according to Tomlinson (1606b), not later than the end of Springer, Lower Penn­sylvanian, anda renewed uplift followed the Hoxbar (Canyon). That the Amarillo Mountains and the Red River uplift were made at the same time as the Wichitas, or at approximately the same time, may reasonably be inferred. PECOS UPLIFT OR CENTRAL BASIN PLATFORM The Pecos uplift is a buried structural feature affecting forma­tions up to and including the Permian. To sorne extent it may like­wise have affected Triassic and Cretaceous formations, but in th.e lat­ter the effect, if any, was relatively slight, and the attitude of the surface formations gave no reason to anticipate such an underlying structural feature as drilling disclosed. The Pecos uplift as now known extends from southeastern Pecos County in a northwesterly direction into New Mexico. The uplift has a breadth, as measured in Permian rock, of 30 or 35 miles. On the uplift are superim­posed structural features in the Permian, several of which are pro­ducing oil. Metamorphic or igneous rocks are known at the present time in one well only, the Shell Company well on The University of Texas lands in Pecos County. · In this well igneous or metamorphic rock was reached at depth 4,750 feet. In samples of this series from depth 4,931 to 4,935 feet, Lonsdale has identified the following as abundant minerals: quartz, microcline, albite, hornblende, and bio­tite; and, in smaller amounts, magnetite, zircon, apatite, and calcite. Much the same minerals, varying in relative amounts, are present in samples at depths 5,001 to 5,004 feet and 5,124 to 5,128 feet. The rock as a whole is granitic and without evidence of meta­morphism. The age of this rock is as yet in doubt. From analogy The Geology of Texas-Pre-Cambrian Systems 53 with the Van Horn region to the west and the Llano region to the east, it is regarded as probably pre-Cambrian. This uplift is known also (190,201) as the Central Basin l>latform (fig. 5, p. 47, and region No. 4 of fig. 3, p. 28). DIABLO PLATEAU The Diablo Plateau is an uplifted large block lying chiefly in Hudspeth County. The block sags in its central area and is struc­turally higher at its west, east, and southeast margins. At its west­ern margin are the Hueco Mountains bordering the Hueco Bolson. These mountains, according to Baker (MS.), are an asymmetrical anticline, the west flank of which dips very abruptly under the Hueco Bolson. At its east margin is the escarpment of Sierra Diablo border­ing Salt Flat. The Finlay dome forms its southwest margin, and at the southeast is the Van Horn dome, now broken into blocks by faulting and deeply dissected by erosion. The Hueco Bolson at the west and the Salt Flat on the east are structural valleys. Fault scarps and abrupt dips separate the sunken valleys from the uplifted blocks. A well on the Diablo Plateau on land of The University of Texas drilled by the California Oil Company reached altered rock at depth 4,725 feet (fig. 5, p. 47, and region No. 2 of fig. 3, p. 28). ECONOMIC PRODUCTS OF THE PRE-CAMBRIAN IN TEXAS A highly diversified series of minerals is found in the pre­Cambrian of the Llano region. The mineral products obtained commercially from the Llano series of rocks include granite of severa! varieties, graphite, lead, manganese, and rare earth minerals. Prospecting has been done for severa! other minerals of which, however, commercial production has not been obtained. Among these are gold, silver, iron, copper, molybdenite, flourite, zinc, marble, asbestos, serpentine, barite, tale, topaz, and wollastonite ( 1171) . The rare earth minerals were mined for man y years at Barringer Hill in Burnet County where a large number of these minerals are found in a large pegmatite dike (711). The Millican formation of the Van Horn region contains silver and copper minerals, the ore being found in mineralized zones and adjacent to dikes. Severa! mines in this region have been operated The University of TexM Bulletin No. 3232 mtermittently for many years. Of these, the Hazel Mine northwest of Van Horn has been most extensively worked. Various rock products were formerly made from the minerals of a pegmatite dike in the Carrizo Mountain formation of the Van Horn Mountains, and were marketed under the name of "micolithic" products. Sorne copper prospects are reported by Baker from the Carrizo Mountain schists (46). Turquoise occurs in the Carrizo Mountain in thin seams along joint planes. The marble of the Millican formation has not been utilized. An outcrop of an iron oxide ore is reported by Streeruwitz (1561) . Fig. 6. Faulting in early Paleozoic formations, on James River, fourteen miles southwest of Mason, Texas. THE PALEOZOIC SYSTEMS In contrast to the limited exposures of pre-Cambrian, the Paleo· zoic rocks are extensively exposed in Texas. All of the systems of the Paleozoic are represented, the most widely exposed formations being those of Pennsylvanian and Permian. CAMBRIAN SYSTEM Absence of Lower and Middle Cambrian Neither in sudace exposures nor in deep wells has Lower or Middle Camhrian been recognized in Texas. Explorations by drill­ing are necessarily incomplete, and the observations thus far made may subsequently be modified. It is known, however, that between the pre-Cambrian and the next overlying Paleozoic there is an unconformity of wide extent representing a long interval of time during which the land was being eroded. In Lower Cambrian the sea on the North American continent occupied, so far as known, only the two major troughs or geosynclines, the Cordilleran geosyncline in the western margin of the continent and the Appa· lachian geosyncline in the eastern part. In Middle Cambrian time a somewhat similar condition persisted and, as now interpreted, no Middle Cambrian deposits are recognized in the Texas-Oklahoma­Missouri region. In the trough bordering Llanoria, early or Middle Cambrian may possibly be discovered hut at present are unknown. Upper Cambrian Upper Cambrian is recognized in surface exposures in Texas in five areas of the state as follows: the Llano uplift, the Marathon and Solitario uplifts, the Van Horn region, and the Franklin Moun­tains. Correlation hetween these widely separated areas is not com· plete, and separate names are for the most part in use for the severa! regions. The Cambrian formations recognized in sudace exposures in the state are as follows : * *For the loeation oí theee regione in the atate see fige. 3 and 4, pp. 28-29. The University of Texas! Bulletin No. 3232 Llano Uplift Marathon and Van Horn Region El Paso Region Solitario Uplifts Ellenburger group, basal part (Emi­nence and Potosi equivalents) F ort Sill and Signa! Mountain Wilberns Cap Mountain Hickory Dagger Flat Van Horn Bliss The Upper Cambrian formations of the Llano region in their underground extension are important water-bearing formations. The Hickory sandstone in particular supplies an abundance of water to wells. The Cambrian, particularly the highly glauconitic facies, contains more or less disseminated lead minerals, chiefly the sulphide, galena. Oíl and gas have not been obtained from the Cambrian formations. However, there seems no inherent reason why the unmetamorphosed, highly fossiliferous sediments of the Cam­hrian, such as are extensively spread over most of the region here mapped as having heen occupied by a Camhrian sea, may not produce oíl under favorable structural conditions. LLANO REGION The Camhrian of the Llano region, as now subdivided, includes the following formations, the oldest being named first: Hickory, Cap Mountain, Wilberns, Fort Sill, Signa! Mountain and the basal part of the Ellenburger group (Potosi and Eminence equivalents) .22 The Cambrian and other Paleozoic formations of the Llano uplift líe in nearly horizontal position or with moderate dip. An exception is found, however, in strata around granite knobs found at the margÍns of the uplift. Around these knobs the Camhrian formations have decided dips up to as much as twelve or sixteen degrees. In such localities the dips are away. from the granite knobs. The conditions here are very like those around porphyry 22Among publications listed in the accompanying bibliography relating to the Cambrian of the Llano uplift are the following: Comstock, 271, 274; Dake and Bridge, 386b; Deen, 402; Jone~ 891 ; Paige, 1170, 1171, 1172, 1173; Roemer, 1330; Shumard, 1465, 1471, 1473; Ulrich, 167.4b; Walcott, 1702, 1703, 1703a-g. The Geology of Texas-Paleozoic Systems knobs in the Ozarks.23 In addition, the strata are cut by the north­east-southwest system of faults which a:ffect both the pre-Cambrian and Paleozoics of this region older than the Strawn, resulting in local pronounced dips. Except as locally a:ffected by faulting and by the granite knobs referred to, the strata dip away from the Llano uplift. Ozarkian and Canadian systems.-In 1911 Dr. E. O. Ulrich pro· posed a new system, to be known as the Ozarkian, named from the Ozark region of Missouri {1647b). The Ozarkian system, as thus proposed, includes a part of the Cambrian and a part of the Ordovician of the current classification. Under this classification, the Fort Sill, Signal Mountain, Potosi, Eminence, and Gasconade formations are placed in the Ozarkian. The Canadian system pro­posed at the same time by Ulrich includes the Ordovician from the top of the Gasconade or its equivalent to the base of the St. Peters. In this publication the terms Ozarkian and Canadian are not used and the division between the Cambrian and Ordovician is placed at the top of the Eminence formation or its equivalent. HICKORY FORMATION The Hickory formation is prevailingly a conglomerate, or sand­stone, which rests on the unevenly eroded surface of the pre-Cambrian schists, gneiss, and granites. Much of the sand is iron stained and in places contains a considerable quantity of iron oxide. Elsewhere it is clean and relatively free of iron. In passing upward it grades into glauconitic sands and limestones of the Cap Mountain formation, the lithologic break between the two formations being not well marked. Near the top some layers of fossiliferous glauconitic limestone alternate with the sandstone. The basal part of the formation varies from place to place in accordance with the character of the underlying pre-Cambrian from which it is derived. Wells drilled into this formation at the margins of the Llano uplift have in most instances obtained an abundance of water. The forma­tion is exposed at many localities at the margins of the Central Mineral region. 23Bridge, Josiah, and Dake, C. L., Initial Dips Peripheral to resurrected Hills, Missouri Bureau of Geology and Mines, SSth Bienni&l Repon, Appendix 1, pp. 1-7, 1929. (Reporta issued November, 1928.) The University of Texasi Bulletin No. 3292 Type locality: Hickory Creek in Llano County; thickness, from a thin stratum to 350 feet or more; correlation, Reagan sandstone of Oklahoma. The formation name was given by Comstock {271). CAP MOUNTAIN FORMATION The Cap Mountain formation consists chiefly of limestone, usually glauconitic. In places it becomes a glauconitic marl heing hut Iittle indurated. In places also, especially near its hase, it is a sandy limestone. The change from the underlying Hickory is gradational and a definite contact is difficult to determine. Sorne of the strata consist very largely of pieces of trilobites. The complete carapace is seldom preserved, notwithstanding that fragments are present in such ahundance as to indicate a sea teeming with trilohite life. With the trilobites, and locally making up parts of the stratum, are small hrachiopods. The glauconite so ahundant in this formation is closely associated with the ahundance of organic material. Fre­quently the glauconite can he seen to lie within the rolled or thickened margins of the trilohite carapaces or spines, and in origin is doubtless associated with the decay of the organic matter. The formation passes by gradation into the overlying Wilhems. The difference between the Cap MPuntain and W'ilbems is not well marked in the lithology, except that there is less glauconite and more shaly material in the Wilherns. Strata of this formation in which trilobites ahound may he seen at Lion Mountain west of Burnet, and at many other localities in the Paleozoic rim of the Llano uplift. Type locality: Cap Mountainin Llano County; thickness, approxi­mately 90 feet. The formation was named by Paige { 1172). It is correlated with the Bonneterre of Missouri and the Eau Claire of Wisconsin. WILBERNS FORMATION The Wilbems formation consists of limestone with sorne shale. Limestone conglomerates are developed locally in the formation. Glauconite is less ahundant than in the Cap Mountain. Overlying the Wilhems are the basal formations of the Ellenhurger group. The contact hetween Wilhems and Ellenhurger, so far as known, presents no appreciahle angularity, although, according to Dake Tke Geolo,qy of Texas-Paleozoic Systems and Bridge, successive formations of the Ellenburger group over­lap and rest upon the Wilberns. The lower part of the Wilberns formation includes flaggy limestones, while the shaly phase is best developed in the upper part. The conglomerate lentils in sorne places consist of flat pieces, often forming edgewise conglomerate. The material of these conglomerates is evidently from the formation itself. This phase of the formation may be seen at exposures on the Llano River and tributaries about ten miles west of Mason. Good exposures of the formation may be seen in the Mason-Brady road south of Camp San Saba. Type locality: Wilberns Glen on Little Llano River in Llano County; thickness, from a thin stratum to 220 feet. The formation was named by Paige (1172). It is correlated with the Davis of Missouri, Honey Creek of Oklahoma, and Franconian of Wisconsin. FORT SILL AND SIGNAL MOUNTAIN FORMATIONS The upper part of the Wilberns as originally defined includes thin-bedded limestones containing an abundance of small round objects identified provisionally as the genus Girvanella, probably an alga. At a higher leve! in the formation are massive, more or less glauconitic limestones. The Girvanella zone, according to Ulrich, is within the Fort Sill formation as defined by him from exposures in Oklahoma, and the higher glauconitic limestones are either of this formation or of the overlying Signa! Mountain limestone (personal communication). In the mapping of the Llano-Burnet quadrangle by Paige this Girvanella zone was usually included with the Wilberns, although at sorne localities it is placed in the Ellen­burger. Good exposures of this part of the formation are found from 2.2 to 3 miles north of Cherokee on the Cherokee-San Saba road. The glauconitic limestone overlying the Fort Still equivalent contains the trilobite Saukiella and small gastropods. Type localities: The type localities of the Fort Sill and Signa! Mountain formations are in the Wichita Mountains of Oklahoma. Descriptions of these formations by Ulrich are given by Dake and Bridge (386b). The fossils obtained from the Cambrian of the Llano region ex­clusive of the Ellenburger include algae, sponge spicules, cystids, brachiopods, gastropods, and trilobites. Extensive limestone reefs in the Wilberns or Fort Sill formation are thought to have been The University of Texas, Bulletin No. 3232 built up by algae. An abundant fossil in the Fort Sill formation is a small oval object, Girvanella sp., probably an alga. Sponge spicules occur at this horizon. Strata of a few inches in thickness in the Cap Mountain or Wilberns formation are in places largely made up of Pelmatozoa stems, probably of cystids. Parts other than the stems are rare. The only published reference to cystids apparently is that of Walcott, who lists cystidean plates from Morgans Creek, Burnet County ( l 703g, p. 213) . Trilobites are in places very abundant, strata of sorne inches in thickness in the Cambrian of the Llano region being made up of fragments of carapaces. Entire specimens, however, are seldom obtain~d. The following species of brachiopods, gastropods, and trilobites are listed by Walcott ( l 703g, pp. 212-213) from the Cambrian of the Llano region. The nomenclature has been revised and brought up to date and the formations which the fossils characterize have been added by J. Bridge and C. E. Resser: Obolus matinalis Cap Mountain Obolus nundina Wilberns Obolus sinoe Wilberns Obolus tetonensis ninus Wilberns? Lingulella acutangula Wilberns Lingulella peratenuatá Wilberns Lingulella texana Wilberns Lingulella u pis Wilberns Lingulepis acuminata Wilberns Acrotreta microscopica Wilberns Billingsella coloradoensis Wilberns Eoorthis iddingsi Wilberns Eoorthis indianola Wilberns Eoorthis remnicha texana Wilberns Eoorthis wichitaensis Wilberns Eoorthis wichitaensis laeviuscula Wilberns Syntrophia alata Wilberns Huenella texana Wilberns Huenella texana laeviuscula Wilberns "Platyceras" texanum Wilberns "Ptychoparia" aflinis Wilberns "Ptychoparia" burnetensis Cap Mountain Wilbernia diademata Wilberns Conaspis llanoensis Cap Mountain? "Ptychoparia"? metra Cap Mountain Pterocephalia occidens Wilberns Conaspis patersoni Wilberns Conaspis perseus var. Wilberns Elvinia romeri Wilberns lddingsia similis Wilberns "Ptychoparia" suada Wilberns Burnetia urania Wilberns The Geology of Texas-Paleozoic Systems Saratogia wisconsinensis Wilberns Camaraspis convexa Cap l\fountain? Dikelocephalus sp. Wilherns Wilhernia pero Wilherns Irvi.ngella sp. Wilherns lrvíngella tumifrons Wilberns Pterocephalia sancti-sahae Wilberns Ptychaspis Wilherns "Crepicephalus" texanus Cap Mountain ELLENBURGER GROUP, BASAL PART (POTOSI AND EMINENCE EQUIVALENTS) The Ellenburger formation was established to include a limestone series exposed in the Central Mineral region of Texas (1172). This series was recognized at the time as being in part Cambrian and in part Ordovician. Recent field work by Dake, Ulrich, and Bridge has shown that the series as a whole can be subdivided on bases both of fauna and lithology. The series includes chiefly limestones and dolomites, sorne of which are chert bearing, and a very limited amount of thin shales and sorne sandy strata. POTOSI EQUIVALENT The Upper Cambrian and Lower Ordovician formations of the Central Mineral region included in the Ellenburger group are very similar both faunally and lithologically to formations of the same age in the Ozark region of Missouri. The base of the Ellen­burger of the northwestern part of the Burnet Quadrangle as described by Paige is marked by massive chert-bearing beds ( 1172). Much of the chert is drusy and the associated dolomitic limestone is coarsely crystalline. This basal part of the Ellenburger is believed by Dake and Bridge (386b) to represent the Potosi equivalent of the Ozark region. This basal formation of the Ellenburger group is exposed near Tow and on the right bank of the Colorado River three-quarters of a mile above Fall Creek. At this last named locality it contains sorne fossils, chiefly gastropods and cryptozoans. Among fossils of the Potosi equivalent are the gastropod Sca.evogyra and fragmentary trilobites. EMINENCE EQUIVALENT Above the Potosi in the northeastern part of the Burnet Quad­rangle is found finely crystallized cherty dolomite containing, according to Dake and Bridge, faunas of the Eminence formation The University of Texas, Bulletin No. 3232 of Missouri. Similar fossils were obtained from about 3.3 miles north of Cherokee on the Cherokee-San Saba road. At a higher level in the Ellenburger other formations are recognized which are described under Ordovician. The most abundant fossil in the Emi­nence equivalent is the trilobite Stenopilus. Euptychaspis typicalis and Plethopeltis also are present (Dake anft Bridge, 386b). Type localities: The type localities of the Potosi and Eminence formations are in the Ozark region of Missouri. EL PASO AND VAN HORN REGIONS BLISS FORMATION The Cambrian is represented in the Franklin Mountains by the Bliss sandstone. This formation is prevailingly fine grained, although a conglomerate is usually found at the base. lt varíes from brown to gray in color. In places it is quartzitic, and elsewhere cross-bedded and less well cemented. The sandstone outcrops in the east facing scarp of the Franklin Mountains and also, to a limited extent, in the Hueco Mountains. In the Franklin Mountains it dips westward. This sandstone rests with an erosiona! unconformity on the forma­tions referred to the pre-Cambrian, the Lanoria quartzite and rhyolite. lt is in apparent conformity with the overlying Lower Ordovician limestone. A few brachiopods have been found in this formation and are identified by W alcott as Lingulepis acuminata, Lingulella, and Obolus materialis (1312). The formation is exposed along the eastern front of the Franklin Mountains and, according to Richardson (1312, p. 3), in the central part of the mountains. lt is found, according to King ( 396b) , at the base of the south scarp of the Hueco Mountains from four to ten miles southeast of Helms W est well and may be seen near the entrance to Padre Mine Canyon. Near here it rests uncon­formably on red granite.24 Type locality: Fort Bliss; thickness, up to 300 feét. The forma­tion was named by Richardson (1312). 24Among publications listed in the accompanying bibliography relating to the Cambrian of the El Paso and Van Horn regions are the following: B~ker, 46; Dumble, 491 ; Richardeon, 1304, 1310, 1312, 1313, 1314. The Geology of Texas-Paleozoic Systems VAN HORN FORMATION The Van Hom region contains one formation referred provi­sionally to the Camhrian, the Van Horn sandstone. This sandstone is coarse grained and in part conglomeratic, particularly in its lower part, becoming finer in texture at a higher leve!. Cross­bedding is present, and the rock is but imperfectly cemented. In coarseness of texture it contrasts with the fine grained underlying pre-Camhrian Millican sandstone. Both sandstones are prevailingly red although the Millican is of deeper color. The Van Horn is a red, arkosic, massively bedded sandstone. From the bottom to the top it contains seams and beds of pebble, cobble, and boulder con­glomerate. The fragments are chiefly red granite and red rhyolite porphyry, hut there are suhordinate fragments of Millican limestone and Carrizo Mountain schist. Four miles west of the Milton ranch, on the south scarp of Sierra Diablo, there are 300 feet of coarse con­glomerate at the hase with well rounded houlders up to 3 feet across. No recognizable fossils have been found in the Van Horn sandstone, and it is placed in the Camhrian by reason of its position in the sec­tion.25 lt rests unconformahly, with gentle dips, on the steeply in­clined Millican and Carrizo Mountain formations. In the Van Horn region the Camhrian sandstone is affected by pronounced faulting, but does not show the complicated structural conditions seen in the underlying pre-Cambrian formations. According to King (Guide, 16th lnternational Geological Congress, 396h), it is separated from the Lower Ordovician, El Paso, limestone by an angular unconform­ity. The formation may he seen in good exposures at the south end of the Baylor Mountains and four miles south of Victoria Peak he­tween the Baylor Mountains and the Diablo Platean; at the west side of Beach Mountain; and at the foot of the Sierra Diablo north of the Hazel silver mine. Richardson (1314, p. 4) describes the formation as exposed over an area of about ten square miles north­west of Van Horn. Type locality: "Red Valley" 3 miles northwest of Van Horn; thickness, up to 700 feet. The formation was named by Richard­son (1314). 2'Streeruwits is eaid to have found borings in thi1 1andstone identified by Walcott as Scolithe1 lineari.s (491, p. 104). According to King these are from an overlying unit which he placea in the Ordovician. The University of Texas Bulletin No. 3232 MARATHON AND SOLITARIO UPLIFTS The Marathon uplift is located in west Texas chiefly in the northern part of Brewster County. Originally the uplift was capped by Cretaceous strata, which, however, have been removed by erosion, thus exposing a core of Paleozoic rock. The area of exposed Paleozoics is 35 or 40 miles across and is irregularly circular in outline. Previous to the formation of thil? great dome, the early Paleozoic rocks had been highly folded, overturned, and in places overthrust. These movements, which have Appalachian trend,affected the Pennsylvanian and older formations, but not, so far as known, the Permian, which was but mildly folded and tilted. The formation of the uplift itself, aside from the thrusting and folding, was not completed until post-Cretaceous time, as shown by the fact that the Cretaceous of the rim rock dips gently away from the uplift, the Laramide and later folding being superimposed upon the already complicated Paleozoic folding. The Marathon Basin.-The Marathon basin, which occupies the crest of the uplift, has been developed by erosion. In this basin are exposures of Cambrian, Ordovician, Devonian, and Pennsyl­vanian formations ali intensely folde~. At the margins of the basin forming the scarps are Permian and Cretaceous formations. The Permian formations, dipping to the northwest, have by erosion formed a pronounced basin-facing scarp. On the opposite side, east and southeast where the bordering formations are Cretaceous in age and of slight (2°-5°) dip, the basin is not limited by a so well marked scarp. To the southwest the basin finds its limits in ranges produced by the Cordilleran folding.26 DAGGER FLAT FORMATION The base of the Paleozoic is not seen in the Marathon uplift. However, in sorne of the anticlines in the basin, rock as old as Cambrian, Dagger Flat formation, comes to the surface. This formation is exposed in the Marathon and Dagger Flat anticlinoria of the Marathon uplift (936a). The strata at these exposures are much crumpled by intense folding. Much of the formation is sand­stone including ledges four or five feet thick passing at a higher 26Publications relating to the Cambrian oí the Marathon uplift listed in the accompanying bibliography include the following: Baker and Bowman, 44; King, 936a. The Geology of Texas-Paleozoic Systems level into flaggy and thinly laminated micaceous sandstone with shale predominating at the top of the formation. The formation is sparingly fossiliferous. The fossils obtained include the brachiopod genera Lingula and Obolus, and the trilobite Agnostus. In their publication on the Glass Mountains issued 1918, Baker and .Bowman (44, p. 81) obtained severa! fossils from anticlines south of Marathon and east of Peña Colorada Creek. The fossils obtained at these localities include the Cambrian genera, Lingulella, Acrotreta, and Acrocephalites. King, however, finds that the rocks from which the fossils were obtained at these localities are trans­ported boulders and that they occur in the W oods Hollow forma­tion which is Ordovician. He states also that the fauna of these houlders is of a facies unlike that known in any exposure in the Marathon basin. Certain of the boulders also contain the Upper Ozarkian trilobite Symphysurina. SOLlTARIO UPLlFT The Solitario is a pronounced small uplift located on the border line of Presidio and .Brewster counties 10 or 15 miles from the Río Grande and 40 or 50 miles southwest of the Marathon uplift. This uplift, like the Marathon uplift, was formerly capped by a Cre­ taceous covering, which has now been largely removed by erosion. Although only a few miles across, the dome involves uplift of severa! thousand feet. The Solitario Basin.-The erosiona! basin resulting from the dis­ section of the Solitario dome is about four and one-half miles across and is depressed below the average elevation of the surrounding rim from 500 to 1,000 feet. Within this basin are exposed formations ranging in age from Upper Cambrian to Carboniferous. Over­ lying the Carboniferous, except where removed by erosion, is a great section of Cretaceous. The Paleozoic rocks of this dome are in­ tensely folded, faulted, and in sorne places overthrust, the trend lines being in general northeast-southwest. The folding giving this trend antedates the Cretaceous and is of the Appalachian trend. The uplift giving rise to the dome is post-Cretaceous and modifies the pre­ Cretaceous folding accordingly. The dip in the strata at the margin of the folds is in places as much as 45º. The University of Texas Bulletin No. 3232 From the Solitario uplift, 50 miles or more southwest of the Marathon uplift, fossils have been obtained by Sellards and Baker which are identified by Edwin Kirk of the United States Geological Survey as Upper Cambrian. The fossils identified were as follows: Lingulella sp., Obolus sp., Agnostus sp. The formation containing these fossils is probably the same as the Dagger Flat of the Marathon region. The Dagger Flat formation in the Marathon uplift is exposed in · steeply folded anticlines which trend northeast. In the Solitario uplift the structural conditions are complicated, but the trend of the Paleozoic.folding is as in the Marathon Region. Type locality: Dagger Flat northeast of Buttrill ranch. The hase of the formation is not exposed and the full thickness is unknown; a maximum of 300 feet is seen. The formation was named by King ( 936a, p. 1064) . Illustrations of sorne Camhrian fossils are given in Plate II. UNDERGROUND POSITION OF THE CAMBRIAN IN TEXAS The Cambrian has been encountered by well drilling in severa! counties adjacent to the Llano uplift. At the south of the uplift the Cambrian is found in Gillespie County, where it appears to have a thickness of ahout 1,000 feet. This depth, however, is based on a single well and may be in error. At the north of the Llano uplift the Cambrian is reached in wells in Brown, Lampasas, McCulloch, Mills, and San Saba counties, where thicknesses up to as much as 600 feet are indicated. By utilizing wells drilled into the Lower Ordovician the approximate position of the Camhrian is determined west of the Llano uplift to Reagan County, and also north as far as Young County. In northern Texas in the eastern part of the Red River uplift the Cambrian is reached in a number of wells. In Clay County the Cambrian is recognized. Its thickness, however, is not definitely determined. In Montague and Cooke counties it is present, although with undetermined thickness. In Foard County no Cambrian has been recognized in wells drilled into metamorphic rocks. The Cambrian is likewise absent, so far as known, from the Texas Panhandle. The Geology of Texas-Paleozoic Systems The table (pp. 192-229) contains a list of wells entering that part of the Cambrian lying underneath the Ellenburger group in Texas. CAMBRIAN SEAS IN THE TEXAS REGION Lower and Middle Cambrian.-No proof has been obtained of a Lower or Middle Cambrian in the Texas region, the oldest deposits known both on the surface and underground being of Upper Cambrian age. In the Ouaohita geosyncline of Oklahoma and Arkansas the lowest formation exposed is the Collier shale, the age of which is imperfectly known. Ulrich (1674b, p. 676) expresses the view that it may be Lower Cambrian, but Honess (838), finding no diagnostic fossils, considers the age undetermined. lts position under Lower Ordovician places it as probably Cambrian, but a more exact reference cannot now be made. The Ouachita and Marathon areas were probably connected by a geosyncline which is now con­cealed under the Coastal Plain. This geosyncline was formed as a trough in front of the land mass Llanoria. At no place in this geosyncline has the base of the Paleozoic been seen, and there are as yet no records showing whether or not this geosyncline was invaded by Lower or Middle Cambrian seas. The similar geosyncline formed in front of Appalachia contains Lower Cambrian deposits (1383, p. 187). U pper Cambrian.-The surface exposures supplemented by the records from well drilling indicate an Upper Cambrian sea which extended across central Texas. Points by which the position of the sea may be approximately located are afforded by well records in Denton, Cooke, and adjoining counties; surface exposures in the Llano, Marathon, and Solitario uplifts, and surface exposures in the Van Horn and Franklin mountains. Initial deposition in this sea as it invaded a previously exposed land surface was chiefly sands, followed over much of the area by glauconitic sand and lime­stone with sorne shales. The westward shore of this sea is possibly indicated by the absence of Cambrian in the Panhandle region of Texas and, so far as the limited records go, in Foard and Pecos counties. On the other hand, the sea may have extended westward across this region, the resulting deposits having been removed by erosion. The location The University of Texas Bulletin No. 3232 of the Upper Cambrian sea in Texas, as nearly as can now be shown, is given in Figure 7.27 1 1 1 OKL A HOMA n -­ LtGE.NO S '~l·<;_ll'.Ul~N OV"~OI' ~ LCM'Ul~.l.llOUl'l.....,,.OU1C-.FOAlV..M01,t.Ctt5. ~ PQDU.lllDIC I• lE]JW...tDto1t.O•nll::U.'Jlftn)lln.l~N'GICtf:C'!JM5)UtC.lltlM:.lOUS .C!l U~H C.»lt.:UIJt 11.l.l.C.IU 'y 'llilW. ot lNflUU> r;;oit W~l.I(\ 0~1c;.o, Fig. 7. Map showing probable extent of Upper Cambrian sea in Texas. RELATION OF THE TEXAS CAMBRIAN TO THAT OF THE ADJOINING STATES The sea in which the Texas Cambrian sediments accumulated is part of a great Upper Cambrian inundation which spread over a large part of the Mississippi Valley, and continued westward across southern Oklahoma, central Texas, and southern New Mexico and across much of the present Rocky Mountain region. Within this sea in Texas were deposited the formations already described. 27Publications relating more particularly to the extent of tbe Upper Cambrian seas in the Texas region listed in the bibliography inelude the following: Schuchert, 1382b, 1383; Sellards, 1440, 1443. The Geology of Texas-Paleozoic Systems In Oklahoma similar deposits accumulated in the Arbuckle-Wichita region. Farther to the northeast, lithologically and faunally related Upper Cambrian deposits are brought to the surface in the Ozark uplift. Similar deposits come to the surface in the Black Hills of South Dakota, in the Big Horn Mountains of Wyoming, and in Colorado, Utah, New Mexico, Arizona, and elsewhere. The deposits within this great interior sea present characteristics which vary with depositional conditions. Throughout much of the region the Upper Cambrian rests on pre-Cambrian, the Middle and Lower Cambrian being absent. The basal beds are very commonly detrital in nature, consisting of sands and arkosic materials. In a general way these basal deposits of the Upper Cambrian may be correlated, although it cannot safely be assumed that they are in all respects contemporaneous. Among names applied to these sedi­ments in the extensive region covered by the Upper Cambrian sea are Lamotte sandstone in the Ozarks, Reagan sandstone in the Arbuckle-Wichita region of Oklahoma, Hickory sandstone in the Llano uplift of Texas, and Bliss sandstone in the El Paso region of Texas and New Mexico. In the Texas region, as already stated, the basal sandstones are succeeded by calcareous and glauconitic deposits including lime­ stone. This is true also in the Arbuckle-Wichita region of Okla­ homa, the Ozark Mountains of Missouri, and the Black Hills of South Dakota. In Oklahoma, as in Texas and sorne other localities, the latest Cambrian deposits in this sea include dolomitic limestone. The next succeeding deposits in the same regions were likewise of similar character, so that the exact dividing line between Cambrian and Ordovician is difficult to locate. ORDOVICIAN SYSTEM Ordovician formations are exposed at the surface in five areas in Texas as follows: the Llano, Marathon, Solitario, Van Horn, and El Paso regions. The deposits include a shaly sandstone and chert facies in the Marathon and Solitario regions and in the other regions a magnesian limestone facies. Sorne of the well-crystallized limestones of the Ellenburger group have been quarried to a limited extent as marbles and for terrazzo material. These limestones underground contain a large supply of The University of Texas Bulletin No. 3232 water which is usually highly impregnated with carbon bisulphide gas. Sorne petroleum has been produced from the limestone~ of the Ellenburger group at severa! localities in north-central Texasz and commercial production has been obtained from these formations on the Red River uplift. The deep production in Reagan County, from 8450 to 8772 feet, is from the Ordovician. The maximum depth drilled in this field to the end of 1932 is 9562 feet in Well No. 1-C. The Ordovician formations recognized in surface exposures in the state are as follows:* Llano Region Van Horn El Paso Marathon ' Region Region Region Upper Ordovician Wanting Montoya Montoya Maravillas ( Cincinnatian) Middle Ordovician Wanting Wanting Wanting W oods Hollow (Mohawkian) Fort Peña Lower Ordovician Ellenburger El Paso El Paso Alsate (Beekmantown) group Marathon (Cambrian in part) LLANO REGION ELLENBURGER GROUP The Lower Ordovician is present in the Llano region and is included In and comprises the upper part of the Ellenburger forma· tion as originally defined. However, severa! distinct units may be · recognized in the Ellenburger group, some of which, as already stated, are Cambrian in age. The Lower Ordovician of the Central Mineral region closely resembles that of the Ozark region, and, according to Dake and Bridge, the equivalents of several of the Missouri formations are recognizable in the Ellenburger group (386b) .28 GASCONADE EQUIVALENT The equivalent in the Ellenburger group of the Gasconade forma­tion is a crystalline dolomite with more or less chert. This dolomite is divided into an upper and lower member by severa! beds of dense, *For the location of these regions in the state see figs. 3 and 4, ' pp. 28-29, 28Puhlications relating to the Ordovician of tbe Llano _region listed in the accompanying bihliography include the following: Comst~ck, 271, 274; Dake and Bridge, 386b; Janes, 891; Paige, 1172; Roundy, Girty, and Goldman, 1354; Shumard, 1470; Uddea. and Waite, 1669; Ulrich, 1674b. The Geology of Texas-Paleozoic Systems fine-grained, snow-white limestone. Fossils are present although not abundant. This formation may be seen in the bluff on the left side of the Colorado River opposite the mouth of Jim John Creek in the northwestern part of the Burnet Quadrangle. The rock exposed, here about 100 feet above the base of the section, is a dolomitic limestone containing fossils and sorne chert. The full thickness of the limestone at this locality was not determined but is in excess of 260 feet ( 386b). The formation is exposed also on the Cherokee­San Saba road from about 5 to 7.4 miles north of Cherokee. A quarry now abandoned has been opened in the limestone member of this formation east of the road, 6. 7 miles north of Cherokee. On the Mason-Brady road 0.8 miles north of the San Saba River, a dense limestone, regarded by Dake and Bridge as a middle member of the Gasconade, rests upon the Signal Mountain formation, the intervening formations, Potosi, Eminence, and lower Gasconade being absent at this exposure. The fossils recognized by Dake and Bridge in the Gasconade equivalent in Texas are Helicotoma uniangulata (Hall), Pelagiella paucivolvata (Calvin), Gasconadia putilla (Sardeson), Sinuopea humerosa Ulrich, Sinuopea, 3 or 4 undescribed species, Hypselo­conus sp., Ozarkina ty pica Ulrich and Bridge, Ozarkina sp., Ec­cyliomphalus gyroceras (Roemer), undescribed species referable to Levisoceras, Dakeoceras, Ophileta, Heliocotoma. Type locality: The type locality of the Gasconade formation is in the Ozark region of Missouri. ROUBIDOUX EQUIVALENT The equivalent in the Ellenburger group of the Roubidoux forma­tion of the Ozark region is a cherty dolomite. On the Cherokee­San Saba road 8.4 and 9.1 miles from Cherokee, fossils charac­teristic of the Roubidoux formation ( 386b) are found in abundance. The thickness of the section cannot be measured at this exposure. However, on and near the Llano River, 10 miles southwest of Mason, Dake and Bridge recognized a lower member 100 feet thick consist­ ing of gray cherty dolomite, and an upper member of dense white limestone about 250 feet thick, both containing Roubidoux fossils. Among fossils reported by Dake and Bridge (386b) from the Roubidoux equivalent in Texas are the following: Syntrophina The University of Texas Bulletin No. 3232 campbelli (Walcoti:), Roubidouxia sp. undescribed, Lecanospira sanctisabae (Roemer) , O phileta. Other gastropods, trilobites, and cephalopods are also present. Type locality: The type locality of the Roubidoux formation is in the Ozark region of Missouri. JEFFERSON CITY AND COTTER EQUIVALENTS The equivalent in the Ellenburger group of the Cotter formation of the Ozark reg~on is chiefly a pinkish-gray crystalline limestone. In an exposure on Honey Creek, 10 miles southeast of Llano, the uppermost 500 feet of the Ellenburger group is limestone of this character. Within 30 or 40 feet of the top of the section is a fossilif­erous zone regarded by Dake and Bridge as Cotter in age or younger, and the upper 500 feet of this section is referred by them to Cotter or possibly in part to the underlying Jefferson City. Other localities yielding Jefferson City or Cotter fossils are as follows: 9.7 and 11.4 miles south of Cherokee on the San Saba road; and 1.5 miles south of the Colorado River on the J ohnson City road. The most abundant fossil, coming probably from the Jefferson City equivalent, is the sponge, Calathium. From higher in the sec­tion, probably the Cotter equivalent, Dake and Bridge obtained the following: Orospira cf. bigranosa Ulrich, Ceratopea, 2 species, Ophileta cf. canadaensis (Billings). Type localities: The type localities of the Jefferson City and Cot­ter formations are in the Ozark region of Missouri and Arkansas. These several units, the Gasconade, Roubidoux, Jefferson City, Cotter, and perhaps others, although recognized as present in the Ellenburger group, have as yet been but imperfectly delimited, and the surface distribution of each cannot now be given. The Ellenburger group as a whole, including both the Cambrian and Ordovician formations, on the surface and underground, is widespread in Texas. lts thickness ranges from a thin stratum to 2,000 feet. This great irregularity is due in part to erosion, the for­mation having in places been removed. An unevenness in thickness occurs likewise through absence of sorne of the formations of the group. Thus Dake and Bridge find the Cambrian formations of the Ellenburger (Potosi and Eminence equivalents) present in the north­western part of the Burnet Quadrangle but absent farther west at The Geology of Texas-Paleozoic Systems Camp San Saba, the overlying upper Gasconade there resting on the Signal Mountain formation. This absence of the Potosi and Em­inence equivalents is interpreted by them as evidence of overlap, although it may, of course, also represent an erosion interval he­tween the Eminence and Gasconade. Owing to the great economic importance of recognizing the Ellen­burger in drilling, this group of formations has heen extensively studied from well cuttings, and its place underground has heen determined over a large area in the central part of the state. The limestones and dolomites of this group are separable from other formations in this part of the section by their lithologic character­istics, thus facilitating their identification in wells. The minute texture of the dolomitic limestones as seen in thin section is distinc­tive (1669). The insoluble residues afford criteria by which not only the group but the severa! formations may he more or less readily recognized. Megafossils are present at severa! horizons, as indicated in the preceding description of formations. The outcropping helt of the Ellenhurger formations encircle the Llano uplift and sorne formations of the group evidently formerly extended across the uplift. In its present structural relations it clips away in all directions from this uplift. The maximum thickness of the group as revealed by well drilling is found in eastern Brown, eastern McCulloch, Mills, and western Lampasas counties. This area is between the Lampasas and Bend arches. The present great thickness of the Ellenhurger group in this region may be due to non-erosion in pre-Bend time, or may he due to non-deposition on the Bend and Lampasas arches if they were positive elements as early as Ordovician time, which is possihle. In these counties, Ellenhurger thicknesses are found as follows: south­eastern Brown County, Cress well, 1,346 feet; southeastern McCul­loch County, Beasley well, 1,235 feet; Milis County, Harrison well, 1,525 feet, and western Lampasas County, Wittenhurg well, 1,977 feet. Much thinner Ellenhurger is found in the western part of these counties and farther west, as follows: western Brown County, Fuller well, 1,074 feet; western McCulloch County, Zella well, 875 feet, and White well, 952 feet; and Taylor County, Wehh well, 561 feet. On the Lassiter farro in Palo Pinto County a well was drilled The University of Texas Bulletin No. 3232 1,600 feet in to the . Ellenburger without reaching the bottorn of the formation. On the Red River uplift, thicknesses of the Ellenburger are record­ed varying from a thin stratum to 1,000 feet. Thus, in the Whaley well of McElreath and Suggett and in the Donald well, Gulf Pro­duction Cornpany, in Cooke County, the Pennsylvanian rests di­rectly on pre-Cambrian, the early Paleozoic being absent. This is true also of Matthews 1 and 3 of the Shell Company in· Foard County. In the Daugherty well, Benson Brothers, Cooke County, the thickness of the Ellenburger is 961 feet. VAN HORN AND EL PASO REGIONS EL PASO FORMATION The Lower Ordovician is represenied in the Van Horn and El Paso regions by a magnesian lirnestone, the El Paso forrnation. In the Van Horn region this formation consists of gray rnagnesian limestones with sorne chert and, near the base, lenses of sandstone. It is exposed in Beach and Baylor rnountains. In the El Paso region the formation, consisting of rnagnesian limestone and sorne chert, is exposed in the Franklin and Hueco rnountains. In the Van Horn region, according to Richardson (1314), the forrnation is sparingly fossiliferous throughout, the fossils being of Beekman­town (Lower Ordovician) age. The remainder contains a few Lower Ordovician fossils. The El Paso limestone is mottled and well bedded. In sorne of the original descriptions there was included with the Van Horn forrnation a series of quartzose sandstones and grits, which grade into the El Paso limestone above, and which contain, to. near their base, Ordovician fossils. lt was in these. beds that Streeruwitz reported worrn borings. The quartzose sandstones rest with a clean-cut contact on the Van Horn arkoses, and in view of their Ordovician fossils and their relations to the limestone above, they are now placed as the basal rnernber of the El Paso lirnestone.29 The more comrnon fossils of the El Paso forrnation are: a sponge, Calathium sp.; gastropods including Ophilita sp., Maclurea sp.; andan orthoceroid related to Piloceras or Cameroceras (1312) . .Publications relating to the Ordovician of the Van Hom and El Paso region1 listed in the accompanyinJ bibliograpby include tbe followln¡: Baker, 46;. King, 936b; Richardaon, 1304, 1310, 1312, 1314; Streeruwitz, 1561, 1566. The Geology of Texas-Paleozoic Systems Type locality: Franklin Mountains in the El Paso region; thick­ness, 1,000 feet. The formation was named by Richardson ( 1304) . MONTOYA FORMATION The Montoya formation found in both the Van Horn and El Paso regions is similar in character to the El Paso limestone. In the El Paso region it is seemingly conformable with the El Paso formation and is separable only on the evidence of the fossils. In the Van Horn region sandstorie is found locally at the base of the Montoya, varying in thickness up to 100 feet. Exposures are found at the southern end of the Franklin Mountains and generally as a narrow band in the upper part of the east-facing scarp of the mountains. In the Hueco Mountains the formation may be seen in Long Canyon about 4 miles east of Helms West well (King, 396b), and 9 miles southeast of Hueco Tanks (1312, p. 4). In the Van Horn region it may be seen at the southeast side of Baylor Mountain and capping Beach Mountain. In addition, King has observed the limestones in the east scarp of northern Sierra Diablo between Marble and Apache canyons (936b, p. 96). In the lower part of the formation fossils are abundant, representing, according to Ul­rich and Kirk, a Cincinnatian fauna. The fossils include severa} well known Upper Ordovician brachiopods, the sponge Receptacu­lites, and various corals, such as Halysites. The Montoya formation is predominantly thickly bedded, and crops out in bold ledges, such as those on the crest of the Franklin Mountains at its southern end. Moreover, the formation is char­acteristically very cherty, with the cherts occurring as long lenticles in the limestone. The best exposure of the Montoya limestone in the region is at the south end of the Franklin Mountains at the high point on the El Paso scenic drive. Excavation for the road has revealed its basal contact and to the west several hundred feet of its lower beds. Type locality: Franklin Mountains, east of Montoya station, 10 miles north of El Paso; thickness, 250 feet. The formation was named by Richardson (1312). The University of Texas-Bulletin No. 3232 MARATHON AND SOLITARIO REGIONS The Ordovician of the Marathon region includes extensive de­posits of shales, sandstones, limestones, and cherts. King has re­cently divided the Ordovician of the Marathon region into five for­mations as follows: Marathon, Alsate, Fort Peña, Woods Hollow, and Maravillas (936a) .30 MARATHON FORMATION The Marathon formation consists of flaggy beds of limestone, prevailingly gray or black in color and usually dense in texture. Shale partings are interbedded with the limestone and greenish clay strata are present. Sorne sandstone and conglomerate are found in the formation and also a limited amount of chert. The formation is exposed on the surface at the town of Marathon, and at the north­east end of Dagger Flat anticlinorium. Good exposures are seen also 3 miles west of old Fort Peña Colorada and on Alsate Creek. The relative amount of limestone in the formation increases north­ward, and to one of the limestone members, approximating 75 feet in thickness near the middle of the formation, King has applied the term Monument Spring dolomite (936a, p. 1068). This member, in which Kirk found a resemblance both in lithology and fauna to the El Paso limestone, thins and disappears southward. The fauna of the Marathon formation includes many graptolites, among which are Tetragraptus, Phyllograptus, Didymograptus, Go­niograptus, Loganograptus, and Dictyonema. Brachiopods, ptero­pods, trilobites, and sponges are present. According to identifica­tions made by Kirk, the fauna indicates Deepkill (Beekmantown) age. A small collection of graptolites made in the central part of the Solitario uplift by Sellards and Baker in March, 1931, was found by Ruedemann to contain Phyllograptus ilicifolius, Tetragraptus fruticosus, and Didymograptus bifidus. These indicate, according to Ruedemann, middle Deepkill (Beekmantown). The approximate equivalent of the Marathon formation, therefore, is found in the 80publications relating to the Ordovician oí the Marathon and Solitario regions listed in the accompanying bibliography include the following: Marathon: Baker, 44; King and Bowman, 936, 936a; Solitario: Powers, 1249; Sellards, Adkins, and Arick, 1436; Udden, 1626. The Geology of Texas-Paleozoic Systems Solitario uplift. The limestone facies, however, is less well devel­oped there. Type locality: Marathon; thickness, 500 to 1,000 feet. The forma­tion was named by King (936a). ALSATE FORMATION The Alsate formation is chiefly a shale with varying amounts of limestone. lt is well exposed on Alsate Creek a few miles south­southwest of Marathon, and in the Marathon and Dagger Flat anti­clinoria. In the northern area of its exposures it is largely shale with sorne sandstone and conglomerate. Southward it contains numerous thin limestone strata, and in the Dagger Creek anti­clinorium, where it is 125 feet or more thick, contains limestone ledges similar to those of the overlying Fort Peña formation. Graptolites are present in this formation, including Oncograptus, Didymograptus, Tetragraptus, Phyllograptus. In the formation is found also the gastropod M aclurea, a small Orthis, and a few trilo­ bites. The fauna, according to Kirk, indicates high Beekmantown. Type locality: Alsate Creek, 2Y2 miles west of Fort Peña Colo­ rada; thickness, 25 to 125 feet. The formation was named by King (936a). FORT PEÑA FORMATION The Fort Peña formation consists of thick hedded limestones and cherts with sorne thin partings of shale. The chert layers are usually thin, although in sorne localities they reach a thickness of 3 or 4 feet. At the hase is a conglomerate consisting of pieces of chert, limestone, and sandstone. Fossils are not ahundant in this formation. However, a small fauna ohtained by King indicates the Middle Ordovician age of the formation. The genera listed by him are Climacograptus, Diplograp­ tus, Didymograptus, Tetragraptus, Ceraurus, Bucania, Orthis, and other hrachiopods. Graptolites ohtained from the Solitario were identified by Ruede­ mann as including Diplograptus (Glyptograptus) angusti/olius Hall of Normanskill (Chazy) age. It would seem, therefore, that the ap­ proximate equivalent of the Fort Peña formation is found in the Solitario uplift. The University of T.exas Bulletin No. 3232 Type locality: ridge north of Fort Peña Colorada; thickness, 125 to 200 feet. The formation was named by King (936a). WOODS HOLLOW FORMATION The lower part of the W oods Hollow foonation consists, accord­ing to King, of flaggy thinly laminated gray or yellowish sandy limestone, or limy sandstone with shale partings, and grades upward into greenish clay shale with a few interbedded limestone layers. Sorne beds of nodular limestone are present which contain com­minuted remains of various fossils. Exposures of this formation are found in the Marathon region between W oods Hollow and Little W oods Hollow Creek on the former Louis Granger ranch. Other exposures are seen near Peña Blanca Spring and Garden Springs. An abundant fauna is found in this formation including graptolites, bryozoa, trilobites, brachio­pods, and bivalves. This fauna indicates Middle Ordovician age~ approximately Trenton. Collections made from the Solitario by Sellards and Baker in 1931 were identified by Kirk as containing the following fossils: Trematis, Orthis, Ceraurus, Hebertella. These, in the opinion of Kirk, indicate the W oods Hollow formation. Type locality: Woods Hollow Mountain; thickness, 470 feet. The formation was named by King (936a). The sediments making up . the four formations last described~ which are of a considerable thickness, were placed originally by Baker and Bowman in the Marathon series. Formation names were not assigned at that time to the subdivisions of this series. From fossils then obtained, however, it was recognized that the Marathon series included formations of both lower and upper Ordovician age (44). MARAVILLAS FORMATION The lower part of the Maravillas formation consists of thick ledges of dark-gray limestone with interbedded thin layers of dark chert and thin dark bituminous limestones. Sorne thin conglomerate beds are present. Southwest of Marathon, near Monument Springs and Rock House Gap (Payne Ranch), these conglomerates, con· taining cobbles and boulders, reach a thickness of from 10 to 20 feet. The Geology of Texas-Paleozoic Systems The upper part of the formation consists very largely of thin­bedded black chert. Thin layers of bituminous limestone and shale are found in this part of the formation between the chert strata. One of these shale strata has a thickness of about 5 feet. At its base where conglomerate beds are present this formation, according to Baker and Bowman, rests unconformably on the older beds. A pronounced erosiona! break separates it from the overlying Ca­ballos novaculite. The formation is extensively exposed in the Mara­thon area. Among easily accessible exposures are those at Fort Peña south of Marathon. The Maravillas formation is ahundantly fossiliferous, particularly in its lower part. The fauna obtained by Baker and Bowman, which includes graptolites, bryozoa, brachiopods, corals, and trilobites, was identified by E. O. Ulrich and was at that time regarded as being in part Trenton and in part Richmond in age. A re-study of this and related faunas from the western United States has led Kirk to regard these faunas as representing Cincinnatian only. Ac­cordingly, the Maravillas is now regarded as being entirely Upper Ordovician. Kirk regards this formation as the approximate equiva­lent of the Montoya formation. The fossils of this formation have been listed by Baker and Bowman ( 44, p. 89) . The Maravillas formation is present in the Solitario uplift, where, as in the Marathon area, it forms prominent cliffs. In the eastern part of the basin this formation is exposed in several northeast trending anticlines. Near the northeast and the southwest margins of the basin the Maravillas occurs in large fault blocks. The thick­ness of the formation has not been measured at this locality, but it is obviously several hundred feet thick. Type locality: Maravillas gap, 20 miles south of Marathon; thick­ness, 100 to 400 feet. The formation was named by Baker and Bowman ( 44). Overlying the Maravillas chert in the Solitario uplift is a green shale, the maximum observed thickness of which does not exceed 25 or 50 feet. This shale, lying between these heavy cherts and the Devonian novaculite, is but imperfectly exposed and as a rule is seen only as a grass covered slope between these two formations. The hest exposures seen were in fault blocks in the southwest and northeast parts of the basin. A similar shale of lesser thickness is The University of Texas Bulletin No. 3232 locally present in the Marathon uplift, where it is occasionally present between the Maravillas chert and the Caballos novaculite ( 44, 936a). Illustrations of sorne of the fossils of the Ordovician systems are given in Plates III and IV. UNDERGROUND POSITION OF THE ORDOVICIAN IN TEXAS Lower Ordovician.-Through the aid of well drilling, the position of the Lower Ordovician underground is located over an extensive region in central Texas and thence north to the Oklahoma line. From its outcropping belt in the Llano uplift the Ellenburger lime­stone dips away in all directions. To the east and southeast its extent is limited, since it is not present in wells drilled in Caldwell County. To the southwest and west it has been found to be present where wells have penetrated the overlying formations. To the north and northeast of the Llano uplift the formation is entered by numerous wells as far north as Young County, and is again brought within reach of the drill on the Red River uplift in Denton, Cooke, and Montague counties. lt is ab_sent, so far as records have shown, from the crest of the highs in the Red River uplift, in the Panhandle region, and in Foard and Pecos counties. On the other hand, it is possibly present at the sides of these uplifts, and, if so, its former extent entirely across western Texas is thus indicated. The counties in which wells have been drilled into or through the Ellenburger group in central Texas are as follows: Brown, Callahan, Coleman, Comanche, Concho, Cooke, Coryell, Denton, Eastland, Edwards, Erath, Hood, lrion, Jack, Kimble, Kendall, Lampasas, McCulloch, Menard, Mills, Palo Pinto, Reagan, Run­nels, San Saba, Shackelford, Stephens, Throckmorton, Sutton, Wichita?, Wilbarger?, Y oung, Crockett. In Grayson County in northern Texas, well drilling has revealed Ordovician shales and cherts of the Ouachita facies (1117). In Reagan and Crockett counties deep drilling has revealed the pres­ence of Middle Ordovician, Simpson or Chazy series, underlying the Permian basin. * These sediments _include shales, sandstone, and •A well entering the Ellenburger in Crockett County (Stanolind Oil Company No. 1 Todd); not indicated. in fig. 8, p. 81, wns completed in December, 1932, while this report was in preH. (Identification of samples by ·H. A. H'emphlll.) The Geology of Texas-Paleozoic Systems limestones (1428). The Upper Ordovician has not been found in drilling.31 ORDOVICIAN SEAS IN THE TEXAS REGION Lower Ordovician.-From surface exposures and well records it is possible to locate an extensive sea in Lower Ordovician time, reaching, as did the Upper Cambrian sea, entirely across Texas from northeast to southwest. Two facies of deposition are present, geosynclinal at the southeastern margin of the sea, and foreland over a larger region. In the foreland facies deposition during Lower Ordovician time consisted largely of magnesian limestone, 1 O LAHOMA COLUMl!.IA NC1N C.OVUtl.D uc.tP'l' ~.IU.UllC~ INC)IC..l.Tl0 LtGrnO ~ Plll<.u'.wtllW Oll'tt'-OI' ~ !.DWU ~....OU.."\~WCMC-. fOe.OIA~ .....DUI U.T l llO.LtD?.ClC ~tl)J,; O.f THE. LLJ;.NORIA 6EOSYNC.UNE UNOtR CFIE.TAC.E.OUS [!) LD''ICW. llE.ACfJ(A!IDCN<.-a.MOVTCllCll'. r OUll.lll) UOts (]J Ul-mite and gypsum. Blaine Fonnation Childress dolomite and gypsum, Lloyd and Thompson, 1929; Childress, Childress County; (1001, p. 952). Top member of the ·Blaine about 150 feet above the Guthrie (Aspennont) dolomite in Childress County (Lloyd and Thompson). Ideal gypsum, same as Childress. Wagon Yard gypsum, Stonn, 1929; Stonewall County; about 300 feet above the Guthrie (Aspennont) dolomite; (1853). This is apparently the same as the Childress dolomite and gypsum. Although proposed at about the same time, the tenn Childress is in more common use. Guthrie dolomite, Cheney, 1929; Guthrie, King County; top of main gypsum series of the Blaine as defined by Lloyd and Thompson; (247, p. 25, and 1001, p. 951). Aspermont d()lomite, M()rley, 1929. Same as the Guthrie which was pro­posed at about the same time. The Guthrie has been more commonly used. Acme dolomite, Lloyd and Thompson, 1929; Acme, Hardeman County; 100 or 200 feet below the Guthrie dolomite. The Acme dolomite is probably the same as the McCaulley. McCau/,ley dolomite, Cheney, 1929; M;ceaulley, Fisher County; (247, p. 26). Beli!lVed to be the same as the Acme dolomite. The term Acme is in more general usage than McCaulley. Mangum dolomite, Gould, 1905; Mangum, Greer County, Oklahoma; 150 or 200 feet above base of the Blaine formation; (1001, p. 951). Groesbeck dolomite, Cragin, 1897; in the Blaine (329a). Collingsworth gypsum, Gould, 1905; Collingsworth County, Texas; upper gypsum of Blaine fonnation (6148, p. 70). Quanah gypsum, Cragin, 1897; near base of Blaine (392a). San Angelo Fonnation Blowout Mountain sandstone (1801). See San Angel.o formation. Clear Fork Group Choza Fonnation Merkel dolomite, Wrather, 1917; Merkel, Taylor County; near top of Clear Fork group; (1801, p. 97). Wichita conglomerate, Case, 1907; (207). The Geology of Texas-Paleozoic Systems 169 Vale Formation Bullwagon dolomite, Wrather, 1917; Bullwagon Creek, Taylor County; at top of the Vale formation, about 3n. Arroyo Formation Standpipe limest1>ne, Cheney, 1929; top of Stand pipe hill, Abilene, Taylor County; t1>p of the Arroy1> formation; (247, p. 27). Lytle limestone, Ll1>yd and Thomps1>n, 1929; near Abilene, Taylor County; (1001, p. 949) . Rainy limestone, Cheney, 1929; Rainy Creek, 6 miles east GÍ Abilene, Taylor County; (247, p. 26). Wichita Group Lueders F1>rmation Lake Kemp limestone, Garrett, Lloyd and Laskey, 1930; east end of Lake Kemp, Baylor County; top of Lueders formation; (1853, Baylor County). Maybelle limestone, Romer, 1928; east of Lake Kemp, Baylor County; (1351, p. 74). Paint Rock beds, Drake, 1893; Paint Rock, Concho County; basal pan of Lueders formation as defined in the present puhlication; ( 499) • Qyde Formation Talpa limestone, Drake, 1893; Talpa, Coleman County; top of Qyde for. mation; ( 449) . Grape Creek shale and limestone, Drake, 1893; lower pan of Qyde forma· tion; ( 449). Fulda sandstone, Case, 1907; Fulda, Baylor County; (207). Belle Plains Formation Bluff Bone hed, Udden, 1912; Bluff Creek, south of Electra, Wichita County; upper pan of the Wichita group; (1632, p. 36). Beaverburk limestone, Udden, 1912; Beaver Creek, Wichita County; upper part of Wichita group; (1632, p. 31). Bead Mountain limestone, Drake,. 1893; top of Belle Plains formation in Colorado River valley; ( 449) • Valera shale, Drake, 1893; (449). Jagger Bend limestone, Drake, 1893; Jagger Bend, Colorado River; ( 449) • Admira! Formation Elm Creek limestone, Drake, 1893; top of Admiral formation; (449). Coleman limestone and shale, Drake, 1893; Coleman County; ( 449) • lndian Creek limestone, Drake, 1893; name preoccupied, see under Strawn; (449). Hordes Creek limestone, Drake, 1893; (449). Lost Creek shale, Drake, 1893; (449). Putnam Formation Coleman Junction limestone, Drake, 1893; ( 449) • Santa Anna Branch beds, Drake, 1893; (449). Pumam limestone, 1929; namé preoccupied by Putnam formation; (1853, map of Shackelford County). Putnam sandstone, 1929; name preoccupied by Putnam formation; (1853, map of Shackelford County). Moran Formation Sedwick limestone, Bradish and Fisher, 1929; Stephens County; (1853). Santa Anna shale, Drake, 1893; (449). Horse Creek limestone, Drake, 1893; preoccupied, see under Strawn; (449). Dothan limestone, Plummer, 1919; near Dothan, Eastland County; (1227, p. 14.5). Watts Creek shale, Drake, 1893; (449). WICHITA GROUP Cummins in 1890 established the Wichita beds which represent the lowest division of the Permian in the Wichita region of north Texas (340, p. 187). In the same publication Dumble described briefly the Coleman·Albany group, said to overlie the Cisco and to represent the latest series of the Coal Measures ( 458, p. lxvii). This group, with the name abbreviated to Albany division but still retained in the Coal Measures, was more fully described by Cum· mins in 1891 (342, p. 375). Cummins at that time regarded the Albany heds south of the Brazos River as wedging in between the Cisco and Wichita groups and recording an erosion interval between the Cisco and Wichita north of the Brazos (342, pp. 397, 401). In 1892 Jules Marcou expressed the view that the Albany was Permian (1048, p. 369). In a manuscript prepared probably in 1893 for the Fifth Annual Report of the Texas Geological Survey, hut not published, Cummins recognized the Albany as a part of the P~rmian representing the southward extension of the Wichita group under The Geology of Texas-Paleozoic Systems 171 changed facies. 61 A paper citing Marcou's opinion and verifying the equivalency of the Wichita and Albany was published by Cum· mins in 1897 (349). The term Wichita group, as here used, is equivalent to the Wichita-Albany of Cummins. A very remarkable reptilian fauna has been obtained from the Wichita and Clear Fork. The vertebrate fossils of the Wichita group in the red bed facies are listed, and localities discussed, by Romer (1351). The invertebrates of the normal marine facies in· elude a large fauna. A list of species from the Admiral formation is given by Plummer and Moore (1228, p. 194), and the common species of the overlying formation are mentioned by Beede in his section on the Colorado River (87). The plants of this group have been listed by White {610). The Wichita group is apparently conformable both with the under· lying Pennsylvanian and the overlying Clear Fork. No pronounced unconformities have been found within the group. For reasons already given, the Pennsylvanian-Permian contact is here placed at the base of the Moran formation and this formation, together with the overlying Putnam formation, is therefore transferred to the Wichita group. The Wichita group has been variously subdivided. In this pub· lication six formations are recognized, as follows: Moran, Putnam, Admiral, Belle Plains, Clyde, and Lueders, each consisting of sev· eral members. These formations occupy a belt extending from the Red River in a south-southwesterly direction to the Cretaceous overlap south of the Colorado River, through Montague, Clay, Wichita, Archer, Baylor, Young, Throckmorton, Haskell, Shackel­ford, Jones, Callaban, Taylor, Coleman, Runnels, and Concho counties. The contact of the Wichita group with the Clear Fork at the top of the Lueders formation has been followed from the Colorado River into Wilbarger County. On the Red River this contact is difficult to determine but is probably near the Wichita-Wilbarger county line. The group as thus defined is 1500 or 1600 feet thick. :MORAN FOR:MATION The members of the Moran formation recognized by Plummer and Moore are as follows: in the Colorado River valley, Watts C'l.This manuecript has been depoaited by C. L. Baker in the Bureau of Economic Geology. Creek shale, Horse Creek lirnestone, Santa Anna shale, and Sedwick lirnestone;* in the Brazos River valley, sandy shale, Dothan lime· stone, shale with sandstone, and Sedwick lirnestone. Recently Hen­derson has shown that the fusulinid Schwagerina is present in this forrnation. Because of the presence of this fossil the Pennsylvanian­Perrnian contact is here drawn at the base of the Moran formation, and the Moran and Putnarn forrnations are transferred to the Wichita group of the Perrnian. The Pennsylvanian-Perrnian contact may lie in the Harpersville forrnation, as proposed by Roth (1353b). However, the evidence for placing it lower than the Moran forma­tion is not at present conclusive. Type locality: The type locality of this forrnation is at Moran in Shackelford County; thickness in the Colorado River valley, 200 feet, and in the Brazos River valley, 350 feet. The forrnation was narned by Plummer (1227, p. 143). PUTNAM FORMATION The Putnam formation, as originally defined, consisted of a shale with sorne sandstone overlain by a lirnestone. Two mernbers were recognized, the Santa Anna Branch shale and the Coleman Junction lirnestone. In the Colorado River valley the limestone forms a prominent escarpment but thins and disappears to the north. The Coleman Junction lirnestone at the top of the forrnation, followed northward into Archer County, grades into sandstone. Its ap· proxirnate horizon, however, has been followed through Archer County and for sorne miles into Clay County. Type locality; The type locality is at Putnam; Callahan County; thickness in the Colorado River valley, 140 feet, and in the Brazos River valley, 190 feet. The forrnation was named by Plumnier and Moore in 1921 (1228, p. 183). ADMffiAL FORMATION The Admira! forrnation consists of a series of shales with some lirnestones, and, at the top, a limestone, the Elm Creek, from 20 to 50 feet thick. The escarprnent formed by the limestone is prom· inent from the Colorado River north through.Throckmorton County. Farther to the north, however, the limestones grade into shales. •The Dothan limestone is also present under the Horae Creek limestone in Coleman County. The Geology of Texas-Paloozoic Systems 173 In the Colorado River valley, Drake recognized the following mem­bers now placed in this formation: Lost Creek shale, Hordes Creek limestone, Indian Creek shale, limestone and marly clay, Coleman limestone and shale, and Elm Creek limestone. The Indian Creek shale contains an abundant ammonoid fauna of the Perrinites bosei zone. The term ·Indian Creek, however, is preoccupied, having been previously applied by Drake to a member in the Strawn. Type locality: Admira! in Callaban County; thickness, 300 to 350 feet. The formation was named by Plummer and Moore (1228, p. 192). BELLE PLAINS FORMATION The Belle Plains formation consists of shale, calcareous marl, and limestone. Thin limestones occur locally throughout the for­mation, and at the top there are somewhat heavier limestones, the Bead Mountain and the Beaverburk. These limestones, particularly the top ones, make small escarpments. From the Colorado River the Bead Mountain limestone may be followed north through Throckmorton and Baylor counties, beyond which it grades into the red beds section of the Wichita region. The Beaverburk limestone, named by Udden and Phillips (1632, p. 31), has been traced north to Burk in Wichita County. From near the top of this formation, at the old military crossing on the Wichita River in Baylor County, Cummins in 1889 obtained a collection of fossils from which C. A. White described four species of ammonites. In the Colorado River valley the formation includes the follow­ing beds named by Drake: shale, Jagger Bend limestone, Valera shale, and Bead Mountain limestone. Beede, however, from the fossils, favors associating the lower members of this formation up to and including the Jagger Bend with the Elm Creek memher of the Admira! formation (1228, p. 198). Type locality: Belle Plains in Callaban County; thickness, 200 to 300 feet. The formation was named by Plummer and Moore (1228, p. 195). CLYDE FORMATION The Clyde formation includes shales, marly beds, and buff lime­stones. In the Colorado River valley it was defined as including memhers as follows: shale, Grape Creek shale and limestone, and Talpa limestone. Type locality: Clyde in Callahan County; thickness, 200 to 475 feet. The formation was named by Plummer and Moore (1228, p. 197). LUEDERS FORMATION The Lueders, here regarded as the top formation of the Wichita group, consists of limestones and shales. The limestone of this formation is quarried at Ballinger, Runnels County, and at Lueders, Jones County. The Maybelle and Lake Kemp limestones are members of this formation. The limestones are relatively fossiliferous, large bivalves being abundant at Ballinger. The limestones of this for· mation can be followed north into Wilbarger County, beyond which the formation grades into the red bed facies of the Red River region. With the Lueders formation is here included on the Colorado River the Paint Rock bed of Drake. Type locality: Lueders in Jones County; thickness, 65 to 275 feet. The formation was named in 1917 by Wrather ( 1801, p. 94). CLEAR FORK GROUP The Clear Fork group was named by Cummins in 1890 (340, p. 188), and was more fully defined in 1891 (342, p. 401), at which time the contact between the Albany ( then regarded as of Coal Measures age) and the Clear Fork was placed by Cummins as ap· proximately at the divide between the Clear Fork of the Brazos and its tributary, California Creek. * Thus placed, the uppermost lime­stone of the Albany is at the top of the Lueders formation (1853, Shackelford County) and is now known as the Lake Kemp lime· stone ( 1853, Throckmorton County) . The Clear F ork is 1200 or 1500 feet thick and as now subdivided includes the Arroyo, Vale, and Choza formations. The vertebrate fossils of the Clear Fork group in north Texas are listed by Romer (1351). Sorne plants have been obtained which are listed by White ( 610). Only a small marine invertebrate fauna is known from this group (87 and 92). Underground to the west the Clear Fork equivalent probably lies next above the "Big Lime" of the Panhandle section and includes the so-called "Red Cave" and a part of the salt beds of that section *Cummins (342), map following p. 552. The Geology of Texas-Paleozoic Systems 175 (1764, p. 1007). In the southern part of the Permian basin the equivalent of this group, according to present interpretations, is within the black shale series below the "Big Lime" of the Reagan County section. The Clear Fork group is conformable with the underlying Wichita but is separated by an erosional unconformity from the overlying Double Mountain. No unconformities are known to occur within the group. As the formations dip westward, their outcropping mar­gins form narrow belts trending approximately north-south. The width of the several formation belts is, of course, proportional to the thickness of the formations. The group as a whole occupies an outcrop zone 30 to 35 miles wide, from the Red River southwest­ward through Wilbarger, Foard, Baylor, Knox, Haskell, Jones, Tay­lor, Runnels, and Tom Green counties to the Cretaceous overlap. ARROYO FORMATION The Arroyo formation consists of shales, limestones, marls, and gypsum. At the type locality the limestones are thin, usually 1 to 3 feet, the greater part of the formation being shale. In Runnels County there is one persistent gypsum bed in the lower part of the formation. Of severa} thin limestones three have been named as members, the Rainey, Lytle, and Standpipe limestones. The type locality of each is in Taylor County. This formation, which was tentatively placed by Beede at the top of the Wichita group, is here considered as the basal formation of the Clear F ork, which recent county mapping seems to show more nearly conforms with the original limits of that group as defined by Cummins. A few invertebrate fossils are found in Runnels County in the limestones of this formation. Ammonites have been obtained from the Lytle limestone near the top of this formation 1 mile east of Abi­lene, representing the Perrinites k~mpae zone (1234f). Type locality: Los Arroyos, near Ballinger, in Runnels County; thickness, 260 feet. The formation name was given in 1918 by Beede (87, p. 45), replacing the preoccupied name Abilene pre­viously proposed by Wrather (1801). VALE FORMATION The V ale formation as originally defined consists of shale and sandy shale and sorne sandstone. The original definition is here modified by including in this formation a thin overlying dolomite member named by Wrather the Bullwagon dolomite (1801). In Taylor County this dolomite is 5 feet thick and consists of two strata separated by a clay parting. On the Colorado River an ap­parently equivalent member consisting of thin dolomites and shales is 36 feet thick. In Tom Green County it is 44 feet thick, of which more than half,_ about 25 feet, is dolomite ( 704, p. 15). A few fossils, chiefly hivalves, are found in the dolomite. Thickening of the dolomite memher is accompanied by thinning of the underlying shale, which is ahout 340 feet thick in Taylor County, 154 feet in Runnels County, and 50 feet in Tom Green County. Type locality: Vale post office (now ahandoned) on the Ballinger­Maverick road at the east side of Valley Creek, Runnels County; thickness, 100 to 340 feet. The formation was named by Beede (87, p. 47), replacing the preoccupied name Tye previously pro­posed by Wrather (1801). CHOZA FORll!ATION The Choza formation consists of red shales with sorne thin dolo­mites. The most persistent of the dolomites is the Merkel memher named by Wrather (1801). The other dolomites give place north­ward to shales. On the Colorado River the Merkel dolomite is within ahout 270 feet of the top of the formation. In Taylor County this interval. overlying the dolomite has been reduced to ahout 25 feet, and in Stonewall County the Merkel member is either cut out by the erosiona! unconformity which separates this forma­tion from that next above, or, like other dolomites of this forma­tion, terminales northward by lithologic change ( 1185, p. 17) • Ammonites have been obtained from about 167 feet above the hase of this formation on the Colorado River. Type locality: Choza Mountain near Tennyson, Coke County; thickness, 870 feet. The formation was named by Beede (87, p. 49). The Geology of Texas-Paleozoic Systems 177 DOUBLE MOUNTAIN GROUP The Double Mountain group, as established in 1890 by Cummins (340, p. 188), is the uppermost group of the Permian of the north­central Texas region. This group is separated from the underlying Clear Fork by a pronounced erosiona! unconformity. The sedi­ments are largely sands, sandstone, shale, and gypsum. Much diffi­culty has been found in making suitable subdivisions in this group, and the formations now recognized are provisional and will doubt­less be in part modified or added to. It has been found possible to apply formation names used in Oklahoma to sorne extent but not fully. The total thickness of the Double Mountain group is from 1500 to 2000 feet. The formations of this group recognized in Stonewall County, Texas, are: San Angelo, Blaine, and Peacock. An alternate subdi­vision of the group in Texas recognizes the following formations: San Angelo, Blaine, Whitehorse, Cloud Chief, and Quartermaster (1001). The term Royston formation was applied by Cheney in 1929 to about 100 feet of shale, gypsum, and thin dolomite exposed at Royston in Fisher County. This unit is probably the basal part of the Peacock formation as defined by Patton and is probably chiefly within the Whitehorse as mapped by Lloyd and Thompson (247, p. 26). The outcropping belt of this group is broad at the north, ex­tending from a few miles west of Vernon in Wilbarger County, where the San Angelo formation crosses the Red River, to Potter County in the Panhandle region. In its southward extension the outcropping belt narrows by the eastward extension of the High Plains and the Triassic formations and is terminated at the south in Tom Green County by the overlap of the Cretaceous. Relatively few fossils have been obtained from the Double Moun­tain group. Sorne ammonites have been found in the Blaine for­mation in Stonewall and Hardeman counties. The Whitehorse for­mation has yielded fossils in Oklahoma and Texas described by Beede (85). The Double Mountain group extends to the west underground across the Panhandle region. The formations and horizons recog­nized are the "Big Lime" (Wichita), "Red Cave," and "Salt Series" (Clear Fork plus San Angelo and prohahly Chickasha), Blaine, Whitehorse-Cloud Chief, and Quartermaster. Of these formations the Cloud Chief and Quartermaster outcrop at the surface as far west as Potter County (1764, p. 1005). To the southwest under­ground in the Permian hasin, the Blaine formation is thought to grade into limestones. SAN ANGELO FORMATION The San Angelo formation consists of chert conglomerate, sand­stones, and sorne shales. The conglomerate is best developed in the region of San Angelo and on the Colorado River. Northward the conglomerate gives place to finer materials. Sands and sand­stones, however, persist as an important part of the formation to the Red River, as well as in the equivalent of this formation, the Duncan of Oklahoma and the possibly equivalent upper Harper of Kansas. According to Beede, the southern part of the formation as ex­posed in Texas constitutes a large delta, centering near Tennyson in Coke County. From this locality the formation is less con­glomeratic, not only along the strike north and south, hut also down the dip west or northwest. The siliceous conglomerate phase reaches to the southern part of Stonewall County and is succeeded farther north in this county by a conglomerate dolomite and other similar rock fragments (1185, p. 21). Type locality: San Angelo in Tom Green County; thickness, 60 to 250 feet. The formation was named in 1891 by Lersch (984, p. 77). BLAINE FORMA'.J:ION The Blaine formation, as the term is now used in Texas, includes more than does the Blaine of the type locality in Oklahoma. N ot only is the underlying Chickasha, or a part of it, merged with the Blaine in Texas usage, hut the overlying Dog Cre~k of Oklahoma is induded in part or entirely. The formation as thus defined consists of red and gray shales, massive gypsum, dolomite, and sorne sandstone. The gypsum beds are lenticular and range in thickness from a few inches to as much as 30 feet. The dolomite beds in sorne localíties contain poorly The Geology of Texas-Paleozoic Systems 179 preserved bivalves. The following dolomite horizons in this for­mation have received names: Mangum, Acme, Guthrie, and Childress (1001, p. 951). The Guthrie is possibly the same as the Aspermont named by Morley in 1929. The Blaine outcrops in a belt which narrows from about 40 miles on the Red River to 15 miles or less at Sweetwater. An ammonite fauna has been obtained from the Acme dolomite member near Acme in Hardeman County (see p. 181). Type locality: Blaine County, Oklahoma; thickness, 550 to 900 feet. The formation was named in 1902 by Gould and more fully described by him in Oklahoma in 1924 (618, p. 331). lt was re­defined, as here used, in 1929 by Lloyd and Thompson (1001, p. 950). WHITEHORSE-CLOUD CHIEF-QUARTERHASTER FORMATIONS The difficulty of making exact correlation with the formations recognized in the Upper Permian of Oklahoma led Patton in 1930 to propose a new name, Peacock formation, for all that part of the Permian above the Blaine exposed in Stonewall County, Texas. These sediments as here exposed, 700 or 750 feet in thickness, con­sist of thin beds of dolomite, red shales, thin gypsum beds, and fine-grained sandstone. The amount of sandstone increases towards the top of the formation. At the base of the formation is a gypsum bed named the Swenson member by Patton; about 100 feet above the base is the Oriana gypsum member ( 1185) . An ammonite fauna has been obtained from this formation at the falls on Salt Croton Creek, Stonewall County (see p. 181). In 1929 Lloyd and Thompson recognized in Texas the Whitehorse­Cloud Chief and Quartermaster formations of Oklahoma (1001), representing approximately the equivalent of the Peacock formation as later proposed by Patton. To the Whitehorse is referred, on the Red River, red friable sandstone, sandy shale, and sorne gypsum. The Whitehorse-Cloud Chief as thus defined outcrops in north Texas from Chillicothe almost to the west line of Hall County, ahout 40 miles, and narrows southward. The Whitehorse is recognized west of Aspermont in Stonewall County and south of Sweetwater (Lake Trammel sandstone of Wrather). The overlying heavy gypsum heds are regarded as occurring within the Cloud Chief equivalent. The Eskota gypsum, Dozier sandstone, and Claytonville62 dol­omite are memhers in the Whitehorse-Cloud Chief interval. The Qu¡utennaster formation in Texas, · according to these authors, is from 200 to 300 feet thick and consists of well bedded red sands and sandy and gypsiferous shales. It is traced southward to Kent County (1001, p. 953), beyond which it is overlapped and concealed by the Triassic. Type locality: The type locality of the Peacock formation is at Peacock in Stonewall County. The type localities of the Whitehorse, Cloud Chief, and Quartermaster formations are in Oklahoma. UNDERGROUND POSITION OF THE PERMIAN IN TEXAS The highly diversified character of the Permian sediments and the remarkably rapid lateral change of facies has made the tracing of the formations underground unusually difficult. As has been indi­cated, the Permian outcrops at both the west and east sides of the Permian basin. In the basin it is covered by Triassic, Cretaceous, and Cenozoic formations. The problem of correlating across the basin has been attacked by following formations from either side towards the middle of the basin and thus obtaining correlations across the basin, supplementing correlations made directly from fossils obtained from the surface exposures. A large number of geologists have contributed toward making these correlations, and the results, although not yet complete, nevertheless record an im­portant advance in a difficult undertaking. 63 The first correlations of formations on the opposite sides of the basin were made by the aid of fossils from the surface exposures. Ammonites have been ohtained from several localities in the Wichita g1oup of Iiorth·central Texas. From 4 miles svuth of Dundee, Archer County, in the Belle Plains formation, Wrather obtained Parale­goceras baylorense, Perrinites cumminsi, Stacheoceras walcotti, and Medlicottia copei. Bi:ise was of the opinion that these were approxi­mately of Hess age (131). However, King (940), on the basis of «lTbe term Sweetwater applied to this dolomite has been found to be preoccupied (247, p. 26). A small colleetion of invertebrates, obtained from the Dozier (Memphis) eandatone, ia Usted by Gould (614b, p. 23) . 83Publications listed in the accompanying bibliography relating to the underground poeition of the Permian in Texas include the followiog : Ackers, 1; Baker, 51; Bauer, 78; Bybee, Boehma, Butcher, Hemphill, aod Green, 190a; Cartwright, 201; Edwards, 517; Gould and Willia, 625; Hoote, 841; Lang, 975; Sellards and Patton, 1414; Sellards and Williama, 1421; Sellarda, Bybee. and Hemphill, 1428; Willio, 1764, The Geology of Texas-Paleozoic Systems 181 more complete fossil collections from the Glass Mountains, regards them as probahly of upper Wolfcamp age. The vertebrates and plants found in the Wichita are not directly comparable since neither has been obtained from the W olfcamp. From the Clear Fork group in Runnels County on the Colorado River, 3 miles east of the west county line, Beede obtained a few fossils from the Bullwagon dolomite member of the Vale formation. Aside from sorne pelecypods and gastropods, the fossils from this locality are Perrinites n. sp., Medlicottia n. sp. (aff. M. orbinyana Vern.), and Gastrioceras n. sp. These few fossils a:fford no very definite correlation with the Glass Mountains section. In the Blaine formation of the Double Mountain group ammonites have been obtained at the falls of the Salt Croton Creek in Stonewall County, where the following were obtained: Perrinites hilli, Stache­oceras sp., and M edlicottia sp.* Sorne ammonites have been obtained also from the Mangum dolomite member of the Blaine formation from near Quanah in Hardeman County. From this locality Bose lists Perrinites and Gastrioceras. These fossils, particularly Perri­nites gouldi Plummer (MS.), which is very el ose to P. vidriensis, are believed to indicate that the Leonard is of Blaine age. In 1910 and again in 1926, on evidence furnished by invertehrate fossils, Beede suggested that the Queen sand in the Captain forma· tion correlates with the Whitehorse formation (86 and 96). In tracing formations by means of well records it has been neces­sary to rely largely on lithologic characters since index fossils are even more rarely found than on the surface exposures. Eastward from the Guadalupe Mountains the Bone Springs memher of the Leonard formation quickly drops in the Delaware basin below the depth of drilling. The Capitan formation, as previously stated, grades eastward into the Frijole limestone member and into sands, and in the Delaware basin is not separable from the Delaware Mountain formation. These two formations, constituting the Guada­lupe Mountain group, consisting of fine sands and sorne dark lime­stones, are readily traced eastward across the Delaware basin. At the margin of the Central Platform, east of the Delaware basin, conditions with respect to these formations become ohscure. Cart· wright maintains that the Capitan equivalent again assumes a reef *These fonila are from the Guthrie (Aapermont) dolomite near the top of the Blaine for· mation. facies at the west margin of the Central Platform and changes eastward on this platform to a lagoonal facies. East of the platform in the main Permian hasin, the Delaware Mountain · formation consists of anhydrite, salt, and red heds, and is thought to tie in at eastern exposures with the Whitehorse formation (201). The Castile gypsum, which at the surface is 800 or 1000 feet thick, increases in the Delaware hasin to 4000 feet and is divisible into two units, lower and upper., The lower Castile prob­ably pinches out against the Central Platform, while the upper member apparently passes across this harrier and includes the principal salt beds in the main Permian basin. The exact equivalency of the upper Castile on the eastern side of the hasin is in douht, hut it is possibly either Quartermaster or Cloud Chief. The Rustler formation at the top of the Permian of the Delaware Mountains may he traced eastward with no important change, other than thinning,. as far as Winkler County and possihly Midland County, where it is lost, being there possibly within or below the Quartermaster forma· tion. A section across the southern part of the Permian hasin is gi~en in Figure 12. For a detailed section on large scale see Bybee, Hemphill, and Boehms ( 190b). This interpretation of equivalencies across the hasin is supported by the observations of Bybee and associates, who have followed a horizon considered to be the Queen sand zone from two wells in New Mexico in a southeasterly direction to Crockett County, Tex11;s. The Queen sand, which is the equivalent of a part of the Capitan, and, according to these writers, the same as the Y ates sand of the Y ates field in Pecas County, is placed near the top of the Delaware Moun­tain formation ("Delaware sands"), which in turn is regarded as a part of the Whitehorse of the eastern section (190a). This correla: tion agrees with that made by Beede from surface exposures in 1910 and 1926 (86 and 96). Underneath the "Big Lime" in the southern part of the Permian basin is a great series of hlack shales and limestones. These have been drilled through near the center of the hasin in Reagan County where they are 4200 feet or more thick. The genus Schwagerina is found in these shales and limestones within ahout 500 feet of the base. The presence of this fossil and associated Fusulina species indicates that 3700 feet or more of this hlack shale is Permian (1428, 1 CULBERSON ca~. REEVES CO. / "'-. /// 2 "-. 1 1 REAGAN CO. IRION CO. 1 1 ' UPTON CQ l5CH..EIC!-ER & TOM GREEN COS. j MENARO CO. 1 /' 5 6 OUAT· 1E:NARY 1 / J----t-::::i"-21 I / 22 JuiE 23 o , ~ \ \ SEA \ º«~,,., \ '11>~ ........... 1/,,/'v~~ ',, "'.1;¡, , .<&-~ ~-V~', S~', ~Gs°", ' / 2000 !;O()' 1000' 500' 5 10 IS a:I ZS l) J5 <10 'º ,,,/"" / ~"'· ~~ / /// / ,/ /// /// // ....vr __ ,,..,,," / -.:-!....;}~ / el formation. Name and Jocation of well TD Elev Miss Ord Camb p-Camb Vestal 1, New South Oil Assn.; J. Dyson Surv.; l 1h mi. E, 1112 N Cross Plains ____ --·--3755 1786 3735 Windharri 1, Mid-Tex Oil and Gas Co.; Geo. Hancock Surv., Sec. 370; 3 mi. NE of Olpin__ _ 4438 1859 4232 • • CARSON COUNTY The formations in Carson County overlying those here recorded are of Cenozoic, Triassic, and Permian age. In the wells here recorded in this and other counties in the Panhandle region the intervening systems from Pennsyl­vanian to Cambrian inclusive are absent. These wells, however, are located on the Amarillo uplift. Off of this uplift and at its sides Pennsylvanian and possibly older formations are present. Name and Jocation of well TD Elev Miss Ord Camb p-Camb Lane 1, Empire Gas and Fuel Co.; l.&G.N.Ry.Co. Surv., Bl. 4, Sec. 72 ; 6 mi. from N, 8 from E county line__ ____________ 2980 3188 Abst · Abst Abst 2550 McConnell 1, Tipton and Wag­ goner Refi ning Co.; l.&G.N.Ry. Co. Surv., Bl. 3, Sec. 201 ; 2 mi. from E, 9 from N county line. 3084 3302 Abst Abst Abst 2685 T hompson 1, Shamrock Oil Co. ; l.&G.N.Ry. Surv., Bl. 7, Sec. 15; 10 mi. from E, 14 from N county line ---------­--­-----------­------­ 3404 3383 Abst Abst Abst 3045 CLAY COUNTY The formations in Clay County overlying those here recorded are of Lower Permian and Upper Pennsylvanian age. In the one well that has penetrated to the pre-Cambrian the Lower Pennsylvanian and Mississippian and probably Ordovician are absent. This well, however, is located on the Red River uplift and the absence of the Lower Pennsylvanian, Mississippian, and Ordovician is probably due to erosion in post-Lower Pennsylvanian time and previous to the deposition of the oldest Upper Pennsylvanian (Cisco or Canyon) present at this locality. Name and location of well TD Elev Miss Ord Camb p-Camb Byers 41, The Texas Co.; Gaston Surv., Bl. 19, Byers Subd.; 2112 mi. E Petrolia ----------------------------4289 978 Abst Abst 3440 4240 COLEMAN COUNTY The formations in Coleman County overlying those here recorded are of Permian and Upper and Lower Pennsylvanian age. Cretaceous deposits persist locally as outliers. Permian is present in the western half of the county. Name a nd location of well TD Elev Miss Ord Camb p-Camb Adams 1, Arizona Oil Co.; A. Wickson Surv. 168; 2 mi. NW Burkett --------------------------------·-3511 1581 3320 3425 • • Burke 1, Pippin Oil Co.; A. Wil­liams Surv. 655 ; 4 mi. E San­ta Anna --------------------------------2679 1596 2575 2664 • • The Geology of Texas-Paleozoic Systems 199 Name and Iocation of well TD Busch 1, Roberts et al; H.E.&W. T.Ry.Co. Surv.; %, mi. SE Whon -------------------------------------1635 Campbell 2, Gladys Bell Oil Co.; H.T.&B.Ry.Co. Surv., Bl. 2, Sec. 60; 1 mi. S, 2% E Santa Anna ----------------------------------------2750 Cox 1, Halbert-Neeley et al; M. Dirks Surv. 203; 25 mi. S, 4 W Coleman ---------------------------------2490 Dibrell 2, Thomas et al and Sims; H.T.&B.Ry.Co. Surv. 16; l % mi. NE Camp Colorado ____ 3500 Dibrell 1, Wise Oil Corp.; H. Kigan _Surv. 498; l % mi. SE Camp Colorado ,-----------------------2920 Featherstone, Manhattan Oil Co. ; G.H.&H.Ry.Co. Surv., Bl. 2, Sec. 52; 4 mi. from N, 8% from W county line --------------4331 Floyd 1, Humphrey and Dozier ; Coleman County School Lands, Bl. 90, Sec. 23; 2 mi. E Rock-wood -----------------------------------1845 Goodgion 1, Andrew Urban; E. Williams Surv., Bl. 2; 2 mi. N Trickham -----------------------------2160 Guthrie 1, Producers Oil Co.; Bonds and Sanders Surv. 78; l % mi. S, 1h W Trickham ____ 1975 Gut.hriP. 1, The Sun Co.; H.E.& W.T.Ry.Co. Surv. 112; 7 mi. S, 3 W Trickham _----------------_ 2267 Halbert 1, Milham Corp.; S. J. Martin Surv. 162; 2% mi. E Camp Colorado ____________________ __ 3025 Harris 1, Slick Oil Co.; H. Starnes Surv. 63; 2% mi. S, l % E Santa Anna ------------------3264 Hubbard 1 (Ray Copeland) ; Capital City Oil Co.; W. Coale Surv. 718; 3% mi. NE Coleman 3604 Jennings 4, Derby Oil Co.; A. S. Lipscomb Surv. 94; 5 mi. N Trickam _ 2435 Johnson 1, T. B. Slick and Sny­der Oil Co.; H.T.&B.Ry.Co. Surv. 21; 3%, mi. NE Camp Colorado --------------------------------3310 MilJer 1, Moutray Oil Co.; W. C. Perry Surv.; 4, mi. N, 9 W Goldbusk __ ___ ______ __ 3627 Miller 1, Syndicate Oil Corp.; Fort Bend County Sch o o 1 Lands Surv., Sec. 37 ; 4 mi. from W, 3 from S county line _ 3075 Elev Miss Ord 1411 1618 1643 2724 1515 2190 1580 3040 3114 1482 2800 2900 1940 4209 4220 1432 1756 1805 1435 1918 2010 1392 1698 1780 1492 1803 1860 1550 2910 2985 1583 2540 2605 1683 3290 3407 1506 2100 2165 1649A 3130 3227 1687 3355 1562 2885 Camb p-Camb • • • * * * • * * • * * * * • * • * Name and location of well TD Elev Miss Miller 1, Tidal Oil Co. (Sys­ tem); Fort Bend County School Lands Surv., Subd. 8-A; 4 mi. SE Leaday ____ ________________ 3175 1565 Morris 4, Eastland Oil Co.; Wm. Webber Surv. 772; 6 mi. E Coleman (in Eastland pool) ____ 3318 1595 3212 Morris 1, Independent-Phillips et al; T. J. Frizell Surv. ; 4 mi. NW Coleman -------------------­3685 1780 3520 Morris 2, Midwest Exploration Co.; A. Newschaffer Surv., BL 750; 8 mi. Coleman ____________ 3667 1622 3430 Morris 3, Magnolia Petroleum Co. and Elizabeth Oil Co.; David Breeding Surv.; 9 mi. N, 2 E Coleman ­-------­----·------­--­ 3438 1582 3350 Morris 4, Magnolia Petroleum Co. and Elizabeth Oil Co.; David Breeding Surv.; 9% mi. N, 2 E Coleman ---------------------­ 3978 1583 3270 Morris 5, Magnolia Petroleum Co. and Elizabeth Oil Co.; David Breeding Surv.; 9 mi. N, 2 E Coleman -----------------------­ 3430 1578 3330 Neff 1, Sinclair-Gulf Oil Co.; G. Eubanks Surv. 173; 11 mi. N,7 E Coleman___________ ______________ 3425 1593 3245 O'Hair 1, Root and Ferl ; Casper Simon Surv.; 4 mi. NE Cole­ man -------------------------------­ 3347 1642 3210 Overall 1, Anzac-Continental; G. H.&H.Ry.Co. Surv., BL 1, Sec. 10; 6 mi. S, Z W Coleman _______ 3240 1674 3010 OveralJ 1, Flanigan; W. Woolsey Surv., Sec. 294; 3% mi. S, 2 W Coleman -------­--------------­ 3535 1791 3340 Padgett 1, Sinclair-Gulf Oil Co.; Brazoria County School Lands Surv. 226; 2 mi. from W and S county line ____ -----­-------------------­Pitts 1, Samuels; J. Johnson 3580 1596 Surv., Sec. 5; 3 mi. W Coleman 3503 1790 Richardson 1, Schemel et al; L. F. Pease Surv., Bl. 268; 1 % mi. S Whon __________ ______________ 1659 1410T 1543 Sealy-Hutchins 1, Sinclair -Gulf Oil Co.; G.H.&H.Ry.Co. Surv. 23; 9 mi. N, 2 W Coleman _____ 3920 1882 3795 Sealy and Smith 1, Magnolia Petroleum Co. and Elizabeth Oil Co.; G.H.&H.Ry.Co. Surv., Bl. 2, Sec. 9; 7 mi. N, 1% E Coleman -----­-------------------­ 3610 1714 Sealy-Smith 4, Roth and Farout; G.H.&H.Ry.Co. Surv., Bl. 1, Sec. 19; 11;4 mi. N. Valera ____ 3642 1830 3500 Ord 2830 3245 3595 3580 3432 3417 3418 3325 3285 3145 3456 3445 3480 1583 3885 3530 3570 Camb p -Camb • • • • The Geology of Texas-Paleozoic Systems 201 Name and location of well TD Elev Miss Ord Camb p-Camb Slate 1, Magnolia Petroleum Co. and Elizabeth Oil Co.; J. Kaufman Surv. 237; 20 mi. S, 2 W Coleman ____ 3130 1442 2304 Starr 1, Roth and Farout; Bur-net County School Lands, Bl. 86; 1 mi. W Valera ________________ 4303 1917 3625 • 3680 Wallace 2, Robertson and Son: Wm. Farris Surv. 279; 7 mi. S Santa Anna -----------------------------2612 1541 2408 2533 COMANCHE COUNTY The formations in Comanche County overlying those here recorded are Cretaceous, over most of the county, and Upper and Lower Pennsylvanian. Name and location of well TD Elev Miss Ord Camb p-Camb Armstrong 1, P. L. Tippit; H.T. &B.Ry.Co. Surv. 13; 3 mi. N, 2 E Comanche________________________ 3120 1283 2781 Brittain 1, Simms Oil Co.; B.B. B.&C.Ry.Co. Surv., Sec. 31: l 1h mi. from N, 1h from W county line ---------------------­3590 Bryant 1, Republic Production Co.; Ph mi. from NW, 81h 1620 3280 • from SW county line · __ _ 3360 1492 3325 Bryson 1, Sun Oil Co.; W. C. Sypert Surv.; 3 m1 . W, 1 S Comanche -----------­-------------------­---­ 3136 1520 2580 2725 Calloway 1, Lone Star Gas Co.; H.T.&B.Ry.Co. Surv. 15; 9 mi. S, 41h W Comanche _ 3525 1700T 284.St Caners 1, Hookins; H.&T.C.Ry. Co. Surv., Bl. 2, Sec. 44; 21h mi. from W, 7 from N county line --­--­----------------------------Da vis 1, Sam Da vis Oil Co.; J. 3352 1369 3101 • Walker Surv. ; Comyn Station; 13 mi. from NW, 21h from NE county line Fisher l; Copperas Creek Oil 3525 1250 3300 Co.; D. H. McFadin Surv. 190; 11 mi. N, 3 W Comanche. ____ 3075 1281 3075 • Fisher 1, Ro"xana Petroleum Corp.; 11 mi. D. H. McFadin Surv; , 3 W Comanche ________ 3200 1271 3100 Fisher 1, Tex-Wa Oil Co. ; E. Cooper Surv.; 9 mi. N, 2, W Comanche ------­---­------------------­ 3048 1250 3000 • • Foster 1, Kelsey et al; D.&D. Asylurn Lands Surv., Sec. 54; 1 mi. SE Sipe Springs_________ 3173 1369 2968 Fritz 1, Tulsa Prod. Co. (Max­ well and Ertel ) ; G. L. Addison Surv.; 5 mi. N, 5 E Comanche 3276 1221 3040 3145 • • fFrom driller's log, unsupported by samples. The top of the Ellenburger may be at 2524 feet. Name and location of well TD Goss 1, Humble Oil and Refining Co.; D.&D. Asylum Lands Surv., Sec. 59; 4 mi. W Sipe Springs --------------------------------3275 Goss 1, Sipe Springs; midway between Rising Star and SipeSprings __________________ . _________ 3330 Hamlin 1, Manhattan Oil Co.; D. &D. Asylum Lands Surv. 23; l1h mi. N Duster_____________________ 3238 Hilly 1, Gales Oil Co.; L. Bird­sall Surv. 54; 2 mi. from N, 1% from E county line ____________ 3568 Kay 1, . Henderson et al; J. P. Stevenson Sur v., Bl. 10 ; 5% mi. S, 1h W Desdemona ___________ 3402 Martin 1, Dickerson et al; Was· son Surv.; 3 mi. SW Wilson ___ 4520 Montgomery 1, Maxwell and Ertel; R. Page Surv.; 7% mi. S Comanche --------------------------3500 Poteet 1, Fain et al; D.&D. Asylum Lands Surv., Sec. 45; 4% mi. from W, 1 from N county line ------------------------·--3415 Powers 1, Milham . Corp.; E. Cooper Surv.; 9 mi. N, 3 W Comanche -----------------------------3120 Rasco 1, Hoffer Oil · Corp.; J. Elliott Surv. 237; 3 mi. E, 4 N Sipe Springs_____________________ 3180 Rudd 1, Roxana-Wallace Oil Co.; D.&D. Asylum Lands Surv. 17; on north county line, 10% mi. from NE corner _______ 3111 Scott and Utterback 1, Trojan Oil Co.; Wm. McC!elland Surv.; 1 mi. S of Comyn _----------------···--3553 Small 1, Humble Oil and Refin­ing Co.; D.&D. Asylum Lands Surv., Sec. 38; 2 mi. N, % E Sipe Springs ------------------------------3355 Standaville 1, Chase, Knight and Miller; E. Whitesides Surv. 71; 12 mi. E, 2% S Comanche . 1 3824 Sturkie 1, Comanche Oil Assn.; A. Hoxey Surv. ; 7% mi. E, 3% N Comanche__ ___________________ 3350 Tate 1, Crawford and Flynn; H. &T.C.Ry.Co. Surv., Bl. 2, Sec. 7; 6% mi. W De Leon________________ 3323 Thompson 1, Hoffer Oil Corp.; H.&T.C.Ry.Co. Surv., Bl. 2, Sec. 16; 14 mi. N, 2 W Co· manche ____________________________,_________ 3146 Elev Miss Ord 1532 3120 3262 1490 3330 1402 3150? 1343 3340 1258 3325 1150T 4100 1420 3245 3385· 1276 2995 1369 3075 3175 1300 2985 3075 1398 3520 1482 3286 1160 3776 1151 3335 1369 3190 3301 1397 3030 3144? Camb p-Camb * * • • . * * • The Geology of Texas-Paleozoic Systems 203 Name and location of well TD Elev Miss Ord Camb p-Camb Wasson 1, Dickerson et al; E.T. Ry.Co. Surv., Bl. 3, Sec. 46; 6 mi. NE Gustine....________________ 4520 1230 4150 • • Wiley 1, Humble Oil and Refin­ing Co.; T.&N.0.Ry.Co. Surv., Sec. 3, 2% mi. from NW, 3% from sw county line__________ __ 3420 1571 3205 3353 • • Wilhelm 1, Sun Oil Co.; A. Smith Surv.; 3% mi. s Co­ manche ----------------------------------------3310 1540 3310 CONCHO COUNTY The formations in Concho County overlying those here recorded are Cre­taceous, in the southern part of the county, and Lower Permian and Upper and Lower Pennsylvanian. Although not recognized in the wells here recorded the Barnett fonnation is probably present in this county. Name and location of well TD Elev Miss Ord Camb p-Camb Hartgrove 1, Arkansas Fuel Co.; H.&T.C.Ry.Co. Surv., Sec. 49; 18 mi. N, 8 E Eden_______________ 1669 3080 • Waring 1, Leonard Petroleum Co.; Gideon Pace Surv. 2853; 3 mi. S Eden ________________________________ 3310 2036 3225 COOKE COUNTY The formations in Cooke County overlying those here recorded include Cretaceous and Upper Pennsylvanian. The Lower Pennsylvanian is possibly locally present. Name and location of well TD Elev Miss Ord Camb p-Camb Alexander 1, Thurman and Max­ well; J. Gregg Surv.; on S county line, 71h mi. from E county line -------------------------------2083 663 1972? • Bailey-English 1, Duffy et al (Lesh and McCall) ; E. Faris Surv. 2273; 10 mi. S Muenster 2273. 877 Abst? Abst? Abst? 2273 Ball 1, Benson Bros.; M. Hunt Surv.; 2% mi. N Myra__ _________ 1580 799 1571 • • Belz 1, Camp Drilling Co. ; J. R. Davis Surv., A-334; 14 mi. from S, 13 from E county line 1225 747 ? 1220t Biffle 1, McElreath and Suggett; R. Shannon Surv.; 7 mi. W, 1 S Gainesville --------------------------2202 839 2114 • Brown (Blanton) 1, Skinner and Simms Oil Co.; B. A. Foreman Surv.; 7 mi. S, 8 W Gainesville 1793 949 1785 Campbell l; Atlantic Oil Produc­in o: Co. (Green et al) :B.B.B.& C.Ry.Co. Surv., Sec. 27; 9 mi. W, 2 N Gainesville________________ 1924 904 1924 • • fThe base of the Cretaceous in this well is probably at depth 1060 feet. The Ellenburger is entered at depth 1220 feet. There is, accordingly, only about 160 feet of Pennsylvanian in this welL Mississippian is probably absent or, if present, is included within the 160-foot interval. Name and location of well TD Campbell 1, Faith Oil Co.; O. F. Leverett Surv. ; 9 mi. W, 2 N Gainesville 1924 Campbell 1, Green et al; O. F. Leverett Surv. A.6()7; 10 mi. W, 2 N Gainesville_____ _ _______ 1662 Campbell 1, Tippit and Darnall; D. E. Moss Surv.; iPh mi. N Myra _ 3000 Clayton 1, Humble Oil and Refin­ing C<>. (J. G. Roe); E. Reed Surv.; 3 mi. NE Muenster _ 1644 Cooke 1, McElreath and Suggett; S.P.Ry.Co. Surv. 7; Ph mi. W, 1 S Hood________________ __________ 1890 Dayton 1, Abernathy et al; F. Godley Surv.; 6% mi. S Gainesville ------------------------------2147 Dayt<>n 1, Shasta Oil Co.; Cooke County School Lands, Sec. 26; 10 mi. S, 4 E Gainesville _____ ___ __ 2148 Dennis 1, Shell Petrnleum C<>rp.; T. Hutchinson Surv., A-484; 2 mi. from W county line; Bul­ cher pool _________ _ __ 2043 Dennis 2-A, Kewanee Oil and Gas Co.; J. B. McClyman Surv.; Bulcher Oil Po<>l ______________________ 2526 Donald 1, Gulf Production Co·.; J. Guffey Surv., A-1545; 9 mi. S, 1 W Muenster__ __________ ______________ 3135 Dougherty 1, Benson Bros.; B. Garner Surv.; 10 mi. S, 4 W Gain esville -------------------------_______ 2007 English 1, Duffy et al; Faris Surv., A-387; 8 mi. S Muen­ster ----------------------------------------------2287 Felker 1, Deep Rock-Shell; S. E. Clements Surv., A-2,73; 1 mi. E, 8 S Muenster_________________________ 1633 Fettie 1, Hanbury et al; Camp­bell Surv.; 3 mi . S Muenster.o__ 2032 F1eitman 1-B, Danciger Oil and Refining Co.; L. Mikel Surv., A-747; 4 mi. N, 1h W Muen­ster ---------------------------------------------1680 Gwynn 1, Petr<>leum Producers C<>.; Marshall Univ. Surv., A­619; 1 mi. S. 5 E Muens•er 1875 Hamm<>nd 1, Kewanee Oil and Gas Co.; E.T.Ry.Co. Surv. 3 · 1h mi. from S, 31h from E county line ---------------------------2122 Hires and Seagraves 1, Petroleum lnvestment C<>.; H. Nail Surv.; 2 mi. S Hood -----------------------------1642 Hundt 1, Hedrick Camp Drlg. Co. and Aberna.thy; F. Gadley Surv.; 7 mi. S Gainesville_______ 1915 E lev Miss Ord 899 1667 934 1607 950 1640 927 1550 1055 1859 735 1926 759 2114 830 2038 867 2456 906 Abst? Abst 755 1046 972 Abst? Abst 1016 1621 911 1967 1048 1670 896 1832 859 2119 974 1495? 752 1914 Camb p-Camb Abst 2900 Abst 2275 ' The Geology of Texas-Paleozoic Systems 205 Name and location of well Hyman 6-B, Kewanee Oil and Gas Co.; T. J. Moss Surv.; 11h mi. W Bulcher ........ .. . Jacobs 1, Simms Oil Co.; J. T. Strickland Surv. ; 1h mi. from S, 5 ~ from E countv 1ne Jacobs 2, Hamilton; J. Strickland Surv., A-929; 1h mi. from S, 51h from E county line J ohnson l, United Production Co. ; J. Clark Surv., A-194; 31h mi. N Muenster Jones l, Texas-Pacific Coa] and Oil Co.; l mi. from S, 51h from E county line Luderman 1, Sun Oil Co.; N. R. Sparks Surv., A-1496; 6 mi. N, •. V 1\1uenster Mitchell l, Sowell Eros.; B.B.B. &C.Ry.C<>. Surv., Bl. A, Sec. 147; Ph mi. NW H<>od . Mount l, McElreath and Suggett; S.P.Ry.Co. Surv., Sec. 9; 3* mi. S Bulcher Pierce l, Porter-Holmes; B. Lusk S·irv. · 2 nii. S. • 17 13.,] •'• r 0 Poteet 3, Humble Oil and Re:fin. ing Co.; Stephens Surv.; l 1h mi. from W, 3 from county li~e. Bulcher ponl Poteet 4, Humble O!I and Re:fin­ing Co.; J. L. Stephens Surv.; l 1h mi. from W, 3 from N cou~rv line. BulchP.r ..,001 Purcell 1, Green et al (Deep Rock Oil Co. and Faith Oil Co.) ; C. F. Stanley Surv., A-907 ; 5 mi. frn .-,, W, ~ frn~ N Cfl'l""(V r~~ Shipley l , Hamilton et al ; M. Hunt Surv., A-506; 1h mi. from S, 6 from E county line ··-­ St.ac" l. 1•,,.noli~ P~trnlenm Co. ; J. Clark Surv., BI. 194; 4 mi. T foenster .. . ·-·- Timms 5, Kewanee Oil Co. ; J. L. Stephens Surv., A-1001; l 1h mi. from W, 3 from county line (Bulcher field) Timms 6, Kewanee Oil and Gas Co.; J. L. Stephens Surv., A· 1"01; 1 2 mi. from W, 3 frnm countv line (Bulcher fip}d) Vogal 1, Skinner et al ; J. Trus­sell Surv.; 2 mi. S, l 1h W Muenster ___ _ TD 1466 1635 1490 1770 1582 3334 2392 2095 2225 1542 1525 1524 1678 2010 1459 1466 2350 Elev 847 606 620 950 647 909 993 1152 914 848 838 995 637 1030 85i 856 1030 Miss Ord 1418 1541 1485 1685 1560 2860? 2368 1900? 2108 ? 14678º 1446 1468 1674 1835 1426 1420 2140 Camb p-Camb • • • • SO'fhis and some adjoining wells have produced oil coming wholly or in part from tbe Ellen· burger Jimestone. Name and location of well TD Elev Miss Ord Camb p-Camb- Walker 1, Amerada Petroleum Corp.; A. Dozier Surv.; 2 mi. W, 1h N Gainesville _________________ 2880 738 2665 • • Wells 1, Fain-McGaha; G. w. Jewell Surv.; 1h mi. from S, 13 from w county line ______________ 1644 864 1543 Whaley 1, McE!reath and Sug­ gett; S.A.&M.G.Ry.Co. Surv., A-999: 9 mi. S and 1h E Muen­ ster ------------------------------------------2340 916 Abst? Abst Abst 2312' Yosten 1, Muenster Oil Co.; G. lvy Surv.; 114 mi. NW Muen­ ster --------------------------------------------3790 1059 1997 2468 2750 CORYELL COUNTY The formations in Coryell County overlying those here recorded are of Cr~ tacoous and Upper and Lower Pennsylvanian age. Of the Upper Pennsyl­vanian the Strawn only is represented and of the Cretaceous only the Comanche series is present. N ame and location of well TD Elev Miss Ord Camb p-Camb-Clark 1, Benedum and Trees, Francis Keystone Texa& Oíl Co.; G. W. Carlile Surv.; 9 .. mi. W, 1 N Gatesville --------------3630 870 3465 Gotcher 1, New York Syndicate; W. T. Whitley Surv.; 214 mi. W, 1h S Copperas Cove ________ 3035 1132 3025 Strickland 1, Buckeye Mid-Kan­sas; John Winn Surv.; l 1h mi. S, % W Pitcock. ___________,_______ 3628 946 3615 * • Tienert 1, New York Syndicate; E. Iones Surv.; l1/2 mi. W, 2 N Cop-peras Co-ve___________________ 3384 1094 3384 CROCKETT COUNTY The formations in Crockett County overlying those here described are Cre­taceous, Permian, and Pennsylvanian. Name and location of well TD Elev Miss Ord Camb p-Camb Todd 1, Stanolind Oil and Gas Co.; G.C.&S.F.Ry.Co. Surv., BI. UV, Sec. 67; 8 mi. W, 4 N Ozona ------------------------------------------.8041 2660 Abst 7247t DENTON COUNTY The formations in Denten County overlying those here recorded are of Cretaceous and Upper Pennsylvanian age. In addition the Lower Pennsyl­vanian is present, although probably locally removed by erosion previous to tAbove the Ellenburger is middle Ordovician, Simpson series, which was reached at depth 7006 feet. Resting on the Simpson is a crinoidal limestone of .Pennsy)vanian or Pemian age eimilar in cha rae ter to the crinoidal limes tone of the deep wells in Reagan County. Tke Geology of Texas-Paleozoic Systems 207 the deposition of the Upper Pennsylvanian. Mississippian is possibly present in this county, although not recognized in these wells. Name and location of well TD Elev Miss Ord Camb p -Camb Atkins 1, Rondeau and Sanford; W. Thompson Surv. ; 5 mi. E, 2 S Sanger ······------------------------------2023 631 2020 Hampton, Chapman, Garrett and Moore; J. Chesson Surv.; 3 mi. SE Sanger --------------············-···· 2210 69581 2125 • • Hughes 1, Rondeau et al; J. Mor­ton Surv.; 3 mi. E, 2 N Sanger 1316 665 1297 • • Jacobs 1, J . W. Peel Trust (Lloyd); J. Johnson Surv., A­ 670; 13 mi. N, 4 E Denton ___ 1800 590 1773 • Waide 1, Jenkins and Kelsey and Jones and Eubanks; T. Carpen­ter Surv.; 1 mi. from N, 7 from W county line .......... . .... . ... 1913 797 ? ? 1870 Wright 1, McMalion and Daniels; S. Noling Surv. 4; 2 mi. S, 3 W Sanger .. ......... ________ 2530 666 24-53 Wright 1, McNeill and Black-stock; S. Flint Surv., A-418; 11 mi. E Sanger .... _______ 1640 632 1475 Yeatts 1, The Texas Co. and Ben­son and Benson; W. J. Hen­drix Surv.; 4 mi. N, 5 W Boli­var ------------------------------2026 771 Abst Abst 2013 EASTLAND COUNTY The fonnations in Eastland County overlying those here recorded are Cre­taceous, locall¡y present in tlie southem and eastem ¡parts of the county, and Upper and Lower Pennsylvanian. Name and location of well TD Elev Miss Ord Camb p-Camb Allen 1, Gulf Production Co·.; Wm. Fields Surv.; 4% mi. S, 3% E Ranger 4010 1446 3765? Alsobrook 1, Havermeyer and Seamans; H.&T.C.Ry.Co. Surv. 14; l1/z mi. SW Gorman .........• 3525 1400 3190 • Barber 2, States Oil Corp•.; H.& T.C.Ry.Co. Surv., BI. 4, Sec. 2; 3 mi. N, 2 E Eastland .............. 4505 1542 3960 • • Bames 1, Prairie Oil and Gas Co.; F. P. Barnett Surv. 657, BI. 40; 2 mi. N, 2 W Ranger 4300 1584 4080 • Bourland l, Goodwin et al; W. Van Norman Surv.; 4 mi. S Ranger ----------------------------------3625 1368 3486 3577 • Branford 1, Prafrie Oil and Gas Co.; Rosseau Surv. 25; 5 mi. S, 2% W Eastland _______________ 3955 1479 3717 • • Brashear 1, Farabee; 4 mi. S Ranger ---------------------------------4000 1473 3628 • • 81The Bend is reported in this well at depth 1904 feet. The elevation is also given as 558 feet. Name and Jocation of well Brashear 1, Leon Oíl Co.; Wm. Van Nonnan Surv. ; 5 mi. S, 2 W Ranger_________________ _______ Brashear 2, Leon Oil Co'. ; Wm. Van Nonnan Surv.; 5 mi. S Ranger ---------------------------- Brashear 1, Westheimer et al; Wm. Van Nonnan Surv.; 5% mi. S, 2 W Ranger_________________ Brown 1, Central Oil Develo·p' ment Co.; G. E. Moore Surv.; 1 mi. E, 1h N Desdemon a._ __ _ _ Collins 1, Kokomo-Phillips; H.& T.C.Ry.Co. Surv., Bl. 1, Sec. TD 4000 11; 10 mi. S, 61h E Eastland 3410 Connellee 1, Benedum and Trej'!S; N. Ussury Surv.; 3 mi. S, %, E Eastland Cooke 1, Texas and Pacific Co·al and Oil Co.; W. Cooper Surv.; 3 mi. N Ranger____________________ Davis 1, S. A. Hopkins et al ; H. &T.C.Ry.Co. Surv., Bl. 4, Sec. 54; 7 mi. W, 7 N Cisco -· Duffer 1, Prairie Oil and Gas Co.; S. N. Mathais Surv. ; 1 mi. E, 31h S Ranger --·-_ ·-·-----Dulin 1, O. R. Cup·per (Trans­continental) ; H.&T.C.Ry.Co. Surv., Bl. 4, Sec. 42; 3 mi. W, 2 N Eastland ----··----··---··-----·-· Eppler 1, Connollee and Aguire; Wm. DeMoss Surv.; 3% mi. NE Gorman _ ···----------------·------­Falls 1, Prairie Oil and Gas Co'.; E. Finley Surv.; 31h mi. S, Ph W Ranger --------------------------­Fee 1, Sun Co.; H.&.T.C.Ry.Co. Surv., Bl. 4; 61/2 mi. W ,1 N Ranger ·----------___________________ Fee 1, Texas and Pacific Coa! and Oil Co.; Robertson Coun­ty School Lands; 8 mi. E, l % S Ranger ____ ------------------------­Fields 1, Atlantic Oil Producing Co.; J. Rubarth Surv. 100; 17 mi. S Eas tland __________ Green 1, J. E. Thompson and McMillan; S.P.Ry.Co. Surv., Sec. 4..58; 2 mi. E Leeray_________ _ SIMississippian in the Co1Iins well includes "pink crinoidar• Jimeetone from 3378 to 3380; 3800 4359 5591 3770 3905 3700 4012 3710 3340 4051 Elev Miss 1477 1471 1460 1450T 1449 327882 1541 1546 1449 3833 1446 1500 1356 1441 1538 1240 1504 ?-333582 1493, ?-3990 Ord Camb p-Caml> 3628 • • 3618 • • 3615 • • 3545 • • 3388 . •· 3737? 4187 . .. 3930 4926 5425± 3680 •. 3898 . ·­ 3238 • • 3685 • • 4000 • • 3520 • • 3339 • 3990 • • the Barnett formation from 3278 to 3378 and in the Jones well Bamett is at depth 3698 to 3740 and the "pink crinoidal" from 3740 to 3894; from 3894 to 3935 in tbis well is a detdtal zone which may also be MiasiHippian; in the Sibley well the ºpink c~oida:l" ie at deptb 3495 to 3582 (L. C. Cartwright) ln lb,. F°f>]ds wP11 •he basP nf the Barnett is a.t depth 3335 or ~37 with "pink crinoidal" at 3337 to 3339 (R. E. Gileo). Orbiculoid•a sp., probab)J MU.oiaip· pian in age, waa obtained from the 1onee well at depth 3920. The Geology of Texas-Paleozoic Systems 209 Name and location of well TD Grove 3, Moody Oil Corp.; S.P: Ry.t:o. Surv., Sec. ~3; 51/2 mi. from W, 21h from N county line ------------_____ 4113 Hagaman 1, Lone Star Gas Co.; W. C. & C. Boswell Surv.; l 1h mi. NE Ranger____________________ 3745 Hagaman 1, Sinclair-Gulf; S. Gafford Surv., 2 mi. NE Ran­ger ------------------------------------------4002 Holcomh 1, Cosden Oil Co.; H.& T.C.Ry.C-0. Bl. 4, House Surv.; · 1 mi. NE Eastland ------------------3830 Jones 2, S. A. Hopkins et al; H. &T.C.Ry.Co. Surv., Bl. 4, Sec. 43; 4 mi. W, 1 N Eastland ____ 3935 McClellan 1, Moody .C-Orp.; S.P. Ry.Co. Surv., Sec. 456; 51h mi. W, 71h N Cisco___________ _ _____ _____ 4124 Mann 1, Atlas Oil C-0.; Thos. Mullryne Surv.; 81/a mi. E, 21/a N Carbon ____ -------------------------3500 Martin 1, Donley Drilling C-0.; J. Haig Surv.; l 1h mi. S East­land __ __ __ _ _ 3745 Parrock 1, States Oil Corp.; H. &T.C.Ry.Co. Surv., Bl. 4, Sec. 7; 614 mi. N, ,%, E Eastland____ 4083 Pelfry 1, Root et al; H.&T.C. Ry.Co. ::¡urv., Bl. 4, Sec. 61; 12 mi. from W, 8112 from N county line _______________________ _____ 4090 Pence 1, Phillips Petroleurn Co.; T.E.&L. Surv., Sec. 2981, A­504; 5112 mi. W, 6% N of Cisco 4165 Pitcock l ; Texas and Pacific C-Oal and Oil Co. ; Wm. Frels Surv.; 2 mi. S Ranger__ _____________________ 4020 Poe 1, Independent Oil Co.; H.& T.C.Ry.Co. Surv., Bl. 3, Sec. 15; 5 mi. W, 11 S Eastland ___________ 3589 Ramscwer 1, Larson (West Adams Petrofoum Corp.) ; H.& T.C.Ry.Co. Surv., Bl. 4, Sec. 38; 14 mi. from W, 2 from N county line __________ _____________ ____ 4390 Ray 4, Root et al; H.&T.C.Ry.Co. Surv., Bl. 4, Sec. 38; 31h mi. W, 6 N Eastland -----------------------4230 Rush 1, Mid-Kansas Oil and Gas Co.; E. Finley Surv.; 3 mi. S Ranger --------------------------------3945 Elev Miss Ord 4040 1426 3699 1567 ?--4075 4075 1~5 3777 1474 369882 1514 4120 1371 3428 1426 3670? 1619 4078 1568 3843 1538 4008 4100 1454 3575 1572 3550 4362 1528 3895 4005 1420 3720 Camb 'p-Camb • • • • • * Name and location oí well Schoor, 1 Humble Oil and Refin· ing Co.; H.&.T.C.Ry.Co. Surv., Bl. 3, Sec. 50; 6 mi. S, 2 E Cisco ······-····-···-············-····------- Sihley 11, Mook·Texas Oil Co.; W. Van Norman Surv., Bl. 19; 4 mi. S Ranger..·--··········-···-····· Stewart 1, Leon Oil Co.; Wm. Van No·rrnan Surv. ; 6 mi. S, 1 W Ranger.·-···-····-···-········ Stockton 1, Cosden Oil and Gas Co·.; Wm. DeMoss Surv.; 6 mi. E, 16 S Ranger ___. ...... _ ..... Turner 24, Barclay and Crotly; H.&T.C.Ry.Co. Surv., Bl. 4, TD 3791 3642 3560 3250 Sec. 3; 3% mi. N, 1 E Eastland 3948 Underwood 1, Systems (Tidal Oil Co.); D. S. Richardson Surv.; 4 mi. W, % N Desdemona...... 3582 Vaught 5, Atlantic Oil Producing Co.; W. DeMoss Surv.; 3 mi. W, 1% S Desdemona .... .... . Ward 1, Gilman and Simmons; S. J. Robinson Surv.; 4 mi. N, 1 E Cisco ···-···-··········-····--······ Ward 1, New Domain Oil Co.; J. B. Hoxie Surv.; 4% mi. N, 1 E Cisco___________ __________________ Whitesides 1, Sipe Springs Oil Co.; J. Rubarth Surv.; 16 mi. S, 1/2 W Eastland___________________ 3245 3992 3976 3170 Elev Miss Ord Camb p-Camb 1603 3672 3755 • • 3495s2 3595 • • 1413 3658 • 1322 3100 3180 1527 3935 • 1379 3510 • 1250T ?-3160 3160 1436 3925 1415 3825 • • 1493· 3160 • • EDWARDS COUNTY The formations in Edwards County overlying those here recordecl, include Cretacoous and Upper Pennsylvanian. The Lower Pennsylvanian (Bend series) is probahly also present. Name and location oí well Holman 2, Phillips Petroleum Co.; C.C.S.D.&R.G.N.G. Surv., Sec. 25, 5% mi. from W, 1/2from N county line___________________ Peterson 1, Dalgish et al ; H.E.& W.T.Ry.Co. Surv., Bl. E, Sec. 82; 6 mi. N, 11 E Rock Springs ----------······················-····· Petersan 2, Stout et al; H.E.&W. T.Ry.Co. Surv., Bl. E, Sec. 96; 12 mi. NE Rock Springs.........__ TD Elev Miss Ord Camb p-Camb 8125 2274 7905 • 5206 2'353 4095 • • 4610 2360 4410 • • tA udetrital'' zone lu this well at depth 4092 to 4141 i1 referred proviaionally to the Mi•i-1p· pian although it may possibly be basal Pennsylvanian. The Geology of Texas-Paleozoic Systems 211 Name and Iocation of well TD Elev Miss Ord Camb p-Camb Schreiner 1, McMann Oil and Gas Co.; H.E.&W.T.Ry.Co. Surv., Bl. F, Sec. 50; 7 mi. from N,l/2 from E county line.______________ 3897 2326 374583 3805? ERATH COUNTY The formations in Erath CGunty oveTlying those here recorded are Cre­taceous and Upper and Lower Pennsylvanian. Of the Mississippian forma­tions the Barnett is probahly present. This fonnation in the Thompson well probably extends from 3655 or above to 3755. Name and Iocation of well TD Elev Miss Ord Camb p-Camb Fee (Allen) 1, Texas and Pacific Coa] and Oil Co.; I.R.R. Surv., Sec. 24; 31/z mi. from W, 2 from N county line --------------------4025 1102 3900? • Fulfer 1, Texas-Manhattan Oil and Gas Assoc.; M. Goff Surv.; 61/z mi. from W, 5 from N county line ----------------------------· 4001 1060 4000 Thompson 1, Gulf Production Co.; F. R. Lubbock Surv.; 9 mi. S, 2 W Thurber____________________ 3935 1383 3655? 3755 FISHER COUNTY The formations in Fisher CGunty oveTlying those here recorded are of Per­mian and Upper and Lower Pennsylvanian age. Name and location of well TD Elev Miss Ord Camb p-Camb George 1, Cranfill and Reynolds; B.B.B.&C.Ry.Co. Surv., Bl. 1, Sec. 200; 5 mi. from E, 6 from N C-Ounty line ------------------------6494 1789 5960 617584 FOARD COUNTY The formations in Foard County overlying those here recorded are Permian and Pennsylvanian in age. The Mississippian and sorne older formations are possibly present although absent on the uplift where these wells were drilled. Name and Iocation of well TD Elev Miss Ord Camb p-Camb Johnson 1, Humble Oil and Refining Co.; S.P.Ry.Co. Surv., Bl. L, Sec. 37, l 1h mi. from W, 8 from S county line _________ _ 5003 1670 Abst Abst Abst 4950? Mathews 1, . Shell Petroleum Corp. (Roxana) and Fain and McGaha; G. C. &S. F. Ry. Co. Surv., A-117, Bl. 3, Sec. 3; 10 mi. E, 2 N CroweJI__________________ 2858 1384 Ahst Abst Abst 2215 83The Mississippian of Boone age, "pink crinoidal", is found in this weU at 3745 to 3805 (Spencer). 84Between 6045, and the Ellenburger, 6175, is found green shale, white chert, ancl liroestQD f< Q{ undetermined age (H. A. Hemphill). This well termina tes in sand. Name and loeation oí well TD Elev Miss Ord Camb P-Camb Mathews 3, Shell Petroleum Corp. and Fain and McGaha; G.C.&S.F.Ry.Co. Surv., Bl. 3; 10 mi. E, 2 N CrowelL________ 2550· B77 Abst Abst Abst 2465 Miller 1, Gulf Production Co.; H.&T.C.Ry.Co. Surv., Bl. 8, Sec. 32, 21h mi. from E, 4 from N county line _______________ 3360 1347 2380? * * GILLESPIE COUNTY The formations in Gillespie County overlying those here recorded are of Lower Cretaceous and Upper and Lower Pennsylvanian age. Although absent in sorne of the wells here recorded the Lower Ordovician (Ellenburger group) is generally present in the county. The presence of Mississippian in the county is undetermined. Name and location oí well TD Elev Miss Ord Camb p-Camb Becker 1, Kothman et al; J. T. Stell Surv. 44; 5 mi. SW Fred­ ericksburg ------------------------580 1650T Abst 200 * Boos 4, 3 mi. SW Fredericksburg 151 130 Dickey 1, Gillespie Development Co.; 2 mi. N StonewalL _______ 660 1600T Abst Abst Abst 304 Hayden 1, Thousand Island Oíl Co.; Surv. 144; 8 mi. W Fred­ ericksburg ------------------------------1505 1850 Abst Abst 180 1182 Kott, Lewis; si de of Fred­ ericksburg 418 1725T Abst Abst Abst 168 GRAY COUNTY The overlying formations and other stratigraphic conditions in Gray County are in general similar to those of Carson County described above. Name and location of well TD Elev Miss Ord Camb p-Camb Beavers 1, Bock-Anderson; H.& G.N.Ry.Co. Surv., Bl. B-2, Sec. 124; 7 mi. from W, 15 from N county line ____________________:____ 3800 3144 Abst Abst Abst 3305 Bowers 1, Operators' Oil Co.; H. &G.N.Ry.Co. Surv., Bl. B-2, Sec. 93; 9 mi. from W, 14 from N county line -------------------3090 3038 Abst Abst Abst 2800 Bradford 1, Danciger Oil Co.; H.&G.N.Ry.Co. Surv., Bl. B-2, Sec. 123; 7 mi. from W, 14 from N county line ---------------------2741 3091 Abst Abst Abst 2670 Heitholt 1, Skelly Oíl Co.; l.& G.N.Ry.Co.Surv., Bl. 3, Sec. 153; 4 mi. SW Pampa,Nof rail­roadB5 ------------------------------------3000 3275 Abst Abst Abst 2835 ""Thio well, according to R. E. Crum (letter of Decemher 19, 1930), after clrilling thruaP 120 feet of granite encountered a fracture in the rock resulting in a flow of 40,0001000 cu. ft.. of cu and 8,000 barreis of oil daily. A well drilled by the Magnolia Petroleum Company (Latham 4) and another hy Cree, Hoover and Graham (Sullivan 1) about one-halI mi1e ­ The Geology of Texas-Paleozoic Systems 213 N ame and location of well TD Elev Miss Ord Camb p-Camb Latham 4, Magnolia Petroleum Co.; I.&G.N.Ry.Co. Surv., Bl. 3, Sec. 153, S of railroad, 3 mi. from W, 9 from N county line 2922 3276 Abst Abst Abst 2875 Sullivan 1, Graham et al (Taco­ nian Oil Co.); I.&G.N.Ry.Co. Surv., Bl. 3, Sec. 136; 4 mi. from W, 9 from N county line 2990 3273 Abst Abst Abst 2900 HAMILTON COUNTY The formations in Hamilton County overlying those here recorded are of Cretaceous and Pennsylvanian age. Name and location of well TD Elev Miss Ord Camb p-Camb Eidson 1, Jas. W. and Geo. F. McCamey; W. J. Merrifield Surv.; 4 mi. W Hamilton _________ 3854 1157 3645 3790 • HARTLEY COUNTY The formations in Hartley County overlying those here recorded are of Cenozoic, Triassic, and Permian age. The general stratigraphic conditions are similar to those of Carson County previously described. Name and location of well TD Elev Miss Ord Camb p-Camb Coots 1, Holmes and Heck; Bl. XR, Sec. 58 ; 4 mi. from S and W county lines --------------------------2990 4181 Abst Abst Abst 2965 Shelton 2, Humble Oil & Refin­ing Co.; Rio Bravo Subd., Sec. 63; 11 mi. from W, 1 from S county line ------------------------------3076 3869 Abst Abst Abst 2977 HUDSPETH COUNTY In the Diablo Platean of Hudspeth County, where this well is located, Cre­taceous, although absent in this well, is elsewhere locally present. The surface formation over much of the Platean is Permian in age. Underneath the Permian is Pennsylvanian and, locally at least, Mississippian, Devonian, Silurian, Ordovician ·and Cambrian. To what extent these early Paleozoics are represented in this well is imperfectly determined. South of the Diablo Platean the Cretaceous thickens, and in the Malone Mountains Jurassic is present. The intermontane valleys contain fil! which in the Hueco Bolson is known to attain a thickness in excess of 3500 feet. Name and location of well TD Elev Miss Ord Camb p-Camb University 1, California Oil Co.; Bl. E, Sec. 19; 131h mi. from W, lllf.i from N county line ____ 4848 5109 166486 2817 4390 4725 obtained similar results. That these three wells were interconnected was shown by the sensi­tiveness of each to the others. A well on the Holmes ranch, 5 mi1es southeast of these wells, obtained production from fractures near the surface of the granite. After drilling into granite, 1ome other wells of thia county have obtained production of oil after the gi;anite had been fractured by shootiog, thus allowing oil to eoter the wells from the adjacent granite waah. 86The Devonian is present in this well from 2096 to 2264, and the Silurian (Fusselman forma. tion) from 2264 to 2817. Ordovician in this well ineludes both upper and lower Ordovicfan (Montoya and El Paso formations). ldentifications by C. L. Baker. HUTCHINSON COUNTY The fonnations in Hutchinson County overlying those here recorded are o{ Cenozoic and Pennian a.ge. Pennsylvanian is probahly presen.t and older formations come in under the Permian and Pennsylvanian <>ff <>Í the uplift. N a me a nd location of 'well TD E lev Miss Ord Camb p-Camb Smith-Capers 1, H. T. McGee and Co. ; M. & C. Surv., Bl. Y, Sec. 10 ; 14 mi. from W, 1 from s county line --------------­---------­---­3175 2.900 Abst Abst Abst 3135? Whittenburg 12, Phillips Petro­ leum Co.; Tumlinson Surv., Sec. 3 (Elva lease) ___________________ 5333 2916 510087 IRION COUNTY The fonnations in Irion County overlying thoee here recorded include Cre­taceous, Triassic, Permian, and Pennsylvanian. Name and location of well TD Elev Miss Ord Ca mb p-Camb Ash 1, Williams et al ; Washing· ton Co. Ry. Surv.; Seo. 20; 7 mi. from S, 9% from W coun­ty line --·-------------------------______________ 8900 2712 88 8825 Suggs 1, Kingwood Oil Co.'; H.& T.C.Ry.Co. Surv., Bl. 1, Sec. 18; 11 mi. from E ,14 from S county line ----------------·--7818 2334 88 7770 Suggs 1, Benedum and Trees; H.&T.C.Ry.Co. Surv., Bl. 28· ' 12 mi. from w, 13 from N 89 county line -----------------------------8286 2376 8267 JACK COUNTY The formations in Jack County overlying those here recorded are Upper and Lower Pennsylvanian. Although not recognized in the two wells listed, the Mississippian, Bamett formation, is probahly present. Name and location of well TD Elev Miss Ord Camb p-Camb Bryson 1, Republic ; l. ·Hughson Surv.; 2 mi. from W, 12 from s county line _________________________ 5264 . 1267 5175 • • Williams 1, Watchorn Oil and Gas Co.; B.S.&T. Surv. A·88; 6 mi. from S, 11 from W coun· ty line -------------------------------------5635 1193 53-25? • • 87According to determinations made by Scruggs this well entered Viola (Fremont) at 4810, Simp1on (Hardin) at 4875, and Arbuckle or Ellenburger (Manitou) at 5100. Mi1ei1Sippian may be present in this well. 88A detrital zone occurs in the Ash well at depth 8816 to 8850 and in the Kingwood Oíl Co. Sugge well at depth 7751 to 7777. "Tbe Ellenbarger in tbl1 well ia overlain loy a detrital zone. The middle Ordov!clan (Slmp-) of tbe Big Lake oil field of Reagan County le apparently ab1ent (H. A. Hemphill). The Geology of Texas-Paleozoic Systems 215 KENDALL COUNTY The fonnations in Kendall County oYerlying those here recorded include Cretaceous and Upper and Lower Pennsylvanian. The Paleozoic of the south­em part of this county south of Boeme is within the Llanoria geosyncline and the wells in that part of the county are listed under that heading. Name and location of well Behr 1, Dixon Co.; J. W. Wilson Surv.; 10 mi. w, Ph s Ken­ dalia ---------------------------------------- Kasten 1, Mowinckle et al ; Surv. 311; T'h mi. W Kendalia _________ McCracklin 1, Sterling et al; B. E. Owen Surv.; 31h mi. NW Kendalia ------·····----------··· Werner 1, Sterling et al; J. F. Torrey Surv., Sec. 781 ; 61h mi. W, 2 N Kendalia ___________________ TD Elev Miss Ord Camb p-Camb 1899 1264 1640? 1543 1386 1092 1127 • • 1480 1398 752 926 1405 780 • KERR COUNTY The fonnation5 in Kerr County overlying those here reoorded include Cre, tacoous and Upper and probahly Lower Pennsylvanian. Name and location oí well TD Elev Miss Leigh 1, Walker-Van Duyn; J. Goodbread Surv., Sec. 38; 6 mi. from E, 9 from S county line -----------------------2828 1530 Love. 2, Evans et al ; C.C.S.D.R. G. Surv., Sec. 159·3; l/2 mi. from S, 1 from W county line . 5878 2380 Real 1, Cannon-Page (L. c. Adams); Kendall County School Surv., Bl. 15, Sec. 2; 8 mi. W, 5 S Kerrville ................. 4706 2235 KIMBLE COUNTY Ord Camb p-Camb 1624? • 5605 4665t • The fonnations in Kimble County overlying those here reconled are Cr&­taceous and Upper and Lower Pennsylvanian. A detrital zone found imme­diately a.hove the Ellenburger in the Beasley, Bode, Means, and Patterson wells probably represents the base of the Penn.sylvanian, although this material may be Mississippian in age. Name and location oí well TD Amberscm l, Wahlenmaier et al; Hubinger Surv., Sec. 167; 9 mi. N, 8 E Junction ...---········-995 Beasley 1, Delva-Tex Petroleum Corp.; T.W.&N.G.Ry.Co. Surv., Sec. 19, A-655; 5 mi. S, 3 E Junction ···-···-···-···-··········--2670 Bode 1, Dixie Oil Co.; J. S. Pat. terson Surv., Sec. 80; 13 mi. w Junction ···--------··-------3025 Elev Miss Ord Camb p-Camb 1693 410 • 2124 2570 • • 1902 2995 • • fCannon-Page No. 1 Real probably did not reach the Ellenburger limestone. Name and location of well TD Elev Miss Ord Camb p-Camb Cannon 1, McLean et al. R. ' Cochran Surv., Sec. 741; 12 mi. N, 9 E Junction__ __ __ __ ________ 1650 1728 110 795 • Hodges 1, Mudge Oil Co.; G. Kimble Surv., Sec. 27; 6 mi. NE Junction ________________________2902 1660 1635 2441? • Mears 1, Braws-Menard Oil Syn­ dicate; T.W.&N.G.Ry.Co. Surv., Sec. 26; 12 mi. N J unction _____ 3350 2257 2708 • • Patterson 1, Delva-Tex Petroleum Corp.; Kimble Co. School Lands, Sec. 750; 6 mi. fromS, 1h from W oounty line_____ _ _____ 3980 2171 3980 • LAMPASAS COUNTY The formations in Lampasa.s County overlying those h.ere recorded are Cn> taceous and Upper and Lower Pennsylvanian. Name and location of well TD Elev Miss Ord Camb p-Camb Abneiy 1, American Well and · Prospecting Co.; near Santa Fe Depot, Lampasas ___ 2012 lOOOT 440 470 ? ? Alexander Bros. 1, Mark Alex· ander et al; S. Berry Surv., A­ 31; 6 mi. SE Lampasas_______ _ 1025 1000 • • Bunch 1, Roeser ap.d Pendleton; W. G. Martin Surv.; 9 mi. from NE, 121 from NW oounty line 3008 1250 1570 • Conradt 1, Robarts et al; E.T. Ry.Co. Surv., Sec. 1; 5 mi. N, 2 W Lometa ____________________________ 2001 1500T ?-1880 1880 • Grove 1, White et al; J. A. Ab­ neiy Surv.; 61/2 mi. NE Lam­ pasas -------------------------------------2066 llOOT 2050 • • Hill l, Hill River Oil Co. (Cham­pfon) ; David Evans Surv.; 8 mi. S Lometa._______________________ 1602 1450T 417 • McCree 1, Reianeiy-Nevels Oil Co. ; Wm. F. Nicholson Surv.; 11 mi. W Lampasas________________ 1120 1400T 20 • • Morgan 1, Sunshine Oil Co·. ; Whittenhurg Surv.; 6 mi. W, 2 N Lometa __________:___ _______________ 896 795 886 • • Smith 1, C. H. White; T. R. Stiff Surv. 16; 13 mi. W, 1 S Lam­ pasas --------------------·-----------------65 1400T 29 • White 1, Texoleum Trust Co. ; Hill Surv.; 131/2 mi. W, 11/2 N Lampasas __. ·--· __ 3000 1250T 136 ? 3000t Whittenburg 1, Western Lam­ pasas Oil Co. ; fohn Boyd Surv. 612, Bl. 229, Sec. 38; 3 mi. W Lometa -----------------------------------4180 1450T 863 979 2976 3580 tPre-Cambrian samp}e at 3000 feet. The top of the pre-Cambrian may be higher. The Geology of Texas-Paleozoic Systems 217 MASON COUNTY The formations occurring locally in Mason County overlying those here re­cordoo are of Cretaoeous and Upper and Lower Pennsylvanian age. Although not rooognized in the one well here recorded, Mississippian, Ordovician, and Cambrian are locally present. Name and location of well TD Elev Miss Ord Camb p-Camb Brandenburger l, Cochran and Steward; M. Patton Surv. 118; 12 mi. W Mason __ _________ __ ________ 1900 1700T ? ? 30 1065 McCULLOCH C-OUNTY The formations in McCulloch County overlying those here recordoo include Cretaceous locally and Upper and Lower Pennsylvanian over the greater part of the county. The Mississippian and Ordovician formations are exposed lo­cally in the southeastern part of the county. Name and location of well J3aumgartner 1, Texas Hurst Syn­dicate; P. H. Schaff Surv. 402; 11/z mi. SSE B ·adv .Beasley 1, Dallas Milburn Valle.y Oil Co.; F. Winkle Surv.; 21/z mi. , 2112 E Mercury ·--------­ Brady water well, Brady _______ -Cawyer 1, Burford and Brimm; D. Mechels Surv. 968; 3 mi. SE Mercury ·Craig 1, Thomas et al ; C. Usner Surv., Sec. 1351; 41/z mi. N, 1 W Melvin -----------------------------­ Crews 1, Southwestern Petroleum Co.; U. Heinrich Surv., Sec. TD 1384 2526 2114 21W 3666 782; 1 mi. SW Rochelle _ . 1965 ·nutton 1, Thad O'Day (Day­Daley Petroleum Assoc.) ; J. H. Gibson Surv. 1; 11 mi. 1 W Brady ·Haby well, Haby and Allison; C. Volmar Surv., Sec. 138; 15 mi. SW Brady ·Morgan 1, J. E. Morgan; State School Lands Surv. 2; 2 mi. W Brady .Sellman 1, . Texas Eastern Oil Co.; C. Beag Surv. 904; 31/2 mi . E E Rochelle Shelton 1, Case Oil Co.; W. Rasche Surv., Sec. 1066 ; 314 mi. , 1/z E Lohn ------------------­White 2, A. H. Bel! et al; C. Mendell Surv., Sec. 811; 8 mi. from E, 61/z from N county line -----·--. White 1, Henderson et al; B.S.& F.Ry.Co. Surv. 1; 17 mi. N, l1/2 E Brady ------------------------------­ 2643 1920 2005 1545 1360 1401 Elev Miss Ord Camb p -Camb 1660 50 61 910? 1280 844 945 1896? 1685 187 980 1422 685 1486 ? 2100? 1755 2065 2625? 3473? 1675 605 1435? 1637 1270 l.>70 2150? • 94.0± 1900 1712A 420 1650T 578 1350 1450T 1500 1580T 1275 * • 1508T 1116 1285 • • Name and location of well TD Elev Miss Ord White 1, Thomas et al., Fisher and Miller Surv. 2586, A-362, 1 mi. E Whiteland_______ --­----------­3406 1750T 1140 Zelle 1, Prairie Oíl and Gas Co.; H.&T.C.Ry.Co. Surv. 89; 4 mi. NW Lohn --------------------------­3516 1498 1870? Camb p-Camb 1840? 2982 2485? 3309 MENARD COUNTY The fonnations in Menard County overlying those here recorded are Cre­tacoous and Upper and Lower Pennsylvanian. Although not reoogni:zed in the wells listed, the Mississippian is probably locally present. Name and location of well TD Elev Miss Ord Camb p-Camb Callan City Investment Company 1, Barnett and Drake; B.S.&F. Ry.Co. Surv., Bl. 22, Sec. 7; 7 mi. , 5 E Menard .____________________ 2207 2130 2075 Callan City Investment Company 2, J. C. Barnett; B.S.&F.Ry.Co. Surv., Sec. l; 6 m1. N, 4 E Menard --------------------------------------2124 2068 2060 • Davis 1, Sabens et al; Surv. 31; 1%, .mi. W Hext_______________________ 720 1809 Abst 434t MILLS COUNTY The fonnations in Milis County overlying th09e here recorded are Cretaoeous and Upper and Lower Pennsylvanian. Name a nd location of well TD Elev Miss Ord Camb p-Camb Cryer 1, Milis County Oíl Co.; J. M. CTark Surv. 14; 12 mi. W, 5 N Goldthwaite____ _____________ 1950 1317 1885 • • Harrison and Slayden 1, Venture Oil Co. ; T. Carroll Surv. 401; 14 mi. W, 8 N Go.Jdthwaite_ ___ 3268 1271 1540 ? ? Hendry 1; L. Bostic Surv. ; 10 mi. E Goldthwaite__________________ 2448 2357 2417 • • Howell 1, Atlantic Production Co. (Atlantic Oi! Producing Co.) ; M. Kenedy Surv., Sec. 647; 41/2 mi. S, 3 W Gold­thwaite --------------------------------­2430 1228 2007 • Locklear 1, The Texas Co.; Sam Cates Surv.; .8 mi. W, Goldthwaite ----------­___ 1 N _____ 3324 1248 1848 19B • Ratliff 1, Bowers et al; Dawson Surv.; S part of county __ ______ Robertson 1, CTarion Oíl Co., J. 1275 1233 1260 M. Douglas; Caldwell County School Lands Surv. 112, Bl. 16; 51/2 mi. W Goldthwaite ___________ 2716 1338 2118 • Tyson 1, A. R. Forstner et al; T.&N.0.Ry.Co. Surv. 2;-10 mi. W, 10 N Goldthwaite·______________ 2520 1372 2324 • fNo umple11 were received between 203 and 434 feet. The top of the Cambrian may be above 434 feet. The Geology of Texas-Paleozoic Systems 219 Name and location of well TD Elev Miss Ord Camb p-Camb Ware 1, Ware Haywood Oil Co.; H. Thurmester Surv.; 6 mi S, 1 E Goldthwaite ____________________ 2513 1248 2473 • • Whittenburg 1, Sterling Oil Co.; A. Thompson Surv. 2; 2 mi. E Ebony -------------------------------1285 1435 1175 • Young 1, Fidelity Oil Co.; Boat-right Surv.; 15 mi. W, 1 % S Goldthwaite ------------------------3314 1971 2036 MONTAGUE COUNTY The formations in Montague County overlying those here recorded are Cn> taceous, in the eastern part of the county, and Upper Pennsylvanian. The presence or ahsence of the Lower Pennsylvanian is undetermined. Name and location of well TD Elev Miss Ord Camb p-Camb Bouldin 1, Bridwell Oil Co.; E. Votaw Surv. ; 19 mi. N, Ph E Montague ------------­-----------------­ 3024 795 ? 2235? 2683 Edmondson 11, Bridwell Oil Co. ; T. R. Edmonson Surv., A-222; 20 mi . N 1h E 1ontae;ne _____ 2133 758 2078? Hinton 1, Humphreys Corp.; A. Coates Surv.; 7% mi. N Nocona 1844 802 1841 ] ones 1, Pure Oil Co. ; W. Dono­ ho Surv.; Lot 41 (82-acre tract) ; 7 mi. N Nocona _________ 1966 782 Abst Abst Abst 1797 Jones 2, Pure Oil Co.; W. Dono­ ho Surv. ; Lot 41; 7 mi. N No­ cona ____ --------------------­------------­__ _ 2795 861 Abst90 Abst Ahst 2084 Jones 1, Red River Oil Co.; W. Donoho Surv.; 7% mi. N No­ cona ----------------------------------­2595 858 ? ? 2500 Lemons 1, The Texas Co.. ; S. Lit­ tle Surv., A-417; 7% mi. N Nocona -------------------­-----------­ 2915 891 ? ? ? 2707 Maddox 3, Boyd Oil Co.; C. W. Thompson Surv.; 10 mi. N No­ cona ------------------------------­2273 864 ? ? 2262 Monroe 1, Warner Oil Co.; Field­ ing-Seacrest Surv.; 9 mi. N St. Jo ---------------­--------------------­ 3243 946 ? 2910± 2950 Rowland 3, Pure Oil Co·.; J. Chambliss Surv.; 10 mi. N, Z E Nocona ---------­----------­--­2700 848 ? ? ? 2622 OOA core of micaceous shale and sandstone, probably Pennsylvanian, was taken from the Pure · Oil Co. No. 2 Jones at depth 1978. Pre-Cambrian was entered at 2084, the early Paleozoic being .absent. The absence of early Paleozoic, Cambrian to Mississippian or Lower Pennsylvanian, -is indicated in severa! other wells in this and adjoining counties on the Red River uplift. MOORE COUNTY The formations in Moore County overlying those here recorded are of Permian and Cenozoic age. Pennsylvanian and older deposits are possibly also present in the county. N ame and location of well TD Elev Miss Ord Camb p-Camb Kilgore 1, Gulf Production Co.; E.L.&R.R.Ry.Co. Sur v., Bl. PMc, Sec. 22; 2 mi. from S, 10 from W county line_ __ ___________ _ 3645 3743 3450 OLDHAM COUNTY The formations in Oldham County overlying those here recorded are of Cene>­zoic, Triassic, and Permian age. These·wells are located on the Bravo dome. On this dome Permian rests on pre-Camhrian. Off of the dome sorne of the intervening Paleozoic systems are probably represented. Name and location of well TD Elev Miss Ord Camb p-Camb Matador 2, Benedurn and Troos ; E.L.&R.R.Ry.Co. Surv., Bl. 7, Sec. 26; 12112 mi. from W, 11 from N county line ------------------­2390 3635 Abst Abst Abst 238o.? Shelton 1, Benedurn and Trees; Bravo Subd., Sec. 137; 6 mi. from W, 6112 from N county line, N of Canadian River near New Mexico line . ____ ____ _______ 2580 3850 Abst Abst Abst 2462? Shelton 1, Hurnble Oil and Re­ fining Co.; Bravo Subd., Sec. 43; 11112 mi. from W, 6 from N county line ----------------····-----------­2590 3699 Abst Abst Abst 2560? PALO PINTO COUNTY The formations in Palo Pinto County overlying those here recorded are Upper and Lower Pennsylvanian. Name and location of well TD Elev Miss Ord Camb p-Camb Chestnut 2, Shaw et al; T.P.Ry. Co. Surv., Bl. A, Sec. 40; 9 mi. S, 1 W Mineral Wells ______________ 5123 1124 4748 4918 Finch 2, Nelson Oíl Syndicate; N. Dickerson Surv., Subd. 45, Bl. 44; 3 mi. S Gordon ______ _____ 4146 950 3685 3820 Guest 1, Goodwin, Lacey and White; Burleson County School Lands Surv. ; Sec. 73 ; 4 mi. from S, 8% from W county line ----------------------------------------------3850 993 3620 3835 McDonald (Watson) 1, The Texas Co.; T.P.Ry.Co. Surv., A-1077, Bl. 2, Sec. 31; 2 mi. W, 1 S . . , Palo Pinto ----------------------------------4665 1033 4410 4590 McDonald 2, Gordon and Ghol­ son ; T.P.Ry.Co. Surv., Bl. 2, Sec. 33, 1 mi. S Palo Pinto________ 4887 1233 4650 4845 • Tke Geology of Texas-Paleozoic Systems 221 Name and location of well TD Elev Miss Ord Camb P-Camb Pennington 1, Magnolia Petro­leum Co.; T.E.&L. Surv., Sec. 1789; 12 mi. W, 4% N. Min­eral W ells -----------·-·--·----------------4650 946 4560 * Rasmussen 2, Pender Production Co.; T.P.Ry.Co. Surv., Bl. 3, Sec. 46; 2% mi. SE Brad____ _ 4245 1149 4ü80 4215 • • Ringo 1, Texas and Pacific Coa! and Oil Co.; T.P.Ry.Co. Surv., Bl. 2, Sec. 85; 7% mi. from S, 12 from W county line ............ : 4375 1006 4060 4250 Sanger l , Owens, Burkett and Wheeler; J. J. Metcalf Surv., A-341; 10 mi. W, 3 N Mi neral W ells -------------·---··--····--·-----------4890 1003 4706 * Seaman 1, Roxana Petroleum Co.; T.P.Ry.Co. Surv., Bl. 3, Sec. 6; 9% mi. from N, 1 from W county line .._______________ 4535 1248 4370 4519 • Strawn Coa! Co. 4, Burton and McKee; A. Ashworth Surv.; 2% mi. N, 2% E Strawn _______ 3797 1010 3607 3780 * Stuart 153, Texas and Pacific Coa! and Oil Co.; W. J. Better­ ton Surv., Bl. 1; 4 mi. W Strawn ·-------------···-----···-----3776 1152 3750 * Taylor 1, Gordon and Gholson; T.P.Ry.Co. Surv., Bl. 1, Sec. 21; 2 mi. W, 1 S Palo Pinto ______ 4792 1114 4527 4720 • • Texas and Pacific Coa! and Oil Co., Fee 1, Lassiter et al; A.B. &M. Surv., Sec. 5; 11/2 mi. NE Gordon -------------------------------5630 948 3913 4-029 Weldon 2, Zada Belle Oil Co.; C.E.P.I.&M.Co. Surv.; 21h mi. S Pickwick ..............____________ 4700 1089 4540 4640 PECOS COUNTY The formations in Pecos County ovedying those here recorded include Cretaceous over the central and southern parts of the county, Triassic over much of the county, and Permian over the entire county. In the one well drilled to the pr&-Cambrian, format.ions older than Pennsylvanian are absent. This well, however, is located on an uplift and these formations may have been eroded from the uplift in pre-Permian time and may come into the section on the sides of the uplift or in the basins. Name and location of well TD Elev Miss Ord Camb p-Camb University 1, Shell Petroleum Corp. and Humphreys Corp.; University Land Surv., Bl. 26, Sec. 23; 10 mi. E, 9 N Fort Stockton ------····-----------------------5204 2620 Abst Abst Abst 4750 POTTER COUNTY The formations in Potter County overlying those here recorded are of Ceno­zo.fo, Tria.ssic, and Permian age. See University of Texas Bulletin 2330. Name and loca,tion of well TD Elev Miss Ord Camb p-Camb Bivens 1, Prairie Oil and Gas Co.; Gunter & Munson Surv., Bl. M-20, Sec. 42; E county line, 2 mi. S county line. ______ 3485 3238 Abst Abst Abst 2525 Masterson 1, Emerald Oil Co.; Gunter & Munson Surv., Bl. 3, Sec. 82; 20 mi. NW of Ama­ rillo ---------------------------------------------2148 3465 Abst Abst Abst 2000 Masterson 1, Greater Amarillo Oil Co.; Gunter & Munson Surv., Bl. 3, Sec. 20; 30 mi. N Amarillo ----------------·---------------------2595 3423 Abst Abst Abst 2045 Masterson 1, Ranch Creek Oil Co.; D.&P.Ry.Co. Surv., Bl. 0­ 18; 25 mi. N Amarillo _____________ 3397 Abst · Abst Abst 2480 M~sterson l. R~ncb Creek Oil Co.; E.L.&R.R.Ry.Co. Surv., Bl. B-11, Sec. 2 ; 20 mi. N Amarillo -------------------------_____ ____ 2675 3434 Abst Abst Abst 2200 Mastersnn 3, Arnarill0 Oil and Gas Co. ; D.&P.Ry.Co. Surv., Bl. 0-18, Sec. 102; 24 mi. N Amarillo -----------------------3082 3455 Abst Abst Abst 2698 Masterson 5, Amarillo Oil and Gas Co. ; Gunter & Munson Surv., Bl. 3, Sec. 31; 24 mi. NE Amarillo ---·-------------------------2230 3279 Abst Abst Abst 2205 REAGAN COUNTY The formations in Reagan County overlying those here recorded are of Cretaceous, Triassic, Permian, and Pennsylvanian age. See University of Texas Bulletin 2901, pp. 175-201, and Bulletin 3201. Name and location of well TD Elev Miss Ord Camb p-Camb University 1-B, Continental Co...__ 8671 2734 Abst 851291 University 2'-B, Continental Co ..___ 8740 2705 Abst 8450 University 3-B, Continental Co. ___ 9020' 2734 Abst 8610 University 4-B, Continental Co..___ 8560 272-2 Abst 8345 University 5-B, Continental Co..... 8483 2738 Abst 8410­ University 6-B, Continental Co. ___ 8335 2716 Abst 8245 University 1-C, Big Lake Oil Co. 9562 2730 ? 8618 • • University 2-C, Big Lake Oil Co. 8820 2.70'4 Abst 8540 • 81All of the wells here listed for Reagan County are in the Big Lake oíl field. The prin· cipal deep production of oil and gas in this field is from the Ellenburger limeatone which has been drilled into from 103 to 947 feet. The Ellenburger in this field is overlain by Middle Ordovician Simpson series which ran¡!es in thickness from O to 350 feet. The depth in feet at which tb:e Simpson was reached in these wells is as followe: l · B, 8305; 2-B, 8225; 3-B, 8390; 4-B, 8195; 5-B, 8325; 6-B, 8155; 1-C, 8346; 2-C, 8280; 3-C, 8470; 4-C, 8325; 5-C, 8205; 6-C. 8340; 1.c, 8160; 8-C, 8405; 9-C, abseut. The Geology of Texas-Paleozoic Systems 223 Name and location of well TD Elev Miss Ord Camb p-Camb University 3-C, Big Lake Oil Co. 8923 2736 ? 8820 • • University 4-, Big Lake Oil Co. 8833 2704· Abst 8606 University 5-C, Big Lake Oil Co. 8872 2697 Abst 8350 University 6-C, Big Lake Oil Co. 8836 2686 ? 8465 • University 7-C, Big Lake Oil Co. 8825 2697 ? 8270 * University 8-C, Big Lake Oil Co. 8368 2691 Abst 8610 University 9-C, Big Lake Oil Co. 8431 2680 Abst 83·15 RUNNELS COUNTY The formations in Runnels County overlying those here recorded are Lower Permian and Upper and Lower Pennsylvanian. Name and location of well TD Elev Miss Ord Camb p-Camb Giesecke 1, Russell Production Co. (M. D. Cerf) ; J. Huhges Surv. 227; 17 mi. SE Ballinger, 1 mi. from E, 2 from S county li ne 3450 1527 3395 Herring 1, Marl ancl Oil Co.; Sec. 139; 3 mi. W Talpa_____________ 4200 1850A 4085 Russel 1, Gulf Production Co.; James Hughes Surv. ; Ph mi. from E, 21h from S county line ----------------------------·----·--·--3505 1677 3440 SAN SABA COUNTY The formations in San Saba County overlying those here recorded are Cretaceous, locally present, and Upper and Lower Pennsylvanian. In the southern part of the county, Lower Pennsylvanian, Mississippian, Ordovician, Cambrian, and pre-Cambrian formations are exposed. Name and location of well TD Elev Miss Ord Camb p-Camb Grane 1, Wilmott et al; % mi. NW San Saba____________________________ 727 1200T 680 717 Cummings 1, Coline Oil Co. ; C. Herberg Surv. ; 3 mi. NNE Locker _________ ____ ______ __ 1380 1362 760 805 Heatherly 1, Royal Duke Oil Co. (Duke-Knowles) ; L. Burchell Surv. 255; 6 mi. N Richland Springs -----------------------·-1900 1425T 605 • Leverett 1, Texas-Mexia Drilling Syndicate; f. Gyton Surv. 79; 6 mi. , 4 E San Saba -----------1003 1250T 893 940? • Maxcey 1, Moss and Keeling; C. Hernandez Surv.; % mi. SE Richland Springs ----------·--------­180 Moore 1, Cayce Petroleum Co.; C. Hernandez Surv.; 8 mi. NE San Saba ------------------------·--·---·--1659 1250T 1281? 1631 1655 Moore 1, Wilmott et al; C. Her­nandez Surv., Bl. 78; 7 mi. NE San Sabat ------------------------3087 1250 1066 2870 Munsel 1, Cayce Petroleum Co. ; Rogers Surv. 26; 6 mi. E, 2 N San Saba ·----------------------798 1250T 404 486 tMoore 1, Cayce Petroleum Co. apparently drilled across a fault plane, accounting for the rcduced thickness oí Ellenburger nnd Camhrian. Name and loeation of well TD Elev Miss Ord Camb p-Camb Roper 1, W ebb et al; 2 mi. S Bowser -------------------------------------750 1340T 625 665 • • Shaw 1, Graves et al ; 2 mi. N Locker -------------------------------1000 B50T 800 • • Winkler 1, Tyler et al ; Sec. 626; Ph mi. from N, 4 from W county line ---------------------------------1325 1368 1030 1079 • • SHACKELFORD COUNTY The formations in Shackelford County overlying those here reoorded are of Permian and Upper and Lower Pennsylvanian age. Name and location of well TD Elev Miss Ord Camb p-Camb Brazell 4, Phillips Petroleum Co.; B.A.L. Surv., Sec. 51 ; 1 mi. from E, 10 from S county line ---------------------------------------------4508 1320 4380 Cooke A-89-60, Roeser-Pendleton and Continental Oil Co.; E.T. Ry.Co. Surv., Sec. 60; 17 mi. from S, 14 from E county line 5331 1606 482092 4950 • Snider 2, Associatet al; Huseman Surv., A-93, Lot 1, Tidwell Subd., 2 mi. N, 51/z W Burkburnett ----------------------------3595 1080 ? ? 3575 WILBARGER COUNTY The formations in Wilbarger County overlying those here reoorded are 1>f Permian and Pennsylvanian age. Name and location of well TD Elev Miss Ord Camb p -Camb Stevens 14-A, Barkley-Meadows Co.; H.&T.C.Ry.Co. Surv., Bl. 14, Sec. 83; 8 mi. S Vernon --3007 1058 Abst Abst Abst 2970 Wagner 2, Sloan Co.; H.&T.C. Rv.Co. Surv., Bl. 4, Sec. 32; 10 mi. from S, 11 from E county line; Rock Crossing pool 4095 1116 395795 ? Zipperle 1, The Texas Co.; H.& T.C.Ry.Co. Surv., BI. 14, Sec. 80; 8 mi. S, 1 E Vernon 2970 1253 2881 YOUNG COUNTY The formations in Young County 1>verlying thl>S6 here descrihed are Per­mian, in the western part of the county, and -Upper and Lower Pennsylvanian. Name a.nd location o~ well TD Elev Miss Ord Camb p-Camb Arnold 1, The Texas Co.; Jona­than a.nd Loo Surv.; 81/z mi. W, 1% N Graham _ 4711 1270 470597 ? * Bullock 1, Panhandle Refining Co.; M. Hamilton Surv.; 5 mi. W, 2 N Graham _ 4952 1117 462997 4775 • Bunger l, The Texas Co.; J. L. Mtercer Surv., A-1783, Bl. 11, l Yz mi. from S, 9% from E county line 4760 1_143 4690 * * Burnett 1, Pitzer and West et al; T.&N.0.Ry.Co. Surv. 6; 4 mi. W. Graham ·---------------------______ 4850 1243 4830 * * Corbett 1, Transcontinental Oil Co.; R. Campbell Surv.; 3 mi. SW South Bend ------------------------4590 1237 4550 * 9CiMay be CambTian. "Thie well has heen reported on the evidence of some foHils obtained from it as having probablY entered Viola. However, the ÍOHils are fragmentary, and the formation may be of Mississippian age. A lew otber welle in tbis field reach similar rock. The Geology of Texas-Paleozoic Systems 229 Name and location of well TD Elev Miss Ord Camb p-Camb Granth.am 3, Hinson-Tidwell; E. J. Ribble Surv.; 31/z mi. from S, 9 from E county line .. ______ 4812 1084 450097 4575 • • Kimbrell 1, Panhandle Refining Co.; W. A. Crumpton Surv.; 9 mi. SE Graham ; 21/z mi. from E, 51/z from S county line .. ___ 4892 1092 4630 4825 • McOusky 7, Panhandle Refining Co.; South Bend pool, 1 Yz mi. W South Bend96 __ ___________ ___ 4201 1040 4148? Morrison 1-A, Panhandle Refin­ing Co.; B. N. Hammond Surv.; 1 mi. E, 11/z N Graham 4885 1203 4820 • Newby 1, Gulf Production Co.; J. H. Fisher Surv., A-1598; 2% mi. from S, 6 from E county line --·--·---·-.. -----..-----..·-------4655 1185 4630? • • Scott 9, Roxana Petroleum Corp.; l. Garrett Surv.; l1/2 mi. S, 11/z W So uth Bend 4485 1075 420097 4452 Stovall 3-A, Ruthada Oíl Co.; J. Tobin Surv., BI. 31, Stovall Subd., 11/z mi. SW Bend _ 4434 440097 4430 • Weldon 1, Jacob Oíl and Gas Co.; W. B. Lyttle Surv., A-1776; 41/z mi. from S, 71/z from E county line -----------·---_________________ 4548 1029 432097 4530 • • Whitley 1, Continental Oil Co.; T.E.&L. Surv., Sec. 422; 1 mi. N Newcastle ----·-----------·----·--5063 1197 473097 5038 • COTTLE COUNTY Since this table of wells was set in type a well has heen completed in Cottle County which reached rock prohably of pre-Cambrian age. This well afl'ords an important record since it shows that the Red River uplift extends westward through Cottle County. For this reason it has seemed desirable to add this Cottle County well to the list. Granite wash was entered in this well at 4645 feet; a ffow of water was obtained at 4718 to 4720 feet. A fusulinid, which according to M. P. White is of Strawn age, was obtained from within the granite wash. The formations in Cottle County overlying those here recorded are of Upper Pennsylvanian and Permian age. Name and location of well TD Elev Miss Ord Camb p-Camb Puercel 1, Merry Eros. and Perini and Darby Petrolenm Corp.; J. H. Stephens ~urv., Bl. "B," Sec. 40; 114 mi. from W, 10 from S county line 4740 2018 Abst Abst Abst 4740 97The Mississippian n rhe Arnold. Grantham. and Stovall wells is probably "pink crinoidal" limestone. A s:milar limestone is found in BuIIock 1 at depth 4747 to 4775, in Scott 9 at 4260? to 4410, in Whitley 1 at 4840 to 5035, and in Weldon 1 at ·4480 to 4530 (R. E . Cile1). ILLUSTRATIONS OF SOME PALEOZOIC FOSSILS Although fossils are present in sorne formations of all of the Paleozoic systems as developed in Texas, the number and kinds of fossils present varY.. with the varying living conditions and facies of deposition. The oldest Paleozoic represented, the Upper Cam­brian, contains an abundance of fossils, the predominating forros being trilobites and brachiopods. Fossils abound in most of the shales and limestones of the Ordovician seas, although sorne of the dolomitic limestones are relatively barren. The Silurian, known in Texas only in the limestone facies, contains sorne, although not many, fossils. In the Devonian formations the shales, Percha forma· tion, are highly fossiliferous, while the Caballos novaculite contains so few fossils as to be doubtfully placed in stratigraphic position. The Mississippian, most of the Pennsylvanian, and sorne of the Permian formations are highly fossiliferous. Most of the Paleozoic fossils of the Texas formations are marine invertebrates. Land plants, however, are present in sorne of the Pennsylvanian and Permian formations, and land vertebrates, amphibians and reptiles, abound in the Permian. In contrast to the abundance of fossils, sorne of the Permian formations accumulated in the super-saline seas of the Permian basin, are notably unfossilifer­ous. It is not practicable to illustrate in this volume more than a very few of the vast number ·of organic remains, plant and animal, pre­served in the sediments of the Paleozoic systems. Of the illustrations which follow, Plates II and III, Upper Cam­brian and Lower Ordovician fossils, have been contributed by the United States Geological Survey. The illustrations were made in the Division of Illustrations, and the plates arranged, and the description of fossils written by Doctor Josiah Bridge of that survey. Plate IV, Ordovician graptolites, has been arranged, identification of fossils made, and descriptions written by Dr. Rudolf Ruedemann of the New York State Museum. Plates V and VI, Pennsylvanian and Per­mian fossils, have becin arranged and the descriptions written by Professor F. B. Plummer. Figures 4-6 of this plate, illustrating Schwagerina, are from a manuscript prepared by Mr. G. G. Hender­son on the Fusulinids of the Moran Formation of Texas. Grateful acknowledgment is made to the organizations and individuals who have contributed these illustrations of Texas Paleozoic fossils for this volume. The Geology of Texas-Paleozoic Systems 231 EXPLANATION OF PLATES 11 TO VI PLATE 11 CAMBRIAN FOSSILS Figures­1-3. Eoorthis remnichia texana (Walcott) l. Dorsal valve. Paratype. United States National Museurn No. 52369·d. 2. Ventral valve. Holotype. United States National Museum No. 52369-a. 3. Profile of ventral val ve. Ali three figures x % . Wilberns formation, Cold Creek Canyon, Burnet County, Texas. 4-5. Eoorthis wichitaensis (W alcott) 4. Dorsal valve. Paratype. United States National Museum No. 52379-b. 5. Ventral valve. Paratype. United States National Museurn No. 52379-a. Wilberns formation, Cold Creek Canyon, Burnet County, Texas. 6-7. Huenella texana (Walcott) 6. Ventral valve. Holotype. United States National Museurn No. 52494-a. 7. Dorsal valve. Paratype. United States National Museurn No. 52494-c. Wilberns formation, Packsaddle Mountain, Llano County, Texas. 8-9. Lingulella acutangula (Roemer) 8. Partially exfoliated ventral valve. Plesiotype. United States National Museum No. 27412-a. Wilberns formation, Honey Creek, Llano County,98 Texas. 9. Ventral valve. Holotype. Geological and Paleontological Museum, University of Bonn. Wilberns formation, San Saba River near the Mason-Menard county line, Texas. lOLll. Lingulella texana Walcott 10. Interna] mold of a dorsal valve. Holotype. United States National Museum No. 51806-a. Wilberns formation, Morgan Creek, Burnet County, Texas. ll. Partially exfoliated dorsal valve. Plesiotype. United States National Museum No. 51805-a. Wilberns formation, Honey Creek, Llano County,99 Texas. 12-13. Billingsella coloradoensis (Shumard) 12. Partially exfoliated ventral valve. Plesiotype. United States National Museum No. 34774-a. Wilberns formation, Packsaddle Mountain, Llano County, Texas. B. Ventral valve. Plesiotype. United States National Museum No. 34777-b. Wilberns formation, Morgan Creek, Burnet County, Texas. 14, 15, 16. Obolus matinalis (Hall) 14. Ventral valve. Plesiotype. United States National Museum No. 52419-a. 08In Monograph 51 of the United States Geological Survey, and elsewhere, this locality is cited as Honey Creek, Burnet County, but it is evident from Walcott's notes that the collections were made on Honey Creek, 8 miles southeast of Llano, which is a well known &ection. 99See note under fig. 8. Figures-Cap Mountain formation, Potatotop Mountain, Burnet County, Texas. 15. Partially exfoliated dorsal valve. Plesiotype. United States National Museum No. 51566-a. Wilberns formation, Cold Creek Canyon, San Saba County,100 Texas. 16. Profile of the specimen shown in Figure 15. 17, 18, 19. Elvinia roemeri (Shumard) 17-18. Profile and dorsal views of a medium sized cranidium. Wilberns formation. Packsaddle Mountain, Llano County, Texas. 19. Pygidium of a larger specimen. Plesiotype. United States Museum No. 70261. Wilberns formation. Packsaddle · Mountain, Llano County, Texas . .20-21. Bumetia urania (W alcott) Dorsal and lateral views of a cranidium. Holotype. United States National Museum No. 23861-a. Wilberns formation, Packsaddle Mountain, Llano County, Texas. 22-23. "Crepicephalus" texanus (Shumard) 22. Dorsal view of a cranidium, in which the outline has been restored and the free cheeks added. Plesiotype. Unit.ed National Museum No. 61647. 23. Ventral view of a fragmentary pygidium. Plesiotype. United States National Museum No. 61650. Both specimens from the Cap Mountain formation, head of Clear Creek, Potatotop Mountain, Burnet County, Texas. 24-25. Wilb emia pero (Walcott) Dorsal and lateral views of a cranidium. Holotype. United States National Museum No. 23859. Wilberns formation, Morgan Creek, Burnet County, Texas. 26-27. Pterocephalia sancti-sabae Roemer 26. Dorsal view of cranidium. Holotype. Margins somewhat restored and free cheeks added from other specimens. 27. Dorsal view of a pygidium. Paratype. Margins restored. Both specimens in the Museum of Geology and Paleontology of the University of Bonn, Germany. Wilberns formation, San Saba River, near the Mason­ Menard county line, Mason County, Texas. 28. "Girvanella" sp. Fragment of a block of limestone containing numerous globular bodies, presumably of alga] origin. Wilberns formation, Ft. Sill equivalent, 5 miles west of Cherokee, San Saba County, Texas. NoTE:-Figures 1-8 and lOt-16 are taken from Walcott, United States C.eological Survey Monograph 51; Figures 19-21, 24-25 are from specimens figured . by Walcott, Smithsonian Miscellaneous Collection, vol. 75, No. 3; Figures 22-23 are from specimens figured by Walcott, Smithsonian Miscel­laneous Collections, vol. 64, No. 3; Figures 9, 26-27 are ' photographs of Roemer's types recently loaned by the University of Bonn. In sorne instances the stratigraphic horizon is not the same as the one ·originally assigned, but ali such changes are based on later and more exact information. 100'fhis locality is given ai Burnet County in Monograpb 51 of the United Statea Geological Survey, p. 213, but Walcott's personal copy contains a note in bis handwriting changing thit reference to San Saba County. 2 4 The Geology of Texas-Paleozoic Systems 233 PLATE 111 FOSSILS FROM THE ELLENBURGER LIMESTONE (Upper Cambrian and Lower Ordovician) Figures­ 1. Scaevogyra swezeyi Whitfield. Dorsal view. Basal Ellenburger (Potosi equivalent), west bank of Colorado River, 0.75 miles NE. of the mouth of Fall Creek, San ·Saba County, Texas. Plesiotype.-United States National Museum No. 86944. 2. Scaevogyra elevata Whitfield. Lateral view. Same horiwn and lo­cality as-the preceding. Plesiotype.-United States National Museum No. 8694.5. 3. Euptychaspis typicalis Ulrich. Ventral view of an imperfect crani­dium X 3. Residual cherts of the lower Ellenburger limestone (Eminence equivalent) , 3.3 miles north of Cherokee, San Saba Coun­ty, Texas, on the Cherokee-San Saba road. Plesiotype.-United States National Museum· No. 86946. 4. Stenopilus cf. S. latus Ulrich. Dorsal view of an incomplete crani­dium. Residual cherts of the lower Ellenburger limestone (Eminence equivalent), 170 feet above base of formation, on west bank of Colo­rado River, 0.75 miles NE. of the mouth of Fall Creek, San Saba County, Texas. Plesiotype.-United States National Museum No. 86947. 5. Gasconadia cf. G. putilla (Sardeson). Lateral view of an incomplete specimen X 2. Residual chert of the Ellenburger limestone (Gas­conade equivalent), 2. 5 miles north of Camp San Saba, McCulloch County, Texas, on the Mason-Brady road. Plesiotype.-United States National Museum No. 86948. 6. Eccyliomphalus gycoceras (Roemer). Natural sections of two speci­mens showing the characteristic mode of occurrence. Lowest white limestone horizon of the Ellenburger (Gaseonade equivalent ), 1.45 miles north of Camp San Saba, McCulloch County, Texas, on the Mason-Brady road. Plesiotype.-United States National Museum No. 86949. 7. Helicotoma uniangulata (Hall). Dorsal view of an average sized speci­men. Residual chert of the Ellenburger limestone (Gasconade equi­valent), 4.5-5 miles north of Cherokee, San Saba County, Texas, on Cherokee-San Saba road. Plesiotype.-United States National Museum o. 86950. 8. Pelagiella paucivolvata (Calvin ). Dorsal view. The spire is extremely low, scarcely rising ahove the body whorl. The latter is strongly compressed dorso-ventrally and sharply angled on the periphery. Same horizon and locality as the preceding. Plesiotype.-United States National Museum No. 86951. 9. Ozarkina typica Ulrich and Bridge. Ventral view of an incomplete specimen. Residual chert of Ellenburger limestone. (Gasconade equivalent), 2.5 miles northwest of Camp San Saba, McCulloch County, Texas, on the Mason-Brady road. Plesiotype.-United States National Museum No. 86952. 10. Ophileta polygyrata (Roemer). Dorsal view of the holotype. Ellen: burger limestone ( ?Tribes Hill equivalent), San Saba River valley near the Mason-Menard county line about 15 miles southwest of Camp San Saba. Original in the Museum of the University of Bonn, Germany. · Figures­11-12. Roubidouxia umbilicata Ulrich and Bridge 11. Lateral view of a silicified fragment of the body whorl, spire re­stored from other specimens. 12. Same specimen as seen from above. Fragments of this sort are common in residual cherts of the Roubidoux equivalent at severa! localities. Plesiotype.-United States National Museum No. 86953; from residual chert of the Ellenburger limestone (Roubidoux equi­valent) on the White Ranch road 1.3 miles southwest of the crossing of Llano River, Mason County, Texas. The species is also abundant in the limestones and dolomiteo of the Roubidoux equivalent at severa! localities. 13--14. Leccano-spira sancti-sabae (Roemer) 13. Ventral view of the holotype. 14. Natural section of the body whorl at a. Ellenburger limestone (Roubidoux equivalent) somewhere be­tween Pontotoc and the San Saba River. Original in the Museum of the University of Bonn, Germany. 15. Calathium sp. A large silicified sponge which is rather common in upper portion of the Ellenburger (Jefferson City or Cotter equiva· lents). Sponges of similar types are also found in the Monument Spring dolomite of the Marathon region and in the El Paso limestone. The figured specimen, United States NationaI Museum No. 86954, is from the upper part of the Ellenburger limes tone (? Jefferson City equivalent) about 4.SO feet above the base of the section on Honey Creek, about 9 miles southeast of Llano, Llano County, Texas. The Geology o_f Texas-Paleozoic Systems 235 PLATE IV ORDOVICIAN GRAPTOLITES FROM THE MARATHON AND SOLITARIO REGIONS Ali figures on this plate are reproduced X 1.5 from camera lucida drawings by R. Ruedemann. The identifications are all by Ruedemann, and the horizons and localities have been verified by P. B. King. · Figures­ 1. Didymograptus nitidus Hall. Marathon limestone 8 miles southwest of Marathon, Texas, on road to Roberts ranch. R. E. King, collector. United States National Museum No. 85363. f 2. Didymograptus bifidus Hall. Marathon !imestone. The Solitario, Pre­sidio County, Texas. Baker and Sellards, collectors. 3. Tetragraptus frutiC'osus Hall. Same forrnation and locality as pre­ceding. 4•. LoganograptUs logani (Hall). Marathon limestone 1 mile northwest of hill having B. M. 4360, northwest of the Peña Blanca Mountains, near MarathonTexas. Hosterman and Baker, collectors. 1 5. Didymograptus cf. D. extensus Hall. Same formation and locality. 6-7. Phyllograptus ilicifolias Hall. Marathon limestone. The Solitario, Presidio County, Texas. Baker and Sellards, collectors. 8. Phylfo{!raptns anna Hall. Marathon limestone 1 mile northwest of hill having B. M. 4360, northwest of the Peña Blanca Mountains, near Marathon, Texas. Hosterman and Baker, collectors. 9. Phyllograptus typus Hall. Same formation and locality. Also from the Alsate shale. 10. Oncograptus upsilon T. S. Hall. Alsate shale 3· miles northeast of Woods Hollow Tank, south of Marathon, Texas. P. B. King, collector. This is an Australian species and this is the first recorded occur­rence of it in 1orth Am erica. 11--12. Glyptograptus amplexicaulus (Hall ) var. perteniiis· Ruedernann. Lime­stone in the Maravillas cl1ert, 0.8 miles east-southeast of B. M. 4361, southwest portion of the Hess Canyon quadrangle, north of Marathon, Texas. R. E. King, collector. United States National Museum No. 85361. 13. Glossograptus echinatus Ruedemann. Woods Hollow shale, 100 feet below Maravillas chert, 3.75 miles N. 50º E. of Roberts ranch, southwest of Marathon, Texas. Sidney Powers, collector. United States National Museum No. 85371. 14. GlyTJtograptus amplexicaulis (Hall). Limestone in the Maravillas chert, 0.8 mile east-southeast of B. M. 4361, southwest portion of Hess Canyon quadrangle north of Marathon, Texas. R. E. King, collector. United States National Museum No. 85358. 15. Diplograptus dentatus Hall. Woods Hollow shale near Louis Granger ranch south of Marathon, Texas. Hosterman and Baker, collectors. 16. Climacograptu,s antiquus Lapworth. Limestone of the Maravillas chert, O.75 miles east of Skinner's gate and 3 miles northeast of Marathon, Texas, on the Fort Stockton road. R. E. King, collector. United States National Museum No. 85364. Figures­ 17-18. Diplograptus angusti/olias (Hall). Woods Hollow shale. The Soli­tario, Presidio County, Texas. Baker and Sellards, collectors. 19. Glossograptus quadrimucronatus (Hall) var. angustus Ruedemann, n. var. Limestone in the Maravillas chert, 0.75 miles east of Skinner's gate and 3 miles northeast of Marathon, Texas, on the Fort Stockton road. R. E. King, collector. · United States National Museum No. 85365. Description : A well-marked variety of G. quadrimucronatus. The dis­ tinguishing character exhibited by all specimens in the collection is the slenderness of the long rhabdosomes, which, beginning with a width of 0.5 mm., widen very gradually to a maximum width of 2.6 mm. Specimens over 5 cm. in length do not exceed this width, while in the typi.cal form the maximurn width of 3 mm. is attained close to the sicular end. The thecae and apertural spines are of the char· acter and type of the species and the thecae number 8 to 9 in 10 mm. JO JI 18 19 17 14 2_ --· ' ' ·­ z • 4 s 7 9 ~ _..__., ' .. ' '.-­' 'º 11 IZ a 15 t> 13 I<\­ The Geology of Texas-Paleozoic Systems 237 PLATE V PENNSYLVANIAN AND PERMIAN FUSULINIDS Figures­1-3·. Schwr<"~rina gigantea M. P. White, Wolfcamp formation. (After M. P. White.) l. Axial section, X 3.8. 2. Median section, X 4.2. 3. Adult specimen, X 6.5. 4--6. Schwagerina sp., Moran formation, about 70 feet below the Sedwick limestone. (After G. G. Henderson, MS.) 7-9. Triticites moorei Dunbar and Condra, Graham formation, 1 mile west of Graham. (After M. P. White.) 7. Axial section, X 7.5 8. Median section, X 15. 9. Adult specimens, X 2.5. 10--12. Triticites irregularis (Schellwien and Staff), Brownwood shale, Graford formation. (After M. P. White.) 10. Axial section, X 6.5 11. Median section, X 15. 12. Adult specimens, X 2.5. 13-15. Fusulina meeki (Dunbar and Condra) var. similis (Galloway and M. P. White) n. var. (MS. ), Gordon limestone, Millsap Lake formation. 13. Axial section, X 14 (photo by M. P. White). 14. Median section, X 14 (after M. P. White). 15. Adult specimens, X 2.5 (after M. P. White). Fusulinids are known in the Texas forrnations from the Pennsylvanian and Permian forrnations. Those shown in Plate V illustrate severa! stages in the development of the group. The earliest species known, not illustrated on this plate, are found near the hase of the Marhle Falls formation and are very minute in size. Description of the two species ohtained at that level will he found in University of Texas Bulletin No. 3101, 1931. The. earliest fusulinid illustrated on this plate, Fusulina meeki, Figures 13-15, is limited to the Millsap Lake forrnation. This species is srnall in size and has a narrow . tunnel angle. The genus Triticites. illustrated by Figures 7-12, ranges from the Mineral W ells forrnation of the Strawn group to the Perrnian. The species of this genus are elongate or spindle-shaped. Triticites irregularis, Figures ] 0--12, is characteristic of the Canyon !O'OUp. The species of this genus are elongate or spindle-shaped and have a wide tunnel angle. In the Moran forrna­ tion, at or near the leve! of the Horse Creek lirnestone, G. G. Henderson has obtained ¡!'radational forrns frorn Triticites to Sckwagerina. Sorne of the fusu­1inids of this horizon are typical Triticites; 'Sorne apparently true Sckwagerina (Figures 4--0): and sorne interrnediate hetween these two genera .. Sckwagerina froni the Wolfcarnp forrnation is illustrated by Figures 1-3. Ali specimens illustrated are frorn Texas. · PLATE VI PENNSYLVANIAN AND PERMIAN AMMONITES Figures­1-3. Perrinites hilli (Smith), Double Mountain formation. l. Side view of holotype, X .35, Salt Croton Creek, Kent County. 2. Youthful specimen, showing relatively larger umbilicus,, X .65, same locality as holotype. S. Mature suture at whorl diameter 90 mm. 4. Perrinites compressus Bose, X 1.6, lower Leonard formation 2 milesc west-northwest of Wolf Camp, Brewster County; suture at whorl diameter 40 mm. 5-7. Perrinites cumminsi (C. A. White), Clyde formation. 5. Side view, X .65, 3 miles south of Electra, Wichita County. 6. Ventral view (after C. A. White), X .65, Military Crossing on. Wichita River, Baylor County. 7. Mature suture at whorl diameter 50 mm. 8--10. Perrinites biisei Plummer and Scott, n. sp. (MS.), Admira! forma-­tion, 5 miles southwest of Coleman, Coleman County. 8. Side view, X .65. 9. Ventral view, X .65. 10. Mature suture at whorl diameter 30 mm. 11-B. Shumardites simondsi Smith, Graham formation. 11. Side view of type (after Smith), X .65, Salt Creek 1 mile· west of Graham, Young County. 12. Ventral view, X .65, Hí miles due east of Fife, McCulloch_ County. 13. Very mature suture at whorl diameter 75 mm. 14--15. Shumardites fornicatus Plummer and Scott, n. sp. (MS.), Graforú formation. 14. Side view, X .65; 5 miles west-southwest of Bridgeport, Wise County. 15. Mature suture at whorl diameter 22 mm. 16. Shumardites sellardsi Plummer and Scott, n. sp. (MS.), Gaptank for-­mation south of Gap Tank, Brewster County; suture at diameter ap­proximately 65 mm. (specimen incomplete). 17-18. Paralegoceras iowense (Meek and Worthen), lower Strawn group. 17. Side view of holotype, X .22, Alpine, Iowa. 18. Suture at whorl diameter 10'3 mm. 19. Gastrioceras sp., X .65, Bend group, 5 miles southwest of Lampasas, Lampasas County. 20. Gastrioceras sp., X 1.6, Smithwick shale. The figures illustrate a typical phylogenetic series of ammonites that lived during the Pennsylvanian and Perfnian periods. These evolved with sufficient rapidity so that species from one zone can be distinguished easily from those of overlying and underlying zones by the character of the suture line, which be­came more complex as the phyllum evolved. Species from the lower Marble Falls (fig. 19) have one lateral lobe; those from the lower Strawn (figs. 17, 18) have three ; those from the Canyon and lower Cisco groups, four. In the upper Cisco the lobes develop subdivisions and become increasingly complex through the Permian (figs. 7, 10). Ali specimens illustrated, except those of Figures 17-18, are from Texas. 14­ 16 17 19 IS 20 PART 2 THE MESOZOIC SYSTEMS IN TEXAS W. S. ADKINS During the Mesozoic era rocks were deposited in Texas in three periods, the rock systems in ascending order being Triassic, Jurassic, and Cretaceous. Based on the lead ratio of radioactive minerals, the following numbers of millions of years have been assigned (947a, p. 49) to these three rock systems : Upper Cretaceous ---------------------------------------------------------------33.8 Lower Cretaceous -------------------------------------------------------------23.4 Jurassic -------------------------------------------------------------------14.3 Triassic ________ -------------------------------------------------------------------13.7 The length of time from the close of the Mesozoic to the present is given as 60 million years. Triassic sediments occur in Texas over a wide area, including most of the Llano Estacado and parts of Pecos, Crockett, Upton, Reagan, and Glasscock counties. These beds are entirely non-marine and represent possibly less than the upper one-third (Keuper) of Triassic time. Jurassic deposits are known in Texas only in a Testricted area of a few square miles near Torcer (Malone Moun­ tain), Hudspeth County. These beds are marine and represent only a small portion of Upper Jurassic (Kimmeridgian and ?Tithonian). No Morrison or other non-marine Jurassic is yet known with certainty in Texas. The Cretaceous is extensively and rather fully developed in Texas. It was probably deposited over most of Texas, and its remaining outcrops cover nearly one-third of the state. The following new or emended names for stratigraphic units are used in the Mesozoic portion (part 2) of this bulletin: PACE Malone formation, restricted (Upper Jurassic) -------------------------------------------254 Comanche series, emended (Lower Cretaceous) _______________________ __ _________________272 Trinity group, emended (Lower Cretaceous) _____________________________ _______________284 Torcer formaiion (Lower Cretaceous) -------------------------------------------------------286 Cedar Park member (Lower Cretaceous) ______________________ ____ ____________ __ ___..331 Pepper formation (Upper Cretaceous) -----------------------------------------------417 Tarrant formation (Upper Cretaceous) --------------------------------------------------425 Britton formation (Upper Cretaceousl -------------------------------------------------~5 Arcadia Park formation (Upper Cretaceous) ___________________ __________________________425 Chispa Summit formation (Upper Cretaceous) _______________ ___________________426, 437 Colquitt formation (Upper Cretaceousl -----------------------------------------------441, 452 llurditt formation (Upper Cretaceous) _______________________________ ________________449 Neylandville formation (Upper Cretaceous) ______________________________________488, 516 Corsicana formation, restricted (Upper Cretaceous) ________ ______________488, 516 Aguja formation (Upper Cretaceous) ----------------------------------------------------505 Approximate maximum thicknesses of these Mesozoic rocks in Texas are; Triassic, 2200 feet; Jurassic, 580 feet; Cretaceous, 15,500 feet. TABLE OF MESOZOIC ROCKS IN TEXAS European, stages CRETACEOUS { Gulf series (~arine) ___:_____________Cenoma~i~n to Maestricht~an Comanche senes (marme) __________Valangmian to Cenomaman, JURASSIC Malone formation, restricted (mostly marine) ----------------------------------------------Kimmeridgian and ?Tithonian·. TRIASSIC Dockum group (non-marine) __________________________________________Keuper TRIASSIC SYSTEM The Triassic Pacific sea covered considerable areas west of the­present Rocky Mountains and extended southwards across central Mexico, but never reached farther east toward Texas than central Arizona. The Texas Triassic1 is entirely non-marine, and is part of an eastward extension of red beds deposited in Arizona and New Mexico. In Texas these red beds and other materials are­comprised in the "Dockum beds" of Cummins, and in certain parts of western Texas the lithologic portions of the DockunÍ have received·. separate formation naines. Triassic outcrops in Texas are almost entirely confined to the Llano Estacado,. or Staked Plains; a plains area occupying the Panhandle of Texas and pait of eastern New Mexico. The Llano Estacado is bounded on the east by 11! prominent escarpment, the "edge" or "break" of the Plains, on the west by an· escarpment lying east of the Pecos and parallel to it, and on the north and: south by an indefinite boundary. The escarpments contain the main Triassic· outcrops and, south of Lat. 33º, the overlying Comanche rocks. The body of the Llano Estacado inside the escarpment boundary, is probably a wide. 1Literall.l.re.-Panhandle: Cummins, 340, 342, 343; Darton, 395; Baker, 42, 43, 52. Northern Panhandle: Bak.er, 42; Cate, 216; Drake, 448; Gould, 615; Patton, 1180. Southern. Panhandle:­Adams, 7 ; Blanchard, 122; Dumble and Cummina, 467; Hoots, 841; Liddle, 991. Oklahoma·New Mexico-A.rizona: Darton, 395; Lee, 978; Bullard, 175; Darton, · A réeumé of Arizona aeoloer.. Univ. Ariz. Bull. 119, 1925. Rothrock, Okla. Bull. 34, 1925. Pal•ontology: Braneon, 147; Cue, 224; 225, 226, 228, 229, 230, 231, 232, 233, 234, 235, 236; Cope, 306, 314, pp. 11-17; Reeolde, 1292b; Simpson, 1487; Cope, A contribution to the history of the vertebra ta of the Tria1 of North America, Proc. Amer. Phil. Soc., 24: 20~228, pls. 1-11, 1887. Mexico: Burckhardt, 181; Burckhardt, Inst. Geol. Mexico, Bol. 21, 1902. Burckhardt, Soc. Sel. Ant. Alzate, 41 :189, 1923. Kellar Ecl. geol. Helv. 21 :327. 1928; Jaworski, Elne Liu-Fauna au1 Nordweat-Mexiko, Ahh. achweiz. pal. Ges., 48 :1-12, 1 pl., 1929; Frech, Ueber Aviculide.n von palaeoroiscbem HabitU.1 au1 der Triaa von Zacatecaa, 10 pp.,_ 2 pls., Mexico, 1906. Triauic fi1Mi: Case, 225; Warthin, 1710. Fou.nal summarr: . Von Huebne, 858a; von Huebne, Neue Beitraco sur lCenntnll der Parasuchier : Jb. preun. geol. Landes11.nst. (íor 1921) 42: 49-160, 1922; von Huehne, Die foHile Reptil·Ordnung Sauriachia, ihre Entwicklung nnd Ge.chicbte, 2 pll., 360 pp.; 41 &c., 56 pi., Berlin, 1932. Limiu of Triauic: Rotb, 1353c. . . The Geology of Texas-Mesozoic Systems 241 shallow syncline in the Permian. This surface was beveled in pre-Dockum times, the weathered surface being a part of the Wichita Paleoplain. On it the Dockum beds were deposited. They now dip gently to the southeast. They were covered by rocks of the Comanche series, which were later removed from much of the northern Llano Estacado, and over much of the Llano Estacado by Dakota, now largely removed. In Cenozoic times a grave! mantle covered most of the area. Dips in the Triassic beds in Texas depend in part on local structure, and at severa! places southeast dips have been recorded, as in the following publications: Locality Direction Amount Drake (448) Llano Estacado SE 8 ft./mi. Drake (448) Potter, Oldham cos. SE 15-18 Baker (42, p. 19) Llano Estacado SE Dumble and Cummins (467, p. 350) Double Mountain SE slight Patton (1180, pl. IX) Potter County NNE? Adams (7, p. 7) states that the Dockum beds were deposited in a basin which underwent folding both before and after the Triassic deposition, and intimates (7, fig. 2) that the Dockum beds dip toward the axis of this basin. "In the southern Triassic area, the dip of the beds is very irregular because of the lenticular nature of the strata, which were laid down as river channel and flood plain deposits. The regional dip, measured on the top of the Santa Rosa, is toward the center of the Llano Estacado. This suggests that the downwarping of the Permian basin continued into the lower Mesozoic, and also that the western margin of the basin was elevated with the upfolding of the Front range" (Adams, personal communication). Western marine Triassic.-A rather full section of the marine Triassic above the Meekoceras zone is known in northern California and central Nevada. In Utah, ldaho, and Wyoming, considerable sections of marine lower and middle Triassic, including the basal Otoceras zone (in the Woodside formation), are known. Here, and in southwestern Colorado, northern Arizona, northern New Mexico, and the Llano Estacado in Texas, the upper Triassic, known vari­ously as Jelm, Popo Agie, Ankareh, Dolores, Chinle, and Dockum, is non-marine. In Arizona and New Mexico, the lower Triassic Moenkopi, containing Meekoceras near its base, is in part marine. In Zacatecas2 and Sonora,ª marine upper Triassic (Carnic, Noric) 2Burckhardt, C., La !aune marine du Trias aupérieur de Zacatecas. Inst. Geol. Mexico Bol. 21, 1902. ªBurckhardt, C., Quelques remarques critiques aur rouvrage de M. W. Freudenberg, "Geologie von Mexico,'" Soc. Sci. Antonio Alzate, vo]. 41, p. 189, 1923. Keller, W. T .. Stratigraphische Beobachtungen in Sonora (Nordwest Mexico) Ecl. geol. Helv., vol. 21, 327-335, 1 map, 1928. occurs; these and the Moenkopi are the known marine occurrences nearest to Texas. Economic Products: Glass sand is known in the Triassic from the Trujillo formation (1180, pp. 105-107). Sorne clays from the Tecovas suitable for certain grades of tile and brick have been tested (1180, pp. 108-109). Gravels, sands and hard sandstones from the Triassic can be used for road metal. Near the outcrop severa! Triassic sands bear fresh water. DOCKUM GROUP Nomenclature.-The entire known Triassic in Texas, non-marine and probably Upper Triassic in age, is included in the Dockum group. Cummins, in 1890 (340, p. 189), described and named the "Dockum beds" (type locality, Dockum, western Dickens County, Texas), and in a second report (342, pp. 424-431) stated their age as Triassic. Drake (448, pp. 227-247) studied and correlated the Triassic along a section from Big Spring northwards to near Amarillo, and thence westwards to near Tucumcari, and subdivided it into three units. Hoots (841) and Adams (7) later made studies near the southern end of Drake's section. At the northern end of Drake's section in Oldham and Potter counties where Drake's upper shale member is absent, Gould ( 615) subdivided the Dockum beds into two formations: a basal shale (Tecovas; type locality, Tecovas Creek, western Potter County), and an upper sandstone and shale (Trujillo; type locality, Trujillo Creek, western Oldham County). These formational differences, as well as other stratigraphic names (Barstow, Quito, Camp Springs, Dripping Springs, Taylor), indi­cate local lithological variations in non-marine deposits. Stratigraphy and Contacts.-Dockum beds in Texas overlie Per­mian formations at all points, unconformably according to most observers. The main evidences for unconformity are: . (a} the Dockum is Upper Triassic (Keuper) and the area apparently was not receiving deposits in the Lower and Middle Triassic; (b) there is a discordance in dip between Permian and Triassic; and (c) unconformities are visible at many places. Baker (42, p. 19) says: "An unconformity between the two formations (Permian and Triassic) is denoted by a slight difference in dip, which in the Triassic is nearly always in a southeasterly direction, and is gen­erally less than the dip of the Permian. On the east side of the Llano The Geology of Texas-Mesozoic Systems 243 the dips of the two formations are in opposite directions. In many places, but not everywhere, there is a pronounced erosion uncon· formity between the Permian and the Triassic." Gould (615, p. 21) records that locally on Trujillo Creek the upper red shales of the Quartermaster (Permian) have been removed down to the Alibates dolomite lentil, and that throughout the region, although very little Permian has been subsequently removed, the Triassic líes uncon· formably upon it. However, there are no fossils near the contact, the beds on both sides of it are in general similar ( except for sorne color differences) , and sorne writers have stressed the gradational appearance of the boundary. Thus Case (228, p. 9) states that he has repeatedly crossed the boundary in every county in Texas where it occurs, and has been unable to draw any line that can he used to separate the two formations. The Triassic red beds are more shaly than those of the Permian, and in general contain sorne gypsum, which may occur in beds of from a few inches to as much as 3 feet thick, or may be in the form of fine seams running in all directions through the red sandy clay. From the Canadian Valley south to beyond Big Spring the intermediate beds are capped by a grit and conglomerate, which is at most places overlain by Tertiary deposits with well rounded quartz pebbles. The Dockum beds in Texas are unconformably overlain by Comanchean or Cenozoic. In northeastern New Mexico and in the western part of the Oklahoma Panhandle they are generally over­lain by Wingate (Jurassic) sandstone or by Morrison beds (Upper Jurassic). Subdivisions.-Correlations of the Texas Triassic are attended with many difficulties. In the absence of zonal fossils, criteria used for correlation have been mainly stratigraphic and lithologic. The proposed units of the Triassic in Texas may be arranged as fol. lows: Eastern Southern Panhandle Central Northern New Mexico (Darton, (Adams, 7) Hoots (841) Panhandle (Drake, 448) Panhandle (Gould, 615) 395) Chinle shales Chinle shales Upperred elay Sandyclay, (thin or some sandstone absent) "Santa Rosa" "Santa Rosa" Basal red Sandstone and Trujillo sandstone sandstone clayand conglomera te, sandstone sandstone some clay and shale (generally absent) Basal shales (generally absent) Sandy clay Tecovas basal shale Roth ( 1353c) has proposed that his Custer formation, with ma­terial formerly considered the upper part of the remaining Permian be considered lower Triassic. A portion of his proposed correlation follows: Grand Southeastern Central-northern Canyon New Mexico Texas (Panhandle) Upper Chinle D k [ Chinle Dockum [ Trujillo (Keuper) Shinarump oc ·um S t an a Rosa Tecovas Camp Spring cgl. Middle (Musohel-absent absent absent kalk) Lower Moenkopi Red beds Upp~ [ C~•~1(Bunter) Rustler Double Castile Mtn. Channel ss. locally at base Mode of deposition: Darton4 states that there is no evidence that the Dockum beds are in any part marine, and that they are prob­ably deposits of the flood-plain or braided stream type, somewhat like the Great Plains formation. Presumably the Llano Estacado in lower and middle Triassic times was an area of denudation, and became markedly a plain of aggradation only during Dockum (upper Triassic) time. The extent of lake deposits, if any, in the Dockum beds is still an open question. Baker (42, p. 14) considers that the Dockum beds represent "deposits laid clown on a land surface, mainly by rivers." Lee (978, p. 10) states that, in the later Triassic, "sorne change in the relation of highlands and lowlands was effected, which caused the streams to spread out, over a wide area, the sand, grave!, and mud of the Shinarump conglomerate and other rocks of late Triassic age, both west and east of the mountains." Case (228, pp. 10-11) states that "the more uniformly deposited beds of clay and shale were apparently laid down in deep water or in water far from the shores; it is only in the disturbed beds, which bear evidence of having been deposited by great flood washes, that the remains of animals and plants have been found." The Tecovas clays generally lack fossils, except wood; the Trujillo sands and conglomerates contain vertebrate and molluscan remains. "lt is only in the irregular heds which were deposited in stream channels and local pools that any remains are 'Personal communication. The Geology of Texas-Mesozoic Systems 245 found" (Case). For conditions of deposition, see also: Hoots, 841, pp. 125-126, and Branson, 147. Source of materials.-From the supposed location of Triassic shore lines and from the regional thickening and size gradation of the conglomerates, it has been assumed that the source of supply of the non-marine Triassic in New Mexico and Texas centered around south-central Colorado. The Triassic in Texas thickens and coarsens toward the northwest. Baker has supposed that the coarse micaceous sandstones and conglomerates, composed generally of smooth, water-worn quartz, granite and limestone pebbles, may have originated from the Rocky Mountains or from the Wichita Mountains in Oklahoma. The Triassic red clay and clay-ball con­glomerate likely carne from the underlying Permian. In contrast to a northwestern source of materials in the Dockum beds in the northern Llano Estacado as supposed by Baker, Adams says that "in the southern areas in Texas an eastern and southern source appears more probable. The coarseness of materials on the east side of the basin compared with the center suggests an eastern source for the material, possibly from the exposed Pennsylvanian conglomerates. The Triassic gravels were possibly reworked from the exposed edges of the Pennsylvanian and Permian beds or from the same source as to the older gravels" (personal communication). Lithology.-Adams has summarized the more usual and striking lithologic features of the Triassic as contrasted with the Permian in the southern area. Among the more useful are the poor lithifica· tion of Triassic shales as compared to the hardness and compactness of Permian shales, the heterogeneous sandstones of the Triassic as compared to the very fine sandstones of the Permian, and the presence of bones, grave}, limonitized and silicified wood, and abundant mica in the Triassic. Bedded anhydrite and salt occur in the Permian, gypsum and anhydrite occur in the Triassic in only minor amounts. Beds of very fine sandstone are rare in the Triassic, common in the upper Permian. Uncolored, well rounded, frosted quartz grains are common in the Permian; colored, sub­rounded, partially frosted quartz grains generally distinguish the Triassic. The clastic sediments of the Triassic are more heterogene· ous than in most Permian formations, and subangular gravel, ranging from fine to coarse, is common in the Triassic. The ahundance of water sands, mica, phosphate, limestone, and cal­careous • shale and sandstone is generally more indicative of the Triassic. Marine fossils, detrital limestone and Chara oogonia are more indicative of the Comanche series. The deep maroon color characteristic of the southern Triassic shales is very rare in the Permian. Impalpable shales, common in the Triassic, are very uncommon in the Douhle Mountain (Permian) heds (Adams, personal communication). In the northern Panhandle, color distinctions seem more valuahle than in the Pecos Valley region. The color features of the Tecovas and Trujillo have already heen mentioned. Baker lists the following as the more characteristic features of the Triassic: mica, con­glomerate, color of sandstones (gray, hrown), color of shales (variegated, in contrast to the hrick-red of the upper Permian), extensive cross-bedding, and unconformities. Certain reptilian bones and species of Unio mark the Triassic. Paleontology.-(a) Invertehrates are lwited to Unios, so poorly preserved as to he specifically indeterminable. Four species have heen descrihed from Dickens and Garza counties (Simpson, 1487; see also Reeside, 1292b) . (h) Fossil wood was found to have heen so hadly rotted hefore fossilization and so deeply impregnated with gypsum as to destroy the cell structure (228, p. 8). Locally lignite occurs. ( c) Vertehrates have heen studied hy Cope, Case, Branson, Mehl and others. The reptiles Phytosauria, dinosaurs, Parasuchians ( croc­odiles); amphihians (Stegocephalia); a fish (Ceratodus dorotheae Case, 225) ; and other forms have heen descrihed from the Dockum heds or their equivalents. Most of these fossils are restricted to the Triassic, hut their value for minute zonation is unknown. No marine invertehrates are recorded from the Texas Triassic, hut the lower Triassic (Moenkopi) in Arizona contains Meekoceras and other mollusca. The Geology of Texas-Mesozoic Systems 247 Some Fossil Vertebrata from the Western Triassic (Species described from Dockum beds indicated by•) Ceratodus crosbiensis Warthin (1710). Ceratodus dorotheae Case (225) • Macropoma sp. Warthin (1710) • Metoposaurus jonesi Case* Metoposaurus fraasi Lucas Buettneria perfecta Case* Buettneria bakeri Case• Typothorax coccinarum Cope Eupelor sp. Cope• Desmatosuchus spurensis Case• (224, 226) Coelophysis sp. (230, 231) Phytosaurus doughtyi Case Machaeroprosopus andersoni Mehl Ptomystriosuchus ehlersi Case• Leptosuchus crosbiensis Case* Leptosuchus imperfectus Case• Dinosaurs, indet. Case* Cf. Phytosaurus sp. Case (232) • Palaeoctonus cf. P. orthodon Cope• Palaeoctonus dumblianus Cope* Episcoposaurus haplocerus Cope Belodon superciliosus Cope• Clepsysaurus sp. Cope* Mollusca described from Dockum beds Unio subplanatus Simpson• Unio dockumensis Simpson• Unio dumblei Simpson* Unio graciliratus Simpson• Thickness and Dip.-In the southem Llano Estacado the general Triassic dip is to the southeast, averaging 8 feet per mile. In Old­ham and Potter counties it is 15-18+ feet per mile. The outcrop thicknesses are less than those preserved in the central syncline of the Llano Estacado, where as much as 1200 feet has been recorded. The following are sorne recorded Triassic thicknesses in west Texas: Feet Eastern Randall County _____ 400 Potter County (average) __ 225 Western Oldham County____ 135 Eastern Howard County-----500-600 Feet Southeastern Crane County_ 95+ Southern area --------450± Midland County (Bryant well) 1200? Martin County (Wolcott well) 1100? Mr. J. E. Adams has very kindly supplied the following approxi­mate thickness of the Triassic in Texas: Feet Andrews County (central)­Deep Rock 1, Kuykendall __l520 Bailey County (western)­Humble 1, Fuqua______2l60 Cochran County (central)­Penn 1, Slaughter __--2125 Crockett County- Magnolia 1, Hoover (central)_ 210 Powell pool (north-central) __ 320 Crane County-McElroy pool (eastern) __ 690 Waddell pool (northern)____ 850 Dawson County (eastern)­ Magnolia 1, Jeter____________l290 Feet Ector County-Judkins pool (south-central)_ 730 Exploration 1, Slater (west­ central) ----------1280 Stanolind 2. Cowden (north­ ern) ___________1590 F1oyd County (western)­Exploration 1, Boone ______ 760 Gaines County (southwestern)­Humble 1, Carswell. ___1480 Garza County-Gulf 1, Slaughter (southwest· ern) ___________ 620 Marland 1, Pippin (north­western) ---------560 Feet Feet White Eagle 1, Dunbar (south­Thraves 1, Sanders (eastern) _ 400 central) ------------------------585 Pecos County- y ates pool ______________________________35-65 California 1, Settles, Settles pool (northern) ___________________ 840 Vacuum.. Elsinore -------------------225 Penn 1, Habenstriet (western) 840 Phillips 1, Pryor (northwest-Hale County (northern)-ern) ----------------------------------340 Exploration 1, Goodman_______l 260 Phillips 1, Nutt (24 mi. NE. Howard County-Ft. Stockton) -------------------140 Sinclair 1, Dodge (eastern) ____ 715 Dixie 1, Hershenson (western) 210 California 1, Fisher (central) __ l 715 · Sun 1, University (SE. of Tay­ Phillips 1, Thomas (north-lor-Link pool) -------------------2.90 central) ------------------------------800 Terry County (northeastern)- Marland 1, Quinn (western) ____ 865 Penn 1, Carlysle__________________2230+ Irion County (northwestern)­Upton County- Fuluman 3, Sugg -------------------220 Shell, Halamiceke (central) ....1135 Lamb County (eastern)-Atlantic 1, Live Stock Ex- Graham 1, Elwood __________ _____1405 change (eastern) ____________________.1000 Martín County (northern) -Winkler County- Phillips 1, Slaughter_________ ______l330 Llano 1, Scarbrough (north-Midland County (southeastern) -ern) -------------------------------------725 Pure 1, Hutt_________________________l215 Llano and McCamey 1, Cow-Mitchell County-den (eastern) --------------------900 Foster pool -----------------------950 Yoakum County (southwestern)­ Westbrook pool _____:______ 450 Weekly 1, Knight____________ l860 AREAL GEOLOGY Contacts.-The Dockum beds overlie Permian strata at practically ali points on the Texas outcrop and in wells. The Permian was generally eroded and beveled before the deposition of the Triassic so that the Triassic rests on a heveled Permian surface, the strata of which range in age from basal Double Mountain to the local top of the Permian. The Triassic is unconformably overlain by marine Comanche series or by non-marine Cenozoic. The Dockum beds underlie practically the entire Llano Estacado south of the Canadian River valley, and probably extend, at least sporadically, farther north, for they occur in .the Cimarron and North Canadian valleys in the Oklahoma Panhandle.5 They out­crop in the east and west escarpments of the Llano Estacado, in outliers such as Pouble Mountain, and in the deep valleys cutting into and across the Plains; on the main body of the Llano Estacado they are folded in a syncline and buried beneath Cenozoic sands and gravels, or south of Lat. 33°, beneath Lower Cretaceous. Farther east they are unknown; and the eastward limit of their deposition is unknown. In eastern New Mexico, east of the Pecos •Kansa1 Geological Society, fourth Annual Field Conference, general geological map, 1931 ; Rothrock, Okla. Geol. Surv., Bull. 34, 1925. The Geology of Texas-Mesozoic Systems 249 and south of the Canadian, the Triassic has extensive outcrops; and westward it thickens into Arizona and the basal formation (Moen· kopi) becomes in part marine. Darton (395, p. 32) considers the Lobo formation, red and gray shales, pinkish limestone, and con· glomerates, in the Deming area, as possibly Triassic. SOUTHERN LLANO ESTACADO In southeastern New Mexico the Triassic is stated to be composed of (a) a basal shale; (b) a medial sandstone (Santa Rosa); and (e) an upper shale. The basal shale disappears south of the Canadian Valley, leaving the medial Santa Rosa sandstone resting directly on the Permian. Adams (7, p. 1052) adopts the name Santa Rosa6 for the medial sandstone and the name Chinle7 for the upper shale, which he states disappears in the southern part of the Texas Triassic area, leaving the Santa Rosa as the sole repre· sentative of the Triassic in Pecos, Crockett, Irion, Sterling, Mitchell, Scurry, Fisher, Nolan and Coke counties. Hoots (841, pp. 86-96) in describing the same area, divides the Dockum beds into (a) basal red clay with numerous gray sandstone seams (275--feet); (b) upper red clay (maximum 175 feet). These may correspond to Adams' Santa Rosa and Chinle respectively, assuming that the sandstones and conglomerates are more segregated in one part of the section. Locally in. this area the basal Triassic seems to consist of red clay. At other places a basal Triassic conglomerate is called Camp Springs (type locality, Camp Springs, near the center of the east line of Scurry County) by Beede and Christner (97, pp. 16-17). Also the upper red clay locally contains sorne sandstones. In the southern area, Drake considered his three divisions to be present, but the basal shale is absent in many sections, as noted by Hoots, Adams, and others. The Santa Rosa can be traced from New Mexico southeastward into this area. At Red Point, south­eastern Crane County, Hoots records about 95 feet of Dockum beds, consisting mostly of cross-bedded and partly micaceous sandstones, light gray, light brown, grayish-brown, light red, red and green streaked, with sorne red and light brownish-red sandy clay, and a little conglomerate containing rounded quartz pebbles. In north­eastern Loving County and in W ard County, according to Hoots, 'Deacribed from near . Santa Rosa, N. M., by N. H. Darton, U. S. G. S., Bull. 726-E, p. 183. The name ie preoccupied by Santa Rosa of Dollfuas and Montserrat, 1868, from Nicaragua. •Deacribed from Arizona by H. E. Gregory, U. S. G. S., P.P. 93, p. 42, 1917. the lower Dockurn consists of 40-50 feet of the rnain sandstone ( quarried at Quito), which is red and gray, cross-bedded, and locally ripple-rnarked, underlain by sandy clay and sandstone. In eastern Howard County, Hoots gives a section of 283+ feet of Dockurn beds, about three-fourths being dark red clay, and one­fourth being light gray or gray-green sandstone with sorne con­glornerate containing fragments of gray lirnestones and pebbles up to 2 inches in diameter. In Scurry County, Hoots records at the top of the Dockum beds as much as 150 feet of dark red clay, only slightly sandy and with no bedding; and in Borden County, in addition, a small thickness of greenish-gray, cross-bedded, very rnicaceous sandstone. In these counties greenish-gray, micaceous, cross-bedded sandstone is common in the basal Dockum beds; and the top part consists largely of dark red clay with only sporadic sandstones. Farther west on the Pecos the sandstones seem more widely distributed in both base and top, and redder. They are massive, of mediurn texture, cernented with iron oxides, and inter­spersed with sorne thin conglornerate lenses. The outcrop reveals only a srnall portion of the Dockurn thickness, for in wells in Midland and Martin counties the Dockurn is thought to have a thick­ness up to 1200 feet, if all fresh-water sandstones are included, the greater part of this thickness being shale or sandy shale. In eastern Crosby County (216, p. 248) the Dockurn beds consist of thin bluish-green sandstone at the base, followed by about 130 feet of light brown, white, red, and rnaroon clays, capped by 5-20 feet of fine, cross-bedded conglomerate. The basal part of the clay con­tains Unios, vertebrates, and fossil plants. Thence northwards to the Canadian Valley, Drake records his upper shale as absent. The southern boundary of the Triassic occurs in part on the surface, in part underground. It is stated approximately to follow the east bank of the Pecos downstream from the New Mexico-Texas line, past Quito quarry to eastern Reeves and northern Pecos counties. It outcrops near Grandfalls, and occurs underground in northern Pecos County but is not now considered to be present under rnost of Reeves County. lt is absent in the Sierra Madera, crosses the Pecos near Sheffield, is present in the Yates (707) and Big Lake (1414) oil fields. Thence it passes northeast to north­eastern Sterling County, includes much of Mitchell, Scurry and Borden counties, and thence follows the scarp of the Llano Estacado The Geology of Texas-Mesozoic Systems 251 northward to the Canadian River valley. In the northern Texas Panhandle it is not exposed. Farther north the Triassic is exposed in the Cimarron Valley in Cimarron County, Oklahoma, where the section consists of Permian, Triassic, Jurassic (Morrison), basal Comanche, Dakota and Cenozoic; in this county 2000 feet of red beds of undetermined age is known, the exposed upper part being Triassic by correlation into New Mexico. CENTRAL LLANO ESTACADO Drake's (448) general section was carried from Signal Peak, 10 miles southeast of Big Spring, Howard County (section given by Hoots, 841, p. 106) , northwards through Amarillo to near Tucum­cari, New Mexico. He divided the Dockum into three parts: (a) lower sandy clay (maximum 150 feet); (b) medial sandstones, conglomerates and sorne clays (maximum 235 feet); (c) upper sandy clay and sorne sandstone (maximum 300 feet). Drake states that his lower clay thickens from Big Spring northwards along the eastern part of the Llano Estacado to Amarillo, and thence west­ward to Tucumcari. The medial sandstones (Santa Rosa of sorne authors) thicken to a maximum of 225 feet in Armstrong County, and thence westwards thin rapidly to 25 feet near Tucumcari. Near Amarillo they apparently form one bed. Drake's basal shale is apparently the same as Gould's Tecovas; Drake's medial sandstone the same as Gould's Trujillo (1180, pp. 48, 66-67). Drake's upper shale ( called Chinle by Adams), present in the southeastern Llano Estacado as far north as Garza County, is missing from Garza County northwestward to Oldham County, and thence westwards gradually thickens until at Tucumcari it reaches a thickness of 300 feet. The following table expresses these proposed equivalencies: Southern Central Canadian Valley Tucumcari Llano Estacado Llano Estacado in Texas region CHINLE Drake's upper (thin) (absent) (300 ft.) clay, thick TRUJILO Drake's medial (present) (present) (present) sandstone and conglomerates TECOVAS Drake's basal (thin) (65-115 ft.) (present) clay (thin) However, because of the irregular and lenticular deposition, the abo ve equivalences are by no means certain. NORTRERN LLANO ESTACADO In the northern section, including the Canadian Valley, Gould (615) divided the Dockum beds into two formations: basal part, largely shale, called the Tecovas formation; and upper part, including from one to five prominent sandstone ledges, the Trujillo formation. The Tecovas typically consists of two parts: (1) a basal member of vari-colored shales, including · generally a lower zone of white, gray or lavender, a middle zone of maroon or wine color, and an upper zone of light yellow or sulphur-yellow color (total 70-700 feet in Palo Duro Canyon, 15--40 feet along Canadian River) ; and (2) an upper magenta shale (120-150 feet in Palo Duro Canyon, 50-75 feet on Canadian River) . The brick-red color of the Quarter­master shale (Permian), the lavender, maroon, and yellow of the lower Tecovas variegated shales, and the magenta of the upper Tecovas, form a characteristic color contrast in this area. Locally the variegated shales are represented by a characteristic, soft, friable, massive, white, yellow or light brown sandstone weathering into distinctive rounded or dome-shaped masses. The Trujillo formation consists of one to five or more, but typically three, sandstone or conglomerate ledges with interbedded red and gray shales. On Trujillo Creek the section is as follows (216, p. 253): 4. Conglomerate, the pebbles variable in size and character; locally replaced by sandstone, occasionally by arkose; contains thin layers of clay and shale; generally grayish, but locally reddish; locally overlain by red sandstone. 3. Thin, blue, sandy clay. 2. Red clay, with sorne bine streaks, sorne calcareous material, and, near the bottom, shaly layers with worm casts (250 feet). l. Sandstones and shaly layers with Triassic bones. This layer can be traced westward to Tucumcari and Montoya. The lower sandstone (615, pp. 26-29) is 60-75 feet thick in Palo Duro Canyon, but only 25 feet thick on the Canadian; it is massive and resistant, and weathers into pedestal forms. Ahove a 15-60 foot bed of red or gray shale is the middle sandstone ledge, 10--40 feet thick. It is a coarse, heavy, cross-bedded, red or gray sandsto·ne, or a cross-bedded, lenticular conglomerate (pebbles of granite, quartz, sandstone, clay and limestone) with pockets and lenses of clay. Locally the ledge consists of small fragments of clay or The Geology of Texas-Mesozoic Systems 253 limestone imhedded in a matrix of sandy clay. At places where pre-Tertiary erosion has not cut so deep, there is a third upper sandstone-conglomerate ledge lithologically like the second (in Palo Duro Canyon 30 feet). The three sandstones locally are divided by clay partings or lenses; the upper two contain Triassic bones. Down the Canadian in Potter County (1180, pp. 66-77) the Trujillo is generally represented by one sandstone and con­glomerate ledge 10-25 feet thick or more. It contains fragments of bone and silicified wood. The Double Mountain outlier in southwestern Stonewall County has 35 feet of "purple, red and mottled sands which pass at the bottom into a conglomerate of bright-colored pebbles" (Dumble and Cummins, 467, p. 350). Similar pebbles occur throughout thé sands in nests, in strata, or singly. The formation lithologically resembles the Trujillo. It has a slight dip to the southeast. Subsurface extent.-Probably the entire Llano Estacado interior to the outcrop and south of the Canadian Valley is underlain by Dockum beds. These reach a thickness of as much as 1200 feet and are deposited generally in a broad, shallow syncline. JURASSIC SYSTEM The North American continent during the Jurassic, as during the Cretaceons period, was invaded by three seas: Pacific, Arctic, and Gulf. Only the last two concern Texas. A branch of the Arctic sea known as the Logan (Sundance, Argovian) Sea extended south­wards along the site of the Rocky Mountains to Colorado. In late Jurassic times, the non-marine Morrison formation was deposited in the dried-up bed of this sea and extended south of it to the north tip of the Texas Panhandle. The Gulf sea, advancing northwards along the southern extension of the Rocky Mountain geosyncline between the sites of Jurosonora and Jurolaurentia, covered parts of northern and central Mexico and reached as far as Malone Mountain, leaving deposits of upper Jurassic age in Texas over only a few square miles in Hudspeth County. Near the end of the Jurassic (Tithonian, "Lower Berriasian"), the continent had largely emerged and its southern shore was an irregular line in northern Mexico running from the tip of the Big Bend gulfwards and parallel to the Rio Grande. The Cretaceous seas transgressed northwards from this shore line (133a, 181, 334). In the following discussion the marine Jurassic Malone beds and the non-marine Morrison formation adjacent to Texas are· briefly reviewed. MARINE JURASSIC IN TEXAS MALONE FORMATION8 (restricted) Nomenclature.-Cragin (328,331) applied the name "Malone formation" to rocks of both upper Jurassic and lowermost Cre­taceous age, which outcrop near Malone (now Torcer) station on the Southern Pacific Railway, southwestern Hudspeth County, Texas. The name Malone, in accordance with Cragin's apparent intention, is here restricted to that portion of these rocks which is of Jurassic age. These beds are only a small terminal residue of Jurassic strata of much greater extent which were deposited in a northwardly narrowing arm of the Kimmeridge sea in north-central Mexico, and must be considered in relation to these more extensive Mexican deposits ( excellently reviewed by Burckhardt, 181). Stratigraphic position and conta,cts: The Malone beds rest uncon­formably u pon Permian strata ( 46, p. 11). Baker and Beede found Richthofenia in the limestone overlying the gypsum at a locality 1h mile north-northeast of Torcer station. Near Torcer they found about fifteen Permian species, including ammonoids, and in the conglomerate above the limestones, Iimestone boulders containing Fusulina elongata. Regarding the unconformity Baker says: The Permian gypsum ... is overlain by a heavy limestone and chert con· glomerate with brown chert as a part of the matrix-cementing materials. Boulders in the conglomerate are as large as 8 inches in diameter. Two of the limestone boulders contained Fusulina elongata. This conglomerate js apparently the basal bed of the Jurassic. Above come mainly limestones with sorne conglomerates and brown sandstones; the limestones locally ~ontain ~hert 8Literature.-Northern. Mexican Jurassic: Castillo and iAguilera, Fauna fosil de la Sierra de Catorce, San Luis Potosi. Com. Geol. Ma., Bol. l, 1895. Burckhardt, 181; BOse, l33a; Burck· hardt, La faune jurassique de Mazapil avec un eppendice sur les fossiles du crétaceque inférieur, lnst. Geol. Mexico, Bol. 23, 1906; Burckhardt Nuevos datos sobre el jurásico y el cretácico en México, Inst. Ceo!. Mexico, Parerg., 3: 281-301, 1910; Burckhardt, Neue Untersuchungen über Jura und Kreide in Mexiko, Centr. Min., 1910-: 622-631, 662-667; Burclchardt, Faunes jurassique1 et crétaciquea de San Pedro del Gallo, lnst. Ceo!. Me:r:ico, Bol. 29, 1912. Baker, C. L., General geology of Catorce míning district (San Luis Potosí, Mexico), Trans. A. l. M. E., 66:42­ 48, 1922. Malone beds: Baker, 46, 55; BOse, I33a; Burckhardt, 181; Cragin, 328, 331; Crick­ may, 334; Cillet, 586; Haug, 673; Kitchin, 944; Spath, 944; Stanton, 331; Tafi', 1573; Udden, 1652 ; Uhlig, 1674, 1674a. Dacqué, E. Die Stratigraphie des marinen Jura an den RS.ndern des Pazifischen Ozeans, Geol. Rundschau, 2 : 464-498, 1911. The Geology of Texas-Mesozoic Systems 255 pebbles. The gypsum here is apparently overlain on its eastern side with a southeastward-dipping brown sandstone with brecciated pebbles, upon which rests a blue limestone. The Malone formation, mostly of Kimmeridge age, is overlain, with an inferred unconformity, by Valanginian Cretaceous. Baker states that at the northwest end of Malone Mountain, near Briggs spur, the gypsum is overlain by about 200 feet of conglomerate and light brown conglomeratic sandstone, and above this by gray fossiliferous limestone with interbeds of light brown conglomeratic and quartzose sandstone, the pebbles of which are quartz and chert. In a sandstone near the top of this ridge Baker found an Astieria, indicating early Cretaceous age, but the amount of strata at this locality which are probably Jurassic has not been determined. Lithology.-The Malone Jurassic consists mostly of conglomerates, brown sandstones and limestones. The sandstones are in part con· glomeratic, with well rounded limestone and chert pebbles. Sorne of the limestones contain chert pebbles. The conglomerates contain pebbles of various materials, including limestone boulders. The section contains a subordinate amount of shale. Both lithology and position of the Malone in the narrow arm of the Jurassic sea indi­cate a near-shore facies. Fossils, Age, Correlation.-The age of these deposits has been dis­cussed by Stanton (331), Cragin (321), Burckhardt (181), Baker (46), Uhlig (1674), Kitchin (944), Bose (133a), Spath (944), Gillet ( 586), Haug ( 673), and others. Uhlig (1674, p. 69) says: "Of the ammonites of this fauna, Peri­sphinctes potosinus Castillo and Aguilera, P. felixi C. & A., and P. schucherti Cragin belong to Burckhardt's genus ldoceras, and P. aguilerai Cragin and P. clarki Cragin to the group of P. victoris Burckhardt or to the genus Kossmatia Uhlig." Kitchin (944, pp. 457-458) says: The Jurassic age of the ammonites described by Cragin cannot be questioned. The opinion of so eminent an authority as Uhlig should scarcely need confirma­tion, but in view of the mixed character of the described fauna, its partial misinterpretation by Cragin, and its discrepant indications of geological age, J have asked Dr. L. F. Spath if he can give a confirmatory opinion based on an examination of Cragin's figures of the ammonites. Dr. Spath kindly informs me that he sees nothing among the illustrations to suggest a Cretaceous age. He is able, in fact, to confirm Uhlig's reading, remarking that the predominant forms of ldoceras are certainly Middle Kimmeridgian, while "the Haploceras, 'Olcostephanus' (=Lithacoceras of what I called the cystettensis-/ructiccms gioup) and 'Aspidoceras' (Simaspidoceras?) may well be of the same age or Upper Kimmeridgian. The doubtful 'Perisphinctes aguilerai' could only be a little later, possihly even a Tithonian Kossmatia (pronus zone of my Somali­Iand zones) ." Thus ali the ammonites recorded from Malone, except Baker's Astieria, are Jurassic; and ali the Trigonias are Cretaceous. How­ever, it is to he noted that large, poorly preserved ammonites associated with Trigonia vyschetzkii and other Cretaceous fossils occur at the south end of Triple Hill in the flat east of Torcer station. The fossils at this locality are exclusively Cretaceous. /urassic in northern Mexico.-Recorded Mexican marine Jurassic localities nearest to Texas are: Placer de Guadalupe, Santo Domingo, Cuchillo Parado, Sierra Rica, San Marcos, Alamos, Monterrey-Saltillo, and Sierra de Cruillas (181, pp. 101, 266). In the Altar and Hermosillo districts, Sonora, crinoid fragments, sorne referred to the Oxfordian, have heen recorded (181, p. 82). Liassic has also heen recorded from Sonora.9 The following zonal parallels exist hetween northern Mexican localities and Malone in the upper Jurassic: Northern Mexico Malo ne TITHO IAN Steueroceras ("Lower Berriasian," Hoplites aff. Kollikeri Purbeckian) Kossmatia Kossmatia aguilerai Proniceras Aulacosphinctes PORTLA DIAN Mazapilites ? Waagenia Haploceras fialar Haploceras Lithacoceras KI 1MERIDGIAN Simaspidoceras? Idoceras Idoceras spp. ARGOVIA DIVESIA CALLOVIA The recent discovery in the Sierra de Cruillas southeast of Burgos and about 100 miles southwest of Brownsville, Texas, of upper Portlandian marls containing Kossmatia spp. (181, p. 266) makes it probable that Jurassic sediments underlie a part of the southern ªKeller, W. T., Stratigraphiscbe Beobachtungen in Sonora (Nordweat-Mexico), Ecl. geol., Helv .• 21; 327-336, one map, 1928. Jaworski, E., Eine Lias-Fauna aua Nordwe1t0 Mexiko, Abh. echweia. ~eol. Cea., 48: 1-12, one pla~e, 1 map, 1929. The Geology of Texas-Mesozoic Systems 257 Coastal Plain of Texas. No direct evidence of such strata has yet come to light in Texas. In deep wells in northern Louisiana, marls bearing foraminifera have been conjectured to be of Jurassic age, hut so far on insufficient grounds. Facies, Source of Material.-The Malone exposures are excep­tionally isolated in Texas; the nearest known marine Jurassic is near Cuchillo Parado on the Conchos, west-southwest of Presidio, though intervening exposures will doubtless come to light with further search. Here the Jurassic is comprised of Burrows' Plomosas formation bearing deposits of zinc, lead, and copper, and composed of 1150 feet of quartzites and limestone basally, a 60-foot con­glomerate medially, and superiorly shales and limestone. Probably in the mountain ranges west of Pilares other similar exposures will be found. The Malone section is even more marginal in character, as its frequent conglomerates attest. Besides, the upper part of the Malone section contains, alternating with marine sediments, beds containing fresh-water fossils, in the following sequence: ( 1) fresh­water limestone with Viviparus and Unio; (2) gray limestone with Kossmatia aguilerai (Cragin) of upper Portlandian (Tithonian) age; (3) conglomerate with chert and quartzite pebbles; (4) lime­stone with fresh-water fossils. At present there is no evidence that this arm of the Mexican Jurassic sea extended north of Malone Mountain. Baker ( 55) even suggests that the Malone mass was overthrust into Texas over the lubricating layer of Permian gypsum, from locations farther west in Chihuahua. NON.MARINE JURASSIC ADJACENT TO TEXAS The non-marine Upper Jurassic Morrison beds10 are mapped11 as extending eastwards beneath the northwestern margin of the Llano Estacado practically to the northwestern comer of Texas. They have never been reported from Texas, but the fact that they are lOLiterature.-Simpson, George Gaylord, The age of the Morrison formation, Am. Jour. Sci., (5) 12: 198-216, 1926. Simpson, George Gay lord: The Fauna of Quarry Nine. American Terrestrial Rhynchocephalia, A.m. Jour. Sci. (5) 12: 1-16, 1926. Schuchert, Charles, Age of the American Morrison formation and East African Tendaguru formations, Bull. Geol. Soc. Amer., 29: 245-280, 1918. "Morrison Symposium," Bull. Geol. Soc. Amer., 26: 295-348, 1915. Crickmay, C. H., 334, pp. 91-93. Kitchin, F. L., On the age of the Upper snd Middle Deinosauer-deposite at Tendaguru, Tanganyika Territory, Geol. Mag., 66: 193-220, 1929. Parkinson, John, The dinosaur in East Africa, 192 pp., Witherby, London, 1930. llMook, Charles Craig, A study of the Morrison formation, Ann. N. Y. Acad. Sci., 27: 39­191, pi. VI, 1916. Lee, Willis T., 978. 25.8 The University of Texas Bulletin No. ·3232 known_ in northeastern New Mexico12 and in Cimar~on County, Oklahoma,13 only a few miles from the Texas line, makes it appear possible that they will he found, perhaps with Upper Cretaceous formations, in synclines in the northern Llano Estacado. Recent field work by C. L. Baker has disclosed probable Mor­rison, Purgatoire, and Dakota outcrops in northern Dallam County, in the northwestem comer of Texas {compare Gould, 615, p. 30). Baker has kindly fumished the following notes on this area {see also page 283) : Rocks lithologically like the Morrison are exposed in a small trihutary o_f Spring Gully, near Buffalo Spring (XIT ranch head­quarters) , ahout 17 miles east of the northwest comer of Texas and Y2 mile south of the Texas-Oklahoma state line. Here there occur, interhedded with each other, dark hlue-gray mudstone stained pur­ple, and huff and yellow-green sandstone. The mudstone and the purple color suggest the Morrison as identified in northeastem New Mexico. At the head of a spring draw south of the ranch house and strati­graphicall y higher than the preceding beds, there_is a section of rocks weathering chalky cream color, the top 10 feet consisting of a wedge of limy, fine-grained fucoidal sandstone, hlue-gray when unweathered, containing shaly interheds; and the basal part con­sisting of cross-hedded, ripple-marked sandstone weathering a hrown to huff color, and containing small pehhles and seams of coarse grit. This section resemhles the Cheyenne sandstone; it is correlated with the Purgatoire of northeastern New Mexico. At a locality ahout 1 Y2 miles north of the XIT headquarters ranch house, Y2 mile north of the state line, and stratigraphically higher than the rocks described ahove, there occurs ahout 15 feet of Dakota in a small isolated knoh. It is a ferruginous, fine-grained, cross­bedded, quartzitic sandstone { cp. Gould, 615, p. 30) . In northeastem New Mexico, the Morrison thins eastwards to its last known outcrop in the Oklahoma Panhandle. The following thicknesses have heen recorded: Cuervo Hill, 20 miles northeast of Santa Rosa, 315 feet; Canadian escarpment, Carro Mesa, 90 lllJ)arton, N. H., 395, esp. pp. 300-307, and pi. 13-B. 18Lee, W. T., The Morrison abales of southem Colorado and northern New Mexico, Jour. Geol., 10: 43, 1902; Stanton, T. W., The Morrison formation and its relation1 with tho Comanche series and the Dakota formation, Iour. Geol., 13: 657-669, 1905; Rothrock, E. P., Geology of Cimarron County, Oklahoma, Okla. Geol. Surv., Bull. 34, pp. 31-36. Tke Geology of Texas-Mesozoic Systems 259 feet; west side Ute Valley below Gallegos, 65 feet; 3 miles south of Montoya, 100 feet; Mesa Rica 10 miles east of Isodore, 50 feet; Tucumcari Mountain, 20-30 feet; Cimarron County, Oklahoma, 80 feet. Ea:stwards down the Canadian V alley the Morrison outcrop is mappedt' as disappearing before reaching the western boundary of Texas. A careful study of Panhandle well samples will be necessary to discover whether any remnants of Morrison have been penetrated in this area. In Union County, New Mexico, the Morrison consists "mostly of typical light-colored clay or massive shale, in general pale greenish-gray with sorne rnaroon and hrown portions, and thin sandstone"; it unconformahl y overlies the Triassic Dockum beds and is about 360-375 feet thick (395, p. 306, fig. 144). Below the middle of the formation there occurs a conspicuous sandstone, correlated by Darton with Lee's Exeter sand­stone. Lee (978, p. 22) portrays the sandstone under the Purgatoire as thinning into northeastern New Mexico, where it is represented by the Exeter, apparently co.rrelated by him with the Wingate sand­ stone. Bones of the supposedly Jurassic dinosaur, Brontosaurus, have been recently recorded1ªª from a locality on highway 64, just east of Kenton, Cimarron County, Oklahoma. The bones, including the fifth and sixth left ribs, two caudal vertebrae and some fragments, were found near the top of the valley wall in dark brown, gray mottled shale referred to the Morrison. Brontosaurus has been recorded from the Morrison at Como Bluff (Mook, op. cit., p. 138). CRETACEOUS SYSTEM The Cretaceous is one of the most important rock systems in Texas, both areally and economically. Soon after the earliest settle­ment of the state, the main north-south trending Cretaceous belt in central Texas was found to possess many advantages of soil, climate, and water, and it is now the most densely settled portion of the state. The Cretaceous outcrop cornprises sorne of the best farming land in Texas, including the Black Land cotton belt; and its western portion, the Edwards Platean, is an important stock raising area. About 34% of the state's population resides on the Cre­taceous outcrop, and on it are built rnost of the largest cities, Dallas, Fort Worth, Waco, Austin, San Antonio, and El Paso. Important artesian water reservoirs are in the Woodbine, Edwards, Paluxy, U•Stovall, J. Willio, Tho Jurauic in Oldahoma, Science (n.o.) 76: 122-123, Auguat 5, 1932. and Travis Peak formations. Sorne of the largest oil fi.elds, notably those in east Texas and along the Mexia and Luling fault zones,18b produce from Upper Cretaceous f~rmations. Upper Cretaceous coal occurs in the Rio Grande embayment (Eagle Pass, Big Bend). The second largest quicksilver district in the United States is near Ter· lingua in Lower Cretaceous rocks. Most of the Portland cement plants in the state and many brick pits use Cretaceo'us materials. An increasing amount of Cretaceous building stone is being quarried. Rocks belonging to this system supposedly were originally deposited over practically the entire area of Texas. At the present time about 75,000 square miles (28%) of the state consists of Upper and Lower Cretaceous outcrops; 35%, lying gulfwards from the outcrop, has the Cretaceous buried beneath younger rock forma· tions; and from the remainder of Texas the Cretaceous has been stripped by erosion, laying bare the underlying rocks. The combined maximum thicknesses of various Cretaceous formations in Texas reach a total of about 15,500 feet, but no single section includes· all of this thickness. The thickest local sections are in the geosynclines of the Rio Grande embayment and the eroded and buried remnants of the Sabine uplift. History o/ Cretaceous deposition in Texas.-At the end of the Jurassic, the North American continent was practically all dry land, the late Jurassic seas of the Western Interior (Logan sea, Argovian) and of Mexico (Kimmeridgian · Tithonian) having retreated. The eroded land surface in Texas at this age has been called the Wichita Paleoplain by R. T. Hill. Upon this land surface Cretaceous seas advanced from the south and east of Texas, and Cretaceous history in this region is largely a record of the deposits of these northward advancing seas. As during Jurassic times, western North America was the scene of three advancing seas, the Pacific sea, the Arctic sea, and the Gulf {or Coloradian) sea. The stages of advance of the Gulf sea are shown in Fig. 22. By Eagle Ford time ii: had reached Colorado and had united with the southern end of the Arctic sea, and during this and the succeeding Austin lBhCertain structural features and physiographic subdivisiona mentioned in the text of Part 2 are ahown on various figures in this bulletin, aa follows: High Plains, Llano Estacado, Maratbon Baain, Osage Plaina, Solitario Baain, on Fjg. 2 (page 28); Balcones Fault, Llano Uplift, .O~achita Mountaina, on Fig. 3 (page 29) ; Eaat Texae embayment, Mieei11ippi embaymenf, Sabine Uplift, Balcones Fault, Nueces embayment, San Marcos arch, on Fi¡. 28; Mexia ..Powell faulta, on fige. 28, 31, 32; Luling faults, on Fig. 36. The Geology of Texas-Mesozoic Systems 261 (Niobrara) stage the maximum advance of the seas over the Western Interior occurred. Near the end of the Cretaceous the Coloradian sea had retreated gulfwards, and in both the Rocky Mountain and northern Mexican regions, considerable ~scillations of marine and non-marine conditions occurred. The Cretaceous marked th"e last great epicontinental marine invasion, and succeeding Tertiary seas were restricted to relatively narrow areas near the continental margin. Facies.-Corresponding to the conditions of deposition, various lithologic facies occur in Texas. The marginal belts of whatever age contain prevailingly sandy or conglomeratic materials, the epicontinental deposits farther o:ffshore consist of shale, clay, marl, chalks, limestones, reef coquina, and various other materials. The prevailing facies in the Texas Cretaceous may be summarized as follo.ws: Continental deposits Marginal facies F1uviatile, palustrine deposita Littoral deposits (between tides) Laguna!, deltaic, and brackish deposits Neritic facies Normal neritic: clays, marls, chalks, limestones Reef deposits: coquina, reef limestones No adequate study of the varied facies of the Texas Cretaceous depositS has been made.14 It has been claimed that many common deposits, such as black, pyritiferous muds and chalky foraminiferal limestones are of very shallow-water origin. Many Trinity and Fredericksburg limestones show rain drops, ripple and wave marks, mud cracks, dinosaur and other animal trails, association with gypsum or salt, and other evidences of extremely shallow water. Eagle Ford flags show markings which have been called ice imprints. Cycads and other plant remains characterize certain sandy forma­tions (Paluxy, Gillespie, Woodbine). Brackish water mollusca mark certain sandstones (Trinity, Tulillo), as do dinosaur bones (Paluxy, Trinity, Aguja). The reef facies is marked by certain typical mol­ 14'A atudy in ReceDt facies ia outlined in Steinmayer: Phaee1 of 1edimentation in Gulf coastal prairiea of Louiaiana, Bull. Am. A11oc. Petr. Geol., 14: 903-916. 1930. For clasaificationa of facies : 631, ch. XV. For Recent materials deposited on the ccntinental platforms, aee Shepard, Francia P., Sedimenta of the cootinenital shelves : BulJ. Geol. Soc. Amer., vol. 43, pp. 1017-1040. 1932. lusca (Edwards, Anacacho). Tuff, bentonite and other volcanic materials occur at many levels, especially in the Upper Cretaceous. Areal Geology. -Any purely geographic division oí the Cre­taceous outcrop is arbitrary, and a more natural division, according to facies and zonation, will require much forther study. Geograph· ically, the Cretaceous in Texas occurs in five areas: central Texas, the Edwards Plateau, the Llano Estacado, Trans-Pecos Texas, and the Gulf Coastal Plain. The central Texas outcrop extends from the northeast comer oí the State up the Red River valley and across the East Texas embay­ment, thence southward to near San Antonio, and thence westward to the Rio Grande embayment near Uvalde and Eagle Pass. The Cretaceous extends down-dip for an unknown distance beneath the Gulf Coastal Plain, and has been found near the Gulf Coast in wells on the South Liberty salt dome (1142). The follow­ ing salt domes in Texas have Cretaceous formations exposed at the surface: Steen dome (1250, pp. 209-216; 1252, pp. 231-237). Upper Cretaceous clays are stated to outcrop near the vertically tilted Midway. Bullard dome (1298, p. 540). Navarro and Taylor are stated to outcrop on this dome. Brooks dome (1250, pp. 191-209; 1252, pp. 237-243). Navarro clays, Taylor chalk ( with microfauna), and Austin chalk (with Baculites, Ostrea plumosa, Gryphaea, lnoceramus, Hamites (?) outcrop on this dome. Keechi dome (1252, pp. 243-253; 843, pp. 266-268; 461, p. 305). Austin chalk and Navarro grayish-yellow lumpy clay (with Exogyra cancellata, Nucula cí. eufaulensis Gabb, Trigonia, Plicatula, Crassatellites, Ringicula, Baculites, Belemnitella americana, "Pachydiscus") outcrop. Palestine dome (461, 843, 1189, 1252, pp. 253-261) Buda, Woodbine (?) Eagle Ford, Austin, Taylor and Navarro outcrop on this dome. Butler dome (404, pp. 647-663; 1252, pp. 262-268). Navarro outcrops on this dome. Marquez dome, Leon County. According to C. L. Baker, Navarro (carrying Scaphites), and Taylor outcrop. Severa! northern Louisiana domes15 also have Cretaceous exposed; among them are: Arcadia (with Arkadelphia exposed), Bistineau ( with Marlbrook), Kings ( with Marlbrook), Prothro (Blossom, ?Brownstown, Marlbrook), Rayburns (Blossom), and Vacherie (Arkadelphia). ""Spooner, W. C., Interior oalt dom .. of Loul1lana, Bull. Am. A11oc. Petr. Ceo!., 10: 217--Q92, · 1926, and Ceo!. Salt Dome Oil Field1, pp. 26~344, 1926. V eatch, A. C., The 1aline1 of northern Louieiana, La. State Exp. Sta., Spec. Rept. II, pp. 47-100, 1902. The Geology of Texas-Mesozoic Systems 263 The Edwards plateau comprises a large area west and north of the Balcones fault. At its southeastern comer is the Llano uplift, which was formerly covered by Lower Cretaceous rocks. North of it to the Red River is a large Pennsylvanian-Permian area from which Cretaceous rocks have been stripped by erosion. The Callahan divide is a remnant of their former extent, but how much farther north they, and particularly the Upper Cretaceous, extended is unknown. The edges of the southern half of the Llano Estacado contain Lower Cretaceous rocks, lying above the Triassic and beneath the Cenozoic cover. Cretaceous is ahsent in much of the Canadian River region, and present farther north along Cimarron River in the Oklahoma Panhandle. In the Trans-Pecos Texas, the Cretaceous, much a:ffected by tec­tonic movements and by holson fill, now outcrops in severa} scattered areas. The Texas Cretaceous is continuous, stratigraphically and struc­turally, with that in the Rocky Mountain region and in northern Mexico. For reference, the following table shows the commonly accepted equivalence of Texas Cretaceous groups with those in the Western Interior (southeastern Colorado) and in eastern Mexico (Tampico embayment). Eastem Tampico San Luis Southeastem Stage Embayment Potosí Texas Colorado Velasco Maestr. Cárdenas Navarro Fox Hills Campan. Mendez Mendez Taylor Pierre San ton. equiv. Coniac. San Felipe Tamasopo Austin Niobrara (upper) Turonian San Felipe Eagle Ford Benton (lower )15Q. Albian El Abra Washita Purgatoire · Tamaulipas Fredericks­(Taninul) burg ?Trinity Unnamed ? Lower Neocomian isaor. L. w. Stephenson has given the lower ( Eagle Ford) portian of the San Felipe a new name. To pography, Soils, V egetation.-Two sets of differences account generally for the great but systematic diversity in lithologic and topographic expression of the Texas Cretaceous: from north to south, changes of facies, agreeing with the prevailing direction of transgression of the seas (as for example, the great development of the reef facies in the Fredericksburg in south Texas); and from central Texas to west Texas the change in amount of rainfall from humid to semi-arid conditions, with resulting differences of vegeta­tion, weathering, and soil. . . Progressive lateral changes in the physiographic expression of rocks of the same age under these conditions constitute a study yet to be made. The humid region, with more than about 25 inches of annual rainfall, extends westward in Texas to the 99th meridian along a line from Red River to San Antonio, and thence southeastward to the Gulf near Rockport. The sub-humid region with 15 to 25 inches of annual rainfall, extends thence westward to a line just east of the Pecos and parallel to it. This line marks a pronounced change in soil, vegetation, and topographic expression of the Cretaceous forma­tions, and the part of Texas east of it will be referred to loosely as the "humid" region, that west of it as "semi-arid." The line dividing the humid from the sub-humid region is stated to continue north­ward to the Canadian boundary and to divide the soils of the United States into two large groups: western, sub-humid, called pedocals, in which sorne horizon of the fully developed soil profile contains more calcium carbonate than does the underlying geological fonna­tion from which the soil is derived; and eastern, humid, called pedalfers, in which the maturely developed soil profiles contain no more calcium carbonate than does the formation, and a shifting or accumulation of sesquioxides occurs (199a, pp. 18-19). More specifically, the groups of the Texas Lower and Upper Cretaceous are mostly characterized by definite soil series. Thus the Upper Cretaceous Black Prairie is composed of the "Houston­ Wilson" soil series (op. cit., pp. 51-70), the Lower Cretaceous Grand Prairie of the "Denton-San Saba" series (op. cit., pp. 68-76), the Western Cross Timbers (Trinity) by the "Winthorst-Nimrod" group (op. cit., pp. 76-82), the Edwards Plateau by the "Denton­ Valera-Ector" groups (op. cit., pp. 113-125). The westward decrease of rainfall has two general effects on topographic expression of the Cretaceous formations: decrease in The Geology of Texas-Mesozoic Systems 265 the amount of vegetation, and consequent sparseness of the soil cover, which is largely removed by erosion. The same hard and soft formations on passing west acquire sharpened profiles and other characteristic e:ffects of arid weathering. Thus the topographic expression of a given formation changes markedly on passing from the humid to the semi-arid region. Another marked regional change in topographic expression is a result of change in the lithologic facies of a given formation. The change from the prairie type of soft Georgetown between W aco and Denison to the limestone plateau type in the lower Pecos drainage is an example. In central Texas the Austin chalk forms prairies; in the Trans-Pecos region it is softer and forms flats. The physiography of the humid region of Texas remains to be written. It has been treated incidentally by Hill and a few other writers (803, 506, 878). The semi-arid region has been briefly treated in several papers (44, 537a, 538, 139, 936, 12; references in 12, p. 17; also 1288a, pp. 5--0, 10-16. Structures afjecting the outcro p.-Various regional structures in Texas, although their implications are much more extensive, mark­edly a:ffect the outcrop and subsurface occurrence of Cretaceous formations, and accordingly are listed here. Sabine uplift (761, 1248, 1124, 1125).-A complicated struc­turally high area in northwestern Louisiana and adjacent Texas counties. The Trinity group is generally present, and on certain high areas the Fredericksburg and most of the W ashita have been subsequently removed, but are present on the flanks. In east Texas fields, the basal Gulf formations overlap against the uplift and sorne are absent; the Bingen and higher formations are generally present. Sorne of the formations are in the marginal facies. Some­what similar relations hold for other structurally high areas in northern Louisiana. The Louisiana Cretaceous section is entirely underground, except in the salt domes mentioned above. East Texas embayment (415, 542, 543, 1232, 1232a, 1691, 987a). -This structurally low area roughly parallels the western side of the Sabine uplift (1232a, pi. I), extending from central Cass County southwest to central Wood County, thence southwards to Anderson County. The strata elevated on salt domes indicate that the Upper Cretaceous section is relatively complete; the Comanche series has at most places not been reached by the drill. Prestan anticline (803, 1530, 174, 177, 844) .-This southeast­trending, plunging anticline marks the turning point of the Cre­taceous outcrop, as it turns south from the Red River valley. The structure appears to affect the formation thicknesses only in minor details. Fort Worth basin (10, p. 13) .-A southeast-trending depres· sion, produced by mid-Paleozoic foldings, and largely filled by late Paleozoic sediments. However, the Cretaceous formations thicken toward its center, and are thinned over the adjacent highs. Plummer (1234a) has outlined the Mineral Wells geosyncline (1228, pp. 60, 205) , arising at the end of the Bend epoch, located between the Bend arch and the Balcones Mountains, and i'unning from Bridge· port south to near San Saba. San Marcos arch.-Running southeastward from the Llano uplift, this broad, plunging arch crosses Blanco, Hays, Guadalupe, Cald­well and G<>nzales counties. The San Marcos River, for which it is here named, flows almost down its crest. Cretaceous formations, notably the Eagle Ford and Austin, thin on crossing this structure. Llano uplift.-This name is used instead of the misnomer "Central Mineral Region," prominent inlier of pre-Cambrian and Paleozoic formations outcropping in Burnet, Llano, Mason, San Saba and adjacent counties. Locally around this high area, as around sorne areas farther west and now buried in the Edwards Plateau, the basal Cretaceous seas contained islands against which the Trinity or even lower Fredericksburg seas overlapped, and which contributed locally coarse (marginal) detritus. So far as is known, middle Fredericksburg and ali later seas completely covered the area (1580, 1581, 1583, 1587, 1589, 274, 350a). Chittim arch (1681, 578a) .-Vanderpool (1681, p. 252) calls this structure the Chittim anticline. It trends generally southeast through central Maverick County into northwestern Dimmit County, and causes a prominent gulfward displacement of the Cretaceous outcrops. Down-dip and underground there is a notable thickening of the Escondido section through intercalation of marine and non-. marine beds not present at the outcrop. A subordinate structural feature on this arch was called the Lampasitas arch by Udden (1625, pp. 88-90). The Geology of Texas-Mesozoic Systems 267 Rio Grande embayment (578, 578a, 1681) .-The greatly thick­ened Upper Cretaceous and Tertiary formations in the lower Rio Grande valley indicate synclinal deposition. Evidences for this are the thick uppermost Cretaceous section below Eagle Pass and the thick basal Tertiary in the Salado arch (along Rio Salado, Nuevo Leon16) and in the Guerrero well. Besides the thickening of beds, the most notable stratigraphic feature is the appearance of near­shore and fresh-water facies, including .coal beds, in the Upper Cre­taceous in this embayment. The limits of the embayment proper up the Rio Grande have not been worked out. In the Big Bend region the uppermost Cretaceous (Aguja, Tornillo) is composed oí near-shore sandstones and apparently non-marine clays contain­ing saurian bones. Terrell arch.-This name is here given to the structurally high · area in which the Paleozoic floor is reached at shallow depths, extending west of north apparently from the Burro Mountains, and reached in drilling in Terrell and adjacent counties. lt a.ffects the thickness of certain Cretaceous formations: for example, the Grayson (=Del Rio) disappears on crossing it, but thickens again on either side. The Zambrano well, with thick marginal arkoses as near Cuatro Ciénegas, lies to the east of this structure. Terlingua arch (1648) .-This name is here applied to the prominent, structurally high, faulted strip passing southeast from the Solitario dome through the Terlingua quicksilver district and plunging toward the structurally low Chisos Mountains. Solitario dome (1652, 44, 1436, 1442, 1249) .-This almost perfectly circular dome, displaying many remarkable geological features, is centrally unroofed and forros a basin. It is an alleged, but not demonstrable, laccolith. Many Trans-Pecos structures show similarity in forro and geology: Finlay Mountains, Cox Mountain, Sierra Madera, Christmas Mountain, Payne's Water Hole, and sev­eral unnamed structures in or near the Terlingua Quadrangle. For map of Solitario, see Fig. 9, p. 119. Marathon dome (1652, 44, 1643, 927, 930, 932, 935, 936, 940) .­This large and unsymmetrical dome is unroofed and eroded to forro a basin. Along its extensive margins Trinity formations change facies and the Glen Rose disappears northwards, hut these effects 18Jones, R. A., A reconnaissance study of the Salado Arch, Nuevo Leon and Tamaulipaa, Mexico. Bull. Am. Aaooc. ·Petr. Ceo!., 9: 123-133, l fig., 1925. are regional and not direct e:ffects of the structure. However, in the northern part of the Marathon dome, overlaps in the Lower Cretaceous involving levels up to high Fredericksburg ( 936, p. 95), are an e:ffect of original structure. Balcones fault zone (544, 672a, 766, 803) .-It was first recorded by E. D. Cope (On the zoological position of Texas, U. S. Nat. Mus., Bull. 17, pp. 5-8; also. Iiill, 732, pp. 292-293, footnote, 1887). The type locality is on Helotes Creek, Bexar County, about 18 miles northwest of San Antonio, where the fault was first observed by the zoologist, G. W. Marnoch. The Balcones fault was first named by Hill in 1890 (766, pp. 117, 134-135). Gulf Coastal Plai,n (538, 803, 1536, 1537) .-The Gulf Coastal Plain in Texas has been defined as limited landwards by the basal contact of the Comanche series as far south as Austin, thence by the Balcones fault southwards and westwards to the Rio Grande embay­ment near Del Rio. Paleontology. -The general faunal complexion of the Texas Cretaceous is as follows ~ in common with . the circum-equatorial Cretaceous of the world, it has in its southward extent a great development of rudistids, mostly segregated in limestones of the reef facies, and farther northwards the rudistid reefs finger out into normal sediments, and the rudistids diminish and disappear. The normal sediments are marked by ammonites and generally lack rudistids; the reef facies generally has rudistids, corals, or sponges, and lacks ammonites. The Texas Cretaceous shows a large provin­cial development of banks or aggregates of the oyster Gryphaea and ammonites of the family Engonoceratidae at several strati­graphic levels. It appears to be characterized by the absence or great rarity of several ammonite groups: lytocerids, phyllocerids, hoplitids, tissotids, and many Indo-Pacific genera. Like the Cre­taceous in Africa, India, and western Europe, it has a large develop­ment of parahoplitids in the Aptian, Douvilleiceras in the lower Albian, dipoloceratids in the middle and upper Albian, pervinquie­rids in the upper Albian, acanthoceratids in the Cenomanian, vasco­ccratids in the lower Turonian, prionotropids in the upper Turonian, mortoniceratids in the Santonian, lnoceramus in the Upper Cre­taceous, and various desmoceratid groups in both Lower and Upper Cretaceous. Many ammonite genera and subgenera and a few other fossils are cosmopolitan, short-range (zonal) fossils, and provide a The Geology of Texas-Mesozoic Systems 269 zonation of the Texas Cretaceous valid for the area and agreeing in essentials with zonations estahlished elsewhere. Some other fossils, as certain ammonites and oysters, appear to he provincial. The Texas Cretaceous contains many genera of cosmopolitan and long-range fossils, of which echinoidea, foraminifera, ostracoda, pelecypoda, and gastropoda, have heen hest studied. As in eastern and northern Africa, certain clays contain a large development of pyritic dwarf (micromorph) fossils. The Texas section, except for the basal Neocomian, which is well developed in the adjoining area of Coahuila and Chihuahua, is practically complete. It is exceptionally well exposed, the fossils at many places are well preserved, and with further study it will undouhtedly prove to he one of the hest standard sections in the world. Although great gaps exist in the knowledge of the Cretaceous plant succession in the Southwest, it appears that Angiosperms were practically missing during th~ Trinity hut may have arisen in the Frederickshurg (Cheyenne sandstone) . Upper Cretaceous (Berry, 100 e) Ripley (Berry, U. S. Geol. Surv., Prof. Paper 136) : some Pteridophytes and conifers, mostly Angiosperms. Taylor (Udden, 1627; Wieland, 1758a): one cycad. 'lf'oodbine or Eagle Ford (Berry, 105): Cycadophytes, 1; Conifers, 1; An· giosperms, 38. Lower Cretaceous (Berry, 98a, 99) Pawpaw (Stephenson, 1530): undetermined fragments. Cheyenne (Berry, U. S. Geol. Surv., Prof. Paper 129-1): Pteridophytes, 4; Cycadophytes, 2; Conifers, 4; Angiosperma, 12. 'lf'alnut: V erticillate alga e; undetermined stems. Palll.%7 and Gillespie (Wieland, 1759a): cycads, and ? gymnospermous wood. Glen Rose (Fontaine, 545; Groves, 633; Torrey, 1608; Wieland, 1759): Algae (Chara), one Equi.setum, a few ferns and cycads, mostly gymnosperms; no angiosperms. Partition of Texas Cretaceous.-In Texas and adjacent areas the Cretaceous strata are divisible into two well-marked series: Comanche ( = Lower Cretaceous), and Gulf ( = Upper Cretaceous) . Neither series can he regarded as a system: they are essentially provincial and not world-wide. On the other hand, their validity as series can he ri:taintained on severa! grounds. The stratigraphic break hetween them is persistent and widespread in the southwestern TABLE OF CRETACEOUS Group Navarro Taylor Austin Eaglei"ord Woodbine Washita Fredericks-burg Trinity Arkansas North Louisiana Arkadelphia Nacatoch Sara toga Marlbrook Annona Ozan Brownstown Tokio "Wood­bine" Washita (undifier­entiated) Fredericks-burg (undifier­entiated) Upper Red Beds Upper Glen Rose Anhydrite Zone Lower Glen Rose LowerRed Beds Northeast Texas Kemp Nacatoch Corsicana (restricted) Unnamed Marls Pecan Gap Wolfe City Unnamed Marls Gober Blossom Bonham Eagle Ford Woodbine Grayson Main Street PawPaw Weno Den ton Fort Worth Duck Creek Kiamichi "Goodland" Walnut (Paluxy) Antlers Trinity-Brazos Rivers Kemp Nacatoch Corsicana (restricted) Unnamed Marl Marlin (Cooledge) Lott Durango Rogers Unnamed MarIs Austin Arcadia Park Britton Tarrant Lewisville Dexter ? Pepper Grayson Main Street PawPaw Weno Den ton Fort Worth Duck Creek Kiamichi Edwards Comanche Peak Walnut Paluxy Glen Rose Travis.Peak Austin Navarro Taylor Burditt Austin Chalk Arcadia Park-Britton Tarrant ? Pepper Buda Grayson Georgetown Edwards Comanche Peak Walnut Glen Ros~ Travis Peak Eagle Pass Escondido Farias Olmos San Miguel (Anacacho) Upson Austin Val Verde-Eagle Ford Buda Grayson Georgetown Edwards Comanche Peak Glen Rose The Geology of Texas-Mesozoic Systems 271 UNITS IN TEXAS Chispa Sierra Big Bend European San Carlos Summit-Blanca- Pecos Quitmans Sta ges County Tornillo Tornillo Aguja Aguja Maestrichtian (Upper ) (Upper) Aguja Aguja (Lower) (Lower) Campanian Taylor Taylor Taylor Upper Santonian Lower Santonian (restricted) Terlingua Colquitt ConiacianAustin Austin Turonian Boquillas Upper Summit Chispa Boquillas Eagle Ford Cenomanian Middle Cenomanian Buda Buda Buda Buda Lower Grayson Grayson Grayson Grayson Cenomanian Main Street Weno Den ton Upper Albian Georgetown Georgetown Georgetown Duck Creek Fort Worth Kiamichi Kiamichi Edwards- Kiamichi niversity Comanche Edwards Mesa Finlay Middle Albian Peak Comanche Walnut Peak Maxon Cox Lower Albian Shafter Glen Rose Glen Rose G!en Rose Cuchillo Upper Aptian Presidio Las Vigas ValanginianTorcer United States. The break in the megafauna is practically complete .. In Louisiana and east Texas at least, a period of orogeny and: perhaps vulcanism intervened. ­ Grouping of the strata into smaller units, such as formations, is less satisfactory, and, on account of changing lithologic facies, is of only local value. The practice of giving formation names to local lithologic units would eventuate logically in a separate name for each facies of each lithologically distinguishable age. If carried out for Texas alone, this would result in many more formation names than are here presented. An inspection of Taylor equivalents,. for instance, will show that a much more involved nomenclature is possible than that now existing. For purposes of correlation, even interstate, the establishment of a detailed, reliable fossil zonation is imperative. In the following discussions, existing formation and member names are recorded for reference and comparison, but their correlation is only provisional. The correlations here given between Texas and the Gulf States, the Western Interior, New Mexico, Arizona, northern Mexico, Europe and elsewhere, · are necessarily only provisional. Many further zonal details and refine­ments are necessgry, both in Texas and in Europe, before a good conelation is possible. The basal contact of the Cretaceous is everywhere in Texas marked by a major unconformity, and the Cretaceous rests upon a diverse patchwork of formations ranging in age from pre-Cambrian to Jurassic (Kimmeridge or ?Tithonian). The upper contact of the Cretaceous is unconformable and represents a break of unknown magnitude. In the table, on pages 270 and 271, the formations of the main outcrop areas in Texas are shown, with their approximate equiva­lences. COMANCHE SERIES17 (Lower Cretaceous), emended The Comanche series was first named by Hill in 1887 (731, pp. 298, 300; 732, p. 299) from the town Comanche, Texas, where he first studied these rocks, and from the Comanche Indians, who inhabited the central denuded region of Texas. 11Literature.-Ark.-Okla.: Dane, 392; Bullard, 174. Northeast Texas: Matson, 1059; Renick, 1298. North-central Te"ª" Bullard, 176, 177; Bybee, 189; Hill, 731, 732, 772, 780, 803; Labee, 969; Marcy, 1055; Shuler, 1453; Tatr, 1575; Winton, 1789, 1790, 1791. South-central Texu: Adkins, 11, 16; Hnssan, 672a; Hill, 743, 803, 808; Pace, 1168; Roemer, 1330; Sellarde, 1402. The Geology of Texas-Mesozoic Systems 273 Synonyms.-Upper Cretaceous (part), Shumard, 1463, pp. 582-590. Middle Cretaceous, and Lower Cretaceous (part), Marcou, 1042, pp. 86-97. Texas Group, Hill, 731, p. 300. Shasta Series (part), J. S. Diller, Potomac Group (part). Emended definition.-The rocks of earliest Cretaceous (pre-Travis Peak) age exposed in Malone Mountain, southern Quitman Moun­tains, and the Rio Conchos region, described by Cragin in 1897 and 1905, and later by Burrows and others, were unknown when Hill defined the Comanche series and the Trinity group, and were never included in the definitions of those units. Various writers have accordingly criticized the definition of Comanche series for not including even all of the Lower Cretaceous present in Texas (as 181, p. 153, footnote) . This earliest Cretaceous is Iocalized in an arm of the late Jurassic-lower Neocomian sea whose tip barely entered Texas at the above mentioned localities, and its position elsewhere in Texas is represented by an unconformity at the base of the Trinity as now defined. The Comanche series and the Trinity group are therefore here emended to include also all Neocomian strata existent in Texas. This early Neocomian, with other sediments, continues southwards into Mexico and is there part of a relatively complete Eocretaceous section. It is clear therefore that the limited amount of Cretaceous in Cragin's "Malone formation" in Texas is incidental to the greater development of these beds in northern Mexico, and cannot be classified independently of those beds. For present purposes it is impracticable to assign them to higher than formational rank, and accordingly the formations as described in the following text are referred to the Trinity group of the Comanche series (both in the emended sense) . 1429, 1430; Taff, 1574. Co,,.tal Ploin: Brucks, 164, 165; DeW11en, 421. Edwards Plateau: Beede, 87, 92; Heuderaon, 704; Hill and Vaughan, 795; Paige, 1172. Rto Grande Embayment: Calvert, 192; Christner, 248; Dumble, 480; Getzendaner, 578, 578a; Liddle, 992¡ Schmitz, 1373; Vander. pool, 1681. Trans·Pecos Te"as: Adkina, 12; Baker, 44, 46, 55; BOse, 129; Cragin, 331; Hill, 722, 799, 805, 820; Hoota, 841; K.ing, 936; Kitchin, 944; Lonsdale, 1013; Powers, 1249; Richard· oon, 1304; Roberto, 1324; Sbumard, 1477; Stanton, 152J, 1524~ Taff, 1573; Udden, 1623, 1626. Northern Me%ic.o: BOse, 134, 135; Dumble, 480; Tatum, 1590. W"esteni Interior: Bullard, 175; Darton, 395; Twenhofel, 1621; Hill, 789; Reeside, 1290. Paleontology: Adkins and Winton, 9; Adkino, 13; Alexander, 27, 30; Berry, 99¡ Boehm, 124a; Bohm, 125, 127; Booe, 134; Boyle, 144; Caney, 199; Clark, 253; Conrad, 280a; Coquand, 320; Cragin, 324, 325, 326, 331; Cushman, 357; Elliaor, 520; Fontaine, 545; Gidley, 583; Giebel, 584; Hall, 643; Hill, 735, 755, 796; Hyatt, 867; Kniker, 947; Laaswitz, 976; Lambert, 974; Marcou, 1041; Marcy, 1055; Plummer, 1238; Roemer, 1331; Sbumard, 1456, 1464a; Whitney, 1756, 1757, 1758; Wieland, 1759. lpeoru: Dawson, 398; Sellarde, 1429, I444a; Vaughan, 1686. Economic lmportance.-In the more humid central part of Texas, the Comanche series, mostly composed of softer rocks, underlies the more thickly settled, industrialized, and agricultura} part of the state. The more arid western Comanchean, the Edwards Plateau, is more sparsely settled, and is devoted largely to sheep and goat raising. The east-central Texas area of Comanche is generally divided into the following strips from west to east: (1) the Western (Trinity, Upper) Cross Timbers; (2) the Lampasas Cut Plain, underlain by the Fredericksburg group; (3) the Grand Prairie, underlain by the Washita group, and overlain to the east by the Eastern (Woodbine, Lower) Cross Timbers. In addition to its soils and timber, the Comanche series contains sorne of the most extensive artesian water reservoirs in the state, in the Trinity sands, the Glen Rose, and the Paluxy, and to a lesser extent in higher formations. The Trinity group contains high­gravity oil in several fields, and other Comanche levels locally produce oil and gas. In northern Louisiana fields the Glen Rose produces oil and gas. In Panola County the Glen Rose produces gas ( 612, p. 14 77). Glen Rose casinghead gasoline is produced from the Chittim arch in eastern Maverick County (578, 578a, 1681, 1625). The Walnut is the horizon of the oil at South Bosque (11, pp. 93-98). Edwards produces oil in the Luling field (164, 165, 1262, 1412), at Salt Flat (728a, 1076), at Darst Creek (1355, p. 1387; and H. D. McCallum: The Darst Creek Oil Field, Guadalupe County, Texas, MS., 1932), and at Larremore (Weeks, 1716). Other economic products from the Comanche series are stone, clay, gypsum, sand, manganese, quicksilver, and severa! other non­metallic products. Fossil wood from the sand formations of the Trinity group is used some­what for building bungalows, tourist camps, chimneys, and fences in Glen Rose, Waco, Austin, Walnut Springs, ltasca, Stephenville, and elsewhere. This is hauled from near Glen Rose, Stephenville, Comanche, and other Trinity outcrops. Taff (1574, p. 310) records that in the Paluxy near Paluxy and Bluff Dale "silicified trees and.fragments of logs are so abundant that one is reminded of driftwood, which doUhtless they were at the time of deposition of the Trinity sands." Duck Creek ammonites have been used for ornamental building near Fort Worth (1789, pl. 4) . .Stratigraphy and Contacts.-The basal contact is the old land surface called the. Wichita Paleoplain by Hill (803, pp. 363-367). The Geology of Texas-Mesozoic Systems 275 During early Cretaceous times the reduced land mass of Llanoria reached southwards from east Texas into northern Mexico, and the shore line extended from the Malone area southeastwards to the tip of the Big Bend and thence gulfwards roughly parallel to the Rio Grande (133a, 181, 334). During Lower Cretaceous time the Mexican ( or Coloradian) sea spread northwards o ver Llanoria, leaving coarse sandy and conglomeratic marginal sediments in many · parts ·of northern Mexico and Texas. The approximate limit of the Trinity sea is shown on Fig. 16. In central Texas the sandy margin ( of diverse Trinity ages) is known as the Travis Peak, Gillespie, Paluxy, Maxon, and Antlers formations. Profiles indicate that sorne sands of true Trinity age extended farther north than the present outcrop in southern Oklahoma. In western Texas the exact limit of the Trinity is vague, through lack of diagnostic fossils · in the marginal facies, but it is present in the structurally low areas near Fort Stockton (12, pp. 33-37). It is practically or entirely missing in the western Oklahoma outliers, in Double Mountain, in the north­ern Llano Estacado, and at Tucumcari. The Fredericksburg and Kiamichi seas extended farther north, to limits not definitely located but approximately shown in Fig. 13. The land surface upon which the Comanche seas encroached had been planed down through sorne of Permian, all of Triassic, and most of Jurassic time, and is com­posed of diverse rocks of most ages from pre-Cambrian ~o Jurassic. Locally, as in Burnet County, west of the Llano uplift, and on the Marathon dome, this land surface was irregularly submerged and islands remained in the earlier Trinity seas, to be buried by later Comanche deposits. Islands in the Trinity sea are recorded in Choc­taw County, Oklahoma, by Miser (Bull. Am. Assoc. Petr. Geol., 11: 444, 1927). The question of the validity or importance of the Comanche series is bound up with the extent and nature of its upper contact, a question not yet well elucidated. It may be stated that ammonite zonation tends in general to reduce the magnitude of the Comanche­Gulf unconformity in central Texas. The highest Comanche forma­tion, the Buda limestone, is of Cenomanian age; so are the W ood­bine and basal Eagle Ford. In the present state of knowledge of the ammonites concerned (Acanthoceras and Mantellicerizs, with related genera), an exact correlation with Spath's Cenomanian zones is not possible, but the ammonites of the Buda, Pepper, and Woodbine formations are closely related to each other. In east Texas and northern Louisiana the Comanche series was uplifted and eroded before the deposition of the basal Gulf formation. In central Texas south of the Brazos, and in Trans-Pecos Texas, the break is apparently less, and the two series are generally con· cordant; the continuity of the zonation here is questionable, but until better zonal work is available the amount of break of the zones will remain unknown. From Denison, Texas, east to Cerrogordo, Arkansas, the W oodbine unconformably overlies Comanchean formations from Grayson marl clown to Kiamichi; thence eastwards the Trinity group is overlain by Woodbine, at the outcrop. Areal Extent.-The conjectured original extent of the Comanchean rocks is shown in Fig. 13. They occur underground at least as far east as the Richland field. Northwards it extends past central Kansas and eastern Wyoming, east of the Rocky Mountain front ranges, but sorne of its members here are non-marine. Westward it outcrops in eastern and central Sonora. Southward, in passing off the Comanchean overlap, the series has not been delimited and prob­ably loses its individuality, but rocks of its age outcrop in central and southern Mexico and into Central America. In the Texas Coastal Plain it is elevated in the Palestine and other salt domes, and extends gulfwards for an unknown distance. Rocks with sorne identical fossils outcrop in Porto Rico.18 Regional Structure.-Over high structures in northern Louisiana, the Sabine uplift and various local highs, the Comanche formations are in part beveled or removed by subsequent erosion. The outcrop across the western part of the East Texas embayment shows a slight thickening of the formations toward the center of the depression. Sorne formations (as Eagle Ford) are thinned across the San Marcos arch. Others (as Grayson) are thinned over the Terrell arch. Shorewards the formations thin, assume the marginal facies, and are affected by numerous gaps in the stratigraphic sequence. Gulfwards they thicken enormously, especially in the Trinity group. Exact correlation and the proof of the magnitude of various strati­graphic breaks, both await more accurate ·zonal studies; most of what has been written on these subjects to date is largeJy conjectural and speculative. "'Hubbard, Bela, Proc. N. Y. Acad. Sci., Vol. 3, pt. 2, 1920. The Geology of Texas-Mesozoic Systems 277 Fig. 13. Known extent of Upper Jurassic, Trinity, Fredericksburg, Kiamichi, and Duck Cceek localities in and near Texas is shown inside the respective lines. The areas enclosed (to the south and east) by the respective boundaries were sea. This is not a paleogeographic map. Slumped blocks in Comanche formations.-Solution has produced slump near the Gulf-Comanche contact at many places in Trans­Pecos Texas, giving an appearance which sorne geologists have misinterpreted as an unconformity. Along laterals of the Pecos between Del Rio and Sonora, especially along faults, blocks of Eagle Ford and Buda have fallen onto the Georgetown. At localities 2 miles north·northeast and 1.5 miles northeast of Black Mesa, northwest of Terlingua, there are two occurrences possihly explain­ahle by solution and slump. Here hills of Buda-Grayson have been dropped at least 500 feet and rest with gentle or steep dips on an apparently recent Edwards floor. There is a possihility that these are narrow down-faulted hlocks. Facies; Mode of Deposition; Source of Materials.-All Comanche sediments known in Texas are of near-shore or of epicontinental, prohahly shallow-water origin. They helong to (1) the marginal facies, near-shore neritic or partly littoral sands, silty clays, conglom­erates and saline or gypsiferous sediments; (2) neritic marls, clays, shales, and limestones; and (3} reef (zoogenic) limestones, coquina, and shell aggregates or marls. In the Louisiana Trinity and locally elsewhere, there occurs a red hed facies, which has heen claimed to he of continental origin. Numerous local and suhordinate facies also are known. Each of the three groups of the Comanche is distinctive in Texas. The Trinity was deposite.d. on an irregular land surface, down­warped gulfwards, and it filled up most of the irregularities in that uneven surface. Gulfwards and in large synclines it thickened enormously. On the rather even surface of the Trinity the Fred­erickshurg was deposited. It has less pronounced changes in thick­ness, hut is distinguished by a great diversity of lithologic facies, corresponding to differences in the sources of its sediments. It is douhtful if W alnut, Comanche Peak and Edwards can he retained as formations in the usual sense, hut possihly those terms might he used to designate respectively the shelly marl, the soft nodular lime­stone, and the rudistid reef facies, for in each of the three supposed formations ali three types of lithology occur. The succeeding and topmost group, the Washita, is distinguished by its partially cyclical mode of deposition, corresponding to sorne periodic change in the conditions of deposition, perhaps oscillations of level or tempera­ture changes. This cyclical deposition is more apparent in the northern than in the southern W ashita area. Topography, Vegetation, Soils.-The Trinity group in its north­ern, more sandy, facies forros the Western Cross Timhers. The comhined Frederickshurg and Georgetown, in their southern and tbicker rudistid limestone facies, form the Edwards Plateau and the region of incised river canyon topography rejuvenated by late Tertiary faulting and uplift. Frederickshurg rocks forro theLampasas The Geology of Texas-Mesozoic Systems 279 Cut Plain. The alternating clays, marls, and limestones of the northern phase of the W ashita group form the Grand Prairie. Numerous minor physiographic divisions are discussed by Hill (803.) The Comanche and Gulf strata in the Gulf Coastal Plain dip gulfwards, producing long strike cuestas of the more resistant formations, with prominent west-facing scarp faces. The vegetation and soils are results in part of the peculiarities oí the rock formations, in part of the amount of rainfall. Sorne vegetation is locally distinctive of formations, but much more indi­cates types of soil or living conditions ( 385, 1789) . The same Cre­taceous formations may be traced westwards from humid central Texas (30 or more inches annual rainfall) to semi-arid western Texas (15 inches or less), and typical corresponding changes in physiographic processes and forms confirmed (12, 936). lgneous rocks in Comanche series.-Dikes have been recorded in Travis County (1429, p. 43), in Bandera County (398; 1009, p. 12), and in Comal County (1009, p. 12). Plugs occur in Hays and Bexar counties (1009, pp. 12-13) and in Medina County (992). Other Cretaceous occurences are listed by Lonsdale (1009) and by Sellards ( l 444a). Sills, dikes, plugs, and laccolithic bodies are com­mon in the Trans-Pecos Lower Cretaceous. The intrusives are prob­ably mostly of post-Cretaceous age. Caves and springs.-Some caves are located in Cretaceous strata in Texas. Near Salado, Austin, and San Marcos, there are caves in the Edwards lime­stone. A large cave near Boerne is in the Glen Rose limestone. Along the Rio Grande, Devils River, and Pecos River, many small caves and rock shelters occur in the thick Fredericksburg·Washita limestones. Some of the largest springs in the country occur in Cretaceous ·rocks in Texas (Meinzer, 1086c). Springs occur along the Balcones fault zone near Salado, Georgetown, Austin, San Marcos, New Braunfels, San Antonio, and farther west. Some of these exit through the Edwards limestone, though much of their water may come from Trinity aquif ers. Large springs in the Cre­taceous occur near Del Rio, Fort Stockton, Toyah, and elsewhere in west Texas. Outlying Areas of Comanche Series.-Stratigraphically the Texas Comanche (including the Valanginian "Malone" Cretaceous) was deposited on a sloping old land, which was invaded by seas from the south and southeast of Texas. In those directions the section is more nearly complete, and to the north of Texas only attenuated fingers of the Comanchean were deposited. In northern Mexico and in western Cuba (near Viñales) Upper Jurassic deposits occur; the Upper Jurassic seas reached northward to Texas only in the Malone-Quitman mountains area, and possibly riear Brownsville (see Fig. 13). The successive Comanchean seas extended farther into the southwestern states, until during Duck Creek time, they had reached Tucumcari, N. M., and southeastern Colorado. There are no certain records of higher Comanchean in the Western Interior, and after Duck Creek time the sea may have withdrawn temporarily, or the formations, if deposited, were subsequently eroded. The "'outlying areas" of the Comanchean are discussed in the following paragraphs. After the close of Comanchean time, the Dakota-Wood­bine sea occupied a large territory in the Western Interior and in north-central Texas (Fig. 23). Sonora.19-Near Arivechi in northeastem Sonora, a fauna described in 1869 by Gabb includes Fredericksburg species, and contains Engonoceras pierdenale (von Buch), Lunatia pedemalis (Roemer), Scalaria texana Roemer, Tylostoma, Cerithium, Turritella seriatim-granulata (Gabb, not F. Roemer), Tapes gabbi Biise, Gryphaea pitcheri Morton, Gryphaea navia Hall, Gryphaea mucronata Gabb, Pyrina parryi Hall, Phymosoma texanum (Roemer) and others. This fauna requires amplification and restudy. Kellar reoords in western Sonora a neritic fauna like that of the Bisbee section, containing rudistids and large oysters, and in part referred to the Albian. Bisbee, Arizona.-This section consists of four formations, in ascending order, as follows: Glance conglomerate, consisting of bedded conglomerates with coarse pebbles of schists and limestones; Morita formation, huff, tawny and red sandstones, altemating with dark red shale, and near the top a few thin heds of impure limestone; Mural limestone with Trinity fossils, hasally thin· hedded sandy limestones, and in upper part gray, massive, hard limestone; Cintura formation, red nodular shales with cross-bedded, huff, tawny and red sandstones, and hasally a few heds of impure limestone. The Mural limestone contains .Orbitolina texana (Roemer), Glauconia branneri (Hill), Lunatia pedemalis (Roemer), Pecten stantoni Hill, Trigonia stolleyi Hill, Ostrea sp., Trigonia n. sp., Cyprina sp., Astrocoenia sp., Rhynchonella sp., Terebratula sp., Terebratella sp., Caprina cf. occidentalis Conrad, Turritella cf. seriatim· granulata Roemer. and Actaeonella cf. dolium (Roemer) (Ransome, U. S. Geol. Surv., Prof. Paper 21, 1904; Bishee folio No. 112, 1904). The first five named indicate the Trinity group, and the others, though they may be of Fredericks­hurg age, are not diagnostic. Southem New Mexico.-The Hatchet Mountains in southwestern New Mexico contain a Trinity fauna like those in the Mural limestone near Bishee and in the Quitman and Shafter districts in Texas. The following fossils have heen reported (Darton, U. S. Geol. Surv., Bull. 618, pp. 43-44; Darton, U. S. Geol. 19Kellar, W. T., Stratigraphiaehe Beobachtungen In Sonora (Nordwe1t-Mexico), Ecl. geol. Helv., 21: 321-355, 1928. The Geology of Texas-Mesozoic Systems 281 Surv., Bull. 794, pp. 38-39, 1928.): Exogyra aff. quitmanensis Cragin, Kingena aff. wacoensis (Roemer), Orbitolina texana (Roemer), Ostrea sp., Corbula sp., Anchura sp., Turritella sp., Enallaster sp., Hemiaster comanchei Clark, Requienia texana (Roemer), Tylostoma sp., Tapes sp., Limopsis sp. In the Potrillo Mountains there have heen recorded: Caprina occidentalis, Cyprina, Trigonia, and Actaeonella dolium. In Luna County, New Mexico, and in the Deming region, the basal Cretaceous Sarten formation is a poorly exposed coarse sandstone, from which the following fossils are recorded: Cardita belviderensis, Cardium kansasense, Protocardia texana, Protocardia quadrans, Tapes belviderensis, Turritella aff. seriatim,.granulata, Ostrea, Nu,cula, Trigonia, Lunatia, Leptosolen, Homomya, Turritella, Anchura, Cyprimeria. This is a Frederickshurg fauna, and most resemhles the Kiowa and Belvidere faunas of Kansas. Northeastern New Mexico.-At Tucumcari Mountain, ahove the Dockum Triassic, there is recorded 100 feet of J urassic Wingate sandstone, 20 to 30 feet of Morrison (Exeter?) white sandstone, and ahout 60 feet of sandy fos· siliferous clay called Purgatoire. The fossils recorded from the Purgatoire are: Exogyra texana Roemer, Ostrea quadriplicata Shumard, Gryphaea tucum· cari (Marcou), Gryphgea corrugata Say, Ostrea cf. subovata Shumard, Plicatula sp., Pecten occidentalis Conrad, Trigonia emoryi Conrad, Protocardia sp., Pinna comancheana Cragin, Cardita belviderensis Cragin, Tapes belviderensis Cragin, Cyprimeria sp., Turritella seriatim-granulata Roemer, Pervinquieria "leonensis" Conrad, Pervinquieria shumardi (Marcou). The last-named fossil, identified by Alpheus Hyatt (796, p. 21), is a Duck Creek marker. Most of the other fossils listed are ohviously high Frederickshurg in age, and are doubtless to he correlated with the Kiowa ( =Kiamichi). To the northwest of Tucumcari, fossiliferous Comanchean shortly disappears. Stanton records (Jour. Geol., 13: 666, 1905) on the north side of Canadian River 15 miles northwest of Tucumcari 20 feet of fossiliferous Comanchean, the northwesternmost place at which it was found. Near Sanchez and on the upper Rio Concha the strati· graphic position of the Comanchean is occupied by a non-fossiliferous thin shaly band. Baker (Am. Jour. Sci., (4) 49: 121, 1920) records nearby localities with Gryphaea tucumcari, Ostrea quadriplicata, Cardium, and Turritella. Cimarron County, Oklahoma (Stanton, Jour. Geol., 13: 664, 1905) .-Near Garret, the Morrison is overlain by Purgatoire, 4 to 15 feet of basal, coarse, hrown, or gray, cross-hedded sandstone, with irregular hands of pebbles, followed by dark shales containing the following Comanchean fossils: Hamites fremonti Marcou, Desmoceras brazoense (Shumard), Inoceramus comancheanus Cragin, Gryphaea corrugata Say, Ostrea subovata Shumard, Ostrea quadripli­cata Shumard, Plicatula incongrua Conrad, Gervilliopsis invaginata (White), Trigonia emoryi Conrad, Protocardia multistriata Shumard, Pholadomya sancti­sabae Roemer?, Anchura kiowana Cragin, Turritella seriatim-granulata Roemer. The first three are Duck Creek fossils, the others indicate nothing higher than Kiowa (Kiamichi). Texas County, Oldahoma (175, p. 90).-A small outlier of about 5 feet of soft, white to yellowish sandstone, contains Oxytropidoceras belknapi (Mar· cou), /noceramus, Trigonia, Turritella, Cucullaea? and Tapes?, and is of Kiamichi age. Irestem Oldahoma.-Bullard (175) has run a section across these outlying areas and has shown that the highest marine leve! observed is Kiamichi. ' Avila Hill, on the Oklahoma-Kansas line, contains Gryphaea navia Hall in the topmost stratum of a 138-foot section, the upper 91 feet of which contains G. navia. In the Supply area, the Permian red beds are overlain ·by 25 feet of sandy strata followed by about 36 feet of fossiliferous Kiamichi, of which the uppermost clay contains Oxytropidoceras belknapi (Marcou), Gryphaea navia Hall and Gryphaea corrugata Say. In the Seiling-Cestos area there is 15 feet or less of clay, limestone, and shell bed. containing Oxy. belknapi (Marcou), Oxy. acutocarinatum (Shumard), Gryphaea navia Hall, Gryphaea corrugata var. hilli Cragin, and other fossils. In the Butler-Foss area, essentially the same lithology and fossils are recorded. Southem Kansas.-The Cretaceous formations are, in ascending order: Cheyenne sandstone, Champion shell bed, Kiowa, Spring Creek shale, Green­leaf sandstone. The last formation is overlain by Dakota sand. The Cheyenne, divided into severa! members, consists of white, yellow, and gray sandstone and shale, and contains no fossils except plants, a cycad (Cycadeoidea munita Cragin), and 23 species of dicotyledons and other forms monographed by .Berry. The formation is apparently non-marine, but was deposited directly on a coast. The Cheyenne represents a non-marine Fredericksburg facies, probably about Comanche Peak in age. The Kiowa is marine, and contains a fauna of 17 vertebrates (fishes, plesiosaurs, turtle), insect wings, and 40 species of inverte­brates including the following, which nowhere occur in beds higher than the Kiamichi: *Gryphaea navia, Exogyra texana, *Oxy. belknapi, Oxy. two other species, Pecten irregularis or occidentalis. (Fossils indicated with asterisk are Kiamichi markers.) No fossils definitely indicates Washita age, i.e., Duck Creek or higher. The Spring Creek contains 13 species, of which the following definitely suggest an age not higher than Kiamichi: Lingula sp., Ostrea quadri­plicata. Nothing proves Washita age. The Greenleaf contains: Cyprimeria kiowana, Pholadomya cf. belviderensis, Turritella, Lingula, shark teeth. The identified species all occur in the Kiowa, and nothing suggests any higher horizon. Central Kansas.-ln ascending order the stratigraphic units of the Coman­chean are: Natural Corral shale, Windom fossiliferous limestone, Marquette sandstone and shale, Mentor sandstone with marine fossils. The Windom contains fossils identical with those of the Kiowa. The Mentor contains mostly Kiowa species, and the following also known to be from the Kiamichi: Ostrea quadriplicata, Trigonia emoryi. No species recorded is distinctively Washita (í.e., Duck Creek or younger) . . Colorado.-At Two Buttes, southeastem Colorado, Stanton and Lee (Jour. Geol., 13: 666, 1905) found Desmoceras brazoense and other Duck Creek fossils. In Purgatoire River, G. corrugata and /. comancheanus occur. In the The Geology of Texas-Mesozoic Systems 283 Apishapa quadrangle the Purgatoire contains : Avicula, Pecten, Trigonia?, Protocardia, Tapes?, Pholadomya sancti-sabae, Trigonia emoryi, Cardium kansasense, Cyprimeria, Protocardia texana, Leptosolen conradi, lnoceramus comancheanus. Stanton correlated this fauna with the Kiowa. lt suggests a hlgh Fredericksburg age, except that /. comancheanus ranges from Duck Creek dt>wn into the post-Kiamichl beds at Fort Stockton, and therefore líes near the Washlta boundary. At a locality near Canyon City, the Purgatoire contains Pholadomya sancti-sabae, Lingula, Tapes, and a mactroid. Reeside (1290) records Purgatoire fossils, including unidentified ammonites, from as far north as Laramie County, Wyoming. They include species of lnoceramus and .Ostrea, Pteria salinensis White, Anchura kiowana Cragin?, Pachydiscus sp.? [Beudan­ticeras?], an ammonite, and fish scales and bones. These localities must he near the Kiamichi-Duck Creek contact. Dr. Moore verbally reports Purgatoire fossils at severa! localities north of central Kansas. Severa! localities in the Llano Estacado in Texas show Comanche Peak, Edwards, Kiamichi, and Duck Creek zone fossils (pages 355-358). Purgatoire formation in DaUam County.-C. L. Baker has lately restudied the isolated Mesozoic exposures in Dallam County, the northwesternmost county in the Texas Panhandle, and has kindly furnished the following notes on these exposures. Although no animal fossils were collected, the lithology permits identification in this area of the formations usually considered Morrison, Purgatoire, and Dakota in northeastern New Mexico. Composite section on North Perico Creek, 2 miles north of Texline from 1,2 mile west of Texas-New Mexico state line to % mile east of that line, and South Perico Creek, about 1 mile south of Texline. Purgatoire formation (Cheyenne?): Caliche at top of section Feet 6. Sandstone, soft, fine·grained, tawny yellow; like Tucumcari beds Clh mile west of New Mexico lineL.-···-···-····-···-···-···-····-----5 5. Sandstone, slabby, brown, ferruginous ................... ·-················-·········-····-3 4. Shale, the lower half sandy, the upper half bentonitic. Most of the bentonitic shale is green, and contains many thin irregular seams stained brown by limonite, dendrites of manganese, and botryoidal masses of barite up to 8 inches in diameter.. ................. ·-··········-····-····-··-15 3. Sandstone, buff to dark brown, fine grained, cross-bedded, ripple­marked, containing many dark brown to black ferruginous concre­tions, plant fragments, and sorne fucoidal markings ................... ·-···-··-8 2. Sandstone, somewhat blue-gray, weathering light buff, fine-grained, with platy and shaly bedding, and containing many fucoidal markings 4 l. Sandstone, buff, fine-grained ......... ·-····-·········-····-·········-··········-··········-········ 2 TRINITY GROUP (emended) 20 Sediments of this group were deposited in Texas in a transgressing sea, whose margin moved northward during Trinity time; the limit of its advance is shown roughly in Fig. 16. Practically everywhere its base consists of sand or conglomerate, which of necessity is of different ages at different places along the line of advance. lt follows that this basal lithologic unit is not a formation, if by formation is meant a rock body of a single restricted contempo· raneous age. It is the combined marginal facies of various Trinity levels. The middle of the Trinity group generally though not every­where consists of a limestone, usually somewhat sandy. The upper· most Trinity is likewise a sand shorewards, a limestone seawards. As in the Fredericksburg group, formations, even though useful in small areas, may not be of the same age over greater distances. Rocks of the same facies are of different ages at different places, and rocks of the same age laterally change rapidly in facies. There­fore the Trinity group will be treated as a whole, and the various, in part overlapping, formations which have been used in di:fferent parts of Texas will be mentioned in their appropriate stratigraphic connection. FORMATIONS OF TRINITY GROUP IN TEXAS Northem and Marathon Sierra Blanca-central Texas basin Quitman Mtns. Stages .,"' .... 11 < Paluxy Maxon Cox Lower Albian Glen Rose Glen Rose Glen Rose- Cuchillo Travis Peak "Basement Mountain- Upper sands" Las Vigas Aptian (absent (absent) Torcer Valanginian 20Literature.-Arkamas: Dane, 392; Hill, 753. Oklahoma: Hill, 803; Bullard, 174, 175; Taff, Atoka, Tishomingo folios; Honess, 839, 840. Louisiana: Spooner, '\\~. C., Interior salt domes of Louisiana, Bull. Am. Assoc. Geol., 10: 217-292, 1926, and, Geol. Salt Dome Oil Fields, 269­344, 1926; Veatch, A. C., Salines oí north Louisiana, La. Geol. Surv., Spec. Rept., 2, 1902¡ Shearer, H. K., and Hutson, E. B., Dixie oil pool, Caddo Parish, Louisiana, Bull. Am. Assoo. Petr. Geol., 14: 743-764, 1930; Ross, J. S., Deep sand development in Cotton Valley field, Webster Parish, Louisiana, Bull. Am. Assoc. Petr. Ceol., 14: 983-996, 1930; Crider, A. F., Pine Is!and deep sands, Caddo Parish, Louisiana, Str. Typ. Amer. Oil Fields, II: 168-182, 1929; Fletcher, Corbin ·n., Structure oí Caddo field, Caddo Parieh, Louisiana, Str. Typ. Amer. Oil Fields, II: 183-195, 1929; Spooner, W. C., Homer Oil Field, Claiborne Parieh, Louisiana, Str. Typ. Amer. Oil Fields, II: 196-228¡ Teas, L. P., Bellevue oil field, Bossier Parish, Louisiana, Str. Typ. Amer. Oil Fields, II: 229-253, 1929. North.-central Te"4&: Bullard, 176, 177; Winton, The Geology of Texas-Mesozoic Systems 285 Hill (731, p. 298) at first placed Shumard's "Caprotina lime­stone" (= Glen Rose) in the Fredericksburg group and separated the "Upper Cross Timbers" (= Travis Peak) as an independent and earlier unit. The term "Trinity division" was first used by Hill in 1889 (735, pp. xiv-xv). Taff's "Bosque division" (1574, p. 280, 1891) is a synonym. The name "Travis Peak sands" was applied by Hill (766, p. 118) in 1890 to the basal marginal facies of the Trinity group in Travis County; the succeeding limestones were called "Glen Rose or Alternating Beds" by Hill in 1891 (772, pp. 504, 507; 780, p. 83) , and the upper Trinity sands were called Paluxy in 1892 (780, p. 84). These three formations comprise the standard type section of the Trinity group. The basal marginal facies, where its exact correlation appears doubtful, has been generally referred to in the literature as "Basement Sands." Along a line (Fíg. 18) through Brown, Parker, Wise, and Denton counties, the Glen Rose facies interfingers out into sand on going northwards, and the combined Trinity sand here has been called Antlers (788, p. 303). Much of it is Trinity, but its upper part may be of Fredericksburg age. In west Texas the nomenclature of the Trinity has met with similar difficulties, and sorne authors, through lack of knowledge of the fossil contents of the beds, have introduced much confusion into the nomenclature. Richardson, in describing the section northwest and northeast of Sierra Blanca, called the basal conglomerate "Campagrande" (1304a, p. 47), the type locality being in the Finlay Mountains; a higher sandstone was called "Cox" (1304, p. 47) from Cox (Tabernacle) Mountain. The overlying Finlay limestone (1304, p. 47) is of Fredericksburg (Comanche Peak-Edwards) age. The basal conglomerate 4 miles west of Sierra Blanca was called "Etholen" by Taff (1573, p. 723). These formations, and the Maxon sandstone of King (936, p. 92), about Paluxy in age, situated in the eastern part of the Marathon basin, ali lie in the thinned shoreward northern extension of the Comanche series in Trans-Pecos Texas. Just south of Sierra Blanca, Taff partitioned the Trinity section into Etholen, Yucca (1573, p. 1789, 1790, 1791; Shuler, 1454; Adkins, ll, 16 ; H'i!l, 742, 746, 803; Scott, 1394; Miser, lll3a; Vanderpool, 1679. Central Te%48: Hill, 803, 795, 808; Jones, 888, 891; Sellards, 1402; Liddle, 992. Trans-Pec.os Te!IC6s: King, 936; Baker, 46; Adkins, 12; Udden, 1623, 1625, 1626. Edwards Plateau: Liddle, 991; Beede, 87, 92; Henderson, 704; Hill, 803. Paleontology: Hill, 762, 767, 783; Rauff, 1286; Burck.hardt, 180a; Vanderpool, 1678, 1679. Paleobotany: Groves, 633; Fon­taine, 545; Torrey, 1608; Sel1ards, 1416; Wieland. 1758a, 1759, 1759a; Adkins, 12, 13. Trans· gressions ond regre&&ions: Grabau, 629b; Hill, 803; Scott, 1394. 725), and Bluf! (1573, p. 727) heds; farther southwest and down the overlap near Quitman Gap he partitioned the Trinity equivalents into Mountain (1573, p. 730) and Quitman (1573, p. 728) heds. In the Shafter district Udden estahlished the Presidio heds for the basal sands and conglomerates of the Trinity (1623, pp. 25--30), and the Shafter heds (1623, p. 30) for the overlying limestones. In the Conchos River region in Chihuahua, west of Presidio, Burrows has estahlished severa! formations, which are discussed in the following section. At Malone (Torcer), in the Conchos River valley west of Presidio, and prohahly near Hot Springs south of Sierra Blanca, the earliest Cretaceous in Texas, here included in the emended Trinity group, occurs. It will he discussed first. The Trinity elsewhere in Texas may he conveniently divided into thicker, off-sho~e, sections, and tbinner inshore, in part marginal, sections. EARLIEST TRINITY IN TRANS-PECOS TEXAS From north-central Mexico a narrow arm of the late Jurassic and earliest Cretaceous seas extended as far north as Malone Mountain, and left ahove the Jurassic sediments already considered certain earliest Cretaceous heds, which are older than any other in Texas. The main areas to he compared are Malone Mountain, the Conchos Valley, Chihuahua, Mexico, and the southem Quitman Mountains near Hot Springs south of Sierra Blanca (Fig. 15). MALONE MOUNTAIN SECTION TORCER FORMATION21 Nomencl<úure.-The name Torcer is here applied to the por­tion of the section at and near T_orcer (formerly Malone} station on the Southem Pacific Railway west of Sierra Blanca which is of early Neocomian age, overlies the Jurassic and underlies the Dufrenoya (Gargasian} level. The type locality is taken in Malone Mountain, though exposures occur also in Malone Hills in the Bat about a mile east of the station, and in the southem and western foothills of Malone Mountain. This name covers the Cretaceous portion of Cragin's "Malone formation," that name having heen restricted to rocks of Jurassic age. The thickness of the Cretaceous 11.tiur•ture.-Tatr, 1573; Stanton, 331; Cragin, 331; Kitchin1 944; Baker, 46, 55; Burck­ hardt, 181. Tke Geology of Texas-Mesozoic Systems 287 portion is, according to the records, more than 831 feet. The forma­tion helongs to the emended Trinity group of the Comanche series. Stratigraphic position and contacts.-The following section by Taff (1573, p. 726) is selected from among several studied, and is interpreted in accordance with the facts published later by Stanton (in 331) and Baker (46, 55). SECTIO OF CE TRAL MALO E MOU TAIN NEAR TORCER STA­TIO (Modified from Taff) : Torcer /ormation (Eocretaceous): (These beds are contínued farther south and west.) Feet 1.22 Limestone, flaggy, compact and finely crystalline, blue to pale yellow, weathering yellow or brown__________________ ___ ___ _______ 100 2. Limestone conglomerate, maximum______ __ _____________________ 10 3. 1ilky white calcite___________ _____________ ______ ________ 2 4. Limestone, blue, slightly siliceous ; pelecypods, gastropods; /resh water facies; this bed may duplicate other limestones in the section__________ 100 5. Calcareous, ferruginous, sandy grit______________________________ 5 6. Siliceous limestone, with chert and limestone pebbles____________ 45 7. Limestone, light blue, weathers yellow, compacL_____ 4 8. Shale, conglomeratic, calcareous, black, weathers purple______ 10 9. Pisolitic limestone conglomerate with siliceous matrix, sorne chert pebbles ------------------------------20 10. Persistent rusty conglomerate: hard conglomerate, brown, rusty, cal­ careous, partly siliceous, matrix, containing chert and limestone pebbles 40 ll. Limestone, thin-and thick-bedded alternating, siliceous, gray______ 450 This basal portion of the Torcer has been subdivided by other 'Hiters. Its upper 250 feet is stated by Stanton to contain a fresh water limestone with fossils. Beneath this is about 35 feet of sandstone with marine fossils. At a level about 125 feet above the base (Stanton's To. 25, in 331, p. 26 ), there is a 15-foot limestone containing Pygurus sp., Gryphaea me,.,icana, Pinna quadri/rons, and Pleuromya inconstans. 12. Calcareous grit and cherty conglomerate_____________ __ 15 13. Calcareous sandstone and siliceous limestone. A thick, light buff to yellow brown sandstone in this position above Briggs switch yielded Astieria and another ribbed Cretaceous ammonite. From this limestone (Stanton's No. 22, in 331, p. 26) fragmentary fossils including am­monites were reported_ _ ___ _ _________ _ _ _ ___ _ 30 ~Taff's numbers are used. Malone forrnation, restricted (Upper Jurassic) : 14. Lirnestone, light blue siliceous, with occasional bands of siliceous shell breccia. Nos. 9 and 10 of Stanton's section II (331, p. 27), presurnbaly the lower part of this bed, consist of blue lirnestones with echnioids and large Nerinaea, and shales_______________________________________________________________________ 300 15. Massive conglornerate, with siliceous lirny rnatrix and lirnestone pebbles. Similar conglornerates occur in the Briggs section___________________ 150 16. Alternating lirnestone and conglornerate layers: the strata are each 10-20 feet thick; the limestones are siliceous; there are sorne shaly strata. At various levels from 220 to 320 feet above the gypsum, Stanton has reported severa! J urassic fossils, including ldoceras schucherti, Kossmatia clarki, nautili and pelecypods. Stanton's Malone Mountain bed No. 13 (at about 188 feet above the gypsum) contains Jurassic fossils. Leonard formation (Perrnian) : 17. Limestone, light blue; locally absenL---------------------------------------------------40 Sorne limestones overlying gypsum in this vicinity contain Richthofenia, ammonoids, and other Perrnian fossils. 18. Gypsum, white, granular_________________________________________________________________ 110 19. Limestone, dark blue granular, minutely cleaved, metamorphosed, and veined with calcite-----------------------------------------------------------------120 20. Gypsum -----------------------------------------------------------------------------50 21. Limestone, siliceous, light gray_________________ _ ________________________________________25+ At many places the thickness of the limestone above the gypsum is variable, and the gypsum is so squeezed and distorted as to involve the adjacent limestones. The incompetence of the gypsum permits much crumpling in its vicinity, and as a result the exact sequence and relations of the basal beds cannot be everywhere seen, especially where folding is intense. In Stanton's Malone Mountain section three gypsums are reported, alternating with limestones or with sorne con­glomerate. How much repetition -exists, or whether more than one gypsum is present, requires further field study. The following interpretation of the stratigraphy is made from the published sections of Taff (1573), Cragin (331), Stanton (in 331), and the structural profiles of Baker (46, 55) , together with observa­tions by the writer. Permian.-At or near the top of the Permian section, a 100-foot bed of gypsum occurs. Locally, perhaps everywhere, it is overlain by a limestone bed, 40 feet thick in Taff's section (1573, p. 726, across Malone Mountain near Torcer station); in this limestone Richthofenia occurs (46, p. 11) . Altogether the visible Permian section consists of two (or ?three) gypsum layers interbedded with The Geology of Texas-Mesozoic Systems 289 limestone. The maximum thickness exposed is recorded as 4 70 feet. s Fig. 14. Profile from Malone Mountain to Finlay Mountains, south-central Hudspeth County, Texas. 4=: Valanginian (Astieria) 2 == Permian (Richthofonia, ammonoids) 3 == Tithonian (Kossmatia aguilerai) ; 1 == Permian gypsum Kimmeridgian (Idcceras) furassic.-Taff's numbers 16-14 (1573, p. 726) and Stanton's 6-17 (331, p. 25) and 2-10 (331, p. 27) are considered Jurassic. The maximum recorded thickness is 580 feet. Fossils from about the middle of this section recorded in Stanton's lists 5 and 7 (331, p. 18), include Idoceras schucherti and Kossmaüa clarki; the former demonstrates Kimmeridge age, and the latter the same or a slightly higher age. KossmaJ,ia aguilerai, found in the foothills west of Malone Mountain and about 2 miles north of its southern end, in a level not tied into those of the main sections, is regarded by Spath as possibly Tithonian (944, p. 458) . The basal half of the Jurassic consists of conglomerates, sandstones, and conglomeratic sandstones and limestones; sorne black, hituminous shales weathering brownish to purple-lavender are Kimmeridgian and nearly typical of shales of that age in northern Mexico; the remainder, about the upper one-third of the Jurassic, is predominently limestone. Possibly higher levels are filled in on the southern part of Malone Mountain, a feature as yet insufficiently checked. Cretaceous.-Only 830 feet of Cretaceous is recorded, sorne of it possibly repeated, and all apparently early Neocomian. Farther $Outh and west, near Malone Mountain, upper beds come in. No complete survey of the section up to the Dufrenoya (Travis Peak) level has yet been published. The Cretaceous section begins with 25 to 45 feet mostly of sandstone, siliceous limestone, cherty and calcareous conglomerate, and grit. These basal strata contain am­monites at various places. In one of the sandstones near this level, at the top of the ridge south of Briggs switch, Baker found an Astieria, and in a nearby limestone, a ribbed Cretaceous ammonite. Above this comes 450 to 550 feet of mostly limestone. This is capped by a 40-foot bed of typically rusty-weathering conglomerate, containing siliceous grit and pebbles; this bed is persistent and easily recognized. lt is overlain by 300+ feet mostly of limestone, with sorne conglomerates, grits, and shales. This upper part of the section is notable for containing two or more levels of fresh-water limestones with Unio, Viviparus, and other genera. One such fresh­water level, may underlie the rusty conglomerate ( which Burck­hardt refers to the Jurassic) . This fresh-water section is interesting through demonstrating that Malone lies on the very margin of marine sedimentation, and through being a reduced Texas repre­sentative of the Wealden facies. Fossils and age.-The age relations of both Jurassic and Cre­taceous at Malone Mountain have been discussed by many writers ( see section on J urassic) , and the general features are now well known. The Cretaceous portion is mostly of infra-Cretaceous (Val­anginian) age, an ammonite (Astieria) and certain pelecypoda (Trigonia, Ptychomya) being most conclusive as evidence, but further research will doubtless reveal more fossils of both this and other Cretaceous ages. Spath's and Uhlig's statements concerning Malone ammonites have already been quoted. Kitchin (944) summarizes the evidences for Valanginian age, as shown by the Malone pelecypoda, in part as follows : (1 ) Trigonia caldero ni (Castillo and Aguilera) is suggestive of T. vau and T. v-scripta. (2) Trigonia goodelli is analogous to T. recurva Kitchin. (3) Trigonia vyschetzskii belongs to the section Pseudo-quadratae (Stein­mann) ,23 characteristically and exclusively Lower Cretaceous everywhere. (4) Trigonia proscabra is distinctly like Neocomian species from Chile. (5) No Malone Trigonia belongs to the section Undulatae, nor is that section exclusively Jurassic. The sculpture of T. rudicostata and T. conferti­costata has its closest analogues in Costatae from the Trigonia beds in the Oomia series in Cutch (Kachh) . (6) The genus Ptychomya, represented at Malone by P. stantoni, is else­where known only from the Cretaceous. (7) The characters of Astarte ( Eriphyla) malonensis recall those of Lower Cretaceous species in the South Andean and Africo-lndian regions. •Steiomann, G., Die Gruppe der Trigonia pseudo-quadratae, N. Jahrb. f. Min., 1882-1: 219­ 228, pis. VII-IX. The Geology of Texas-Mesozoic Systems 291 (8) Some Malone oysters, as Gryphaea mexicana and Exogyra potosina, likewise common in northem Mexican localities, have the characters of Lower Cretaceous species. (9) Pleuromya inconstans Cragin shows much resemblance to forms of Panopea occurring in the Lower Cretaceous in Europe. The ammonites of contemporaneous beds have been described from many regions, such as the late Valanginian Uitenhage beds of South Africa24 and more immediately, Valanginian ammonite­bearing beds in northern Mexico. 25 The Astieria sp. and several other ammonites from Malone localities have not yet been precisely identified. It is possible that other levels, in both the Jurassic and . the Cretaceous, will be identified near Torcer. CONCHOS RIVER VAl.LEY SECTION Burckhardt (181, pi. 12 opp. p. 160) has correlated the Morita formation of the Bisbee section, the arkoses, conglomerates, and shales below the main limestone near Cuatro Ciénegas, Coahuila, and the Mountain bed of Taff (at Quitman Gap), with the Haute­rivian-Barremian sandstones containing copper veins near Las Yigas on the Rio Conchos (Las Vigas formation of Burrows) . The basal red sandstones and shales near Hot Springs are apparently a continuation of these beds. The beds are overlain by the Gargasian marls and limestones containing Dufrenoya and lower Albian with Douvilleiceras, which are overlain by the thick Orbizolina-bearing Glen Rose (Trinity) limestones. Sections in northern Mexico.-Two noteworthy sections of Eocretaceous are those near Cuatro Ciénegas, Coahuila (181, pp. 83, 144-147), and in the Conchos Valley, Chihuahua (181, pp. 83, 147-149). In the former section the early Cretaceous marginal and neritic beds consist mainly of (in ascending order): (a) clays altemating with sandstones or limestones, 800 ft., containing Trigonia aff. vau and other pelecypoda; (h) arkose and conglomerate; shaly SISpath, L. F., On the ammonites of the Speeton clay and the oabdivWona of the Neocomian, Geol. Mag., Vol. LXI, 1924; Spath, L. F., On the cephalopoda of the Uitenhage beds, Ann. S. lúr. Mua., 28: 131-157, pis. XIII-XV, l fig., 1930; Kitchin, F. L., The lnvertebnte fauna and paleontological relationa of the Uitenhage aeriea, Ann. S. lúr. Mua., 7: 21-250, pla. II-XI, 1908. 95Jl0ae1 Emil, Alcunu faunas cretacicas de Zacatecae, Durango y Guerrero, Inat. Geol. Méxi~o, Bol. 42, 219 pp.• 19 ple., 1923; Burckhardt, C., Faunes jurauique• et crétaciquea de , San Pedro del Gallo, Imt. Geol. México, Bol. 29; del Castillo, A., and Agnilera, J. G., Fauua fosil de la Sierra do Catorce. San Luim Potoei, Bol. Com. Geol. México, No. 1, 1895; Burckhardt, C., La fanne jan.Mique de Mazapil avec un appeadice nr les foHiles du Crétacé inférieur, Inst. Geol. México, Bol. 23, 1906. ­ at base, 765 ft.; (e) sandstone and arkose, 2300 ft.; (d) sandstone and arkose, 200 ft. These are overlain by Gargasian, containing Dufrenoya texana. The Zambrano well (N.E. Coahuila) contains a somewhat similar arkosic section. The Conchos Valley section consists of (a) Boquilla26 slate, possibly Paleozoic, 1000 ft.; (b) Plumosa formation, possibly Jurassic, limestones, with subordinate quartzite, conglomerate, and shale, 1150 ft.; (e) Las Vigas forma­tion, Neocomian, basal half sandstones with four commercial copper veins, upper half shales with thin sandstones, sorne fossil plants, 1940 ft.; ( d) Cuchillo formation, its basal 1500 ft. of gypsum with rock salt near base, shales, limestones with Dufrenoya and Douvilleiceras (Gargasian), more clayey to south, 2000 ft.; Aurora ("Mountain") limestone, cherty, fossiliferous limestones with big springs, the main mountain-forming rock of the region, 1500 ft. This fa overlain by the Upper Cretaceous. NNW S.SE. Fig. 15. Profile from Cornudas Mountains (Texas-N. M.) to Conchos Valley south of lndian Hot Springs. Northwards the section thins greatly, transgressive overlap involves succes­sively higher Comanche levels up to the Duck Cxeek, and the sandy marginal facies becomes progressively younger to the north. The following letters indicate persistent fossil zones: M = Mortoniceras (Washita species) G = Gryphaea navia (.Kiamichi) F = Rudistids (Fredericksburg) x = Orbitolina texana (Glen Rose) E= Exogyra quitmanensis (Quitman, Cuchillo) D = Douvilleiceras and Parahoplites (Cuchillo) T = Trigonia aff. taffi (Cuchillo) SOUTHERN QUITMAN MOUNT.AINS SECTION The southwestern part of these mountains near Hot Springs (Eagle Mountain sheet) contains a thick section of early Cretaceous beds reaching from an unknown base up to the Orbitolina (Glen Rose) 21Name preoccupied by Udden's Boquillae, 1907. The Geology of Texas-Mesozoic Systems 293 limestone. The beds mostly dip eastward in uninterrupted succes­sion, with sorne folding and minor faulting, and afford a more straightforward section than the Malone Mountain district. The basal observed formation is the Las Vigas, a large thickness of red sandstones in beds up to 50 feet thick, gray sandstone, red sandy shale, and gray shale. These beds are generally poor in fossils. They are of early Neocomian age. They are overlain by severa! hundred feet of gray limestones and marls, of Gargasian and perhaps Lower Albian age, referred to the Cuchillo formation. These are overlain by Glen Rose equivalents. LAS VIGAS FORMATION N omenclature.-This formation was described, without age assignment, by Burrows27 in 1910, from exposul'es in the Conchos River valley in northern Chihuahua, west of Presidio, Texas. According to Burckhardt's (181, pp. 83, 148-149), interpretation, it overlies the upper Jurassic Plumosas formation of Burrows. It consists of gray, black, and red quartzitic sandstone, gray limy sandstone, black shales, wd sandy limestones. Sorne of the sand­stones and shales contain veins of copper. The upper portion, transitional to the overlying Cuchillo formation, contains gypsum ar.d fossiliferous limestones (Exogyra}. Its thickness in the Conchos Valley reaches 1968 feet ( 600 meters). Outcrop in southern Quitman Mountains.-On the Sierra Blanca road, within 2 miles of Hot Springs, the east-dipping red sandstones, siltstones, and sandy clays beneath the fossiliferous Gargasian­Upper Aptian marls are more than 500 feet thick. The section here · iucludes the following rocks: 6. Rhyolite tuffs and extrusive igneous. S. Limestone with some red sandstone, siltstone, and red beds. Near north exit of Hot Springs road onto Quitman Arroyo flat. 4. Cuchillo formation . (Gargasian) and Lower Albian) : Thin gray or blackish limestones and gray marls interbedded. At Quitman Summit on the Hot Springs road. Fossils: Douvilleiceras, Parahoplites (severa} species}, Trigonia aff. taffi Cragin, Exogyra quitmanensis Cragin, Trigonia spp., Alec­tryonia aff. carinata (or rectangularis), and many others. Thickness ( esti­mated), 400+ feet. 3. Massive gray limestone. No fossils collected. Thickness ( estimated), 200 feet. 27Burrows, R. H., Geology of northern Mexico (eastem C:h.ihuahua), Bol. Soc. geol. Mexicana,. 7: 1-15, 1910. 2. Gray calcareous clay with t.hin bands of nodular clayey limestone. No fossils collected. Thickness (estimated), 250+ feet. l. Las Vigas formatiQn (Eocretaceous): Red sandstone in beds up to 50 feet thick, some red sandy shale, gray sandstone in members up to 50 feet, gray sandy shale; near top of formation, a little shale and limestone. No fossils collected. Thickness (estimated), 500+feet. The base was not seen. These heds dip eastwards, at places steeply. A considerable area of fossiliferous marls and limestones is exposed on and near the road, ahout 5 miles north of Hot Springs. In a long valley at a sharp hend of the Río Grande, 1 % miles downstream from Hot Springs, Messrs. Baker and Arick and the writer collected Para­hoplites, Douvilleiceras, a large ammonite, and various Trigonia. This level is the same as that at Quitman Summit, and lies several hundred feet helow the main Orbitulina zone. So far, Dufrenoya, a marker for the Gargasian (= Upper Aptian), has not been found here, and the Cuchillo fauna marks the lowermost Alhian. How­eYer the similarity with the ~xican Cuchillo leads to a provisional correlation with that formation. The correlation of the underlying red sandstones with Burrows' Las Vigas formation is eyen less well estahlished, on account of lack of fossil evidence, hut this is the nearest lithologically similar formation to which the lower beds at Hot Springs can he referred. CUCHILLO FORMATION Nomenclature.-Burrows (op. cit., p. 8) described this fornia­tion, without age assignment, from the Conchos Valley section north of the Kansas City, Mexico and Orient line, a short distance north of Presidio. It clearly overlies the copper~hearing basal Las Vigas sandstones, and underlies the heavy-bedded main limestone (Aurora of Burrows; Mountain limestone of Hill, not of Taff nor of Euro­pean authors; upper Glen Rose-Frederickshurg). The Cuchillo is identifiahle as the main horizon of Dufrenoya and Douvilleiceras, which have heen found at many places in this region. Bose collected them near the Aurora mine, 5 km. south of Cuchillo Parado, in the San Vicente valley in the Burro Mountains, southwest of Del Rio and in the Cañon de Vallas near Saltillo; and Burckhardt collected them from the Río Nazas in Durango. A similar fauna has long been known from the Travis Peak beds in western Travis County (783, 180a). •It contains Dufrenoya texana (Hill), D. justinae (Hill), The Geology of Texas-Mesoz~ic Systems 295 Pseudosaynella walcotti (Hill), and the overlying Glen Rose con­tains Parahoplites and Douvilleiceras. At several places in the rim of the Solitario, in nodular limestones above the basal conglomerate and above limestones containing .Exogyra quitmanensis, a large Pecten, and Nerinea {several species), there are lower Albian marls containing Douvilleiceras spp., Parahoplites spp., Procheloniceras n. sp. aff. a/,brechti-austriae, Nautilus neohispanicus Burckhardt, and other cephalopods. These may be referred to the Cuchillo. In this sense the Travis Peak would be in part the marginal facies of the Cuchillo. Outcrop in southern Quitman Mountains.-Nos. 2-5 of the pre­ceding tabulation, composed of fossiliferous marls and marly lime­stones outcropping on the Hot Springs road near Quitman Summit, are referred to the Cuchillo. Their age is Lower Albian, and, probably, in their basal part, Upper Aptian (= Gargasian). It appears that the ammonites here have considerable zonal thickness; the following expresses the supposed zonal arrangement in this locality: Glen Rose: 6. Orhitolina zone Cuchillo: 5. Exogy:ra quitmanensis}Douvilleiceras and 4. Trigonia taffi Parahoplites 3. Dufrenoya (?) Las Vigas: 2. Fossils not known l. Malone fossils ( ? ) The Malone Cretaceous apparently comes helow the main section of Las Vigas near the Hot Springs road. The Travis Peak is equiva­lent to zones 3-5. The hase of the Solitario rim section líes in zone 5. SYNCLINAL (OFF-SHORE) TRINITY SECTIONS Southern Hudspeth County.-ln southern Hudspeth County the Trinity rapidly thickens southwards and loses the marginal facies. V arious authors, not fully appreciating these two features, have given numerous overlapping names to Trinity heds south of the Southern Pacific Railway, as has been already mentioned. The Trinity section surrounding Sierra Blanca Peak, which consists of two formations: Etholen conglomerate helow, and Cox sandstone above, is in the marginal facies. On passing southwards the section thickens and passes into the offshore neritic facies, the formations becoming more marly and limy, especially near the top. Near Bluff Mesa, 3 miles south of Sierra Blanca station, Taff described the basal Yucca sand, overlain by the marly and limy Bluff formation. Near Quitman Gap, a basal 2000 feet of sandstone is called Cox by Baker, and Mountain by Taff, who recorded 4060 feet but failed to report its repetition by folding. It is overlain by a thick limestone and marl section, the Quitman of Taff. Passing southwards to neai Hot Springs the section further thickens and is here divided into equivalents of the Las Vigas, Cuchillo, and Glen Rose formations. The accompanying profile depicts the writer's opinion of the general relation of these various formations, based on the known zonal fossils ( Fig. 15) . Taff's (1573, p. 730) "Mountain" bed was mentioned above. The type locality of his "Yucca" bed is in Yucca Mesa at the west end of Devils Ridge, 3:112 miles south of Sierra Blanca; the type locally of his "Bluff" bed is in Bluff Mesa, 2 miles southwest of Sierra Blanca; and that of his "Quitman" bed, in Quitman Gap across the Quitman Mountains, about 9 miles southwest of Sierra Blanca. Much further field work in this faulted and alluvium-covered region is necessary to define the relations of these formations. They are in part equivalent to each other. The Yucca bed includes the basal, more sandy and conglomeratic strata in Devils Ridge and Yucca Mbsa. It consists generally of alternating arenaceous limestone and quartzitic · sandstone, with flaggy sandstones and limestones, pisolitic limestones, shell debris, and limestone breccias and conglomerates. At the top is a caprinid limestone. Fossils are rare; Arca, Ostrea, and caprinids are recorded. The Bluff bed overlies the Yucca bed. It consists of alternations of sandstone or quartzite with oyster-bearing limestones. Recorded fossils are Arca, Exogyra texana, large flat oysters, other oysters, Orbitolina texana, and caprinids. Orbitolina and caprinid limestones occur near the top of the Bluff bed. It is to be emphasized that these two formations occur together in the ridges and mesas near Sierra Blanca, and that the Quitman and Mount.ain beds occur in another region, Quitman Gap, separated from the first by large The Geology of Texas-Mesozoic Systems 297 faults which obscure the stratigraphic succession. Baker has mapped a major overthrust in this region. At Quitman Gap, the Quitman bed is described as consisting of, basally, calcareous flaggy and yellow friable sandstone, containing Exogyra quitmanensis Cragin, Ostrea aff. owenana Shumard, Pecten, and a peculiar Trigonia-Iike fossil; medially, a massive siliceous shelly limestone; and at the top a massive caprinid limestone. A total thickness of 330 to 380 feet is recorded. According to Taff, the Quitman is overlain at Quitman Gap and in the west flank of the southern Quitmans by the Mountain bed, 4060 feet thick. Baker states that these beds are repeated by compressed folding and gives them a thickness of about 2000 feet ( 46, p. 20). Taff describes them as consisting of members of varicolored flaggy and calcareous sand­stones alternating with members composed of limestones, marbles, and sandstones. Near the base there are sorne oyster shell lime­stones. The Quitman bed, with Exogyra quitmanensis, resembles the beds at Quitman Summit (Cuchillo) , and the Mountain bed in lithology resembles the Las Vigas forniation. The Bluff bed contains Orbito­lina in abundance, and corresponds to the Glen Rose. In the Hot Springs section the abundant Orbitolina zone is severa! hundred feet above the main Exogyra quitmanensis zone. Val Verde-Maverick counties (578, !j78a, 1625, 1681.-Near Del Rio the entire Comanche~ has been penetrated in severa! wells, and metamorphosed slates and soft shales found beneath. In Maverick County wells have not reached pre-Comanchean rocks. The follo~­ing are reported thicknesses of Glen Rose in the area: Rock Springs, 500 ft.; Juno, 500 ft.; Del Rio, 900 ft.; north line of Uvalde County, 1000 ft.; Uvalde County, maximum, 2250 ft.; Maverick. County (Sullivan, Chittim leases), 3600+ ft. Details of the Travis Peak are lacking in many wells. The Glen Rose contains large amounts of limestone, much of it silty, sandy, or marly; mineralized waters with calcium sulphate, magnesium sulphate, and sodium chloride occur; and cavities containing pure sulphur or celestite, veins of gypsum, and small veins or stringers of anhydrite are found. On the large nortliwest-trending Chittim structure, the Glen Rose pro­duces a large quantity of casinghead gas. The Cretaceous section in northern Coahuila between the Burro Mountains and the Rio Grande has been described by Dumble (480). The Burro Moun­tains are a large domal uplift dissected by deep canyons, which however do not seem to reach the pre-Cretaceous rocks. C. L. Baker repotts the section to be as follows: Washita-Fredericksburg mountain-forming limestone, 1200 feet; greenish-gray Walnut marl with calcareous concretions and many marca­site fossils (Exogyra texana, echinoids, etc.), 50 feet; Glen Rose alternating beds of marly limestone and purer limestone, the base not seen, 2000 feet. Near the base of the Glen Rose section, an ammonite (Douvilleiceras?) was found. Georgetown, thinned Grayson (Del Rio), Buda and Eagle Ford (Boquillas facies) form a 50-mile dip slope east of the Burros. Bexar County (888, 1145, 1401, 1402) .-From about 600 feet on the outcrop, the Glen Rose thickens gulfwards to 1785 feet (at 3097-4882) in the Milham Corporation, Eastwood No. 1 well in southwestern Bexar County. Here the Travis Peak is 479+ feet thick {at 4882-5361 ft., T.D.). The Glen Rose consists almost entirely of yellow, or blue, sandy limestone, dark colored sandy and shaly limestone with oi~ shows, and, in the basal 750 feet, of gray-yellow limestone. The Travis Peak consists of light, fine­grained sandstone and sandy shale with minor seams of limestone and quartzite, and basally sorne grits and conglomerates. The Quitman-Eagle Mountains, the Maverick and the Bexar sec­tions of the Trinity were deposited to great thickness in subsiding synclines of the Rio Grande embayment, and, in most levels, pre­served shallow water conditions, with deposition of coarse sand­stones, conglomerate, and anhydrite. The. Louisiana section of the Trinity likewise contains a large thickness of shallow water sedi­ments. MARGINAL TRINITY SECTIONS In consequence of the landward (northward) overlap of Trinity sediments onto the old basement rocks across Texas, the Trinity group forms a wedge-shaped mass of rocks, the thin edge pointing inland, and the thicker, buried, seaward extension pointing gulf­wards. The Trinity rock sheet reaches inland to an irregular line (Fig. 16) running approximately through El Paso, Fort Stockton, Big Spring, and thence across the central area, denuded of Coman­chean rocks, to southern Oklahoma; south of this line there are restricted areas in which Trinity rocks are absent and Fredericksburg rests directly on the old land. The Geology of Texas-Mesozoic Systems 299 Louisiana sections.-The Trinity section in the northern Louisiana oil fields shows different formations and facies different from those on the outcrop. The Trinity memhers are, in descending order: Upper Glen Rose lime· stone, Anhydrite zone, Lower Glen Rose limestone, non-marine red heds, Basal Trinity sand, basal fossiliferous day (pre-Trinity?). The following sections are recorded: Washita and PINE ISLAND­CADDO HOMER BELLEVUE 1600+ ft. red shale Fredericksburg and gumbo ; west flank of Caddo field ---Major erosiona! unconformity on tops of domes, removing Washita and Upper Glen Rose limestone Anhydrite zone Lower Glen Rose limestone (at top, Wickett oolitic limestone; below, D i 11 o n and Dixie pays) Red beds (non­ marine red shale) Basal Trinity sand Neocomian? o r Jurassic? elay Fredericksburg 200 ft. limestone 450 ft. anhydrite 900 ft. limestone ( Douvüleiceras) 2000-2515 ft. red beds thin not reached sediments--­ 850 ft. red and gray-black shale; sandy shale, sandy l i m e s t o n e, fine sand, sandstone; Ostrea, Pecten. 500 ft. sedimentary anhydrite interbed­ded with lime­stone; dwarf fos­sils. 1000 ft. gray-black shale and shaly 1i m e s to n e , red shale, sorne fine· san d a n d sand­ stone. not reached not reached not reached • 200-600 ft. lime­stone and clay. 500 ft. anhydrite 1150 ft. limestone, f o r a m Í' ni f e r a (M i l i o l i da e ) , Dierks, ostracoda Serpula. 991-1800 ft. red beds 1072 ft. white and red sand and sand­stone. 330+ ft. fossilifer­ous clay and lime­stone* (Bliss and Wetherbee No. 30, at 4972-5302 ft.) *Contains Polymorphina, Haplophragmium, Haplophragmoides, gastropoda and ostracoda. Exact age unknown; stated to resemble Cretaceoua. In facies, all Trinity rocks at the outcrop in Texas are epiconti­nental, and consist of two classes: (1) marginal sediments, con­glomerate, sandstone, sandy shales in the typical Travis Peak formation, sorne sandy phases of the Glen Rose, and the type Paluxy; and (2) an offshore, neritic facies, consisting of limestone and marl, as in the type Glen Rose. The marginal facies is char­acterized by clastic and detrital material, coarse sands, gravel, and conglomerate, red color, rarity of typical marine invertebrates, presence of fossil wood, cycads, dinosaurs, fish remains, and cross­hedding. The other facies contains limestone (shell breccias, coquina, or organically precipitated limestone), sorne of it of shal­low water origin and containing ripple marks, rain marks, mud cracks, dinosaur tracks, and coral reefs, sorne black shale, and anhydrite, sulphur, celestite, strontianite and mineral ·salts. In Louisiana deep wells there is a third, red bed facies, which may he of continental origin. Fig. 16. Extent and facies of the Trinity group in and near Texas.· Ruled area =landward margin of Glen Rose limestone wedge; dotted area =shore­ward extent of Antlers sand (heavier dots indicate actual outcrop). A-A, northern margin of Glen Rose. B-B, northern margin of Trinity sand. The Geology of Texas-Mesozoic Systems 301 The formations of the Trinity group have only local validity, because, if viewed regionally, they are facies of one continuous and laterally changing mass of sediments. For convenience they are here treated as local formations, with the reservation that on being traced into the marginal area the offshore units become lithologically similar. The Gillespie near Fredericksburg is a marginal, cycad­bearing facies of the upper Glen Rose. The Paluxy is a sandy facies of the uppermost Glen Rose. The Antlers in southern Oklahoma is the combined marginal equivalent of the entire Trinity group, and perhaps includes basal Fredericksburg strata. The limy and marly Trinity is marked by an upper Aptian and lower Albian assemblage of pelecypods and gastropods, corals (resembling those from the Tehuacán, San Juan Raya, and Puebla districts in southern Mexico), and ammonites (Dufrenoya, Para­ho plites, Douvilleiceras}. The marginal facies is marked by cycads (Cycadeoidea boesiana, C. bart-johnsoni}, wood, conifers, no angio­sperms, hrackish-water mollusca, and dinosaurs. Anhydrite.-In Arkansas, Louisiana, northern Mexico, and Texas, rocks of the Trinity group contain anhydrite. The De Queen lime· stone in southwestern Arkansas contains, along the outcrop, lenticu­lar masses of celestite and thin beds of gypsum, which thicken gulfwards and hecome massive heds of anhydrite. They are reported to he ahout 20 feet thick on the surface. At Pine Island-Caddo, there is about 450 feet of anhydrite hetween the upper and lower Glen Rose limestones; in the Homer field, _500 feet of sedimentary anhydrite, interhedded with limestones (fauna of dwarfed fossils); in Bellevue, 500 feet of anhydrite. Farther east, in the Richland field, and in the Bethany gas field, Panola County, Texas, the anhydrite thicknesses are as follows (612, p. 946): Richland field Bethany Eubanks No. 1 field Anhydrite ---------------------------------------------------28 5 Shale and limestone ____________________________________155 248 Anhydrite ---------------------------------------------196 238 Limestone --------------------------------------60 67 Anhydrite ------------------------------40 3 In Fannin Count}r, Texas, in a well on the Owens farm, anhydrite was cored at the depth 2656 feet, and the driller logged 50 feet of anhydrite. At 2675 feet, calcareous sandstone was cored. In the city well at Hubbard, Hill County, Dr. T. W. Stanton found anhydrite in cores at 2855 feet. Gypsum is logged (803, p. 557) at the depths 2848-2878 feet. The base of the Glen Rose in this well is at or near 2640 feet, and the well ended in Travis Peak at 3166 feet. In the North Currie field, the Sun Company's H. A. Swink No. C-1 had gypsum cuttings at a level of about 1225 feet below the "Tritaxia zone," which is located just above the top of the Glen Rose. In the Mexia field in E. L. Smith's Steubenrauch well, anhydrite cuttings were recorded at 1100, and gypsum cuttings at 1400 feet below the "Tritaxia" zone (969, p. 334). In the Kelly No. 1 well, Luling field, anhydrite was cored at the depth 4422 feet, its thickness being undetermined; at 4728 feet the base of the Cretaceous was reached. In the McAngus well at Elroy, eastern Travis County, the Glen Rose contains an · anhydrite stratum at the depth 2367 feet. The Travis Peak contains an anhydrite stratum cored at 2988 feet. At the outcrop in Maverick Cotinty, anhydrite occurs in the Edwards, and thin beds and veins of it occur at eleven levels in the Glen Rose. Gypsum occurs at the outcrop in the northern part of Gillespie County. In the Edwards, or Comanche Peak, limestone, 3 or 4 miles south-southwest of Menard, a few feet of gypsum is found in shallow excavations . . Gypsum outcrops in the Glen Rose near the mouth of Bull Creek, western Travis County. Burckhardt reports gypsum at the outcrop in the Conchos River region in northern Chihuahua, a short distance west of Presidio, Texas. Near the top of t~e Neocomian-Aptian copper-bearing sand­stones ("Las Vigas" of Burrows) near Coyamé, intercalations of gypsum and limestone seams occur. In the overlying Gargasian shales ("Cuchillo" of Burrows), gypsum and rock salt occur (181, p. 148); the rock salt has been locally exploited for a century. In Smackover field, Arkansas, the salt was found at depths of 5974-7255 feet, beneath the lower marine series of Trinity. Spooner2s says: "The age of the salt is not determinable, but the probability that it is older than Comanche is suggested." Celestite pockets and nodules are widespread in the Glen Rose in central Texas. Celestite.-Professor L. S. Brown has kindly furnished the follow­ing comments concerning the Trinity celestite in central Texas: '"Spooner, W. C., Bull. Am. Assoc. Petr. Geo!., 16: 602, 1932. The Geology of Texas-Mesozoic Systems 303 Concerning the deposits of celestite in the limestones, it is my opinion that these are of primary (syngenetic) occurrence. The evidence supporting this view is as follows: l. Petrologic Structures.-ln many cases the enclosing limestone shows distortion without fracturing, diverging and bending around the celestite nodule. This is easily seen only in case of the larger nodules, around six inches in diameter or more. In severa! cases, immediately above the nodule, bedding planes can be seen, showing no bending or other disturbance in the vicinity of the nodule, though succeeding strata contained similar nodular inclusions. These features are especially evident in the Mt. Bonnell region. 2. Distribution.-Celestite nodules, similar in appearance, are found in a rather wide belt through central Texas. Ordinary stratigraphic descriptions make no particular observations on celestite, but, so far as 1 am aware, the occurrence of the mineral is limited to the Glen Rose limestone, though 1 have no particular reports of its absence from other horizons. This strongly bespeaks marine distribution, and almost definitely excludes secondary entry. 3. Associated Minerals.-Within the Glen Rose, gypsum, anhydrite, and celestite occur in similar manner and in some abundance. Hill has reported epsomite and strontianite, but 1 have not observed either. However, the occurrence of ali of these minerals of similar character is indicative of marine concentration. 4. Precedent.-The literature contains severa! descriptions of syngenetic celestite in limestones, notably severa! papers by Kraus on the "vermicular" limestones of New York, Put-ln-Bay Ohio, etc. ANHYDRITE, GYPSUM A D CELESTITE LOCALITIES IN THE CRETACEOUS * = underground occurrence TRINITY GROUP Feet Louisiana-Pine Island-Caddo (anhydrite) ---------------------------------------450* Homer field (anhydrite) -----------------------------------500* Richland field (anhydrite) -------------------------------244* Bellevue field (anhydrite) ------------------------------------------500* Arkansas-DeQueen outcrop (gypsum, celestite) --------------------------------20 Texas- Bethany field, Panola County (anhydrite) __________________________________246* Northern Shelby County, near Paxton (anhydrite) ----------------------------* Fannin County, Owens farms (anhydrite) __________________________________ 50* Parker County (anhydrite) -----------------------------------------------------­ Hill County, Hubbard city well (anhydrite) ______________________________________ 30* Navarro County, North Currie (gypsum) _______ ___________________ * Limestone County, Mexia, (anhydrite, gypsum) -----------·------* Comanche County (anhydrite ) ? ------------------------------------- Somervell County, near Glen Rose (celestite) ________________________________ * Caldwell County, Luling (anhydrite) -------------------------------* Lampasas County, near Nix (celestite) ___________,____________________ Travis County, Elroy (anhydrite) ---------------------------------------* Feet Williamson County, near Leander (celestite) _______ __ ___________________ Travis County, Bull Creek (gypsum) outcrop____ _ _____ _______ Travis County, Mt. Barker (celestite) ______________________ Milis County, outcrop (gypsum) _ _ ___ _____ ______ ____ • Val Verde County, Del Río (gypsum}_____________________________ Uvalde County, Southern Crude O. P. Co., Washer 1 (anhydrite in Glen Rose at severa! levels) ____ __________ ______lOO+* Chihuahua-Conchos River west of Ojinaga, outcrop (gypsum) ---------------------­Coyamé, Las Vigas copper-bearing sandstone (gypsum) ; Cuchillo shales (gypsum ) --------------------------------------­ FREDERICKSBURG GROUP: Maverick County, Edwards outcrop (anhydrite) -----------------------­ Menard County, near Menard, Edwards outcrop (gypsum) __________ 5 Kinney County, Fredericksburg outcrop, Cummins (gypsum) _________ Gillespie County, Doss Valley road (alabaster gypsum}__________________ 10 Gillespie County, Mason road 13 miles nw. of Fredericksburg, (7 ft. alabaster) -------------------------------------­i\Iaverick County, Rycade Chittim 2 (20 ft. rock salt, top Edwards) Van, Van Zandt County (Trinity gypsum leve!), severa! wells_____ • Shafter section (1623, 53) .-The Trinity of the Shafter section is ~omposed of two formations: B. SHAFTER formation ( =Glen Rose) .-Thin to medium-bedded, but mostly massive limestone, which differs from Fredericksburg limestones in being non-cherty; sorne interbedded limy marls. Thickness, 700 feet. Fossils: Porocystis in two zones, at top, and 170 feet above base; Monopleura marcida, 250 feet ahove base; Orbitolina texana and other species, from base to within 230 feet of top; Caprina occidentalis and C. crassi/ibra, at about middle; Exogyra texana and Engonoceras cf. complicatum Hyatt, in upper 200 feet. A. PRESIDIO formation ( = Travis Peak) .-Unconformably overlies the Permian Cíbolo limestone. It consists largely of sandstone, sand, sandy clay and conglomerates; so-called mortar rocks (conglomerates and lime-cemented sand and sandstone) occur throughout the formation. At the base there is 26 feet of indurated gray mar! and clayey limestone with a few calcareous and organic fragments. In the upper half, Orbitolina texana, Pecten, Trigonia. The thickness is 400+ feet. The increased thickness of basal Trinity from the Conchos River "alley north-northwest to Torcer station coincides with the extent of a narrow arm of the late Jurassic-early Comanchean sea. The sections a short distance to the east of this sea, as at Shafter or in the Eagle Mountains, consist of sandy and marginal Travis Peak and Glen Rose equivalents, but lack the basal Comanchean forma· tions. The Geology of Texas-Mesozoic Systems 305 Solitario, Brewster-Presidio counties (1249, 1436) .-The Trinity group is exposed in the basal part of the inner rim of this unroofed dome, as 1000 feet of beds dipping about 45° radially outwards. The basal stratum is a thin ( up to 50 ft.) , massive, hard, silicified conglomerate, predominantly red, composed of angular cobbles of quartz, novaculite {from the eroded Hercynian ridges of Devonian Caballos novaculite in the Solitario basin), a little limestone, and other materials. The basal Trinity unconformably overlies at various points a variety of complexly folded and overthrust Paleo­zoic formations. Above the basal conglomerate there is locally fossiliferous limestone and marl, and generally a thick felsite sill encircling the rim. This is followed by thick fossiliferous Glen Rose limestone and marl in thin-bedded to massive strata, with Exogyra quittnanensis, Pecten, large sp., and gastropoda. Near the base they contain Douvilleiceras, Parahoplites, and other fossils. Near the middle are several zones with Orbitolina texana in great profusion. At many levels there occur echinoids, gastropods, and pelecypods, and the following fossils similar to those occurring in the W ashita: H aplostiche texana, N autilus aff. texanus, Kingena aff. wacoensis, Alectryonia aff. carinata, and others. Near the top is 50 to 75 feet of shell marl with predominantly Fredericksburg fossils, including Exogyra texana, which is assigned to the Walnut {Fig. 9). Southern Arkansas (392, 1113a, 1114) .-On the outcrop, from McCurtain County, Oklahoma, through Cerrogordo, Arkansas, where the Goodland and Kiamichi have their easternmost outcrop, to west of Antoine, the Trinity sands are overlapped by Woodbine. and higher Gulf fonnations. Farther east the basal Gulf formations are successively cut out, and the overlap involves successively higher members, until, in northeastern Arkansas, the Tertiary supposedly was locally in contact with the basement rocks. The Trinity dips southwards at · the rate of about 100 feet per mile and, near the Arkansas-Oklahoma line, aggregates about 100 feet in thickness. lt consists mostly of sand, with sorne quartz and other grave} from the under­lying beveled Paleozoics, and with four lenticular members, in ascending order as follows: Pike grave} lentil, a basal member, 100 feet thick or less, which thins westwards; Dierks argillaceous, fossiliferous limestone member, 40 feet thick or less, thinning westwards; Holly Creek red clay, sand, gravel, up to 300 feet (1679, p. 1079); Ultima Thule gravel lentil, 100 feet thick or less, thinning to east and found only in western Arkansas and in McCurtain County, Oklahoma, where it overlaps westward onto the Paleozoic basement rocks; De Queen limestone lentil, maximum thickness 72 feet, thinning and over­lapping to the west. The De Queen is notable for containing on the outcrop a 20-foot hed of gypsum, which can he traced southwards down-dip, into the anhydrite of the northern Louisiana oil fields. Both limestone lentils contain typical Glen Rose fossils: Glauconia branneri, Eriphyla pikensis, Ostrea frank· lini, and others. Both apparently pass in a west-southwest line underground across north Texas and connect with the thin limestone interfingerings of the northern Glen Rose into the Antlers sands in Parker and Wise counties, Texas. The remaining Trinity s¡md above the De Queen is called Paluxy (1679, p. 1071) • Southwards from the outcrop the Trinity rapidly thickens. A well in Little River County, Arkansas, contains a thickness of probably more than 2500 feet of Trinity. For the suhsurface section in northern Louisiana, see page 299. Southem Oklahoma.-Westward along the outcrop from Cerrogordo, Arkansas, the traceable Trinity members overJap out against the upward slop· ing Paleozoic basement. Presumably to the northwest only the higher members of the Trinity are present; but these levels have not been identified and are included in the Antlers sand, the marginal facies of the entire remaining Trinity section in this area. South of the turning point of the Comanchean formations in northwestern Grayson County, the Antlers has a north-south strike, and in Cooke County thin fingers of Glen Rose limestone appear. The Antlers in southern Oklahoma is a whitish-gray, locally varicolored, quartz packsand, nearly devoid of fossil. Gould records a dinosaur in ·it (626). For severa! miles east of Ardmore along the southern outwash slope of the Arbuckles, the Antlers received much dissolved calcium carbonate from the mountains, uplifted and actively eroding during early Comanchean times. Locally it is a limy conglomerate, containing many limestone pebbles and boulders. The Antlers has a thickness of 600 feet or less. It consists mostly of fine, light colored, incoherent packsand, with lesser amounts of basal and intraformational conglomerate of quartz and chert pebbles, locally cemented to quartzite, and red or bine shale, and thin calcareous sandstones. The basal conglomerate, usually 25 feet thick or less, consists of loosely cemented, cross:bedded sand with streaks of clay, and interbedded conglomerate of rounded-to-subangular chert and quartz pebbles. · The formation contains near its top Ostrea crenulimargo Roemer and Exogyra texana, and locally car· honized wood. Large deposits of silicified driftwood are recorded. Texas outcrop.-The Trinity group thickens on passing from the Red River valley southwards into the Mineral Wells-Fort Worth· East Texas geosyncline, and on passing gulfwards from the houndary between the o:ffshore and marginal facies. This boundary may be taken at the northern and western margin of the outfingerings o{ Glen Rose limestone into the Antlers sand (1394, 1679, 1574). The margin follows a line running from near Texarkana westward (underground) across northern Denton County, across Wise, Parker, northern Comanche, and eastern Brown counties ( outcrop), thence in a large reentrant {removed by erosion) down the Colorado River valley, across Gillespie County ( outcrop) , westward across the The Geology of Texas-Mesozoic Systems 307 southern part of the Edwards Plateau ( underground) , through northern Edwards and Val Verde counties to the .Pecos south of Pandale. W est of the Pecos the thinned margin of the Glen Rose occurs in the northeastern quadrant of the Marathon basin (Puring­ton ranch, and near Gap Tank) on the outcrop, sporadically near Fort Stockton off the high structures ( underground), south of Kent ( where absent on outcrop), between Black Mountain ( where absent) and Sierra Blanca (where present), westwards to near El Paso ( where unreported) . South and east of this line, the Glen Rose limestone with its normal marine fauna is present; north of the line, the marginal sandy equivalents are present over a strip of variable width, 100 miles or less generally, but formerly extended farther inland for an unknown distance. The presumed northerri limit of Trin'ity deposition is shown on Fig. 16. A section (Fig. 17) from Cooke County southward through Den­ton to Fort Worth shows (1) that the Glen Rose limestone fingers out to the north into the Antlers sand facies; and (2) that the Trinity group maintains a nearly uniform thickness in these two facies, and, therefore, that much of the Antlers is of Trinity age. In the more northern wells, one thin lentil is logged as lime (in Hampton well, 11 feet); farther south three (Denton City, Lewis Atkins) · or four (Hughes-Morton, Fritz-Mathis) thicker limes appear. In Tarrant County these consolidate to 347-418 feet of Glen Rose. Fig. 17. Subsurface profile of Trinity group from Fort Worth to Red River. The limestone facies (Glen Rose) fingers out northwards into the sand facies (Antlers). In the Red River counties the typical Comanchean well log shows the W oodbine distinct ( 400-536 feet), the combined W ashita and Goodland limestone 425-650 feet thick, and the Antlers 456-1185 feet thick. This variation corresponds to irregularities in the base· ment, and to local overlap of basal beds. Facies changes in the Trinity are shown on the outcrop in Parker &nd Wise counties (Cooperative maps Parker & Wise Cos.; Scott, ] 394) . About 4 miles west of Decatur a few thin limestone ledges with typical Glen Rose fossils occur. On the Weatherford-Millsap road the Glen Rose, in two limestone seams, is about 50 feet thick. Eastward and southward the Glen Rose thickens, partly by the addition of new limy members above and below. Along the Brazos valley at the Parker-Hood county line, the Glen Rose is about 200 feet thick. In central Travis County the Glen Rose is 359-418 feet thick. In Dallas it has a recorded thickness of 522 to 595 feet (1454, pi. XX). In Parker County, the basement sands and conglomerates, 150 feet thick or less, consist of quartz sand and pebbles up to 3 inches in diameter, well rounded in comparison with the underlying angular and heterogeneous Pennsylvanian conglomerates, and not derived from them. In both the basement sands and the Paluxy there are deep purple "red beds." The basement sands contain bone fragments, carbonized wood and plant remains, and much silicified logs and wood. The Paluxy is a packsand, bearing silicified wood. An east-west section, from Erath, Comanche, and Brown counties to beyond Big Spring, shows the Glen Rose rapidly thinning west· wards across Comanche County and disappearing near Brownwood, west of which only Paluxy represents the Trinity group (Fig. 16). At Round Mountain, northwestern Erath County, the Glen Rose is 1epresented only by a 5-foot limy ledge. In the Santa Anna, Calla­han Divide, and San Angelo area, the Paluxy consists of 150 feet or less of derived material, which rests on an irregularly eroded Pe1mian basement. In lrion County, thin Trinity lime is logged. Near Big Spring and in the Llano Estacado the substratum is Triassic. In the Colorado River valley, the lateral variation of the Trinity group has been studied by Taff, in a series of sections from Hickory Creek to M;ount Barker near Austin (1574). These studies demon­strated that the clastic and conglomeratic features of · the Trinity become more refined towards the southeast, and that the Glen Rose limestone thickens and becomes more calcareous and less sandy The Geology of Texas-Mesozoic Systems 309 in that direction. If Ta:ff's section were projected graphically west­ward, the limit of the Glen Rose limestone would lie in eastern Llano County. In the Hays-Blanco county section, the Glen Rose thins westwards and disappears in eastern Gillespie County. In the Kerrville-Fredericksburg section (Fig. 16) the same thin­ ning is shown on outcrop and in subsurface. The marginal facies of the upper Glen Rose near Fredericksburg has taken on a great quantity of red color from the underlying decomposed Cambrian formations. This facies is called the Gillespie formation. It bears cycads and fossil wood. In the southern part of the Edwards Plateau, numerous sections reveal the ofishore thickening of the Trinity group, and the fact that several areas were islands in Trinity times. This area has been investigated by Mr. L. D. Cartwright ( 20 lb) . The inner margin of the Trinity across the southern part of the Edwards Plateau, and sorne projecting irregularities in the old land floor (presumably islands) hoth within the limits of the Glen Rose limestone wedge and in the area of marginal sands are shown on Fig. 16. Liddle and Prettyman have published numerous sections of the Trinity in the Pecos valley (991). The basement rocks are irregular in this district, and locally no Trinity was deposited (Fig. 16). In the Marathon-Fort Stockton section, the Glen Rose outcrop occurs as far north as Gap Tank. To the west, in the northem Glass Mountains, the entire Trinity group is locally ahsent by non­deposition, and the Fredericksburg rests on the Paleozoic. In the Fort Stockton area, the Trinity limestone is of irregular distribution, generally absent on the highs. In several of the wells, sands, with Chara fruits are present, and are probably Trinity. Farther south­west, in the Hovey district, wells show severa} hundred feet of Glen Rose limestone. Kent is north of the margin of the Trinity limestone, and only thin Trinity sand is present at the outcrop. In the Sierra Blanca area north of the Texas and Pacific Railway, hcneath the Georgetown limestone is 100 feet or less of sandy beds with Kiamichi fossils. Under thcse is the Finlay limestone, which is of Edwards and Comanche Peak age. Beneath this is the Cox sandstone, probahly of Maxon-Paluxy age at its top, of Glen Rose marginal equivalents basally. The Campagrande and Etholen have not been precisely dated by fossils, but are likely of Trinity age. For Fredericksburg equivalents at Sierra Blanca, see page 352. From the Etholen, Baker records Porocystis pruniformis; in the sandstones near the base of the Etholen at the type locality, there are sorne poorly preserved oysters. Taff (1573, p. 724) records oysters and an Exogyra? in the Etholen conglomerate; Richardson does not mention any specifically Trinity fossils in the Cox or the Campagrande. TRAVIS PEAK FORMATION Nomenclature.-The Western, or Upper, Cross Timbers, under­lain in part by the Travis Peak formation, was known to certain early explorers and writers (1329, 1463), hut only in 1887, when studied at localities near Millsap, was it formally recognized by the name "Dinosaur sand" (731, pp. 301-302). The names "Trinity sand" and "Trinity division" were first applied by Hill in 1889 (735, p. 219), the type locality being in western Travis County. Stratigraphy and Contacts.-The Travis Peak formation rests on early Cretaceous beds in the Malone ancl Quitman mountains dis­tricts. In the Rio Grande embayment and in Louisiana its substratum is unknown. Elsewhere in Texas it rests unconformahly on a folded and eroded basement of pre-Paleozoic, Paleozoic, or Triassic forma­tions. In a few places within its extent, it is locally ahsent: in part of the Llano-Burnet area, in the lower Pecos valley, in the northern Marathon basin. In sorne Denton County wells it rests on Ellen­burger. lts upper contact has not heen well studied. In . north­central Texas, and generally, where the Glen Rose limestone is absent, no line can be drawn between it and higher Trinity sands. Scott states that its top is laterally continuous with outfingerings of Glen Rose. Data on the deep offshore zones of the Glen Rose (Louisiana, Chittim structure) have not been published, and it is not known whether they coincide with sorne zones referred to the Travis Peak in the marginal areas or not. Facies.-Nearshore, the formation consists of packsands, grits, sandy clays, sandstones, conglomerate, and gravel. Offshore, it consists of sandstones, sands, sandy clays, thin seams of limy rock, and at the base a variable thickness ( 50 feet or less} of grits and conglomerates with subangular quartz grains and rounded quartz pebbles up to an inch long. Most of this material is the marginal, in part littoral, deposit of an advancing sea; other more limy an,d shaly beds are a part of the neritic facies. The Geology of Texas-Mesozoic Systems 311 Areal outcrops, local sections. -In the Red River region the Antlers sand, the sandy equivalent of the entire Trinity group, con· sists predominantly of poorly cemented or uncemented packsand. At Rock Bluff ferry, northwestern Cooke County, the base of the Trinity consists of 16 feet of gravelly conglomerate of chert and quartz pebbles up to 3 inches in diameter, and fine to coarse, poorly cemented, light colored sand. This is followed by about 68 feet of packsand, containing at places limy streaks, irregular concretions, layers 9f yellow to purple clay, and, near the top, some thin layers of gypsum. This is capped by a 3-foot, hard, pebble, conglomerate bed. Between Warren's Bend and Sivell's Bend (Bullard, Okla. Geol. Surv., Bull. 33, p. 21, 1925), there is a section of 181 feet of upper Trinity overlain by Goodland limestone. It consists of packsands and hard sands (mostly of light colors), some sand­stone, and clay. In the upper part of the section, Exogyra texana Roemer and Ostrea crenulimargo Roémer, occur. On a tributary of Little Mineral Creek 4 miles north of Fink, 123 feet of Trinity is recorded (177, p. 17). It consists of light colored packsands with sorne clays, conglomerates, and limy streaks. The formation contains locally large amounts of fossilized logs and driftwood. Grayson County wells have almost a thousand feet of Antlers. In the city of Sherman well it is 953 feet thick and is largely packsands and sandstones, with some shale and sandy shale near the base. Red color is scattered throughout, except near the top. Water horizons are logged about 200 feet below the top, and at many levels near the bottom. In Montague County (176, p. 69) the basement sand of the Trinity is about 600 feet of clean packsand and conglomerates with scams of clay. The fine, white to yellow, massive packsand occurs in beds up to 40 feet thick. Lentils, of yellow, purple, or yaricolored clays, scattered throughout the Trinity, have a thickness ranging from a few inches to 40 feet. The basal Trinity consists of a quartzose conglomerate, about 3 feet thick, composed of well rounded quartz grains and pebbles up to an inch in diameter, with practically no mud or silt in the matrix. Near Montague and Bowie there are more than one of these thin basal conglomerate seams. In Wise and. Parker counties, the basement sands and conglom­era tes reach 150 feet in thickness. The basal conglomerate consists of quartz sand and pebbles up to 3 inches in diameter, with little siliceous or calcareous cement, or, more generall y, uncemented. These rounded quartz gravels are not derived from the underlying angular and heterogeneous Pennsylvanian conglomerates. The basal conglomerate grades upwards into unconsolidated white pack­sands, and thence into the sandy clays, and limestones of the Glen Rose. Locally the basal Trinity, like the Paluxy, contains red beds. Near the village of Brock there is a local concentration of salty sand which contaminates wells and makes the soil unusable (1~94, p. 39). Along the strike in Cooke, Denton, and Tarrant counties, the base­ment sand maintains a thickness of around 400 feet (Fig. 17), but down-dip it thickens somewhat (550 feet at Dallas, severa! hundred feet south of Mexia). From the Brazos River valley to the Colorado River valley, the western border of the Comanchean lies only slightly west of the farthest extent of the thinned Glen Rose lime· stone. Therefore to the west of this border the outliers of the Trinity group consist only of sandy deposits overlain by Fredericksburg clay and limestone, as at Santa Anna and in the Callahan Divide. From the Brazos Valley the Trinity border passes in a southwesterly direction across northern Erath and Comanche counties to the northern part of Brown County. Thence the margin follows south­wards along high blu:ffs on the east side of Pecari Bayou to · the Colorado River valley near Marble Falls ( 449, pp. 360-371). The basal Comanchean conglomerate and sands show two outstanding features: (1) they were deposited on an irregular Paleozoic floor, and change rapidly in thickness; (2) the basal conglomerate con­sists largely of materials deriyed from the immediate vicinity, and is more limy in the south (Burnet, San Saba, McCulloch counties) where the hard Ellenburger and Bend limestones furnished resistant materials, more sandy in the north (Brown, Eastland, Comanche counties) where the Paleozoics contained more soft sandstones, clays, arid sorne limestones. From Comanche County, at Round Mountain, Hill (803, p. 207) gives a section of about 247 feet oí sand, sandy shale, and thin conglomerate below the Glen Rose limestone. Along Rusk Creek north of Comanche the 50 to 75 feet of basal Comanchean is composed largely of a conglomerate of siliceous pebbles and grit of white ( occasionally red) quartz grains ( 449, p. 364). At nearby localities the conglomerates in the basal MAP SHOWING OUTCROP OF TRINITY DIVI SION BETWEEN THE BRAZOS & RED RIVERs;rEXAS LE. GEN O t ~wa1m,1t "j{ [§] 'º"'' ~ } ~ ¡ Gl~nrose Antlers ~~;i:~ent Sands Fig. 18. Outcrop of Trinity group between Red River and Brazos River, showing interfingering into sand of the thin, interior margin of the Glen Rose limestone wedge (Dr. Gayle Scott). Trinity sands and grits are very thin and local. In the escarpment east of Pecan Bayou, on account of the irregularity of the Paleozoic fioor, there is a variable amount of basal conglomerate, 20 to 30 · feet, overlain by red, pink, or yellow friable sandstone and grit, and by sandy limestone, . followed by sands and sandy clays to a total thickness of 100 feet or more. N~ar Nix, Lampasas County (449, p. 364; 803, p. 181), the basal conglomerate, 20 feet thick, contains pehhles of Paleozoic limestones, quartz, fiint, and other materials, cemented in a matrix of argillaceous and arenaceous lime. It is followed by 30 feet of lime-cemented packsand and grit, then 20 feet of calcareous sand· stone. Locally north of this point the basal conglomerate reaches 100 feet in thickness and is followed by as much as 100 feet of packsand. Colora.do River section.-Near the type locality, Travis Peak, basal sands are over 250 feet thick, and thin westwards. The basal conglomerates and sands have here heen called the Sycamore sands by Taff. They typically consist of ahout 50 feet of basal con­glomerate followed by cross-hedded calcareous shell grit. They ccntain the basal Trinity artesian water reservoirs in this immediate area. They are followed by the relatively impervious Cow Creek beds, ahout 30 feet of shale, grit, sand, and shell heds. Ahove these are the Hensell sands, typically 143 feet of red and yellow sand, C'onglomerate, and sorne limestone. This memher contains the important middle Trinity aquifers. It is followed by yellow sandy fossiliferous (rudistid) basal Glen Rose limestone. The Leon sands in Comanche represent the local hasement sands level. The Gillespie sands near Frederickshurg represent the entire local basal sands helow the upper Glen Rose limestone, hut may also he of Glen Ro.se age. Shorewards from Austin the Glen Rose thins rapidly, and the Trinity group is reduced to a thickness of 70 feet at Post Moun­tain, just south of Burnet. The Travis Peak formation, originally studied hy Taff (1574), was partitioned into three memhers by Hill (803, pp. 141-144). The Geology of Texas-Mesozoic Systems 315 HICKORY CREEK SECTIO OF TRAVIS PEAK FORMATION Feet D. Thin-bedded sandy limestone, with sorne limy sandstone and conglom· era te seams --··--····---···--··-·······--····--····-·····-·-·-·-···-···-·---··-40 C. Hensell sand member.-Red or yellow sands, with subsidiary beds of conglomera te, sandy limestone, and magnesian limestone; few fossils; artesian water horizon -·-·--·-·-·-··--···-·-·-····-···-···-·····-··--··--143 B. Cow Creek member.-Grit or conglomerate, much of it calcareous, more limy near top, with many fossils at sorne levels; subordina te bluish shale, sands, and sandy limestones; forros prominent calcare· ous, fossiliferous bencL...-····-················--··············-·············-····-········ 30 A. Sycamore2 9 sand member.-Conglomerate, sand, silt and shell grit; basally with cobbles up to 6 inches diameter; above, the pebbles decrease in size; near top, cross-bedded limy shell grit; downdip forros artesian water horizon; westwards it seems to disappear.___ 50 (Unconformably underlying rocks : Strawn or Smithwick.) Cuyler (Thesis MS., 1931) reports three levels at which fossils occur: two in the Cow Creek member, and one near the top of the Hensell. A large fauna occurs in the Cow Creek beds, including Du/rerwya texana (Hill), D. justinae (Hill), D. roemeri, Pseudosaynella walcotti (Hill), Ostrea rags­dalei Hill, Trigonia stolleyi Hill (Hill, 755, p. 47; 783; 803, p. 161, pl XXI; Cragin, 324). GLEN ROSJq FORMATION"" Nomenclature.-This formation, the Caprotina limestone of Shumard (1463, pp. 583, 588), was first named Glen Rose by Hill (772, pp. 504-507) in 1891. The type locality is in the thinned shoreward extension of the formation along the Paluxy River near Glen Rose, Somervell County. Stratigraphic position and contacts.-Basally, it is in gradational contact with the Travis Peak sands. It is absent west and north of the line shown in Fig. 16. North of about the latitude of Waco, it is overlain, probably in gradational contact, by the Paluxy sands, which Scott claims to he littoral deposition in a withdrawing sea at the end of Trinity time. Hill had previously indicated that the Paluxy is a sandy phase of the upper Glen Rose limestone. Facies.-The Glen Rose is a calcareous formation, in part clayey and sandy, and is of the neritic facies. As already explained, it is »rhia na.me hae priority over the Sycamore limestone in Oklahoma (J. A. Taff, 1903) . IOLJierature.-Hill, 742, 753, 762, 767, 780, 783, 795, 803, 827 ; Rauff, 1286; Scott, 1394; Uddea, 1623 ; Vanderpool, 1678, 1679, 168la ; COOperative maps, Parker and Wise counties, 1853. replaced shorewards by sand. Numerous features, ripple marks, dínosaur tracks, plants, gypsum, and general líthology, indicate that at many places it was deposited in shallow water. Areal outcrop, local sections.-The Dierks and De Queen lime­stone lentils in southwestern Arkansas contain Ostrea franklini, Anomia texana, Modiola branneri, Eriphyla pikensis, Glauconia branneri and other Trinity fossils. Outfingerings of similar lime­stone outcrop in western Parker County, Texas, where the marginal Glen Rose contains three zones (1394, p. 41) : (1) near the base, a zone characterized by Orbitolina texana (Roemer), Porocystis globularis (Giebel), Pecten stantoni Hill and Trigonia stolleyi Hill; (2) near the middle of the formation, a zone of abundant Orbitolina texana, and sorne Loriolia texana (Clark); and at the top, a mass of Modiola branneri and sorne Porocystis n. sp. (elongated). Just above the second zone is a Monopleura-Toucasia bank. In this sec­tion ¡it least three lhny outfingerings of the Glen Rose into the Paluxy facies are mappable. A similar situation is seen on sub­surface profiles in Denton County, where several such limy out-fingerings occúr (Fig. 17). . . The Glen Rose typically consists of thin-to medium-bedded hard continuous limestone strata alternating with marl or marly lime­stone, and weathering in stream cuts to steep canyons and on .hill­sides _to a terraced o.r "staircase" topography. J'he narrow Glen Rose prairie passes from Mt. Bonnell northwest of Austin to near Burnet, and thence northwards to west of .Lampasas, up the large. scarp east of Pecan Bayou in Mills and eastern Brown County to near May, thence northeastwards to make a large southeast reentrant down Leon River in northern Comanche County, thence northwards to near Desdemona, and northeastward to the Brazos in southwestern Parker County. lts last limy outfingerings occur near Decatur and elsewhere in Wis~ County. In its outcrop south of the Brazos, it grad­ually increases in thickness to about 720-:800 feet near Waco. In Bell County, the 500-664·feet of Glen Rose consists of pure, so lid lime­stone near the middle, thinner bedded, shalier, and sandier lime­stones near the base and the top, and two general water horizons, located respectively 130-175 and 240 feet below the top. In the Faleozoic inlier at Lampasas (1574, pp. 32~-338), following about 20 feet of basal heterogeneous conglomerate and 30 feet of yellow­ish, brown, and whitish packsand, sandstone, and grit, there is about The Geology of Texas-Mesozoic Systems 317 80-feet of Glen Rose limestone, sandy and transitional in lithology at the base, and more calcareous above. lt consists of soft, impure limestone, alternating with marly lime and soft yellow sandstone, the strata being thin-bedded and well stratified. From Twin Sisters Peak, to Bachelor Peak 18 miles to the southeast, it has increased in thickness from 90 to 200 feet. The McAngus well near Elroy, eastern Travis County had in excess of 1066 feet of Glen Rose ( 1854-2920) , and more than 180 feet of Travis Peak (2920-3100 T.D.). The city of Austin Blunn Creek well in Travis Heights had 800+ feet of Glen Rose (825?­1632), and 558 feet of Travis Peak (1632-2190). Celestite occurs in pockets at a level near the top of the Glen Rose at man y places in central Texas: on Donaldson Creek due east of Nix, in the escarpment north of Nix, in Rocky and South Rocky creeks near Lampasas, South San Gabriel River north of l.eander, Mount Bonnell north of Austin, and elsewhere. Anhydrite is recorded in Comanche, Lampasas, and western Parker counties (803, p. 146). In the Hubbard city well, Hill County, a 30-foot layer of anhydrite occurs near the depth of 2855 feet. Anhydrite occurs in the Glen Rose in Arkansas, Louisiana, and Maverick County, Texas. West of Austin the Glen Rose shows the same gulfward thicken­ing and change of facies. At Fredericksburg (795, pp. 221, 314) it is about 55 feet thick, and at Kerrville about 600 feet thick. A similar change southwards occurs across Sutton, Edwards, and Kinney counties. For Glen Rose in Trans-Pecos Texas see pages 292-297. Paleontology.-In the central Texas outcrop counties, where it has been most studied, the Glen Rose is from 400 to 800 feet thick, but underground in the Gulf Coastal Plain, it exceeds 3500 feet. Its fossil zonation is nowhere known, and it is probable that the reduced outcrop thickness represents only the upper portion of the complete formation. If so, all existing fossil partitions are very defective. Pending fuller study of thick subsurface sections, such as those in Maverick County and Louisiana, or thick outcrop sec­tions, such as those in northern Mexico and the southern Quitmans, no general zonation for the formation can be outlined. The Quitman section contains, associated with or slightly above Malone fossils, a prominent zone of Exogyra quitmanensis Cragin. This, or a similar oyster, occurs at the base of the section in the rim and in Glen Rose inliers in the Solitario. Associated fossils are Trigonia, a large Pecten n. sp., Alectryonia aff. carinata and echinoids like Toxaster. Severa! hundred feet above this are the main Orbitolina texana zones. The succession of zones in the Quit­mans and the Solitario is as follows: Exogyra texana (abundant) ______ WaJnut Orbitolina texana, and Glen Rose echinoids ____________Glen Rose, Bluff bed Douvilleiceras, Parahoplites a n d other arnmonites ____ ____Basal Glen Rose Exogyra quitmanensis _ _ ____Quitman bed; Cuchillo Trigonia taffi _____ _ Basal Quitman; Cuchillo Fossils unknown _ __Mountain bed; Las Vigas Malone fossils ________Torcer In central Texas, several zones of Orbitolina texana and other allied foraminifera have long heen known; sorne ammonites (Douvilleiceras, Parahoplües and Dufrenoya) occur hut have not heen worked out; anda large smooth Exogyra resemhling that from the Solitario occurs. A Douvilleiceras n. sp., with depressed cross·section and reduced tuhercles, was hlown out of Dixie Dillon No. 43 well, Pine Island, Louisiana, from helow the casing, at 3338 feet. It is from the lower Glen Rose limestone, ahove the 2000 feet · of red shale. Vanderpool (1678, 1679) lists the following ostracoda from the Trinity group in southern Arkansas, northwest Louisiana, and near Weatherford, Texas: Ba.irdia dorsoventrus anderpool Cypridea sp. indet. Bairdia glenrosensis \ anderpool Cytheridea trinitensis Vanderpool Bythocypris rotundus anderpool Cythere ornata Vanderpool Cypridea diminutus anderpool Paracypris weatherfordensis Vander­Cypridea tuberculata Sowerby var. pool gypsumensis anderpool Pontocypris perforata Vanderpool Cypridea ventrosa Jones var. bispino­sus anderpool Algal ( Chara) oogonia occur in man y widely separated areas in 1he Trinity group in the Southwest. They have heen reported from the De Queen limestone memher of the Glen Rose in Arkansas (1678, p. 98), from the Glen Rose in northern Texas (1791, p. 64), from the Glen Rose in the Kokernot well near Hovey ( 633) , and The Geology of Texas-Mesozoic Systems 319 from strata referred to the Trinity in various wells in the Fort Stock­ton district (12, pp. 33-37). Chara oogonia appear to be moré prevalent on the southern . edge of the Salt basin and along the Fort Stockton-Yates high area. They occur in the Penn Alvis well about 2 miles south of Belding; the Lockhart Webb well west of Fort Stockton; in various wells along the southern flank of the Fort Stockton high;_ crest of Yates Pool; Riley Murphy well, west of Sheffield; Cosden Perner well, Crockett County; and well in central Irion County. Sorne Chara are found in a greenish-gray shale with limestone · concretions, gypsum and ostracoda, which underlies the "Basement sand" (Maxon, Paluxy?). These basal shales are 100 or more feet thick near Fort Stockton, about 250 feet thick at Y ates, and near 600 feet thisk at Belding. Wieland (l758a, 1759, l 759a) records the following Trinity cycads: Cycadeoidea boeseana Wieland (Basal Trinity sand; near Bridgeport) Cycadeoidea barti Wieland ( Paluxy, near Comanche; Gillespie sand, near Fredericksburg) Cycadeoidea wolfei Wieland (Paluxy, near Stephenville) Cycadeoidea dyeri Wieland (Paluxy; near Tolar and Stephenville) Cycadeoidea johnstoni Wieland (Paluxy, near Stephenville) Wieland says: "Tbe Trinity beds must be ranked as one of the five great cycad-yielding terranes of North America-the other four being the Arundel of Maryland, the Lakota of the Black Hills region, the Como of the Black and Freeze Out Hills, and the Mesaverde of the Chuska Mountain region of New Mexico and Arizona . . . The Trinity was a flat, subsident, river and bayou, cycad-dinosaur-conifer, forest land, swept by the shallow edges of the sea." Jones (888, p. 770) says: "Tbe writer has seen nodules of pure coal im­bedded in the Glenrose limestones of Bandera County, Texas." The foraminifera from the Glen Rose have not been carefully studied, but probably Orbitolina-like forms of two or more genera exist. The corals show a great variety, sorne being reef-forming. Forty or more species have been collected and are being described _by Mr. J. W. Wells (1727). The mollusca in the outcrop counties show a great variety; only a few have been described by Hill, Conrad, and others. The alleged bryozoon genus Porocystis marks the Glen Rose. Echinoids are abundant and as yet undescribed. The most distinctive Glen Rose fotaminiferal genus is Orbitolina, of which a common species, O. texana, was described by F. Roemer in 1849. The genus has been recently reviewed by Vaughan (1688a). He considers the larger O. whitneyi Carsey to be only a large·sized variant of O. texana, and O. texana asaguana Hodson and O. texana monagasa Hodson (from Venezuela) to be only growth forms of O. texana. He says (1688a, p. 610): "O. walnut­ensis Carsey [from the Fredericksburg group] differs so greatly from the other species that it may belong to another genus"; Silvestri (1479a) has referred it to Dictyoconus. Glen Rose corals (Wells, 1727, 1727a) occur largely in reefs, located in the lower half of the formation, and built on great masses or layers of caprinids. The lowest reef, at the base of the Glen Rose in Hays, Coma!, and Blanco counties, has afforded 6 species of lsastrea, Orbicella, Astrocoenia, and other genera, and has a height of 3 to 10 feet over an area of severa] square miles. Reefs located about 100 feet above the basal reefs are 15 to 30 feet thick, and contain numerous types of corals, some brachiopods, oysters, and other fossils. A third coral horizon occurs about 200 feet above the base of the Glen Rose. Dinosaurs, mostly tracks, are known from the following locali­ties: Kinney County near northeast comer on the Edwards ranch; northeastem Uvalde County near Utopía on the Loman ranch; southeast comer of Kimble County on the Gamer ranch, about 7 miles west of Kerrville and 13 miles north of the Kerrville-Junction road; southem Bandera County, in Hondo Creek 2 miles down· stream, and 21/z to 3 miles upstream, from Tarpley; Medina County, Hondo Creek, about 13 miles northwest of Hondo; Travis County (reported), about 15 miles up Colorado River from Austin; near Glen Rose, Somervell County (1452); in Hamilton County (1805). Bones, said to be of a Morrison dinosaur Elaps, were found by Darton (N. H. Darton, oral communication) in the Middle Concho River in eastem lrion County, probably in Paluxy sand. Wieland (l759a) records a nearly complete dinosaur skeleton from the Pal­uxy?, on Paluxy River near Stephenville. Gould (626) records a dinosaur from the .A.ntlers sand in southern Oklahoma. Plants have been described ( 545) from the Glen Rose near the type locality. PALUXY FORMATION The upper Trinity sand was first given the name Paluxy by Hill (780, p. 84; 772, p. 510) in 1891. That it is laterally continuous with the upper Glen Rose was maintained by earlier writers, and can be observed at sorne places. Fossils hitherto found in the Paluxy do not give clear-cut age indications. Ostrea crenulimargo and Exogyra texana, recorded from the upper Antlers in the Red The Geology of Texas-Mesozoic Systems 321 River region, are Fredericksburg or Trinity forms, and may indicate that the upper Antlers is of Fredericksburg age. Fossil wood and fish remains (318) are of unknown value for age determination. -Cycads (Cycadeoidea barti Wieland, 1759a) occur a few miles north of Comanche, and there are notable cycad localities near Stephenville. Paluxy sand outcrops in a narrow timbered strip on top of the Glen Rose prairie, from the Antlers sand in the Red River region in Montague and western Cooke counties southward to the Leon Valley at the north boundary of Coryell County (latitude 31° 30'). McLennan County logs give no definite indication of Paluxy. Farther south it is absent both on outcrop and underground. Its exact subsurface extent has not been traced. A thin (about 20 feet) but persistent sand occurs at its leve! in man y Hill County wells: in the Milford City well there is 30 feet of sand, hard above but -containing good water basally; in the Wetherby well east of Hills­ boro, 20 feet (at 1160-1180) of water sand occurs; in the R. C. Finley well in southern Hill County this is reduced to 11 feet ( at 596-607 feet) . A noteworthy feature of the Paluxy is its extension westward over the Callahan divide. There is no doubt that the thin basal Cre· taceous sand in this area is continuous with that above the western­most outfingerings of the Glen Rose limestone (Fig. 18). At Santa Anna ( 449, pp. 11, 13, 14), the basal sand is 105 feet thick and is used for glass manufacture; at Bu:ffalo Gap, Taylor County, it is 140 feet thick (1574, p. 321); at Signa! Peak, Howard County, 70 feet thick (841, p. 76); at Double Mountain, Stonewall County, 25 feet thick ( 467} . W est of the Pecos, the Maxon and Cox sandstones are in part equivalent to the Paluxy. Lenticular sands occur in the Colorado River drainage at the top <>Í the Glen Rose, in the proper position for the Paluxy, and support the idea that the Paluxy is a sandy facies of the uppermost Glen Rose (see 803, p. 169). Such an area of sand occurs from 3 to 51h miles south of Bertram, Burnet County, where it is about 20 feet thick, and consists of packsand with thin arenaceous limestone seams, capped by thin W alnut limestone and marl containing Exo­gyra texana. Another area of Paluxy is in and east of Bachelor Peak along the road between Briggs and Lampasas, where the sand is 10 to 15 feet thick. GILLESPIE FORMATION Hill and Vaughan ( 795, p. 221), in 1898, called the basal Comanchean sands at and near Fredericksburg the Gillespie forma­tion. The formation consists of about · 120 feet of cross-bedded, vermilion-red sands, silts, clays, and sandy grits, lying beneath the thin (55 feet) Glen Rose sandy limestone. They were con­sidered to be probably the stratigraphic equivalent of the lower part of the Glen Rose formation. Two miles south of Fredericksburg on the Adolf Eckhardt land they contain cycads ( Cycadeoidea barti Wieland) and fossil wood. Near Kerrville a considerable thickness of red material may represent the downward extension of this forma­tion. The red color is derived from the underlying early Paleozoic heds; the formation is strictly a local facies, characterized by its lithology. FREDERICKSBURG GROUPs1 N omenclature.-Roemer classified these rocks, including those at the type locality, Fredericksburg, in his "Kreide des Hochlandes," as Turonian or Senonian, overlying the Upper Cretaceous rocks of the Gulf Coastal Plain. Shumard, repeating Roemer's error in the Austin section, placed his Comanche Peak group and the overlying Caprina (= Edwards) limestone above the Austin chalk (1463, p. 583). In Hill's first classification (731, p. 298) the Fredericks­burg division included rocks down to the Dinosaur sand {Travis Peak), but later, his Trinity division (772, pp. 504-511) was made lv include the basal Trinity sands and the Glen Rose, the Paluxy being placed questionably as basal Fredericksburg. The town Fredericksburg is the nominal type locality, unfortunately chosen, as the group is unequally developed over Texas, its basal part (W alnut and Comanche Peak) being most fully shown in the Brazos and Bosque valleys, and its upper part (Edwards) most typically developed in the canyons of the Nueces, the Pecos, and the Rio 81.Literature. -A..rkansas: Dan e, 392. Oklahoma: Honess, 840; Bullard, 174; Hill, 788. Northeast Texas: Lahee, 969; Shumard, 1463. Coastal Plain.: Collingwood, 267; Brucke, 164, 165; Hill and Vaughan, 808; Hill, 803; Taff, 1574, 1575; McCollum, 1076. Edwards Plateau: Hlll and Vaughan, 794, 795; Hil11 825. Rio Grande Embayment: Getzendaner, 578, 578a; Vander• pool, 1681; Udden, 1625. Trans·Pec.os Texas : Hill, 799, 805, 820; King, 936; Adkina, 12; Baker, 46; Richardeon, 1304; Udden, 1623, 1626, 1664; Wilson, 1787. Lithologr: Adkins and Arick, 16; Alexander, 27; Hanna, 647a; Udden, 1656. Paleontology: Alexander, 27, 29, 30; Adkins and Winton, 9; Cragin, 324; Clark, 253; Hill, 784, 803; Lasswitz, 976; Marcou, 1041; Merrill, 1103; Plummer,, 1238 ; Stanton, 1522, 1522a; Winton, 1789, 1791. Kiamichi: Adk.ins. 12, 16; Bullard, 175; Scott, 1398a; Stanton, 1524; Taff, 1574, 1575; Winton, 1789. The Geology of Texas-Mesozoic Systems 323 Grande. At a later date, disagreement arose concerning the proper cJassification of the Kiamichi clay, whether basal W ashita or upper Fredericksburg; it is here included in the Fredericksburg (page 360). Although in this discussion the Fredericksburg is · divided into the usual con­ventional formations, it is the writer's opinion that all formations in this group should be suppressed and only the facies used. However, a decision on this procedure can be reached only after the zonation is better known and the meaning of the term "formation" better clarified. Strat,igraphic position and contacts.-North of Coryell County, where the Paluxy is present, Scott claims an unconformity at the hase of the Frederickshurg, hecause the Paluxy was deposited in a regressive sea, which readvanced over the land, depositing the Walnut formation. In south and west Texas the Glen Rose-Walnut contact is apparently concordant (page 328). The Kiamichi is ahsent south of Bell County, and its position is marked by a dis­conformity. In north-central Texas there is sorne evidence (pehhles) for an unconformity at the top of the Kiamichi; over parts of Oklahoma and Kansas, Kiamichi is the last remaining marine deposition. Facies.-The Frederickshurg group presents a complex assortment of facies, corresponding to various conditions of deposition. (1) Marginal facies: consists of sand, sandstone, and sandy shale; perhaps the upper part of the Antlers sand in the Red River counties of Texas and in southern Oklahoma is of Frederickshurg age; at Black Mountain (Sierra Prieta), north of Sierra Blanca, sandstone of the marginal facies, containing casts of Alectryonia cf. carinata and other pelecypods, has invaded the section as high as the hase of the Desmoceras-Hamites zone of the lower Duck Creek limestone. (2) Neritic facies: the widespread marls, marly limestones, and chalky limestones in the Walnut, Comanche Peak, and Kiamichi formations. (3) Reef facies : coquina, shell dehris, detrital and shelly limestone, and organic limestone of several types. In contrast to No. 2, it contains rudistids, hut few ammonites; other common fossils are corals, echinoids, bryozoa, pelecypods, gastropods, worms, fish remains, and algae. There may be marly interbeds between cr around the reefs. Typical Edwards reefs are found near Belton, Crawford, Ogleshy, and Round Rock. Among the most famous ones is the El Abra limestone, largely organic-reef limestone with Chondrodonta and Eoradiolites, in the Sierra del Abra west of Tampico, and in the buried mountain range now the producing horizon in the southern Vera Cruz oil fields ("Golden Lane"). From wells in this field many caprinids, rudistids, Pectens, and other fossils of the reef type have been blown out under high gas pres­sure. The rocks are mostly of Fredericksburg age. (4) Oyster aggregates, as in the Walnut and Kiamichi. (5) A non-marine, but near shore, plant-bearing sandstone facies of Fredericksburg age is represented by the Cheyenne sandstone in southern Kansas (1621; Berry, U. S. Geol. Surv., Prof. Paper, 129-I, 1922). (6) In the Rycade Chittim No. 2 well in eastern Maverick County, 20 feet of coarsely crystalline rock salt occurs near the top of the Edwards (578, p. 1426). Areal outcrop, local sections.-In the Red River valley, the thinned Goodland-Kiamichi produces only a narrow band of out­crop. Southwards the formations thicken, and the outcrop forms a part of the Grand Prairie, lying east of the Western Cross Timbers (Trinity) and west of the Washita prairies. In central Texas, the dissected western border of the outcrop forms the Lampasas Cut Plain, whose top consists of interstream ridges and outliers of limestone (Edwards and Comanche Peak), overlooking to the west clay valleys (Walnut). Rocks of this group form the crest of the Callahan divide, the remnant of the formerly continuous plateau which covered the denuded area in north Texas between the main Comanchean outcrop and the Llano Estacado. Fredericksburg forms the resistant cap of the Llano Estacado as far north as 33º north latitude. It forms the cap of most of the Edwards Plateau. In western Texas the limestone plateaus have been rejuvenated, and the rivers have cut deep canyons in Fredericksburg limestones (Nueces, Pecos, Devils River, Rio Grande). The easternmost outcrop of the group is near Cerrogordo, Arkansas. It is reached in wells on salt domes in East Texas. Over a large area in northern . Louisiana the Fredericksburg and Washita sediments were uplifted and planed off the higher struc­tures in pre-W oodbine time. Thickness and dip.-On the Edwards Plateau, the dip is gentle .to the south and east. South and east of the Balcones fault, the dip steepens, and the beds of this group are buried deeply beneath later sedim~nts. The probable shore lines are indicated on Fig. 13. The Geology of Texas-Mesozoic Systems 325 Fig. 19. Profile of Fredericksburg group from Fort Worth to Austin. The two right hand columns should show a sniall thickness of "Comanche Peak" and of "Walnut" at the bottom of the section. ldentifiahle Frederickshurg is thin from eastern New Mexico to the Balcones fault, and in north-central Texas. Eastward, to the flank of the Sahine uplift, it thickens greatly, hut it particularly thickens on passing southward to the Rio Grande emhayment and northern Mexico. Over this area the Edwards (rudistid-reef) facies greatly thickens, and occupies the whole Frederickshurg column, extending even to the top of the Georgetown. This comhined limestone mass, the Devils River limestone of Udden (1625), Mountain limestone of Hill (782, p. 309), Aurora of Burrows (Bol. Soc. G. Mexico, 7 :85, 1910), reaches a thickness of 1500 feet west of Presidio. Paleontology anil zonation.-Some results have heen reached in constructing a douhle zonation for the Frederickshurg, one for the ammonite facies, and one for the rudistid facies. Much work, however, remains to he done. The type Walnut seems to he char­aclerized by forros related to Metengonoceras hilli, and sorne species of Oxytropidoceras. Oxy. chihuahuaense and O. acutocarinatum seem to mark the middle of the group. The top is marked by Dipoloceras a:fi. cristatum, Oxy. supani, Chonilrodonta munsoni and others. The upper Edwards is marked by severa! species of Eoradio­lites ( davidsoni, quadratus, angustus} and by Praeradiolites, gen. aff. Polyconites, caprinids like Planocaprina, and others. The Kiamichi is marked by Oxytropidoceras belknapi (Shumard), Oxy. several other species, Gryphaea navia Hall, Gryphaea tucumcari Marcou (also in basal Duck Creek), and others. At the Kiamichi· Duck Creek boundary, a restricted zone of Elobiceras occurs. The most distinctive or zonal Fredericksburg fossils are as fol­lows: among ammonites, Oxytropidoceras and Dipoloceras, so far as known, are restricted to the Fredericksburg group; radiolites occur fo it ( and the W ashita) but have never been reported from the Trinity group; certain types of reef , molluscs, as Chondrodonta munsoni, Pecten duplicicosta, Cladophyllia, and numerous minute fossils described by Roemer are unknown in the Trinity, occur in the Fredericksburg, and similar species occur in the reef facies of various Washita ages. The oyster Gryphaea is abundant at many Fredericksburg levels, but rare in the Trinity. Exogyra texana is present but rare in the Glen Rose. Many gastropods and pelecypods, occurring commonly as casts, cause confusion between Trinity and Fredericksburg, though many others are quite distinctive for each group. Common echinoid genera, are, so far, very confusing and undiagnostic, and data on those of the Trinity are still unpublished. Certain foraminifera are generally used in diagnosis: Orbitolina texana for the Trinity, Orbitolina walnutensis82 for lower Fredericks­burg, abundant large miliolids for the Edwards, an aggregation of arenaceous genera for the Grayson. Many fossils, alleged to be markers for certain formations, are quite unreliable, except perhaps locally and where found in abundance; among those whose currently quoted ranges need correction are: Haplostiche texana (Conrad), Kingena wacoensis, Alectryonia carinata, Nautilus texanus, "Enal­laster" texanus, Exogyra texana, Gryphaea marcoui, and several üthers which are habituallly misidentified. Until the thickened extensions of the Edwards in the Coastal Plain and the Rio Grande embayment have been studied, only provisional zonations of the group can be presented. A double zonation will be necessary, al;! in the Urgonian in the Mediterranean rcgion, one set of ammonite zones, and a set of rudistid zones. 32Referred to Dictyoconus aegyptensis Chapman var. Jl7alnu.ten.sis, by Silveatri, 147?a, p. 159, Cootnote l. · The Geology of Texas-Mesozoic Systems 327 PROVISIONAL FREDERICKSBURG FOSSIL ZONES Ammonite Facies: Rudistid Facies: Brazos-Colorado Pecos-Brazos­Pecos­valleys Rio Grande Colorado Rio Grande Kiamichi: Elobiceras Adkinsitesªª belknapi­Gryphaea navia (absent) (unknown) (absent) Edwards: Oxytropidoceras supani ? Eoradiolites zone ? Dipoloceras aff. cristatum ? Planocaprina? zone ? Dipoloceras aff. cornutum ? Comanche Peak: Üxytropidoceras acutocari­natum ? (Rudistid zones Walnut: unknown in basal Metengonoceras aff. hilli Fredericksburg) Correlation and age.-The upper Aptian (Gargasian) has been located by several writers as the Dufrenoya zone of the Travis Peak sands. Much of the Glen Rose and ali of the Fredericksburg is placed in the lower and middle Albian. The top of the ranges of the ammonite genera Dipoloceras and Oxytropüloceras, and the bottom of the ranges of Elobiceras and Pervinquieria, mark the base of the upper Albian, and approximately coincide with the Kiamichi-Duck Creek boundary. The other fossils mostly agree with the assignment of the Fredericksburg group to the middle Albian. Economic products.-Certain Edwards levels produce, locally, artesian water. The large springs along the Balcones fault make their exit through Fredericksburg rocks, but much of the water may be from Trinity aquifers. The Edwards is an oil reservoir at Luling, Larremore, Darst Creek and Salt Flat. Other economic products are limestone, lime, clay, grave!, quicksilver, silver, and severa! other metals in smaller amounts. It is not certain whether or not the upper part of the basal sands (containing Exogyra texana, E. weatherfordensis) near Fort Stock­ton, and the upper part of the Cox sandstone near Sierra Blanca are Fredericksburg. llGenuo deocribed by L. F. Spath, lSlla, p . 350. Teno species: belknapi {genotype), trinitensi.r (Gabb), chilwahuemis (Base), kiOUJana (Twenbofel) . FREDERICKSBURG FORMATIONS AND FACIES IN TEXAS North-central So u th-cen tral Sierra Texas Texas Fort Stockton Blanca Post-Kiamichi and Kiamichi Kiamichi Edwards Kiamichi Goodland { Edwards (thin) Comanche Peak University Mesa Comanche Peak (thin) Mar! } Finlay Walnut Walnut (thin) Comanche Peak ? Basal Sands ?Cox SS. ( upper part) (upper part) WALNUT FORMATION Nomenclature.-The Walnut clays were named by Hill (772, p. 512; 780, p. 86) to indicate the yellow clays, flaggy limestones, and shell masses of Exogyra texana and Gryphaea marcoui, lying above the Paluxy sands near Comanche Peak. The type locality is at W alnut Springs, Bosque County. Stratigraphic position and contacts.-In north-central Texas the basal part of the type Walnut is invade<¡! by sand, up to the level of the prominent Gryphaea marcoui shell aggregate, and the basal portion is thus indistinguishable from Paluxy sand. It is therefore probable that, north of Fort Worth, sorne Walnut sand may be included in the Antlers formation; at least the upper Antlers con­tains Exogyra texana and Ostrea crenulimargo, which are known from the Fredericksburg group. The W alnut-Comanche Peak con­tact is apparently conformable. In the southern part of the Edwards Platean and in northern Trans-Pecos Texas, the Walnut is either reduced locally to an insignificant "break" (receding ledge) less than 1 foot thick, or else is not positively identifiable. In the southern Pecos Valley, the underlying formation is Glen Rose lime­ stone, but near Fort Stockton it is the basement sand. These contacts appear to be concordant, but whether they are conformable has not been discovered. Facies.~The for~ation is in the neritic facies over most of its extent, and consists of clays, limestone seams and shell aggregates. From Fort Worth to the Red River valley its basal part is sand; this is possibly true at places in Trans-Pecos Texas, as at Ken!. Areal outcrop, local sections.-The section near the type locality represents only an extreme of the Walnut formation in Texas. To th€.. north the base rapidly becomes sandy, and the only persistent feature is the aggregate of Gryphaea marcoui shells; to the south Tke Geology of Texas-Mesozoic Systems 329 the oyster shell beds first became unconsolidated (in Williamson County) , and then vanish, leaving only an insignificant and indis­tinctive marl, containing scattered oyster shells and few or no diagnostic markers, and, finally, in the southern part of the Edwards Plateau, only a thin "break" or receding ledge. Near Goodland, Oklahoma the probable equivalent of the W alnut i& 3 to 6 feet of persistent, hard, thin, coquina-like limestone, with interbedded thin layers of dark marly shale (1530, p. 135). On Red River, north of Gainesville, the Walnut is represented by 4 feet of marly clay containing Exogyra texana and Gryphaea marcoui (l89, p. 15). Near Marysville, the Walnut consists of a small thickness of marl and marly limestone with the usual fossils. At Preston, and in Little Mineral Creek, Grayson County, the Walnut is represented by a few clay layers containing Exogyra texana (803, p. 208) . The difficulties in mapping and identifying the W alnut in this district have been most clearly realized and expressed by Winton (1791, pp. 16-18) in treating the Denton County area. The top of the formation is a widely persistent, consolidated, and mappable Gryphaea marcoui shell aggregate, 16-18 feet thick. Under this cap are sands, sandstones, and a few clay seams, which continue down to a coarse red sandstone (Paluxy), which lithologi­cally is distinguishable from the finer-grained and lighter-colored Walnut sands. On the Clear Fork of the Trinity west of Fort Worth, the shell aggregate of the Walnut is 5 to 8 feet thick, and is underlain by about 100 feet of Walnut sands. At Decatur (803, p. 208), the W alnut is about 27 feet thick, with only a thin shell agglomerate at the top. Wells in Tarrant and Johnson counties show about 100 feet of W alnut, with sorne water sands. Logs of Dallas County wells indicate 50 feet or more of the formation. In Johnson County, both outcrop and wells indicate a thickness of about 100 feet, of which the upper 25 feet is shell aggregate and the lower part mostly soft light-colored sands, with a few thin ledges of grayish sandstone, which forro a water reservoir of small volume (1790, p. 20) . At Comanche Peak, the formation consists of 30 feet of shale, marly limestone, and sands (803, p. 209). Various wells in eastern Hill County show 145-215 feet of Walnut; in western Hill County. 120--135 feet, Scott and Hawley consider the Walnut to he uniformly ahout 27 feet thick in the area west and northwest of Fort Worth, and to he limited to the cal· careous sediments, including the Gryphaea marcouí, shell hanks. The under· lying sands they refer to the Paluxy. In the Lampasas Cut Plain in Bosque, Coryell, McLennan, and Bell counties, the type W alnut is best developed~ Here it has lost its sandy base, and retains the massive shell aggregates. It is 100 to 182 feet thick, and thickness down dip. It makes long west­ward reentrants up the stream valleys, and, in general, covers large areas in the lowlands, as in Coryell County. It consists of gray­black, calcareous clay and seams of thin bedded limestone, thicker chalky nodular limestone, and shell aggregates. The formation is extremely rich in ammonites, pelecypoda, gastropoda, echinoidea, and other fossils. In Bosque County, Hill (803, p. 206) gives a section of 96 feet of Walnut, consisting of marly limestone beds, alternating with harder and more crystalline limestone and very limy marl. The formation contains a large assortment of fossils, with the usual oysters and Oxytropidoceras. At Comanche Peak, it is 121 feet thick. In the Iredell section Taff (1574, p. 305) lists 102 feet, with the same lithology and fossils. In the Walnut Springs section Taff (1574, p. 306) records 74 feet of Walnut, composed of marly and chalky limestone, compact crystalline limestone, and limy shell marls, containing a typical W alnut fauna: Exogyra texana Roemer, Gryphaea marcoui Hill and Vaughan, Cyprimeria texana (Roemer), Protocardia texana {Conrad), Natica, Trigonia, Holec­fJ'pus, Heteraster, and others. Unfortunately the real zonal fossils of this formation are rare, and do not appear in usual lists. W estward across the Callahan divide to the Llano Estacado, the Walnut forros a constantly thinning layer above the basal {Paluxy) sand and beneath the prominent Fredericksburg limestones {page 321) . This formation has an irregular but small thickness: 55 feet at Twin Sisters Peak, Lampasas County; 10 feet in Brady Mountains, McCulloch County; 6 feet at Monument Mountain, Toro Green County; 12 feet at the Camp section, Crockett County; 8 feet at Castle Mountain, southeastern Crane County; a solid mass of 5 feet of Gryphaea aggregate at Double Mountain, Stonewall County. On a more northern, parallel, section the W alnut is 20 feet thick at Round Mountain, Comanche County; 5 to 10 feet thick at the Santa Anna glass sand pit; 20 feet thick ~t Baker Mountain, The Geology of Texas-Mesozoic Systems 331 Callahan County; 4 feet thick at Bu:ffalo Gap, Taylor County; 10 fcet thick in Runnels County; 15 feet thick on Bitter Creek, Nolan County; no marl represented, at Stepp Mountain, Coke County; 8 feet thiek at Signa! Peak, Howard County; no marl represented, in the F ort Stockton area. South of the Brazos, the marl facies of the W alnut becomes gradually thinner, and the remaining basal Fredericksburg prob­ahly equivalent to type Walnut, locally takes on non-Walnut facies. In western Bell County, typical Walnut is at least 150 feet thick; in northern Williamson County, near Bertram and Bagdad, it is given as 30 to 40 feet thick by Hill (803, p. 210), and south of Florence, in the same area, the Gryphaea banks are absent. Here much of the position of the W alnut is occupied by a limestone lentil, which is here designated Cedar Park member (type locality: quarries, about 2 miles northwest of Cedar Park). It occurs over a considerable area in western Williamson County, and grades out northwards into Walnut of the type facies. It typically consists84 of about 58 feet (in core tests) of limestone, crystalline and porous above, and more marly and nodular below. The upper part (about 15 feet) is a solid, medium-grained, grayish limestone, weathering yellow, with but few scattered fossils (Exogyra texana, Ostrea, gastropods) ; beneath it is a few feet of porous limestone, with sorne caprinids and mollusca, and great numbers of cavities of Trigonia; other fossils are Exogyra texana, Protocardia, Corbis, and Turritella. Both limestones are used for building stone; the new Travis County courthouse is huilt of the Trigonia stone. The basal portion of the Cedar Park member is somewhat nodular and fóssiliferous. The hase is ahout 5 feet of typical W alnut marl with many Exogyra texana and other usual fossils. These three portions are exposed in a facies transitional to the type W alnut on the blu:ffs of the South San Gabriel at the highway crossing north of Leander, where they overlie the Glen Rose. In the Cedar Park area the lime­stone lentil in the basal Fredericksburg reaches 125 feet in thick­ ness, and prohahly covers seferal square miles. From this point south and west, the W alnut as ordinarily under­stood, is an insignificant shell marl less than 15 feet thick, which is persistent and has been used as a structural marker. Locally, in the southern Edwards Platean, it dwindles to a mere "break," "From Jield work by H. C. Fountain. a receding plane between thick Edwards strata. This marl has the usual long-range Fredericksburg species, most commonly Exogyra texana and Gryphaea marcoui, and may be lithologically indistinguishable from other thin Fredericksburg marls. Regarding W alnut as a facies only, this southern attenuated Walnut is a thin portion of the type W alnut. In the Colorado Valley, Hill (803, pp. 210-211) assigns 10 to 15 feet to the W alnut. In the plateau region west of Austin, it makes a thin stratum of yellow, calcareous clay, lying above the Glen Rose limestone and below the Comanche Peak, and weathers into either a steep marl slope or, more typically, into a flat terrace or bench, forming a platform for the overlying Comanche Peak­Edwards limestones. This yellowish, untimbered band is con­spicuous at many places in western Travis County. The Walnut here contains echinoids (Holectypus, Heteraster, Salenia), pelecy­pods, gastropods, and Engonoceras but no Oxytropidoceras. At places it contains Loriolia texana and Porocystis, which indicates that locally the band called Walnut may be of Glen Rose age. At a few localities, rare and undescribed ammonites have been collected. In a butte on the Travis-Blanco county line, Hill assigns 31 feet to the W alnut; at Shovel Mountain, Blanco County ( 803, p. 211) , 20 feet; and at Fredericksburg, 10 feet of yellow calcareous clay with Exogyra texana (795, p. 221). At Kerrville it is assigned a thickness of 1 foot; in Real County it is an intermittent thin yellow­brown clay, absent at most places (Russell F. Ryan, oral communi­cation). This situation largely persists west to the Pecos. In the Pecos Valley, only thin Walnut is on record, 8 to 14 feet in the lower Pecos Valley, and 2 to 3 feet farther north (991, pp. 52ff). Around Girvin and Fort Stockton, no clay is present in its position, and any limestone referred to W alnut must be confirmed by fossils, at present an impossible task. In the Gap Tank area, 50 feet of marls, sandy marls, and thin limestones lie between the Maxon s~ndstone below and limestones of the Edwards reef facies above (936, p. 93); what part of this is of Walnut age is unknown in the absence of decisive zonal fossils. Other thicknesses in the Big Bend are: Solitario, abo~t 50 feet; southern Quitmans, about 100 feet (46, p. 26); Van Horn Moun­tains, a considerable thickness; at Shafter, it is .apparently absent. The Geology of Texas-Mesozoic Systems 333 From these facts it is clear that (1) the southern "Walnut" corresponds to only a small part of the type W alnut, and at most places is not identifiable as Walnut; (2) on account of facies changes, no correlation of the southern "Walnut" can be made on lithology alone (it is useful locally as a datum plane), but an accurate fossil zonation is nocessary for any eventual correlation; (3) Exogyra texana and Gryphaea marcoui do not identify the W alnut, because where the facies is favorable they range far out­side it; where the section contains rudistid, marginal, or other unfavorable facies, their apparently restricted range is illusory. Lithology and microscopic features.-No material has been pub· lished on the numerous foraminifera and ostracoda of this forma­tion, nor has the mineral content been well investigated. Thickness and dip.-At what rate the formation dips coastward in the Gulf Coastal Plain can only be inferred from adjacent forma­tions. lt seems absent or unidentified in southern Texas, as in Maverick County (1681, p. 257) and at Luling (165, p. 646). In southwestern Bexar County (888, p. 770), it is only 20 feet thick. lt is, therefore, a formation essep.tially local to north-central Texas. At Mexia there is 40 feet or less of Walnut; in the interior salt domes and the East Texas oil fields it has not been well identified. Paleontology and zonation.-No good zones have been established, and probably the entire formation represents only a short time interval on account of rapid deposition. Metengonoceras sp. aff. hilli Bohm may mark the formation. Species of Oxytro pidoceras seem common to it and the overlying Comanche Peak in its more marly phase. Unidentified plant stems have been reported by H. C. Fountain from the Walnut along the Georgetown-Lampasas road 2 miles west of Briggs, Williamson County. Foraminifera from Walnut formation (From three localities in vicinity of Austin, the Mount Barker outcrop being richest in species) Haplostiche texana (Conrad) Ammobaculites subcretacea Cushman Cyclammina sp. and Alexander Choffatella sp. aff. decipiens Schlum­Flabellammina alexanderi Cushman herger Textularia rioensis Carsey Lituola sp. Textularia washitensis Carsey Ammobaculites goodlandensis Cush­Verneuilina schizea Cushman and man and Alexander Alexander Valvulina sp. Vaginulina inturnescens Reuss Orbitolina walnutensis Carsey ( =Dic­Patellina subcretacea Cushman and tyoconous according to Silvestri, Alexander 1479a) Globigerina washitensis Carsey Orbitolina sp. cf. texana (Roemer ) COMANCHE PEAK FORMATION (INCLUDING GOODLAND) Nomenclature.-This formation was called the "Comanche Peak group" in 1860 by Shumard (1463, pp. 583-585), who placed it correctly below the Edwards ("Caprina") limestone and incor­rectly above the Austin chalk. lts type locality is at the famous lndian landmark, Comanche Peak, central Hood County, and the formation is best developed in the Brazos and Trinity valleys. Stratigraphic position and contacts.-Thickness relations indicate that the Comanche Peak is a facies of the Fredericksburg, and may be in part laterally continuous with Walnut below and Edwards above. No adequate zonation allows a check of this assumption, but certainly to the south the rudistid facies ("Edwards") invades ali levels of the Fredericksburg group, and therefore is presumably equivalent in part to type Comanche Peak. Both upper and lower contacts of the Comanche Peak appear to. be concordant, according to published reports. Facies.-The Comanche Peak is a chalky-limy facies. To the north it is continuous with the "Goodland" limestone, which is of the same lithology and fossils (1575, p. 256). Throughout central Texas and the Callaban divide, it maintains the same lithology; in the marginal areas (Red River valley, southern Oklahoma, north of Fort Stockton and Kent, at Sierra Prieta), it presumably goes into a marginal sandy phase. Areal outcrop, local section. -The Goodland limestone in the Red River valley is the same as the Comanche Peak, becatise (1) Edwards is defined as consisting of the rudistid facies and similar rock, and does not outcrop north of Fort Worth; and (2) the Good­land contains Oxytro pidoceras acutocarinatum, a species which marks the middle and lower parts of the Fredericksburg group. At Goodland (803, p. 217) the limestone is less than 20 feet thick. The rock is fractured, crystalline, whitish limestone, resembling Comanche Peak in lithology, and contains undiagnostic fossils: Engonoceras a:ff. hilli Bohm, Exogyra texana Roemer, Cerithium bosquense Shumard, and many pelecypods arid gastropods. The Giology of Texas-Mesozoic Systems 335 The eastei;nmost outcrop of the Goodland is north and east of Cerro Gordo, Arkansas, and about 4 miles down Little River from it. It consists of 50 feet or less of thick-bedded, gray, sandy limestone, containing sorne beds of hard, yellow-gray, calcareous sandstone. At sorne horizons, the Goodland beds are notably lenticular; lentils of limestone 6 feet long and a foot thick, of varying degrees of sandiness, stand at small angles with the normal bedding. The upper 8 feet of the formation, where exposed, is a less sandy limestone. The top is a ledge a foot thick, of hard, white limestone, which weathers into cavernous slabs. The Goodland is overlain by about 20 feet of Kiamichi clay containing Grypha.ea navia (392, pp. 15­16). In Grayson County, the Goodland, overlying 6 feet of marl, shale and thin seams of limestone and shell aggregates, consists of about 15 to 20 feet of hard, white, semi-crystalline limestone, generally in four beds each 4 to 6 feet thick. It weathers by conchoidal fiaking, and develops a honey-comb surface by erosion of softer pockets. In Marshall County, Oklahoma, 15 to 20 feet is recorded; in Love County, about 25 feet. It contains Oxytropidoceras aff. supani, pelecypods, and gastropods, including a hrrge smooth oyster some­what like Exogyra americana Marcou. In northern Cooke County, the Goodland is 25 feet thick, in southern Cooke County, 40 feet. At a variable distance (2 to 16 feet) below the top, there is a horizon of Exogyra plexa Cragin. At a variable level (3 to 9 feet) above the base, a zone of abundance of Gryphaea marcoui is recorded . Oxy. acutocarinatum is reported throughout the forma­tion. Other fossils are: Remondia robbinsi (White) , Protocardia, Pholadomya, Pecten, Turritella, Cerithium bosquense, and Heter­aster. The W alnut shell aggregate is absent, and the thin Walnut clay rests on sandy beds containing Grypha.ea marcoui and Ostrea crenulimargo Roemer. This aggregation of fossils is not diagnostic, but suggests Comanche Peak, not Edwards. The formation thickens, from 42 feet in northem Denton County and 75 feet in southwestern Denton County, to 116 feet near Lake Worth, Tarrant County. The marly limestones and limy marls of the Goodland forro large hills on the Clear Fork and West Fork of the Trinity in western Tarrant and eastern Parker counties. Near Benbrook, there are large, richly fossiliferous exposures. At Lake Worth Dam, a complete section shows an alternation of more limy and more marly beds, lying above the massive Gryph~a marcoui aggregate capping the W alnut and the base of the Kiamichi clay. Dipoloceras and Oxytropidoceras range from bottom to top of this. section. Local zones (9, pp. 15-31) are probably applicable from this area to the Red River valley. At the type locality, Comanche Peak (1574, p. 311), it is 66 feet thick. Its ' typical lithology is. chalky, fossiliferous limestone in fairly massive beds. There is. considerable jointing or flaking, which gives the limestone a frac­tured appearance. Sorne slight, irregular, marly seams bound the· limy beds. It weathers to a dull whitish-chalky color. Calcite and calcitized fossils are frequent. Topographically it forms steep slopes, in contrast to the more massive, bluff-forming Edwards above, and the soft, valley-forming W alnut clay below; it forms numerous round-topped buttes and outliers where the more precipitous. Edwards cap has been removed. This lithology is distinctive­throughout central Texas; it may be seen on a large scale at Ben·· brook, Comanche Peak, and Valley Mills. The ridges and buttes of the Lampasas Cut Plain in Somervell,. Bosque, Coryell, western Bell, and western McLennan counties,. show on their upper slopes typical Comanche Peak, In the breaks. of the Edwards scarp west -::f Oglesby and near Copperas Cove, it. is excellently displayed. It overlies the thin W alnut clay remnant in the buttes of the­Callahan Divide, and occurs in the eastern rim of the Llano Esta­cado. At most of these localities it is with difficulty distinguished· from the Edwards. At Round Mountain, Comanche County, 60• feet is reported; at Santa Anna, 40 feet; in Taylor Comity, 60 to 80\ feet; in Runnels County, 21 feet; at Stepp Mountain, Coke County, about 90 feet; at Signal Peak, Howard County, about 70 feet; at. Double Mountain, Stonewall County ( 467), 55 feet. In southern Hill County, south of Blum, the Brazos bluffs show· complete sections of the Comanche Peak for miles. Similar excel-· lent exposures occur with abundant fossils in the Bosque valley· near Valley Mills. Southwards, down the east side of the Leoru Valley, long exposures cross Coryell County and continue to northern: Bell County (16, pp. 33-34). In western Bell County the formation is about 100 feet thick, and weathers as grayish-white, flattened,. ncidular, fossiliferous limestone, forming the upper steep scarps of The Geology of Texas-Mesozoic Systems 337 ridges and outliers in the Lampasas Cut Plain. In the Burnet quad­rangle, it ranges from 70 feet in the north, to 40 feet in the south. Near Leander, it has a thickness of 75 feet or less. In the Austin area (1429, p. 44) its outcrop thickness is 49 to 55 feet. Here it consists of marly, grayish·white limestone, with compressed nodules, and the flaking and jointing already described. The W alnut differs from it in being more marly, and in having uncompressed nodules imbedded in a considerable amount of marly matrix. Here the formation contains echinoids, pelecypods, gastropods, tall conical Orbitolina (O. walnutensis}, and other fossils. Along the southern margin of the Edwards Plateau, the formation consists of about 35 feet of nodular, whitish, sparsely fossiliferous límestone, overlying the soft, abundantly fossiliferous Walnut clay, and underlying the massive, hard, gray, flint-bearing Edwards lime­stone. The Comanche Peak contains Exogyra texana, Gryphaea mar­coui and pelecypod and gastropod casts. In the Nueces quadrangle there is 40 to 50 feet, in the Uvalde quadrangle 60 feet, of yellow­weathering, nodular, argillaceous limestone, containing Exogyra texana, which represents the Comanche Peak. In these areas the Walnut is absent, but the Exogyra is more abundant at the base of the limes tone. In the lower Pecos V alley 2 to 12 feet of nodular limestone, containing Exogyra texana, Protocardia texana and Lunatia pedernalis, occurs (991, pp. 52-60). Thickness and dip.-The formation does not reach a thickness of oyer 150 feet. It is apparently gradational and conformable into the Edwards and the Walnut, and has the same attitude and dip as those formations. Its greatest thickness is in the Brazos and Colorado valleys. In the Red River valley, it is reduced to an insignificant thickness, and, on approaching the Rio Grande, it is either indistinguishable from the overlying greatly thickened Edwards limestone, or else persists as a thin nodular limestone. These facts strongly suggest that the Comanche Peak is not of the same age throughout its extent, but that it is a nodular facies, present at various Fredericksburg levels. Paleontology and zonation.-No Comanche Peak· zone fossils are known. The correlation is discussed under the "Edwards forma­tion." The following are the most distinctive ostracoda of the Goodland (Comanche Peak) in north-central Texas:35 Cythereis mahonae Alexander Cytliereis fredericksburgensis Alexander Cytherella fredericksburgensis Alexander Cytheropteron howelli Alexander Cythereis carpenteri Alexander Oower Goodland only) Cytheridea oliverensis Alexander Bythocrypris goodlandensis Alexander (not common) Cytheridea goodlandensis Alexander Paracypris siliqua Jones and Rinde The following are the most distinctive foraminifera of the Good· land: Foraminifera from Goodland formation (Three localities in the vicinity of Fort Worth) Ammobaculites subcretacea Cushman Spiroplectammina sp. and Alexander Verneuilina schizea Cushman and Ammobaculites goodlandensis Cush­Alexander man and Alexander Valvulina sp. Frankeina goodlandensis Cu s h man Vaginulina marginulinoides Reuss and Alexander Vaginulina intumescens Reuss Flabellammina alexanderi Cushman Globulina exserta ( Berthelin) Spiroplectammina scotti Cushman and Patellina subcretacea Cushman and Alexander Alexander Spiroplectammina whitneyi Cushman and Alexander Economic products.-At places the Goodland or Comanche Peak is a nearly pure limestone, and can be used with the Kiamichi clay for Portland cement. The El Paso cement plant uses lime from this level. Locally it is used for road metal. EDWARDS FORMATION Nomenclature.-The name Edwards,36 of Hill and Vaughan (795), replaced the terms Caprina limestone of B. F. Shumard (1463, pp. 583-584), and Barton Creek limestone of Hill (735, p. 5; 751, p. 23). Other local members of the Edwards near Austin are the "Flag limestones" (lithographic horizon), the "Austin •This and the following lista of ostracoda were kindly furnished by Dr. C. l. Alexander. 86Literature.-Hill, 803; Hill and Vaughan, 794, 795, 808; Hanna, 647a ; Taff, 1574, 1575. Paleontology: Cragin, 324; H'ill. 784;o Merrill, 1103; Roemer, 1335; Stanton, 1522; White, 1738. The Geology of Texas-Mesozoic Systems 339 marble" (Caprotina horizon), and the "chalky limestone sub­division" (735, pp. xix-xxii). The type locality of the Edwards is on Barton Creek near Austin. Stratigraphic position and contacts.-From Fort Worth to south of Waco, the Edwards gradually thickens, and is overlain, appar­ently unconformably, by the Kiamichi clay. South of Waco, the Kiamichi is absent, and the Edwards is overlain by Duck Creek limestone. The Edwards-Duck Creek contact shows evidence of unconformity in Bell County (16, p. 40). Its lower contact with the Comanche Peak is continuous and gradational where it has been recorded. Facies.-(I) Marginal facies exists at Sierra Prieta north of Sierra Blanca, where brown cross-bedded sandstone containing Alectryonia cf. carinata and other poor casts composes the section below the basal (Hamites·Desmoceras} zone of the Duck Creek limestone. In the Rycade Chittim No. 2 well in eastern Maverick County, 20 feet of coarsely crystalline rock salt is recorded (578, p. 1426), presumably near the top of the Edwards, with 779 feet of liniestone between it and the Del Rio clay. In nearly pure, heavy­bedded limestones, in the southern part of the Edwards Platean, fossil logs are recorded (578, p. 1427): a dicotyledonous log 18 inches in diameter near Mine Creek, northern Uvalde County; a palm-like log 20 inches in diameter near Barksdale, southeastern Edwards County. Silicified wood also occurs in basal Edwards in southern Real County. It is not known whether these logs floated to their present locations, or whether they indicate proximity of the marginal facies. (2) Neritic facies occurs in the forro of mar! at Fort Stockton, here called University Mesa marl. Marly lime­stone occupies the top of the Fredericksburg at many places (El Paso, Round Rock) . (3) Reef limestones and associated rocks compose the typical Edwards; these rocks, diverse in lithology, are discussed below. Dr. Decker has recently discovered a rudistid ( caprinid) deposit in the Fredericksburg in southern Oklahoma, the northernmost known in this longitude. Areal outcrop, local sections.-The northernmost recorded Edwards is at Fort Worth, where a few feet of crystalline, thin-to medium-bedded limestone contains masses of undetermined caprinid casts (Gayle Scott, personal communication); at Benbrook a rudis­tid was reported in the top of the Goodland (1575). Hill considers the Edwards to be 4 feet thick here. lt is harder, more crystalline, and more prominently cliff-forming than the underlying Comanche Peak. In southwestern Johnson County, about 35 feet of Edwards is recórded. In the cap of Comanche Peak 33 to 35 feet remain, of which the upper 3 feet contains Eoradiolites davidsoni and Chon­drodonta munsoni. The formation is composed of layers of hard white limestone, each from 3 inches to 10 feet thick, below which i~ a massive bed 15 feet thick, forming the main upper scarp of the peak. In Hill Cqunty below Blum, the Brazos has cut tall cliffs capped by Edwards, which continue downstream across Hill County. The Edwards is 50 to 75 feet thick, and consists of rudistid lime­stone, a hard, crystalline, medium-to-massive-bedded, white lime­stone, composed of considerable calcareous shell detritus and sorne precipitated limestone. lt contains Eoradiolites, Chondrodonta, T ou­casia, Requienia, caprinids, Pecten, and other reef forros. This lime­stone is exposed in Nolands River just north and west of Blum, and in road cuts south of the town. Tall cliffs oc~ur along the Bosque Valley east of Clifton and around V alley Mills. In the upper strata of nearly pure, white, crystalline reef limestone, abundant rudistids occur, as Caprina crassifibra Roemer, Caprinula anguis (Roemer), Eoradiolites spp., Toucasia texana (Roemer); and Chondrodonta munsoni (Hill), pelecypods, and gastropods. At localities on the Meridian Highway 2 to 3 miles east of Valley Mills, the Edwards consists of alternations of whitish nodular limestone, with the usual upper Fredericksburg fauna of pelecypods .and gastropods, and massive, harder, crystalline reef limestone with rudistids. Caves and rock shelters nearby contain many rudistids. In one of the softer layers east of Valley Mills, the plicate inoceramus, Actinoce­ramus subsulcatif ormis Bose, was fo un d. Other fossils include Exogyra texana Roemer, Lima wacoensis Roemer, Cardita, Gryphaea marcoui Hill and Vaughan, Engonoceras, and species of Oxytro pi­doceras. In facies, this soft, marly upper Edwards is similar to that at Round Rock; the top of the Edwards in Hill County is uniformly a massive pure limestone with a tangle of Caprinidae, rudistids, Chondrodonta, and other reef dwellers. In McLennan County, the Edwards is massive, pure (99.4% CaC03 ), unstained, rudistid limestone. An excellent exposure, studied and collected by Dr. T. W. Stanton about 1890, is at the west crossing of Bluff Creek, 3.5 miles northwest of Crawford, The Geology of Texas-Mesozoic Systems 341 where the limestone is 60 feet or more thick. The exposures consist of alternate, medium-bedded harder projecting and less resistant receding, pure, white limestone ledges. They contain much calcite, and so little iron that the exposures show practically no ferruginous stain. A few ledges at the top are softer. The limestone is a shell debris, as in the reefs west of Belton and at Oglesby. The Edwards here contains a large typical fauna, including Caprina crassifibra, Caprinula anguis, Plagioptychus? cordatus Roemer, Eoradiolites davidsoni (Hill), Radiolites(?) sp., Toucasia texana, Toucasia sp., Caprina sp., Caprotina sp., Chondrodonta munsoni, and others (11, pp. 35-37). The Edwards also outcrops in McLennan County along Middle Bosque River, from a point 2 miles west of Windsor north­west to the Bosque County line, including the area east of Crawford and along Bluff Creek. West of its reentrant down North Bosque River at Valley Milis, the outcrop turns westward and follows down Leon River across western Coryell County to Belton. At Patton, in the bed of Hog Creek, the basal Duck Creek and 3 feet of Kiamichi marl occur; beneath them is the top layer of pure reef limestone with the rudistids mentioned ahove. On the Meridian Highway, 0.4 mile west of the McLennan-Bosque county line, beneath ahout 9 feet of Kiamichi marl, the top of the Edwards, with similar lithology and fossils, is exposed. In the creeks about a mile east of Crawford, the same contact is exposed, and beneath it, ahout 25 feet of fossiliferous .Edwards. In the bed of North Bosque River, 3.5 miles southwest of China Springs, heneath 4 feet of Kiamichi, a few feet of uppermost Edwards occurs (11, p. 40). In Middle Bosque River, 2 miles west of Windsor, about 25 feet of upper Edwards, consisting of alternate reef and gray nodular limestones, occurs. North of Bell County, the Edwards lithology shows three main types: soft, nodular, marly, gray limestone and marl with non-reef pelecypods, gastropods, and echinoids; harder chalky-gray lime­stone with slight clay content, and a non-reef fauna; and pure dazzling white, calcitic, limestone, hard to friable, much of it composed largely of shell debris and precipitated lime, with a reef fauna. From Bell County southwards other types appear. Here the formation caps the upland west of the Balcones fault zone, running from Leon River west to Sugar Loaf Gap north of Killeen, along the north county line. In the northwest quarter GÍ the county it forros a large upland, deeply cut to the soft Walnut clay in the valleys of streams flowing down-dip. A broad plain is formed by the valley of Nolan Creek, west of Belton. In the southwest quarter of the county the main Edwards outcrop narrows to a few miles in width, and forros the back slope of a long cuesta running eastwards from the valley of Lampasas River. These Walnut valley interstream divides, buttes ( outliers) , and the west-fronting cuesta face of the Edwards-Comanche Peak scarp, compose the Lampasas Cut Plain of Hill. It is notable that late movenients in connection with the Balcones Fault have produced typical intrenched meanders of considerable depth in Bell County (as Leon River) and McLennan County {as Bluf! Creek), by rejuvenating the streams and increasing their gradients. The Edwards here, and generally, is distinguished from the underlying Comanche Peak facies by having: (1) persistent strata of limestone, even-bedded and medium-to-massive in thickness, instead of compressed chalky limestone nodules with a subordinate a.mount of marly matrix; (2) flint, in nodules and in thin strata; (3) rudistids and caprinids, of the genera Toucasia, Requienia, Mono pleura, Caprina (these four occur also in the Glen Rose), Caprinula, Caprotina (?), Plagioptychus (?), Planocaprina (?), Polyconites ·(?); Praeradiolites, Eoradiolites, Sauvagesia, and others; (4) other reef-dwelling fossils, as those from the Edwards described by C. A. White and F. Roemer, most of them apparently zone fossils: Chondrodonta munsoni, Phacoides acute~lineolatus, Trochus texanus, Cladophyllia furcifera, and others; (5) reef lime­stone: a nearly pure, white Qr light gray detrital or fragmenta! shell coquina and associated precipitated calcium carbonate, composed mainly of comminuted shell fragments, and containing much calcite as shells and as free masses; (6) other kinds of limestone, whose exact mode of deposition has not been investigated, as miliolid limestones, sandy limestone, and sandy, limy clay, both finely laminated, silty layers; and (7) pulverulent layers of finely divided, nearly pure, calcium carbonate, produced by intraformational solu­tion and redeposition, and, associated with it, disintegrated remains of "honey-comb" limestone from which much of the lime has been dissolved. These pulverulent layers are at places associated with anticlinal structure; they occur on the Kolls place west of Belton, on Barton Greek and in Deep Eddy Bluf! at Austin, in numerous The Geology of Texas-Mesozoic Systems 343 cavés near Crawford, Valley Milis, Austin, and in the Edwards Platean and canyon region of the Pecos and Rio Grande valleys. Rudistids become disengaged in such weathering layers and occur free in large numbers. The pulverulent limestone has been used commercially on a small scale; the honeycomb rock, from Glen Rose, Edwards, and other formations; is locally used as ornamental stone. A soft formation, called "adobe,'' occurs near the top of the Edwards in central Texas, and forms the producing horizon in the Luling oil field. In Bell County the top of the formation is a pure white rudistid­reef limestone, as farther north. However a few thin layers inter­bedded with the limestone are composed principally of flaky, yellow, shelly marl, containing the same fossils as the adjacent limestones, Pecten duplicicosta, Clwndrodonta, Praeradiolites, Eora­diolites, Goniopygus cf. zitteli, corals, and other fossils. The base of the formation consists of a widespread, soft, water-hearing silt­stone, weathering yellow, and containing few fossils except casts of Planocaprina (?) and other caprinids. The middle of the forma· tion contains several limestones associated with the purer coquina and Requienia-limestones: (1) a dense, ringing, fine-grained, medium-to thin-bedded limestone, light bluish-gray or dull buH­gray, with faint salmon-reddish cast or streaks, which contains numerous imhedded small calcitic fossils, visible as cross-sections on fracture. This rock is mostly non-siliceous, hut locally contains flints. It has a prominent conchoidal fracture, splits easily, and is a good building stone. In texture it resembles fine-grained Ellen­burger limestone. (2) A prominent type is a shell coquina of rudistids, caprinids, gastropods, pelecypods, corals, echinoids, and other fossils, cemented into a porous or cavemous mass of shell agglomerate and debris. This rock is a part of the rudistid reef facies. At some places it is entirely calcareous, and may he sawed into building and paving stone. lt is full of cross-sections of rudistids, caprinids, Nerinea, and other gastropods. At other places the fossils are partially silicified, and the matrix, only slightly so, decomposes into a very ferruginous clay, disengaging the fossils upon weathering. The rock and clay hear considerable iron, and weather to a dark red color. The fossils include foraminifera. (Haplosticke texana, Orbitolina, and others), many gastropods, corals, caprinids. and rudistids. (3) A common type, excellently exposed at the Santa Fe quarry 3 miles northwest of Belton, is a coquina of comminuted shell fragments, with many entire shells, of the rudistid reef facies. It is a white or light bluish-gray, entirely crystalline, rather soft calcareous deposit, with a composition of 3% or less of silica, and the rest practically pure calcium carbonate. Prominent fossils are foraminifera, corals, caprinids, rudistids (Eora.diolites, Polyconites?), pelecypods (Plagiostoma, Lima, Pecten}, gastropods, echinoids, bryozoa, worms, corals, and other groups. In Williamson County, the Edwards is thicker, and locally is u~ed for building stone and for lime manufacture. Hill (803, p. 236) gives a thickness of about 230 feet for the Edwards near Round Rock. A persistent sulphur water horizon occurs near its top. The top is well displayed in Brushy Creek at Round Rock near the Balcones Fault. Beneath the Duck Creek memher of the George­town limestone, there is 5.5 feet of gray-blue marl with Oxytropido­ceras supani (Lasswitz), Tylostoma sp., Exogyra texana Roemer and other fossils, an upper Fredericksburg fauna. Ta:ff (1574, p. 344) considers this stratum as Kiamichi, but classifies the Kiamichi as of Fredericksburg age. Pending the discovery of diagnostic Kiamichi fossils at this locality, the identification with Kiamichi will have to remain in doubt; but in any event, the Kiamichi is very close in age to upper Edwards, di:ffering largely in the presence of Gryphaea navia and a few other zone fossils; Oxytropidoceras supani apparently occurs in both the Kiamichi (Fort Stockton) and the upper Goodland (southern Oklahoma), but this genus requires intensive study before this upper Fredericksburg group of fine ribbed species can be used for minute stratigraphic distinctions. The thin uppermost elay is undei:lain by a T oucasia-Requienia reef, about 5 to 10 feet thick, a massive limestone, in which are cemented . innumerable rudistids, The upper one-third of the Edwards con­tains at least four zones of rudistid limestone; in the upper reef limestone, 6 feet below the top of the Edwards, is an abundance of Eoradiolites, and at a leve! about 50 feet below the top, both here and at Austin, a main leve! of Chondrodonta. The middle one-third oí the limestone is non-reef limestone, and contains severa! promi­nent bands of flint nodules; the lower one-third contains in addition to the hard, gray limestone, with strong conchoidal fracture, at least one band of reef limestone. The Geology of Texas-Mesozoic Systems 345 Near Austin, the Edwards is 300 feet thick or more {808, 1429). Its upper one·third contains a:t least four levels of reef type of lime· stone and a prominent flint band. Its middle one-third contains mostly non-reef limestone and severa} flint bands. Its basal one· third contains four or more reef bands and basally sorne sandy strata. A widespread sulphur water horizon is located near the top of the Edwards. Requienia and Toucasia are present from top to bottom of the Edwards, and in the Glen Rose. Local correlation can be hased on intervals and on the presence, in various horizons, of flints of characteristic shape or size. The Edwards limestone caps the highest summits of the Callahan Divide, and extends westward to the cap of the Llano Estacado. In both these areas it possesses its typical lithology, flints and sorne characteristic fossils. In Comanche Peak, Hood County, it is 35+ feet thick. At Lp of the unit. The lower one-third of the unit is blue clay, capped by a 10-foot bed of black shale having near its top a 3-inch bentonite seam; it is overlain by 20 feet of white or yellowish laminated marl. This basal third of the unit seems to disappear north of Denton County and south of Hill Ce>unty, leaving the upper Britton in contact with the Grayson (or Pepper). The upper blue clay portion of the Britton is continuous from Red River to Austin. lt is thickest in the Iatitude of Dallas, thinner to the north, being represented by 30 to 50 feet of blue sandy clay, and at Austin is reduced to a few feet mainly by thinning of the several beds. The Britton grades upward into the Arcadia Park. Met. swallovi occurs in the base of the Eagle Ford in Grayson County, and at Slate Shoals, Lamar County, in sandy clay. Fossils: The Britton contains two zones: (a) basal one-third, zone of Metoi­coceras irwini Moreman; (b) upper portion, zone of Metoicoceras whitei Hyatt. Other fossils in Britton fonnation: Metoicoéeras gibb<>sum Hyatt, Placenticeras pseudoplacenta var. occidentale Hyatt, Baculites gracilis Shu­mard, lnoceramus labiatus Schlotheim, In.oc. capulus Shumard. The type locality of the Britton clay may be taken as tributary of Newton Branch 3% miles south of Britton, on the Wdlothian road. Arcadia Park shale.-Type locality: Arcadia Park station, 7 miles west of Dallas, on the Fort Worth.Dallas interurban. Typical thickness: about 100 feet; thins to north and to south, about 10 feet thick at Austin. Lithology: The type section consists of basally 20 f~ of blue clay; then 1 to 3 feet of thin limestone flags forming escarpment and dip-slope; the upper part, 75 feet of blue shale containing numerous calcareous concretions of various sizes. On Red River the upper part is sandy and the lower part blue shaly clay with a few thin scattered sandstone seams. Southwards, in McLennan and Bell counties, the unit is laminated marl; at Austin the lower part is flaggy, laminated marl and the upper part blue shale. The Arcadia Park unit is un· conformably overlain by the Austin chalk; the transition zone, Taff's "Fish Bed Conglomerate" (1575, pp. 299-304), is composed of clay containing gyp­sum, phosphatic pebbles and reworked pelecypods (many Alectryonia lu,gubris) ·and fish remains. At White Rock escarpment on the Dallas-Fort Worth road, it is about a foot thick. Fossils: the ammonites are typically prionotropid; Prionotropis aff. woolgari (Mantell) is abundant in the basal part, particularly in the limestone flags, associated with lnoceramus dimidius White. The upper part contains Prionotropis, Prionocyclus, and near the top a zone of abundance of Alectryonia lugubris ( Conrad). It may be noted that in the W aco area Prather (1256, 1257) applied the · name "South Bosque marls" to the upper Eagle Ford. Facies.-Five facies occur in Texas: (1) Black shale facies (type): Lustrous shales, well laminated, black or locally pinkish-black when fresh but weathering gray to rusty-brown~ compose the bulk of the formation in riorth-central Texas as far south as Waco, where a flag member is intercalated near the base. Above the flags in south-central Texas is a black shale with bentonitic streaks. (2) Flag facies (Val Verde, 468, p. 221; Boquillas, 1626, pp. 29--33): From Waco southwards on the outcrop this member occupies increasingly more of the basal part of the Eagle Ford. Westwards from San Antonio the amount of black shale decreases, and in Val Verde, Terrell, Brewster, imd Presidio counties, ali of the Eagle Ford is of the flag facies. The transition takes place between Uvalde and Brackettville. (3 ) Clay (Mancos) facies: The Eagle Ford equivafont in the Chispa Sum­ . mit region, western Jeff Davis County, has almost entirely the clay facies, with a subordinate amount of thin platy layers and bands of septaria and concretions; it is here called the Chispa Summit fonnation. (4) Chalky limestone seams, as at Chispa Summit. The upper Eagle Ford near the Val Verde-Maverick county line is reported to be chalky, somewhat like the overlying Austin. (5) Marginal facies, composed of igneous detritus, as at King's Water Hole, Uvalde County (1009, 1686). Thtoughout central and east Texas, the Eagle Ford, especially in its upper part, contains much bentonitic and similar clayey material in thin seams inter­bedded with the flagstones or shales. The Geology of Texas-Mesozoic Systems 427 Fig. 24. Facies of Eagle Ford group in aml near Texas. Areal outcrop; local sections.-The Eagle Ford outcrop extends up Red River valley from northwestern Red River County to western Grayson County (1353, pi. 20). Thence it turns south and, passing west of Dallas and. Waco and through Austin, extends to northern Bexar County, where it turns west, parallel to the Balcones fault. lt extends west to heyond Brackettville, and then turns south through Maverick County and into the Rio Grande embayment. W est of Devils River a prominent outcrop covers much of western V al Verde and southeastern Terrell counties. There are many scattered out­crops in Trans-Pecos Texas. The largest are in southern Brewster, northwestern Presidio and southern Hudspeth counties. Smaller ·ones are on the eastern and northern edges of the Davis Mountains, near Sierra Blanca, and in and west of El Paso. Benton outcrops near Clayton, New Mexico, within ·a few miles of the New Mexico­ Texas state line. An Eagle Ford outcrop occurs on the Palestine dome, and the group is reached in many wells in the Gulf Coastal Plain. Red River counties.-The easternmost Eagle Ford mapped in Texas is in eastern Lamar and western Red River counties, extending a little east of Woodland (1353, p. 179, Pl. XX). These beds con­sist of 50 or 60 feet of fine to coarse marine sand, with a central band which contains a small percentage of water-laid volcanic material. At the base of this sand just north of Woodland there is a bed of conglomeratic sand, 11/2 feet thick, containing many water­worn pebbles of novaculite reaching a diam~ter of 1 inch and re­worked chunks of soft reddish sandstone. This material is not of the typical Eagle Ford lithology, and may represent basal Bonham clay (Austin chalk age). In western Lamar County and in Fannin County, the Woodbine sand is overlain, probably unconformably, by the Eagle Ford clay, which consists typically of 300 to 400 feet of dark, more or less bituminous clay carrying calcium carbonate concretions, in part septarian, sorne of which are fossiliferous. In the Paris city well (844, p. 27) 520 feet (8{}-600) of Eagle Ford is recorded. In Fannin County, Garretts and Sowells bluffs contain exposures of fossiliferous, septaria-bearing Eagle Ford clay, and in wells about 400 feet of Eagle Ford i.s recorded. In the Celeste well (Hunt County) the record shows 292 feet (1243-1535) or more of Eagle Ford. In Grayson County Stephenson records an estimated thickness of 300 to 400 feet of Eagle Ford. In the Fortuna Oil Company, H. M. Ryan well, 3 miles north-northwest of Tom Bean, 350 feet (555-905) of Eagle Ford was penetrated. The log of the Sherman city well shows 459 feet (32--491) of Eagle Ford. Stephenson re­ports from western Collin County 535 feet (1530, p. 147). At Sherman, about 10 feet below the base of the hard Austin chalk, there is a conglomeratic !ayer of gray sandstone, containing phos­phatic pebbles, Ostrea ali/era Cragin, and fish teeth, which Stephen­son considers·to be the basal layer of the Austin chalk deposit. This is the "fish-bed conglomerate" of Taff's reports, and is widespread . in north-cent:ral Texas. The top of the Eagle Ford here consists of 20 feet or more of clay and considerable sand, with Ostrea lugubris Conrad (= bellaplicata Shumard) . The upper part of the for­mation consists of blue clay, and sorne thin, platy sandstone and limestone layers containing Prionotropis and Prionocyclus. The The Geolo'gy of Texas-Mesozoic Systems 429 upper Eagle Ford clays carry large limestone concretions and sep­taria, sorne of them fossiliferous. Eastward from Sherman the sandy strata at. the top of the formation increase in thickness. In a creek a mile west of Bells, Stephenson records about 50 feet of ferruginous sandstone ("fish-bed"?), dark greenish-gray massive sand, and argillaceous fine sand with layers of soft yellow sand­stone. This is underlain by dark, shaly, gypsiferous, septaria-bear­ing Eagle Ford clay. The middle and basal parts of the Eagle Ford blue-black lam· inated clay are poorly exposed in this district. They contain con­cretions and nodules with ammonites and other fossils at localities about 4 miles east of Whitesboro. On Panther Creek, northeast and southeast of Rock Hill, Collin County, Taff (1575, p. 303) records a fine siliceous conglomerate or grit, containing fish teeth, at a level 18 feet below the massive Austin chalk, and just below it is Eagle Ford clay with Ostrea lugubris. On Squirrel Creek, southern Grayson County, the con­glomerate, 20 inches thick, containing Ostrea lugubris and fish teeth, occurs 10 feet below the top of the Eagle Ford, and in the ~lay beneath it large numbers of the Ostrea occur. Tarrant-Dallas section.-Wells in Dallas penetrate 500 feet of Eagle Ford (1454, pi. 20). The White Rock escarpment southwest of Dallas exposes the upper part of the formation, which consists mostly of laminated blue clay; the uppermost part contains fossil­iferous, laminated sandy limestone flags, as exposed near Arcadia Park, and lower in the section numerous large flattened limy con­cretions. Ostrea lugubris, exposed in the cut of the Dallas-Fort Worth highway, ranges clown into the Eagle Ford for 50 to 75 feet. The concretions contain Metoicoceras swallovi, "Placenticeras" syrtale var. cumminsi and other ammonites. Taff (1575, p. 292) records the basal Eagle Ford on Bear Creek near the Dallas-Tarrant county line: it begins with finely laminated, arenaceous and cal­careous clay, which contains clay segregations and fossiliferous con­cretions (Metoicoceras inequiplicalum,), followed by laminated sand, sandy clay and hard, sandy flagstones. These strata overlie stratified sand and clay carrying Lewisville fossils. The basal Eagle Ford near Tarrant station is a clay and sandy clay with Acantho­ceras and other fossils (1789, pp. 74-83). The middle Eagle Ford, exposed on Bear and Hackberry creeks, is a blue shale with numerous ammonites and other fossils. The middle and upper parts of the section near Britton and Midlothian, Ellis · County, are very fossiliferous blue-black shales with concretions and, in the . upper part, thin, flaggy layers (1141). Hill-McLennan-Bell counties.-Wells in Hill County penetrate about 133 to 365 feet of Eagle Ford. The basal Eagle Ford is a black shale, above which a small thickness of limy flags is exposed in the area west of Hillsboro. The upper Eagle Ford is a lustrous black clay with lnoceramus aff. labiatus and ammonites (Priono­tropis), well exposed in Chambers Creek near Maypearl. In Mc­Lennan County the Eagle Ford, 175 feet or less thick, is well ex­posed in the Bosque escarpment west and southwest of W aco. Here the basal, thin, black shale is fossiliferous. It is succeeded by a few feet of Eagle Ford flags. The upper shale is about 100 feet thick, and outcrops at Bosque Bridge, Potato I!ill, South Bosque, near Moody, and elsewhere. Both the flags and the upper shales contain numerous bentonite seams, up to 18 inches thick. In Bell County (16, pp. 59--61), the Eagle Ford, exclusive of the Pepper shale, consists of about 5 feet of limestone flags overlain by about ·50 feet of black or brown shale containing numerous bentonite seams. The upper Eagle Ford at many places, as near Maypearl and W aco, contains large flattened concretions and large septaria. In these counties the Eagfe Ford outcrops in a west-facing escarp­ment, which, especially northwards, where the formJitions are thicker arid the outcrop broader, expands into rolling hills, sorne of them locally capped by harder flagstone layers. These flagstones are well exposed near South Bosque and in the Blue Cut of the Santa Fe Railway south of McGregor. A similar isolated Eagle Ford exposure whose cap has been recently removed is Haunted Hill north of Moody. Williamson-Travis-Hays counties.-At Prairiedell, Bell County, where the Buda is 5 feet thick (16, pp. 50, 56), Eagle Ford flags with Acanthoceras aff. cornutum occur. In wells in Williamson County 43 to 71 feet of Eagle Ford is recorded, with greater thick­nesses down-dip. On the San Gabriel below Weir, about 50 feet is exposed, consisting of basal hlack shale, thick medial flags, and upper black shale. On Brushy Creek below Round Rock, a similar Tke Geolagy of Texas-Mesozoic Systems 431 hut thinner section occurs. The basal and upper contacts occur respectively 1 and 2 miles south of Round Rock; fossils are listed elsewhere. A complete section is exposed down Walnut Creek from Watters Park. The upper contact is well exposed in the headwaters -0f Shoal Creek, and shows phosphatic nodules and fossils in the upper 2 feet of the Eagle Ford and the basal 3 feet of the Austin chalk. An excellent section of the Austin-Eagle Ford unconform­able contact, the upper shale and the middle flags was reached in excavations {March, 1932) on the west part of The University of Texas campus. The basal shale {Pepper?) was excellently exposed in building and sewer excavations at 19th and Nueces Streets, Austin. A diversion cut on Bouldin Creek, on the Barton Springs road in South Austin, exposes the Eagle Ford and its contact with the Buda. In Bear Creek west of Manchaca the entire Eagle Ford with both contacts is exposed. The formation is recorded as 24 to 45 feet thick in wells, and 42 to 47 feet on the surface, in Travis County. On the Blanco River southwest of Kyle the upper Eagle Ford and its contact with the Austin are well exposed. Southwest Texas.-The interfingering transition from the black shale facies to the Boquillas {Val Verde) flag facies occurs be­tween Uvalde and Brackettville. In Val Verde and . Terrell coun­ties the Boquillas is extensively exposed and is not sharply defined from the overlying Austin flaggy limestone. In Brewster and west­ern Pecos counties the Boquillas overlies the Buda concordantly and with a wavy contact. This is well exposed around the outer part of the Solitario rim, and at the north end of the Davis Moun­tains. At Chispa Summit the Eagle Ford {Mancos) clays and thin flags overlie the Buda, apparently concordantly. At Cerro de Muleros west of El Paso, 350 feet of shales and flags with lno­ceramus labiatus are recorded. From the northern · and eastern slopes of Gomez Peak, northern Jeff Davis County, Mr. A. H. Dunlap reports an Eagle Ford section consisting of (a) about 250 to 300 feet of beds, the base in undulat­ing contact with the Buda limestone; their lower half consists of hard, ringing, thin-bedded, salmon colored Boquillas flagstones, their upper half of alternating flagstones and yellow shales which contain near the top Scaphites, Prionotropis, a three-foot ammonite, lnoceramus cf. labiatus and other fossils; and (b) ahout 240 feet of yellow to whitish·yellow clay. He reports the presence, at the Texas Pacific dam in Little Aguja canyon, northern Davis Moun· tains, of-ahout 15 feet of sand of undetermined age, underlying what appears to he basal Eagle Ford shales. Paleontology and zonation.-At present the Eagle Ford can he divided only tentatively into paleontological zones, which are sum· marized as follows: Austin chalk -----1mconfomuty----­ 8. Alecu·yonia lugubris zone -Prionocyclus-Prionotropis zone 6. Coilopoceras zone 5. Romaniceras-Metoicoceras whitei zone 4. _ eocardioceras zone· (Pseudaspidoceras) 3. Eucalycoceras bentonianum zone 2. Acantboceras wintoni zone l. Acanthoceras tarrantense zone -----unconformity·----­ A generally valid zonation, hased on expansion and rectification of these zones, requires further detailed collections and comparisons hetween numerous localities. Red River counties.-Shumard (1464a) Cragin (324), Taff (1575), Hyatt (867) and others record the following fossil partí· tion in Grayson County: Feet 7. Alectryonia lugubris (bellaplicata) zone: shell aggregates, blue clays, shelly marl with sand and phosphatic grains; AmmoniJ;es meekianus Shumard, Ostrea alífera Cragin and its var. pediformis, Alectryo1ua llV­gubris, Ostrea congesta, Ca.rdium choctawense:, Corbula graysonensis; Post Oak Creek, near Sherman, and elsewhere; thickness, abouL______ 75+ 6. Prionotropis zone; blue-black shale with large ironstone concre­ tions and septaria; Prionotropis graysonensis, Scaphites vermiculus, Me­ toicocceras swalloui, Alectryonia bellaplicata, Corbula tuomeyi, Venus sublamellosu.s; 4--4\6 miles north of Sherman; creek northeast of Sher­ man Junction; thickness________________________ 200+ 4. M etengonoceras dumbli, .Metoicoceras swallovi, "Ancyloceras" an­ nulatus Shumard, Baculites gracilis; Cytherell! lamarensis, Turbinopsis septariana, _feritopsis biangulatus, atica striaticostata Cragin, Fusus graysonensis Cragin, Anchura modesta Cragin; 4 miles east of Wbites­ boro; estimated thickness____________________________ 300+ The Geology of Texas-Mesozoic Systems 433 2. Blue-hlack, gypsiferous clay with sand streaks and small concre­tions; thickness ahout-----------------------------------------------------50--­ ln Fannin and Lamar counties the Eagle Ford contains Metoicoceras swaJ. lovi, Prionotropis graysonensis, Amm. inequiplicatus, gastropods and pelecypods. Tarrant-DaUas counties.-The Eagle Ford section, as studied by Tafi (1574, 1575), Cummins, Winton, Scott (1391), Moreman (1141), the writer and others suggests the following zonation: Feet 7. Alectryonia luguhris zone: shale with sand, shells, bones, fish teeth, and A. luguhris (Comad) in abundance; White Rock escarpment_ _ 15 6. Prionotropis zone: shale and thin flaggy limestone; Prionotropis, Prionocyclus, Scaphites vermiculus Shumard ; Arcadia Park_______ 60 5. Coilopoceras :rone: shales; C. afl. eaglefordense; ahout ____ 75 4. Romaniceras-Metoicoceras whitei zone: 3 miles NW of Midlothian 50 3. Neocardioceras :rone: shales; Keenan's Crossing (Neocardioceras septem-seriatim holotype; Metengonoceras dumbli), Horton's Mili, Cali­fornia Crossing; thickness uncertain, possibly_ _____ ______ 50 2. Eucal,ycoceras bentoniarwm-Borissiakoceras zone: shales; Boris­siakoceras n. sp., Metoicoce:ras irwini (Cottonwood Creek); Bor. n. sp., Eucalycoceras n. sp. (Walnut Creek); Euca/,ycoceras bentonianum (Cra­gin), Metengonoceras dumbli (Cragin), Proplacenticeras syrta/,e var. cumminsi (Cragin), Baculites gracilis Shumard, "Ancyloceras" annula­tum Shumard, lrwceramus (Hackherry Creek) ; ahout_______ _ 90 Zone undetermined: carhonaceous shales-, with Acan.thoceras (Eucaly­coceras?) wintoni Adkins, Ammonites inequiplicatus Shumard; ahout__ 145 L Acanthoceras zone; shale, sandstone; Tarrant station; ahout____ 15 The Acanthoceras zone is unconformably underlain by shelly Woodbine sandstone containing Ostrea soleniscus Meek, Ostrea carica Cragin, Exogyra columbella Meek, Arca tramitensis Cragin, Neritopsis tramitensis Cragin, fish teeth, and many other fossils. Wells in Dallas show a thickness of 495 feet of Eagle Ford. Western Ellis County (Britton-Midlothian-Maypearl) .-South of the preceding section and in the same strike, along the White Rock escarpment, is a well-developed section of Eagle Ford, studied by Moreman (1141) and others. A more detailed zonation, with de­scriptions of numerous species, will be published by Moreman. Feet 8. Transition zone: hlue marl, fish teeth_ 5 6. Prionotropis zone: shales and thin flaggy limestones; ahouL__ 100 4. Metoicoceras whitei zone: shales with M. whitei, M. whitei var., Neocardioceras septem-seriatim (Cragin), Romaniceras sp., Proplacen­ticeras pseudoplacenta and its var. occidenta/,e (Hyatt), Scaphites afl. warreni, Baculites gracilis Shumard, Allocrioceras pariense (White) , lnoceramus fra:gilis, Lunatia, Fasciola:ria, fish remains; about__________________ 100 2. Eucalycoceras zone; shales with Metoicoceras irwini Moreman (= aff. pontierí), Metoicoceras sp. A. (Moreman), Pachydiscus sp. A. Moreman, Placenticeras sp.; basally sorne limy flags; about____________________ 150 Zone undetermined; basal black shales; about______________________________________ 125 l. Acanthoceras zone; limestone with A. ta~rantense (Adkjns) , Me­teng. planum Hyatt, Exogyra columbella Meek; Mountain Creek; about 15 -----unconformity·----­ Woodbine (Lewisville beds) : shell aggregate of Ostrea soleniscus, fish re­mains and numerous Lewisville fossils. Waco section.-The most reliable wells near Waco show about 200 feet of Eagle Ford; on the Bosque escarpment there is about 175 feet. The following fossils are known in this section: Feet 3. Upper shales with bentonite seams; Prionotropis (normal and mi­cromorph), lnoceramus spp., Pachydiscus, Metaptychoceras n. sp., Allo­crioceras n. sp., Hemiaster sp., pelecypods and gastro•pods; Clidastes, lchthyodectes, Xiphactinus, Protosphyraena, Oxyrhina, plesiosaurs; about -------------------------------------------------------------------------------100 2. Middle flags; Mantelliceras sellardsi Adkins, Eucalycoceras sp.., Scaphites aff. aequalis, l noceramus, Ostrea., Pecten; about______________ ______ 35 l. Pepper clays (?) : Basal shale ; fish (Portheus?), turtle (Protostega gigas Cope), mososaurs and other vertebrata; lnoceramus, Cardium, Tur­ritella, Arca:; exposed at spillway below dam, Bosque Bridge, South Bosque and Bosque escarpment; about_______________________________________ 40 Bell County.-Between Belton and Temple, and elsewhere in the county, the following summarized section occurs: Feet 3. Upper shales with bentonite seams; lnoceramus; about_________________ 55 2. Middle flags (Aca:nthoce ras zone) ; Acanthoceras bellense, A. stephensoni, A . lonsdalei, Acanthoceras (severa! other s.pecies), Eucaly­coceras leonense, Metacalyco·ceras spp., Heliococeras pariense White, An­cyfoceras annulatum, Turrilites . aff. costatus Sowerby, T. aff. desnoyersi d'Orbigny, Turrilites spp., lnoceramus /ragilis, pelecypods, gastropods, reptilia, fishes, carbonized wood; about______ __ _______________________________________ 5 l. Pepper clay&: Basal lustrous black shale; Anchura, Y oldia, other pelecypods; the age of this shale is not entirely clear; about____________ 50 The basal shale rests unconformably on Del Rio (Grayson) at most places, on Buda at a few places. Travis County.-At the outcrop near Austin there is 35 to 40 feet of Eagle Ford, in wells 24 to 45 feet, counting the basal black shale. The Geolo'gy of Texas-Mesozoic Systems 435 The following is a generalized section, compiled from Bear Creek near Manchaca, Bouldin Creek, excavations on The University of Texas campus, Watters Park, Round Rock, and the San Gabriel River south of Weir: TARRANT­WACO­DALLAS COS TEMPLE AUSTIN GRAYSON MAIN ST Fig. 25. Condensed wne in Eagle Ford group in south-central Texas. Eagle Ford zones: 8. Alectryonia lugubris 7. Prionotropis 6. Coiloj:Joceras 5. Romaniceras-Metoicoceras 4. ~eocardioceras 3. Eucalycoceras bentonianum 2. Acanthoceras wintoni l. Acanthoceras tarrantense Woodbine zones: IV. Acanthoceras n. sp. 111. Aguilera cumminsi-Ostrea soleniscus 11. Plants l. Euhystrichoceras ?-desmoceratids (indet). Buda markers: Budaiceras, P ecten roemeri Grayson markers: Graysonites n. gen., Adkinsia, Gryphaea mucronata Main Street markers: Stoliczkaia sp., Turrilites brazoensis Feet (D) 8, 7, 6, 5, 4. Condensed zone;4si¡. Eagle Ford clay contaii:iing angular boulders up to 18 inches long of both chalky limestone and laminated Eagle Ford limestone, corroded by ground water but not 4B•Omiuion is a submarine condition in wbich neither sedimentation nor removal of 1edi­ment1 occuns. The zonal fossils representing severa} sncee11ive time unita are preserved along the omission-surface, where they are found commingled in a single atratum 10 that the euc· ce111ion of the foesil zones of different agea is unrecognizable. Thie mixture of foseils of 436 The University of Texas Bulletin No. 3232 rolled; sorne phosphatic pebbles; Alectryonia lugubris (Conrad), Pri­onocyclus sp., Prionotropis spp., Coilopoceras chispaense:, C. eagleford­ense, C. n. sp., Romaniceras sp., Pseudaspidoceras 2 spp., Proplacenti­ceras (?) n. sp,, N e:ocardioce:ras spp., Scaphites n. sp·., pelecypods, fish teeth; about -------------------------------------------------------------------------1.5 (C) Zone undetermined; laminated shale with thin bentonite seams, a 4-10 inch bentonite seam at base; color yellow from ground water; lnoceramus spp., pelecypods, fish teeth; about____________________________________________ 16.5 (B) 3, l. Bla.ck limestone flags and shale; Exogyra columbella, Man­telliceras n. sp. (compressed), Acanthoceras sp. (strongly cornute), Eu­calycoceras leonense Adkins, Austiniceras n. sp., Eucalycoceras benton­ianum Cragin (?) ; M etoicoceras sp. (?) ;49 plants, fish; about______________ 12 ------1inconformity·-----­ (A) Pepper bhale (?): Basal lustrous black shale; Exogyra colum­ bella (?), gastropods, pelecypods, Ammobaculites; about ---------------------15 ------unconformity·------ Buda limestone. The thin Uppermost boulder bed of the Eagle Ford at Austin is here interpreted as a condensed zone, representing the upper five zones of the Eagle Ford in north Texas. If this boulder bed were a product of subaerial erosion, it would show (a) miscellaneous debris from various formations on the erosion surface, and (b) great wear of the soft fossils. Neither of these features appears to be present. Trans-Pecos Texas.-In Val Verde, Terrell, Brewster, and south­ern Presidio counties the Eagle Ford occurs in the Boquillas flag different ages in a single bed is a condensed zone. Thus in the topmost atratum of the Eagle Ford near Austin, apparently ali zones from the Pseudaspidoceras-Neoc.ardioceras zones of the lower Eag1e Ford to the Ostrea lugubris zone at the top of the Eagle Ford are indiscriminately mixed together in a stratum less than 2 feet thick. These featurea are explained in Amold Heim : Ueber submarine Denudation und chemische Sedimente. Ceol. Rundschau, 15: 1-47, 1925. '-9Scott (1391, p. 622) records a specimen of Metoicoceras whitei in float at the top of the Buda on Barton [probably Bouldin] Creek, south Austin. According to the writer's interpre• tation, this would represent !ayer B or C above. Cragin (324, p. 243) record.a Prionotropi1 [?] f.rom immediately above the Buda limestone on the San Gabriel at Towne'e Mill below Weir. Four individuals of Coilopoceras in the University of Bono were collected by George Stolley in 188~1887 from "Barton's [probably Bouldin] Creek, 6 miles von Austin, Texas." On& ti ribbed, the others smooth; one has a complicated suture with tall elements; and the othere have simpler sutures with blunter lobes; two are thin-lenticular, the others fatter. They are probably identical with the severa] species which have been collected by the writer from the uppermost Eagle Ford condensed zone in Travis County. Among the speciea; recently found at Austin is C. colleti Hyatt, the genotype, essentially identical with topotypes from Hyatt's type locality, Carthage, New Mexico, collected by Prof. H. B. Stenzel and kindly donated to the Bureau of Economic Geology. By far the most abundant genus in the condensed zone near Austin is Coilopoceras, then Pseudaspidoceras. The Geology of Texas-Mesozoic Systems 437 facies. A few ammonites, lnoceram:us, fish remains and other fossils have been found; but the formation has not been zoned. In the Chispa Summit area the Eagle Ford equivalents are in the marl facies, here called the Chispa Summit formation. The type locality is in the headwaters of Van Horn Creek on the Johnson and Colquitt ranches, in the neighborhood of Needle Peak (see 20, p. 36, fig. 7). The formation is here around 800 feet thick. It has been zoned as follows (20): 8. Upper thin limestone flags and interhedded marls. Fossils: Prionotropis, Metoicoceras, Scaphites aff. aequalis, belemnites; lrwceramus aff. labiatus; pelecypods. 7. Clays. 6. Coüopoceras zone: Clay with flat calcareous mudstone nodules; Coüo­poceras eaglefordense, C. chispaense, Coüopoceras aff. springeri Hyatt, Ac~ thoceras sp., pyritic micromorphs (Prionotropis, Metaptychoceras), Campto· nectes. 5. Coüopoceras-Romaniceras transition zone: clay with calcareous nodules; Coüopoceras eaglefordense, Romaniceras cumminsi, Metacalycoceras (?) n. sp., micromorphs (Prionotropis) . 4. Interbedded limy flagstones and marl; few fossils. 3. Romaniceras zone: clay with septaria, concretions, conglomerate concre­tions, and nodules; Romaniceras loboense, prohably R. cumminsi, Pseudaspi­doceras (?) chispaense, Prionotropis aff. papalis, a new genus of Vascocerati­dae, Acanthoceras. ·2. Clay with suhordinate thin flags; Metoicoceras, lrwceramus. 1 (b). Pseudaspidoceras zone: Thin limestone flags with some interhedded marl and a band of gray chalk. Pseudaspidoceras aff. foateanum + spp., Metoicoceras, Acanthoceras, Prionotropis aff., hyatti, Allocrioceras pariense White (?), Scaphites. 1 (a). Interhedded limestone flags and marls (Neocardioceras zone): Neo­cardioceras septem-seriatim (Cragin) + sp., "Accmthoceras" coloradoense Hen­derron, Metoicoceras spp., Mantelliceras aff. couloni, Scaphites aff. africanas Perv. + spp., Baculites gracüis, Allocrioceras n. sp., Acanthoceras sp., echi­noids, gastropods. Zone la is interpreted as Upper Cenomanian. It is noteworthy that in the English and French sections the Cenomanian-Turonian boundary is marked by a zone of N eocardioceras and M etoicoceras pontieri ( = aff. irwini Moreman) (see Spath, 1510, table opp. p. 80). Zones lb-2 are considered Lower Turonian (Salmurian); zones 3-8 are considered Upper Turonian. The principal Acantho­ceras zone of the Eagle Ford flags (Tarrant; Upper Cenomanian) was not located at Chispa Summit. Salmurian with the ammonites Fagesia texana Adkins, Thomasites n. sp., Neoptychites n. sp., and a new genus ( = "Hoplitoides mirabilis" Bose, not Perv.), occurs in the Van Horn Mountains 8 miles west of Chispa Summit. In the Terlingua quadrangle the top of the Eagle Ford may be taken as a persistent limestone flag cap rock containing belemnites, Crioceras n. sp., and Scaphites a:ff. vermiculus Shumard (from near Woodlake, Grayson County, but larger). Foraminifera of Eagle Ford Formation~º Haplophragmoides aff. calcula Gaudryina filiformis Berthelin Cushman and Waters *Quinqueloculina stelligera Schlum-Ammobaculites aff. subcretacea berger Cushman and Alexander Trochammina diagonis ( Carsey) *Spiroplectammina terquemi Lenticulina rotulata Lamarck CBerthelin) Marginulina elongata d'Orbigny •verneuilina aff. propinqua H. B. Dentalina communis d'Orbigny Brady Dentalina adolphina d'Orbigny Vaginulina webbervillensis Carsey *Bolivina sp. Vaginulina regina Plummer Entosolenia laevigata (Reuss) Flabellina hebronensis Moreman Globigerina cretacea d'Orbigny Frondicularia cordai Reuss Globigerina voluta White Guembelina globulosa (Ehrenberg) *Hasterigerinella moremani Cushman V entilabrella eggeri Cushman Globotruncana arca (Cushman) Bulimina aff. elegans d'Orbigny Gyroidina depressa (Alth) Bulimina aff. murchisoniana Valvulineria aff. asterigerinoides d'Orbigny Plummer Loxostoma tegulatum (Reuss) • Anomalina eaglefordensis Moreman The following ostracoda are most distinctive of the Eagle Ford: Cythereis eaglefordensis Alexander Cytheropteron n. sp. Alexander Bairdia alexandrina Blake Cythereis n. spp. Alexander Cytherella münsteri (Romer) Ammonites known in Eagle Ford Equivalents in Texas Lytoceratidae: Turrilitidae: Lytoceras (?) n. sp. Tun-ilites aff. costatus Baculitidae: Turrilites aff. desnoyersi Baculites gracilis Shumard Tun-ilites spp. Baculites spp. Engonoceratidae: Scaphitidae: Metengonoceras dumbli (Cragin) Scaphites vermiculus Shumard Metengonoceras spp. Scaphites n. sp. Moreman Prionotrnpidae: Scaphites aff. africanus Perv. P1-io_notropis aff. woolgari Scaphites n. spp. Prionotropis aff. papalis Pi-ionotropis hyatti Stanton Crioceratidae: . Prionotropis graysonensis ( Shu-Crioceras n. sp. mard)Hamitidae: Prionotropis aff. bravaisi (More­Metaptychoceras n. sp. man) !Ofrom aiz: outcrops in Dallas and Denton counties; list by Helen Jeanne Plummer; Hteriak lndicatea species thought to be cbaracteristic of tbe formation. The Geolo'gy of Texas-Mesozoic Systems 439 Prionotropis spp. Prionocyclus spp. N eocardioceras septem-seriatum (Cragin) Neocardioceras n. sp. Moreman N eocardioceras n. sp. (?) Watinoceras (?) aff. colorado· ense. (Henderson) Acanthoceratidae: Mantelliceras sellardsi Adkins Mantelliceras spp. Eucalycoc;eras n. sp. Eucalycoceras bentonianum (Cragin) Eucalycoceras leonense Adkins Eucalycoceras spp. Acanthoceras aff. comutum Acanthoceras stephensoni Adkins Acanthoceras bellense Adkins Acanthoceras lonsdalei Adkins Acanthoceras tarrantense (Adkins) Acanthoceras wintoni Adkins Acanthoceras spp. Romaniceras loboense Adkins Romaniceras cumminsi Adkins Romaniceras aff. deverianum Protacanthoceras (?) sp. Metoicoceratinae: Metoicoceras swallovi (Shumard) Metoicoceras whitei Hyatt Metoicoceras gibbosum Hyatt Metoicoceras irwini Moreman (=aff. pontieri Metoicoceras (?) inequiplicatum (Shumard) Metoicoceras spp. indet. 1\1.ammitidae: Pseudaspidoceras eaglense (Adkins) Pseudaspidoceras aff. armatum Perv. Pseudaspidoceras aff. pedroanum (White) P1;eudaspidoceras aff. footeanum (Stoliczka) Pseudaspidoceras aff. footeanum (Petraschek) Vascoceratidae: Fagesia texana Adkins Fagesia aff. haarmanni Bose Thomasites n. sp, Neoptychites n. sp. Three new genera Coilopoceratidae: Coilopoceras colleti Hyatt Coilopoceras eaglefordense Adkins Coilopoceras chispaense Adkins Coilopoceras n. spp. Coilopoceras aff. springeri Hyatt Placenticeratidae: Proplacenticeras (?) pseudoplacenta Hyatt and var. occidentale Hyatt Proplacenticeras (?) cumminsi (Hyatt) Phlycticrioceratidae: Phlycticrioceras n. spp. Allocrioceras pariense (White) Allocrioceras larvatum ( Conrad) Allocrioceras rotundatum ( Conrad) Allocrioceras n. sp. Not placed: Ancyloceras annulatum Shumard Borissiakoceras 2 n. spp. Other fossils are listed in Adkins, 13, p. 32. AUSTIN GROUP51 Nomenclature.-The name Austin limestone was first used by B. F. Shumard (1463, pp. 583, 585) in 1860 for the limestone typically exposed at Austin, which was located by Shumard cor­rectly above the thinned Eagle Ford (fish bed), but incorrectly below the Comanche Peak formation. Shumard says that the State House and severa! public buildings in Austin were made of the stone. The "Pinto" lime8tone oí Dumble is a synonym. "1Literature.-North·c•ntTal T..,,,,: Alennder, 3lb; HJll, 803; Shuler, 1454; Stepheneou, 1530; Talf, 1575; Bullard, 177; Lahee, 969. South-centTal Te"4S: Adldna, 11, 16; Bill, 803, 808; Vau¡han, 1686; Sellarda, 1402; Liddle, 992; Talf, 1574. Tran1-Peco1 Te"41: Udden, 1625, 1626. PoleontOlogy: BOhm, 126; Heine, 702; Heinz, 703, 703a; Kniker, 947; Lasswitz, 976; Prather, 1256, 1257; Schlüter, 1372; Stanton, 1518; Stephenson, 1540; Adkina, 13 ¡ Roemer, 1331; Ree• oide, 1295a. /tfneou• rock.: Lonsdale, 1009; Ron, 1353. Stratigraphic position and contacts.-East of Sherman a little helow the hase of the typical Austin there is a fish-hed conglom­erate with associated sands and clays ( thicker to the east) and pehhles of phosphate, chert and quartz. Stephenson regards this as evidence of an unconformity, and places the "fish hed con­glomerate" at the hase of th~ Austin chalk. Stephenson has traced Taff's Fish hed conglomerate from the Red River region southward to Hays County. It contains fossil material reworked from the under­lying Eagle Ford, including several kinds of oyster shells and the teeth of several kinds of fish. In Travis and Hays counties small horings extend from the hase of the Austin downward into the Eagle Ford clay to a depth of as muchas 18 inches and these are filled with glauconitic chalk exactly like the basal chalk layer of the overlying Austin (1539, p. 1328). In McLennan County the Austin-Taylor contact is unconformable, and is marked by a thin hut persistent phosphatic conglomerate. At a locality near Bynum, Hill County, the base of the Taylor cuts across bedding planes of the upper Austin chalk. The phosphatic conglomerate at the hase of the Taylor has heen traced across Hill, McLennan and Ellis counties to the Dallas County line, where it apparently dies out. According to Stephenson, a layer containing numerous specimens of lnoce­ramus undulato-plicatus Roemer lies at the top of the exposed Austin chalk at W aco hut 250 feet helow the top at Dallas and well down in the Austin chalk at a. place 6 miles northeast of Austin, showing that the unconformity at W aco represents the removal of at least 250 feet of upper Austin chalk (1539, p. 1330). East of eastern Smith County, Austin rests on Woodbine, and east of Upshur­central Gregg counties where the Woodhine disappears, on Comanche rocks. Facies.-The type Austin is an alternation of white chalky lime­stone and limy marl strata with sorne layers of shelly marl especially near the top. East of Grayson County on the outcrop, clay (Bon­ham) and sand (Blossom) appear. In the East Texas oil fields east of Smith County the Austin is sandy, and in southwestern Arkansas its partial equivalent, the Tokio, contains much sand interhedded with clay. Likewise in the northern Louisiana oil fields it contains sand. Two other intergrading facies occur in west Texas. · From Val Verde-Terrell counties westward to heyond Terlingua, the Austin consists of thin limestone flags, chalkier to the east, more The Geology of Texas-Mesozoic Systems 441 crystalline to the west. Near Terlingua these are thin and are interbedded with much marly material, so as to weather down to flats. To the northwest the fonnation becomes more marly until at Chispa Summit it consists of marl, with thin subordinate amounts of marly and platy limestone flags. This facies is here called the Colquitt formation. Near Pilot Knob, Travis County, the Austin locally occurs in a reef facies, a rather pure white shelly limestone, in part coquina, containing interbedded serpentine at places, with echinoids, cap­rinids, oysters and various other mollusca. Areal Geology.-Eastwards from the eastern line of Grayson County (roughly east of the axis of the Preston anticline) through Fannin, Lamar and Red River counties, the Austin is represented by four equivalents, in ascending order as follows: (1) "Fish bed conglomerate" and associated sands and clays; (2) Ector chalk; (3) Bonham clay; (4) Blossom sand. In the Black Prairie region the Austin is represented by the Austin chalk proper, overlain by the Burditt marl. In Trans-Pecos Texas it is represented by unnamed flags generally similar to the underlying Boquillas but less vividly colored, and farther northwest by an unnamed clay facies. In the Sabinas coal basin (northern Coahuila) a local marginal facies of coarse grits, sands and conglomerates appears. Topography aruJ, vegetation.-In the humid region, where the Austin is composed mostly of limestone ("chalk"), and typically fonns prairies, the central or inner portion of the black land belt, two general topographic types prevail: the canyon topography occurs along streams cutting across the Black Prairie, and the interstream areas are prairie land. lndurated limestone layers pro­duce steep blu:ffs along streams, but the softer strata weather to more rounded forms, and the canyons are not intrenched. The uplands are widely but shallowly dissected by small headwaters, especially on cuesta slopes. The upland type of Austin is most typically shown on top the White Rock escarpment, as in Dallas and Ellis counties, where through-going drainage is eliminated and only small headwaters remain. Here a deep fertile soil is formed, and the topography is flattened, Near large streams, much soil is removed and bare patches of limestone rock may mark hill slopes. The most characteristic soil of the Austin is the "Houston" clay, typically a dark-brown or grayish-brown clay superficially, grading at a foot or more depth into grayish-yellow clay containing fria.ble limy material, which deeper grades into the chalky marl or chalky limestone of the Austin. Where derived from the chalky limestone, the subsoil is a greenish-yellow, chalky, friable clay, grading into soft, white chalky material at depths of less than 3 feet. The dried soil may be crumbly, and in color light or dark ashy gray. The prairie white rock land originally supported a growth of mesquite grass, with occasional post oak, elm and hackberry. The bare Austin chalk, especially on escarpments, is covered with a thicket growth of small trees and shrubs, "cedar" (= juniper), oaks, elm, hackberry, box elder, red bud, honey locust, sumac, mesquite, smilax, prickly pear and bear grass. The main oaks are Quercus breviloca,ta (shin oak) , and Quercus texana. In the semi-arid region the Austin group is largely of a soft facies. At most places it consists of thin interbedded marls and flags and forms flats. In the Chispa Summit district, it is largely marls, and forms miniature bad lands. NORTHEASTERN TEXAS From Fannin County eastwards on the outcrop, the Austin con­sists of the four units described below. Southwards from Fannin County, these lose their identity, and the group consists of typical Austin limestone overlain by Burditt chalk marl. FISH BED CONGLOMERATE This bed was described by TafI from eastern Grayson County (1575, p. 303). On Squirrel Creek one mile below Trinity school house, at a level 10 feet below the top of the Eagle Ford, there is a 20-inch stratum of conglomerate or coarse grit containing fish teeth and a few Ostrea lugubris. On Choctaw Creek 1 ~ miles above the Sherman-Van Alstyne road, the conglomerate, 2.5 feet thick, is located 10 feet below the top of the Eagle Ford and it and the underlying Eagle Ford have many O. lugubris. In Post Oak Creek near Sherman, the 2-foot conglomerate is overlain by 20 . feet of Eagle Ford shale. Near Ector and Ravenna the conglomerate is 35 feet below the base of the Austin chalk, the intervening material heing mostly light greenish calcareous shaly and somewhat sandy clay, containing in the lower 10 feet lenses of sand and sandstone. The Geology o/ Texas-Mesozoic Systems 443 About 3 miles south of Ravenna the indurated conglomerate, about 10 inches thick, consists of coarse calcareous sand, grayish and brownish phosphatic pebbles, a few pebbles of quartz and chert, and scattered shark teeth (1530, p. 149). ECTOR CHALK This member was named by Stephenson in 1919 (1530, p. 149). It is the basalmost member having the chalk facies, in this section. From Dallas northwards the Austin chalk has thickened consider­ably, and in the Sherman-Leonard section in southwestern Fannin County its top includes chalk of Taylor age perhaps continuous eastward with the Gober chalk. East of the axis of the Preston anticline the Austin portion of the chalk changes facies, becoming the Bonham clay, except that its base retains the chalk facies and extends from a point south of Ector northeastwards to near lvanhoe, Fannin County. This is the Ector chalk member, 50 feet or less thick near Ector. It is underlain by the shaly clay, thin sands and fish bed conglomerate previously mentioned. The shaly clay grades into the chalk through a transition zone only about one foot thick. The easternmost known locality of the Ector (1530, p. 150) is on the old Bonham-Ravenna road about 1Y2 miles southeast of Ravenna. The member contains Gryphaea aucella Roemer and "Radiolites" austinensis Roemer. BONHAM CLAY Southwest of Bonham the thick central portion of the Austin chalk changes in a northeast direction into the Bonham clay. lt was named by Stephenson (1534, p. 8) in 1927, the type locality being at small exposures a short distance north of Bonham, Fannin County, Texas. It is a greenish-gray waxy clay, weathering yel­lowish green, about 400 feet thick. A little above the middle there is a stratum of calcareous and strongly glauconitic clay with frag­ments of /noceramus large species, Ostrea congesta Conrad and Ostrea plumosa Morton, which Stephenson considers the westward extension of the Blossom sand. To a certain extent the transition from Austin chalk to Bonham clay has been observed in Grayson County east of Sherman. In the area between Luella, Bells and Whitewright, the basal half of the Austin is largely impure argil­ laceous chalk and chalky clay, and as far west as Luella, highly argillaceous, slightly bituminous shaly chalk or chalky clay. The Bonham clay is mapped eastward, across Fannin, Lamar and Red River counties, to Red River north of Clarksville, between Pecan Bayou and Silver City. In southern McCurtain County, Oklahoma, and in southwestern Arkansas the same member is called the Tokio. The Bonham clay has been traced as a narrow strip through southern Grayson and northern Collin counties as far south as McKinney ( Alexander and Smith, 3lb) . BLOSSOM SAND This sand, first called by Veatch (1691, p. 25) "sub·Clarksville" sand from wells near Clarksville, was named Blossom by Gordon (609, p. 19), who correlated it with the sandy upper portion of the Eagle Ford at Sherman. The type locality is at Blossom, eastern Lamar County. The upper part of the Bonham clay about halfway between Ector and Randolph, southwestern Fannin County, is calcareous and chalky and eastwards is distinctly glauconitic; this develops into brown, sandy, ferruginous glauconitic beds interlaminated with thin clay beds, outcropping as a sandy belt severa! miles wide. The Blossom outcrop passes eastward across central Fannin, Lamar and Red River counties, through Paris, Blossom, Detroit and Bagwell, and ending at the edge of Red River valley near the mouth of Pecan Bayou. Stephenson states that the fossils from the Blossom indicate the equivalence of the Blossom with the upper part, perhaps the upper half, of the type Austin near Austin. At least 11 species are common to the type Austin, and the following indicate synchroneity with the upper part of the type Austin: lnoceramus aff. /. deformis Meek, Ostrea congesta Conrad, Ostrea aff. O. diluviana Linné, Gryphaea aucella Roemer, Exogyra ponderosa Roemer, Liopistha elegantula (Roemer)?, and Baculites asper Morton. No Eagle Ford species were found. The cephalopoda listed are: Nautilus sp., "Hamites" sp., Baculites asper Morton, Placenticeras sp., and Prionotropis?. BLACK PRAIRIE REGION TYPICAL Al]STIN CHALK From eastern Grayson County southwards, the Austin is in gen­eral typical. lt forms a wide, prominent and important outcrop, the substratum of a part of the fertile black land helt (Black The Geology of Texas-Mesozoic Systems 445 Prairie) devoted largely to cotton raising. On it are located many important towns: Sherman, McKinney, Dallas, Waxahachie, Mid­lothian, Waco, Temple, Austin and San Antonio. The total chalk in eastern Grayson County is prohahly as much as 1000 feet thick; near Dallas 700 feet; at Corsicana 425 feet; 480 feet in the Powell field and 440 feet in the Mexia-Richland area (969, p. 331); near Groesheck, southern Limestone County, 350 feet; in Bell County 550-604 feet; in Milam County ahout 500 feet; in Williamson County, 325-342 feet; in Travis County, ahout 420 feet (275-400 in wells); in Medina County, ahout 350 feet; in eastern Uvalde County, 350 feet; western Uvalde County, ahout 350 feet; in eastern Uvalde County, 350 feet; western¡ Uvalde County, 550 feet [F. M. Getzendaner, personal communication]. Although the literature contains records of 350 to 400 feet of Austin in Bexar County, many geologists now consider that these thicknesses include some rocks of Taylor age. The Austin chalk is stated to be 110 feet thick in eastern Bexar County [L. W. MacNaughton, personal communication], and the 443 feet of Austin recorded (888) in southwestern Bexar County is stated to include the Anacacho. Likewise it is unknown how much, if any, of the upper part of the type Austin chalk in Travis County should be separated from the true Austin. These questions require extensive zonal work and a paleontological redefinition of the type sections. At the type locality the lower two-thirds of Austin consists of irregular strata of variable thickness, from thin-hedded to massive, and with often indefinite limits, generally alternately harder and softer. They are composed of a gray-white chalky lirnestone in the harder layers, and a dark hlue or hlackish marly limestone or limy marl weathering dead white or light gray, and in texture unevenly flaky or laminated. A few of the lirnestones are indurated, sorne are shelly. Sorne contain rnuch dehris of oysters, inocerami and other shells. At certain levels considerable glauconite, dispersed as small specks, occurs; the formation contains imhedded halls, cylinders and irregular botryoidal rnasses of pyrite with radiating interna} structure; and locally veins, seams and joint cracks filled with calcite. In youthful strearn cuts vertical clifls of alterpately projecting and receding strata occur; on hillsides and upland prairies a rounded topography prevails. On many patches of upland, headwater erosion is sufficiently rapid to strip the outcrop of soil. Generally harder and softer ledges are not topographically well expressed. The upper part of the formation has considerable cal­careous marl, in beds up to 30 feet thick, and sorne very shelly marl ( with Exogyra), generally in beds 5 feet or less thick. Such a marl in northern Travis County seems to be characterized by the presence of Exogyra tigrina Stephenson and "Ostrea" centerensis Stephenson, and contains other species listed below. A notable feature of this level is the presence of a wide range and variety of Exogyra, prob­ably referable to severa! species. The Austin consists of heds of impure chalky limestone, containing 85 per cent or more of calcium carbonate, interstratified with heds of softer marl. lt is usually of an earthy texture, free from grit, and on fresh exposure softer, so that it can he cut with a hand saw, hut on exposure more indurated. In thin slices the material shows calcite crystals, particles of amorphous calcite, finely crystalline calcareous material, foraminiferan shells and fragments, fragments of the prismatic !ayer of ln.oceramus often in great ahundance, dehris of pelecypods, gastropods, echinoids, and other organic fragments. The ma­terial has the typical crystalline structure of limestone. Some slices show ahundant glauconite specks; sorne show a sparse to medium amount of "spherical hodies" (see page 365); and sorne show a finely crystalline texture almost devoid of organic material. Typical analyses show calcium carbonate 82 per cent; silica and insoluble silicates 11 per cent; ferric oxide and alumina 3 per cent; magnesia 1 per cent. The water-filled subterranean chalky limestone is usually of a blackish-blue to bluish-gray color, as in most cores. The air-dried material is generally glaring white and of a matte texture. The dried marls may be more blackish or bluish. They weather mostly into abrupt slopes capped by harder ledges. Some ledges become indurated and crystalline; others, less crystalline, weather into irregular small conchoidal flakes with an earthy fracture. The harder strata have an irregular, ragged conchoidal fracture. Locally in the more massive layers, there occurs a large conchoidal fl.aking, superficially resembling exfoliation. On prolonged disintegration, the Austin weathers into a black residual soil, characteristic of the Black Lands belt of east-central Texas. Locally as near Pilot Knob, the Austin is metamorphosed, and occurs as a porous, redeposited and recrystallized limestone in medium beds, soft enough on fresh exposure to be sawed, nearly pure, and producing an excellent building stone. The German Lutheran Church just north of the Capitol at Austin is built of this stone. Formerly the ordinary The Geology of Texas-Mesozoic Systems 447 Austin was somewhat used as a building stone, but its softness, marly partings and iron stain make it less desirable than other stones available in central Texas. · The outcrop covers the southeastern one-fourth or more of Grayson County. ~ly lime is more prominent in the lower half of the formation, and medium bedded to thick massive chafky lime­stone in the upper half. In Dallas County the base of the chalk capping soft upper Eagle Ford shales, clays and flags, forros the prominent west-facing White Rock escarpment which proceeds southwards to the Brazos. It is well exposed in road cuts and cement plants on the Fort Worth road about 5 miles west of Dallas. In the quarry of the Texas Portland Cement Company 3 miles west of Dallas, the base of .the Austin chalk, just above the Eagle Ford contact, is marked by a layer of phosphatic pebbles (1530, p. 148. arid PI. XXVII-A). The basal part, 150 feet of the formation, con­sists of heavy-bedded, massive chalk layers separated by thin shaly layers, the most resistant beds heing contained in the basalmost 50 feet (1454, p. 19). The basal part contains an abundance of nodular, spherical or cylindrical masses of pyrite. The middle part, ahout 250 feet thick, has fewer massive layers, and is characterized by thick, and often indurated shaly layers which show ~ fine lamination. This part does not show in stream cuts as marked expression of projecting and receding layers as does the basal part. The uppermost part contains more shaly limestone and less chalk. The colors are predominantly blue and yellow. Some sandy strata occur. At the Austin-Taylor boundary, there is a sharp transition from massive flaggy chalk ( containing "large ammonites,'' most of them Parapuzosia) to gray shale, some of it calcareous. In the W aco region the basal chalk is well exposed in Cameron Park. Here it consists of medium to thick massively bedded strata with some alternating receding ledges. By undercutting of Bosque River large blocks fall down the slopes and disintegrate. ' Flaking and exfoliation are extensive. In the cuts of Brazos River aci'oss the Austin chalk outcrop, considerable small scale faulting, with the development of V-and A-shaped grabens and horsts, is present. Such local faulting occurs in White Rock Creek near the Harring­ton well. The base of the chalk, and locally the. hard Eagle Ford flags, form the crest of the west-facing Bosque escarpment across McLen­nan County. The Bosque is deflected parallel to this scarp and follows it northward to the point where the Brazos cuts through the scarp. Along the scarp, there is considerable faulting in discon­nected lines. The medial part of the chalk consists of medium hedded chalky limestone softer marly layers, weathering white. The Austin-Taylor contact occurs in and near the Baylor University Campus. Here the topmost chalk stratum is a massive chalky lime­stone containing lnoceramus undulato-plicatus and other species, and is followed with a sharp lithological break by hlue-hlack Taylor shale. Stephenson considers that ahout the upper 250 feet of chalk is here absent by suhsequent erosion. The top of the chalk occurs in severa! creeks just east of the Waco-Austin highway. In these creeks Dr. Pace has demonstrated a persistent line of faulting, possihly the eastern limit of the Balcones fault zone in this area. Southward from W aco, the typical hard Austin chalk is overlain by a chalk marl of variable thickness, generally referred to the Taylor because of its foraminifera. In or near the hase of this marl at many localities, large ammonites of the genera Parapachydiscus . and Parapuzosia occur, and their zone of ahundance marks approxi­mately the top of the Austin chalk. Unfortunately their exact zonation has not yet been, puhlished. They occur in severa! localities southwest of Rohinson and Rosenthal, and east of Temple, west of Holland in the hranches of Darr's Creek, north of Austin in Big and Little W alnut creeks, on the Rio Grande at Tequesquite Creek between Del Rio and Eagle Pass, and near San Carlos, Coahuila. Sorne of these "cart-wheel" species reach large size; two of them have heen described from Tequesquite Creek by Scott and Moore. The eastern horder of the chalk is exposed near Garland, east of a line hetween W aco and Eddy, in Deer Creek, in northern Bell county near Little Flock Church¡ east of Temple, in various creeks west of Holland, in Brushy Creek south of Hutto, and in various creeks in Travis County. In San Antonio the excavations in Brackenridge Park represent the Austin chalk at levels hetween 100 and 150 feet ahove the base. The rock is evenly hedded in strata of from six inches to severa! feet in thickness . . It is light gray, tinged with yellow. Oxidized pyrite nodules are present. Near the hase of the quarry, a layer The Geology of Texas-Mesozoic Systems 449 rich in Gryphaea shells occurs. In this county the upper 200 feet of the Austin is a soft bluish calcareous clay or mud. In these beds Stephenson found Scaphites sp., Placenticeras sp., and a large Bacu· lites. The Austin in Medina County (992, pp. 46-48) consists of alternations of soft chalky limestones and marls, argillaceous shales, or clays. Near the top the formation is mostly chalky limestone. The basal half of the Austin as far west as Hondo River contains ledges which are highly glauconitic. The upper part especially has vertical cylindrical concretions of pyrite with radiating structure. The basal 75 feet is quite highly indurated and lithologically some­what resembles the Buda, but lacks the calcite veins characteristic of that formation. At a level about 275 above the base there is a layer of Gryphaea aucella shells, about 4 to 5 feet thick, which persists across Medina and Bexar counties, and is possibly the same as the prominent Gryphaea layer above the middle of the formation at Austin. In the Uvalde area the Austin consists of soft, white and yellow chalky limestone and limy marl alternating. Two large exposures are on the east side of Nueces River opposite Soldiers Camp Spring, where the upper 150 feet is exposed; and a basal 200 feet in the high blu:ff on the west side of the Nueces between the Southern Pacific Railroad and the West Nueces. Gryphaea aucella Roemer, lnoceramus a:ff. digitatus Sowerby, and Mortoniceras texanum · (Roemer) are recorded from the Austin in this area. BURDITT MARL52 Nomenclature.-Hill included this chalk marl with the Austin chalk, and stated that the top is transitional to the Taylor. Taff (1574, p. 353) segregated the upper marly lime zone of the Austin chalk, and considered it lithologically transitional to the Taylor marl. This chalk marl is here called Burditt, from Burditt School, Travis County, and the type locality is along Little Walnut Creek downstream from the Austin-Cameron road. Stratigraphy.-Stephenson states that the Taylor in McLennan County unconformably overlies the Austin, and that its base con­tains a phosphatic pebble zone. There appears to be no marked 52Literature.-Areal: Tafl', 1574, p. 353; Adkins and Arick~ 16, p. M; Dane and Stephenaon, 391. Fouils: Stephenson, 1540; Scott and Moore, 1393. break in Travis County, although a prominent layer of phosphatic nodules and fossils occurs in tbe Burditt near the type locality. Areal geology.-ln south-central McLennan County above the solid Austin chalk, tbere are chalk marls sorne of which may be of the same age as the Burditt in Travis County. In Bell County the solid chalk is overlain by a chalk marl which contains many thick­shelled Exogyra, sorne Ostrea centerensis, Parapuzosia, and severa! other fossils. This chalk marl outcrops in Deer Creek, tbe head· waters of Little Elm Creek, in Cottonwood Creek, and in tbe branches of Darr's Creek west of Holland. Only about 35 feet has been recorded from The Pure Oil Company Hill core test west of Rogers, but it seems to be tbicker on the outcrop. At many places in tbis zone in McLennan, Bell, and Travis counties large Parapuzosia occur, and seem to be distinctive of the level. Taff records the zone from the high bluffs on San Gabriel River, between 1 and 2 miles below Jonah. Lithologically it is transi­tional to tbe Austin cbalk. At least 20 feet of marly, chalky lime occurs, interbedded with marl, and with sorne thin seams of in· durated sandy marl. Taff records that tbis marl contains "large Exogyra ponderosa, an oyster resembling O. subovata, and a small narrow-beaked oyster." A sandy flagstone layer above the marly lime is regarded by T aff as tbe top of the Austin. At the type locality on Little W alnut Creek about 5 niiles north· east of Austin, the Burditt marl is about 40 feet thick. It is a light­gray, somewhat shelly, calcareous clay overlying tbe hard chalk. Several species or varieties of Exogyra (laeviuscula?, ponderosa, tigrina, and costate, subcostate, imbricate, spinose, and subcancel· late kinds), cart-wheel ammonites (mostly Parapuzosia), Mortoni­ceras, Glyptoxoceras, Nautilus (Eutrephoceras) and "Ostred' cen­terensis occur here. At the crossing of the new Del Rio-Eagle Pass road over Teques­quite Creek, Exogyra tigrina and various large ammonites including Parapuzosia similar to those in the Burditt marl occur in tbe lime­stone. At localities between San Carlos and El Moral, Coahuila, exceptionally large ammonites occur at this level. A soft, thin member at the top of the Austin chalk in Medina and Bexar counties is likely equivalent to the Burditt. The Geology of Texas-Mesozoic Systems 451 This unit is distinguishable lithologically from McLennan County probably to Medina County. Paleontologically it is approximately the zone of large cart-wheel ammonites (Parapuzosia). Paleontology.-This unit is the zone of abundance of Parapuzosia sp. and the oysters Exogyra tigrina Stephenson, Exogyra n. sp. ( called the "Chalk Ponderosa"), and "Ostrea" centerensis Stephen­son. In addition it contains fossils of undetermined range: Nautilus sp., Mortonicerll$ sp., a pachydiscid, Neancycloceras?, Baculites, Exogyra ponderosa, E. laeviuscula?, and severa! other mollusca. The foraminiferal fauna includes a large proportion of species common to Austin and Taylor, and apparently a few Austin markers, accord­ing to Mrs. Helen Jeanne Plummer. TRANS-PECOS TEXAS West of the Pecos, the Austin outcrops in four general areas. In Terrell County there is a considerable area of Austin chalk in thin to medium bedded white chalky limestone ledges along the Shumla-Dryden highway. These beds, perhaps 200 feet remaining, contain typical lnoceramus and other fossils. In Brewster County, in the Chisos and Terlingua quadrangles the Austin is irregularly exposed, and forms the lower part of Udden's Terlingua formation. The Austin locally may be considered bound­ed below by a widespread caprock of siliceous limestone in medium or thin-bedded flags, containing Crioceras n. sp. ( with short spines), a belemnite, one or two species of Scaphites, and sorne unidentified discoidal ammonites. It outcrops on the hill north of No. 16 head shaft of the Chisos Mining Company at Terlingua, at the south end of Grace Canyon, at many places between Terlingua and Hen Egg Mountain, on the north and west slopes of Mariscal Mountain, and elsewhere. The Austin extends up to and grades into typical Taylor day. In lithology it is entirely different from type Austin, but somewhat similar to Val Verde or Boquillas flags. It consists of thin to medium bedded, laminated, slightly shaly limestone flags, blackish-blue to gray interiorly, weathering to whitish-gray in the more calcareous layers, blackish-blue in the m?re shaly and car­bonaceous layers, brittle, jointed vertically, and breaking into .diamond-shaped blocks of various sizes or in more indurated flags weathering to large, hard, ringing slabs. Near the top there is an alternation of softer shaly and harder limy strata, which on domes weather to circular benches with low infacing cuesta faces and long outdipping back slopes. The formation is less resistant, and forms less prominent hills, than the underlying Boquillas flags (Eagle Ford); it is more resistant than the T~ylor, which weathers to clay flats and slides, bad lands and outlier topography. Among the fossils are: M ortoniceras severa! species, Baculites, lnoceramus subquadratus Schlüter, lnoceramus several spec;ies, Durania cf. austinensis (Roemer), and others. A notable area of Austin is in the southeastern part of the Chisos quadrangle along the Río Grande between San Vicente and the mouth of Tornillo Creek, where numerous lnoceramus cf. digitatus Sowerby occur. In the Tierra Vieja, Van Horn and Eagle Moun­tains, Austin formation outcrops. Between Chispa Summit and the abandoned San Carlos coal mine, it is in almost entirely a clay facies, with small intercalated bodies of thin limestone flags. This formation, about 1200 feet thick, bounded below by the Chispa Summit (Eagle Ford) and above by Taylor clays, is here called the Colquitt formation. The type locality is on the Colquitt ranch below Chispa Summit, western Jefl Davis County. In northern Brewster and western Pecos counties, Austin chalky limestone occurs on the east slope of the Davis Mountains beneath the Taylor clay. Paleontology.-But little progress has been made toward a zona· tion of the Austin chalk and its equivalents. The following are sorne fossils from the formation with their probable ranges. The earliest Mortoniceras52~ occur in the Austin; the genus is repre­sented by a complicated, as yet unpublished, flowering of species as in the W ashita genus Pervinquieria. M. minutum Lasswitz is com· mon; M. quattuornodosum Lasswitz and M. texanum (Roemer} are rare. The rudistids Durania and Sauvagesw are common in Austin and Taylor. lnoceramus subquadratus Schlüter ( often misnamed l. crippsi) is perhaps the commonest Chalk lnoceramus. A rarer tall form is /. subquadratus var. austinensis Heinz (703a). Prac­tically typical /. digitatus Sowerby occurs in the Big Bend. l. un· dulato-plicatus Róemer characterizes the upper part of the Austin 5.hThe ammonite genus Mortoniceras as · applied to Austin chalk and higber epecies has been renamed Te~anites by Spath (15llb), but for the convenience of readers the older name­i1 retained in this discussion. The Geolagy of Texas~Mesozoic Systems 453 chalk, but its total range is unknown. At many levels both basal and upper, forros like Haploscapha grandis Conrad and H. niobra­rensis Logan occur. Other rather characteristic species are Pecten bensoni Kniker, Spondylus guadalupae Roemer, Liopistha elegantula (Roemer), Gryphaea aucella Roemer, Hemiaster texanus (Roemer), Exogyra laeviuscula Roemer, Exogyra n. sp. Bose (so-called "Chalk Ponderosa," practically confined to the Austin chalk marl at the top of the formation), Exogyra tigrina Stephenson, "Ostrea" center· ensis Stephenson, and others. In a lowermost portio~ in Travis County, no Mortoniceras have yet been reported; to· this portion Iikely belong: Phlycticrioceras n. sp., Parapuzosia a:ff. stobaei, and Coilopoceras austinense Adkins. This portion contains Iarge lnocer­amus (up to 2 feet in diameter) . A middle portion of the chalk contains M ortoniceras minutum Lasswitz, and severa! species similar to it, M. planatum Lasswitz, M. quattuornodosum Lasswitz, M. texanum (Lasswitz), M. aff. emschere, and other species, Parapachydiscus (small sp.), Para­puzosia aff. corbarica, Barroisiceras dentatocarinatum (Roemer), pelecypods and echinoids, and a new ammonite genus closest related to M ortoniceras. Near the top of the chalk there are found: Parapuzosia (Iarge species), Parapachydiscus (Iarge species), "Hamites," Baculites, and other ammonites. The overlying chalk mrarl with Exogyra n. sp. (Chalk Ponderosa), Exogyra tigrina and "Ostrea" centerensis, contains Baculites, "Hamites" and Parapachydiscus (small sp.). The following species are on record from western Texas: (a) probably from the basal Austin equivalents, Coniacian = Spath's Gauthiericeratan age, Peroniceras aff. czornigi (Reeside, from Seco Creek and Tequesquite Creek); P. aff. czornigi, with very prominent alations (Arick; Capote Ranch), P. aff. westphalicum (Reeside; Uvalde County), Gauthiericeras aff. margae (Terlingua area). (b) From upper levels, Lower Santonian = Mortoniceratan, Parapu­zosia americana Scott and Moore, P. bosei Scott and Moore (Te­quesquite Creek). Canadoceras flaccidicostum (Roemer) and Tur­rilites wysogorskii Lasswitz also probably are Austin chalk species. Sorne -0f these ammonites were described by Reeside (1295a). Of the rudistids, Sauvagesia aff. degolyeri Stanton, S. acutocos­tata Adkins, S. aff. belti Stephenson, and Durania austinensis (Roemer) occur in the chalk. Fish and mososaur remains have been found in the Austin chalk. The following are among the most distinctive Austin ostracoda: Cythereis bicornis lsraelsky (upper Austin) Cythereis n. sp. aff. bicornis Alex­ander (lower Austin) Cythere sphenoides (Reuss) (Aus· tin; Taylor) Cytheropteron pedatum Marsson (upper Austin; rare; Gober, com­mon; Pecan Gap; Annona; Sara­toga) , Cytheropteron n. sp. Alexander Cythere n. sp. Alexander Cythereis semiplicata (Reuss) Cythereis ornatissima (Reuss) Cythereis omatissima (Reuss) (up­ per Austin; Gober) Cythereis austinensis Alexander (up­ per Austin) Cytherella parallela (Reuss) Cytherella bulla ta Alexander ( up·per Austin to Pecan Gap) Foram,inifera do not in general afford an exact distinction of Austin from either Eagle Ford or basal Taylor; however, the following foraminifera are found in the Austin chalk in central Texas: Austin Foraminifera53 Ammodiscus incertus (d'Orbigny) Flabellamina rugosa Alexander and Smith Flabellamina clava Alexander and Smith Spiroplectammina anceps (Reuss) Textularia agglutinans d'Orbigny Gaudryina carinata Franke Gaudryina pupoides d'Orbigny Gaudryina stephensoni Cushman Clavulina cf. communis d'Orbigny Heterostomella sp. Trixtaxilina (?) sp. Valvulina inflata Franke Arenobulimina cf. prnsli (Reuss) Dorothia sp. Lenticulina rotulata Lamarck Lenticulina aff. pondi (Cushman) Lenticulina spp. Hemicristellaria trilobata ( d'Orb­ igny) Saracenaria italica Defrance Vaginulina recta Reuss Vaginulina regina Plummer Flabellinella sp. Dentalina alternata (Jones) Dentalina communis d'Orbigny Dentalina granti Plummer Dentalina megapolitana Reuss Dentalina spp. N odosaria affinis Reuss Flabellina interpunctata von der Marck Frondicularia archiaciana d'Orbigny Frondicularia cordai Reuss Frondicularia lanceola Reuss Froudicularia verneuiliana d'Or­ bigny + var. bidentata Cushman Frondicularia spp. Ramulina aculeata (J. Wright) Vitrewebbina cervicornis ( Chapman) Guembelina globulosa (Ehrenberg) *Rectoguembelina texana Cushman *Eouvigerina serrata (Chapman) Pseudouvigerina plummerae Cush­ man Pseudouvigerina sp. Spiroplectoides rosula (Ehrenberg) *Hantkenina multispinata Cushman and Wickenden Bulimina murchisoniana d'Orbigny Loxostoma tegulatum (Reuss) Ellipsonodosaria rotundata (d' Or­ bigny) 88In this list, prepared by Helen Jeanne Plummer, the epecies marked (*) are thought to be moet characteristic of the Austin. The Geology of Texas-Mesozoic Systems 455 Discorbis aff. correcta Carsey Globotruncana arca (Cushman) Gyroidina depressa (Alth) Globotruncana canaliculata (Reuss) Gyroidina globosa (v. Hagenow) Globotruncana fornicata Plummer Glob!gerina cretacea d'Orbigny Anomalina involuta (Reuss) Globigerinella voluta (White) Anomalina ripleyensis W. Berry *Hasterigerinella alexanderi Cushman Anomalina taylorensis Carsey *Hasterigerinella watersi Cushman TAYLOR GROUPH Nomenclature.-When this and many other Texas rock groups were named the conception of type locality did not exist. The name of the formation might be changed, because of preoccupation or convenience, and another name substituted without the notion that the conception of the formation was thereby altered. Towns were few, and often one was selected on the strip of the formation be­cause it was the nearest available name, not because the town stood on a large or significant exposure. 55 lt is here assumed that for certain names of long standing, change of name does not involve change of the type locality, so that the type locality of the Taylor is on the Colorado in Travis County, the type locality of the Buda on Shoal Creek at Austin, the type locality of the Edwards on Bar­ton Creek near Austin. The Taylor, first called the "Blue Bluffs division" (from Blue Bluff of the Colorado, 6 miles east of Austin) in Hill's 1889 papers, was named the Taylor marls by Hill (780, p. 73) in 1891. In many papers it had been called the "Exogyra ponderosa marls" or "clays." It changes facies rapidly along the outcrop across Texas, and the attempt to apply the system of formational and member names to these many types of lithology has resulted in a maze of local names. The following is a partial summary of the names so far applied to Taylor equivalents: 61.Literature.-A.rkansas: Dane, 392; Stepbeoson, 1538; Israelsky, 870. North-central Te%as: Dane, 391; Reiter, 1297; Spo_fford, lSlld; Stephenson, 1530, 1534; Shuler, 1454;,1 Bullard, 177; Lahee, 969; Hill, 103. South-central Te%a&: Hill, 795, 803, 808; Stephenson, 1541; Vaugban, 1685; Baker, 49; Udden, 1625. Trans-Peco1 Texas: Udden, 1626; Vaughan, 1687. Paleontolo11: Adkins, 15; Hyatt, 867; Vaughan, 1687; Stephenson, 1541; Udden, 1627. lgneou.t rock:J: Lona­ dalo, 1009; Roeo. 1353. 1353&; Udden. 1641. Rockwall sandstoBe dike: Burleson. 172, pp. 12&­129; Hill, 803, p. 361; Kelsey, 899b; Paige, 1169; Patton, 1183; Stephenson, 1535; Fohs and Robinson, 543. MR. T. llil:l, peraonal communication. Subdivisions of Taylor Group in Texas McLennrous lime. These sands contain sorne indurated streaks. The basal Nacatoch con­tains breaks of shale or gurnbo. The Arkadelphia fonnation overlies the Nacatoch, forms a seal for it in oil and gas fields, and is the uppermost Cretaceous forrnation 'known in this area. lts approximate recorded thicknesses are: Bellevue, 40 feet; Caddo, 80 to 100 feet; Cotton Valley, 100 feet; Homer, 90 to 125 feet; Pine lsland, 100 feet. NORTHEAST TEXAS The outcrop of the Navarro group between Red River and Brazos River is divisible into three formations, the medial Nacatoch sand being used as a recognizable marker to separate the basal marl from the upper marl. The Nacatoch sand strip runs about as follows: in Hopkins County, near Sulphur Bluf!; in southeastern Hunt County, at Campbell, Dixon, Cash (faulted), and Quinlan (good exposure); in Kaufman County, just west of Terrell and Kaufman; in Navarro County, just west of Chatfield (good exposures), west of Corsicana, near Corbet and west of Pursley; in northern Lime­stone County, east of Cooledge, where it is thin, and where Steph­enson reports its southernmost exposure. In northeast Texas the formations of the Navarro are: Kemp formation (803, p. 343), including Stephenson's unnamed chalky marl member and unnamed upper clay member (1539, p. 1331). Nacatoch formation (1691, p. 27). Neylandville formation (restricted), comprising the basal part of the "Corsicana beds" of Hill (803, p. 342), and probably the "Exogyra cancellata beds" of Stephenson. See p. 516. Below the Nacatoch, as thu13 defined, is the basal (Neylandville) marl of the Navarro; and above the Nacatoch, ali the beds up to the basal greensand of the Midway are includéd under Hill's Kemp formation. It is to be noted that part at least of the basal marl is equivalent to the Saratoga in age, and that Thomas and Rice ( 160lb) would consider this part as more probably of Taylor age, thus placing the base of the Navarro group in, or at the base of, the Nacatoch. Composite section of Navan-o group from Franklin t<> Falls counties, Texas, with average thicknesses, by David J. Crawford Midway group (Eocene) : Midway clay Feet Basal Midway glauconite layer Navarro group: Kemp formation: Upper Navarro clay ..·----------------------------------------------------160 Sandy clay, thickness 16 to 20 feet. 11. Concretion layer, located in Navarrn below Midway greensand; dense compact concretions, well rounded, with many calcite partings. Clay, locally slightly sandy. 10. Concretion !ayer, located on tops and flanks of first Navarro scarp below Midway greensand, 30 to 40 feet below the Navarro-Midway con ta et; the best U pper Navarro bed for detailing. Sandy clay. 9. Concretion !ayer, in flat topography, 100+ feet below the Midway greensand. Clay, thin . The Geolo'gy of Texas-Mesozoic Systems 487 Feet 8. Sand, thin, about 15 feet, contains a concretion !ayer at hase; located about 15 feet helow No. 9, and ns+ feet helow the basal Midway greensand. This is a stray sandstone in this upper 15-foot sand break; it appears in Limestone County and prohahly continues south· ward to Milam County, where it may he the Minerva-Rockdale pro· ducing horizon. Sandy clay. 7. Concretion !ayer, 120+ feet helow Midway greensand, occurs in low places, field draws, washed from typical Navarro shales. Sandy clay, thin. 6. Concretion !ayer, located 10 to 15 feet ahove Navarro chalk. It is not persistent or continuous over any great distance and is a poor marker. Sandy clay, thin. 5. Navarro chalk stratum, immediately overlies the thin Nacatoch glau· conitic fossil hed; locally almost pure chalk, grading elsewhere into marl; thickness 1 inch to 10 feet. 4. Glauconitic fossil hed, marks top of Nacatoch sand; thickness 4­feet. Nacatoch Jormation: sand, sandy shale, and some concretions, .ahout 130 Upper sand. 3. Fossiliferous Nacatoch houlder horizon; in upper 30 feet of Nacatoch sand, occurs down east face of Nacatoch dip slope. lt is formed of well-defined boulders. To the north, in Hopkins and Hunt counties, these are of sandstone, hut farther south as the N acatoch becomes shalier across Limestone County, the boulders, although retaining sand characteristics, become very calcareous. Medial sand with shale lenses and scattered houlders. Basal sand !ayer, its basal contact. irregular or undulating. Neylaruluille Jormation; marl, containing an upper anda medial con· cretion bed; approximate thickness_ _______________ 265 2. Upper Corsicana concretion hed: persistent, calcareous, very hard, hrittle, easily shattered, locally fossiliferous concretions. The hase of the Nacatoch is at most places poorly defined, and this hed is useful as a check on that contact. Upper clays. l. Medial concretion layer, located ahout 150 feet helow the hase of the Nacatoch, and tops basal scarp of Navarro. Thin, persistent, fossiliferous, very calcareous concretions. Basal clays. Taylor group. Features of concretion layers and other markers in the above Navarro se e ti o n (David J. Crawford) Thick-Relia-Range Bed Color ness Hardness Fossils bi!ity Fracture (feet) 11 grayish 3±' 5-6 Rare Very Angular S± to white good 10 deep l'-3' 4 Rare to Excel-Argilla-15? yellow many lent ceous 9 red l" 2 None Good Angular 20± 8 .dark 2"-6" V&y None Undet. True ss. 2 gray hard fracture 7 brownish 3"-1' 6-7 None Good Sub-15± to reddish angular brown 6 chrome l ' 1 None Very Argillac. 1-3 5 (chalk) l"-10' Poor 4 (glauconite) 3 white to· l'± gray 4+ Man y Fair lrreg. 10-50 2 gray to %'-' Very None to Good Sub-20 yellow hard many angular 1 white 4"-1' 3± Present Good Argillac. 10± irreg. NEYLANDVILLE FORMATION Nomenclature.-The lower Navarro clays were apparently m­cluded, with the Nacatoch, in Hill's Corsicana beds (803, p. 342). They comprise most or ali of Stephenson's "Exogyra cancellata sub­zone" (391, PI. II; 1534, PI. 1) , and are, in part at least, corre­lated with the Saratoga chalk in southwestern Arkansas (392, p. 111; 1534, p. 15) . Although not entirel y a satisfactory arrange· ment, it is considered best here to restrict and redefine the "Cor­sicana" of Hill to include ali beds in the Navarro County section above the top of the Nacatoch sand and below the base of the upper clay of Stephenson, i.e., the "chalk marl" of Stephenson. The beds between the top of the Taylor and the base of the Nacatoch are here called N eylandville formation. This terminology follows sugges· tions recently made by Dr. L. W. Stephenson (see p. 516). The type localities of the Neylandville are taken as the first cut of the Texas l\fidland Railway west of Neylandville station, and exposures along the Bankhead highway between Liberty School and Neylandville, 3 to 6 miles in an air line northeast of Greenville, Texas. The Geology of Texas-Mesozoic Systems 489 Outcrop.-The basal Navarro consists generally of marls, with the scattered concretion layers described above. In sorne of the older literature it is not distinguished from the Marlbrook. Caddo field, Louisiana-Texas.-The "Marlbrook" has been de­scribed (1059) as consisting of 325 to 375 feet of shale, gumbo, and sorne chalk and boulders, part of which is probably basal Navarro. Hunt County.-Stephenson (1530, p. 157) describes the basal Navarro as follows: The lower 300 or 400 feet of the formation consists of gray calcareous shaly clay or marl that produces a dark gray or black soil and carries a distinctive fauna, the most significant species of which are Exogyra cancellata Stephenson, found at several localities near Cooper and Greenville, and Anomia tellinoides, Morton, found at one locality near the Texas & Midland Railroad 2 miles west of Cooper. This is the Exogyra cancellata subzone, which forms the basal part of the E. costata zone and which has been traced throughout the Atlantic and Gulf Coastal Plain from New Jersey to Kaufman County, Texas, and has been recognized at Ciudad del Maiz, San Luis Potosi, Mexico, about 440 miles south of Eagle Pass, Texas. This subzone is represented in southwestem Arkansas by the upper half or more of the Marlbrook marl with the exception of approximately the upper half of the "Saratoga" chalk member, which forms the upper 20 or 25 feet of the Marlbrook. Dane and Stephenson (391, p. 47) give certain details regarding the Exogyra .cancellata subzone northwards and eastwards from Rockwall County. In this direction the sandy constituent at the base of the Navarro disappears, and here the Navarro beds are typically less calcareous than the Taylor. At severa} localities along the Greenville road within 3 miles of Royce City, Exogyra cancel/ata occurs in calcareous clay or marl; at a point on this road 2.8 miles from Royce City Exogyra cancel/ata, Placenticeras?, and Baculites (large, smooth species) occur; at 2.5 miles from Royce City, E. cancellata, Placenticeras?, Anomia tellinoides Morton and Gyrodes occur; at the Greenville fair grounds, E. cancellata is abundant. The same zone occurs on the Josephine road 2 miles north by east of Nevada, Collin County, with the Taylor marl containing E. pon· derosa only a short distance below it. Rockwall and Kaufman counties.-Dane and Stephenson state (391, p. 46) that from a point 2.5 miles southeast of Chisholm, southeastern Rockwall County, south by west through Kaufman County, the Taylor is overlain by gray, sandy calcareous clay or inarl of unquestionable Navarro age. The clay contains E. cancel­lata and a "variety of that species in which the surface of the shell tends to he smooth instead of cancellated": in this zone the typical E. ponderosa has not been found, and E. costa.ta, which elsewhere in the Coastal Plain is associated with E. cancellata, seems also to be rare or wanting. At localities 4.25 to 4.65 miles west of Kaufman, the basal Navarro is supposed to he represented by a 2-foot bed of strongly glauconitic marl containing poorly preserved fossils and nodules of phosphatic material. This bed is overlain by sandy marl. In the Exogyra cahcellata zone in a cut l % miles east of Gastonia, Ostrea panda Morton and Exogyra cancellata were found; and in a cut 1 mile east of Gastonia there were found Exogyra can· cellata, E. costata, Anomia argentaria, Ostrea panda, O. tecticosta and Gryphaea sp. (large) . Navarro County.-In wells near Corsicana the basal Navarro marl consists of about 140 feet of mostly dark gray or greenish-gray calcareous clay, sorne of which is sandy, glauconitic and fossilif­erous. .At most places two concretionary beds exist, one at the top and one near the middle of the formation. The lower Navarro is exposed in a roadside ditch east of Cedar Creek on the Corbet highway 5.7 miles southwest of the Corsicana railway station, and consists of sandy marl with · large' concretions. On the Emhouse road 1.8 miles northwest of the Corsicana airport there is a road cut with 2 to 3 feet of yellow-gray sandy clay containing pelecypods and other fossils. Limestone County.-The basal Navarro in wells consists of about 265 feet of sandy marls with sorne sand streaks, some of them gas· bearing (543, PI. XIII). The best published descriptions of the lower Navarro outcrops hetween the Trinity and the Brazos are by Dane and Stephenson (391, pp. 55-57). They state that from Navarro County southward to at least the latitude of Cameron, the lower Navarro is mostly a sandy marl, which generally can he recognized by its less calcareous nature and by the presence of large dense gray limestone concretions. Basal sandy Navarro marl is exposed in western Limestone County southwestward from a point 4.2 miles east of Prairie Hill, and on the Groesbeck road 5 miles The Geology of Texas-Mesozoic Systems 491 east-southeast of Mart. The lower Navarro is stated to thin south· wards from about 200 feet in Kaufman and Navarro counties to not more than 50 feet in Milam County. Falls County.-The Exogyra cancellata zone was recognized by Dane and Stephenson (391, p. 56) in an outcrop of sandy marl with large concretionary limestone lenses weathering white, at a locality 6.1 miles northeast of McClanahan, Falls County. Stephenson has not recognized this zone anywhere in Texas south of Little River, Milam County (391, p. 57). Sa/,t domes in Gulf Coastal Plain.-The only known Navarro in­liers in the Texas Gulf Coastal Plain are on the Brooks, Butler, Bul­lard, Keechi, Marquez, and Palestine domes (p. 262). From the Brooks dome Hill (709, p. 223, footnote) collected Gryphaea vesi· cularis, Ostrea sp., Plicatula sp., and /noceramus sp., which he referred to the Marlbrook, and Harris (1250, p. 194) collected Exogyra costata, Gryphaea vesicularis and Ostrea larva, which indi­cate Navarro age. Probably Navarro is indicated by fossils col­lected on the Butler dome (1252, p. 265). On the Keechi dome lower Navarro with Exogyra cancellata, a micr.ofauna stated by Selig to be of the app.roximate age of the Nacatoch, and upper Navarro with Belemnitella americana, are known (1252, pp. 247­248). On the Palestine dome the Exogyra cancellata zone has been found. Navarro is known in wells over a wide area in the East Texas embayment. Renick (1298, p. 533) described it as follows: In the East Texas geosyncline the Navarro, including the Nacatoch, consists of 375 to 1000 feet of dark and light gray and hluish-gray marine shale and clay, generally slightly calcareous with thin heds of gray limestone and brownish, ferruginous limestone. Sorne lime heds contain siderite concretions. It is ahout 1000 feet thick in Freestone County, hut thins eastward to 400 feet or less in eastern Cherokee County. Near the top in eastern Anderson and Cherokee counties, hut apparently somewhat higher in the Navarro section in Freestone County where this formation is thicker, there is a horizon possihly equivalent to the Nacatoch sand in Louisiana. This Nacatoch (?) horizon in sorne places is sandy shale, sand, and thin non-calcareous sandstone; in others, interhedded thin limestone and shale. NACATOCH FORMATION Nomenclature.-The type locality of the Nacatoch62 sand, de­scribed by Veatch (1691, p. 27) is Nacatoch Bluff, on Little Mis­souri River, Clark County, Arkansas, where a 50-foot section is exposed. Synonyms in Texas are: Powell sand, Campbell sand, and prohably Minerva sand; and from Hill's description (803, p. 342), the Nacatoch sand appears to compose the upper part of his "Corsicana beds." Synonyms in Louisiana are: Caddo sand, Vivian sand, Shreveport sands. Outcrop.-The Nacatoch outcrop extends westward across the northern tier of Texas counties, Bowie, Red River, northern Delta, and turning southward with other Gulf outcrops in eastern Hunt County, passes through Kaufman and Navarro counties to northern Limestone County. Underground the Nacatoch is widespread in northern Louisiana and in the East Texas embayment, though its exact subsurface extent is not yet securely known. In northwestern Louisiana it is an extensive gas-bearing horizon. The upper sand in the Bethany gas field, the sand in Eldorado, the producing sand in the Mexia-Groesbeck gas field, the oil sand in the Powell field, the heavy oil sand in the Corsicana field, and the Minerva sand in northern Milam County, are supposed to be nearly or exactly equivalent to the Nacatoch. The fields along the Mexia fault zone where the Nacatoch has produced oil or gas are listed by Lahee (%9, p. 360). Red River County to Hunt County.-ln the Caddo oil field the thickness of the Nacatoch ranges from 100 to 200 feet, part of the di:fference being caused by the northward and westward thickening of the formation ( 1059, pp. 23-25) . It is composed of light gray to greenish fine sand, alternating with layers of indurated sandstone and thin layers of clay. Locally the formation contains glauconite or calcareous filling or cement. Shale, gumho, and in­durated fine sand occur in lenses. The N acatoch here bears gas and salt water. Westward across Panola County (859, p. 190; 1408, fig. 1) the Nacatoch thickens from a small amount to about 225 feet. Stephenson records in northeastern Texas about 100 feet of Naca­toch, consisting of fine gray sands and more or less sandy clays 62Literature.-Arkansas : Dane, 392; Veatch, 1691, p. 27. Louisiana: Howe, 850 (bibliography); Veatch, 1691. Northeast Texas: Dane and Stephenson, 391; Lahee, 969; Matson, 1059, 1060, 1062; Powers, 1248, 1252; Stephenson, 1530, 1534; Fohs and Robinson, 543; Shumard, 1469; Hyatt, 866; Sellards, 1408; Hull and Spooner, 859. The Geology of Texas-Mesozoic Systerµ,s 493 (1530, p. 157). Fohs and Robinson (543, PI. XIII) record the following sections of Nacatoéh: in the Paris-Ripley-Sulphur Springs area, 140 feet of hard sandstone and muddy sands; in the Terrell­Wills Point section, 150 feet of hard, water-bearing sands, each 5 to 35 feet thick, and sandy shales; in the Bethany field, 150 feet of gas sand; near Corsicana, 270 feet of sand and sandy shale, sorne of it glauconitic. In Anderson County (1298, p. 542) from 350 feet above the top of the Pecan Gap chalk down to near the top of that chalk, there occur sand, sandstone, and sandy shale, and locally interbedded thin limestones and shales, which have been correlated with the Nacatoch, and which in Cherokee County give good show­ings of gas. In Hunt County the Nacatoch strip passes west of Campbell and Dixon and near Cash and Quinlan. In a stream cut on the M. K. & T. Ry. about 3 miles east of Greenville the writer has collected, in a sand and sandy clay, abundant middle Navarro fossils, in­duding Exogyra costata (narrow, elevated ribs), Pycnodonta aff. vesicularis, Trigonia, Pecten, Eutrephoceras and gastropods. In Kaufman County the Nacatoch outcrop passes just west of Terrell and Kaufman. Navarro County.-The narrow Nacatoch outcrop passes through Chatfield, the western edge of Corsicana, near Pursley, east of Corbet and thence to a point east of Cooledge, northern Limestone County. The thickness in wells near Corsicana is about 200 feet. Matson · and Hopkins (1062, p. 218) state that locally the sand is firmly cemented by lime to form hard, dense, calcareous sandstones or ir­regular shaped concretions. The sand ranges from medium grained to very fine grained and contains glauconite, which is more abundant in sorne beds than in others. Most samples of the sand are de­scribed as fine grained or very fine grained, greenish gray or dark gray, calcareous or argillaceous, and glauconitic; sorne are hard; a few levels in the formation are fossiliferous. A subordinate amount of dark gray, sandy, calcareous clay is present, apparently in lenses. B. F. Shumard (1469) named the Navarro formation and de­scribed many fossils collected near Chatfield and Corsicana. Dr. T. W. Stanton collected in the same area about 1890, and sorne of his fossils were described by Hyatt (866). In recent years the region has been extensively but unsystematically collected. The Nacatoch outcrop crosses the Rice-Dallas Federal highway No. 75 about 2.75 miles north of the T. & B. V. Ry. underpass in Corsicana, and here there occur sands containing large concretions with fossils (Baculites, lnoceramus, Turritella). In northern Navarro County there are many Nacatoch outcrops; fossils occur at the Negro cemetery 1 mile north-northwest of Chatfield, and in concretions on the Hervey Lake road 2.1 miles northeast of Chatfield. From these localities Miss Gene Ross and others have collected numerous Nos­toceras, Helicoceras, Oxybeloceras, Baculites, Inoceramus and gas­tropods. Limestone County.-On the outcrop the Nacatoch is thin or absent; it has been reported to be thin near Cooledge. Passing underground down-dip it thickens considerably. Matson (1060, pp. 81, 89, 92) states that in the Mexia-Groesbeck area the Naca­toch has a thickness of 40 to 65 feet, and averages 40 feet, ex­cluding the cap rock. The sand contains locally partings or lenses of shale, most of them 3 to 4 feet thick but sorne as thick as 10 feet. The sand is mostly fine grained, light gray quartz sand con­taining many grains of glauconite. Its top is generally cemented into a denser, firm sandstone, which forms a cap rock 1 to 10 feet (average 5 feet) thick. Beneath the cap rock the sand is porous except for layers and lenses of clay. The amount of pore space in samples tested ranges from 16.6 per· cent to 34.2 per cent, and averages 25.5 per cent. From the uniform decline in pressure throughout the field it is assumed that the amount of porosity is maintained over a wide area. Lahee (969, p. 327) states that "a few hundred feet below the disconformity (top of the eroded Na­varro) is a zone of shaly sands and true sands, niore or less glau­conitic, forming the Nacatoch sand member of the Navarro. In sorne localities, notably near Richland, the upper Navarro clays become progressively more. marly downward, changing into a thin, hard limestone layer which caps the Nacatoch sand zone. This sandy zone ranges from 150 to 250 feet in thickness. It is not the same in all places, but as a rule contains one or more distinct sands, which may carry water or, on favorable structure, oil or gas." The Edens sand (1062, PI. XX) lies near the Taylor-Navarro contact, The Geology of Texas-Mesozoic Systems 495 and is thought to be the same as the Chatfield gas sand. As ex­ plained earlier, the "Corsicana" sand in the Taylor of this area is probably the W olfe City sand. Specimens of Ostrea owenana Shumard were identified by Steph­enson from the glauconitic gas sand in the Mackey well near Mexia, and it is stated that the sand "probably corresponds in age to and may be physically continuous with the Nacatoch sand" (1060, p. 80). Milam County.-The Minerva sand, lying about 110 to 120 feet below the local top of the Navarro, consists of rounded quartz grains, and is generally 3 to 10 feet thick with a maximum thick­ness of about 15 feet. KEMP FORMATION Nomenclature.-The upper part of the Navarro in the Navarro­Kaufman County area was called Kemp beds by Hill. The presum­able type locality is the faulted inlier ·near Kemp. Fossiliferous upper Navarro is exposed at many nearby places, as Quinlan and tbe Corsicana clay pits. Stephenson suggests that the chalk marl above the Nacatoch sand receive tbe name Corsicana formation (of Hill, but re· stricted); see p. 517. Outcrop.-At various places in Texas tinknown amounts of sec­tion have been suhsequently removed from the top of the Navarro column, or else an unknown amount was never deposited, or exists down-dip hut is overlapped nearer the outcrop by Midway. The Kemp formation has heen in part correlated by many writers with the Arkadelphia clays in Arkansas. Northeastern Texas.-ln the Caddo oil field the upper Navarro clay is 300 to 400 feet thick (1059, pp. 25-26). It is a dark gumho or shale, with thin layers of sand and sandstone near the hase. In Panola County 600 feet of Arkadelphia has heen re­corded (Hammill, 643a; Sellards, 1408, p. 7). In the Paris­Sulphur Springs area the upper Navarro shale containing sorne sand is stated (543) to he about 535 feet thick; and in the Terrell­Wills Point section it consists of 590 to 620 feet of hlue to hlack shales with sorne lime concretions near tlie top, and with sorne sandy shales and thin sands. In the Bethany area it consists of 500 feet, chiefiy of shales with lime heds in the lower half. Navarro County.-The upper Navarro clays are descrihed (1062, pp. 218-219) as being slightly sandy and glauconitic, calcareous, and locally gypsiferous. The clay is dark blue when fresh, and weathers to greenish yellow, then to dark olive gray, and finally to black, waxy soil. lt contains calcareous concretions, sorne com· posed of hard, dense limestone, sorne with septarian form, and sorne with cone-in-cone structure. Limestone County.-The upper Navarro clay is described (1060, p. 89; 969, p. 327) as a compact to finely laminated gray clay, with a marked conchoidal fracture. The contact with the Midway is disconformable, and the Navarro surface contained inequalities over which various members of the Midway were deposited; locally the Tehuacana limestone is nearly in contact with Navarro, and at other places the two are separated by as much as 100 feet of sandy clay. In sorne localities, notably near Richland, the upper Navarro clays become progressively more marly downward, chang· ing into a thin, hard limestone !ayer which caps the Nacatoch sand. Salt domes in Coasta/; Plain.-On the Keechi dome fossils were collected which Stephenson (1252, pp. 247-248) considered as "probably very near to the top of the Navarro"; they included Belemnitella americana, Baculites, and Pachydiscus. SOUTH-CENTRAL TEXAS From near the Brazos (Milam County) southwards along the outcrop, the Navarro is considerably thinner than farther north, and the width of outcrop is correspondingly reduced. This situa­tion persists as far south as Bexar County, where the Cretaceous outcrops swing westward parallel to the Balcones fault, and thence to northern Maverick County, where the Navarro section becomes greatly thickened on entering the Rio Grande embayment. Stephenson, using Exogyra zones and lithology, has explained this regional thinning of the Navarro gn;mp as caused by the absence at the outcrop of certain basal Navarro beds .. He states that from Falls County to Bexar County, a distance of 150 miles or more, the Exogyra cancellata zone is totally absent at the outcrop (1534, pp. 13-14), and that "the stratigraphic break between the Taylor marl and the upper Navarro, which in Travis County accounts for the absence o.f the Exogyra cancellata zone and the Nacatoch sand member, continues toward the southwest with as great or greater magnitude nearly to the Rio Grande Valley, where, in the vicinity of Eagle Pass, Maverick County, the gap is only partly filled by the Olmos, a coal-bearing formation" (1539, p. 1332). In the following paragraphs it will appear that the Navarro beds in this area consist in part of sandy strata, which by sorne geologists have been The Geology of Texas-Mesozoic Systems 497 identified as Nacatoch, and that down-dip the Navarro thickens enormously, so that even if sorne basal Navarro is locally missing at the outcrop it may he present down-dip. So far, the only proposed suhdivisions of the Navarro in this area are (a) an unnamed chalky mar! member, and (b) an unnamed upper clay member, of Stephenson (1539, p. 1331). Milam County.-The basal zone of the Navarro, consisting of sandy marl with both Exogyra cancellata and its smooth variety, occurs at a point 1.7 miles south of Burlington on the Cameron road, and at a point 7.4 miles northwest of Cameron on the Buck­holts road. At a road exposure .4 mile southeast of the last­named locality there is a suggestion of an unconformity above the E. cancellata beds, which would cut these beds out farther south: at this place "gray sandy marl of typical lower Navarro lithology, such as outcrops only 0.4 mile farther northwest with a typical fauna, is overlain on a somewhat irregular contact by a 2-foot bed of richly glauconitic green, marly sand which carries typical Exo­gyra costata in association with strongly noded Exogyra cancellata, identical with the forms found in the Saratoga chalk of Arkansas" (391, p. 56). Williamson and Travis counties.-On the outcrop from northern Williamson County southwards, the upper Navarro and the upper Taylor: are so near to each other as to leave no room for lower Navarro outcrops (391, p. 57). However, the situation is still somewhat obscured by two factors: (a) faulting at or near the contact; and (b) the question of whether zonation can be based on the distinction between a variety of E. ponderosa characterized by cancellated sculpture on the umbonal portion of the shell, an upper Taylor form which is ancestral to, and probably prophetic of, the more typical E. cancellata of the lower Navarro (391, p. 57); and a nearly smooth variety of E. cancellata which occurs in the lower Navarro (391, p. 56). Near Kimbro, northeastern Travis County (391, pp. 57-58; 1539, p. 1331), the upper part of the Taylor is a non-chalky marl con­taining Exogyra ponderosa (var. with cancellated beak region) , various Taylor megafossils, and according to Mrs. Helen Jeanne Plummer, typical Taylor foraminifera. At a somewhat lower level is a nodule zone, containing many ammonites, among them Spheno­discus cf.. lenticularis (found by Dr. F. L. Whitney), Heliococeras?, Placenticeras cfr. intercalare, Menuites, Nostoceras, Oxybeloceras and Baculites. Taff (1574, p. 356) records the fossiliferous nodule bed from Rice's Crossing. The Taylor marl is directly overlain by Stephenson's "chalky marl carrying a micro-and macro-fauna such as is characteristic of the chalky marl above the Nacatoch sand in Navarro and Limestone counties." In the base of this chalky marl there are a few small, dark phosphatic nodules. Thus, according to Stephenson, both the Exogyra cancellata zone and the Nacatoch are absent at Kimbro. At a road cut 8 miles west of Cameron, Milam County, he states that the chalky marl member of the Na­varro · rests, with a sharp, somewhat irregular contact upon the lower Navarro Exogyra cancellata zone, only the Nacatoch sand being absent. In Travis County the Navarro, consisting of sandy clay and sorne black carbonaceous shales, was called "Webberville" by Hill and V aughan ( 795, pp. 241-242; 808) . The thickness recorded ( 1429) in wells is about 600 feet. Bastrop and Caldwell counties.-In Bastrop County wells the Navarro is recorded (1422) as about 550 feet thick. lt consists in the Larreinore area in Caldwell County, where it is exposed as the lowest outcropping formation, of bedded gray clay shale and beds of yellow to gray, fine-grained, limy sandstone (1716). In the Salt Flat field (1076) it consists of about 500 feet of massively stratified marls. The upper part of the Navarro contains much sand in strata of blue-gray, fine-grained sandstone, sorne of which are as much as 12 inches in thickness, interbedded with gray marl and sorne sandy shale. The lower half oí the Navarro is principally gray marl. Brucks (165) records the combined Taylor-Navarro thickness in the Luling field as about 1350 feet. At Lytton Springs the Navarro is given (188) ;as 550 feet of light bluish to dark clay and marls with thin sandstone layers and limestone concretions; the middle and upper Navarro contain numerous hard ledges. In the San Marcos area Brucks (164, p. 831) records 500 to 600 feet of Navarro, most of it bluish-gray calcareous clays, but the uppermost beds consisting of similar clays interbedded with cross-bedded and evenly bedded, very fine grained, variably indurated, calcareous sandstone, light blue when fresh, weathering to a grayish-yellow color. The formation has a rolling-plain topography, forros heavy black clay soils, and bears predominantly mesquite timber. Mr. R. The Geology of Texas-Mesozoic Systems 499 L. Cannon has kindly furnished the following notes concerning Navarro sands in the San Marcos area: There are two zones in the Navarro formation carrying sand in the San Marcos quadrangfo. The lower of these is the Exogyra costata zone.63 personally believe that this horizon is the equivalent of the Nacatoch member. At the time of working in this part of the section, having seen it from this area to southern Arkansas, 1 felt convinced that the same fossil assemblages were represented generally throughout the area. A higher sand rnember may he seen in isolated places in the area between ·the San Marcos River and San Antonio. A locality is on the southwest bank of the San Marcos River about a mile north of Staples. Three other localities occur in about a straight line at distances 5 to 7 miles southwest of Staples, the middle one being about a mile west of Wade School. In places, if my rnemory serves me right, there is as much as 30 or 40 feet of fine sandstone in this member. The clay pit of Blumberg's Brick Company, south of McQueeny and west of the Guadalupe River, has thin sandstone members in the upper part of the exposed section. Bexar County to Uvalde County.-ln Bexar County (1402, p. 50), a thickness of about 450 feet has been assigned to the Navarro. An upper 100 to 150 feet is locally sandy and oil-bearing. In Medina County about 580 feet is considered Navarro, excluding beds from which Exogyra ponderosa, Echinocorys texanus and Bos­trychoceras n. sp. aff. polyplocum have been collected (992, p. 71). On the Castroville road about 17 .3 miles west of the Missouri Pacific station at San Antonio, there is exposed in a prominent road cut Navarro limy marl and limestone nodules with abundant Exo­gyra costata (prominent, narrow and elevated ribs), Pycnodonta aff. vesicularis, H emiaster bexari Clark and severa! other f ossils. In Medina County the D'Hanis hrick pit leve! consists of about 65 feet of soft yellow clay with a few thin limestone )edges near the top. This is followed by about 400 feet of soft, yellow arena­ceous clays containing thin ledges of hard, brown arenaceous lime­stones up to 2 feet in thickness. These two layers contain shark teeth, oysters, pelecypods and gastropods. There follows about 65 feet of fine-grained very fossiliferous, hard, yellow, arenaceous limestones, with interbedded, soft calcareous shaly clay. This is the 00Expoaures occur at ahout the following distances and directions from Staples : 1 mile east; 3 miles north of west; 3 miles north-northwest; 4 miles northeast; 3 miles south-southwest. Another road locality is 4 miles northwest of Lockhart. Sphenodiscus pleurisepta horizon; associated fossils are Ostrea cor­tex, Nucula, pelecypods and gastropods. The upper part of the formation consists of very fossiliferous, hard, light to dark brown limestone strata up to 2 feet thick, interbedded with thin clay shale strata (992, p. 71). This level contains Ostrea cortex. The stratigraphic facts about the Navarro-Tertiary contact from Medina County to the Rio Grande have been excellently detailed by Stephenson (1528), and are briefly discussed on a later page. In Uvalde County the Pulliam formation of Vaughan is only about 100 to 200 feet thick, and although it has not been zoned, comparison with the Escondido farther south indicates that a con­siderable thickness has been removed from its top; in Uvalde County wells the Escondido has a recorded thickness of 550 feet; and passing southwards into Maverick County this formation thickens rapidly. RIO GRANDE EMBAYMENT In the Rio Grande embayment the Navarro section thickens greatly on passing underground and down-dip. Part of this thickening represents beds intercalated down-dip but not present at the out­crop, and part represents thickened offshore extensions of beds present at the ·outcrop. Sorne of the thickening may be caused by the appearance down-dip of younger beds at the top of the section, which are covered nearer the outcrop by the overlapping Carrizo and other Tertiary formations. An additional important feature of the Navarro in the Rio Grande embayment is that, on the outcrop, certain levels (notably Olmos, Tulillo, and Aguja) are in the marginal facies, whereas down-dip most levels have assumed the marine neritic facies. The sections in the Amerada-Rycade No. 1 Oppenheimer well, Frio County, and those on the Chittim anticline east of Eagle Pass, noted in the following paragraphs, illustrate the features just mentioned. The corresponding sections on the Mexican side of the Rio Grande have been described by Bose and Cavins (134, 135). The thickening of the Navarro group southward from Uvalde is notable: in Uvalde County wells the Escondido is 550 feet thick; in central Maverick County the Olmos is 434 feet thick, and the Escon­dido 1675 feet thick (1681, p. 253); in the Sullivan No. 1 well, The Geology of Texas-Mesozoic Systems 501 southeastern Maverick County, the total Navarro is 2830 feet thick; and in the City National Bank well No. 1, in western Dimmit County, the Navarro is 2437 feet thick. The general section on the Chittim structure follows (578, pp. 1432-1433): Feet Escondido: Marine limestones and shales___________________________________________ 750 Marine Navarro beds, older than Escondido______________________________ 330-420 Olmos: Non-marine, sandy, lignitic, coal-bearing shales.________ __--400-600 Farias beds: Marine Navarro, glauconitic, sandy shales and impure sand­stones; containing lnoceramus and other fossils__________ ___ 200 Marine Navarro, lignitic muddy sandstones and sandy shales______ 400 Marine Navarro: very micaceous, calcareous, sandy shales with a prolific basal Navarro microfauna______________________________________ 325 For comparison, another Rio Grande embayment section, in the Amerada-Rycade No. 1 Oppenheimer well, Frio County, is sum­marized, through the courtesy of Mr. L. W. MacNaughton. In this well the upper Navarro is supposed to be 815 feet thick (3252­4067) and the lower Navarro about 993 feeti (4067-5060). From microscopic examinations of cores and cuttings, the follow­ing depths have been stated for the Upper Cretaceous groups in this well: Navarro ------------------------------------------------------_3252-5060 1808 feet Taylor --------------------------------------------------------5060--5435 375 Austin ----------------------------------------------------------5435-5650 225 Eagle Ford ________________________________________________5650'-6039? 389? The Buda has been reported at about 6039 feet, and the Edwards at 6302 · feet. In the basal part of the Navarro sºome limestone and considerable sandstone were cored. OLMOS FORMATION Nomenclature.-The Olmos beds were called "Coal Series" by Dumble (468, p. 225), who extended White's use of the term "Eagle Pass division," and by later writers. Stephenson (1534, pp. 10, 14) in 1927 named the beds the Olmos, from the station Olmos, Maverick County, and from Olmos Creek, the type locality. Olmos (Elm) Creek follows the strike of the beds from about 7 or 8 miles north of Eagle Pass to the Río Grande ahout 2 miles ahove Eagle Pass. Areal outcrop.-The Olmos formati-0n is largely non-marine sands and clays, on the outcrop 400-500 feet thick, and in wells 400-600 feet thick. It consists -of clays, shales, and sandstones, with seams of coal and fireclay. Only one of the coal seams _ is thick enough to he profitahly mined. Along Olmos (Elm) Creek irregularly stratified sandstones and clays containing fer­ruginous concretions and silicified wood are exposed. There is -no constancy in the small heds of sand and clay; they are simply interlocking lenses (1687, p. 23). At several mines in the dis­trict the workahle coal seam is ahout 6 feet thick, as in the old Hartz mine near Eagle Pass. In the clays ahove the coa! a Laramie palm, Geonomites tenuirachis Lesquereux was found. The Eagle Pass coal is present at Fuente and in other mines near Piedras Negras, Coahuila, and coals of the same age, extend for 140 km. southwards into the coal hasins of Sabinas and Barroterán. Udden measured the coa! and adjacent strata on the Mexicar> and the American sides near Eagle Pass, and concluded that, although the total thickness of coal is relatively constant, toward the northeast the coa! seams are hroken up by clays, and that the coals hecome more impure (1625, p. 77). Sections in the Sabinas hasin show that the facies of the formations has changed and the local divisions estahlished at Eagle Pass are replaced by other local heds. Agui­lera64 lists fossils from the well-known locality near Las Esperanzas: Exogyra costata Say, Ostrea arizpensis Bose, Placenticeras stantoni var. bolli, P. intercalare Meek, P. placenta (Dekay), and Spheno­discus lenticularis (Owen). From douhtful Olmos near Eagle Pass, -V aughan lists severa} marine fossils. Silicified wood is noted by various writers. ESCONDIDO FORMATION Nomenclature.-The highest Navarro formation, the Escondido, was named by Dumhle ( 468, p. 227) in 1892. The type locality is near the mouth of Río Escondido, which empties into the Río Grande ahout 2 miles helow Piedras Negras. Dumhle says that a mile helow the mouth of this river the top of the coa! series (Olmos) 8'Aguilera, J. G., Les gisements carboniferes de Coahuila, IOth In..t. Geol. Cong:., Livret·Guide .No. XXVII, 1906. E. Ludlow, Les gisements carbonifhes de Coahuila, ibid., No. XXVIII, 1906. The Geology of Texas-Mesozoic Systems 503 crosses the Rio Grande and is capped by the basal hard ledge of Escondido, the same that caps the hills in the eastern part of Eagle Pass. The exposure of Escondido, a mile long, consists of clays and ripple-marked sandstones dipping down stream about 2°. lt is sometimes stated that the type locality is on the Arroyo de Caballero, 35 miles down the Rio Grande from Piedras Negras. The topmost Escondido is exposed at this locality which is opposite the bluffs on the American side in which Stephenson (1528, PI. XVI) figured the Cretaceous-Tertiary contact. On the Mexican side on the Blessé Ranch is Loma Prieta, a small conical hill containing the contact. At Arroyo Caballero are found: Sphenodiscus pleurisepta, Para· pachydiscus aff. colligatus, Cassidulus cf. subquadratus, Ostrea glabra, and crustacea. Areal outcrop.-In Maverick County, the Escondido, 550 to 75q feet thick, covers a wide outcrop on account of its superior resistance to erosion, and is subdivided by more prominent hard ledges into three parts. Northward these parts lose their identity by overlap and change of facies. The base is excellently exposed capping the cliffs just east and north of Eagle Pass, where on the first back­slope Exogyra costata and Sphenodiscus occur in the softer layers. The Escondido consists of dark clays and marls, interbedded with more or less extensive strata of sandstone, limestone and shelly ledges. If the basal hard layers just mentioned are taken as the base of the Escondido, then the upper part of the Olmos is fossilifer­ous, and consists of 35 feet of purplish, sandy or silty clay and sand­stone, containing several species of marine pelecypods and gastro­poda. Hard Escondido members form prominent cuesta faces 2 to 3 and 7.5 to 8 miles east of Eagle Pass. Udden divides the Escondido into (1) basal sandstol).e followed by basal clay; (2) medial sand­stone and clay; (3) upper sandstone and clay. The sandstone and clay strata and especially the oyster shell ledges are very lenticular md erratic in outcrop. Ali of these units show a m'.""ked down-dip deflection on crossing the Chittim plunging anticline, as do the Upson, San Miguel and Olmos beds (578, p. 1430, fig. 1). The basal sandstone consists of medium to thick-bedded ledges separated by clay strata, and locally broken up into two or three units. In composition it ranges from a siliceous sand to a fairly pure limestone composed of considerable shell fragments. lt is mostly of fine texture, but contains sorne gravel seams. Ripple marks, fragments of reptilian bones, and barite occur. It is recorded as unconformably overlying the Olmos beds. Udden gives its thick­ness as 30 to 100 feet. The lower clay, about 275 feet thick, makes a prominent back-slope and shelf down-dip, south and east, from the sandstone. The clay contains fibrous barite. The bottom of the medial sandstone unit forms a range of bilis extending from north to south about 3 miles east of Eagle Pass. It is more lenticular, more porous, and coarser grained than the basal sandstones. Locally shell breccias of Ostrea cortex reach a thickness of 40 feet. The entire unit is about 130 :feet thick. The medial clay is light gray and contains small ftakes of gypsum, and in its upper part large yellow limestone concretions, many with Sphenodiscus pleurisepta. The clay contains frequent Ostrea cortex throughout, and locally ledges of shell aggregate. · The fine-grained upper sandstone is persistent but thin, 5 to 30 feet thick. The upper clay consists of 100 or more feet mostly of clay with fibrous barite, oyster aggregates, and thin sandstones. Udden reports Ostrea iridensis in this unit. Some fossils recorded from the lower part of the Escondido are: lnoceramus barabinai Morton, Turritella cf. safjordi Gabb, Trigonarca cuneata Gabb, Cardium cf. eufalense Conrad, Sphenodiscus pleurisepta (Conrad) var. From the Upper Escondido the following are recorded: Ostrea cortex Conrad, Cardium cf. eufalense Conrad, Mactra cf. war­reneana M. and H., Eutrephoceras dekayi (Morton), Sphenodiscus pleurisepta (Conrad). Bi:ise and Cavins have investigated and zoned the Escondido in the neighborhood of Lampazos, Nuevo Leon, in Las Mesillas and the Mesa de Cartujanos. lt is entirely possible that in this district higher heds are present than at Eagle Pass, hecause of removal of the overlapping Tertiary beds. At any rate, characteristic ammo­nites, Coahuilites and certain species of Sphenodiscus, have not yet heen reported from the American side. These ammonites Bi:ise considers to indicate Maestrichtian age, a conclusion already reached hy others from the occurrence of the supposed Parapachydiscus aff. colligatus at the Arroyo de Caballero. From their ammonite collec­tions Bi:ise and Cavins established the following Escondido zones, in ascending order: (1) Coahuilites sheltoni; (2) Sphenodiscus lenticularis; (3) Sphenodiscus intermedius; (4) Coahuilites cavinsi; (5) Sphenodiscus pleurisepta. lt will he noted that in Las Mesillas The Geology of Texas-Mesozoic Systems 505 and the Mesa de Cartujanos they consider Exogyra costata to under­lie their Coahuilites zones, and that they record two species of Sphenodiscus well known from Texas. Another feature of im­portance is that they describe a Navarro facies of non-marine sand­stone containing brackish-water pelecypods, the Tulillo facies. BIG BEND The formations of the Navarro group in Brewster and Presidio counties are, in ascending order, the Aguja (upper part), and the Tornillo. Ammonites indicate that the lower part of the Aguja is of Taylor age. AGUJA FORMATION Nomenclature.-When in 1907 Dr. Udden described his "Rattle­ snake" formation, the name had already been used for a formation in the Oregon Pliocene.65 Accordingly the name Aguja is here substituted for Udden's name. The type locality is Sierra Aguja (Needle Peak), in the flat in front of the Santa Helena fault scarp, 6 miles south of Terlingua, Brewster County, Texas. The slopes and surrounding flats contain a practically complete section of the beds, overlain by the Tornillo clay, and situated close to Udden's original type locality. Areal outcrop.-Navarro equivalents outcrop in only two areas in Trans-Pecos Texas: (1) in the Terlingua-Chisos area; and (2) in the San Carlos-Candelaria-Presidio area, southern Presidio County. Lithologically and paleontologically the outcrops are very similar in the two areas and in both places may be referred to the Aguja and Tornillo formations. The Aguja makes a nartow belt of outcrop encircling the Chisos Mountains except on the south. East of the Chisos at many places the outcrop is badly overwashed by bolson fill controlled by local levels, but nearer the Rio Grande and along large creeks, such as Tornillo Creek, good exposures occur. Such exposures are at San Vicente, and along Tornillo Creek 2 or 3 miles north of Hot Springs. Exposures occur north of Burro Mesa at Chisos Pen, along the headwaters of Cottonwood Creek. In the Terlingua quadrangle the 85Merriam, J. C., A contribution to the geology of the John Day Basin: Calif. Univ., Dept. Geol., Bull. 2: 269-314, 1901 ; a!so in Calkins 1902, ibid., Bull. 3 : ll4. Apparently the name Rattlesnake has also been used for a granite intruding probably Triassic, by F. E. Hudson, Calif. Univ., Pub!. Dept. Geol., Sci. Bull., Vol. 13, No. 6, pp. 181, 207-208, 1922. Aguja has outcrops in two general areas. It enters the eastern edge of the quadrangle just south of Maverick Mountain and Study Butte, and in the lowlands of Rough Run and Dawson Creek it is exposed in a series of south-dipping parallel cuestas. From the Taylor outcrop near Study Butte south to the Tornillo purple and vari­colored clays south of Dawson Creek, the entire Aguja is well exposed. Thence the formation makes a large outcrop south of Cuesta Blanca, and extends southward covering the area between Willow (Sauz) and Terlingua creeks. The beds here dip east­wards under the Tornillo and higher formations of the Chisos Mountains. It is notable that just south of the Rio Grande the Aguja disappears and the Tornillo is in fault-contact with Fred­ericksburg along the Santa Helena fault. From a point north of Terlingua Abaja northwest to near Comanche Spring, the Aguja and Tornillo lie in a downfaulted block in which the igneous­capped Sierra Aguja (the type locality) is situated. A second general area of Aguja is in the northeast quarter of the Terlingua quadrangle, east of Terlingua Creek. Good outcrops occur south of the fault scarp which crosses the Alpine-Terlingua road east of Hen Egg Mountain, in the flats encircling the dome at Payne's water hole, and in the flats north of Leon and Bee mountains. Three widespread types of sediments compose the Aguja: (1) rather coarse grained fossiliferous sandstones, weathering to dark brown, tan, yellowish-brown, and blue-gray shades; (2) lustrous to dull black, non-marine, carbonaceous, lignite-bearing shales, and especially near the top of the formation sorne purplish, vermilion or greenish-gray shales, like those typical of the overlying Tornillo; (3) massive shelly clays, somewhat like those in the Taylor but generally weathering more yellowish-brown, and generally more sandy or silty. Udden states that the formation consists of sand­stones, muddy and peaty clays and silts, a little limestone in thin strata, and a few thin beds of gravel. In . the sandstone layers locaÜy there are numerous casts of /noceramus cumminsi, Cragin, and other species, and locally spherical, sandy, "cannonball" con­cretions up to a foot in diameter. At most contact localities the basal heavy shelly sandstones are distinct, but locally they appear to be absent, and in those places the basal Aguja sandy clays are distinguishable with sorne diffi.culty from the Taylor. In most areas where the beds are inclined, the topographic differentiation between The Geology of Texas-Mesozoic Systems 507 sandstone ridges and shale valleys is striking. Udden states that the basal 100 feet of Aguja is transitional to the underlying Taylor, and has very similar clays, but contains the following fossils: V oluto­mor pha cf. ponderosa Whitfield, Camptonectes burlingtonensis Gabb (?), Thracia sp., Gyrodes (?), Natica (?), "Rostellites" [Volutoderma] texana Conrad (?), Dentalium, Baculites, fish teeth, and others (1626, p. 42). Single beds of the sandstones are as much as 60 feet thick. They are well sorted. The grains are generally less than 1h mm. in diameter, and are free from grave! or mica; they consist of quartz, sorne chert (in the larger sizes), sorne magnetite, organic frag­ments, and calcareous material. The sandstones locally grade into thin limestones. Secondary calcareous cement from action of ground water is quite generally present. In sandstones 300 feet above the base of the Aguja, Udden (1626, p. 44) reports Haly­menites. This alga (?) is a conspicuous marker in the Nacatoch sand in Arkansas, a fact probably significant for correlation. The finer sediments in the Aguja consist mostly of silts below, and of finer-textured clays above. The silts are locally marly, the calcare­ous material being present to an extent sufficient to form irregular concretions. Sorne original calcareous matter is present in the form of thin limestone seams containing organic fragments, and poorly assorted calcareous sand and mud. Thin limonite layers are present. Locally the iron concretions are circular disks, and sorne are thinly laminated cand on weathering split into thin leaves. Paleontology.-One of the commonest Aguja markers is Ostrea sp. aff. pratti Stephenson (sometimes called O. subspatulata Forbes, thicker than O. owenana Shumard). This conspicuous and durable oyster is abundant and widespread in the lower Aguja sandstones and sandy clays. Here also occurs a zone of abundance of Exogyra sp. (with fine, numerous costulations), and Exogyra a:ff. cancellata; apparently typical E. costata (with narrow, elevated costae) has not been reported. Ostrea glabra and another very long oyster, found at Chisos Pen and elsewhere, characterize the Aguja. Casts of Inoceramus cumminsi are abundant in the Aguja sandstones. Rudistids include Durania cfr. maxima Logan and Durania n. sp. A striking feature of the Aguja is the local abundance of a large gastropod fauna, consisting of many species like those described from the Ripley ( 1700) . Locally an extensive bryozoan reef occurs near the base of the formation. Among the cephalopoda identified from the Aguja are: Placenticeras intercalare Meek, P. meeki Bohm, M ortoniceras cfr. delawarense (Morton) , Submortoniceras n. sp. a:ff. woodsi Spath, Libycoceras (?) n. sp. Baculites spp., and Eutre­phoceras sp. The Aguja near Newman Springs and San Carlos is lithologically similar, and contains Mortoniceras, Submortoniceras, Placenticeras, Baculites and other ammonites, and the same Exogyra as near Terlingua. Extensive reptilian beds occur in the Aguja. Those near Terlingua were studied briefly by Williston and by U dden ( 1626) . They occur in the lustrous and dull carbonaceous beds above the basal Aguja sandstones in the Terlingua and Chisos quadrangles. Above the ammonite beds about 3 miles northwest of Vieja Pass dinosaur beds occur in a brownish silt. Tracks also occur on the Quinn (Means) ranch at the spring about 3 mil~s north-northwest of Newman Spring, San Carlos sheet. TORNILLO FORMATION Nomenclature.-The highest part of the Aguja is largely clays, free from sandstones, and grades upwards into the Tornillo clays, apparently without a sedimentary break. The Tornillo is prohahly Cretaceous (Udden reports saurian bones), and may or may not he marine. lt is similar in lithology to sorne of the upper Aguja clays. The name was given by Udden (1626, p. 54) in 1907. The type locality is along upper Tornillo Creek, north of the Chisos Mountains and Burro Mesa ( Chisos quadrangle) . Areal outcrop.-Vdden states that at least 600 feet of these clays overlie the Aguja. They are gray, dull olive-green, dull hlue, dull red, dull yellow, dull purple, dirty hrown, and locally hlack and white; the prevailing colors are bluish-hlack with a somewhat rusty tinge, and with locally thick seams of dull purple. The Tornillo in general has a more rounded weathering than the Taylor, and lacks the steep and even vertical clay ridges, undercut slopes and clay slides of the Taylor. It is generally less calcareous and more lam­inated. lt contains local thin lentils of tough, cemented sandstone. The clays have a very fine texture, and consist of particles mostly less than 1/64 mm. in diameter. Calcareous material is rare; it is The Geology of 'J'exas-Mesozoic Systems 509 associated with thin seams of sand; gravel, or iron carbonate; iron­stone and other small residual concretions cover much of the weathered clay surface. Two . features of · weathering characterize the Tornillo, creeping, and clay halls. The Tornillo, in contrast to the underlying Aguja, is so impervious to water that after rains only a thin surface }ayer is moistened. This layer on drying cracks off and breaks into angular and rounil lumps which cover and roll down the slopes. The lack of moisture prevents any vegetation which might impede the clay slides. 'l'he Tornillo clay contains in most levels consiqerable bentonite, and sorne parts of it are largely composed of bentonitic minerals. Similar 01.i:tcrops occur over considerable areas in southern Pre­sidio County west of the Rim Rock. An irregular, locally faulted outcrop extends from south of Newman Spring (San Carlos quad­rangle) west almost to the Rio Grande, and another extends south and west for sorne miles from the Empire-Phillips Tootle well. The formation has considerable fossiliferous outcrops of shale and sandstone in the Rio Grande V alley near Presidio, and in the basins surrounding the mountains near the lower Conchos Valley along the Kansas City, Mexico & Orient Railway south and west of Ojinaga, Chihuahua. Paleontology.-The only fossils recorded are saurian bones, rep­tilian ( ? ) tracks, and fossil wood. Paleontology of Navarro group.-The lower limit of the Navarro coincides essentially with the junction between the ranges of Placen­ticeras and Sphenodiscus. In Medina and Travis counties, Spheno­discus lenticularis is reported from strata currently called highest Taylor (highest typical Exogyra ponderosa), and Stephenson re­ports that in the Arkansas formations the lowest Sphenodiscus found is from the Nacatoch sand. In Medina County the Taylor has arbi­trarily been extended about 75 feet above the top of the asphaltic Anacacho coquina, apparently to include all beds carrying Exogyra ponderosa. This throws Bostrychoceras aff. polyplocum, Para­pachydiscus aff. wittekindi, Parapachydiscus aff. gollevillensis, Sphe­nodiscus lenticularis (besides Hoplitoplacenticeras aff. vari, Menuites and Pseudoschloenbachia) into the Taylor. In the face of such an assemblage, it would be difficult to place the age of the upP.er Taylor, as thus construed, much lower than the Campanian-Mae­ strichtian boundary (see Spath, 1510, table opp. p. 80; also 1505, 1506). In the Aguja sándstones and shales, Placenticeras, but no Sphenodiscus, are known, and the upper Taylor ammonites just be­ neath the Aguja at San Carlos demonstrate a lower level than the top of the Taylor in Medina and Travis counties. How much Na­ varro is present in the Aguja remains to be discovered. Among the most distinctive Navarro ostracoda are: Cytheridea fabaforrnis (Berry) Cytheridea micropunctata Alexander Cythere alata (Bosquet) Cythereis comrnunis Israelsky (com· mon; good marker) Cythere rhomboidalis Berry (com· mon; good marker) Cythere ovata Berry Cythereis parallelopora (Alexander) Cytheridea everetti Berry Cytheropteron liannai (Israelsky ) Cytheropteron saratogana (Israelsky) Bairdia magna Alexander Cytherella ovata (F. A. Roemer) Cytherella tuberculifera Alexander Cytherelloidea williamsoniana (Jones) The following list of foraminifera known from the Navarro has been kindly supplied by Helen Jeanne Plummer, the most charac­teristic species being marked by asterisks: Proteonina diffulgiformis (H. B. Brady) Reophax texana Cushman and Waters Ammodiscus incertus (dürbigny) Haplophragmoides calcula Cushman and Waters .Haplophragmoides excavata Cush­man and W aters '*Haplophragmoides glabra Cushman and Waters '*Haplophragmoides rugosa Cushman and Waters "'Ammobaculoides navarroensis Plum· mer S piroplectammina anceps (Reuss) *Verneuilina bronni Reuss Gaudryina rugosa d'Orbigny Gaudryinella spp. Clauvulina insignis Plummer Dorothia bulletta ( Carsey) Quinqueloculina sp. Massalina cretacea (Reuss) Trochammina diagonis ( Carsey) '*Trochammina gyroides Cushman and Waters '*Trochammina texana Cushman and Waters Lenticulina navarroensis (Plummer) Lenticulina spp. *Astacolus dissonus Plummer Hemicristellaria ensis (Reuss) *Hemicristellaria silicula Plummer Saracena1ia italica Defrance *Vaginulina gracilis Plummer var. cretacea Plummer Vaginulina multicostata Cushman *Vaginulina simond&i Carsey Vaginulina strigillata (Reuss) Vaginulina webbervillensis Carsey Vaginulina aff. cristellarioides Reuss Marginulina elongata d'Orbigny Dentalina communis d'Orbigny Dentalina crinita Plummer Dentalina granti Plummer Dentalina megapolitana Reuss Dentalina obliqua (Linné) Dentalina reussi Neugeboren Dentalina spinescens (Reuss) Dentalina spinulosa (Montagu) Nodosaria affinis Reuss Nodosaria radicula (Linné) Nodosaria vertebralis (Batsch) Nodosaria cf. adolphina (d'Orbigny) Nodosaria spp. Pseudoglandulina sp. Lagena hispida Reuss Lagena sulcata (Walker and Jacob) Flabellina interpunctata von der Marck The Geology of Texas-Mesozoic Systems 511 *Flabellina reticulata Reuss *Loxostoma eleganta (Plummer ) Frondicularia archiaciana d'Orbigny (Midway) *Frondicularia clarki Bagg Loxostoma plaitum (Carsey) Frondicularia cf. gracilis Franke Loxostoma plaitum (Carsey) var. *Globulina lacrima Reuss limbosum Cushman *Globulina lacrima Reuss var. sub­Loxostoma tegulatum (Reuss) sphaerica (Berthelin) *Siphogenerinoides plummeri Cush­*Globulina lacrima Reuss var. hor­man rida Reuss *Uvigerina seligi Cushman Guttulina problema d'Orbigny Reussia sp. *Pseudopolymorphina cuyleri Plum­Pleurostomella subnodosa Reuss mer Discorbis correcta Carsey *Pseudopolymorphina mendezensis *Epistomina caracolla (Roemer ) (White) *Epistomina aff. reticulata (Reuss) Nonionella robusta Plummer Siphonina prima Plummer *Heterohelix spp. Gyroidina depressa (Alth) Guembelina excolata Cushman Gyroidina girardana (Reuss) Guembelina globulosa (Ehrenberg) 'Ceratobulimina cretacea Cushman Guembelina striata (Ehrenberg) and Harris Guembelina spp. *Pulvinulinella aff. subperuviana Pseudotextularia varians Rzehak Cushman Ventilabrella eggeri Cushman Allomorphina trigona Reuss Ventilabrella carseyae Plummer Pullenia quinqueloba (Reuss) Planoglobulina sp. *Globigerina lacera (Ehrenberg) Eouvigerina hispida Cushman *Globigerina rugosa Plummer *Turrilina sp. Globigerinella voluta (White) Bulimina obtusa d'Orbigny Globotruncana arca (Cushman) *Bulimina aculeata d'Orbigny (Mid­Globotruncana canaliculata (Reuss) way) var. ventricosa White *Neobulimina cf. canadensis Cush­Globotruncana fornicata Plummer man and Wickenden Anomalina grosserugosa (Gümbe]) *Bolivina decurrens (Ehrenberg) Anomalina pseudopapillosa Carsey *Bolivina watersi Cushman *Cibicides aff. ungeriana (d'Orbigny) Cushman (Contr. Cushman Lab. Foram. Res., 8:89, 1932) states that Gaudryina navarroana Cushman and Gaudryinella pseudoserrata Cushman are excellent markers for the Navarro clay above the Nacatoch sand. Records of comrnon Navarro fossils Arkansas East and o s Central ·;¡ .g O:l ~ Texas ;:;¡" ~ Escoo­ ~o~~-5 ~ dido ~ '"·;-º~;~C!. u -:5 ~ ," . .. °2 ~ >.. .... E (f'JZ <;t Z ~ L M z ~ "' Sphenodiscus lenticularis .............................. ? • S. pleurisepta ·········-····-··-··························-­ S. beecheri ---··········-················-·········--···· * S. aberrans ·····················-····-···········-···-······· S. lobatus ···-···-·············-···-··········-····-········ S. prepleurisepta ------·-·-···-·····-··········-········ • S. interrnedius ··········-···-···-····-····-············ * S. n. SP·-·········-···-·····-···-·····-··········-····-········ ? S. stantoni ···-····-···········-··········-··------········· • ~~~h~f~:~s c~:?ns~· -~~::::=.-=:=:::::::=:=:=:::::::::: C. orynskii ··········-····-··········-····················--··· * Arkansas East and 8 e Ce nt ra l ·¡¡ ·~ o ~ Texa2 ~ ~ .g Escon -E ~ ~ ~ dido ~ ~ o. o ~ ~ ] ~ E ~ ~ ·~ ~ o ~ z < z z ~ L M u z < • C. sheltoni -----·-···--····-····-···-····-····-··-····· Parapachydiscus n. sp. L._____________________ P . n. sp. 2 -·-·-···-·-·-···-···-····-------------·­ P. aff. colligatus..-----------------···-··· Nostoceras spp. ---------------------·-·-·-·------• 9~:~1~!,~~:~~~,,sp¿ipp:··-=::::=:::::::::=:::::=:::_-::=::: • Baculites spp. ------------···--···-··----·-----• • Scaphites spp. ···--····--·---------·--------------·-·-• Placenticeras spp. ------------------------­• Belemnitella americana ----------------··---------• • Nautilus spp. ----··--------·--------------------• • auvagesia --------------------·------? P ycnodonta vesicularis -------·--·-·--------• Exogyra costata Say____________ __________ • E. costata (narrow costae) ---------·-------­ E. spinosa Stephenson..___________________ E. cancellata Stephenson_____________________ * • Gryphaeostrea vomer --------·-·---·-·--­ Ostrea falcata -·-·-·--------------·------­• Ostrea owenana --------------------------­ Ostrea tecticosta -------··------------------- Pecten argillensis Conrad___________________ Pecten simplicius Conrad_______________ • Crenella serica -----------------··---------- Inoceramus aff. barabini...____________ lnoceramus spp. ----------·------------------ Veniella conradi Morton___________________ * • Cyprimeria depressa Conrad______________ ? Paranomia scabra_________________ * Lio pistha protexta ----------------------* • Anatimya antiradiata -------------------·-* Tunitella trilira___________________________ • Turr. cf. quadrilirata______________________ Liopistha (Cymella) bella_________________ Cardium (Pachyc.) spillmani_________________ * Pecten mississippiensis ---·--··------------·· • Ostrea aff. pratti_______________________________ Ostrea plumosa ---------------·-----------·­ Ostrea mesenterica ---·-----------------­• Cyprimeria densata ----------------------------·-• Trigoi;iia aff. eufalensis__________________________ Anomia argentana ------------------------------­ Stephenson states (1535a, p. 493) that the following are among the more conspicuous and useful of the species present in the upper Navarro but ahsent or rare in the Exogyra cancellata subzone (basal Navarro clays) : Trigonia eufaulensis Gabb Dreissensia tippana Conrad Pulvinites argentea Conrad Liopistha protexta Conrad Crenella serica Conrad Crassatellites subplana (Conrad) Pholadomya littlei Gabb Cardium stantoni Wade The Geology of Texas-Mesozoic Systems 513 Cardium tippanum Conrad l\forea cancellaria Conrad Cardium dumosum Conrad Liopeplum liodermum (Conrad) Cardium kummeli Weller Ringicula pulchella Shumard Aphrodina tippana Conrad Scaphites conradi Morton + vars. Turritella vertebroides Morton Sphenodiscus (severa! species) Sargana stantoni (Weller) Belemnitella americana (Morton) EXTRUSIVES ABOYE TORNILLO CLAYss Above the Tornillo, extrusives outcrop in two areas: the Chisos Mountains, and the Rim Rock near San Carlos. The age of the basal part of the extrusives is unknown, but there is no evidence that it is Cretaceous. Certain volcanic beds in the Trans-Pecos region are dated as Cenozoic, on the evidence furnished by teeth, bones, plants, and gastropods. Chis os M ountains area.-:--Vdden (1626) described as "Chisos beds" about 2000 feet mostly of tuffaceous sediments, which occur in persistent thin, evenly bedded strata. Accessory materials are thin strata of clay, conglomerate, and cross-bedded, ripple-marked sandstone. No fossils are known from the Chisos beds. They are capped by the Crown conglomerate (1626, p. 66), consisting of three heavy ledges of conglomerate totaling about 60 feet thick, composed of well-rounded pebbles and boulders of trap rock, lava, and Comanche limestones, interbedded with materials like Chisos tuffs. In both Tornillo and Chisos beds, considerable bentonite results from decomposition. Rim Rock area.--.:Vaughan ( 1687, p. 77), has includect the vol­canics above the San Carlos coals in his "Vieja series." lt consists of about 1925 feet of extrusives up to and including the pantellerite. Baker ( 44, 46) has suggested the following sequen ce in Trans-Pecos Texas: (5) Basalts (interbedded with, or later than, the "Santa Fe" lake beds; Pliocene? ) ( 4) Andesites (3) Trachytes (2) Pantellerite-paisanite ) Vieja series of Vaughan (1687). rHyracodon ( Oligocene) on Casey ranch; (1) Rhyolites Wilcox (?) plants in Barilla 1ountains J (Berry, 104). G6Literature.-Streeruwitz, 1560, 1561, 1564, 1566; Osann, 1160, 1161, 1162; Lord, 1014; Vaughan, 1687; Durnble. 480; Udden, 1626; Baker, 44, 46, 53; Ma.nsfield, 1035c; Phillips, 1208; Turner. 1618, 1619; Hill, 722; Berry, 104. Non-marine gastropoda have been collected from points west of the Mount Ord range southeast of Alpine and from the Fletcher (02) Ranch south of Alpine, in Tertiary felsites and conglomerates. Dr. Junius Henderson examined material consisting of large and small gastropods of more than one species, from the latter locality, and reported as follows: 67 The large snails are certainly congeneric and almost certainly specifically identical with the snail that Prof. Cockerell described as Helix hesperarche.68 ... The fossil was labelled "either Puerco or Torrejon, probably Torrejon," to which Cockerell added, in brackets, ["New Mexico"]. He informs me that it was assumed to be from N ew Mexico hecause it is from the Cope collection and Cope was known to have fossil mammals from the Torrejon or Puerco. 1 do not know whether the lahel was in Cope's writing or was written by someone else, hecause the matrix resembled early Tertiary from New Mexico. • • • Cockerell says your specimens look exactly like the American Museum material. .. The difficulty is that Cope's specimen may have come from your locality instead of from New Mexico, [as] Sternherg, who did much collecting for Cope, obtained rich collections from Texas red heds and may have visited other localities. Non-marine gastropods like Planorbis occur at the Casey ranch, at the northeastern foot of the Davis Mountains, within 200 feet of the base of the volcanics. IGNEOUS ROCKS IN TEXAS CRETACEOUseu The igneous occurrences within Cretaceous rocks in Texas · are grouped ~ostly in two areas, Trans-Pecos Texas, and the Coastal Plain south and east of the Balcones fault. No igneous rocks of Cretaceous age have been reported from Trans-Pecos Texas except, doubtfully, sorne ultra-basic lavas in a large syncline southeast of the Marathon Basin (C. L. Baker) , and the age of these rocks is still unknown. Other extrusives and intrusives (flows, stocks, plugs, sills, dikes) in Cretaceous formations in this area are thought to be of Tertiary age, and are discussed later in this paper. 17Letter, to the writer, July 11, 1929. 98Cockrell, T. D. A., Tertiary mollusca from New Mexico and Wyoming: Bull. Am. Mua. Nat. Hist., 33: 104, pi. 10, .6.gs. 1-3, 1914. Helix is used in the broad sense. 69Literalu.re.-Basaltic rocks : Getzendaner, 578, 578a; Hill,: 757, 765, 793; Hill and Vaughan, 795, 808; Lonsdale, 1009; Sellards, 1429. Dikes: Dawson, Hanna and Kirby, 398; Lonsdale, 1009; Sellards, 1429. Sills: Lonsdale, 1009, pp. 39-41. Ash, tufj and bentonite: Ross, Mi1er and Stephenson, 1353; Ross and Ke.rr, 1353a ; Getzendaner, 578. Ser"pentines : Bybee, 187; Byhee and Short, 188; Collingwood, 268; Collingwood and Retger, 267; Getzendaner, 578; Lahee, 971; Lons. dale, 1009; Sellards, 1422, 1444a; Schoch, 1376; Schoch and Reed, 1377; Udden, 1638, 1639a; Udden and Bybee, 1641. The Geology of Texas-Mesozoic Systems 515 In south and central Texas, the known igneous bodies occur along the Cretaceous outcrop gulfwards from the Balcones fault zone. How­ever, the Upper Cretaceous in northeastern Texas and southwestern Arkansas contains volcanic ash and bentonites (1353); and other igneous bodies will likely be found with further drilling in the Coastal plain. The known occurrences in the Cretaceous may be grouped as follows: l. lntrusive basaltic rocks: Stocks or plugs of basalts (olivine-basalt, nephelite-melilite-basalt, limburgitic rocks, gabbro) and of phonolitic rocks (phonolite, nephelinite, Uvalde phonolite) occur in a narrow belt from Austin to near Brackettville, along; and gulfwards from the Balcones fault zone (1009). The youngest formation cut by them is Pulliam, and Lonsdale is of the opinion that the age of the massive intrusions in this belt is Tertiary (1009, p. 44) . Sorne such bodies, however, were exposed and weathered in Eagle Ford, Austin and Taylor times, and left sedimentary serpentines in those formations. 2. Dikes and sills: A few dikes are known in Glen Rose or Edwards outcrops in Travis, Comal, Bandera, Medina· and possibly Uvalde counties. Lonsdale thinks these bodies may also be of Tertiary age (1009, p. 42). Surface sills occur in Kinney and Uvalde counties, and sills are known in wells in Travis and Zavala counties. Dikes in Bandera County were described (636) in 1888. 3. V olcanic ash and bentonite: Clays of volcanic origin occur as interbedded scdimentary deposits in the Woodbine (1353), Eagle Ford, Austin, Taylor and Navarro (1009, p. 46) groups. 4. Serpentine: Lonsdale (1009, pp. 139-149) divides the serpentines of the Balcone& fault area into three classes. They are: a. Weathering residues of basaltic rocks. Examples are the serpentines at Knippa, Uvalde County, at Pilot Knob, Travis County, and at the locality three-fourths mile upstream frorn Black W aterhole, Uvalde County. b. Sedimentary serpentine. This is interbedded with other sedirnentary rocks, of Eagle Ford, Austin, and pechaps other Upper Cretaceous ages. Examples are Pilot Knob and Black Waterhole. On Onion Creek north of Pilot Knob, this sedimentary igneous material contains lnoceramus and other Austin fossils. The tops of sorne serpentine "plugs" in the oil fields mentioned later contain foraminifera, and appear to be sedimentary; this conclusion how· ever does not apply to the entire body of such "plugs." c. Volcanic serpentine. These bodies, as found in Lytton Springs, Thrall, and othel'. Coastal plain oil fields, are low eones of large size. Many writers have considered these bodies as extrusive, either onto the floors of Upper Cretaceous seas or onto low-lying emerged areas. Serpentine of this type occurs at *Buchanan, *Chapman, *Dale, *Lytton Springs, *Lytton Springs townsite, *Schimmel-Batts, *Thrall, *Yoast, Kimbro, Darst Creek and in Uvalde, Medina, Zavala and Travis counties (578, 1009, 1444a). *Aster:sks indicate oil fields producing from serpentine. NOTE ON SUBDIVISIONS OF NAVARRO GROUP Dr. Stephenson suggests that the basal Navarro clays (Exogyra cancellata zone) below the Nacatoch he called Neylandville formation, and that if the name Kemp beds of Hill is retained, as in this paper, for the portion of the Navarro above the Nacatoch sand, the lower part (chalky marl) of the Kemp be separated as the Corsicana formation (restricted). It appears from Hill's description that he included in his "Corsicana beds" the Navarro clays helow the Nacatoch, the Nacatoch, and a portion at least of the chalky marl. Dr. Stephenson says: 10 "The name Neylandville would be an appropriate one to apply to the unit which 1 have heretofore called Exogyra cancellata zone. This zone in· eludes all the heds hetween the Taylor marl below and the Nacatoch sand above. Exposures of the materials comprising the zone occur in washes in a field j ust south of the fair grounds at the southeast edge of Greenville, and in ditches along the Dixon road for a mile or more southeast of the fair grounds. Type exposures occur along the Bankhead highway between Liberty School and N eylandville, 3 to 6 miles in an air line northeast of Greenville, and in the first cut of the Texas Midland Railway west of Neylandville station. "The Kemp formation, as used by the Bureau of Economic Geology in this report, includes the units which 1 have called the chalky marl meniber and the upper clay member. Since the chalky marl member underlies the city of Corsicana, it would be appropriate to restrict the name Corsicana to the chalky marl unit. As Hill originally used it, the "Corsicana" probably inclúded the Exogyra cancellata zone, the Nacatoch sand, and the chalky marl. The pit of the Corsicana Brick Company 2 miles south of the court house at Corsicana, might appropriately be regarded as the type locality. If the name Kemp is retained, it should be restricted to the upper clay member, but expostues of this are rare in the vicinity of Kemp, and the desirability of applying the name to this unit has not been fully considered. "The names Neylandville, and Corsicana (restricted) have not as yet been formally adopted by the United States Geological Survey." CLOSE OF CRETACEOUS IN TEXAS Most writers on the Navarro have mentioned that a hiatus or un­conformity of unknown magnitude marks its top. Locally various Tertiary formations as high as the Indio overlap onto the Na­varro, and the extent of highest Cretaceous strata which these over­laps conceal is unknown. It is stated that at different places he­neath the Tertiary overlap Navarro of differing ages appears on the outcrop. Thus Stephenson indicates that about the upper half of the Escondido is younger than any Navarro in central Texas (1534, Pl. 1), a view expressed also by other writers. At the pres­ '1oPereonal communication, March 6, 1933. The Geology of Texas-Mesozoic Systems 517 ent time, lack of an adequate zonation of the Navarro, surface and underground, prevents a clear answer to this question. The Es­condido in Nuevo Leon contains Coahuilites and other ammonites not yet found on the American side of the Río Grande, but whether this lack represents a difference of age, of facies, or insufficient col­lecting, remains unknown. Scott (1389, 1390) has attempted to correlate the basal Midway with Danian, and therefore add it to the Texas Cretaceous. This cor­relation depends on the affinities of H ercoglossa vaughani, V eneri­cardia bulla and other Midway species, and is discussed later under the "Midway group." (See Plummer, Jour. Pal., 4:207, 1930; and Gardner, 572.) Late Cretaceous time was marked by elevation of the land and retreat of the sea in central Texas, and early Tertiary by a new transgression of the sea. The interval between Cretaceous and Ter­tiary is therefore marked, on the outcrop, by an unconformity, which may extend down-dip a great distance, by various physical signs, and by a practically complete break in the megafauna. It is possible that down-dip and underground this gap is partly or entirely filled, but so far no such place is known. The top of the Navarro is not of the same age at different places for two reasons. The sea retreated earlier in sorne areas than in others: in Trans-Pecos Texas, where the sandy and near-shore Aguja formation represents upper Taylor and prO:bably Navarro; in northern Mexico, where Bose and Cavins described brackish (Tulillo) sandstones in the Navarro; in northeastern Sonora, where various Upper Cretaceous shore lines are in evidence. Furthermore, differing amounts of material have been removed from the top of the Cretaceous at various places near the outcrop, although it is probable that higher beds are preserved down-dip. The amount of retreat of the uppermost Cretaceous sea is un­known, but it is improbable that the Taylor and Navarro seas ex­tended much farther inland than the present Balcones fault zone. If they h14d deposited soft sediments over a large area of the Ed­wards Plateau and Osage Plains, and subsequently retreated, the basal Tertiary beds should contain great amounts of relatively fresh Upper Cretaceous materials and fossils; yet this feature is incon­spicuous earlier than the Lissie. A less conclusive argument is that the Anacacho limestone is a near-shore Taylor reef. The physical evidences of unconformity, the locally deep leaching, the break in the fauna, and the fact that the basal Midway is different at different places (clay locally, Lone Oak limestone locally) argue for a dis­tinct period of prohably subaerial erosion. Fig. 27. Mouth of Santa Helena canyon of Rio Grande, 10 miles south of Terlingua. The wall is 1700 feet high, and is composed mostly of Freder­icksburg limestone. Part 3 CENOZOIC SYSTEMS IN TEXAS F. B. Plummer lNTRODUCTION ECONOMIC IMPORTANCE OF CENOZOIC STRATA Cenozoic rocks furnish a large proportion of the natural re­sources of Texas. The soils developed from these strata support extensive forests of pine and hardwood timher, which constitute the chief supply of lumher. The clays make a good quality of brick and tile. Salt plugs, which have reserves of salt estimated by Barton (69, p. 49, 1928) to be 1,170,000,000 long tons above a depth of 2500 feet, occur within the area covered by Cenozoic strata. More than 700,000,000 barreis of oil have been produced from sands of Cenozoic age along the Gulf Coast and in south Texas. Barton (69, p. 23, 1928) estimates that over 500,000,000 barreis of known recoverable oil are still in the ground, and that three times as much is yet to be discovered. Available sulphur de­posits in strata of Texas and Louisiana Gulf Coast amount to at least 90,000,000 tons. Lignite occurs in many places also. Baket (MS.) estimates that these reserves amount to 30,000,000,000 tons and points out that the lignite is the cheapest and most abundant source of future electric power in the state. Lignite is capable, by the process of hydrogenation, of furnishing an almost inexhaustible supply of gasolene and lubricating oils. The low-grade iron ore occurs in great abundance in the middle Eocene strata of east Texas. Cenozoic strata contain high-grade clay for the manufacture of brick, tile, and pottery, and volcanic ash altered to fuller's earth, which is extensively used as a filtrant for oils. The shallow sands furnish water supply for thousands of homes, and in certain areas in south Texas underground water is present in sufficient quantities to irrigate thousands of acres of truck gardens and valuable agri­cultura! land. The U. S. Geological Survey estimates that more than four-fifths of the people of east and south Texas are supplied with drinking water from wells. The supplies of lumber, oil, lig­nite, salt, sulphur, and underground water are more than sufficient to give these formations first place in natural reserves among the major geologic groups. GEOLOGIC INVESTIGATIONS The first puhlished announcement in American literature of the presence in Texas of strata helonging to the later geologic periods appears to have been by William Maclure,1 who compiled a geologic map of the United States. In his observations that accompanied the map he referred to the unconsolidated sediments of the coastal province as alluvial rocks. In 1824 John Finch2 suggested that Maclure's alluvial formation was identical with the Tertiary for­mations of Europe. The first fossils from the Cenozoic strata of the Gulf Coast were described by Say,3 Conrad,4 and Lea.5 Featherstonhaugh,6 in his report of an examination of the country between the Missouri and Red rivers, was one of the first geologists to describe strata of Cenozoic age on the west side of the Mississippi embayment. During 1845, 1846, and 1847 Ferdinand Roemer, a German geologist, visited Texas in the interest of German colonization and published nine papers between 1847 and 1889 giving an account of his geological observations (1327, pp. 358-365, 1846; 1328, pp. 21-28, 1848; 1330, pp. 1-464, 1849; 1331, pp. 1-100, 1852; 1335, pp. 281-296, 1888). Roemer (1330, 1849) prepared the first map to show the Cre­taceous-Eocene contact in Texas. He7 noted also fossiliferous Eocene rocks in Robertson and Caldwell counties. In 1857 Schott (1380, pp. 28-48, 1857) published an account of the geology of the formations along the lower Rio Grande and illustrated a f ew Eocene fossils. Gabb (555a, pp. 375-406, 1860) published a paper 1Maclure, Wm., 103la, pp. 411-428, 1809. 2Finch, John, Geological essay on the Tertiary formations in America: Amer. Jour. Sci., first ser., vol. 7, pp. 3143, 1824. 3Say, Thomas, An account of sorne of the fossil shells of Maryland : Acad. Nat. Sci. Pbila. delphia Jour., vol. 4, pp. 124-155, pis. 7-13, 1828. 'Conrad, T. A., Fossil shells of the Tertiary formations of North America, pp. 1-121, pis. 1-20, Philadelphia, 1832, 1835. 5Lea, Isaac, Contributions to geology; Tertiary formation of Alabama, pp. 1-208, pls. 1-6, 1833. (Lea received his first Tertiary fossils from Judge Tllt of Claiborne, Alabama, in January, 1829.) 6Featherstonhaugh, G. W., Geological report of an examination made in 1834, of the elevated country between the Missouri and Red rivers, pp. 1-97, Washington, 1835. 7An interesting account of Roemer's travels in America has been published recently by S. W. Geiser (572c, pp. 421-460, 1932). The Geology of Texas-Cenozoic Systems 521 on a collection of Eocene fossils obtained near Wheelock, Robert­son County. From 1861 through the seventies, due to the Civil War and its effects, no noteworthy contributions to Cenozoic geology were made except by Hilgard. In 1860 Hilgard8 completed a publication on the geology of Mississippi, in which he devoted 86 pages to the description of the Cenozoic strata, and published new sections and many lists of fossils. In 1869 he (721a, pp. 331-346, 1869) visited Louisiana and published the results of hís observations in which he teviewed the geology of the younger formations of the state. In 1871 he published9 a paper on the geological history of the Gulf of Mexico. In 1873 he10 completed his final report on the geology of Louisiana, which was the most complete report of the Cenozoic geology published up to that time. Other noteworthy articles by Hilgard concern lignite beds and their under clays, the later Ter­tiary of the Gulf of Mexico, and an account of the old Tertiary of the Southwest. Altogether Hilgard dominated geological inves­tigations on the Cenozoic formations between 1860 and 1885. Beginning about 1885, however, interest in the coastal section was renewed by a number of new accounts of the geology. Note· worthy among these are those by Loughridge (1017, pp. 669-806, 1884), who published the first account of the occurrence of older Eocene (Midway) fossils in the Tehuacana Hills, Limestone Coun­ty; Heilprin (701, pp. 393-406, 189I), who published descriptions of Eocene mollusca of Texas; and Hill (734, pp. 1-95, 1887), who presented a summary of all that was known at the time concerning the geology of the state. The first detailed accounts of the younger strata of Texas carne in 1890 and succeeding years, as a result of the work of the Dumble Survey in Texas and the Smith Survey in Alabama. Penrose (1189, pp. 3-100, 1890) published a report on the geology of the Gulf Tertiary of Texas, and Kennedy published severa! reports dealing with Tertiary strata (903, pp. 65-203,)891; 904, pp. 3-40, 1892; 905, pp. 41-125, 1892; and 906, pp. 1-84, Sffilgard, E . W., 'Geology and agriculture of the State of Mississippi, pp. 1-391, Jackson, Misaiuippi, 1860. ºHilgard, E. W., On the geological history of the Gulf of Mexico: Am. Jour. Sci., 3rd ser., vol. 2, pp. 391--404, 1871. lOffilgard, E. W ., Supplementary and final repon of a geological reconnaissance of the State of Louisiana, 44 pp., 1873. 1893). In 1894 Smith, Johnson, and Langdon11 published the most complete account of the geology of the southern Gulf Coast. During the same epoch Dumble, as director of the Geological Survey of Texas and later as chief geologist for the Southern Pacific Railroad, took much interest in Cenozoic geology and deserves much credit for his own researches as well as those carried on by his assistants. His numerous publications have contributed much to the knowledge of Cenozoic stratigraphy and have had much in­fluence on later geologic work. He published a report (470, pp. 1-243, 1892) on the brown coal and lignites of the Eocene forma­tions; an account (478, pp. 549-567, 1894) of the Cenozoic de­posits of Texas; notes ( 481, pp. 23-27, 1895) on Texas Tertiaries; a treatise ( 487; vol. 2, ·pp. 471-516, 1898) on the geography, geol­ogy, and natural resources of Texas, in which much space was de­voted to the younger formations; an account (494, pp. 913-987, 1903) of the geology of southwest Texas; two papers (497, pp. 50­51, 1911; 498, pp. 52-53, 1911) dealing with Eocene beds; a dis­cussion (501, pp. 447-476, 1915) of the Texas Tertiary sands, and a comparison (502, pp. 481-498, 1915) of the geology and stratig­raphy of northern Mexico with southern Texas; another summary (503, pp. 125-204, 1916) of the geology of Texas; a bulletin (506, pp. 1-388, 1918) on the geology of east Texas containing a new map of the Cretaceous and Cenozoic formations; and finally, a revision (510, pp. 424-444, 1924) of the Texas Tertiary geologic section with special reference to the subsurface strata revealed in oil wells. Altogether Dumble contributed more to the Texas Ceno­zoic literature than any other geologist. The first paper dealing exclusively with Texas Tertiary fossils was written by Heilprin (701, pp. 393-406, 1891). This good begin­ning was followed soon by a series of notable papers on Tertiary paleontology by Harris: Tertiary Geology of Southern Arkansas (660, pp. 1-206, 1894); Neocene Mollusca of Texas (661, pp. 83-114, 1895); Midway Stage (662, pp. 115-270, 1896); New and Otherwise Interesting Tertiary Mollusca from Texas ( 663, pp. 45­88, 1896); Lignitic Stage, part 1 (664, pp. 193-294, 1897); Lig­nitic Stage, part 11 (664a, pp. 1-128, 1899); Pelecypoda of the 11Smith, E. A., Johnson, L. C., and Langdon, D. W., Jr., Report on the geology of the Coaotal Plain of Alabama: Geol. Survey Alabama, pi. l , pp. 1-445, 24 pis., 1894. The Geology of Texas-Cenozoic Systems 523 St. Maurice and Claiborne Stages (668a, pp. 1-268, 1919). During this interval Aldrich (23, p. 25, 1890; 24, pp. 53-82, 1895; 26, pp. 1-26, 19ll), DeGregorio (406b, pp. 1-316, 1890), W. B. Clark (251a, pp. 1-173, 1891), Otto Meyer,12 and Dall (387, pp. 1-200, 1890) added notable contributions to the paleontology of the south­ern Gulf Coast Tertiary formations. Since the work of Harris and his contemporaries, most of the publications on the Cenozoic of 'fexas, except those of Dumble al­ready mentioned, have come from the pens of geologists of the United States Geological Survey in the form of Water-Supply and Professional Papers. Thus, Veatch (1691, pp. 1--422, 1906) has described the underground waters and geology of east Texas, north­ern Louisiana, and southern Arkansas. Deussen ( 415, pp. 1-365, 1914; 421, pp. 1-145, 1924); Deussen and Dole (416, pp. 141-177, 1916) ; Gordon ( 609, pp. 1-78, 19ll), and Trowbridge (1610, pp. 85-:..107, 1923) have described the geology and underground waters of southeast, southwest, and northeast Texas. Berry has described the fossil floras (101, pp. 227-251, 1916; 103, pp. 1--481, 1916; 109, pp. 87-92, 1924; and 112, pp. 1-196, 1930). Stephenson (1528, pp. 155-182, 1915) described the Cretaceous-Eocene contact in Texas, and Julia Gardner (565, pp. l09-ll5, 1923; 566, pp. 141-145, 1924; 567, pp. 134-138, 1925; 569, pp. 245-:..251, 1927; 570, pp. 362-383, 1927; 572, pp. 149-160, 1931; 572a, p. 470, dis­cussion, 967-970, 1931) in connection with her work on a new geological map of Texas has studied the stratigraphy and paleon­tology of the Cenozoic strata and deserves much credit for complet­ing a large task in a very difficult field. She has untangled a mass of conflicting ideas and has placed Texas stratigraphy on a firmer foundation. The recent work of the paleontologists of the southwest in ad­vancing the science of micropaleontology must be mentioned as an important ítem in any review of Cenozoic stratigraphic research. The knowledge gained from a study of the foraminiferal faunas has furnished a new, accurate, and very important tool to aid in the mapping and the correlation of formations. Esther Applin, Alva Ellisor, and Hedwig Kniker (32, pp. 79-122, 1925) in a 12Meyer, Otto, Species in the southern old Tertiary : Am. Jour. Sci.• vol. 30, pp. 270-275, Oct., 1885. paper on the suhsurface stratigraphy of the Coastal Plain proved the value of microfossils as a means of identifying and correlating underground strata in Texas. Helen Jeanne Plummer (1235, pp. 1-206, 1927) in a paper on the foraminifera of the Midway has shown the value of these fossils for zonation of Cenozoic forma­tions and their value in surface mapping. Cushman and Applin (352, pp. 154-189, 1926) and Cushman and Thomas (374, pp. 176-184, 1929, and 379, pp. 33-41, 1930) have descrihed the forarninifera of the Jackson and Claihorne (Eocene) groups. Other recent helpful contrihutors to Texas Cenozoic stratigraphy are Bailey ( 40, pp. 1-187, 1926), who descrihed excellently the vol­canic tuffs of south Texas; Alva Ellisor (522, pp. 976-985, 1926), who wrote on Oligocene coral reefs, and ( 523, pp. 1335-1346, 1929) on the correlation of the Claihorne; Wendlandt and Knehel (1728, pp. 1347-1375, 1929), who have given the hest account of the lower Claihorne of east Texas; Renick and Stenzel (1299, pp. 73-108, 1931), who descrihed the lower Claihorne along Brazos River Valley; and Ball (58, pp. 1-173, 1931), who has added to the knowledge of the paleobotany of the Eocene formations. GEOGRAPHIC EXTENt Cenozoic formations are widespread in Texas. The outcrop covers a broad belt of territory along the Gulf of Mexico from Florida to Mexico. These formations outcrop along the Coastal Plain in an irregularly shaped belt, which includes most of the eastern part of Texas. The northern limit is a line drawn through points located 210 miles up Rio Grande Valley, 190 miles up Colo­rado River, and nearly 300 miles up Sahine River and its trihu­taries. A few small patches of nonmarine Cenozoic strata have been iden­tified in west Texas. West of the Pecos there are extensive intru­sions of Cenozoic igneous rocks, ancient flows of Cenozoic lava, and heds of volcanic ash. Clays that contain leaves of Cenozoic plants, fossilized snail shells, and bones of animals are found interstrati­fied with the ash heds in a few places. Cenozoic strata cover more than one-third of the surface of the state and are developed in a wide and diverse variety of facies and structure, exceedingly interesting scientificaIIy· and very important economically. The Geology of Texas-Cenozoic Systems 525 RELATION OF REGIONAL STRUCTURE TO DISTRIBUTION OF OUTCROPs1a Regional structure has had two marked effects on the extent and character of Cenozoic formations. First, the uplifts and basins determined the facies of the sediments and lithology of the forma· tions. The waters were deepest and the sea remained longest in the synclinal areas. Most formations in the middle of the troughs are made up of fine-grained marine muds and silts. Traced laterally Fig. 28. Structural features in the Gulf Coast province of Texas and adjoin­íng states. "'LtTERATuRE-Veatch, A. C., 1691, pp. 61Hí9, 1906. Fohs, F. Julius, 543, pp. 70~721, 1923. Pratt, Wallace E., aod Lahee, F. H., 1263, pp. 226-236, 1923. Powers, S., 1252, pp. 20~268, 1926. Lahee, F. H., 969, pp. 303-388, 1929. Weodlaodt, E. A., 1728, pp. 1347-'1376, 1929. Heath, F. E., aod Waters, J. A., 6%, pp. 43-@, 1931. Moody, C. L., 1125, pp. 531-551, 1931. toward an uplift, the same strata change to coarser sediments of littoral origin and merge with continentál sediments having so dif· ferent an aspect that geologists have assigned in sorne cases two names to the same formation. Second, the shape of the trough in which. the sediments were deposited and the shape of the local ah­ normal structures in the hasin controlled the shape of the shoreline and extent of the deposits. The outcrops of nearly all the forma· tions hroaden and extend landward in the hasin areas, narrow and hend gulfward around the arches and uplifts, are repeated or widened by the faults having upthrow sides on the southeast, and are displaced, punctured, and hroken by the salt plugs. The Gulf Coast structural features that have had most effect on Cenozoic geology are as follows: l. Mississippi embayment 2. Sabine uplift 3. East Texas basin 4. East Texas salt domes 5. Nortbeast Texas fault system: a. Balcones or Cretaceous group of faults b. Mexia·Powell or Midway group of faults c. Mt. Enterprise or. Claiborne group of faults 6. Gulf Coast salt domes 7. San Marcos arch of the Llano uplift 8. South Texas fault system: a. Balcones or Cretaceous faults b. Midway group of faults c. Pettus or Claiborne group of faults 9. South Texas salt domes 10. ueces valley trough 11. Chittim arch 12. Sierra Madre line of folds. The location and extent of these features is shown on the map~ figure 28, and their effect on the width and trend of the outcrops can he studied on the geologic map of Texas and on detailed map& of the faults and salt domes. HISTORY OF SEDIMENTATION The outstanding feature in the history of Cenozoic sedimentation in Texas is a continuous and relentless struggle hetween the en­croaching ·waters of the Gulf and heavily loaded, large streams. The Geology of Texas-Cenozoic Systems 527 The sea endeavored to advance over the land, and the rivers con­stantly tried to build seaward a newly deposited land in the forro of a deltaic plain.14 In sorne epochs the water forces prevailed, in others the land-building processes predominated. During the Midway stage, for example, an advance of the sea brought far inland a marine sedimentary facies and marine fossils. During the Wilcox stage, river-laid sands were extended far seaward, and a continental facies of sediments containing land plants and a fresh-water fauna was superimposed over the marine strata. The present time appears to mark the end of a long epoch of land building in which the strand line has been pushed seaward to its limit. Drowned valleys, numerous bays, and long tidal areas in the lower stretches of the coastal rivers show a very recent change and indicate a beginning of another sea transgression. The history of the Cenozoic era is a history of the transgressions and regressions of the marine waters, and the correct interpretation of the geology depends upon a knowledge of the remarkable inter­grading and interbedding of the two types of sediments, the con­tinental and the marine, as well as the recognition of intermediate types, the littoral and lagoonal sediments. Not only does one type of sediment replace the other vertically, as the Wilcox land deposits replace the Midway marine strata, but also, if sorne formational units are traced laterally far enough, one facies may grade or change ab­ruptly into another. Thus the lower Miocene strata exhibit a typical land facies on the outcrop in east Texas; followed gulfward beneath younger strata they change to littoral deposits; still deeper they as­sume a typical deep-water marine facies. The same strata traced southwestward into southern Mexico exhibit the marine facies in outcrop. The complicated intergradations of sediments make Cenozoic stratigraphy difficult and correlation of formations uncertain in sorne places. The relationships of the various facies of the forma­tions during the epochs of the Cenozoic era are shown by the diagram, figure 29, which depicts transgressions and regressions of the strand line during Cenozoic history. lt will be noted by re­ferring to the figure that at least nine maximum transgressions of 1'Barton, D. C., (70, pp. 359-382, 1930) in bis excellent account oí recent deltaic sedi­mentation along: tbe Coastal Plain has given the best description of tbe building.-out process. Wills Point­ Kinc.aid Fig. 29. Diagramatic representation of the changes in strand lines during the Cenozoic era. The stippled portion represents land; the blank portion sea. Extension of blank areas to northwest shows advances of seas. Extension of stipled areas to the southeast indicates retreat of the sea. (Modified from diagram by H. B. Stenzel, 58, p. 6, 1931.) The Geology of Texas-Cenozoic Systems 529 the sea occurred, and that each transgression _was followed by a maximum regression, and that during these major changes numerous oscillations of the strand line of greater or less extent took place. These major transgressions divide Cenozoic time into natural divi­sions which form a basis for the classification of the strata into formations. Thus the Wills Point, Reklaw, Weches, Crockett, lower Jackson and marine Miocene mark stages of advancement of the sea and of widespread marine deposits. The Carrizo, Queen City, Sparta, Yegua, Catahoula, Oakville, Goliad, and Lissie mark stages of major withdrawal of the sea and widespread land deposits. These major strand-line changes were most marked in the Mis­sissippi embayment area of Texas, Louisiana, l\Hssissippi, and Ala­bama and were much less persistent outside the embayment. In Mexico and Florida the marginal strips were narrow and have been removed. The succession of strand-line changes with their recurrent sediments have been interpreted as sedimentary cycles by Weller,1~ or as rhythms by Hudson.16 These rhythms have been explained by sorne geologists as due to periodic isostatic adjustments in a geosyncline or embayment following heavy loading with sediments and corresponding removal of material from adjacent land masses,; and by others as due to periodic compaction of clays by dehydration of colloids at depth following long epochs of deposition, the com­paction requiring less time than the deposition and bringing ahout a transgression of water after each long period of filling and water displacement. Whatever the cause, these periodic major strand-line changes have played a very important role in Cenozoic sedimentary history of the Texas region and have brought about the complicated interfingering of the continental and marine facies in the geologic section. CLASSIFICATION The Cenozoic rocks in Texas have been divided into eight groups, .and these divisions subdivided into formations and memhers as follows: lSWeller, J. Marvin, Cyclical aedimentation of the Penneylvanian period and ita significance: Jour. Geol., vol. 38, pp. 97-135, 1930. 16Hudaon, R. C., On the rhythmic succession of the Yoredale series in Wensleydale: Proc. Yorkebjre Ceol. Soc., n. ser., vol. 20, pt. 1, pp. 125-154, 1924. 530 The Uni'versity of Texas Bulletin No. 3232 Classification o/ stratigraphic divisions in Texas *According to United States Ceological Survey usage in 1932. The Geology of Texas-Cenozoic Systems 531 EocENE SYSTEM MIDWAY GROUP11 DEFINITION The name Midway was first applied by Smith and Johnson18 in 1887 to designate the oldest Eocene strata in Alabama. Harris ( 660, p. 12, 1894) used the term in his report on the Tertiary geology of southern Arkansas and again (662, p. 126, 1896) in his bulletin on the Midway stage in which he showed that it was a stratigraphic and paleontologic unit of first rank. In describing the formational divisions of the Austin quadrangle, Hill and Vaughan (808, p. 6, 1902) used the new name Lytton for the lowermost Eocene strata. The term Midway has been adopted generally by ali geologists describing the 'lower part of the Eocene section, so that it is now well established. The type locality is at Midway Landing on Alabama River in Alabama. The Midway includes ali the strata between the Upper Cre­taceous (Navarro and Escondido marls) and the sands of the Wilcox group. The contact with the underlying Cretaceous marls is un­conformable and is marked in most places by a layer of glauconite, or a line of small black cobble-shaped phosphatic nodules, or a thin stratum of glauconitic sand containing polished pebbles and shark's teeth. The unconformable relationship shows plainly in the Río Grande area and in northern Mexico, where, according to C. L. Baker, the contact is marked by water-worn boulders and pebbles and where the underlying Cretaceous beds dip more steeply than the Midway strata. 17SELECTED LITERATURE-Smith, E. A., and Johnson, L. C., Tertiary and Cretaceous strata of the Tuscaloosa. Tombigbee, and Alabama rivers : U. S. Geol. Survey Bull. 43, p. 62, 1887. Penrose, R. A. F., 1189, pp. 19-22, 1890. Kennedy, W., 905, pp. 47-50, 1892. Harria, G. D., 660, pp. 22-54, 1894; 662, pp. llS-270, 1896. Smith, E. A., Johnson, L. C., and Langdon, D. W., Report of the geology of the coastal plain of Alabama: Geol. Survey Alabama, pt. 1, pp. l-445, 1894. Kennedy, W., 911, pp. 144-149, 1896. Veatch, A. C., 1691, pp. 33, 34, 1906. Hill, R. T., and Vaughan, T. W., 808, p." 6, 1902. Deussen, A., 415, pp. 29-37, 1914; 421, pp. 4(}-47, 1924. Dumhle, E. T., 502, pp. 485-486, 1915; 502a, pp. 171-181, 1915; 506, pp. 30-37, 1918. Liddle, R. A., 992, pp. 74-81, 1918. Sellards, E. H., 1402, pp. 54-57, 1919. Trowbridge, A. C., 1610, pp. 88-89, 1923. Hull, J. P. D., Guide notes on the Midway in southwestern Arkansas: Am. Assoc. Pet. Geol. Bull., vol. 9, pp. 167-170, 1925. Cook, Wythe, The Cenozoic formation of Alabama: · Geol. Survey Alabama Bu11. 14, pp. 253-356, 1926. Plummer, Helen Jeanne, 1235, pp. 1-206, pis. 1~15, 1927. Gardner, Julia A., 570, pp. 362-383, 1927, Semmes, Douglae, Oil and gas in Alabama : Geol. Survey AJ.abama Special Rpt. 15, PP• 232-239, 1929. 18Smith, E. A., and Johnson, L. C., Tertiary and Cretaceous strata of the Tuscaloosa, Tom· bigbee, and Alabama rivere: U. S. Geol. Survey Bull. 43, p. 18, 1887. The contact of Midway strata with the overlying basal sand of the Wilcox group is not so sharp as the lower contact, but in most places where exposures are good, it is easily recognized. lt is the line where the thick, irregularly bedded, medium-grained sand of the basal Wilcox succeeds abruptly the evenly laminated silt and silty clay of the Midway. In places the contact is uneven, due to an abrupt change in sedimentation without an intervening period of erosion. The coarse, stream-deposited sand of the Wilcox tended to settle unevenly into the soft, fine, marine silt of the uppermost Midway. SUBDIVISIONS The Midway group has been divided on a basis of differences in facies and faunas into two divisions: Kincaid formation at the base, and Wills Point formation above. KINCAID FORMATION"' Definition.-The identity of the lower portion of the Midway as a separate, easily distinguishable unit was first recognized in 1924 by oíl geologists mapping the structure of the Mexia-Powell fault line. It was named Barrows member of the Midway by F. B. Plum­mer (MS., 1924), basal Midway by H. J. Plummer (1235, p. 14, 1927), and Tehuacana formation by the United States Geological Survey on the preliminary edition of the geologic map of Texas (396c, 1932). The name Tehuacana was given by Harris ( 662, p. 155, 1896) to designate the Midway limestone at Tehuacana, and was used in the same significance by H. J. Plummer (1235, pp. 12, 13, fig. l, 1927). The name is now in good usage among geologists for the limestone lentil. It therefore seems best to apply a new name to the basal strata of the Midway group in order to avoid confusion. Julia Gardner has proposed the name Kincaid from Kincaid ranch in 19SELECTED Ll'IERAnIRE-Penrose, R. A. F., 1189, pp. 19-22, 1889, Kennedy, W ., 911, p. 146, 1896. Harris. G. D., 662, pp. 127-130, 1896. Deussen, A., 415, pp. 33-36, 1914. Liddle, R. A., 992, pp. 74-81, 1918. Dumble, E. T., 506, pp. 34-37, 1918. Tbompaon, W. C., 1604, pp. 323-332, 1922. Trowbridge, A. C., 1610, pp. 88-89, 1923. Deuaaen, A., 421, pp. 40-46, 1924. Cooke, W., The Cenozoic formationa of Alabama : Geol. Suney Alabama Sp~. Rept. 14, pp. 253-257, 1926. Plummer, Helen· Jeanne, 1235, p. 14 and pp. 26-24, 1927. Semmes, D. R., OiI and Gao in A!abama: Geol. Survey Alabama Spec. Rpt. 15, pp. 232-239, 1929. Chadwick, Geo. H., 237, p. 117, 1929. The Geology of Texas-Cenozoic Systems 533 Uvalde County, and the United States Geological Survey has ap­proved this term. Sirice both Wilcox and basal Midway strata occur in the vicinity of the Kincaid ranch, it seems best to select a type locality more accessable to geologists and where the entire section is exposed. Miss Gardner selected Tehuacana bluff as typical of the Tehuacana formation, the name used in the preliminary edi­tion of the Texas geologic map, and this is the best possible type lo­cality for the basal Midway division. Tehuacana bluff is the steep hill just west of the town of Tehuacana in Limestone County. Other typical localities are the hluff on the right hank of Colorado River on Caldwell ranch20 4 miles by river helow Webherville and 21/z miles north of Caldwell village in Bastrop County, the exposures alóng Texas Highway No. 1 hetween the Terrell reservoir and Cohb, and especially the outcrops along the stream valleys in the vicinity of Ola and on hoth sides of the town of Elmo, Kaufman County. Regional geology.-The outcrop of the Kincaid formation in most areas is characterized by a prominent northwestward-facing cuesta, which is conspicuous where indurated ledges mark the top of the formation. At Pisgah Ridge and at Tehuacana, for example, the limestone caps the top of the ridge, and the glauconitic sands and clays form the slopes. The Kincaid formation has been mapped from central Delta County southwestward to the southern boundary of Kaufman County and from Richland Creek in Navarro County southwest to the center of Guadalupe County. It outcrops in western Bexar County, ex­tends across Medina into eastern Uvalde Co'unty, and is exposed for a short distance in Rio Grande Valley 18 miles southeast of Eagle Pass. Its ahsence on geologic maps northeast of central Delta County is thought to he due to a change in facies at the .outcrop from shallow marine to deltaic nonfossiliferous strata. Sorne geologists have suggested that the Kincaid strata were over­ lapped northeast of Delta County by younger nonfossiliferous heds. The. ahsence of the outcrop of the Kincaid formation from just south of Corsicana northeastward across Navarro County is due in part to a large normal fault, which hrings upper Wills Point heds in con­ tact with the Navarro and in part to a thinning and an áhsence of •Deuaaeii, Aleunder, 421, pp. 43, 44, 6g. ll, Sta. 213, 1924. the limestone. Its absence in Guadalupe County is due to an over­ lap of the Wills Point clay. In northeastern Maverick and western Zavala counties the Kincaid is overlapped by Carrizo sand. The Kincaid formation extends beneath the surface south of its outcrop throughout the entire east and central Texas area. Charac­teristic fossils have been obtained from it in wells as far south as the Boggy Creek oil field in Cherokee County and from the Gay Hill salt dome in Washington County. Strata containing a typical . Kincaid fauna outcrop on the Keechi salt dome in Anderson County. The Kincaid formation has an average thickness of 150 feet along the outcrop. The strata dip southeastward beneath younger for­ mations at the rate of 60 to 75 feet per mile. The formation thickens as the depth increases, and in sorne deep wells it is twice as thick as in outcrop. Measurements of sections of the outcrop and thick­ nesses in wells, in which formational contacts have been determined from reliable well samples, are included in the following table: LOCAT!ON COUNTY DEPTH AUTHORITY Feet Long-Bel! No. 1, Shaffer Oil & Rfg. Co., sec. 35, T. 5 S., R. 12 W. ___________________Grant (Ark.) 93 H. J. Plummer Outcrop, 2 mi. . of Cumby ____ Hopkins (Tex. ) 118 F. B. Plummer Outcrop, 2 mi . E. of Cedar Grove __________________ Kaufman (Tex.) 100 F. B. Plummer Outcrop, W. of Tehuacana_______Limestone (Tex.) 158 F. B. Plummer Outcrop, Brazos River val1ey____l\1ilam (Tex.) 40 A. C. Wright Outcrop ______ _ __Medina (Tex. ) 75-100 R. A. Liddle Price o. l _______________ __Uvalde (Tex.) 287 F. M. Getzendaner L. E. Hanchett o. l __-=-_Dimmit (Tex.) 216 A. C. Trowbridge Black o. 1, Texas Co.__________Maverick (Tex.) 250 F. 1. Getzen~aner Oppenheimer o. 1, S.W. of Pearsall ----------------------------Frio (Tex.) 152 L. W. MacNaughton Stratigraphy.-The Kincaid formation comprises the lower por­tion of the Midway group from the Cretaceous contact to the base of the Wills Point formation. The lower contact is everywhere un­conformable. The upper contact is drawn in northeast Texas at the plane between the Tehuacana limestone and overlying glau­conitic sand. Where the Tehuacana limestone is absent, the contact The Geology of Texas-Cenozoic Systems 535 is drawn at the top of the clays carrying characteristic lower Mid­way fossils and below a glauconite commonly referred to as the second persistent glauconite, which occurs at the base of the Wills Point formation and in places contains the very characteristic zone fossil, Venericardia bulla Dall. In south Texas the Wills Point formation in most places is overlapped by the Carrizo sand so that the contact is not well exposed. The upper contact of the Kincaid is known to be, in most places at least, unconformable. CI: NTRALTE:XA5 (\c.nc.r•Hx~d :)eetion EAOT T!!: XA~ Mex ia are 11 G ct n er.aliz.ed ~4ction Lime,.tone Count y -------­ OOUTHWC::> T TE:.X A5 / / Opp~nheimer No.\ f"rio Co unty / lcat1ty ¡ ~Li1;¡-ihm•n" ,c:::!:]'Pl•ni loullty ~e•I• c::::J O~~r.s mulfil1r#• loealhon Fig. 36. Outcrop of the Seguin formation in Bastrop, Caldwell, Guadalupe, and Bexar counties. 87J>ersonal communication. in a number of deep wells south of its, outcrop and also in wells in Upshur County in northeast Texas east of its surface exposure. lt undoubtedly extends over a wide area. The thickness of the Seguin formation on the outcrop is about 65 foet. Throughout central Texas it varies from 50 to 75 feet. In Rio Grande Valley, it may be greater, ás Jewell68 has measured a section that appear11 to show 190 feet of basal marine strata. In wells drilled south of its outcrop the Seguin formation has a thick­ness ranging from 100 to 160 feet. The measurements of a few typical sections are shown in the following table: LOCATION COU NTY T H! CKNESS AUTHORITY Feet Solomon's Creek, 6 miles S. of Elgin ···-····-····-····-················-····-··· Bastrop 65+ F. B. Plummer Red Bank Oil Co. core test No. 2, James McLaughlin Survey, 2 mi. W. of Brazos RiveL................ Milam 53 Do York Creek, 21h mi. S. of Fent· ress ······················-···-····-··········-····­ Caldwell 60 Do Cranfill and Germany, Norman No. 1 core test, 1h mi. NW. of Fentress ···-····-····-·····-·········-········· Caldwell so+ H. J . Plummer Rio Grande, Indio ranch.. ·-··········-··· Maverick 190 W. R. J ewell Oppenheimer No. 1, Amerada Oil Co. ···············-············--····-····-····-··· Frio 152 Mac aughton Stratigraphy.-The Seguin formation rests conformably upon the upper Wills Point strata (Kerens member) in northeast Texas, dis­conformably upon the middle Wills Point in sorne places in south­central Texas, and disconformably u pon the Kincaid formation in southwest Texas. It is overlain by the Rockdale formation. It is thought that the contact of the Seguin and Rockdale is conformable, hut it is possible that the upper Seguin strata have been removed in places, since in sorne areas the basal strata of the Wilcox group resemble the Rockdale, and no lower fossiliferous strata are present. No unconformable contacts have as yet been observed. The Seguin formation can be divided into two members: 2. Caldwell Knob oyster bed l. Solomon Creek clays and sands 88JewellJ W. R., personal communication, 1924. See also Gardner, J. A., 566, pp. 141-145, 1924. The Geology of Texas-Cenozoic Systems 577 The Solomon Creek member is composed of gray, laminated, silty clay, fine, uniformly grained, gray sand containing large, flat, rough-surfaced, calcareous concretions from one to twelve feet in length and from a few inches to severa! feet thick, and layers of silty, carbonaceous clay containing plant remains, sulphur and gyp­sum crystals. This member carries no lignite beds. The strata are typically exposed in Solomon's Creek, 6 miles south 25 degrees west of Elgin, Bastrop County. The Caldwell Knob member consists of a layer of oyster shells varying from a few inches to severa! feet in thickness, the average thickness being about one foot. The oysters, in most places Ostrea multilirata Conrad, líe in a matrix of calcareous silt which in most places is cemented into a hard sandy limestone. The bed has been traced by Miss Gardner (566, p. 143, 1924) from a point near Brazos River in Milam County to the Río Grande Valley and has been identified on the Guerrero structure near Guerrero in Mexico. It is not continuous along the outcrops. In many places it is covered by loose sand from adjacent beds or by grave! from Pleistocene deposits. In other places it may have been removed by pre-Rockdale erosion, or it may never have been deposited. Its outcrop in central Texas is shown in figure 36. The type locality of this member is Caldwell Knob located 10 miles north of Bastrop and about 2 miles south of Colorado River in Bastrop County, where the oyster Ostrea multilirata Conrad var. duvali Gardner is abundant. The characteristics of the Seguin formation m the various areas are best shown by the following sections: Core test No. 2, Red Bank Oil Compan,y, on ]anies McLaughlin Survey about 2 miles west o/ Brazos River, eastern Milam County. (Core samples furnished by B. F. Robinson) Thickness Feet Shell bed, gray, hard, made up of large nurnbers of fragments of oyster shells set in a matrix of silt firmly cemented by calcite.__ 1 Silt, gray, very uniformly fine grained, thinly bedded, with wavy bedding lines and an impression of a complete leaL________________ 6 Clay, gray, interbedded with thin layers of gray silt___________________ 10 Sand, light gray, uniformly fine grained, containing thin layers of tough, compact clay ----------------------------------------------------·--------------10 Silt, gray, uniformly fine grained, containing small fragments of plant remains and very thin layers of silt clay___________________________ 21 Sand, light gray, very fine grained, thinly bedded. The bedding lines are wavy in places and show cross bedding with very fine partings of silt, in which the sand and silt laminae alternate. About 40 laminae comprise one inch of section_________________ _______ _ ___ 10 Total thickness _________________________:..________________________________________ 53 Section along Solomon's Creek from a point near its junction with Wilbarger Creek northeastward up the creek to a point about .1 of a mile southwest of Lawrence Solomon's farmhouse, on the Elgin-Utley road, 5.8 miles by road south-southwest o/ the railroad crossing about 1 mile south o/ Elgin, Bastro¡> County. Thickness Seguin formation-Feet 7. Sand, buff gray, in layers l " to 2' thick, interbedded with thin beds (1,4" to %,") of dark gray clay. Sand is strongly cross-bedded ---------------------·-----------------------------------------------------------16 6. Sand, light gray, very fine, in layers from 3" to 8" thick, and lentils interbedded with fine silty shale; concretions less numerous than lower in section ------------------------------------------------10 5. Silty clay, gray, soft, thinly laminated, contains large, rough-surfaced concretions and reddish-gray ferruginous concre­tions. One concretion is foil of a species of Turritella about 1 inch long_________________________________________________________________________________ 12 4. Sandy clay, thin bedded, contains log-shaped colony of cal­careous tubes resembling fucoids having white, shell-like surfaces, black, carbonaceous matrix. Contains also more or less rounded boulderlike concretions in large numbers_ __ 15 3. Sand, buff gray, fine grained, thin bedded, with thin lentils of unlaminated sand 3" to 6" thick. Contains large, hard, buff­colored, flat, irregularly shaped, smooth-surfaced concretions from l' to 7' or more long and from 6" to 4' thick. Concre­tions are plentiful and cover creek bottom. Sorne have very rough, irregular, and wavy surfaces and occur in a concre­ tionary ledge about 4' thick______________________________________________________ 4 2. Sandy clay or silt, gray, stained with rusty streaks, thin bed­ded, carbonaceous, having yellow film of sulphur on sorne bedding planes, limonite on others__________________________________________ 5 Wills Point formation­ 1. Clay, dark bluish gray, brittle, weathering light gray, fossilif­erous: Natica reversa Whitfield, Dentalium, "Pleurotoma" sp., Ringicula alabamensis Aldrich, frequent ostracods, foraminifera. This is the type locality for Ammobaculites midwayensis H. J. Plummer and A. ex pansus H. J. Plummer 5 Total thickness measured__________________________ _____ __________ __ ____________ 67 The Geology of Texas-Cenozoic Systems 579 Section o/ Seguin /ormation in Norman No. 1 (shallow core test), one-half mile northeast o/ Fentress, Caldwell County (drüled by Crdnfill and Germany). Thickness Feet Seguin fonnation-Oay, yellow, brown, loose, sandy. Washed sampl_e contains lumps of selenite, angular and subangular etched quartz grains, few magnetite grains, and traces of glauconite_______________________________ 30 Oay, yellow, brown, loose, sandy. Washed sample is made up of finely divided siliceous and argillaceous grains bound to­gether by crystals of selenite and limonitic matter, little mica ----------------------------------------------------------------------------------------------15 Clay, brownish gray, compact, silty. Washed sample is composed of fine, brown, micaceous silt, lurnps of selenite, little li­monite and magnetite, and rounded to angular quartz grains 5 Wills Point formation- Clay, dark, tough, heavy bedded. Washed sample very small and cornposed of fine micaceous silt, little glauconite, little py­rite, few grains of selenite, and a generous scattering of tests of Anunobaciúites midwayensis H. J. Plummer and A. ex­ pansus H. ]. Plummer.__________________________________________________________________ 5 Total thickness measured___________________________________________________ 55 Sedimentology.-The Seguin formation is composed of shallow· water marine sediments deposited in the littoral zone and along the beach of a flat, featureless marshy coast. The materials of these beds are much coarser than those of the underlying Midway, and they are interbedded with thin layers of subaqueous plant detritus such as accumulates in a tidal marsh. The laminations in the sand and silt are fairly evenly spaced, from ten to twenty to the inch, and indicate moderately rapid deposition. The oyster bed indicates perhaps a beach deposit in which the shells accumulated as heach shingle. In many places they appear to he wave worn and piled up hy wave action. The sands and silts were probably derived from the adjacent coastal plain and perhaps from Upper Cretaceous strata. Lithology.-The strata of the Seguin consist of ahout 50 per cent fine sand, 30 per cent silt, 19 per cent clay, and 1 per cerit carhonaceous matter. The mineral grains consist of angular and suhangular quartz, few selenite crystals, limonite, considerable altered mica, traces of magnetite, and a ·Iittle glauconite. All the beds 11re unconsolidated except the concretions, which are large, rough surfaced, oblate, and firmly cemented with calcite. A chemical analysis of typical clays from the Seguin formation is as follows: Analysis69 of clay from Elgin, Bastrop County Per cent Silica 71.3 Alumina 19.7 F erric oxide ------------------------------------------------------------------------------------------­LO Lime ---------------------------------------------------------------------------------------------------------2.1 Magnesia -----------------------------------------------------------------------------------------------Trace Soda ----------------------------------------------------------------------------------------------------0.08 Potash -----------------------------------------------------------------------------------------------------Trace Titanic acid ----------------------------------------------------------------------·----------------------Trace Water -------------------------------------·-----------------------------------------------------------------5.8 To tal --------------------------------------------------------------------------------------99. 98 Distinguishing characteristics.-The Seguin formation can be dis­tinguished by the following criteria: l. Characteristic oyster bed at top of section. 2. Uniformly finely textured and finely laminated sands contammg black flakes of leaf fragments, interbedded with thin layers of black carbonaceous matter. The uniformly darker, silty clays of the underlying Wills Point have very little or no car­bonaceous matter. 3. Large, rough-surfaced, calcareous concretions containing white­shelled fragments, oysters, and ornamented gastropods of the genus Cerithium. These concretions are larger, more evenly laminated, and more numerous than those in the Rockdale. They do not contain plant leaves. The concretions in the Rockdalc formation are less distinctly laminated, and have no shell fragments. 4. The sands and clays in most places are more thinly laminated and have less lignitic matter than the overlying Rockdale for­mation. Paleontology.-The fauna of the Seguin formation has not yet been described.70 It was first reported by oil geologists working in Bastrop County about 1922 and first mentioned in literature by Trowbridge (1610, p. 90, 1923) and Gardner (565, p. 109, 1923). ""Ríes, Heinrich, 1320, p. 77, 1908. 70Mr. C. B. Claypool. aided by a fello~ship grant cd by thd National Research Council (I932L. is engaged in a study of the faunas of the Wi1cox group at the University oí Illinois. The Geology of Texas-Cenozoic Systems 581 The fossils, with the exception of the common oyster, Ostrea mul­tilirata Conrad, which is found in great numbers as var. duvali Gardner in the Caldwell Knob member, occur in large calcareous concretions. Collections from the Solomon Creek beds and in the Bureau of Economic Geology contain the following forms: Gastropoda-Natica (Lunatia) cf. . eminula Conrad Turritella n. sp. Cerithium mediaviae Harris Cerithium n. sp., A Cerithium n. sp., B Cerithium n. sp., C Cerithium n. sp., D Pseudoliva cf. P. unicarinata Aldrich Pseudoliva ostrarupis var. pauper Harris Levifusus aff. L. supraplanus Harris Levifusus pagoda (Heilprin) cf. var. Harris Levifusus n. sp. Fusus ostrarupis Harris Volutocorbis limposis (Conrad) var. Fusoficula cf. F. juvensis (Whitfield) Olivella sp. "Pleurotoma" ostrarupis Harris "Pleurotoma" aff. P. nodoideus Aldrich "Pleurotoma" aff. P. mqorei Gabb Pelecypoda-Ostrea multilirata Conrad Leda sp. cf. L. corpul entoides Ostrea multilirata Conrad var. duvali Aldrich Gardner Venericardia sp. ucula sp. Cardium sp. Tellina sp. cf. T. trumani Harris Protocardia sp. Yoldia sp. Callocardia sp. cf. C. nutlalliopsis Leda milamensis Harris var. greggi ( Harris) Cephalopoda-Hercoglossa sp. cf. H. vaughani Gardner Most of these fossils appear to be identical with, or related to, early Wilcox forms in Alabama and Mississippi. They are more closely related to the Wilcox faunal groups at Alabama Landing and Greggs Landing in Alabama than they are to any Midway as­semblages. In fact, only 6 out of 40 species identified from Solo­mon's Creek can be referred to Wills Point species. The fossils are more thick shelled and consist largely of oysters, large forms of V enericardia, Cerithium, and Levifusus. There are fewer of the delicately ornamented, small gastropods and none of the small, delicate corals frequent in the Wills Point strata. lt is a near­shore, shallow-water assemblage. Another marine fauna occurs in the Rio Grande Valley about 190 feet above the hase of the Wilcox group, as mapped by W. R. Jewell. It belongs possibly to the Rockdale formation, but more likely it represents the upper ·portion of the Seguin, which may have thickened southwestward. The fossils were collected by Jewell 3 miles northwest of Jacal ranch house and about 18 miles south· east of Eagle Pass in Maverick County, and identifications were made by Miss Gardner (566, p. 144, 1924) as follows: Cornulina armigera (Conrad) atica sp. Pseudoiiva vetusta ( Conrad) Limopsis ? sp. Pseudoliva sp. cf. P. vetusta Ostrea sp. cf. O. thirsae (Gabb) (Conrad) Modiolus sp. Pseudoliva sp.? Veneri.cardia planicosta Lamarck Levifusus ? sp. Venericardia sp. Cerithium sp. Cardium cf. C. tuomeyi Aldrich Cerithopsis ? sp. Cardium hatchetigbeense Aldrich Cerithiopsis ? n. sp. Cardium n. sp.? Turritella mortoni Conrad Cardium sp. Turritella humerosa Coilrad Callocardia sp. cf. C. nuttalliopsis Turritella sp. (Heilprin) var. greggi (Harris) Calyptraea aperta (Solander) Pteropsis n. sp. Architectonica ? sp. Few, if any, of these species are similar to the forms just described from the lower Seguin. Many of these forms occur in the Wilcox strata of Alabama, and such species as Turritella mortoni Conrad, T. humerosa Conrad, Ostrea thirsae (Gahb) and Callocardia nut­talliopsis var. greggi (Harris) are found in the Nanafalia, or oldest division of the Wilcox group in that state. It is remarkable ·that Ostrea thirsae (Gabb), so very persistent in the lower Wilcox strata in Alabama, should not occur in Mississippi or anywhere in Texas except in the Rio Grande Valley. lt has been reported from the Wilcox in northern Mexico and may yet be discovered in central Texas. Two distinct fossil zones occur in the Seguin formation in central Texas. The diagnostic forms of each are of great aid in correlating the lower Wilcox strata. 2. Ostrea multilirata zone al the top of the Seguin formation and comprising the Caldwell Knob member. This zone is marked by a great abundance of O. multilirata Conrad, Cerithium. pen­rosei Harris and C. texana Heilprin. The Geology of Texas-Cenozoic Systems 583 l. Turritella turneri n. sp. (MS.) zone near the base of the Seguin formation. Remains of this small turreted and lirated gastro· pod occur with "Pleurotoma"' sylvaerupis Harris and other gas­tropods in conc:retions. It is easily recognized and serves to distinguish the strata at once from the underlying Midway. Correlation.-The fauna of the Seguin formation has not been studied sufficiently to warrant definite correlations with other groups. The fossils are related unquestionably to the faunas of the lower member.s of the Wilcox group of Alabama. They seem to have close affinities with the fossils of the Ackerman formation of Mis· sissippi and the Nanafalia formation of western Alabama. Their relationships with faunas of the Atlantic coast, of California, and of Mexico are not known. Economic resources.-The Seguin formation has no noteworthy economic resources other than agricultura! products and forests. The soils and agricultura! products are simj}ar to those of the middle Wilcox beds and are discussed fully in the paragraphs on economic resources of the Rockdale formation. The large, hard, boulderlike concretions are sufficiently numerous in sorne places to furnish a supply of rock for crushing for road ballast or concrete mixtures where terrace gravels are not available. At present they are not being utilized except at one locality in Navarro County. ROCK.DALE FORMATION'l' Definition.-The name Rockdale is proposed to designate all the nonmarine strata of the Wilcox group from the top of the Caldwell Knob oyster bed or its equivalent beds to the base of the marine strata of the Sabinetown formation, the upper division of the Wilcox group. In areas where the Sabinetown formation is absent the Rockdale formation is limited at the top by the Carrizo sand of the Claiborne group. The type locality of the Rockdale formation comprises exposures in. central Milam County in the vicinity of Rockdale, where the lignitic members of the formation are mined. '11LITEllATUU-Dumble, E. T., 470, pp. 13~139, 1892; S06, pp. 37-55, 1918. Liddle, R. A., 992, pp. 82~6. 1918. Sellards, E. H., 1402, pp. 57-63, 1919. Trowbridge, A. C., 1610, PP• 9_><>~ ~ 0 o~•nd B Lim c.$'roric. ~Oy~h~.r $hct.l b E@ f"o:.$il ife.rou$ $h .oi\c ~~hale. ai rid c l a.y §Glzr. vc..oni 're § u qnit <&. § e ovldc.re Fig. 38. Columnar sections showing Claiborne formations across Texas. CARRIZO FORMATION'º' Definition.-The Carrizo formation was named by Owen (454, p. 70, 1889), who separated an upper, massive, sandy layer from the underlying clays of the lower Lignitic beds and named it the Carrizo sandstone, because it furnished well water to the town of Carrizo Springs. Dumble ( 494, pp. 929, 930, 1903), after study­ing Kennedy's report on the unconformable relationships of the underlying clays with the Carrizo sands, believed that this sand should. be separated from the Wilcox group and be correlated with 1°'L1TERATCR•-Owen, J., 454, pp. 70-74, 1889. Vaughan, T. W., 1687, p. 45, 1900. Dumble, E. T., 494, pp. 929, 930, 1903; 498, pp. 52, 53, 1911; 506, pp. 37-55, 1918. Liddle, R. A., 992, pp. 87-93, 1918. Sellards, E. H., 1402, pp. 63, 64, 1919. Trowbridgc, A. C., 1610, pp. 91-93, 1923; 1613a, pp. 52-64, 1932. Deussen, A., 421, pp. 58-62, 1924. Brucks, A. W., 164, p. 831, 1927. Gctzcndancr, F. M. 578, p. 1434, 1930. The Geology of Texas-Cenozoic Systems 613 the Queen City sand of east Texas and with the Tallahatta forma­tion of Alabama. Udden, Baker, and Bose, (1652, pp. 83-84, 1916) and Liddle (912, pp. 87-93, 1918) treated the Carrizo as a separate formation and placed it in the Claiborne group. Sellards (1402, pp. 63-65, 1919) also separated it from the Wilcox and made it a formation of equal rank, but did not group it with the Claiborne. Berry (105a, p. 4, 1922) obtained plant fossils from the Carrizo sand and concluded that the plants were more closely related to the Wilcox flora than to the plants in the overlying strata. Trowbridge (1610, p. 89, 1923), influenced by Berry's de­terminations, placed the Carrizo in the Wilcox group and named the strata below the Carrizo the Indio formation.1º5 Wendlandt and Knebel (1728, pp. 1350-1352, 1929) mapped the Carrizo around the flanks of the Sabine uplift and across northeast Texas from Leon County to Sulphur River. These authors and Miss El­lisor (523, p. 1343, 1929) have shown that the Carrizo does not correlate with the Queen City, as ,Dumble thought, but with a sand below the Reklaw at the base of the Claiborne section. Renick and Stenzel (1299, p. 81, 1931) mapped and described the Carrizo sand in Brazos River valley. Miss Gardner, in assisting in the prepara· tion of the new geologic map of Texas, has traced the outcrop of the Carrizo from the Rio Grande to Sabine River ºand has shown its true relationships across the state. The exact age of the Carrizo is still somewhat problematical. The reasons for including it in the Claiborne are (1) the Carrizo sand is separated from the underlying Wilcox by a definite unconformity; (2) · it merges into the Reklaw sediments above by a gradual transition; and (3) its color, lithology, and physical characteristics are more like those of the Claiborne than the Wilcox. The Carrizo sand so closely resembles the Queen City sand, that for a long time the two were believed to be equivalent (Dumble 506, p. 61, 1918). ( 4) The evidence offered by the plant remains in the Carrizo, criteria that influenced Trowbridge and Deussen to place the Car­rizo in the Wilcox, is now regarded as inconclusive, since the Grenada sand with similar plant remains is now known to correlate lO&frowbridge originalJy described three formations within the Wilcox group. It was discovered later, however, that bis upper division, the Bigford, correlated with tbe lower strata of the Claiborne group in east Texas, and accordingly it was removed from the Wilcox. with the Tallahatta of Alabama ·and not with the Wilcox in that area. Owen in naming the formation did not designate a type locality. Berry (105a, p. 4, 1922) states that the type locality is the outcrop in the quarries one-half mile west of Carrizo Springs. These quar­ries are now thought to lie in the base of the Reklaw and not in the original series of underlying sands defined as Carrizo. Geologists working in the district agree that if a type locality is to be desig­nated, it should be the exposure known as Brand Rock on Peña Creek west of Carrizo Springs. Regional Geology.-The surface expression of the Carrizo for­mation is a ridge of moderate relief covered by loose buff or gray sand and forested by a more or less thick growth of blackjack oak, sandy-land hickory, poison ivy, and cucumber-leafed sunflower. The formation ·outcrops in a belt about three miles wide along the southeast edge of the Wilcox group of formatioris from the Rio Grande on the southwest to Sulphur River on the northeast. In the extreme northeast part of the state the outcrops are obscured by alluvium and terrace deposits of the Sabine. and Sulphur rivers and their many tributaries, but the formation is thought to extend into Louisiana. . On the west side of the Sabine uplift the Carrizo occurs also in a belt from a fraction of a mile to three miles wide west of the Wilcox outcrop. Southeast of the outcrop of the Car­rizo along the central Texas monocline and west of its outcrop on the flanks of the Sabine uplift it is penetrated in all the wells that have been drilled sufficiently deep. The thickness of the Carrizo varies from a few feet on the west side of .the Sabine uplift to nearly 300 feet in Nueces River valley in south Texas. Measurements in severa} areas in Texas are shown in the following table: LOCALITY COUNTY Tll'ICKNESS AUTHORITY Feet Christian No. 1, Amerada Pet. Co., Felix Flores Survey_________ Smith 43 Denison Core test, near Rusk__________________ Cherokee 50 Wright Wade No. 1, J. H. Fields Survey__ Upshur 80 Do Outcrop section ------------------------Camp & Morris 40--50 Do Outcrop section, E. of Lavernia_ Wilson 87 Deussen Outcrop section ---------------------Medina 75-100 Liddle Outcrop section ------------------------Uvalde 100 Getzendaner The Geology of Texas-Cenozoic Systems 615 LOCALITY COUNTY THICKNESS AUTHORJTY Feet T. R. Price No. 1, W. E. Er­skine Survey, sec. 34 _______________ Zavala 255 Do Weathersby No. 1, A. B. & M. Survey, Bk. A, sec. 44____________ Zavala 231 Do Huffman No. 3, 3 mi. N. of In­dio --------------------------Zavala 137 Do Holmsombuck water well, Crystal City ---------\.-------------------------Zavala 300 Do Outcrop section, Rio Grande Valley, SW. of Carriw Springs Dimmit 118 Trowbridge Oppenheimer No. 1, Amerada Pet. Co. -------------------------------Frío 295 MacNaughton Stratigraphy.-The Carrizo sands are disconformable with the beds of the underlying Wilcox group. In Sabine River valley, in the San Antonio area, and in Rio Grande valley the sand rests upon the Sabinetown formation. In most other districts the Sabinetown has been eroded, is overlapped by the Carrizo, or is present in an unrecognizable nonmarine facies. Whatever the relationship, in sorne places the Carrizo sand rests upon cross-bedded and non· marine sandy clays, in other places upon unevenly bedded, glau­conitic, sandy, marine strata, and in still other places on cross­bedded deltaic beds. These relationships leave no doubt of an ahrupt change in sedimentation between the Wilcox and Carrizo epochs. The upper contact of the Carrizo with the Reklaw is conformable,1°6 and in sorne places it is difficult to draw the line of demarcation. The Carrizo formation has not been subdivided into memhers, and divisions are not feasible in so uniform a sand. The character of the strata in the various districts is best shown by sections. lOODeussen. A., 421, p. 60, 1924. In this treatise localities are described to illuatrate the unconformable relationships betweeo the Carrizo and Mt. Selman formations. The author'1 excellent work waa done before the Carrizo had been mapped or tbe present subdivisions of the Claiborne differentiated, so that the localities mentioned by him are not at tbe top of the Carrizo, as now designated, but at or near the base of the sand. For comparison, &ee the outcrop of the Carrizo in Bastrop County, as mapped by Miss Julia Gardner (396e. 1932) . Section1or o/ Carrizo sandstone 11h miles north and west of Chupadera ran_ch, near the southwest comer o/ Dimmit County. Thickness Feet 7. Gray, concretionary sandstone ..·-···-····-··········-····-··········-··········· 10 6. Interbedded brown and gray sandstone·--···--·-····-·-·---··-····· 10 5. Gray shale with a few slabs of gray to brown sandstone .. ·-·····-8 4. Smooth gray sandstone, brown on surface.................. ·-···--···-··· Va 3. Gray shale ···-····························-····-····-····-··-··-····-············-··········· 1 2. Gray, shaly sandstone, cross-bedded ................................ -·····-····-·2-4 l. Gray sandstone in thin slabs ........ ·-····-····-····-···············-···-········· 10 Total thickness measured, about.. ..... ______________________.... 44 Section' ºª o/ Carrizo sand on Sutherland Springs road 3 mües east of La­vernia, Wilson County. Thickness Feet Sandstone, red, ferruginous, soft.. .. -·-······-···········-···-··········-·········-··· 20 Shale, red, ferruginous, with argillaceous sand .. ·-··-····--····-···-····-··· 2 Sand, red ·······-···-····-··········-·················-··································-·--········· 4 Shale, white, sandy ........ ·-···············-···-···-························-····················· 1 Sand, red ···-·····-···-·--····-····-····---·--·--······-·················-···-·-····-······· 2 Unexposed --····-···-···-······-···-····------········--····-···--··-···-····· 8 Sand, red, ferruginous ........................... ---·-·-··········-··-············-···-······ 10 Unexposed ······-··-···-····-····-··--··---·-···----·····-···-·-···-···· 15 Sand, gray, laminated, argillaceous ............ -.. ········-···-·······················-3 Sand, red, ferruginous ... -··-···-··-··-·-·-···-····-·····-····-···-·-········-······· 2 Sand, reddish gray, laminated....----····-------····-······-············-······-20 Total section measurecL . _______......... _.________________________ 87 Sedimentology.-The Carrizo sand, for the most part, is a con· tinental deposit laid down by streams that dropped their loads on a flat coastal plain and built up a broad alluvial apron ~.ll along the coast. Severa! factors operated to bring about deposition of a sand sheet so widespread. The Sabinetown sea of the late Wilcox epoch withdrew, and increased rainfall furnished floods of water to the valleys. The continental base-level was brought down to the position of the Paluxy and Trinity sands. The capping limestones had been cut by erosion, and large quantities of unconsolidated sand were transported seaward by the floods and spread broadcast 107Trowbridge, 1613a, p. 61, 1932. 108Measured by A. Deussen, 421, p. 60, 1924. The Geology of TexaB-Cenozoic Systems 617 by the streams along the present coastal plain. The epoch ended by a slow return of the sea, a decrease in the gradient of the streams, and a slow replacement of the continental ·deposits by shallow-water, marine sediments of the Reklaw formation. Lithology.-The Carrizo formation consists of about nine-tenths medium-grained sand and one·tenth sandy clay. No lignite has been definitely reported from this formation in northeast Texas, but the sand contains carbonaceous material and plant leaves in many places. The sand in sorne places contains considerable fer­ruginous material, which lends a brilliant color to the outcrop and life to the soils. The basal strata of the Carrizo are composed chiefly of rounded and subangular quartz grains that average about one millimeter in diameter. In places these grains are cemented by ferruginous mat­ter to form concretions. The upper strata are slightly finer grained, less ferruginous, and more uniformly textured. In sorne places they contain lentils of yellow, ferruginous clay. Lonsdale and his assistants (1013c, pp. 77-81, 1931) have in­vestigated the microscopic characters and mineral . composition of the Carrizo sands. They find about four-fifths of the grains are subangular and the minerals comprise the following in order of abundance: Low-gravity minerals High-gravity minerals Quartz Leucoxene Microcline Ilmenite Plagioclase Magnetite Glauconite Tourmaline Zircon Staurolite Rutile Muscovite Distinguishing characteristics.-The distinguishing characteristics of the Carrizo strata are: l. Texture. The sand is slightly coarser than that of the Wilcox strata. The size of the grains ranges up to 2 mm. in diameter, whereas the Wilcox grains are rarely larger than .3 mm. 2. Stratüication lines. The Carrizo strata are thicker, more massive­ly hedded. more conspicuously cross-hedded, and they contain a larger proportion of sand heds in the outcropping section than do the average Wilcox strata helow or the Reklaw ahove. 3. Color. The carrizo shows more mottling of red and buff shades in its exposures than does the underlying Wilcox. It is less intense a red and has fewer limonitic stains and less fer· ruginous matter tlian the overlying Reklaw. Paleontology.-No vertebrate fossils have been reported from the Carrizo formation. Plant leaves and stems are found in a few places, but most of these are very poorly preserved. The plants listed by Berry (lOSa, pp. 3, 4, 1922) from the Carrizo in south Texas are thought to belong in overlying strata. Fig. 39. Outc:rop of the carrizo sand in southwest Texas and area to which it furnishes abundant artesian water (after Lonsdale, Robinson, Turner, and Sayre, 1013b, map 3, 1931). Correlation,-The correlation table of Claiborne formations in the Gulf Coast area (fig. 40) and the section along the Gulf Coast (fig. 41) show the Carrizo sand as the equivalent of the lower part of the Tallahatta formation of Mississippi and Alabama. Economic resources.-The chief economic resources of the Car­rizo are its underground-water supply and its glass sand. Water occurs in the formation throughout its extent, and most farms located south of its outcrop derive their water supply from its beds. In the southwestern Texas area, according to Lonsdale The Geology of Texas-Cenozoic Systems 619 and associates (1013b, p. 3, 1931) waters from the Carrizo are used extensively for irrigation. More than five hundred pumping plants and artesian wells, most of which obtain their supply from the Car­rizo, are in operation and altogether 29,000 acres of land are irri­gated in this way. The water-bearing stratum has an average thick­ness of 200 feet. The belt in which the sandstone can be reached within a depth of a thousand feet has an average width of fifteen miles ( fig. 39) . The average permeability is about 200 gallons a day through a cross section a foot high and a mile wide with a gradient of one foor per mile, or 24,000,000 gallons per day for the pumped districts of Zavala and Dimmit counties. When the value of ali this water to the crops and cattle in a region of low summer rainfall is considered, it will be found that this resource in the long run ranks as high in value as the lignite in the Wilcox or the oil in the Jackson. The Carrizo sand occurs in sufficient purity in sorne places to make glass. The quartz foses to produce clear, green glass suit­able for the manufacture of bottles, vases, and other articles. A factory established at Three Rivers, Live Oak County, procures its sand from Haiduk Switch on the San Antonio, Uvalde and Gulf Railroad in the north edge of Atascosa County. lt is manufacturing glass successfully on a large scale. REKLAW FORMATION1oo Definition.-The Reklaw formation was named by E. A. Wend­landt and G. M. Knebel (1728, p. 1352, 1929) to designate the strata in east Texas below the Queen City and above the Carrizo sand. Trowbridge (1610, p. 92, 1923) had given the name Bigford to certain clay strata south of Carrizo Springs which he supposed to be a portion of the Wilcox group. Miss Gardner (396c, 1932) :r.egards the Bigf ord as contemporaneous with, but not exactly equivalent to, the Reklaw and has preferred to retain Trowbridge's name in place of Rekláw for strata immediately above the Carrizo southwest of Atascosa County. Trowbridge (1610, p. 92, 1923) defined Bigford as follows: 109L1TERATtJJ1B-Trowbridge, A. C., 1610, p. 92, 1923. Ellisor, A. C., 523, p. 13•2, 1929. Wendlandt, E. A., and Knebel, G. M., 1728, p. 1352, 1929. Renick, B. C., and Stenzel, H. B.• 1299, pp. 83-84, 1931. Trowbridge, A. C., 1613a, pp. 65-llO, 1923. South of Carrizo Springs the sand and sandstone of the Carrizo give place along the strike to clay, thin-bedded sandstone, and lignite. To these beds, which consist so largely of clay that they are not to be called Carrizo sandstone, the name Bigford is here given. The description as well as the map accompanying Trowhridge's report indicates clearly that Trowhridge intended Bigford to be a facies of the Carrizo-simply a change froµi sand to clay along the strike. On the map by Trowbridge (1610, pl. 28, 1923) the Carrizo merges abruptly into Bigford 8 miles due south of Carrizo Springs. The line drawn hetween the Bigford and Carrizo hy Miss Gardner is only 1 mile southeast of Carrizo Springs. Accordingly, Miss Gardner has amended and expanded the Bigf ord formation of Trowbridge, in order to make it a valid formation and has separated it from the Carrizo. The Nueces Valley emhayment was shallower than the east Texas embayment, received sorne sediments from a north Mexico land mass as well as from the northern sources, was so elevated at certain times that the sea withdrew, and continental sand and palustral coal beds were interbedded with marine strata. Such local conditions pro­duced deposits in south Texas somewhat different from those in east Texas. lt seems, however, unnecessary to use two names for con­temporaneous strata, even though they are lithologically somewhat different. Since the name Reklaw has priority over the amendation of Miss Gardner, and since it is in estahlished usage by geologists110 of the state, it is preferable to adopt it exclusively, if pos~ihle. The type locality of the Reklaw formation is the section along the Texas and New Orleans Railroad 1 mile east of Reklaw in Cherokee County. Regional geology.-The surface exposure of the Reklaw formation is typiéally a gentle, rolling, mature topography charllcterized hy red soil. The outcrop is less rugged and less forested than the Car­J:lizo or Queen City and may he described as a red prairie belt be­tween two hroad, oak-forested ridges. The Reklaw formation has two belts of outcrop in Texas. One extends around the west flank of the Sabine uplift from the northwest comer of Marion County southwest to western Rusk County, thence southeast to the Louisiana line in east-central Sahine County (1728, p. 1349, 1929). The 110Renick, B. Coleman, and Stenzel, H. B., 1299, p. 83, 1931. Levorsen, A. F., 987a, p. 263, 1931. Wamer, C;-A., 1709a, p. 48, 1932. The Geology of Texas-Cenozoic Systems 621 other extends from Sulphur .River on the Arkansas line southwest­ward to the southeast comer of Van Zandt County, thence south­ward to Navasota River in western Leon County and across central Bastrop and northwestern Wilson counties to Atascosa County. Southwestward from Atascosa River to the Rio Grande the strata helonging to this formation are more sandy, less lignitic, and, al­though contemporaneous, are thought by Miss Gardner111 to diff er sufficiently lithologically to make the exact relationships of her Bigford strat,a }Vith the Reklaw of east Texas uncertain. As now represented on the geologic map of Texas (396c, 1932) the belt of outcrop of the Bigford is much wider than that of the Reklaw in east Texas and extends across northern Frio, western Zavala, and western Dimmit counties to northwestern Webb County. The aver­age width of the outcrop in northeast Texas is Ph miles, but in the Rio Grande district the outcrop widens, if correctly mapped, to 12 miles or more. Throughout its extent from Louisiana to Atascosa River the Reklaw is a distinctive and easily distinguishable for· mation, which deserves more recognition and more detailed study than it has received in the past. The subsurface contacts of the Reklaw in well logs and sets of well samples are not determined so easily as the boundaries of the surface outcrop. In the area immediately south of its outcrop the formation can be recognized as clay strata between two prominent sandstone zones. Farther south at a distance of 50 or 75 miles from the outcrop the sands above and below merge into marine sandy clays, change in character, and lose their identity so that the Reklaw · heds can be distinguished only by their microfossils, which are so similar to the fauna of the Weches formation that the limits of the formation cannot be marked accurately in most wells. The thickness of the Reklaw varies from 80 feet in central Texas to 700 feet or more in the Rio Grande district. The few records where authentic measurenients of the thickness have been obtained are shown in the following table: 111Misn. H. D . Pc.-nonal communic:i:h)n to E. H. Sellards, August 4. 1932. LOCALJTY COU 'TY THICKNESS A THOHITY Feet Thompson No. 1, Humphreys Corp. ·········-····-················-········· Cherokee 142 Wendlandt and Knebel Brazos River Valley·--····-·····-···· Robinson 60-100 B. C. Renick Core test near Troup...·-···-··-···· Smith 75 A. C. Wright Core test ···-··-···-····-········-···-· Cherokee 80 Do Bonner No. 1-A, core test, Wm. Elliott Surv. ···-····-····-···-----Angelina 125 Wendlandt and Knebel So. Pine o. 4-A, core test, Hum­ble O. & R. Co....... ----····-····-Houston 180 Alva Ellisor So. Pine No. 1-A, core test, Hum­ ble O. & R. Co...·-····-··--·-Trinity J50 Do Renfro No. 1, Simms Oil Co..... Angelina 95 Do Generalized section ...................... Zavala 700~800 F. M. Getzendaner Oppenheimer No. 1, Amerada Pet. Co. ·----···-···-····--·--·· Frio 650 MacNaughton J. H. Strickling core test, D-395.. Leon 53 Wm. Penn Stratigraphy.-The Reklaw formation rests conformably upon the underlying Carrizo sand and is overlain conformably by the Queen City sand. In Cherokee County and in sorne other places in east Texas the lower contact is marked by a thin, dark-green glauconite bed in the base of the Reklaw, and in many places this bed contains large numbers of V enericard-ia planicost,a Lamarck. Where this bed is not present the contact is marked by an abrupt downward change from the glauconitic Reklaw sand to laminated yellowish clay typical of the Carrizo. The upper contact is marked by an abrupt change from yellow, ferruginous clay to medium-grained sand. In southwest Texas the Reklaw-Carrizo contact is less sharp. In the Rio Grande area the contact is drawn where the strata change upward from predominately sandy to predoniinately clayey. The contact of the Reklaw with the Queen City formation is likewise indefinite, because the typical sandy layers that mark the overlying beds in east Texas are not so characteristically developed in south­west Texas, and exposures are fewer. Where contacts can be ob­served the division is made where the clays give place upward to glauconitic, cross-bedded, sandy layers. The Reklaw formation has not been subdivided into small units, nor have its individual layers been studied or carefully traced in The Geology of Texas-Cenozoic Systems 623 the field. In east Texas it appears to consist of a single unit of clay containing thin glauconite heds, and sorne lignite. The char­acter of the strata of the Reklaw formation is shown in the following sections: Section112 o/ Reklaw /ormation in the Thompson No. 1 core test drilled by Humphreys Corporation in the northeast comer o/ William F. Williams Survey, Cherokee County, Texas. Thickness Feet Shale, gray with larninae of sand and a few thin layers of glau­ conite --------------------------------------------------------------------------------------5 Shale, brown with larninae of sand and stringers of glauconite containing fossil casts -----------------------------------------------------------------------20 Shale, brown with larninae of sand, clay, ironstone concretions, and casts of fossils __________ --------------------------------------------------------------------Glauconite, irnpure, sandy, containing a few fossils ____________________________ 4 Shale, brown, containing sorne sand and a few fossils _____________________ 8 Shale, brown, sandy, fossiliferous, containing thin stringers of glauconite ---------------------------------------------------------------------------------------------10 Shale, brown, sandy with lenses of glauconite containing echinoid spines and other fossils ___ --------------------------------------------------------------___ lSl/2 Shale, gray, containing srnall fossils___________________________________________________ 321h Glauconite, containing Bryozoa and rnany other fossils ____________________ 13 Shale, brown, fossiliferous, having larninae of gray sand_________________ 5 Shale, brown, containing lenses of glauconite ----------------------------______ 10 Shale, brown, sandy, fossiliferous___________________________________________________________ 6 Shale," brown, sandy, containing stringers of glauconite _____________________ 19 Total thickness rneasured__________________________________________________ 149 Section o/ the Reklaw fo rmation (499 to 552 /eet) in core test D--395 on the f. H. Strickling /arm, S. f. W est Survey, by Shell Oil Company and Penn Oil Company, Leon County. Thickness Feet Clay, chocolate-colored, contammg sorne greensand__________________________ 7 Clay, chocolate-colored, sandy, containing sorne greensand, c_oncre­tions, and fossils near the top and bottorn __________________________________________ 15 Greensand, clayey, containing concretions at bottorn. -----------------------13 Greensand, clayey ----------------------------------------------------------------------------------------2 Clay, chocolate-colored, with gr eensand, few fossils and concretions 14 Greensand, clayey --------------------------------------------------------------------------------------2 Total thickness ---------------------------------------------------------------------53 11"Dcscr;bed by Wendlandt and Knebcl. 1728, p. 1354, 1929. Sedimentology.-The sediments of the Reklaw formation were deposited in shallow water along a flat-lying or gently inclined coastal plain. In the east Texas embayment and in central Texas most of the sediments accumulated slowly in marine water not over 15 fathoms deep. In the south Texas area the waters were shallower, and during sorne of the time at least palustrine condi­tions existed and peat accumulated in swamps and lagoons that later became interbedded in the clay and silts, sorne of which are nonmarine. The chief distinction in sedimentation hetween the Reklaw and Carrizo and Queen City appears to be less clastic depo­sition due to less rainfall or lower stream gradients. During the Reklaw epoch much less sand was washed into the sea, the land was probably somewhat lower, and marine waters advanced farther landward in the embayments, working over and burying the Carrizo sands with finer sediments. The strand line appears to have oscil­lated somewhat, because in severa} areas, especially in the Río Grande district, lignite beds occur within marine sediments. Lithology.-The Reklaw formation in east Texas consists of about 90 per cent glauconitic clay, 8 per cent glauconitic sand, and 2 per cent impure lignite. The section consists essentially of stratified clay made up of thin beds of glauconitic, hlack, sandy clay, green glauconitic clay, and gray and yellow gypsiferous clay. The for­mation is marine in the embayment areas and partly nonmarine in the intervening areas. In south Texas the formation consists of about 70 per cent gray, brown, yellow, and red clay interbedded with 25 per cent of gray, green, and brown laminated, fine-grained sandstone and 3 to 5 per cent brown lignite. Samples of the sand examined under the micro­scope do not have grains larger than .589 mm. They are subangular and contain a larger percentage of glauconite than either the Queen City or Carrizo sand. Distinguishing characteristics.-The Reklaw formation can be distinguished from the adjacent formations by the following criteria: l. Deep red color of its soils. 2. Larger percentage of clay in its section. 3. Finer-grained, more glauconitic sand, the grains never over 0.6 of a mm. Grains from Carrizo in many places up to 2 mm. in size. The Geology of Texas-Cenozoic Systems 625 4. Fossils. In most places fossils are less numerous and smaller than those in the Weches and Crockett. 5. Interbedded lignites are less pure and browner than the lignites in the Rockdale formation. 6. Glauconitic layers are thinner and less prevalent than are those in the Weches or Crockett formation. Paleontology.-The first fossils from the Reklaw were named by Heilprin (701, pp. 393-406, 1891) from a collection of fossils sent him by R. A. F. Penrose, Jr., collected from Devil's Eye, a shoal in Colorado River about 8 miles southeast of Bastrop in Bastrop County. Since the time of Penrose very little work has been done on the paleontology of this formation. The beds are not very fossiliferous. Most of the fossils are in the form of casts or molds, which are poorly preserved and diffi­cult to identify. The fauna, as it is known from the collections obtained in the Colorado River valley, is characterized by small size of the fossils, predominance of gastropods, absence or scarcity of oysters, and small number of species of pelecypods. The most common forms are: Venericardia planicosta Lamarck Vol u tocorbis petrosa ( Conrad) Cornulina armigera (Conrad) Stucula gabbi Conrad Corbula sp. cf. C. smithvillensis Harris The complete fauna has not been studied or collected at all sys­tematically. The specimens from authentic localities in the Reklaw which have been identified' 13 · and deposited in the Bureau of Eco­nomic Geology are as follows: Dwnp at side of old "copper" prospect. Alsobrook land, Pallen SMvey, 4'Yi miles northeast of Harwood, Caldwell Cou.nty. Ancilla staminea (Conrad) Pleurotoma carlottae Harris Cancellaria sp. igaretus sp. Latirus aff. L. moorei (Gabb) Turritella n. sp. Murex sp. Turris cf. T. moorei (Gabb) Natica sp. Glycimeris sp. Pleurotoma cf. P. texanopsis Harris Venericardia cf. V. densata Conrad Corals, 3 spp. 113Jdcntifie L i .s bon Wi non a Ta 1 1 -h . t t - Fig. D"' " V ~ ' Fig. 41. Section along the Gulf Coast showing relationships of Eocene formations (adapted from Moody, 1125, p. 542, 1931). the Wilcox below and the Sparta above. In sorne parts of its section it has more glauconite than either the Wilcox or the Sparta sands. lt is thicker than the Sparta and somewhat more cross-bedded. In most places it contains less lignite, less carbonaceous clay, and fewer concretions than the typical Wilcox beds. It is somewhat finer textured than the Carrizo sand. Paleontology.-No invertebrate fossils have been reported from the Queen City formation. The carbonaceous clays in places contain a large assemblage of plant leaves, which in sorne places are well preserved. These have not been collected systematically or identi­fied, so far as known. The Geology of Texas-Cenozoic Systems 635 Correlation.-The stratigraphic position of the Queen City above the Reklaw and below the Weches suggests a correlation of this sand with part of the Cane River of Louisiana, the lower part of the . Winona of Mississippi, and the lower Lisbon of Alabama ( fig. 41). Economic resources.-The only economic resource of importance in the Queen City formation is underground water. The sand throughout east Texas and south-central Texas carries an abundance of pure water that furnishes good supplies to farms and small towns located south of its outcrop. WECHES FORMATIONu• Definition.-The name Weches was proposed by Wendlandt and Knebel (1728, p. 1356, 1929) to designate the prominent middle glauconite bed between the Queen City and Sparta sands of the Claiborne group, and it has been adopted by the tJ. S. Geological Survey for these beds, as shown on the new geologic map of Texas. Veatch (1688a, p. 127, 1902) referred to strata carrying a similar fauna, regarded as belonging to this formation, as Low Creek beds named for Low Creek south of Sabinetown, Sabine County. Deussen (415, p. 56, 1914; 421, p. 66, 1924) and Dumble (506, p. 66, 1918) described this glauconite bed in a number of localities as a member of the Cook's or Cook Mountain120 formation. Renick (1298, p. 531, 1928) referred to this bed as the San Augustine member of the Cook Mountain formation. Dumble (510, p. 428, 1924), however, had already used San Angustine as a group name to replace Ken­nedy's old term "Marine" to include ali strata from the top of the Wilcox group to the base of the Yegua (now Cockfield) and therefore Renick's name cannot be adopted. Miss Ellisor (523, p. 1341, 1929) used Wendlandt and Knebel's name in a paper on the correlation of the Claiborne group in Texas and Louisiana. Moody (1125, p. 536, 1931) designated these same strata Mount Selman, thus restricting the old definition and using it to include only strata between the 11•L1TERATVRE-Dumble, E. T., 461, pp. 303-326, 1891; 506, pp. 67-70 (Sabino River section), pp. 7:H!O (San Auguetine eection) , pp. 88, 89 (Alto eection), p. 90 (Hall's illuff eection), pp. 97-101 (Brazos River section), 1918. Burchard, E. F., 180, pp. 6~109, 1915. Price, W. A., and Palmer, K. van W., 1275, pp. 20-30, 1928. Ellisor, A. C., 523, pp. 1341-1343, 1929. Wen\!landt, E. A., and Knebel, C. M., 1728, pp. 1356-1359, 1929. Cushman, J. A., and Thomas,. N. L., 374, pp. 176-184, 1929; 379, pp. 33-41, 1930. Renick, B. C., and. Stenzel, H. B., 1299, pp. 8~91, 1931. l.Mfor a discussion of the spelling of this name, see Wendlandt and Knebel, 1728,' footnote, p. 1359, 1929. Qu~en City and Sparta sands. Renick and Stenzel (1299, p. 84, 1931) descrihed the Weches in a paper on the lower Claihorne of Brazos River valley. The fossiliferous greensand comprising the Weches formation is now recognized generally as one of the most significant units of the Claihorne group. lt is a persistent and easily recognized key hed for stratigraphic and structural mapping. Its glauconite and iron ores give it much economic importance. The type locality of the Weches has not heen definitely designated. Wendlandt and Knehel state, in their description of the formation, that iron ores of the upper heds of its section are well exposed in the Southern Pine Lumher Company's 75-acre tract in the W. F. Richardson Survey, 10 miles southeast of Palestine, Anderson County, and hence this might he regarded as the type locality. lt is hest known to geologists, however, at Alto, 10 miles northwest of Weches in Cherokee County, where it was descrihed by Kennedy (905, pp. 105-108, 1892), and at its well-known outcrop at Smith­ville on Colorado River. Its lower heds are hest exposed along Burleson Bluff of Brazos River near Collard's or Collier Ferry in the J. C. Rohinson Survey in northeastern Burleson County, where it has heen visited by geologists since the days of Penrose. Regional geology.-The Weches formation is essentially a section of glauconite and glauconitic clay, characterized by heds of hlack and hrown iron ore. The soluble ingredients of the glauconite leach out, and the iron hecomes concentrated in the form of hematite, siderite, and limonite in the upper layers. The resistant ferruginous heds cap hills and escarpments throughout most of the area of its outcrop in east Texas and produce a picturesque, rugged topography of steep, high, flat-topped hills dissected by deep V-shaped valleys. In central and south Texas, in places where the iron ore has not been concentrated, the unconsolidated beds weather to form rolling, open prairies with fields of rich, red soil in striking contrast to the oak-covered sand that characterizes the outcrops of the Queen City and Sparta sands. The Weches outcrops as isolated hills or along slopes and ridges covered by the overlying Sparta on the stream divides along the middle of the east Texas geosyncline (fig. 42). The formation has been mapped also in a rather tortuous helt fi:om Sahine River, south of Sahinetown, west:Ward through San Augustine, Nacogdoches, Weches, Palestine, and Centerville to Burleson Bluff 'in the northeast corner of Burleson County, thence southwest to The Geology of Texas-Cenozoic Systems 637 Smithville on the Colorado, thence through Oak Forest in Gonzales County, south of Floresville in Wilson County, through Pleasanton in Atascosa County, to Derby 'in Frio County. In Frio County and southward through the Nueces and Rio Grande valleys the Claiborne strata above the Queen City have not been differentiated, and the exact course of the outcrop in southwest Texas is not known. Weches in east Texas is 50 feet; the thickness in central Texas is about 30 feet. In well sections south of its outcrop the thickness ranges from 50 to 150 feet. The measurements of thickness in various localities are shown in the following table: LOCALITY CO UNTY THJCKNESS AUTHOR ITY Feet J. L. Bonner No. 1-A, Humble O. & R. Co., Wm. Elliott Survey_ Angelina 70 Wendlandt and Knebel Thompson No. 1, Humphreys Corp., W. F. Williams Survey_ Cherokee 53 Do South of Palestine Anderson 73 MacNaughton S. Pine No. 3-D, Humble O. & R. Co. ··-----······--------------------------­ Houston 145 A. C. Ellisor So. Pine No. 1-A, Humble O. & R. Co. -----·--------·--····--··----····------­ Trinity 150 Do Brazos River section___________ _________ Robertson 50-70 Renick and Stenzel Rainey No. l.____ _____ ___ ___________________ Cherokee 55 N. L. Thomas Outcrop, hill 15 mi. SE. of Buf­falo _···----··--------------------------------Leon 50 A. C. Wright Outcrop, northeastern corner of county __ _______________ ____ _:-_____________ Smith 50 Do Stratigraphy.-The Weches formation is described as the marine, fossiliferous, glauconitic beds between the Queen City and Sparta sands. The base is taken as the contact of the fossiliferous glau­conitic !ayer with the underlying gray, unfossiliferous sand. The basal contact in the east Texas basin and in the central Texas area is more or less conformable. In a few places, especially in Anderson County, a thin bed of glauconitic iron ore occurs at the base of the' Weches at its contact with the Queen City and suggests an old weathered zone between the two formations, and Stenzel reports a slight unconformity in Burleson and Leon counties. The contact on the flanks of the Sabine uplift, especially in exposures along Sabine River valley, is unconformable. The greensand rests upon the Reklaw, and eastward it overlaps the Reklaw and lies upon the Carrizo. The upper contact of the formation is marked every­where on the outcrop by layers of limonite and black, porous iron ore in contact with gray and bu:ff sand belonging to the Sparta formation. In most places the contact appears to be conformable. Stenzel has observed a slight discordance at the top of the forma­tion in Leon County. The Geology of Texas-Cenozoic Systems i639 The Weches formation in east Texas is made up of two divisions; (a) an upper division consisting of concretionary, ferruginous strata in which the glauconite has weathered and altered to iron ore, and (b) a lower bed containing more or less pure or clayey, fossiliferous glauconite free of quartz sand but interstratified with clay or marl. The same strata in central Texas hetween the Brazos and Colorado river valleys consist also of two divisions; (a) an upper division made up of impure glauconite containing sorne iron ore overlying a very pure, very richly fossiliferous glauconite con­taining large numbers of gastropods and having at its base a lentil of limestone, and (b) a lower division consisting of a layer of dark-gray or black glauconitic clay and a lower fossiliferous green sand containing large numbers of pelecypods and other fossils. The stratigraphy of the Weches in the different districts is best shown by the following described sections: Section121 o/ W eches formation on Sabine River about one mile above mouth o/ Low Creek a short distance south of Sabinetown, Sabine County. Thickness Ft. in. 4. Limestone, dark green, fill ed with large grains of green­ sand and containing large numbers of Pecten cornuus122· and crustacean remains ··-----------------------­---­---------------------­ 5 3. Greensand, fossiliferous, oolitic, containing spots of green clay, which weathers red -------------··--------------­----------------­-------· 7 2. Limestone, green, contll ining small, rounded, greensand grains, weathers red . ··············---------·---------------------·-·-----------­ 4 l. Oay, green, fossiliferous, containing much greensand ........ 10 Total section measured ...... ----------·-------------------------------­ 22 4 Section1 2a o/ W eches formation at Alto in southern Cherokee County. Thickness Feet 6. lron ore, laminated, and brown sand ... ___________________________________.10-15 5. Sand, brown, yellowish brown, altered, glauconitic, contain· ing streaks and nodules of calcareous material and a rich fauna of well-preserved fossils·----------·----·---------------------­6 l2tMcasured by Vca.tch, 1688a, pp. 127, 128, 1902. 122Now known as Pecten scintillatus Conrad var. corneoides Harris (668a, p. 28, 1919). 123.Measured b)'1 A. Dcussen. 415, p. 63, 1914; scc also descriptiens by Kennedy, 905,_ PP­ 105-109, 1892. Thickness Feet 4. Glauconite, yellowish brown, g:rayish brown, and grayish green, indurated, C-Ontaining rich fauna _________________________________ 20 3. Glauconite, green, containing casts of fossils__________________________ 6 2. Sandstone, brown, altered, glauconitic, containing casts of fossils ---------------------------------------------------------------------------------------------30 l. Glauconite, gr een, containing fish teeth and a fairly well-preserved fauna -----------------------------------------------------------------------8 Total thickness ------------------------------------------------------------------80--85 Section124 of W eches /ormation 800 to 1000 feet west of highway bridge across Colorado River at Smithville, Bastrop County, one o/ the most famous and most frequently visited Cenozoic fossil localities in Texas. Thickness Feet 12. Mari, green, glauconitic, fossiliferous______________________________________________ 2 11. Gree,nsand, indurated, fossiliferous__________________________________ -------------1 10. Mari, brownish black, fossiliferous, glauconitic -----------------------l 1h 9. Limonite, or indurated, weathered glaue-0nite -----------------------------14 8. Mari, brown, laminated, fossiliferous ---------------------------------------------4 7. Limonite, very hard, fossiliferous --------------------------------------------------2 6. Mari, green, glauconitic, fossiliferous ---------------------------------------------5 5. Limonite, or indurated, weathered glauconite ______________________________ 1 4. Mari, green, laminated, fossiliferous _____________________ ~--------------------------1 3. Unexposed ------------------------------------------------------------------------------------------10 About 20 feet beneath the bottom of this section at the mou~h of Gazley Creek about 1600 feet west of the bridge and separated from the above section by a small fault and w1conformity, a soft, white shell mar! outcrops at low water, if not covered by river mud. The section may be continued as follows: 2. Mari, green, highly glauconitic, mostly unexposed____________________ 20± l. Sand, white, medium grained. Beach sand containing a bed made up of a shell bank of white pelecypods belonging to the genus Pitaría and containing about 12 species of fossils, which have been described by Katherine Palmer (1275, pp. 20c--30, 1928) . Sorne of the shells are eroded by waves (?) 3 Total thickness of Weches formation at Smithville ___________ 57± IMMeuured by Deussen, 421, p. 701 1924. The Geology of Texas-Cenozoic Systems 641 Section125 o/ Weches formation along road 2 miles so1ah o/ courthouse at Floresville, Wilson County, Texas. Thickness Feet 10. Clay, red, forming the subsoil and containing yellow limestone concretions averaging 1 foot in diameter.___________________________________ 2 9. Limonite, red, siliceous____________________________________________________________________ 1h 8. Clay, red, sandy, weathered_______________________________________________________ 1 7. Limonite, red, siliceous_____________ -------------------------------------------------------1h 6. Clay, red, sandY--------·-----------------------------------------------------------------1 5. Sandstone, red, ferruginous, consisting of altered greensand _____ 1 4. Clay, red, ferruginous, containing limestone concretions 1 to 2 feet in diameter having septarian structure --------------------------3 3. Unexposed ____________:________________________________________________________________________ 8 2. Shale, brown, containing limestone concretions 1 to 2 feet in diameter --------------------------------------------------------------------------------------------15 l. Clay, reddish, sandy, exposed in creek bed ____________________________________ 3 Total section measured__________________________________________________ 35 Sedimentology.-The sediments of the Weches formation were deposited in moderately shallow, clear, marine waters, which deep­ened as the epoch advanced. The rolled and wave-worn shells at the base of the formation indicate a shallow littoral or beach facies. The thick beds of glauconite rich in fragile, perfectly preserved gastropod shells of the upper strata indicate an off-shore facies in which the water was 200 to 600 fathoms deep, where animal life was very abundant and where little coarse sediment of any kind was deposited. The material that accumulated was fine, calcareous ooze and colloidal silicate in the form of iron potassium silicate (K, Fe, Si20 6H20) which in the presence of sea water precipitates in the form of glauconite grains. The exact process of formation has been much discussed by geochemists and geologists.126 WMeasured by Deussen, 421, p. 62, 1924. U8S1CNIFICANT LITERATUBB ON CLAUCON1n-Murray, J.• Deep sea deposite: Challenger Exped., p. 383, 1891. BaHey, J. W.• On the origin of greensand and its fonilation in tbe oceana of the present epoch: New Jersey Geol. Survey Ano. Rept.• p. 219, 1892. Clark, W. B., A preliminary report on Cretaceous and Te.rtiary formations of New Jersey with special reference to Mon­mouth and Middlesex counties: New Jersey Geol. Survey Ano. Rept., pp. 167-245, 1892; Origin and classification of the greeneande of New Jersey: Jour. Geol., vol. 12, pp. 167-177, 1894. Clark, F. W., The composition of glauconite and greenalite: U. S. Geol. Survey ·Mon. 43, pp. 243--247, 1903. Prather, J. K., Glauconite: Jour. Geol., vol. 13, pp. 509-513, 1905. Collet, L. W., and Lee, G. W., Researches on glauconite: Proc. Roy. Soc. Edinburg, vol. 26, pp. 238-278. 1906. Caspari, W. A.,. Contributions to the chemistry of eubmarine glauconite : Proc. Roy. Soc. Edinburgh, vol. 30, pp. 364--373, 1910. Palmer, Chase, Genesis of glauconite: Geol. Soc. Am. Bull, vol. 25, p. 91, 1914. Goldman, M. l., The petrography and genesis of the sedimenta of the Upper Cre· taceous of Maryland : Maryland Geol. Survey Rept., pp. 111-182, 1916. Audley, J. A., Silica Latest ideas are that the glauconite grains precipitate out of sea water around a minute nucleus according to the method of forma­tion of minute concretions or oolites. The chemical reactions appear to b~ a replacement of Al ions from aluminum silicate by Fe and K ions. The K ions are probably present in the sea water as soluble potassium salts; the Fe ions are thought to be produced by reduction of insoluble iron mineral matter by organic compounds produced by decomposition of animal or plant matter. At an anode (nucleus) set up by the reduction of ferric to ferrous ions, Si02 molecules are precipitated forming a colloidal iron silicate. This colloid absorbs potassium and traces of other positive ions to form a double silicate. Clark thinks that after i:he reduction of the iron, colloidal ferrous hydroxide forms first, and that this colloid absorbs and reacts with K and Si02 ions to produce the double salt, potas­sium íron silicate. In either case the final product is a colloidal silicate, which takes on a more or less spherical shape. The precipita­tion may take place inside the shell of a minute fossil in such way that the glauconite filling is a perfect cast of the interior of the shell. Murray found that glauconite is forming today abundantly in water below the mud line at depths of 100 to 900 fathoms where deposition is slow and where there is little land-derived sediment. Lithology.-The Weches formation along the outcrop consists of about 55 per cent glauconite, 30 per cent glauconitic clay, 10 per cent glauconitic sand, 4 per cent clay, and 1 per cent iron ore, mostly in the form of limonite. The glauconite consists of dark­green or greenish-black spherical, oval, and elongate grains that average 1 mm. in size. Sorne have the shape of minute fossils and are the casts of the interior of fossil shells, but by far the greater portion resemble rounded sand grains, sorne of which are nearly perfect spheres and have the appearance of oolite. The chemical analysis (Schoch, 1378, p. 170, 1918) of typical samples of the glauconite is given in the following table. and the silicates, pp. 6, 27, 29, 30, 101-102, and 172, London, 1921. H11mmel, K., Glauconite, a recent example of iron enrichment through chemical precipitation from eea water: Geol. Rund. echau, vol. 13, pp. 41-81, 97-136. 1922. Berz, C., Researches on glauconite: Neues Jahrbuch Min. etc., pt. 2, p. 207, 1923. Clark. 'F. W., Data of geochemistry: U. S. Geol. Survey Bull. 770, pp. 519-522, 1924. Twenhofel. W. H., Treatise on sedimentation, pp. S36-34I, Baltimore, 1926. Gill. J. E., Origin of the Gunflint iron-bearing formation: Eeon. Geol., vol. 22. pp. 719-722~ 1927. Schneider. Hyram, A study of glauconite: Jour. Geol., vol. 35, pp. 289-301, 1927. The Geology of Texas-Cenozoic Systems 643 LOCALITY PERCENTAGE CoMPOSITION P,03 Si02 AI,0 3 Fe,0 3 Feo MgO CaO Na20 K,O H20 Mount Selman, Cher­okee Co. o.oo 20.95 16.28 47.62 1.46 1.81 3.94 0.93 3.65 1 mi. s. of Palestine, Anderson Co. --------4.21 9.20 7.48 15.31 29.51 3.1 Neru· Dialville, Cher­okee, Co. ----0.54 14.40 2.07 56.23 5.00 3.05 Tr. 4.61 14.0 ~ mi. S.E. of Nacog­ doches, acogdoches Co. 0.41 30.5 24.47 4.93 14.49 3.66 2.31 Tr. 2.05 17.00 1 mi. S.W. of Chireno, N acogdoches Co. ·---Tr. 34.10 14.58 2.06 14.94 3.68 8.28 2.03 0.68 19.0 ear San Augustine. San Augustine Co._ 0.12 37.50 8.89 32.33 0.80 2.39 0.65 0.99 13.02 The high percentages of Al20 3, MgO, and CaO show that ali the glauconite is impure. The samples from the Weches, with the ex­ception of the one from Dialville, are ali low in potash and high in aluminum oxide. The glauconite; where it exists in beds, is for the most part free of sand but contains sorne fine, argillaceous clay or marl and an abundance of fossil shells. lt weathers to a brownish-buff and dull brick-red color and forms dark·red soils. In sorne places in central Texas the Weches formation contains a thin layer of impure fos­ siliferous glauconitic limestone. The clay in most places is light gray, thin-bedded, and fine~grained and contains small flakes of mica, fossil shells, and spherical grains of glauconite. The iron ore is altered glauconite in which the iron has been concentrated either by leaching out of the potash and silicates, a process that leaves the iron oxide in the form of a black, honey-combed, porous layer 1 to 3 feet thick, or the iron has dissolved and precipitated as a limonite seam along porous layers. It occurs also less commonly in the form of carbonate as round, biscuit-shaped concretions in impervious beds. The iron ore occurs in the upper few feet of the outcrop following the contour of the surface of the ground without regard to the bedding planes of the strata. The ore is found capping the hills and mesas at or a few feet beneath a sand-covered surface. In central Texas and in well sections south of the outcrop, the Weches beds contain a smaller proportion of glauconite, much less iron ore, and more marl and thicker beds of fossiliferous, glauconitic clay. In central and south Texas the clay in places contains smooth, hard, nodular, ferruginous concretions 6 inches to 1 foot in diameter which have peculiar botryoidal shapes. Samples of the W eches formation examined under the microscope are found to contain a larger proportion of spherical glauconite, less plagioclase feldspar, fewer heavy minerals, except leucoxene and ilmenite which are common, less pyrite, and fewer carbonate minerals than samples from most other marine formations in the Claiborne. Distinguishing characteristics.-The Weches formation is dis­tinguished easil y by the following criteria: l. Iron ore. The bands of black, porous, and honey-combed layers of iron ore capping thick beds of glauconite and glauconitic clay are characteristic of the Weches formation. 2. Red soil. The deep brick-red soil which . colors the fields, the roads, and landscapes of east Texas help to distinguish this formation from the gray, sandy, and brownish soil of the Queen City below and Sparta above. 3. Glauconite. The glauconite· beds are thicker, purer, more per­sistent, and more fossiliferous in the Weches than in other Claiborne formations. 4. Fossils. Certain index fossils, especially Vertagus wechesensis Stenzel, Turritella fem.ina Stenzel, Rimella texana Harris, Latirus singleyi Harris, and Scutella m.ississippiensis Twitch­en,127 are index fossils of the Weches. Paleontology.-The Weches formation is one of the most richly fossiliferous Cenozoic formations of the Gulf Coastal Plain. In number of species it is surpassed only by the Crockett. Many of its fossils are hard and well-preserved original shells, which occur in large numbers. The outcrops of the Weches along the Texas rivers have delighted fossil hunte,rs since the days of Roemer. The most famous localities are as follows : LOCAL!TY COUNTY ZONE Low Creek south of Sabinetown.____________________ Sabine Upper Roadside exposures east of San Augustine____ San Augustine Middle Vicinity of Alto ---------------------------------------------------Cherokee Upper Hall's Bluff on Trinity River.____________________________ Houston Lower Robbins-Centerville road, 0.6 of a mile east of Robbins -------------···-···-··---------------------------------Leon Complete section Bl uff at old iron bridge on Navasota River.... Leon Upper Burleson Bluff on Brazos River._ _______________________ Burleson Lower Bluff on Colorado River, Smithville -------------·---Bastrop Middle and upper Gazley Creek, Smithvill e ----------------------------------Bastrop Lower mcommonly referred to in literature as Scutella. caput-sinensis Heilprin (see Stenzel, 152Sd.. p. 318, 1932). The Geology of Texas-Cenozoic Systems 645 The following list of fossils from Smithville is representative of fossils that occur128 in the middle and upper beds of the Weches formation: Foraminifera129_ Spiroplectammina zapotensis (Cole) Textularia afI. tumidula Cushman Quinqueloculina yeguaensis Wein­zierl and Applin Triloculina trigonula (Lamarck) Lenticulina alato-limbata (Gümbel) Guttulina problema d'Orbigny Globulina inaequalis Reuss Sigmoidella plummerae Cushman and Ozawa onionella sp. Bolivina cf. B. gracilis Cushman and Applin Discorbis yeguaensis Wienzierl and Applin Eponides guayabalensis Cole Eponides exiguus (H. B. Brady) Anthozoa1ªº-Platytrochus stokesi (Lea), C Discotrochus orbignianus Milne­ Edwards and Haime, C Turbinolia pharetra Lea, C Gastropoda1ªº-Cylichna kelloggi ( Gabb), C Terebra houstonia Harris, C Conus smithvillensis Harris, C "Turris" nodocarinata Gabb, C "Turris" moorei (Gabb) "Pleurotoma" huppertzi Harris "Pleurotoma" huppertzi var. pen­ rosei Harris "Pleurotoma" insignifica Heilprin "Pleurotoma" finexa Harris "Pleurotoma" rebeccae Harris "Pleurotoma" vaughani Harris "Pleurotoma" enstricrina Harris Drillia prosseri Harris Drillia texanopsis Harris, C Microdrillia infans ( 1eyer). c Ancistrosyrinx bella (Conrad) "Eucheilodon" reticulatoides Harris Cancellaria bastropensis Harris, C Cancellaria penrosei Harris Siphonina claibornensis Cushman Lamarckina yeguaensis Cushman Gyroidina soldanii var. octocamer­ ata Cushman and G. D. Hanna Asterigerina afI. A. bracteata Cushman Amphistegina cf. A. californica Cushman and G. D. Hanna Ceratobulimina eximia (Rzehak) var. Globigerina sp. Globorotalia cf. G. crassata (Cush­ man) Anomalina sp. Anomalina costiana Wienzierl and Applin Cibicides pseudowuellerstorfi Cole Paracyathus alternatus Vaughan Oculina singleyi Vaughan Madracis johnsoni Vaughan Balanophyllia irrorata var. mortoni (Gabb and Horn) Trigonostoma panones (Harris) Trigonostoma panones var. smith­villensis (Harris) Trigonostoma panones var. junipera (Harris) Volutocorbis petrosa (Conrad), C, R Volutocorbis dalli (Harris) Lapparia dumosa Conrad Conomitra poli ta (Gabb), C Pyramitra costata (Lea), C Pseudoliva vetusta (Conrad), C Levifusus trabeatoides Harris, C Fusinus bastropensis (Harris) Euthriofusus mortoniopsis (Gabb), c Latirus moorei (Gabb) , C Alectrion scalatus (Heilprin) Astyris bastropensis Harris, C Murex vanuxemi Conrad Ficopsis penita (Conrad ) 12SCapital letters after fossil names indicate occurrence also in the Crockett (C) formation and Rcklaw ( R) formation. 129List made by Helen Jeanne Plummer. l\fatcrial collected from dark glauconitic and fossilifcrous clay near the topi oí the section exposed upstream from the bridge at Smithville. 130The names of the Antho¡r.oa and Gas tropoda have becn fumishcd by H. B. Stcnzel. Turritella nasuta Gabb, C Tuba antiquata (Conrad), C Architectonica al vea ta (Conrad) Liotia tricostata Conrad, C Vertagus wechesensis Stenzel Clavilithes kennedyanus Harris Scaphopoda-Dentalium minutistriatum Gabb Cadulus abruptus Meyer and Ald­rich Pelecypoda-Ostrea alabamiensis Lea Ostrea sellaeformis Conrad var. smithvillensis Harris Pecten burlesonensis Harris Trinacria pulchra (Gabb), C Trinacria decisa (Conrad) Arca ludoviciana Harris Arca reticulata Gmelin Nucula magnifica Conrad Venericardia rotunda Lea, C Venericardia rotunda Lea var. flabellum Harris Pyramidella ha tropensis Harris Natica semilunata, Lea, C Neverita arata (Gabb), C Sinum arctatum (Conrad) Sinum bilix (Conrad), C Venericardia rotunda Lea var. coloradonis Harris Lirodiscus smithvillensis (Harris), C Crassatellites antestriatus CGabb), C Crassatellites trapaquarus Harris Sphaerella anteproducta Harris Callocardia texacola (Harris) Tellina tallicheti Harris Corbula deusseni Gardner Corbula smithvillensis Harris, C, R The following list from Burleson Blufl on Brazos River is repre­sentative of the fauna of the lower Weches181 (identified by H. B. Stenzel, 1299, pp. 106-108, 1931): Gastropoda­"Pleurotoma" huppertzi Harris var. penrosei Harris Surcula n. sp., cf. S. gabbi (Con­ rad), UW Oliva bombylis Conrad Mitra cf. M. dubia (H. Lea) Volutocorbis petrosa (Conrad), uw Fusus interstriatus Heilprin? Clavilithes chamberlaini Grabau and Johnson Clavilithes papillatus ( Conrad) Clavilithes kennedyanus Harris? Metula brazoensis Johnson Pelecypoda-Corbula engonatoides Gardner Tellina tallicheti Harris var. Meretrix texacola Harris Cardium claibornense Aldrich Venericardia planicosta Lamarck, uw Venericardia trapaquara Harris var. texalana Gardner Pyrula penita Conrad, UW Cassidaria brev:identata Aldrich Rostellaria ( Calyptraphorus) velata ( Conrad) Rimella texana Harris Rimella texana Harris var. plana Harris Xenophora conchyliophora (Born) Natica limuia Conrad Natica mamma Lea Neverita arata (Gabb) Tuba antiquata (Conrad) Sinum (Sigaretus) hilix Conrad Calyptraea aperta (Solander) Pecten burlesonensis Harris Ostrea sellaeformis Conrad, UW Ostrea alabamiensis Harris (non Lea) Arca deusseni Gardner lSl.The aymbol, UW, after some of thé fo11il namea indicate• occurrence also in tbe upper '\Vecheo. The Geology of Texas-Cenozoic Systems 647 Scaphopoda-Dentalium minutistriatum Gabb, uw Anthozoa- Turbinolia pharetra Lea, UW Balanophyllia . irrorata ( Conrad) , Platytrochus stokesi (Lea), UW uw Paracyathus alternatus Vaughan, Balanophyllia irrorata var. mortoni uw . (Gabb and Horn) , UW The fauna of the upper Weches, exemplified by collections from Smithville at the Bureau of Economic Geology, contains 8 corals, 47 gastropods, 2 scaphopods, and 19 pelecypods. Of these, 37 species or about half occur also in the Crockett, whereas only about 3 per cent are found in the Reklaw. The fauna of the lower Weches represented by the species from Burleson Bluff contains 4 corals, 22 gastropods, 10 pelecypods, and 1 scaphopod. Only 10 species, or about 25 per cent of the total number of species, occur in the upper Weches. The similarity of the upper Weches and lower Crockett is due probahly to similarity of facies and environ· mental conditions. The upper Weches and lower Crockett faunas in central Texas are moderately deep-water, off-shore assemblages. The lower Weches is a near-shore, littoral fauna. Three fossil zones have heen recognized in the Weches formation: 3. Upper zone characterized by Calyptraphorus velatus Conrad, Turritella femina Stenzel, Vertagus wechesensis Stenzel, and by the abundance and excellent preservation of. its gastropods. Z. Middle limestone lentil, which occurs in San Augustine County and can be traced eastward to Sabine River; especially char­acterized by Scutella mississippiensis Twitchell (see footnote 126) . l. Lower zone characterized by large numbers of Anomia ephip­poides Gabb, numerous shells of Pecten burlesonensis Harris, and a small variety of Ostrea sellaeformis Conrad described by Stenzel (1299, p. 87, 1931). Correlation.-The Weches formation is absent on top of the Sahine uplift in Louisiana, hut according to Miss Ellisor (523, p. 1344, 1929) it occurs north of the uplift in Arkansas. Also the fauna of the heds in the vicinity of Minden and Mount Lehanon on the east side of the uplift appears to be related to the Weches. The Weches formation is apparently equivalent to the Mount Selman as restricted by Moody (1125, p. 538, 1931), the upper Winona of Mississippi, and the middle Lisbon of Alabama (fig. 41). Economic resources.-The economic resources of the Weches for­mation are iron ore, glauconite, and petroleum. The iron de­posits132 are estimated to amount to more than a billion tons. These deposits were well known and worked on a small scale before and during the Civil War. During the reconstruction period that fol­lowed the Civil War, the mines fell into disuse and were not op­erated again till the 70's. In 1870 the Loo Ellen (or Kelly) fur­nace, located 5 miles north of Jefferson in Marion County was put into blast and operated for a decad'e. In 1891 another charcoal blast furnace having an annual capacity of 13,500 tons was in­stalled on the north edge of the town of Jefferson and was operated until about 1900. In 1884 a blast furnace was opened on Texas state land about three-quarters of a mile ·northeast of Rusk in Cherokee County. lt was designed for an output of 25 tons a day and was operated by convict labor until 1909. The Tassie Belle furnace was built s,outheast of Rusk in 1S90 and the Star and Crescent three-quarters of a mile east of Rusk in 1891. This fur­nace had a capacity of 18,000 tons of iron annually and was op­erated until 1907. Pig iron of good grade was turned out and used at Marshall for manufacture of car wheels. Since that date mining and smelting operations have been allowed to fapse, and the great reserves of low-grade iron ore remain for future indus­trialists of the state to develop. The distribution · of the iron-bearing formation is shown in figure 42. The richest beds are found in the upper member of the Weches formation around the rim of ridges and mesas capped by ledges of ferruginous sandstone. Ali the. outcrops are located in the trough of the east Texas geosyncline. The ore occurs in three forms: l. Soft, brown, laminated limonite in beds from 1 inch to 4 feet thick. 2. Curly, honey-combed, hard, black, residual limonite in sheets and layers. 3. Concretionary nodular ore of limonite or carbonate in the form of botryoidal, bulblike concretions in the glauconitic beds. l::S2LI'fERATURE ON IRON ORE DEPOSITS-Johnson, L. c., 880, pp. 1-54, map, 1888. Penrose, R. A. F., 1189, pp. 65--89, 1890; 1191, pp. 44-50, 1892. Birkinbine, John,116, pp. 33-37, 1891. Walker, W. B., 1705, pp. 225-300, 1891. Dumble, E. T., Kennedy, Wm., et al, 461, pp. 7-326, map, 1891. Kennedy, Wm., 910, pp. 258-288, 862, 863, 1895. Eckel, E. C., 514, pp. 348-354, 1905. Phillips, W. B., The iron ore resources of Texas: Eng. Soc. West Penn. Proc., pp. 64-79, March, 1902; Tbe iron situation in east Texas: Mio. World,. p. 994, Nov. 26, 1910. Linton, Robert, 1000, pp. 1153-1156, 1913. Burcbard, E. F., 180, .PP· 69-109, map, 1915. The Geology of Texas-Cenozoic Systems 649 The ore consists chiefly of brown hydrated sesquioxide of iron (2Fe20 3-3H20) with a minor amount of nodular carbonate ore (FeC03 ) in the lower layers helow the oxidized zone (fig. 43). Both the oxide ore and carbonate ore contain more or less silica and alumina and other impurities, as shown by the following analysis: Average compositionl33 Per cent Metallic iron -----------------------------------------------54.91 Silica -----·--------------·-·--·------------------------·-----------------5.18 Alumina -------·--------------------···---------------------------------4.30 Phosphorus ------------------------------------------------------.073 Su!ph ur ----------------------··-------------------------------·--·---------------------.067 5' Soil, sand,and grave! Limoni+e lo' Glaucon"itic sand Glaucon·1+ic sandy clayLimonite. and glauconitic sand !ron carbonate Clay Sand Fig. 43. Columnar section showing occurrence of iron ore on Surralt tract, Cass County (after Burchard, 180, p. 79, 1915 ) . The ore occurs in a more or less continuous laminated bed that varies from I % to 4 feet thick near the top of bilis and in upper portions of small branch gullies cutting back into the flat-topped divides. lt is in the form of lenses and ledges, sheets and layers, and in the lower beds in nodules, everywhere associated or inter­bedded with oxidized glauconitic sand. The ratio of ore to barren material in average exposures is about 25 to 30 per cent of ore by volume or about 40 to 50 per cent by weight. No cheap method for removing barren rock has been developed. Hand picking renders l81phillips, W. B., lron and eteel malcing in Texas: Iron age, Jan. 11, 1912. Average composi· tion from 65 samples from Marion County. the process too expensive to meet competition of other mining dis· tricts under present conditions. The ore has been mined by strip­ping off the surface sand from 1 to 6 feet deep with wheel scrapers, blasting the consolidated layers by light charges of dynamite, separating the best ore trom the glauconite by hand, loading and transporting it by trucks or trams to the furnace. If a cheap method can be developed to concentrate the ore-bearing material, hand­picking can be abolished, and the whole operation of handling the ore can be reduced to the work of machinery, and the iron-ore de: posits can be developed. Perhaps when sufficient demand for these ores arises, methods will be devised for handling economicall y this vast store of potential iron. The glauconite of the W eches formation is one of the largest de­posits in the United States. lt is low in potash and phosphoric acid. Most samples have less than 2 per cent K20 compared with 4 per cent in the Midway glauconite, and 5 per cent in much of the glauconite in New Jersey. Consequently this deposit is not suit­able for fertilizer or for the manufacture of potash. The purer deposits can be utilized as water softeners that employ the zeolite process.1 3 4 Zeolite softening has displaced practically ali other methods of water softening in industrial plants and for domestic use. Processed greensand is the best possible zeolite. lt softens water as fast as it can be forced through it, will operate with waters containing C02, and is not injured by turbid, iron-bearing waters. The process of preparing the material is simple, and glau~onite should find a market · with concerns manufacturing zeolite for softeners. Oil occurs in the W eches formation in the shallow Chireno field southeast of Nacogdoches, where it has been developed on a small scale since 1877. The occurrence, however, is more of historie than of economic interest, since all the wells are shallow and small 1ML1TERATURE ON ZEOLJTE WATER SOFTENERs-Barthel, E. L., Preparation of zeolite water· softening material: lowa Acad. Sci. Proc., vol. 31, pp. 275-276, 1926. Behrman, A. S., Recent developments in zeolite softening: Jour. Ind. Eng. Chem., vol. 19, pp. 445-447, 1927. Kneeland, H. C., Water softening on a large scale by the zeolite proceea: West Virginia Coll. Eng., Tech. Bull. l, pp. 66-74, 1927. White, A. H., Walker, J. H., Partridge, E. P., and Collin1, L. F., Zeolite water treatment in a large central beating plant; Jour. Am. Water Works Aesoc., vol. 18, pp. 219-249,. 1927. Camphell, J. T., and Davis, D. E., Softening municipal water supplies by zeolite: Jour. Am. Water Works Assoc., vol. 21, pp. 1035-1053, 1929. Shreve, R. N., Greensand u a water softener: U. S. Bur. Mines Bull. 328, pp. 3o-43, 1930. The Geology of Texas-Cenozoic Systems 651 producers. In the deep wells on the coastal and near-coastal salt domes, the Weches is thought to be a clay or mar!, and the oil, if present in the Claiborne, is found in the adjacent Sparta and Queen City sands (see sections by Heath, Waters, and Ferguson, 696, pp. 52-53, 1931). SPARTA FORMATION""' Definition.-The Sparta sand was first defined by Vaughan136 as deep quartz sand extending across Louisiana and well developed near Sparta in Bienville Parish. V aughan confused sorne of the Pleistocene sands, so plentiful in eastern Louisiana, with the Sparta, for he states "These sands overlap both the lower Claiborne and the Grand Gulf extending entirely across the Jackson and Vicks­burg." Since he gave the type locality as Sparta, Spooner187 arnended the original definition to include only the Claiborne sands that occur at the sarne stratigraphic position as those near Sparta. This section includes about one hundred feet of strata above the fossiliferous red clays. Miss Ellisor (523, p. 1345, 1929) has cor­related these sands with those overlying the Weches forrnation in Texas and has retained the Louisiana name for the beds of the same age in Texas. This name Sparta was used at the same time by Wendlandt and Knebel (1728, p. 1359, 1929), who made these sands the lower member of the Cook Mountain formation. Renick (1298, p. 531, 1928) preferred the name Nacogdoches, which had been given by Dumble (506, p. 67, 1918) to the transition beds between the Cook Mountain greensand and the gypsiferous clays of the Y egua. Dumble at this time regarded the beds lying above the Sparta and known now as Crockett as the marine Yegua. Dumble's narne Nacogdoches therefore appears to be a synonyrn for Vaughan's older narne Sparta as restricted by Spooner. Since sorne doubt exists as to just what Dumble intended to include in his "transition" beds, and since the name Sparta was in good usage in D5L1TERATUP.z-Vaughan, T. W., A hrief cootribution to the geology and paleontology of northwestem Louisiaoa: U. S. Geol. Survey, Bull. 142, pp. 25, 26, 1896. Spooner, W. C., Interior salt domes of Louisiana : Bull. Amer. Assoc. Pet. Geol., vol. 10, p. 235, 1926. Ellisor. Alva, 523, pp. 1338 and 1341, 1929. Weodlaodt, E. A., aod Koebel, M. G., 1728, pp. 1359­1360, 1929. Reoick, C. B., aod Stenzel, H. B., 1299, p. 90,. 1931. l.38Vaughan, T. W., A brief contribution to the geology and paleontology of northwestern Louiaiaoa: U. S. Geol. Survey, Bull. 142, pp. 25, 26, 1896. l87Spooner, W. C., JntPrior ult domes of Louisiana: Amer. Assoc. Pet. Geol. Bull., vol. 10, p. 235, 1926. Louisiana, Miss Ellisor and Wendlandt and Knebel have been justi­fied in dropping the name Nacogdoches. Sparta has since been recognized by Renick and Stenzel (1299, p. 90, 1931) and by the U. S. Geological Survey on the new geologic map of this state. Regional geology.-The Sparta formation in east Texas occurs on the high ridges above the greensand beds and caps most of the ferruginous hills along stream divides in the ea,st Texas syncline. In central Texas it forms a belt of moderate relief characterized by sandy soils and post oak timber. The formation has been mapped in a continuous belt from Columbus, Louisiana, south of Sabinetown to the center of the west line of Lee County. The average width of the outcrop in east Texas is two and one-half miles, except in the east Texas basin, where it widens to ten miles or more in Houston and Anderson counties. Southwest of Lee . County it narrows to one mile and continues southwestward in a belt from one to one and one­half miles wide to the valley of Lucas Creek in northeastern Atascosa County. South of the outcrop it has been recognized in well sections as far south as Clay Hill salt dome and doubtless constitutes one of th.e deep oil sands on sorne of the coastal domes. In southwest Texas it occurs in well sections in LaSalle and McMullen counties. The Sparta formation in east Texas varies in thickness from 230 to 300 feet, as shown in the following table: LOCALITY COUNTY TH'ICKNESS AUTHORITY Feet J. L. Bonner, No. 1-A, Humble O. & R. Co,______________________________ Angelina 242 Wendlandt and Knebel So. Pine No. 4-A, Humble O. & R. Co. -----------------------------------------Houston 250 Alva Ellisor So. Pine No. 2-A, Humble O. & R. Co. ----------------------------------------Trinity 275 Do Outcrop section, Brazos River Valley ------------------------------------------Robertson 300--350 Renick and Stenzel Schirmer No. 1, Sun Oíl Co., Clay Creek --------------------------------Washington 150 J. A. Waters Stratigraphy.-The Sparta sand in Texas lies apparently con­formably upon the Weches formation and is overlain disconform­ably by the Crockett. In Louisiana, according to Spooner's section, it separates the Cane River and St. Maurice formations. In most The Geology of Texas-Cenozoic Syste?ns 653 places where penetrated by the drill or studied at good exposures on the outcrop the formation appears to be a stratigraphic unit made up largely of sand and sandy clay. The top of the formation is placed at the contact of chocolate-colored, glauconitic, ferru­ginous, fossiliferous sand of the Crockett formation with the coarser­grained, more carbonaceous, nonfossiliferous beds of the S'parta. The fossiliferous glauconitic sand named "Eaton lentil" by Renick and Stenzel is regarded as the lower part of the overlying Crockett. The base of the Sparta formation is placed at the contact of gray sand with green or reddish-yellow, glauconitic and iron-bearing beds. In the southern part of Smith County and in the vicinity of Tyler a glauconite layer about 120 feet above the base of the Sparta -can be traced for sorne distance. This stratum is thought by Wend­landt and Knebel (1728, p. 1359, 1929) to be a lentil in the Sparta but by other geologists to represent the lower layer of the overlying Crockett. The fact that it occurs only in the basin where the Sparta would normally be thickest and has only .about 120 feet of sand be­low it in any area where the normal section of the Sparta is fully 250 feet thick is evidence in favor of a Sparta age for the lentil. The member has been named Tyler greensand by Wendlandt and Knebel. The stratigraphy of the Sparta formation is best described by the following sections: Section o/ Sparta sand in Humble Oíl and Refining Company's No . 1-A, William Elliott Survey, Angelina County. Thickness Feet Sand, partly consolidated ····-··· ·-----------------------···---------------------------------------11 Shale, sandy ---------------------------·----------···---------------------------------------------------20 Sand, brown -----------------------------------------------------------------------------------------------~ 31 Rock ---·------------------------------------------------------------------------------------------------------2 Shale, sandy -----------------------------------------------------------------------------------------------6 Shale, sticky -------------------------------------------------------------------------------------------15 Sand, gray and brown, containing streaks of lignite._________ ________________ 19 Shale, hard -------------------------------------------------------------------------------------------------2 Sand, brown, containing streaks of lignite___________________ _ ____________________ 53 Shale, hard, sticky____________________________________________ __________________________ 15 Sand ··-·····---------------------·-------------------------------------------------------------------------------41 Shal e, sticky ---------------------------------------------------------------------------------------------20 Sand, brown ----------------------------------------------------------------------------------------------7 Total thickness measured.____________________________________________________ 242 Sedimentology.-The sediments of the Sparta sand are thought to be mostly continental in origin. The basal sands were laid clown on a beach and coastal plain in conjunction with the withdrawal of the Weches sea. The middle sands are mainly fluviatile deposits spread broadly over a flat terrain. The upper sediments were de­positea along a transgressing shoreline laid clown in advance of the Crockett sea and were worked over by later marine waters. Strata of such an origin138 wedge out seaward and expand land­ward. The basal and upper layers show shore conditions with beach sands, dune deposits, and interfingering shallow deltaic strata. Cross-bedding formed by streams and river-made ripple marks are noteworthy in the middle beds. Thin laminae made up of the remains of land and marsh plants also occur there, but there are no layers of lignite of any thickness. Lithology:-The Sparta formation consists of about 70 per cent sand, 25 per cent sandy shale or clay, 3 per cent glauconitic sand, 1 per cent limonite, and 1 per cent lignite. The sand is gray or buff, and in places where it contains sorne glauconite it weathers to reddish hues. It is nearly everywhere laminated and in sorne places decidedly cross-bedded. It consists of round and subangular quartz grains about 0.5 mm. in diameter mixed with a small percentage of exceedingly fine grains. In most places the sand is unconsolidated and erodes easily to form rounded uneven slopes. In a few places where it contains ferruginous material it is consolidated into thin ledges impregnated with limonite. The clays are most prevalent in the upper part of the formation. They are gray or chocolate­colored and contain considerable carbonaceous matter. Distinguishing characteristics.-The following criteria are useful m identifying the Sparta formation: l. Lack of compactness. The Sparta sand is distinguished by its loose, unconsolidated makeup. It does not form cliffs or steep banks, and in drilling will not hold together in a core barrel. 2. Brown ca1·bonaceous matter. The carbonaceous clays are choco­late-colored and the plant remains are brown, not black like those of the Carrizo. 3. Paucity of limonite and greensand. The small amount of limonite and glauconite as compared with the iron ore and glauconitic 138Grabau, A. W.. Principles of stratigraphy, pp. 734-738, A. G. Seíler and Co., New York, 1913. The Geology of Texas-Cenozoic Systems 655 beds of the Weches and Crockett distinguish the Sparta sand from the forrnations above and below. 4. Absence of fossils. There are very few marine fossils and no richly fossiliferous beds in the Sparta sand like those so com­rnon in the Weches and Crockett formations. Correlation.-The Sparta formation is correlated with the Sparta sands of Louisiana, with strata in the Kosciusko formation in Mis­sissippi, and with strata in the upper Lisbon formation in Alabama (fig. 41). Economic resources.-The chief resources found in the Sparta sand are water near its outcrop and oil in deep wells located on or near salt domes. According to Heath, Waters, and Ferguson (696, p. 53, 1931) the upper producing sand on the Clay Creek dome in Washington County is in the Sparta formation. Doubtless it yields oil in other wells of the northern coastal domes. The sand along its outcrop and for a distance of 25 miles south contains a good supply of potable water and supplies farros and small towns in central San Augustine, southern Nacogdoches, central Houston, south-central Leon, and south-central Robertson counties. The soils derived from the Sparta sand are rather poor for agriculture but produce sorne timber in east Texas and furnish pasturage and oak wood for fuel in central Texas. CROCKETT FORMATION'89 Definition.-The upper marine strata above the Sparta sands were classified as a part of the Cook's Mountain of the Marine beds by Kennedy (905, p. 54, 1892), as a part of the Cook Mountain formation by Deussen ( 415, p. 56, 1914), and lower or marine part of the Yegua by Dumble (506, pp. 102-108, 1918). The locality along Elm Creek in Lee County, selected by Dumble as the type locality for his Yegua, is typical of strata now assigned to the Crockett. Renick (1298, pp. 531-534, 1928) designated the same beds Lufkin member of the Cook Mountain, stating that this term U9L1TERATt:11E-Deussen, A., 415, pp¡ 58-59 (Moseley'• Ferry section) , p. 61 (Alabama Bluff section). 1914; 421, p. 69 (Moseley's Ferry section) , p. 71 (section northeast <>Í Caldwell) , p. 73 (Colorado River section 4% miles east o( Smithville), pp. 75, 76 (Nueces section at Cotulla), 1924. Dumble, E. T., 506, pp. 67, 79'4!6, 91-97, ~101, 1918. Gardner, J., 569, pp. 245-251, 1927. Stadnichencko, Maria M., 1517, pp. 221-243, 1927. Renick, B. C., 1298, p. 531, 1928; and Stenzel, H. B., 1299, pp. 91-96, 1931. Ellisor, A., 523, p. 1340, 1929. Wendlandt, E. A., and Knebel, G. M., 1728, p. 1360, 1929. Weinzierl, L. L., and Applin, E. R., 1721, pp. 384-410. 1929. Heath. F. E., Waters, J. A., and Ferguson, W. B., 696, p. 46, 1931. had been introduced by Knebel and Miss Ellisor. Wendlandt and Knebel (1728, p. 1360, 1929), however, in their later publication named these strata Crockett member of the Cook Mountain for the town of that name in Houston County. The name was used by Miss Ellisor (523, pp. 1339-1340, 1929) to designate that portion of the Cook Mountain formation that líes between the Sparta sand and the Milams member of the Cook Mountain on the Sabine uplift and between the Sparta sand and the Cockfield formation in the type area for the Crockett in Houston County. Miss Ellisor recognizes a change in the facies and in the faunas of the upper part of the Cook Mountain division in the region of the Sabine uplift and divides the strata on a basis of microfaunas and lithology into three divisions: Crockett at the base, Milams Fig. 44. Cross-section showing stratigraphic relationships of the Claihorne divisions in east Texas and Louisiana (after Ellisor, 523, fig. 2, 1929). and Saline Bayou at the top. She believes the Cockfield overlaps the Milams and Saline Bayou strata west of Angelina County. The relationships, as she has worked them out, are shown in figure 44. The United States Geological Survey has not accepted ali these small divisions of the upper Claibome section but has classified ali the strata above the Weches as Cook Mountain. Renick and Stenzel (1299, p. 91, 1931 )have used Crockett as the upper member of the Cook Mountain in describing the section in Brazos River Valley, and Heath, Waters, and Ferguson (696, p. 46, 1931) have followed the same usage in their discussion of the stratigraphy of the Clay Creek salt dome in Washington County. The name Crockett is now fairly well established by usage. The Geology of Texas-Cenozo¡c Systems 657 The type locality of the Crockett formation comprises the oul­crops in the vicinity of Crolkett, Houston County. There are good exposures of certain strata of the formation along the San Pedro Creek near the road southeast of Augusta in Houston County, at Alabama Bluff on Trinity Rive1, at Shipp's Ford on Colorado River just north of the Bastrop-Fayette county line, and along Pinoak Creek east of Smithville, Bastrop County. Regional geology.-The Crockett formation is made up of soft clays and unconsolidated, fine-grained sar:ds which weather to pro­duce a red soil and a more or less featureless, slightly rolling torography except in areas close to rivers where it may be trenched deeply C'nough to produce good exposures. The formation outcrops south of the east Texas geosyncline and .therefore has a fairly straight and moderately narrow outcrop that extemls from Sabine River opposite Columbus, Louisiana, westward to Cn•ckett in Hcus­ton County, thence southwestward to Stone City .on Brazos River in Brazos County, thence to Colorado River above West Point, crosses San Marcos River west of Gonzales, and reaches the Atascosa River below Coughran. From Atascosa County southward the f. )r­mation has not been mapped. The character of the formatkn changes somewhat so that it is more difficult to distinguish it from the adjacent formations. lt is possible, however, to trace equivalent beds from a locality east of Cotulla in LaSalle County southward to Laredo in Webb County. At Laredo the strike of the beds swings southeastward, so that the outcrop of the upper marine beds border the valley of the Rio Grande as far southeast as Lopeño in Zapata County. The width of the outcrop in northeast Texas i!' about four miles except across the Trinity River valley, where it widens to seven miles or more. The average width is three miles between the Colorado and Atascosa rivers. South of Atascosa County its width has not been determined. The Crockett formation clips southeastward beneath the surface, except in the Nueces River valley, where it has been bent into a southeastward-plunging trough. It has been recognized in sections of deep wells as far south as the northernmost salt domes. In the Clay Creek salt dome, for example, according to Heath, Waters, and Ferguson (696, p. 53, 1931), it was encountered between depths 600 and 1200 feet. The thickness on the outcrop varies from 125 to 450 feet. The measurements of thicknesses in the different districts where infor­mation is available are shown in the following table: LOCALITY COUNTY TH!CKNESS AUTHORITY J. L Bonner No. 1-A, ·Humble Oil & Rfg. Co.......-------------------­Angelina Feet 455 Wendlandt and Knebel Southern Pine No. 1-A, Hwnble Oil & Rfg. Co.__________ __ _ _______ Trinity 400 Alva Ellisor Brazos River Valley ~ -------··--·---,---­Robertson 125 Renick and Stenzel Well sections, Clay Creek salt dome ------------­--­-----­---------Washington 225 J. A. Waters ÁRenick and Stenzel placed in the Sparta formation 25 to 50 fe;et of atrata regarded by some others as lower Crockett. lnc)uding the questionab1e beds, the thickness is ISO to 175 feet. .Stratigraphy.-The Crockett formation lies upon the Sparta sand and is overlain by nonmarine beds of the Yegua formation. The basal contact in most places is sharp and is marked by the contact of laminated, fossiliferous clay interbedded with lentils of beach sand of the Crockett formation with coarser, more massive sands of the Sparta below. The top of the formation is regarded as the contact of the fossiliferous marine strata with the overlying non­marine beds of the Yegua formation, into which it grades somewhat. The Crockett formation contains several limestone lentils. One of these outcrops in the vicinity of Crockett in Houston County. Two have been described by Renick and Stenzel (1299, pp. 91, 92, 1931) in the Brazos River valley. The lower limestone, which occurs about 50 to 80 feet above the base of the fossiliferous beds, is named Moseley limestone. Another, which occurs 65 to 75 feet below the top, is called the Little Brazos limestone lentil. The stratigraphy of the Crockett formation in the different dis­tricts of Texas is best illustrated by the following described sections: The Geology of Texas-Cenozoic Systems 659 Section140 of a portion o/ the Crockett formation at the type locality along the Crockett-Palestine highway from a point 1.8 miles north of Crockett to the courthouse and thence along the Crockett-Midway road to a point 2.6 miles southwest of the courthouse, Houston County. Thiokness Feet 8. Clay, brownish gray, fossiliferous, containing a zone of small, ferruginous concretions ·············································-··········-····-15 7. Sand, brown, medium to fine grained ...... ·-·······-····-·····-····--------··· 2 6. Clay, grayish brown, having sand partings and containing a few ferruginous concretions .......................................................... 14 5. Clay, brown, much weathered ..................................... ·-·········-·····-····· 30 4. Sandstone, ferruginous, containing glauconite ................................ 10 3. Clay, chocolate-brown, calcareous, fossiliferous, carbonaceous, containing streaks of light-gray sand .......... ···························-· 25 2. Sand, ferruginous, cross-bedded, containing lumps of clay........ 5 l. Clay, grayish brown, containing selenite crystals ···-··············--·-··· 30 Total thickness measured..·-····················-··-····-·····················131 Crockett formation 14 1 in Humble Oil & Refining Company's ]. L. Bonner No. 1-A, northwest comer William Elliott Survey, Angelina County. Thickness Feet Shale, grayish brown, contammg fragments of fossils .. ----·········-···--33 Rock, brown, ferruginous, having texture of clay ............... ____________ 1 Shale, gray, sandy, containing streaks of gray sand....... -------··-··-·-62 Clay, brown, cemented with ferruginous cement..______________ .............. 1 Shale, sandy ······-··--·-··-··--············--···--·--·····-·-·--·--·--·--······-------··--····-16 Clay, brown, cemented with ferruginous cement..·--···-·····--··-·---··---1 Shale, sandy, containing streaks of gray sand ___________________________________ 22 Shale, hard -·-·····--··-········-····-······-····--··-·------····-··---····--··-········-··----·-··· 5 Shale, greenish gray, glauconitic, fossiliferous ···-········--··-·-··-·······-· 16 Shale, hard -····-··································-·····-···-··········--·-··········----------------19 Shale, brown, containing a few streaks of sand........ ·-····---·--···-·····-· 18 Rock ················-················-·······-········-····-··························-······-·······--····· 13 Shale, hard ······--······--·-·····-··········-······-··········-·······-··-···-·-··-··---···········-·-· 13 Shale, greenish gray, glaucohitic and fossiliferous ...-.. ·-·················-··· 2 Shale, dark, slightly greenish gray, sandy .. ·-·············-···--···-···--····--···· 11 Shale, hard ····--------------·-····-·····--·--------········-··········-············-·······-······· 16 Shale, gray, stickY-------····-····-·-··-····-····-·-···-··-···-···-· ··-··-··-------------··· 37 Rock --------------·----···················-··--···-····-·---··-··-··-···-······-····-·····-···-·-··-· 1 " ºMeasured by Alva Ellisor, 523, pp. 1340-1341, 1929. HlDescribcd by Wendlandt, E. A., and Knebel, G. M., 1728, p. 1357, 1929. Thickness Feet Sh ale, gray, stickY-------------------------------------------------------------------------------------54 Shale, gray, sticky, containing fossils________________________________________________ 47 Sha le, gray brown, sticky, containing streaks of glauconite and fossils and one layer of rock 4 inches thick__ _________________________________ 47 Shale, sandy, containing streaks of sand______________________________ ______________ 21 Total thickness of section__________________________________________________-456 Sedimentology.-The sediments of the Crockett formation show much variation both in kinds of sediments and types of life which they contain. In the early part of the epoch, waters were shallow, and the fossils and aspect of the sediments indicate a shifting shore line in which continental, beach, and littoral conditions alternated. Toward the middle of the epoch, waters were deeper, more glau­conite was formed, thin layers of calcium carbonate mixed with sand and silt accrued, and conditions were favorable for a varied animal life. Later waters shallowed, and zones containing crabs, clams, and other forms that enjoyed a littoral environment replaced the gastropod faunas. At the end of the epoch the sediments show a gradual transition from marine to palustrine and continental de­posits. In the Sabine uplift area and in the Nueces valley embay­ment in south Texas, the clear-water facies of the middle Crockett appears to be absent, and the fauna so well known from Alabama Bluff and Moseley's Ferry is absent. Shallow, muddy waters were the rule, although at certain intervals brackish water and even land conditions may have interrupted marine sedimentation. Lithology.-The Crockett formation in eas.t Texas consists of about 90 per cent fine sediments, clay, shale, and sandy shale, 9 per cent medium-grained sediments, sand and glauconite, and 1 per cent rock, limestone, and ferruginous concretions. In south Texas it contains a larger proportion of sands and sandy clays. The glau­conite is distributed uniformly through the sands and sandy clays and does not occur in thick, pure beds as in the Weches. Sorne of the glauconite grains may have been transported from older forma­tions and redeposited in the Crockett. The clays are bluish gray and black, weathering to buff and yellow colors. They are col­loidal, and sorne layers are distinctly calcareous, whereas others do not react to acid. Most of the concretions are ferruginous. One inter­esting type, described by Burt (185d, pp. 33-45, 1932), is rich in The Geology of Texas-Cenozoic Systems 661 alumina, contains fossils, and appears to have formed around the fossils as nuclei. The concretions are dark gray, spherical to spheroidal, average 55 mm. in diameter, and have a core varying from dark reddish brown to bluish black. The core is in direct contact with, or has replaced, the shell and body of an enclosed fossil crab. They have the following mineral (Burt, 185d, p. 40, 1932) and chemical (Zeller, 185d, p. 40, 1932) percentage com­position : Si02 Ca O MgO Fe20 3 Cu O MnO A120 3 H202 P20s Core 4,_94 12.80 5.15 2.49 0.20 0.065 57.50 3.21 5.32 Case 36.6 13.07 1.37 7.23· 0.00 0.000 . 23.30 5.56 5.79 Alumina ---------------------------------------------------------------------------------------58.1 Calcite and dolomite_______________________________________________________________________ 15.3 Collophanite -------------------------------------------------------------------------------------12.2 Quartz ------------------------------------------------------------------------------------------5.2 lron oxide minerals________________________________________________________________ __ ________ 2.5 Aluminum hydroxide minerals_________________________________________________________ 2.3 Magnesium su!phate ------------------------------------------------------------------------1. 9 Glauconite, etc. ------------------------------------------------------------------------2.5 These concretions occur in middle strata of the Crockett along Little Brazos River in Brazos County. Similar concretions, but not containing crabs, have been found in the Crockett on the bluffs of Sabine River west of Columbus, Louisiana. Distinguishing characteristics.-The Crockett formation is dis­tinguished from other Claiborne formations by the following criteria: i. Predominence of clay. The Crockett strata in east Texas and especially where penetrated by wells south of the outcrop are characterized by much clay. Sand in the section occurs only in thin layers and mixed with clay. Thick lentils of sand are rare. 2. Glauconite. The beds of glauconite are thinner than the beds of the Weches, and the glauconite contains more sand, silt and other impurities. Much of the glauconite in the Crockett Idrntific:2Conrad, T. A., Observation9 on the Eocene deposita of Jackson, Mississippi, with descriptions of four new species of shells and corab: Acad. Nat. Sci. Philadelphia Proc., vol. 7, p. 257, 1856. upon the Yegua and is overlain unconformably by the Catahoula and Frio formations. It consists of shallow-water, marine, and beach deposits, composed of medium-and fine-grained, thin-bedded sand, argillaceous and tuffaceous clays and tuffs, and lentils of coarse, rounded, and polished sand grains. In many places the beds are somewhat fossiliferous. They represent the lower, or Eocene, portion of the pyroclastic epoch, during which violently active volcanoes began to play an important part in supplying material to the sediments. SUBDIVISIONS The Jackson group of strata has not been subdivided into forma­tional units in Texas. All the strata are referred by the United States Geological Survey to one formation, which they (396c, 1932) have designated Fayette formation. Sorne geologists158 regard the Frio formation as upper Eocene or Oligocene; if it is Eocene, it belongs to the Jackson group. The correlation of subsurface data seems to indicate, however, that the outcropping Frio grades down dip above strata that carry a microscopic fauna related to marine lower Oligocene faunas of the Gulf Coast region. The Frio formation has therefore been removed from the Jackson group in recent publi­cations154 ano is classified with Oligocene formations. The Jackson group in Alabama and Mississippi is divided by Cooke155 into the J ackson formation proper and the Ocala limestone. The Ocala limestone does not occur in Texas. FAYETIE FORMATIONUO Definition.-The upper Eocene, Miocene, and Pliocene strata from the top of what is now known as the Crockett formation to the top of the Lagarto clays were grouped together by Penrose 153Deussen, A., 421, p. 92, 1924. Dumble, E. T., 510, p. 435, 1924. Trowbridge, A. C., 1610, pp. 97, 98, 1923. Bailey, T. L., 40, pp. 50, 51, 1926. lMGeologists of the Humble Oil and Refining Company, The geology of the Gul! Coast area of Texas and Louisiana: Natl. Oil Scouts Assoc. Yearbook, p. 54, 1931. lMCooke, Wythe, The Cenozoic formations: Geol. Survey Alabama Special Rpt. 14, p. 274, 1926. l'"I.tTERATURE-Penrose, R. A. F., 1189, pp. 47-58, 1890. Dumble, E. T., 470, pp. 15-l-157, 1892¡ 494, pp. 913-987, 1903; 506, pp. 134-144, 1918; 510, pp. 426-427, 431-435, 1924. Kennedy, Wm., 905, pp. 60-62, 113-116, 1892; 906, pp. 45-46, 1893; 911, pp. 95-99, 1896. Hayes, C. W., and 1'ennedy, Wm., 692, pp. 21-23, 32-ól, 1903. Deussen, A., 415, pp. 68-72, 1914; 421, pp. SG-91, 1924. Cooke, C. W ., Correlation of the deposita of Jackson and Vickahurg agea in Mississippi and Alabama: Washington Acad. Sci. Jour., vol. 8, pp. 186-198, 1918. Trowbridge, The Geology of Texas-Cenozoic Systems 679 (1189, p. 47, 1890) under the name Fayette. Dumble (470, pp. 148-157, 1892) split this original group of Penrose into two divisions, Yegua at the base and Fayette (restricted) at the top. Later Dumble ( 478, pp. 556-559, 1894) revised the classification in south Texas and added two more divisions, the Frio and Oakville. Since the publication of these early reports by Penrose and Dumble the name Fayette has been used variously by geologists. Kennedy (905, pp. 60--62, 1892) included the Catahoula sandstone in his Fayette sands, making the division include strata from the Lufkin formation (now Yegua) up to the Fleming. Veatch (1691, p. 43, 1906) and Deussen (415, p. 68, 1914) included the Fayette in their Catahoula formation. Udden, Baker, and Bi.ise (1652, p. 86, 1916) included in the Fayette from 400 to 600 feet of strata between the Y egua and Frío southwest of Brazos River and from 400 to 500 feet of beds between the Yegua and Catahoula sand northeast of the Brazos. Dumble (506, p. 134, 1918) still further restricted his definition of the Fayette to include certain strata in east Texas between his Y egua and fossiliferous beds that he found to be of Eocene age. He apparently intended to restrict the name to a sfogle bed of fossiliferous sand below the base of the Jackson in east Texas and below the Frío in south Texas. On his map of a portion of east Texas (506, pL 1, 1918) he shows the Fayette only in patches, possibly outliers, upon the Yegua outcrop, and he designated (506, p. 134, 1918) as the type locality for his restricted Fayette the section of strata on Colorado River east of West Point in the extreme western comer of Fayette County. He states that the first high blu:fl down the river from the railroad bridge two miles north of W est Point, called by Penrose "Chalk Bluff," has "Yegua at its base, but higher up a different formation comes in characterized by light colored sands and joint clays which helong to the Fayette ... Criswell Creek just east of West Point gives excellent exposures of the Yegua-Fayette contact." These localities are within the outcrop of the Yegua, as shown on the new geologic map of Texas (396c, A. C., 1610, p. 97, 1923. Applin, Eather, Ellisor, Alva, and Kniker, Hedwig, 32, pp. 111-122, 1925. Bailey, T. L., 40, pp. 37--44, 1926. Cuahman, J. A., and Applin, Esther, 352, pp. 154--189, 1926. Moree, R. W., 1139, p. 227, 1930. Cushman, J. A., and Elliaor, Alva, 382b, pp. 51-58, 1931; 382h, pp. 40-43, 1932. Ellisor, Alva, Jackson fonnation in Texas : Ms, of paper presentcd at meeting of Society of Economic Paleontologiets and Mineralogista, March 1931. Howe, H. V., and Wallace, W. E., Foraminifera of the ]ackeon Eecene at Danville Landing on the Ouachita: Louiaiana Dept. Conservation Geol. Bull. 2, pp. 1-118, 19S2. Trowbridge, A. C., 1613a, pp. 141­155, 193%. 1932). Dumble (506, p. 134, 1918) placed his Fayette beds in the Claiborne group and believed they were distinct from the Jackson. Dumble's type locality for his restricted Fayette formation was selected unwisely, and his definitions are not clear, so that unfor­tunately interpretations of the name Fayette are varied. Trowbridge, for example, (1610, p. 97, 1923) designated the strata between the Frio and Y egua as F ayette. Deussen ( 421, p. 80, 1924) influenced by the United States Geological Survey followed the same usage in his report on the geology of the Coastal Plain west of the Brazos. Deussen, however, states definitely that the beds are not of "Clai­borne age but of Jackson age," yet he did not regard them as equivalent to the J ackson, beca use he remarks ( 421, p. 80, 1924) that "west of the Brazos the Fayette sandstone lies above the Yegua, hut in eastern Texas and western Louisianllj it Hes above the Jack­son." Dumble (510, p. 431, 1924) finally emended his former definitións and described the Fayette as a series of beds that is exposed in a northward-facing escarpment in Lipan Hills east of Campbellton and extends in a broken line for sorne 20 miles or more northeast and southwest. In this same paper Dumble (510, pp. 433-434, 1924) divided his Fayette into two members, Whitsett beds above and Lipan heds below. He stated that he felt fully war­ranted in referring the upper member to the Jackson but still held that the lower or Lipan member was Claiborne. Miss Ellisor157 uses Jackson as a formation name to designate the strata between the Y egua and Catahoula and divides these beds into three divisions: Caddell, McElroy, and Whitsett. The United States Geologica} Survey (396c, 1932) has assigned the name Fayette to ali the strata between the Yegua and the Catahoula in northeast Texas and between the Y egua and the Frio in south Texas. Trowbridge (1613a, pp. 141-155, 1932) used Fayette again for the strata in south Texas between the Frio and Yegua. Shearer,158 Moody (1125, p. 536, pl. 1, 1931), and Heath, Waters, and Fergu­son ( 696, p. 46, 1931), on the other hand, have preferred to use the older term Jackson as a formation name instead of Fayette. 167[llieor, A1va, Jackson formation in Texas : Paper present_ed at San Antonio meeting of the Society of Economic Paleontologista ·and Mineralogista, March, 1931._ She originally used the word Fayette to designate the upper member, but changed it i~ 1932 to Whitsett. lMSberer, H. K., Geology of Catahoula Parish, Louisiana: Bull. Am. Auoc. Pet. Geol., vol. 14, p. 434, 1930. The Geology of Texas-Cenozoic Systems 681 The diagram, figure 45, summarizes this complicated nomenclature. The name Jackson now seems to be preferable for a group name to designate all the uppermost Eocene strata above the top of the Claiborne. Fayette is employed as a formation name for Texas strata between the Y egua below and the Catahoula or Frio above. The section exposed at Lipan Hills, as described by Dumble in his final description of the Fayette, is now regarded as the type section of the Fayette formation. H1LGl'l'RO l &'ll P r N R0 3 C CUM8LC V'f:ATCH ocu~~t:t1 IO'i>O 104) 2. · ·~ 19 2.4­E . Tc.-.;;a'll ·-,,.__ OUM~LC e A ILE.Y 192."'­1<)'2.í. (~. Te.u.•' C. LLl~OR C. COOK U. ~. G. 5. A'J'" 1•31 193-Z.. 193 2.. .L.­-, --­::: Lip•n ~dd~ll ~ ~ v Y"LCjU ll C!?f.:1d Ya:. '9 U Q ~c~fie\d ~c;ua ~el Gardner, MazzaUna oweni Dall is identical with forros that have been described from the 179Bowling, Leslie. Manuscript read at Houeton meeting of Texas Academy o{ Science, Novem· ber, 1932. The Geology of Texas-Cenozoic Systems 695 Jackson formation at White Bluff on Arkansas River, northwestern comer of Jefferson County, Arkansas. The presence of Mazzalina, V enericardia, and Callocardia give a strong Eocene aspect to the fauna. Miss Gardner correlated the strata near Flatonia, Texas, with those at White Bluff, Arkansas. These fossil lists are all incomplete and tinsatisfactory, partly he· cause the specimens are poor, but mostly hecause the faunas have not been sufficiently studied. lncomplete as the data is, however, the collections from the Fayette of Texas give sorne clue to the correlation of the upper Eocene faunas. The fossils from the Cad­dell member are related to forms from the lower Jackson of Mont­gomery, Louisiana, and from Moody's Branch, Jackson, Mississippi. The fossils from the Whitsett, according to Miss Gardner, are re­lated to those of White Bluff, Arkansas. The foraminifera of the Fayette formation in Texas have been described by Cushman and Applin (352, pp. 1~189, 1926) and by Cushman and Ellisor (382b, pp. 51-58, 1931; 382h, pp. 40-43, 1932), and have heen discussed by Miss Ellisor in a manuscript now ready for publication. The foraminifera of the Jackson at Danville Landing have been studied recently by Howe and Wallace.178 The following list of species of foraminifera in material col­lected from the Caddell member three-quarters of a mile south of Robinson's Ferry on Sabine River has heen furnished by Mrs. Plummer: Spiroplectammina mississippiensis Guttulina spp. (Cushman) Nonion umbilicatulus (Montagu} Textularia dibollensis Cushman and onion advena (Cushman) Applin Nonionella hantkeni var. spissa Textularia dibollensis var. humblei Cushman Cushman and Applin Operculinella sp. Gaudryina sp. Uvigerina alata Cushman and Applin Quinqueloculina spp. . Uvigerina topilensis Cushman Biloculina sp. Uvigerina gardnerae Cushman and Lenticulina articulata var. texana Applin (Cushman and Applin) Virgulina dibollensis Cushman and Lenticulina alato-limbata (Gümbel) Applin Astacolus propinqua (Hantken) Bolivina jacksonensis var. striatella Astacolus fragaria var. texasensis Cushman and Applin (Cushman and Applin) Bolivina jacksonensis Cushman and Nodosaria jacksonensis Cushman Applin and Applin 113 Howe, H. V., and WaBace, W. E., Foraminifera of the Jackson Eocene at Danville Landing on the Ouo.chita: Louisiana Dept. of Consexvation, Geol. Bull. 2, pp. 1-llS, 1932. Bolivina gracilis Cushman and Applin Tubulogenerina? eocenica Cushman and Ellisor Discorbis hemisphaerica Cushman Gyroidina soldanii var. octocamerata Cushman and G. D. Hanna Siphonina jacksonensis Cushman and Applin Siphonina advena var. eocenica Cushman and Applin Cibicides jacksonensis var. texanus (Cushman and Applin) Cibicides jacksonensis var. dibollensis (Cushman and Applin) Cibicides antigua (Cushman and Applin) Cibicides yazooensis Cushman Eponides jacksonensis ( Cushman and Applin) Amphistegina sp. Globigerina inflata d'Orbigny Glohigerina sp. Anomalina affinis (Hantken) The most significant species of foraminifera in the McElroy mem· her is Textularia hockleyensis Cushman and Applin, and these strata are often referred to as the "Textularia hockleyensis zone." The following species have been chosen by Miss Ellisor as diagnos­tic of the McElroy member: Haplophragmoides dibollensis Cushman Ammobaculites hockleyensis C.ushman and Applin Textularia hockleyensis Cushman and Applin Massalina decorata Cushman Massalina humblei Cushman and Ellisor Robulus alato-limbatus (Gümbel) Robulus articulatus (Reuss) var. texanus (Cushman and Applin) Robulus limbosus (Reuss) var. hockleyensis (Cushman and Applin) l\rarginulina jacksonensis ( Cushman and Applin ) Marginulina pediformis Bornemann Guttulina spicaeformis (Roemer ) Pseudopolymorphina dumblei (Cushman ana Applin) Sigmomorphina jacksonensis (Cushman) Nonion chapapotensis Cole Buliminella subfusiformis Cushman Discorbis farishi C.ushman and Ellisor Cibicides yazooensis Cushman The following list of significant Whitsett foraminifera has been furnished by Miss Ellisor: Textularia adalta Cushman Textularia mayeriana d'Orbigny Spiroplectammina carinata (d'Orhigny) Massali na pratti Cushman and Ellisor Trochammina teasi Cushman and Ellisor Robulus limbosus (Reuss) Robulus propinquus (Hantken) Planularia truncana (Gümbel) Nonion hantkeni ( Cushman and Applin) var. fayettei Cushman and Ellisor Nonion laevis (d'Orbigny) var. marginatus Cushman and Ellisor onion scapha (Fichtel and Moll) var. inAatus Cushman and Ellisor Elphidium eocenicum Cushman and Ellisor Elphidium whitsettense (C.ushman and Applin) Plectofrondicularia mexicana (Cushman) Tubulogenerina? eocenica Cushman and Ellisor Eponides pygmaeus (Hantken) Valvulineria texana C.ushman and Ellisor Siphonina carltoni Cushman and Ellisor Globorotalia cocoaensis Cushman Anomalina barrowi Cushman and Ellisor The Geology of Texas-Cenozoic Systems 697 The Fayette formation contains in several places a large number of plant fossils. The best-known localities are: l. Nevil's Prairie, about 6 miles southwest of Lovelady, Houston County. 2. Bluff on Colorado River, one-half mile below Rabb's Creek, Fayette County. 3. Creek on Hamilton League, Fayette County. 4. Railroad cut at Striker, nonhern Polk County, near the Fayette­Catahoula contact. 5. Ash beds 21h miles north of Mirafiores ranch, near Jennings gas field, Zapata County. 6. Ash beds 41h miles north of Mirafiores ranch, Zapata County. The following plants have been identified by Berry from four of the localities listed ahove. The numbers following the plant names refer to these localities: Anemia eocenica Berry (2) Nectandra, n. sp. (1, 5-6) Apocynophyllum, 2 n. spp. (1, 5-6) Oreodaphne obtusifoliwn Berry (5-6) Arundo pseudogoepperti Berry (1, 2) Oreodaphne sp. (1) Bombacites, n. sp. (5-6) Papilionites, 11. sp. (5-6) Cinnamomum sp. (5-6) Persea sp. (1 ) CitrophyHum eocenicum Berry (2) Pisonia, 11. sp. (5-6) Citrophyllum sp. (1) Sabalites vicksburgensis Berry (5-6) Coccolobis claibornensis Berry (2) Sapindus dentoni Lesquereux (5-6) Coccolobis columbianus Berry (2) Sapindus formosus Berry (1) Conocarpus eocenicus Berry (5-6) Sapindus georgian1tS Berry (1) Diospyros, n. sp. (5-6) Sapotacites, n. sp. (5-6) Ficus sp. (1, 2) Sophora claibornensis Berry? (5-6) Inga, n. sp. (5-6) Sophora wilcoxiana Berry (1 ) Lygodium kaulfussi Heer (1) Sterculia sp. (1 ) Mespilodaphne, n. sp. (1, 5-6) Terminalia phaeocarpoides Berry Mimosites georgianus Berry (1 ) (5-6) Momisia americana Berry (1) Ternstoemites, n. sp. (5-6) Myri tica catahoulensis Berry? (5-6) Thrinax eocenica Berry? (2) Economic resources.-The economic resources of the Fayette for­mation consist of soils, lignite, fuller's earth and petroleum de­posits. The soils of the Fayette outcrop in northeast Texas are for the most part sandy loams and sands. In sorne places the outcrop is forested by a rather sparse growth of post oak and hickory. In other places the tree growth is scattering, due perhaps to unequal drainage or to the lenticular character of the deposits from which the soils are derived. About half the land is cultivated. Under favorable conditions cotton, corn, sweet potatoes, and ribhon cane can be raised profitably. Land throughout the unimproved areas can be purchased at prices varying from $5 to $12 per acre.174 The lignites of the Fayette are thin, impure, and of poor quality. A few deposits of sorne economic value occur, and the following have been reported by Deussen (421, p. 85, 1924): LOCALITY COU:'ITY THICKNESS Feet Richard Harvey Survey, W. of Ledbetter.. ....... _ __Washington 91h Near the town of Ledbetter..·-·····················-······---Washington 8 Owl Creek, 2 mi. SW. of Nechanitz ...---·-················-Fayette ? Colorado River, 21h mi. NW. of La Grange .......... _. __Fayette 2-15 W. F. Hamilton League, 3 mi. . of West Point.. ...... Fayette ? The following lignite deposits have heen reported by Dumhle (506, pp. 289-291, 1918): LOCALITY CO "\TY THICKNESS Feet l 1h mi. N. of M.K.&T. R.R. on White Rock Creek. ...Trinity 6-8 Western portion of Jacobs League, JA, mi. N. of Potomac ·········-····-················-·····-···-··········-·····--····-Polk 31h N ear Groveton ···-··-······-······-··-··-··-----··-··-····--Trinity 9 Bed of Angelina River on Aaron Ashley Survey, 15 mi. E. of Zavala ... ·-····-···-----··--····-·--···-···-Angelina 5 Bed of Kelso Creek near middle of S. Y oung Survey on Walker-Grimes county line_ ._____.... Grimes 8 Bank of Tanyard Creek on Boatwright Headright near Piedmont Springs ... ·-·········-····--······-··--·--Grimes 7 Richard Hardy Survey, northeast of Ledbetter.. .... -..Washington 91h None of the localities listed ahove have been developed except the one near Ledhetter in Washington County, where a small mine has operated in the past hut is now abandoned. Deposits of volcanic ash in the forro of fuller's earth1n occur at severa} places along the Fayette outcrop. The principal use of l7'Bcnnett, H. H., and Shaw, C. F., Soil survey of Robertson County, Texas: U. S. Dept. Agric., Bur. Soil1, p . 37, 1909. l'rnL1nRATURE-Panona, C. L., Fuller'a earth: U. S. Bur. Mines Bull. 71, 1913. Dumble, E. T., 506, pp. 3~365, 1918. Ladoo, R. B., Non-metallic mineral•, their occurrence, preparation, and utilization: McCraw-Hill Book Co., New York, pp. 91-97, 1925. Ro•, C. S.1 an'd Shannon, E. V .• Mineral• oí bentonite and related clay1, and their phyaical propertiet: Jour. Amer. Cer. Soc ., vol. 9, pp. 82-83, 1926.) Davit, C. W., and Vacher, H. C., Bentonite, it1 properties, mining, preparation, and utilization: U. S. Bur. Minee, Tech. Paper, 438, 1928. Baker, C. L., Volcanic a1h in Te:ia1: Bur. Econ. Geol. Univ. Texas Min. Res. Circ. No. 2, pp. 1-t., 1932¡; Circ. No. 3, pp. 1-7, 1932. Broughton, M. N .• Texas fuller'1 earth1 : Jour. Sedimeatary Petroloa:y, 't'ol. 2, pp. 125­ 139, 1932. The Geology of Texas-Cenozoic Systems 699 fuller's earth is for filtering and clarifying mineral and vegetable oils. Deposits in the Fayette formation are located as follows: LOCALITY COUNTY TH!CKNESS Feet Sulphur Spring, 5 mi. . of Chester_______________ Tyler 6 Chalk Bluff, northwest part of county________ Polk 8 ear Potomac ---·-·-------------------·-·-------------------Polk 5 ear Groveton ------------------·------------Trinity ? Wm. Fitzgibben urvey, near Piedmont Springs______Grimes 2 2 mi. E. of Union Hill ------------Grimes 4 W. cor. James Tuttle Survey___ _ _ _ ____Grimes 4-5 W. P. Zuber Survey________________________ __Grimes 4-5 W. F. Hamilton Survey, 3 mi. SW. of West Point..-Fayette 10 61h mi. S. of Gonzales_ ______________ _______________________Gonzales 3 Conquiesta Crossing, 4 mi. W. of Falls City________ Karnes 10 Mines from which fuller's earth is being produced at present are as follows: LOCALITY CO NTY COMPANY Near West Point.________Fayette Texas Co. 61h mi. S. of Gonzales______Gonzales Coon Co., Inc. ------------·--------------F'ayette Crown Central Pet. Co. --------------·-----·-···-------Grimes Standard Fullers Earth The fuller's earth is mined by stripping the overburden with a steam shovel. The material is then excavated and dried thoroughly. After grinding to a very fine powder, sorne grades are treated with acid to remove any carbonate content, then washed and placed in filters. A large supply of fuller's earth in Texas is available from both the Fayette and Catahoula formations. The product is used mainly by oil companies in their refineries. A much larger demand for the product could undoubtedly be developed by introducing it on a larger scale into other uses, such as abrasive soaps, polishes, insulating compounds, and as a filler in paints. Oil is produced from sands in the Jackson formation on many of the Gulf Coast salt domes and from about fifteen fields in south Texas. The oil sands are fine graineCI, unconsolidated, from 10 to 100 feet thick, and yield from 5000 to 30,000 barreis per acre in the more productive fields. The locations of the fields yielding oil from the Fayette from south Texas are shown in figure 46. ÜLJGOCENE SYSTEM GUEYDAN GROUP DEFINITION No group name has been published for Oligocene strata between the top of the Fayette formation and the base of the Miocene. Ali the fossiliferous Oligocene strata in Texas are overlapped on the outcrop by nonmarine beds, and the faunas and classification of the subsurface strata have not been comprehensively treated. The marine Oligocene heds in Alabama and Mississippi are included in the Vicksburg group by C. Wythe Cooke.176 The name Vicksburg group was also used by Carroll Cook177 to include all Oligocene strata in Texas. Miss Ellisor178 has identified about eighty typical Vicksburg species of foraminifera from the lower Oligocene subsurface strata of Texas. The Oligocene beds ahove this Vicksburg zone carry faunas of younger age and constitute a major part of the Oligocene section in Texas. The name Vicksburg group is therefore likely to be misleading. Gueydan group is proposed to designate all strata between the Fayette formation of Eocene age and the Oakville formation of Miocene age. This section is thought to be typically Oligocene, except perhaps the Catahoula, the stratigraphic position of which is still somewhat questionable. The name Gueydan was first used by Bailey ( 40, p. 62, 1926) for the clays and tuffaceous strata in southwest Texas now referred to the Catahoula. Gueydan was later dropped in favor of the older name, and it is therefore available and appropriate to apply to all the strata above the Fayette and below the Oakville. The strata of the Gueydan group are largely pyroclastic sediments consisting of light-colored ash, tuff, and tuffaceous clay interbedded with lentils of light-colored quartzitic sand and conglomerate. The group has been mapped from Sabine River to the Rio Grande along a belt of rough, rolling, and dissected topography about twenty miles wide and situated about eighty miles from the coast, as shown on the map, Plate l. 178Cooke, C. Wythc, The Cenozoic formatione: Geol. Survey Alabama, Spec. Rept. 14, p. 279, 1926. l'17Cook, Carron, Areal geology of lhe Catahoula formation in Gonzalcs and Karnes countÍE"S: Univ. Texas Thesis, p. 32, 1932. 178Ellisor, Alva, personal communication, Nove:mber, 1932. The Geology of Texas-Cenozoic Systems 701 SUBDIVISIONS The Gueydan group in east Texas comprises only the Catahoula formation. In southwest Texas th~ thicker section is divided into the Frio formation below and the Catahoula above. In subsurface sections in deep wells along the coast the group is divíded, as follows: 4. Catahoula, lower Miocene or upper Oligocene. 3. Unnamed middle Oligocene strata. 2. Frio, rniddJe or lower Oligocene. l. Vicksburg, lower Oligocene. PLE.ISTOCENE­RECENT PUOC (NE.­ MIOCE.NE. OLIGOC. ENE Fig. 47. Section through the upper Cenozoic formations from Brenham to Galveston showing subsurface stratigraphy (adapted from Natl. Oil Scouts Assoc. Amer. Yearbook for 1931, p .. 40). The subsurface middle Oligocene strata may be the down-dip extension of the lower or middle portion of the Catahoula formation in outcrop. The stratigraphic relationships of these Oligocene divisions are shown in the cross-section, figure 47. SUBSURFACE STRATA OF LOWER OLIGOCENE AGE"" Definition.-Marine strata containing minute fossils that are regarded as similar to those in the lower Oligocene strata of Louisiana and Mississippi have been recognized by many paleon­tologists in a large number of oil-well sections just above the Whitsett division of the Fayette. No such strata have been discovered at the surface in Texas, and it is concluded that these marine Oligocene beds are overlapped by the Frio and Catahoula formations. The strata containing the fossils lie upon the Fayette formation and are overlain by strata correlated with the Frio. The graphic section (fig. 47) shows the relationship. No name has been assigned to these l70L1TERATU1tE-The geology of the Gulf Coast area of Texas and Louisiana: Texas Culf Coast OH Scouts Assoc. Bull. l , p. 42, 1930. Ellisor, Alva, Jacksoo formation in Texas with notes on the Frío: manuscript presented at meeting of Soc. Econ. Pal. Mio., March, 1931. Cook, C. E., Areal geo)ogy of tbe Catahoula formation in Gonzales and Karnes counties: Univ. Texas Thesis. pp. 32-34, 1932. strata in Texas, but Miss Ellisor has referred them tentatively to the Vickshurg group of Mississippi. Regfonal geology.-Strata carrying fossils thought to he of lower Oligocene age have heen reported180 from the following areas: LOCALITY COUNTY THICKNESS Feet Moss Bluff oil fie]d _______________________________________________ Charnbers 500 Raccoon Bend oil field ___ ____ ----··------------___________ Washington 300 Barbers Hill oil field _____________________________________________Charnbers 400 Hurnble oíl field________________ __________________________________________Harris 247 Pierce Junction oil field ·-----------------------------------------Harris ? Hockley oil field__________________________________________________________ Harris 545 Welder No. 1, near Nursery______________________________________Victoria 424 The thickness of this section varies from 200 to 550 feet. Lithology.-The lower Oligocene heds consist of ahout 90 per cent clay and 10 per cent very fine sand or sandy clay. The clay is similar to that of the Frio formation and comprises light-gray, greenish-gray or green, argillaceous, slightly calcareous clays that grade in places into sandy clays. The sands are composed of fine, angular and subangular quartz and chert grains mixed with a little volcanic glass. Sorne of the chert grains are black. Paleontology and correlation.-These lower Oligocene strata in places carry a rich foraminiferal fauna. Miss Ellisor has identified181 from this zone more than sixty forms that occur also in the Byram strata in Mississippi and a large number that occur in the Red Bluff clays of the Oligocene in that same state. A typical list from this zone furnished by Miss EllisÓr is as follows: Textularia rnississippiensis Cushman Siphonina advena Cushman Textularia warreni Cushrnan and Cibicides floridanus (Cushman) Ellisor Eponides byramensis (Cushman) Textularia turnidula Cushman Eponides vicksburgensis Cushman Clavulina byramensis Cushman and Ellisor Robulus rotulatus (Lamarck) Cassidulina crassa d'Orbigny Lenticulina vicksburgensis Globigerina bulloides d'Orbigny (Cushman) Anornalina mississippiensis Cushman Nonionella taturni Howe Sorne geologists182 helieve that these strata represent the deep­water marine facies of the Frio or the lower Frio formation. Others regard these marine strata in well sections as a separate memher lllO'J'eiwi Gulf Cout Oil Scouts A90oc. Bull. l, pp. 42-44, 1930. 181.Ellisor, Aba, personal communication. 1932. lllApplin, E. R., Ellioor, Alva, and Kniker, H. T., 32, p. 107, 1925. The Geology of Texas-Cenozoic Systems 703 that is overlain and overlapped by the Frio clays. The strata are cor­related on the hasis of their foraminiferal content with the Vickshurg stiata of Mississippi. FRIO FORMATIONW Definition.-The name Frio was assigned by Dumhle (478, p. 554, 1894) to dark-colored, greenish-gray clays ahove the Fayette sands in south Texas. He did not define clearly the upper limit of his formation. He states, "The clays are dark colored, greenish gray, red or hlue, usually massive, with quantities of gypsum and with calcareous concretions arranged in lines." He specified that typical strata are exposed along Frio River in Live Oak County. Twenty years later he descrihed again the weathered clays as "a chalky looking mass of dazzling white"' and stated that the formation out­cropped on Atascosa River southwest of Fant City and along the escarpment south of Comanche Creek in Atascosa County. Bailey (40, p. 45, 1926) descrihed and mapped under the name Gueydan a series of sandstones, clays, and ash heds which he found to he approximately equivalent in age to, and continuous with, the Cata­houla sandstone formation in northeast Texas, hut which included also much of the section assigned by Dumhle to the Frio formation. Bailey (40, p. 44, 1926) restricted the name Frio to the strata heneath the volcanic tufls of his Gueydan formation and ahove the Fayette formation. This restricted Frio formation did not include the strata at the type locality of the Frio on Frio River nor the strata southwest of Fant City descrihed by Dumhle. Bailey's proposal, therefore, was regarded as too drastic a restriction to he acceptahle to the United States Geological . Survey according to the rules of nomenclature. Gardner and Trowhridge (572a, p. 470, 1931) found it preferahle to assign a new name, Yeager clay, to the strata between the Gueydan and Jackson and to ahandon the name Frio. Memhers of the San Antonio Geological Society, however, (572a, p. 967, 1931) suggested that the new name Yeager would lead only 181f.nu..T11U-Damble, E. T., 478, pp. 5M-555, 1894; 494, pp. 953-956, 1903; 497, p. 51, 1911; 510, p. 434. 1924. Hayet, C. W., and Kennedy, Wm., 692, pp. 22-23, 3 diecuMion, pp. 967-970, 1931. Ellieor, A. C., Jackson formation in Tesas with nolea on the Frio: MS. of paper preeented at San Antonio meeting: o( Soc. Econ. Pal. and Mio., Narch 1931.. Cook. C. E., Areal 1eoloCJ of tbe Catahoula formation in Gonzales ami Karnea countie• : Univ_ Tena tbeaia, pp. 32--M, 1952. to more confusion and regarded Bailey's restricted use of Frio as preferable. They further objected that the name Yeager was so similar to the name Yegua, that confusion in telegrams and written notes would be a likely consequence. The United States Geological Survey (970d, p. 101, 1932) with sorne hesitancy therefore agreed to the restricted definition of the Frio formation and have assigned the name to the strata included by Bailey in his definition, as shown on their new geologic map of Texas (396c, 1932). Neither Bailey nor the San Antonio Geological Society Committee on geologic mapping has designated a new type locality for the restricted Frio formation. Bailey ( 40, p. 46, 1926) describes 15 feet of creamy-gray to greenish, plastic clay in a cut on the San Antonio, Uvalde and Gulf Railroad one mile northwest of Fant City in Live Oak County. This might be taken as the type locality for the Frio as now recognized. Regional geology.-The outcrop of the Frio formation is a generally featureless plain, known as the Frio plain, covered by mesquite, cactus, and thorny chaparral. lt extends from the southeast comer of Atascosa County southwestward across McMullen County to a point near Aguilares in Webb County, thence southward along the eastern border of Zapata! and western Jim Hogg counties to the Rio Grande at Rio Grande City. The width of the outcrop in Live Oak County is about one mile. It widens in McMullen County .to two to four miles, and in Zapata, Jim Hogg, and Starr counties it is from eight to ten miles wide. The strata dip beneath younger formations and . are penetrated in deep wells throughout southwest Texas as far as the coast. The thickness of the formation in outcrop varies from 150 feet in Live Oak County to 800 feet in Jim Hogg County. Beneath the surface its thickness ranges from 250 to 600 feet in wells. The following table shows thicknesses in various districts: . LOCALITY COUNT'i THICKNESS AUTHORITY Feet Warren No. 7, Humble Oil Co., Hockley salt dom e ---------------Harris 560 Ellisor E. B. Wilson o. 1, Humble Oil Co., Raccoon Bend oil field ___ Washington 260 Ellisor Welder o. 1, Humble O. & R. Co., near Nursery __________ Victoria 424 Ellisor The Geology of Texas-Cenozoic Systems 705 LOCALITY COUNTY THICK 'ESS AUTHORITY Feet U. S. l. Realty Co., Fant City___ Live Oak 390 Deussenl.l Hicks o. 1, well drilled by H. Coquat et al, 1 mi. W. of Simmons -----------------------------Live Oak 270 Bailey Laas No. 1, Lavaca Oil Co., eastern part of countY-----·---Lavaca 322 Bail ey Average thickness of outcrop ____ Webb 300 Trowbridge :i.Rcviscd slightly to agree with the new nomcnclature. Stratigraphy.-The Frio strata lie conformably upon sand and sandy shales of the Fayette formation and are overlain unconform­ably by beds of tuff and volcanic ash of the Catahoula formation. The base is marked by the contact of greenish-gray clays with light­gray, thin-bedded, sandy clays and sand of the Fayette~ The top of the fonnation is established where the greenish-gray clays are in contact with decidedly tuffaceous and ashy beds. In Kames County a !ayer of sand and conglomerate and coarse detritus marks the upper contact. In most places where exposures are good, it is easy to identify the Frio strata by its characteristic greenlsh-gray, mass1ve clay. A typical section is described as follows: Log184 o/ a well drilled by the U. S. l. Realty Company at Fant City, Live Oak County. Thickness Catahoula forma tion-Feet Cl a y, gray, gritty, plas tic_____ -------------------------------------------------------------65 Lime and volcanic ash, pinkish gray _______________________________________ 35 Frio formation-Clay, green --------------------------------------------------------------------------------40 Clay, green, gritty ------------------------------------------------------------------------15 Clay, green, calcareous, sandy ------------------------------------------------------10 Clay, green, gritty, calcareous ----------------------------------------------------195 Clay, green, sandy --------------------------------------------------------------21 Mari, green, containing calcareous nodules ---------------------------------39 Limestone, green, argillaceous, interbedded with green, brittle clay -------------------------------------------------------'-----------------------------44 Limestone, green, sandy, argillaceous _______________•___________________________ 26 Total thickness of Frio formation ________________________________ 390 Sedimentology.-The Frio deposits appear to representa continua­tion of Fayette conditions of sedimentation. The much larger por­ lS&Described by A. Deuasen, 421, p. 93~ 1924 (formational interpretation reviaed). tion of clays suggest that the adjoining land areas were low and more nearly at base level. There may have been also less rainfall and less river water to transport coarse sediments. The absence of fossils and lack of even stratification in the clays suggests that sorne of the material may have been of fresh-water origin. The absence of carbonaceous matter and the presence of much gypsum also suggest nonmarine deposition. Lithology.-The Frio formation is composed of over 95 per cent clay, about 4 per cent sand and sandy silt, and 1 per cent concretions. The clay is nearly everywhere creamy-green or buff green. The silt is gray, extremely fine grained, noncalcareous, and very gyp­siferous. The sand grains are subangular to angular and range from one-sixth to one-quarter of a millimeter in diameter. The following composition of a typical washed sample from an outcrop one mile south of Whitsett, Live Oak County is given by Bailey (40, p. 47, 1926) : Light minerals-Per cent Gypsum -----------------------------------------------------------------------------------------------------90 Plagioclase feldspar --------------------------------------------------------------------------------3 Orthoclase feldspar --------------------------------------------------------------------------------1 Quartz -----------------------------------------------------------------------------------------------------5 Chert --------------------------------------------------------------------------------------------------------1 Calcite --------------------------------------------------------------------------------'----------------Trace Heavy minerals-Microcline --------------------------------------------------------------------------------------------Rare Barite ---------------------------------------------------------------------------------------------------Trace Magnetite ---------------------------------------------------------------------------------------------Trace Green hornblende -------------------------------------------------------------------------------Trace Titanite ----------------------------------------------------------------------------------------------------Rare Paleontology and correlation.-The age and correlation of the Frio formation are uncertain. The strata are younger than the Fayette which is definitely Eocene, and older than the subsurface strata, now thought to be middle Oligocene. Dumble (494, p. 953, 1903) believed that the Frio fossils indicated Eocene age. Deussen ( 421, p. 92, 1924; p. 97, 1930 ed.) on the authority of the paleontologists of the United States Geological Survey stated that the fauna "may indicate '\ .. either late Eocene or early Oligocene age . . . but until further evidence is available the formation is classified as of late Eocene (Jackson) age." Bailey (40, p. 51, 1926) noted that beds contain Ostrea georgiana Conrad and are The Geology of Texas-Cenozoic Systems 707 therefore "more probably of Eocene age." Miss Ellisor, as quoted by E. H. Finch (572aJ p. 970, 1931), believes that "the Frio clays contain a few lower Oligocene or Vicksburg foraminifera." Miss Kniker185 believes that possibly the Frio clay is a southern facies of the lower Catahoula sand of central and northeast Texas and is therefore the same age as the Catahoula. Recent detailed subsurface correlátion of strata in oil wells by geologists of the Humble Oil and Refining Company and the United Gas Company indicates that the Frio formation líes beneath strata assigned to middle Oligocene age and above strata assigned to the Vicksburg (fig. 47). SUBSURFACE STRATA OF MIDDLE OLIGOCENE AGE,.. Definition.-The subsurface deposits, commonly referred to by Texas geologists as Oligocene or middle Oligocene, consist of dark, olive-green and gray, faintly calcareous, fossiliferous clays, fine, olive-gray sands that carry oil on many domes, and thick lentils of limestone in the form of coral and foraminiferal reefs. The total thickness of these strata varies from 400 to 1100 feet, as shown by the following table: LOCALITY COUNTY TH!CKNESS AUTHOR!TY Feet Hull oil fi eld ______________________ ___________ Liberty 550 Applin, Ellisor, and Kniker Batson oil field_________________________ Hardin 600 Do Pierce Junction oil fielcL_ _________ Harris 4.50 Do Goose Creek oil field._____ _ ______ Harris 600-1150 Do West Columbia oil field______ ____ Brazoria 425 Do Damon Mound oil field _________ Brazoria 313 Do Miller-Vidor No. 1, Gulf Prod. Co., E. Lewis Survey.________ Orange 356 M. A. Hanna Keeran o. 1, Bunte et al, M. de Leon Survey_____________________ Victoria 601 M. A. Hanna Stratigraphy.-The details of the stratigraphy of the Oligocene beds are shown in the following described sections: 185.Personal communic.:ition. l80L1TERATURE-Applin, . E. R., Ellisor. A. C., and Kniker, H. T., 32. pp. 102-111, 1925. El1isor, A. C., 522, pp. 976-985, 1926. Anonymous, The gcology of the Culf Coast arca of Texas and Louisiana: 18 33d. pp. 41. 42, 1931. EJJisor, A. C.. The stratigraphy of thc Jackson of 1'exas with notes on the Frio: MS. 1931. Section187 o/ strata penetrated by Lovejoy No. 1, Humble Oil and Refining Company, W est Columbia oil field, Brazoria County. Thickness Feet 3. Clay, light gray, and light greenish-gray, shaly, containing very fine, angular sand grains and small lime nodules ........... 100 2. Limestone, gray, chalky in places and varying from crypto­crystalline to porous, coarsely crystalline texture, containing lentils of green clay. Portions of the limestone are made up almost wholly of Het erostegina cf. antillea Cushman and Amphistegina lessonii d'Orbigny, bryozoa, corals, and ostra­cods. Other parts are devoid of fossil remains... _ ............... 225 l. Clay, light greenish gray and bluish gray, calcareous, sandy, and shaly, containing foraminifera... _ .. _ .........·-··············-··--····-··100 Total thickness......·-··-····-···-··-··-···-·······-··-··-··--·-·-··--·-·-·-·-··-425 Details of the strata represented by the second division of the above section are shown in the following descriptions of beds penetrated by another well in the same field. Section188 penetrated by Gallagher No. 2, Humble Oil and Refining Company, W est Columbia, Brazoria County. Depth Feet Limestone, blue, cryptocrystalline, fossiliferous, made up of masses of H eterostegina, Lithothamnium, and sorne Porites, and containing veins of coarsely crystalline calcite............ 2977 Limestone, made up of great quantities of foraminifera and a few quartz sand grains cemented by chalky calcite into a firm mass, containing Heterostegina cf. antillea Cushman and Aniphistegina lessonii d'Orbigny, Gypsina sp., Pecten sp., and ostracods ... _ .....______........... _ ........ -.. ···········--·--······--····-·2994-2996 Limestone, blue, cryptocrystalline, containing veins of calcite and man y foraminifera, among which H eterostegina cf. antillea Cushman Amphistegina lessonii d'Orbigny, and Gypsina sp. can be recognized ········--·········-·····-·-··········-···-·--3000c-3008 Limestone, light gray, cryptocrystalline, made up almost en­tirely of the coral Porites with a few foraminifera and ostracods between the coral branches....... ---···-········-·-·····-···-· 30·43 Limestone, white, chalky, made up largely of the coral Porites and containing veins of crystalline calcite..... -.......3059-3078 Lithology.-The middle Oligocene beds consist of shaly clays, sandy clays, fine sands, and lentils of coral and foraminiferal lime­ lB7Descrihed by Applin, Ellisor, and Kniker, 32, y. 109, 1925. 188Modi6ed slightly from a description of the cores by Mhs Ellisor, 522, p. 978, 1926. The Geology of Texas-Cenozoic Systems 709 stone. The clays are greenish gray, calcareous in sorne places, non­calcareous in others, sandy in sorne layers, and generally fossilifer­ous. The sands are composed of very fine and angular to medium­sized and subangular quartz grains. Glauconite occurs in sorne zones. The limestone lentils in the Oligocene section are especially note­worthy. They consist of massive, crystalline limestone from one to severa! hundred feet thick, and their fossil content shows that they were originally coral reefs. These reefs occur only on salt domes where water was shallow enough for the reef-forming animals to live. According to Miss Ellisor (522, pp. 976---977, 1926), the upper part of the reef is composed almost wholly of Heterostegina antillea Cushman; the lower portion is massive, cryptocrystalline coral limestone built up of the massive species Porites. Distinguishing characteristcs.-The Oligocene strata in well sec­tions are distinguished mainly by their foraminiferal content and by the massive limestone lentils containing corals. Paleontology and correlation.-The subsurface Oligocene strata have been divided by Applin, Ellisor, and Kniker (32, p. 102, 1925) in to three Jossil zones: Discorbis zone at the top, H eterostegina zone m the middle, and Marginulina zone at the base. 3. Discorbis zone. This series of strata is characterized by the foraminifer Discorbis cf. D. vilardeboana d'Orbigny. The strata consist of bluish-gray, calcareous, shaly clay, dark-gray, calcareous, sandy clay, and lentils of fine-grained sand. The thickness averages about 100 feet. 2. H eterostegina zone. This zone consists of reefs or lentils of limestone containing Heterostegina cf. antillea Cushman. The reefs are confined to areas around salt domes where the Oligo­cene sea was shallow. The rock consists of gray limestone composed of fine, angular grains cemented into a solid mass containing nodules and streaks of white, chalky limestone. Gray, calcareous and noncalcareous clays are interbedded in places with the limestones. The thickness of this rock varies from 100 to 225 feet. It has been encountered on the follow­ing salt domes: Damon l\found, West Columbia, Nash, Bowling, Barbers Hill, Pierce Junction, Batson, Hull, Humble, Strat­ton Ridge, Sour Lake, and others. l. Marginulina zone. This zone is characterized by the foraminifer Marginulina cf. M. philippinensis Cushman. The strata con­sist of bluish-gray, calcareous clay containing layers of cal­careous and noncalcareous fine-grained sandstone and a little glauconite. The thickness of this series of strata varies from 100 to 350 feet. The fauna is regarded by Miss Ellisor (522, p. 977, 1926) as middle Oligocene in age and correlative with the Antigua forma­tion of the West ludies. Carefully constructed cross-sections indicate that these middle Oligocene strata coalesce up dip with upper Catahoula strata. CATAHOULA FORMATION189 Definition.-The formation now named Catahoula was first desig­nated Grand Gulf sandstone for Grand Gulf on Mississippi River in Claiborne County, Mississippi, by Wailes190 in 1857. In 1860 Hilgard191 used the name Grand Gulf group for ali the beds in Mississippi between the Vicksburg and recent coastal clays. Hil­gard192 in 1869 also recognized the same strata in Louisiana and traced them across the state to the Texas line. Two years later108 he presented a map showing their extent across southeast and south Texas. The Grand Gulf mapped by Hilgard included the present Yegua, Fayette, Frio, Catahoula, Oakville, and Lagarto formations. Loughridge (1017, pp. 47-58, 1884) published the first descriptions of the Grand Gulf strata in Texas. After the publications 'of Hilgard and Loughridge, however, the name Grand Gulf was used with so JBOLmall, W. H., The Grand Gulf formation: Science, new ser., vol. 16, pp. 946-947, 1902; Science, Tol. 18, pp. ~. 1903. UOJlilprd. E. W., Sciencc, new ser., vol. 18, pp. 180--182, 1903. Udden, Baker, and Bose (1652, p. 88, 1916) also used Corrigan in the same way. Matson ( 1061a, pp. 209-210, 1916), working in Mis­sissippi and Louisiana, used the name Catahoula but restricted it to include only nonmarine deposits equivalent to those found at the type locality at Grand Gulf, limiting the formation to the strata above the marine Vicksburg in Mississippi and below the Hattiesburg clay or its equivalent. His Catahoula was a synonym for Dumble's Corri· gan. Deussen ( 421, p. 95 and map, pl. l, 1924) mapped the Catahoula to a point about 5 miles southwest of La Grange in Fayette County, and separated it from the Fayette below and Oakville above following Matson's definition. The strata below the Oakville and above the Fayette south of La Grange he mapped as Frio. Bailey ( 40, pp. 1-179, 1926), mapped and studied in detail the strata between the Fayette and Oakville formations in south Texas. He divided the strata in this section in to two formations: (1) volcanic tufls, con­glomerates, and noncalcareous ash beds above, which he named Gueydan; and (2) yellowish-green, calcareous clays below, to which he applied Dumble's name Frio in a restricted sense. He regarded the Gueydan formation to be equivalent, in part at least," to the Catahoula. Cook197 traced the Catahoula formation south­westward from La Grange in Fayette County to Frio River in Live Oak County and established the equivalency of the Catahoula sand­stone to the lower part of the clays which Dumble had designated the type locality of his Frio (now lower part o~ Bailey's Gueydan formation). Three synonymous names are therefore now in use to designate the strata between the Fayette and Oakville in south Texas and between the Fayette and Lagarto in east Texas: Corrigan and Catahoula in east Texas, and Gueydan in south Texas. The name Corrigan was given in 1892, Catahoula in 1906, and Gueydan in 1926. Corrigan should have precedence over the others, but the Corrigan formation was not clearly defined by Kennedy. In fact, the present meaning of the name was not defined until Dumble's work on east Texas was published in 1915 and 1918. On the other hand, Catahoula was described by Deussen, Matson, Berry, Trow­bridge, and Goldman in publications that are read widely so that the latter name carne into common usage. The term Gueydan was given te> the volcanic tuffs and ash beds by Bailey because he was l97Cook, C. E., Areal geo1ogy of the Catahoula íormation in G:onzales and Karnea counties: Univ. Texas thesis, p. 10, 1932. The Geology of Texas-Cenozoic Systems 713 not certain of the correlation of the formation with the Catahoula and thought the difference in facies of the strata in the south from those in the northeast was sufficient to warrant another name. The United States Geological Survey on the new geologic map of Texas (396c, 1932) has decided to name the sandstone strata in east Texas Catahoula sandstone and the ash beds in south Texas Catahoula tuffs. Bailey (40a, p. 259, 1932) has agreed to the substitution of Catahoula tuff for Gueydan formation and the name is likely to stand. No type locality for the Catahoula was established by Veatch. The formation was named for Catahoula Parish, Louisiana, where according to Sherer198 the sandstone strata cover the northwestern part of the parish. Matson regarded the type locality as the outcrop at Grand Gulf, Mississippi, where the Grand Gulf was originally described by Wailes. Excellent exposures of the sandstone in Texas occur along the lnternational and Great Northern Railroad just south of Riverside in W alker County. The type locality of the Catahoula tuff facies (Bailey's Gueydan formation) is on the Gueydan ranch in the Gueydan Survey in southeast McMullen County where the upper part of the formation is well exposed. Regional, geology:-The Catah"oula outcrop may be conveniently divided into two areas for purposes of description, the east Texas outcrop and the southwest Texas outcrop. The east Texas outcrop comprises the Catahoula sandstone and interbedded ash beds and consists of a belt of rugged, rocky, tree­covered territory extending from Sabine River at the northeast comer of Newton County westward across northern Tyler, northern Polk, northern San Jacinto, central Walker, central Grimes, northern Washington, central Fayette, and southern Gonzales counties to Guadalupe River. The south Texas outcrop comprises the Catahoula tuff and occupies a belt of rolling, moderately dissected, more or Iess improved and cultivated farm land in south-central Texas and pasture land in south Texas which extends from southern Gonzales County, through northern Karnes, northern Live Oak, and northwestern Duval counties to eastern Webb County, then bends southward across 198Sberer, H. K., Geology of Catahoula Parish, Louisiana : Am. Assoc. Pet. Gcol. Bull, vol. 14, p . '37, 1930. eastern Wehh County and disappears heneath younger formations in Zapata County (fig. 49). The width of the outcrop of the Catahoula sandstone in east Texas varies from four to six miles. lt narrows in central Texas to one mile or less. The outcrop of the Catahoula tuff in central Texas is from one to two miles, hut it widens in south Texas to eight and ten miles in McMullen and Duval counties. The Catahoula formation extends heneath the surface as far as the coast and is an important oil-producing horizon on salt domes and in sorne of the south Texas fields. The Catahoula formation varies in thickness from 300 to 600 feet in east Texas to 150 to 200 feet in central Texas and thickens to 800 to 1000 feet in south Texas. lts thickness in various sections is shown in the following table: LOCALITY COUNTY THICKNESS AUTHORITY Feet Outcrop, 4 mi. E. of Flatonia_ Fayette 120 L. Bowling Sandies Creek valley.._._______________ _ Gonzales 200 C. E. Cook Brazos River valley_________________ _ Washington 200 A. Deussen Guadalupe River valley_____________ Gonzales 190 T. L. Bailey Generalized section ------------------ Karnes 350 Do Generalized section -----------------·---­Live Oak 600 Do Generalized section --------------------- McMullen 650 Do Generalized section -----------··--------Duval 850 Do Hicks No. 1, H. Coquat and As­ sociates (section incomplete) __ Live Oak 350+ Do Santo Domingo No. 1, Alcorn Oil Company --------------------­ Starr 629 Do Peters well, 9 miles NW. of Moglia ------------------­Webb 87{}-790 Do Matson, (1061a, p. 220, 1916) determined the thickness of the Catahoula in a well at Monticello, Mississippi, to he 420 feet, and Sherer1 99 found it to he 844200 feet thick in The Texas Company well near Jonesville, Catahoula Parish, Louisiana. Stratigraphy.-The Catahoula formation overlies the Fayette and Frío formations unconformahly and is overlain unconformahly by the Oakville and Lagarto formations. In east Texas the basal con· tact is marked by the plane between coarse-grained sand and l.19Sherer, H. K., Geology oí Catahoula Parish, Loui1iana: Bull. Am. Auoc. Pet. Geol., vol. 4,, p. '"9· 1930. IOOfocJudee a liule recent surface sand. The Geology of Texas-Cenozoic Systems 715 conglomerate in places cemented to form a quartzitic ledge and the light-colored tuffaceous and highly siliceous clays and thin-bedded, light-colored sandstones of the underlying Jackson. In south Texas the tuff beds of the Catahoula rest upon green and greenish-gray nontuffaceous clays of the Frio. According to Cook201 the basal Catahoula tuffs in northern Live Oak County are so heavily impreg­nated with silica that they stand out above the underlying soft, unindurated Frio clay as a conspicuous cuesta known as "chalk bluffs" which can be followed and mapped readily. The upper contact of the Catahoula is distinguished easily in most places. In east Texas where the Catahoula is in contact with Lagarto clay the clay can be distinguished by its darker color, higher calcareous content and larger amount of colloids. The Catahoula beds below are light colored, tuffaceous, gritty, noncalcareous, and less colloidal. In central Texas where the Oakville sandstone rests upon the Catahoula, the contact is marked by a cuesta of brownish-gray, calcareous Oak­ville sandstone rising above white and buff tuffaceous clays of the upper Catahoula. The basal beds of the Oakville vary in lithology along the contact and in those places where typical Oakville sand­stone is absent the Oakville clays can be distinguished by their darker color, greater calcium carbonate content, and smaller amount of volcanic material. The clays of the Oakville resemble more closely the Lagarto than the Catahoula. The Catahoula formation in east Texas has been divided into two subdivisions or members on a basis of lithology, as follows: 2. Onalaska.-Dumble gave the name Onalaska to the strata above his basal sandstone member (now called Chita) and below the base of the F1eming ( now called Lagarto and Oakville). The beds consist of tuffaceous shales, sandy clays, and cross-bedded, len­ticular sandstones in places cemented by opal. The type lo­cality comprises the exposures in Rocky Creek east of Onalaska, Polk County. There are good exposures also in Kickapoo Creek in Polk County and in Harmon Creek north of Huntsville. l. Chita.-The new name Chita member is introduced to include the coarsely textured, and in places conglomeratic, basal sands of the Catahoula exposed at Chita and Corrigan in east Texas. Kennedy gave the name Corrigan to this sand, and Durable (506, p. 188, 1918) referred to it as Catahoula member of the Corrigan formation. Since Durable, Udden, Baker, and others I01Cook, C. E., Areal geology of the Catahoula formation in Conzales and Karnes counties: Univ. Texas theeia, p. 44, 1932. have used Corrigan for the whole Catahoula formation, it is confusing to use the name again in its original restricted sense, and it seems best to drop the name. The Chita sand is 10 to 80 feet thick, has white, polished grains called "rice sands," and is in places solidly cemented to a hard quartzite with sileceous cement. In most places the !ayer forms a persistent cuesta. The type locality comprises the exposures along the north-facing es­c~rpment near the town of Chita in Trinity County. The strata in south Texas have been divided on lithology into three members: 3. Chusa.-The Chusa member is named for La Omsa mesa in south­eastern McMullen County, where a good section is exposed be­neath the Oakville sandstone capping the mesa. The series of strata consists of unindurated, tuffaceous clays and unstratified tuffs, and it resembles in every way the fine-grained materials interstratified with and separating the conglomerate beds of the Soledad member. The tuff is described by Bailey ( 40, p. 91, 1926) as "an unstratified, noncalcareous to marly, very poorly consolidated, pisolitic or lumpy bentonitic clay ... which com­monly outcrops in vertical facies like loess. The clay ... shows a prominent pisolitic or pseudo-pisolitic structur_e." The clay in sorne. places contains spheroidal or lobate clay concretions from one-fourth of an inch to six inches in diameter. The thickness is estimated to be from 160 to 200 feet. 2. Soledad.-The Soledad conglomerate lentil is named for the Sole­dad hills in western Duval County, where a typical section is ex­posed. It includes conglomerate lentils in the Catahoula in south Texas between the top of the Fant memb1'r and the base of the Chusa. This series of strata comprises volcanic conglomerate, &andstone, and tuff. The well-rounded pebbles of the conglom­erate consist of reddish-and grayish-brown trachyandesite, trachyte, cobbles, chert, pumice, and tuff, and they range from a fraction of an inch to a foot or more in diameter, and these are cemented by milky-white, translucent opal. lnterbedded with the conglomerate layers are lenses and beds of impure tuff. In places the conglomerates are thin and are separated by thicker beds of tuff, clay, and sandstone. The sandstone is brownish­gray and greenish-gray, tuffaceous, more or less indurated, and of uneven texture, ranging from very fine grains to coarse peb­bles. The conglomerate layers occur at several horizons in the Soledad member and form a series of ridges especially notice­able in McMullen County. l. Fant.-The Fant member is named for the town of Fant City in northern Live Oak County. This division includes ali the strata in south Texas from the top of the Frio formation to the base The Geology of Texas-Cenozoic Systems 717 of the Soledad rnernber. The series of strata consist of volcanic ash and tuff interbedded with sorne clay. The tuff is character· istically white, fairly well indurated, rnassively bedded, sorne· what vesicular and fine textured, and classified by Bailey as a trachyte.2º2 The beds are cut by joint cracks and break down readily into srnall angular fragrnents. The white tuffs are inter· bedded in places with light·gray and yellowish.gray, very friable, soft tuff resernbling the sand and less cornmonly with grayish· brown, rnottled, bentonitic clay. The total thickness of the Fant rnember is about 200 feet. Ali three members are present in south Texas. The Fant member extends as far south as Gonzales and Lavacá counties, where it is interbedded with a number of siliceous sandstone beds and takes on a sandy facies. The exact relationships of the beds in east Texas with those in south Texas have not been satisfactorily determined. It is thought, however, that the strata in east Texas consist of the lower La9 a r+o -..:-:-: -::_ ~~~ ~:~=~:~'~ .~~ri. d ... ""l'"arir a~h end cl•y rr •o c. ay rro,,;/J -\.._ Onala.ska -tuft + F'o!Jsl/.s f".¡y~tte Fig. 48. Diagrarnrnatic sketch showing the stratigraphic relationships of the rnernbers of the Catahoula forrnation and the overlying Oakville sand. The fossils indicated near the top of the Fayette forrnation are those found at and near Flatonia, Fayette County, and near Fashing in Atascosa County. beds only and that the upper members are not present in east and central Texas due to overlap by the Oakville sandstone and Lagarto clay. The supposed relationships are indicated in the diagram, figure 48. The upper portion of the Catahoula formation in east Texas is characterized by beds of volcanid ~sh, fuller's earth, and tuffaceous clays similar to those described above and resembling closely clays and tuffs in the Fant member of the Catahoula tuff beds in south Texas. The lower portion is characterized by beds of coarse, cross­hedded sandstone in places cemented with white, porcellaneous opaline silica. Details of the stratigraphy in east Texas are shown by the following described sections: 90ILight-colored igneous rock compoaed large)y of orthoclue feldapar. All its mineral con· :stituenta, except the pheoocryate, are megascopically unrecog:nizable. Section203 of a portion of th.e l~wer Catahoula formaúon at Deuils Bend on Nech.es River, one-q11.arter of a mile so1úh.east of th.e mo1úh. of Shawnee Creek in north.ern Tyler Connty. Thickness Feet 5. Sandstone, fine to coarse grained, contammg plant fragments and halls of clay. The sand grains are set in a white porcellaneous matrix of opaline quartz._______________________________ 8 4. Clay, yellowish green to greenish brown, weathering yellow to cream-colored, thin bedded, partially indurated and breaking in cubica] blocks________________________________________ 15 3. Clay, greenish brown to chocolate-brown, weathering dirty brown, the upper 6 inches solidly indurated so that it stands out as a ledge_ ____________________________________________ 4 2. Llgnite -----------------------------------------------------------------8 l. Sand and clay, greenish brown to bluish green, weathering to cream-color and containing an abundance of small fer­ruginous concretions formed around plant nuclei_________________ 5 Total thickness of section measured.________________________ 4{) Section20~ of a hillside on Moscow-Trinity road, a qnarter of a mile west of Moscow R. R. staúon., Polk County. Thickness Feet 6. Clay, light green, very calcareous, imperfectly laminated, con­ taining concretions of white, fine-te.'1es 'o. l and No. 2 are ordinary vesicular tuff; No. 3 is the siliccous type tuff ; 10 . 4 and No. 5 are 1he J!ranular light-wcight 1ypcs; and No. 6 is the ahercd or bcntonitic typc. The sandstone beds in the Catahoula consist of gray, brownish­gray, and buffish-gray, medium-and coarse-grained, cross-bedded, quartz sandstone. The most characteristic feature of the rock is its content of opaline cement. In many places the sand grains are solidly cemented by opaline silica into hard quartzite. The opal is bluish white, translucent, vitreous, and takes a beautiful polish. The distribution of the opal is irregular hoth vertically and hori­zontally. In a vertical section sorne ledges are firmly cemented and others are unconsolidated. A quartzitic ledge may change hori· zontally to loose, unindurated sand in a short distance. The texture and mineral composition of typical washed samples of the sandstone from south Texas had the following texture, shape, and mineral composition as determined by Bailey (40, p. 145, 1926): TEXTURE Sa mple No. 1" Sample No. 2" Per cent Per cent 1h mm. to 1 mm. _______________________________ _________Trace l;i mm. to 112 mm. --------------------------------------Ys mm. to 1;{ mm. ------------------------------------------­1/ 16 mm. to Ys mm. _____________________________________ 50 3515 SHAPE Well rounded ____________ _______________________________________ About 5 10 Subangular, more or less worn .___________________ 95 90 MINERAL COMPOSIT!ON Quartz -----------------------------------------·----------------30 65 Plagioclase ----------------------------------------------------28 1 Chert --------------------------------------------------------------25 5 Opal (cement) -------------------------------------------------11 24 Orthoclase and sanidine_____________________________ _ ____ 4 5 Microcline -----------------------------------------·--------1 Magnetite --------------------------·---------------------------·Trace Trace Biotite _______________________________________________________________ Trace Muscovite --------------------------------------------________ Trace Zircon ----------------------, ___________________________________ Trace Trace Glass __________________________________________________________ Trace Tourmaline -----------------------------------------------------____ Trace •Sample No. 1 is from a quarter of a mile northwest of Rockland, Tyler County. Sample No. 2 is from 5 miles southeast of Smiley, Gonzales County. Samples from Fayette County examined by Wendler2º7 yielded the following heavy minerals in addition to those listed by Bailey above: Garnet _________________________ _ ____ __ Rare Epidote --------------------------------Rare Rutile ---------------------------------Rare Spinel ---------------------------------Rare Pyrite _________________________ Common Hornblende __________________________ Rare Limonite ______________________ Abundant Titanite _______________________ Very rare . Staurolite _____________ _____________ _ Rare Anatase ___________________ Very rare Monazite _______________________________ Rare Kyanite --------------------,--------------Rare Many of the sand grains in the samples from Trinity County are highly polished as if subjected to a sand blast. Goldman (596, 907\\"endler, A. P., Heavy minerals of the Catahoula, Fayette County~ Texas: Univ. Texas. thesis, 1932. The Geology of Texas-Cerwzoic Systems 725 pp. 261-287, 1915) thought that this character might indicate an arid! climate. The cement between the grains of sand consist of a mixture of opal, chalcedony, and argillaceous material which prob· ably originated from solution of the fine volcanic dust by alkaline underground waters. The argillaceous clay beds in the Catahoula are gray or dark brownish gray and in sorne places blue, and they weather to varie­gated colors. They are tuffaceous, in places carbonaceous, and locally contain plant leaves and siliceous concretions. They are tough and plastic in most places in south Texas and more sandy and friable in east Texas. On the whole the argillaceous clays are less abundant in the outcrop than the tuffs or sandstones. The tuff is most prominent in south Texas, the sandstone in central and east Texas. In subsurface sections south of the outcrop the sands and tuffs thin and argillaceous clays and silts thicken. Conglomerate beds occur at the base of the Catahoula formation in central Texas and near the middle of the Catahoula tuff beds (Soledad member) in south Texas. The conglomerates in south Texas consist of reddish-brown and dark brownish-gray pebbles, cobbles, and in sorne places small boulders of trachyandesite, ande­site, trachyte, pumice, and chert set in a matrix of light colored, bluish-white, translucent opal and chalcedony. The pebbles are water worn, well rounded to subrounded, and measure from one­tenth of an inch to 2 feet in diameter. The common range is between 1.2 and 8 inches. Distinguishing characteristics.-The Catahoula formation can be distinguished from other formations by the following criteria: l. Preponderance of volcanic tuffs. Beds of tuff, volcanic ash, and pyroclastic materials occur in larger quantities in the Cata­houla than in other formations. Such materials occur also in the Fayette and Frío. In the Catahoula, however, they greatly predomina te. 2. Opaline cement. The sandstones, conglomerates, and in sorne places the tuff are solidly cemented by opa! and chalcedony. Opa] occurs also in the Jackson beds but in minor amounts. In the Catahoula it is the predominating cementing material and in sorne places in south Texas occurs in veins. 3. Glass. -Minute grains or spherules of glass occur in the Cata­houla, are absent or rare in the Fayette, and absent in the Oakville. 4. Coarse texture and irregular bedding. Tbe sandstones in th e Catahoula, especially in northeast Texas, are coarser textured and contain more pebbles than the J ackson strata. TI1e sands and clays are more massively beclded, and the sands are more cross-bedded and more lenticular than those of the Jackson. 5. Polished, rounded sand grains. Tbe lower sandstone beds in north Texas contain many beautifully polished, rounded grains that have suggested to geologists the name "rice sands." These polished ricelike grains set in a matrix of opal cement are espe­cially characteristic of the Catahoula formation in east Texas. 6. Absence of calcareous cement and calcareous concretions. Cal­careous cement and calcareous concretions are rare in the Cata­hou1a and common in most other formations. 7. Scarcity of fossils. Fossils are rarer in the Catahoula than in the J ackson. Paleontology and correlation.-The Catahoula formation in most places is poor in fossil remains. Shells of brackish-water Unios belonging to the genus Amblemoidea, discovered by Leslie Bowling north of La Grange in central Fayette County, were described208 recently by F. S. MacNeil. Poorly preserved shells have also been found by Lyman C. Reed nine miles south of Bryan, Brazos County. Remains of fossil plants have been found in the Catahoula at a number of places. Plants, however, are not so common as in the Fayette strata. The following list records the more common and typical forros that come from localities known to he Catahoula, as defined by the new geologic map of Texas (396c, 1932): Palmoxylon microxylon St.enzel (1) Palmoxylon cellulosum Knowlton (1 ) Palmoxylon remotum Stenzel (2) Palmoxylon lacunosum Felix (4) Lygodium mississippiense Berry (3) Acrostichum smithi Berry (3) Burseritcs catahoulensis Berry (5, 6) Cearela jacksoniana Berry (5) Localities recorded in above list­ 1. Northern Rapides Parish, Louisiana. 2. Three miles north of Waynesboro, Mississippi. 3. King, Mississippi. 4. One mile east of Galbraith, Louisiana. 5. Striker, Polk County, Texas. 6. Harmon's Creek, Walker County, Texas. I08MacNeil, F. S.• A new genue of fre1h·water mu11el from the Catahoula eandstone of Texaa; manuecript read at Oklahoma City ·meeting, Am. AHoc. Pet. Ceol., Marcb, 1932. · The Geology of Texas-Cerwzoic Systems 727 The great abundance of palms (Palmoxylon} in the flora indi­cates, according to Berry (101, pp. 229, 1916), a tropical climate. According to Stenzel, they are closely related to either Corypha or Cocus, which are found among the fossil wood collected from Oligocene beds in Antigua, a decidedly tropical country today and probably tropical also during the Oligocene period. The fern, Acrostichum, today inhabits coastal swamps associated with man­groves and nipa palms. The flora so far studied is not large enough to enable paleobotanists to determine the exact age and correlation of the Catahoula strata. Berry (101, p. 229, 1916) helieves that the basal beds of the Catahoula in east Texas from which the few plant fossils were collected are · Oligocene. Stephenson209 believes that the stratigraphic relation of the Catahoula sand in Mississippi to the underlying Vicksburg strata indicates that the Catahoula can be either Oligocene or Miocene. The final solution of the age of the Catahoula must await further more convincing evidence. MIOCENE AND PLIOCENE SYSTEMS FLEMING GROUP11º DEFINITION The clays and thin sandy strata above the Catahoula sandstone in east Texas and Louisiana were named Fleming by Kennedy (905, pp. 62-63, 1892) from exposures near Fleming, a station on the Missouri, Kansas, and Texas Railroad east of Corrigan in Polk County. Kennedy included in bis division ali the strata ahove the Corrigan sandstone (now Catahoula) and below sand deposits then referred to the Lafayette. He stated that the strata occupy a belt 15 to 25 miles wide. Dumble (494, pp. 956-983, 1903), and Veatch (1691, pp. 43-44, 1906) used Kennedy's name for about the same strata. Deussen (415, pp. 72-77, 1914) limited the Fleming to about 200 feet of clay strata occupying an outcrop about 7 miles wide above the Catahoula sandstone in east Texas and introduced a •Personal com.muaicatiou. "'ºLinJU.TUU.-Kennedy, W., 905, pp. 62~, 18!n; 911, pp. 93-95, 1896. Barrio, C. D., 66Sa, pp. 28-32. 1902. Manry, C. J., A eomparison of the Oligocene of western Europe and the 1outhem United Stateo: Bull. Am . P•l., vol. 3, p. 390, 1902. Veatch, A. C., 1688a, pp. 135­ 137. pp. Hl-J.14, 1902; 1691, pp. 43-44. 1906. Dumble. E. T., 494, pp. 956-983. 1903: 501, VI" 467­472, 1915; 504, pp. 1632-1634, 1915; 510, pp. 435-440, 1924. Rayes, C. W., and Kennedy, Wm., 692, p. 53, 1903. Deu_,., A., 415, pp. 72-77, 1914; 421, pp. 97-102. 1924. Udden, J. A., Baker, C. L., and Büae, E., 1652, pp. 89, 90, 1916. new name, Dewitt formation., to include a series of beds occupying in south Texas about the same stratigraphic position as the Fleming. Udden, Baker, and Bose (1652, p. 89, 1916) followed Kennedy's and Dumble's terminology. The name carne into general use to designate the strata in east Texas between the Catahoula and Lissie (Pleistocene beds). The same sequence of strata in south Texas that Deussen named Dewitt was divided by Dumble ( 478, pp. 556-559, 1894) in to three forma­tions, Oakville, Lapara, and Lagarto. Deussen ( 421, p. 97, 1924) and Trowbridge (1610, p. 98, 1923) later abandoned the name Dewitt and used Dumble's south Texas names, Oakville, Lapara, and Lagarto. The United States Geological Survey in preparing a new geologic map of Texas mapped the sandy strata above the Cata­houla from Nueces River to the Brazos as Oakville sandstone. They decided, however, to use Dumble's name Lagarto for the beds above the Oakville and dropped the names Fleming and Lapara. The Oakville is really a sandy facies of the lower and southwestern portian of the Fleming. lt grades laterally and vertically into the clay. In view of the difficulty of separating the Oakville and Lagarto beds in Texas east of the Brazos, it seems preferable to retain the name Fleming as a group name to include ali the strata above the Catahoula form;ation and below the sands of the Citronelle group and to apply the names Oakville and Lagarto to formational divisions of the Fleming group. The strata of the Fleming group consist of yellow . and green clays, gray sandy clays containing layers of pink and brown clay, in sorne sections a thin !ayer of chalky limestone, and lentils and layers of cross-bedded sand. Small calcareous and ferruginous nodules are common. Toward the base in the portion of the section corresponding to the Oakville the clays are dark greenish gray streaked with hrown and purplish-gray shades. They contain much more sand than the upper heds. Ali the strata are calcareous and contain redeposited Cretaceous foraminifera, chara fruit, calcareous nodules, and aragonite prisms thought to have been derived from lnoceramus plates. The subsurface strata near the coast are inter­bedded with severa} marine layers of well bedded sandy clay 50 to 200 feet thick containing marine Miocene fossils. The total thick­ness of the Fleming group in the oíl fields is 2000 to 2700 feet. The Geology of Texas-Cenozoic Systems 729 The beds lie unconformably upon the Oligocene strata in the sub­surface sections and lie unconformably upon the Catahoula forma­tion on the outcrop. They are overlain conformably by Pliocene strata. The type locality for the Fleming group comprises the exposures along the Missouri, Kansas, and Texas Railroad east of Corrigan and near the station of Fleming in Polk County. The section as descrihed by Kennedy (692, p. 52, .1903) at this place is as follows: Section o/ the Fleming strata along the Missouri, Kansas, and Texas Rail­road near Fleming in the eastern edge o/ Polk County. Thickness Feet 6. Sand, gray -------------------------------------------------------------------------1,1¡ 5. Sand, brown, mottled ____________________________________________________________________ 2-4 4. Sand, gray, stratified, containing fossil palm wood in great abundance and pebbles of quartz and jasper ----------------------------2(} 3. Clay, bl ue, partially stratified, showing a tendency to break into conchoidal blocks, and containing numerous calcareous nod u! es ------------------------------------------------------------------------------------------50 2. Clay, red, having same structure as bed above, but containing no concretions ------------------------------·---------------------------------------------· 10 l. Sand, yellow --------------------------------------------------------------------------------------4 Total thickness measured. __________________________________________ 88% SUBDIVISIONS The outcrop of the Fleming beds in central and south Texas has been divided into the two following formations, which are described in stratigraphic order :· 2. Lagarto l. Oakville OAKVILLE FORMATION21t Definition.-The Oakville sandstone was differentiated from the Fayette group of beds by Dumble (478, pp. 556-559, 1894) and assigned to the Miocene.212 Dumble described the formation as 2111.iTZRATVRB-Dumble, E. T., 478, pp. 556-559, 1894; 494, p. 957, 1903; 501, p. 476, 1915; 506, pp. 228-243, 1918. DenHen, A., 415, pp. 74-76, 1914; 421, pp. 97-99, 1924 ; and Dote, R. B., 416, p. 156, 1916. Bailey, T. L., 38, pp. 95, 96, 1923; 40, pp. 52-58, 1926. Trowbridge, A. C., 1610, p. 98, 1923; 1613a, pp. 165-181, 1932. Applin, P. L., 33, pp. 21-23, 1925. Bose, E .. and Cavina, O. A., 135, pp. 128-133, 1927. Sayre, A. N .. Ground-water resources of Duval County: U. S. Geol. Survey Press Rpt., p. 7, Feb. 12, 1933. lll2'fhe announcement of the discovery of extensive Miocene strata in Texas was first made by Shumard (1474, p. 140, 1863) baaed on the determination of fossil bones identified by Leidy (980, p. 416, 1861). sandstone, grits, gritstone, and silt interhedded with clay making up a section of strata hetween the Frio clay (now Catahoula formation) and the overlying Pliocene clay. He thought the formation was confined to south Texas and correlated it with the lower half of the Fleming clays of east Texas. Deussen (421, p. 97, 1924) descrihed the formation in more detail, hut did not change essentially Dumhle's definition. Bailey (38, pp. 52-53, 1923) followed Dumhle's definition in descrihing the Oakville formation in the Colorado River valley in Fayette County, hut later in descrihing the strata in south Texas he · (40, pp. 52-58, 1926) restricted the Oakville as mapped by Deussen and included the basal strata in his Gueydan formation (now Catahoula). Trowhridge in two papers (1610, p. 98, 1923; 1613a, pp. 165-181, 1932) used the name ahout as originally defined by Dumhle. The United States Geological Survey in their preliminary map of Texas (396c, 1932) used the definition of Dumhle and Deussen in mapping the formation in south Texas and have differentiated its outcrop as far east as Brazos River. The Oakville formation is now made to include ali the strata of Miocene age ahove the Catahoula formation and helow the Lagarto clay. The type section comprises the exposures on Nueces River in the vicinity of Oakville, Live Oak County. Regional, geology.-The Oakville formation as now delineated extends in a continuous outcrop ahout 8 miles wide from Navasota in Grimes County through Washington, Fayette, northwestern Lavac~ De Witt, Karnes, and Live Oak counties to the southwest comer of Duval County (figs. 49, 50). From Duval County southward it is .overlapped throughout most of the area by Pliocene deposits. It occurs, however, in a few isolated spots, for example, near Torre­cillas in Wehh County, on Mulato Creek in the northeast comer of Zapata County, and north of Rio Grande City in Starr County. It occurs also on the Mexican side of the Rio Grande. In southeast Texas from northeast of Navasota in Grimes County eastward the Oakville formation has not heen differentiated from the Lagarto clay. It is thought that it is not overlapped by the younger deposits as in south Texas, hut that east of Brazos River the Oakville sands change to a clay facies and merge with the lower part of the Lagarto formation and cannot he, or at least have not heen, distinguished from the Lagarto. Miocene vertehrate fossils The Geology of Texas-Cenozoic Systems 731 similar to vertehrate fossils in the Oakville have been discovered near Cold Spring in San Jacinto County and at Red Bluff on Trinity River. The fonnation changes also southward heneath the surface. Ahout 50 miles south of the outcrop the Oakville heds merge with and are interhedded with marine Miocene clays and sands, and hecome important oil·producing zones in the salt dome oil fields. Fig. 49. Outcrops of the Catahoula and Oakville fonnations in south-central Texas (compiled fr<>m Univ. of Texas theses by Carroll Cook and A. P. Wendler). The thickness of the Oakville formation varíes along the strike of the outcrop from 200 feet in northeast Texas to 500 feet or more in south Texas. Its thickness increases also beneath the surface toward the coast line, as shown in the following table: LOCALITY COUNTY THICKNESS AUTHORITY Feet Brazos River section___________________ Washington 200 A. Deussen Deep well at Galveston _______________ Galveston G. D. Harris 720+" Colorado River section ______________ Fayelte and Colorado 495-550 T. L. Bailey Stratton Ridge salt dome ____________ Brazoria lOOO+b P. Applin Niels-Esperson well, 15 miles east of Brownsville_____________ Cameron 175 + Julia Gardner Nueces River section _______________ Live Oak 300 A. D ussen O u tero p ---------------------------------------------D u val 500 A. N. Sayre ªBottom of Miocene etrata not reached. bThe thickening of the Oakville toward the coast is due aomewbat to actual thickening of the slrata, but also to a large extent to the fact tbat the basal portion of the Lagarto clay cannot be difierentiated from the marine Oakville beds, and the two divisions are measured together. Stratigraphy.-The Oakville formation overlies the Catahoula unconformably and in turn is overlapped unconformably by the clays of the Lagarto formation (fig. 48). In sorne places the basal contact is marked by a conglomerate made up of rolled water-worn Cretaceous fossils and pebbles. In other places the contact is between coarse-grained sand above and greenish-or yellowish-white, tuffaceous clay below. The Oakville formation is wholly continental in origin at its outcrop. It is of more or less uniform composition and has not been subdivided into mappable members. The northeast portion of the outcrop contains a larger proportion of clay than the southwest district. In other respects the Oakville is generally uni­form in character throughout its outcrop. The following sections compiled from literature give a good idea of its stratigraphic features: Section213 o/ Oakville Jormation exposed at Hidalgo bluf] on Brazos River in Washington County. Thickness Oakville--Feet 9. Sandstone and d ay, light gray to yellow, generally coarse grained, but ranges from very fine· to coarse, irregularly bedded. The beds are from 2 to 6 feet thick, rnassive in sorne places and laminated in others_________________________________________ 29 lllllMeaaured by W. W. Kelley, 506, p. 239, 1918. The Geology of Texas-Cenozoic Systems 733 Thickness Feet 8. Clay, dirty yellow or grayish, calcareous, weathers to produce badland íorms ·-·-···-····-···-···-···-····----···--···-···-----16 7. Sand, unconsolidated, medium grained, containing severa] len­tils oí consolidated sand, rolled and redeposited Cretaceous fossils, and one fragment of a bone ·······-···-···-···-·········-····· 11 6. Clay, dirty yellow or gray, containing .calcareous nodules and a lentil of yellowish sand ·------···-···-·--·-··········-···-·····--17 5. Sand, uuconsolidated except the upper 6 inches, which is in­durated. The sand contains rolled Cretaceous fossils, frag­ments of silicified wood, and a layer of pebbles at its base 5 4. Sandstone, gray to yellow, cross-bedded, ranging in texture from a conglomerate made up of sandstone pebbles to a fine sand -------------------------··-···--·--···-------------·· 26 3. Coqujna, white or gray, composed of small fragments of Cre­taceous fossils mixed with a little fine sand. The fossils are rolled and water worn..·--------·-·-·····--·--···-···-····-5 Catahoula ?­ 2. Clay, buff or dirty yellow, fine grained, sandy, standing up to exhibit a vertical section. ______________________________________ 20 l. Clay, light blwsh gray, containing streaks and nodules oí cal­ careous matter, less calcareous at the base, partly covered by detritus -·-····-··-------------------------------54 Total thickness measured ··-···-····-···--·-·-···-····-·····-···-· 183 Section214 o/ Oakville formation on a hill just ea.st of Santa Cruz ranch 5 miles southeast of Río Grande City, Starr County. Thickness Feet 6. Clay, pink --····--··------·-··--····-···-····-----------······-······· 23.l/z 5. Clay, hard, nodular, forming a protruding ledge___________________ 1 4. Clay, pink --···-·-··-···-·-·-···-·····-·------------------2112 3. Sandstone, gray, massive, irregularly bedded _____________________ 11 2. Clay ------------------------------------_.__ 3 l. Sandstone, hard, blocky. The sandstone at a Jocality nearby contains pellets of clay believed to have been derived from underlying Frio wbich weather out leaving round cavities in the sandstone -------------··-···-··-·-·····----------------4-5 Total tluckness measured ___________________________ 46 Sedimentology.-The sediments of the Oakville were deposited by streams on a gently inclined coastal plain along the border of a ''"Meaaured by A. C. Trowbridge, 1613a, p. 171, 1932. sea and merged seaward with marine deposits.21 5 The physical geography of the Oakville epoch was somewhat unusual. Condi­tions must have favored rapid deposition of material derived from sources comparatively near at hand by streams that established enormously wide flood plains. Large quantities of redeposited Cre­taceous shells prove that the sediments were derived largely from Cretaceous outcrops, carried across the older Tertiary areas, and deposited in great quantities in the form of broad alluvial sheets or aprons. A very large mass of Cretaceous marl must ·have been transported to secure in places so rich a concentration of Cretace­ous shells. Perhaps the deposition of so much volcanic ash during the preceding Catahoula epoch so changed the character of the soil that much of the land flora disappeared on the Cretaceous uplands. Before a new flora became adjusted to the new environment produced by a mantle of ash, the barren uplands eroded easily and water un­obstructed by plant life ran off rapidly causing great floods after each rainy period. Only by rapid erosion and great quantities of water in rivers constantly shifting over a featureless plain can such thick and extensive sheets of redeposited Cretaceous shells, coarse-grained, lenticular, cross-bedded sand beds, and bone-bearing clay beds be explained. Lithology.-The strata of the Oakville formation consist of about 40 per cent sand, 30 per cent sandy and ashy or bentonitic clay, 20 per cent marl, 5 per cent redeposited Cretaceous shells, and 5 per cent gravel. The sand is light gray in most places, friable, medium grained, intricately cross-bedded, calcareous, and in places more or less indurated. Bailey ( 40, pp. 55, 1926) found that a typical washed sample had the following mineral composition: Per cent Quartz --------------­---------­------------------------------------------------­------------------­--­ 40 Calcite (!argel y cernen t ) ------------------------------------­--------­----------------------­ 25 Chert ------------------­----------­-------­----------------------------------------------­----------­ 20 Orthoclase -------------------------------------------------------------------­--------­---­ 6 Plagioclase --------------------------------------------------------------------­---------------------­ 7 Water-worn shell fragmen ts·--------------------------------------------------------------­ 2 Traces of microcline, biotite, magnetite, limonite, zircon, barite, chalcedony, and reworked foram inifera. ....iley, T. L., 38, pp. 95-96, 1923. Tke Geology o/ Texas-CenozoiC Systems 735 At sorne exposures the sand grains are cemented with chalcedony or opal in place of calcite. The siliceous rock is exceedingly hard, breaks with a conchoidal fracture, and resembles quartzite in every way. The sand grains are subangular to angular, made up of quartz, feldspar, and calcite, and have according to Trowbridge (1613a, p. 176, 1932) the following texture anal ysis: DIAMETER OF GRA i ·5 mm. Per een.t -~ to ~ ·----·----------------------------------------------------·---------4.5 7$ to 1/Í..--------------------··-------------·--------------------------------35 1/ 16 to ----·-·----·-----------·-·-·----·-----·----------------------·-----------11 1/ 32 to l/ 16 ---·-----------· ····-----·--·------------------------------------------~ 1/ 64 LO 1/ 32 -----------·--·------·--··-·--·-----------------------------------------·---· ~ Smaller than 1/64 ------·------·-------------·------------------·-·-------------------------8 The clay is gray or dirty yellow, compact in most places, poorly laminated, calcareous, containing in places much marly material, reworked foraminifera, and oyster and other shells derived from the Cretaceous deposits. In other places the clay contains much rede­posited volcanic ash derived from the Fayette and Catahoula forma­tions. In a few places in south Texas the ash is so pure that it is thought to be original and derived from volcanic sources during Oakville times. In the places where the ash is particularly abundant it is cemented in places into hard lentils of chalcedony by infiltrating siliceous waters. The indurated siliceous clay, according to Trow­bridge (1613a, pp. 178-179, 1932), is an extremely hard, grayish to brownish-gray, fine-grained siltstone resembling chert. It may occur in the forro of concretions, as thin lenticular seams, or as pipes.216 A thin-section under the microscope reveals minute angular quartz grains less than one-eighth of a millimeter in diameter set in a brownish-gray clay matrix together with sorne calcitic cementing material, limonite aggregates and streaks, and minor amounts of chalcedony in veins and segregations. Trowbridge thinks that the material in one part of the section was cemented originally with calcite and that in another part with chalcedony. Most of the rock is now cemented with silica, which in the form of chalcedony has replaced the calcite. --rhe pi~ aeeordinc to Lonadale, are poaibly aocient volcaoic •ents filled with eiliea. l>e1aMeD has thoqht these siliceoue deposite micht be asaociated with fauh or fracture linea and prodaced by aacendiog siliceoua waten. Distinguishing characteristics.-The Oakville formation is dis­tinguished from the Lagarto clay above and the Catahoula forma­tion below by the following criteria: l. Redeposited Cretaceous fossils. The Oakville strata contain in many places, both in outcrop and in core sam:Jles obtained lrom wells, water-worn Cretaceous fossils and fragments of shells and fora minifera 'redeposited from tl'e Cretaceous marls. The Catahoula . Chalcedony. The Oakville strata in south Texas contain more lentils, veins, and pi pes of chalcedony in the form of siltstone than the Lagarto or Catahoula. The Catahoula has much opal­ine cement but less chalcedony in the form of separate ag­gregates. 4. Vertebrate bones. The clays in sorne places contain bones of mammals that distinguish the strata from the Lagarto and CatalJOula. Similar bones occur in the Lagarto, but they are of Pliocene age. 5. Lithology. The Oakville contains a much larger percentage and thicker, more massive beds of sand than the Lagarto. lt con­tains less ash and more sand than the Catahoula of south Texas. The sand grains are more angular and less polished than the sand grains in the Catahoula. 6. Clay halls. The rapidly deposited sands of the Oakville have halls, nodules, and small lentils of clay imbedded in the grit. These clay halls are not common in the Catahoula sand. 7. Prorninent escarpment. In many places the Oakville is suffi­ciently indurated to produce a prominent cuesta. In south Texas the formation forms the Bordas escarpment. Paleontology.-The Oakville formation contains no marine fossils on the outcrop. In well sections in the salt dome oil fields it yields a rich marine fauna that distinguishes it easily from the formations above and below. The following fossils have been identified from the lower Fleming strata at Stratton Ridge salt dome, Brazoria County, by Mrs. Applin (33, pp. 25-29, 1925): The Geology of Texas-Cenozoic Systems 737 Mulinea lateralis Say Mactra quadricentennialis Harris Ostrea sp. Glycimeris sp. Balanus sp. Cerithiopsis sp. Pecten sp. Olivella sp. Chione cancellata (Linné) Cylichna bidentata var. galvestonen­ atica cf. N. eminuloides (Gabb) sis Harris Corbula cf. C. seminula Dall "Pleurotoma" cf. P. calvertensis Clark Corbula inaequalis Dall Strombina sp. Arca transversa var. busana Harris Rotalia beccarii (Linné) Arca incongrua Say Cibicides americana (Cushman ) Nassa trivittata Say Elphidium sp. Leda sp. Quinqueloculina sp. Mactra lateralis Say A collection of these fossils was studied by Olsson,217 who reported them to be definitely Miocene in age probably representing middle Miocene assemblages. The following fossils have been identified from the Miocene strata in the Niels-Esperson well, 15 miles east of Brownsville, by Miss Gardner (1613a, p. 182, 1932): N ucula sp. indet. Adeorbis sp. Leda sp. cf. L. proteracuta Gardner Architectonica? sp. Leda sp. indet. Natica (Cryptonatica) cf. N. (C.) Pecten aff. P. eboreus Conrad pusilla Say Pecten? sp. · Polynices sp. Cardium (Cerastoderma) sp. indet. Turritella sp. cf. T. terebriformis Dall Tellina sp. indet. Alectrion? sp. Corbula (Caryocorbula) cf. C. (C.) Oliva cf. O. literata Say nasuta Dall Cancell aria n. sp. Corbula sp. indet. Cancellaria? sp. Dentalium sp. indet. Drillia n. sp. Cadulus? sp. Miss Gardner -396, 1930. Hoote, H. W., 841, pp. 38-126, 1925. Gould, C. N., and Lonsdale, J. T., Geology of Texas County, Oklahoma: Oklahoma Geol. Survey Bull. 37, 1926. Reed, L. C., and Longnecker, O. M., Jr., 1288a, pp. l-98, 1932. Baker, C. L., Conjecturea on the Cenozoic history of the Texas Plaine: MS. eubmitted to Bur. Econ. Geol., Aug., 1932. Stirton, R. A., 1546b, pp. 147-168, 1932. the first connected account of the geology of the area. His puhlica­tions drew the attention of paleontologists to the region, and Cope (305, p. 177, 1892; 308, pp. 49-50, 1892) and Gidley (582, pp. 617-635, 1903) made extensive collections of vertehrate fossils and recorded observations on the stratigraphic sequence. Gidley gave names to three divisions of the section, and C. N. Gould (614b, pp. 1-64, 1906; 615, pp. 1-70, 1907) published comprehensive reports on the geology an~,the water supplies of the Panhandle of Oklahoma and Texas. Lull (1028, p. 117, 1913; 1026, pp. 327-385, 1915) led an expedition for Y ale University into the Panhandle area, made collections of vertebrate fossils, and hoth he and his assistant, Troxell (1614, pp. 613-638, 1915) published descriptions of sorne of them. Baker (42, pp. 1-225, 1915) studied and described the geology and underground waters of the Llano Estacado and con­trihuted much to the knowledge of west Texas. Eight years later Patton (1180, pp. 1-180, 1923) described the geology of Potter County, and Udden (1661, pp. 72-74, 1923) puhlished additional descriptions of the rim rock of the High Plains. Matthew,2• 5 just hefore his untimely death, prepared a manuscript setting forth his observatio-ns of the Tertiary geology of the northern Staked Plains in Texas. Hoots (841, pp. 33-126, 1925) studied and descrihed the strata in eastern New Mexico and western Texas and published a comprehensive bulletin describing the surface and subsurface sec­tion. More recently Matthew and Stirton ( 1072, pp. 171-216, 1930; 1073, pp. 349-396, 1930) have identified a large collection of verte­hrate fossils from Pliocene sands northeast of Miami in western Hemphill County. Finally, Reed and Longnecker (1288a, pp. 1-98, 1932) published a detailed account of the geology of Hemphill County, and Baker has completed a manuscript on the geologic history of the Texas High Plains. Altogether more than forty articles have been written on the geology and paleontology of the Cenozoic deposi.ts of west Texas. DEFJNJTJON The Pliocene strata include all the deposits above the Triassic and Cretaceous rocks and below the Pleistocene stream and terrace sands. The strata rest upon the Dockum beds of Triassic age in :u.5Matthew, W. D., Ohservationa on the Tertiary of the Staked Plaina: MS. aubmitted to American Museum of Natural Hiatory, 1924. The Geology of Texas-Cenozoic Systems 765 the northern and western part of the Llano Estacado and upon upper Comanchean strata in the southern portion. The beds consist of a basal conglomerate overlain by 200 to 650 feet of sand, sandy clay, sand containing lentils of clay, a little volcanic ash, and sorne fine wind-blown sand and silt. SUBDIVJSIONS The Cenozoic strata of the Llano. Estacado have received the fol­lowing names in geological literature: Loup Fork beds. This name was used by Cummins (346, pp. 203-208, 1893) to designate the oldest Tertiary strata in the Panhandle thought then to be of Miocene age. Blanco beds. The term Blanco division was used by Cummins (342, p. 431, 1891; 346, pp. 200--201, 1893) and made to include the strata that outcrop along the rim of the Llano Estacado from Double Mountain Fork of Brazos River on the south to Paloduro Canyon on the north. These beds have a thickness of about 160 feet. Panhandle formation. This name was proposed by Gidley (582, pp. 634--635, 1903) to include the finer clay deposits of the High Plains above the Mesozoic and Paleozoic beds and below the Recent sands. This unit as originally defined appears to be more or less equiva­lent to the Blanco beds of Cummins. Clarendon beds. These beds were named by Gidley (582, pp. 632-­634, 1903) to denote strata that occur north and northeast of Clarendon in Donley County. These beds had previously been called Loup Fork by Cummins, as he regarded them as equivalent to the type section in Nebraska, but they are now known to be lower Pliocene in age and therefore younger than the Loup Fork. Goodnight beds. This name was given by Cummins (346, pp. 201­203, 1893) to sands outcropping at the head of Mulberry Canyon and thought by Cummins to be older than the Blanco beds. Matthew and Stirton have since confirmed this opinion (1073, pp. 365--366, 1930) . Potter formation. This name was proposed by Patton (1180, p. 78, 1923) for the coarsely stratified and more or less consolidated sand and grave! above the Dockum beds and below the Coetas forma­tion exposed along Canadian River in Potter County. Coetas formation. This formation was named by Patton (ll80, p. 80, 1923) and made to include the slightly consolidated sand and sandy limestone strata above the Potter formation and below the surface silts and marls occupying the surface of the Llano Estacado. The formation has a thickness of about 200 feet. The type locality is along Coetas Creek in eastern Potter County. Hemphül beds. This name was given to the upper-lower Pliocene strata in the Canadian River valley by Reed and Longnecker (1288a, p. 20, 1932). The formation includes all the strata in Hemphill County ahove the Triassic formations. It is thought by Matthew to be older than the Blanco division and probably younger than the Oarendon. Jt is quite possible that the Hemphill beds are equivalent to the Goodnight beds of Cummins. Most of these names apply to local areas only and can not he used to separate the Cenozoic deposits of the High Plains into stratigraphic divisions outside the respective areas in which they were named. Gould pointed out (614b, p. 27, 1906) that it is im· possihle to separate the deposits of this area into mappahle divi­sions that can he traced and designated as stratigraphic units. Matthew246 used Gidley's namé Panhandle formation to apply to the entire Cenozoic section in the west Texas plains. On a hasis of his large collections of vertehrate fossils he was ahle to determine three divisions, as follows: Panhandle formation­ 3. Blanco beds, middle Pliocene. 2. Hemphill (Goodnight) beds, upper-lower Pliocene. l. Clarendon beds, lower Pliocene. The age relationships of these heds are discussed by Matthew and Stirton ( 1073, pp. 365-366, 1930), as follows: l. The Hemphill fauna, especially the equids, is a later phase than Clarendon, so far as the latter can be judged from described material. 2. The four equid species agree quite closely with the four types of Equidae distinguished by Cope in the "Goodnight" beds. So far as published material shows they do. not agree closely with Oarendon specimens referred to these species by Gidley. 3. The typical Clarendon species are nearly allied to those from Hemphill, although more primitive, and they may well have been comparatively direct ancestral stages or mutations. 4. The Blanco fauna in turn is more advanced than the Hemphill, the Equidae carrying on two of the four types into furthe; di· vergence (Plesippus simplicidens, Hipparion phlegon), the Borophagus with a larger species, the Proboscidea with Steg­omastodon in place of Rhyncotherium, rhinoceroses absent and 2i8Matthew, W. D., Observations on the Tertiary of the Staked Plaina: MS. submitted to the American Muaeum of Natural History, 1924. Matthew, W. D., and Stinon, R. A., 1073, pp. 364-367, 1930. The Geology of Texas-Cenozoic Systems 767 glyptodonts present. The gap between HempJ:iill-Goodnight and Blanco appears to be wider than between Hemphill and Clarendon. PANHANDLE FORMATION... Definition.-The main body of the banded "clays" that underlie the Staked Plains were named Panhandle formation by Gidley (582, pp. 634-635, 1903). The unit was defined more definitely by Matthew248 and made to include ali the strata on the Staked Plains above the Cretaceous and Triassic formations below and the Recent surface deposits. Regional geology.-The Panhandle formation overlies uncon· formably the varíegated green and purple clays and sandstones of the Triassic Dockum formation, and it is overlain by the buff Gands of the Recent wind-blown deposits. lt extends from Crosby County northward into Oklahoma and Kansas. Southward from Crosby County the formation grades into the Recent wind-blown sand. Ac­cording to Baker249 no fossiliferous Cenozoic beds have been found on the Llano Estacado south of the headwaters of Brazos River, and consequently it has been impossible to correlate the strata of the southern part of this area with the fossiliferous beds farther north. The Panhandle formation is best known from exposures around the east-facing escarpment of the Llano Estacado and in canyons that cut back into the escarpment. Its thickness has not been deter­mined in many places. In Hemphill County Reed and Longnecker (1288a, fig. 2, 1932) found the thickness of the lower Pliocene strata to be about 550 feet, which is the maximum thickness so far meas­ured. Their Hemphill strata, according to Matthew, represent only the middle portion of the Panhandle section. The thicknesses de­termined by Reed and Longnecker are as follows: LOCALITY COUNTY THICKNESS AUTHORITY Feet Generalized section ··········-···-··- Hemphill 550 Reed & Longnecker Iones No. 1, Gibson Oíl Co...­.. Roberts 512 Do George No. 1, Fisher Oíl Co.______ Hemphill 465 Do lM7LITERATtJRE--Gidley, J. W., 582, pp. 617-{;35, 1903. Baker, C. L., 42, p. 32, 1915. Matthew, W. D., Ohservations on the Teniary of the Staked Plains: MS. aubmitted to the Amer. Mus. Nat. Hist., 1924. Udden, J. A., Baker, C. L., and Bose, E., 1652, p. 91, 1916. 2'BMattbew, W. _D.• Observations on the Tertiary of the Staked Plains: MS. submitted to the Amer. Mus. Nat. Hist., 1924.. 249Baker, C. L., personal communication. 768 The University of Texas Bulletin No. 3232 Stratigraphy.-The character of the formation is shown by the following descrihed section that outcrops in Hemphill County: Composite section250 o/ Pliocene strata exposed in Hemphill County. Thickness "D" member-Feet Sand, buff, fine grained, unconsolidated, covering the surface and containing in places much white or grayish-white caliche__________ 75 Sandstone (key bed No. 1-A), gray, friable, faintly laminated, cemented at the surface in mo~t places by white caliche to form the cap rock exposed alon~ the tops of escarpments_______ 10 "C" member-Clay, sandy, brown, unconsolidated_______________________________________________ 15 Sandstone (key bed No. 1), notably very light gray to white, cal­careous and clayey, contains volcanic ash locally. This sand­stone constitutes a persistent bed that caps the next to the highest esca1·pment and mesas in western Hemphill County______ 10 "B" member- Clay, brown, sandy in sorne places______________________________________________ 45 Sandstone (key bed No. 2), gray, laminated, friable, contain­ing sorne gravel and clay pebbles_________________________________________ l0---25 Clay --------------------------------------------------------------------------------30 Sandstone, buff, massive________________________________________________________lS--50 Sandstone (key bed No. 3), gray, massive, indurated to friable, containing a little gravel and sorne vesicular lava boulders from 3 to 6 inches in sorne places__________________________________________ 5-25 "A" member- Sand, buff, slightly resistant, massive, containing stringers of cal­careous material ---------------------------------------------------------4 Sand, buff, soft to well indurated, weathering to form blocks, shows fine laminations---------------------------------------------------8 . Sandstone, light buff, very fine grained, loesslike______________________ 15 Sand, reddish to buff, fine grained, loesslike, massive, weathers to form steep bluffs and contains a little clay as a mátrix in the lower part of the hed_________________________________________________________ 22 Clay with little grit, dark brown, containing few calcareous nodules ------------------------------------------------------------------------------6 Sand, reddish buff, massive, medium grained, contains a little clay and numerous calcareous nodules ___________________________________ 32 Sand, coarse, made up of irregularly sized grains in a matrix of reddish-brown clay, contains abundance of calcareous nodules 5 Clay, brown, mottled with greenish tints_ _______________________________ 3 Sand, dark brown, medium to coarse grained_________________________________ 6 t:iOCompiled from descriptions by Reed and Longnecker, 1288a, fig. 2, pp. 16-39, 1932. The Geology of Texas-Cenozoic Systems 769 Sandstone, brown or dark buff, massive, coarse grained, made up of much arkosic grit from .5 to 3 mm. in diameteL·-····-········ 60 Clay, brown, sandy.·-····-····-···-····-··········-···-········-····-····-----·-5 Clay and brown silty sand .. ·-··············-··-··-······-······-··-······-··-······-··· 20 Sand, white to greenish, calcareous ... -...............·-·····-··-················ 10 Section unexposed ·····-··-···-···-····-····-····-···-····-····-···--···-··-···· 50 Sandstone, grayish brown, friable, coarse grained, in places con­ taining fow thin clay partings .. ·-····-···-·····-···-····-···-·····---··-···· 16 Section unexposed ···-··········-···-····-····-···-····-···-·········--··-···-···· 25 Sandstone and conglomerate, gray to buff, well indurated in places, containing clay halls and other material derived from the underlying red beds____________________........ ·-··········-·-·········-········· 15 Average thickness of lower Pliocene section ..·-·--················ 550 Sedimentology.-The sediments of the Panhandle formation rep· resent a broad piedmont alluvial apron that was laid clown on a gently inclined plain by streams that flowed eastward from the Sangre de Cristo and Sierra Grande uplift of New Mexico. Deposi­tion took place during an epoch when rainfall in western Texas and eastern New Mexico was heavy. Streams swollen by heavy rains flowed swiftly clown the mountain slopes and debouched abruptly on the nearly flat treeless plain of the mountain foreland (fig. 51). As a result of the sharp slacking of the flow of the streams on reaching the gentle · gradient of the plain, large amounts of their loads of sedi­ments were deposited. Faris were built outward until they coalesced to produce the broad alluvial apron represented now by the thick mantle of alluvial deposits that constitutes the present Cenozoic deposits of the High Plains. During epochs or intervals of little rainfall, when the streams carried little coarse sediment, the larger rivers were able to erode and to deepen their channels. Wind also became an agent of sorting and in redepositing finer material that produced beds of loess and silt. With renewed rains, channels were again filled and finer material in the form of mud was washed into the depressions between alluvial ridges and became the clay lentils. Showers of volcanic ash contributed sorne of the finer sediments. Thus, the remarkable sheet of continental deposits was slowly built up. Streams in west Texas and eastern New Mexico are at present carrying much less water than they did during the Pliocene and Pleistocene epochs. Erosion is now in excess of deposition, and the larger streams, like Canadian River, have cut deep channels through Fig. 51. Evolution of the physiography of northwest Texas and southeastern New Mexico. A, Area during Pliocene times showing alluvial deposits east of the high mountains in New Mexico. B, Area during present epoch showing capture of eastward-flowing streams of Pliocene times by the head-waters of Pecos River. The Geology of Texas-Cenozoic Systems 771 the sand deposits of the Llano Estacado. The surface strata too are cemented by caliche and other forms of calcium carbonate to form a hard cap rock, so that the strata form steep escarpments and canyon walls. The greater hreadth of the ancient river channels compared with those of present streams and the presence of so much caliche in the Recent surface sands and its ahsence in the lower heds indicates a somewhat more arid climate now than during Pliocene times. Baker helieves that the larger streams of past epochs were caused by much higher mountain ranges in New Mexico during Pliocene times. The greater altitudes induced greater precipitation, and the steeper gradients intensified erosion of the mountain slopes and deposition on the surrounding plains. The original mass of Cenozoic sediments in the Llano Estacado is estimated to have heen at least 6000 cuhic miles, an amount equal to a mountain mass 300 miles long, 20 miles wide, and 5,000 feet high. Although uplift and erosion may have heen contemporaneous, it is probable that the great amount of denudation during and since Pliocene times has lowered New Mexico elevations considerahly. Marked changes in stream courses have taken place since the Pliocene epoch. The southward-flowing streams, which have the shortest course to the Gulf of Mexico and consequently the steepest gradient, have an advantage in this valley-cutting process and have eroded their valley heads farther back and have captured many of the former eastward-flowing streams. Thus Sulphur Draw, head­water tributary of ·the ColOrado, was beheaded by the Pecos. Later the upper Portales River was cut off by the Pecos and diverted southward into the Rio Grande. Fans are no longer forming, and the Llano Estacado, once the site of so much deposition, is now heing slowly cut away251 by slow recession of the great eastern es­carpment and the downward and lateral erosion by the streams that have cut deep canyons into this great alluvial formation. Lithology.-The sediments of the Panhandle formation consist on the average of ahout 60 per cent sand, 23 per cent clay, 10 per cent arkosic grit, and 7 per cent gravel and conglomerate. The sand is gray, coarse to medium grained, contains in sorne places lentils and halls of red clay and in sorne places lentils of gravel. The grains m1Baker, C. L, Conjecturea on the Cenozoic hiatol"J of the Texas Plains: MS., 1932. in most places are subangular and are made up largely of quartz with some feldspar, a little magnetite, phlogopite, biotite, and a trace of epidote. The largest portion of the grains (about 65 per cent) range between 0.5 and 2 millimeters in diameter, as shown by the following mechanical analyses: Mechanical analyses252 o/ /our typical samples o/ the Panhandle formation /rom Hemphill County. SCREEN SCREEN SAMPLES MESH NO. SJZE 5 6 7 8 mm. Per cent 10--------------------------21h 4 o 2 o l C>--20 -------------------------2%-114 15 7 12 2 20-40_______________________ l 14-5/6 18 9 15 8 40--60______________________ 5/ &-5/8 12 10 10 6 6(}... 80___________________ _5/8-5/12 15 18 13 10 80--100__ ________________________5/ 12-5/ 16 14 16 12 14 100-120 ------------------------5/l&-14 5 8 5 10 120-140 -----------------------·--%-5/ 24 4 7 4 9 140--160·-----------------------5/ 24-5/ 28 2 3 3 5 160-180_______ _________________ 5/ 28-5/ 36 1 1 2 2 180-200________________________ 5/ 3&-l¡f; 6 11 10 24 200_________________________ %­ 4 10 10 16 The clay is brown or buff. In many places it is poorly bedded, in others it is laminated with thin silty partings that produce thin bedding planes. The beds are lenticular and grade in short dis­tances into sandy clays and sand. The conglomerate in most places occurs in the. basal part of the section where it constitutes a basal conglomerate. The material con­sists of rounded and subrounded pebbles, cobbles, and in sorne places boulders derived partially from the underlying red beds and in part from distant sources. The pebbles are composed of meta­morphic, igneous, and sedimentary rocks, of which quartz, chert, and quartzite are the most common, although in places igneous peb­bles are present in appreciable proportion. The sizes vary from small pebbles to cobbles of quartz that range from two to three inches in diameter. A few vesicular lava boulders are a foot or more in diameter. In many exposures the gravel contains water­worn Cretaceous shells. IOOJleed. L. C., and Longnecker, O. M., Jr., 1288a, p. 44, 1932. The Geology of Texas-Cenozoic Systems 773 Fig. 52. Area of the High Plains (Llano Estacado) showing well-known fossil localities in the Panhandle and Tule formations. The arkosic sand is brown, cross-bedded, and contains in its upper portion a little clay. The sand is composed of quartz, feldspar, jasper, magnetite, phlogopite, and minor amounts of rarer minerals. Paleontology and correlation.-The Panhandle formation contains the largest variety of vertebrate remains of any Cenozoic formation in Texas. Fossil-hunting expeditions have explored the wild can­yons of the High Plains since the pioneer trips of Shumard and Marcou. Many have been richly rewarded. The more common and hest-known specimens recorded and the localities where they occurred are presented in the following lists. Fauna253 of the Clarendon beds Pliocyon gidleyi (Matthew) Machaerodus? sp. Teleoceras fossiger (Cope) Protohippus perditus? Leidy Protohippus placidus? Leidy Pliohippus pachyops (Cope) Hipparion cf. H. lenticulare (Cope) Hipparion cf. H. occidentale? (Leidy) Serridentinus productus (Cope) Serridentinus serridens (Cope) Megatylopus gigas M. & C. Camelidea sp. indet. Pliauchaenia sp. Blastomeryx sp. Synthetoceras tricornatum Stirton This fauna, according to Matthew, is lower Pliocene in age and <:orrelates with the upper Snake Creek fauna and the Valentine fauna ·OÍ Nebraska. Fauna254 of the Blanco beds Canimartes cumminsii Cope (l·, 2) Borophagus diversidens Cope (1) Glyptotherium texanum Osborn (1) Megalonyx leptostomus Cope (1) Plesippus simplicidens (Cope) (1, 2) Hipparion phlegon (Hay) (1) Stegomastodon mirificus (Leidy) (1) Rhyncotherium? sp. (1) Platygonus bicalcaratus Cope (1) Platygonus texanus Gidley (1) Leptotylopus percelsus (1) Megatylopus spatula (Cope) (1) Camelids indet. ~Matthew, W. D., MS., 1924. List from Cope and Gidley with some revised identifi.cations by W. D. Matthew (MS. 1924). _o;4List recorded by Cope and Gidley and revised by W. D. Matthew (MS., 1924). The Geology of Texas-Cenozoic Systems 775 Localities recorded in above list­ 1. North side of Crawfish Draw, a small tributary to the south side of Blanco Canyon about 10 miles north of Crosbyton, near R. B. Smith ranch house, now known as the "old rock house," Crosby County. 2. East side of Blanco Canyon due east of Crosbyton, Crosby County. Matthew regarded the fauna of the Blanco beds as middle Plio­cene in age. Fanna of the Hemphill beds Canidae (2, 3) Leptocyon sp. (20) Procyon sp. (28) Borophagus cynoides (Martín ) (20) Aelurodon sp. (24) Hyaenarctos sp. (20) Sthenictis sp. (20) Pseudolaelurus sp. (20) Machaerodus catocopsis Cope (20) Mylagaulus cf. M. mono explain the widespread sheet of gravel of the Pleistocene is floods of water. Remnants of old abandoned stream channels still existing """Measured loy T. L. Bailey (38, p. 102, 1923) . The Geology of Texas-Cenozoic Systems 785 in the late Pleistocene surface indicate that sorne of the late Pleisto­ . cene river channels were more than five times as wide as the present rivers. Barton (70, p. 382, 1930) cites examples of two large ancient rivers in the Trinity and Neches delta plain. The rivers in earlier Pleistocene epochs when the gravel was deposited must have been at flood stage to have transported so much detritus. There is no evidence of any local uplifts during the Pleistocene period along the Balcones fault line or along any of the central Texas structural lines of sufficient magnitude to have furnished gradients steep enough to have brought out widespread sand deposition without greatly increased amounts of water. It seems certain that the floods in the south occurred during the advance and retreat of the ice sheet in the north. The floods were terrific and exceeded even the transportivg power of water flowing out from the melting ice sheet itself. Lithology.-The Lissie formation is made up of ahout ·60 per cent sand, 20 per cent sandy clay, 10 per cent gravel, and 10 per cent clay. The sand and gravel is red, orange, or mottled red and gray on the outcrop and bluish and greenish gray in subsurface sec­tions. In north Texas the gravel occurs in lentils a few inches to 5 feet thick, rarely thicker. In south Texas the lentils of.gravel are thicker, the pebbles are much coarser, and the beds at the surface are cemented by caliche.266 The bedding is irregular, and the texture is variable. The pebbles are composed of chert, quartz, quartzite, pegmatite, granite, porphyries, schists, silicified wood, chalcedony, and water-worn fossils. In central Texas the chert pebbles are largest and most numerous. In most samples at least 90 per cent of the pebbles are chert. Of the remainder, 5 to 6 per cent are white, yellow, and pink quartz, and the rest are chalcedony or igneous rocks. In south Texas the percentage of igneous pebbles increases. The pebbles vary greatly in size in the same exposure and also to a greater extent from one exposure to another. The pebbles average much larger in the outcrops in south Texas than in the sections of east Texas. Most of the pehbles are suhround. --Caliche, according to W. A. Price, is found under 12 inches· of soil in western Hidalgo County aod has been encountered in core tests in the Saxet gas field, Nuéces County, at depths between 85 and 100 feet. This latter occurrence may be the base oí the LiSsie, (Se:e H~ W. Hawker, A study of the soils of Hidalgo County and the stages of their soil accumulation: ::;on Science, vol. 23, No. 6, pp. 475-485, June, 1927, W. A. Prfoe, Reynosa problem of south Texas and origin of. caliche : Amer. Assoc. Pet. Geol., vol. 17, May, 1933.) . The sand varies between red and gray and varies greatly in tex­ture from very fine sand to gravel. Most of the small grains are subangular to angular and average perhaps one-sixteenth of a millimeter in diameter. The composition of a typical sample (Bailey, 38, table 4, 28th from top of list) is shown in the following table: Clay ----------------------------------------------------------------------------------------22% Quartz ------------------------------------------------------------------------------------------63% Chert -------------------------------------------------------------------------------10% Chalcedony -----------------------------------------------------------------------------------3% Feldspar -------------------------------------------·----------·---------------------------------------1o/o Limonite ··-----·---------------------------------------------------------------------------------------· 1o/o Ilmenite ------------------------------·-----------------------------------------------------------frequent Magnetite -------·----------------------·---------------------------------------------------------·ªbundant Hematite -----------------------------·-----------------------------------------------·-------------·common Epidote __ ---· frequenL Tourmaline -----------------------------------------------------------------------------------frequent Zircon -----------------------------------------------------------------------------------------ª bundant Distinguishing characteristics.-The Lissie formation can be dis­tinguished by the following criteria : l. Topography. Tbe outcrop of the Lissie is a nearly featureless plain bounded on the north by a ridge known as the Hockley escarpment. Streams meander broadly across this flat belt in broad, shallow valleys bordered by a slight ridge of sand de­posited as a natural levee. The outcrop of the Goliad and the upper Pliocene sands have more maturely dissected rolling uplands and normal stream profiles. 2. Vegetation. The Lissie supports a more or less open prairie forested in most places by only patches of oak or having fringes of trees along its stream courses. Tbe Goliad and upper Pliocene strata are more heavily forested with post oak and underbrush. 3. Color. Tbe Lissie is distinctly red, orange red, or pinkish buff. Tiie Goliad and upper Citronelle sands are grayish buff and _ have in most places much lighter shades than the Lissie. 4. Texture. The Lissie is finer textured and carries less grave! than the Pliocene strata. Paleontology.-Fossils are rare in the Lissie formation. A few bones have been found, and rare land snails and fragments of plant leaves. In a few wells drilled close to the shoreline marine and brackish-water fossils have been recovered. In general, however, The Geology of Texas-Cenozoic Systems 787 the. Lissie formation is barren ground for the fossil hunter . . The following vertebrales have been identified from the Lissie: Trucifelis fatalis Leidy (7) Equus complicatus Leidy (7) Canis sp. (3) Equus francisci Hay (5) Cistudo marnockii Cope (3) Equus crenidens? Cope (3) Megatherium sp. (2) Equus tau? Owen (3) Bison latifrons ( I-Iarlan) (6) Equus semiplicatus Cope (3) Mastodon serridens Cope (4) Equus excelsus Leidy (3) Glyptodon petaliferus Cope (3) Equus occidentalis? Leidy (3) Elephas columbi Falconer (6) Camelid (3) Elephas primigenius (Blumen-Ox (2) bach ) (3) Tapir (2) Elephas imperator Leidy (6) Localities from which above fossils were collected- l. Two feet above base of grave! al La Loma de la Cruz, Mexic.o, 3 miles east of Rio Grande City, Starr County. 2. Banks of Brazos River; no exact localities recorded. 3. Taranchua Creek, a branch of San Diego Creek, near San Diego, Duval County (erroneously recorded as Nueces County in old reports by Cope). 4. East Texas; no exact locality given by Cope. 5. Shallow well in northern Wharton County, depth 25 feet. 6. Bee County; no exact locality given. 7. I-Iardin County; no exact locality given. BEAUMONT CLAY""" Definition.-The Beaumont clay was named by Rayes and Ken­nedy (692, p. 27, 1903) for the exposures in the vicinity of Beau­mont, Jefferson County. Previously these clays along the Gulf Coast had been referred to as Port Rudson formation by Rilgard268 and Loughridge (1017, pt. 1, p. 680, 1884) and as coast clays by Dumble (478, p. 564, 1894). Rayes and Kennedy (692, pp. 27-29, 1903) defined the Beaumont as the clay deposits between the Colum­bia sands (now Lissie sands) and the overlying Port Rudson silt of recent age. The name has beeri used in the same way by ali later writers. The Beaumont is unique among Cenozoic formations of Texas in maintaining one geologic name during the last three 387LJTERATVRE-Hilgard, E. W ., Summary of results of a late geological reconnaiuau.ce of Louisiana : Am. Jour. ScL, 2nd ser., vol. 48, pp. 332-333. 1869. Loughridge, R. H., 1017, vol. 5, pt. 1, p. 680, 1884. Dumble, E. T., 478, pp. 564-566, 1894; 506, pp. 269-272, 1918. Hayes, C. W., and Kennedy, W .. 692, pp. 27-29, 1903. Fenneman, N. M., 537, pp. 13-16, 1906. Deussen, A., 415, pp. 80-81, 1914; 421, pp. 110-113, 1924. Udden, J. A.• Baker, C. L., and Bose, E., 1652, pp. 94-95, 1916. Trowbridge, A. C., 1610, p. 100, 1923; 1613a, pp. 208-218, 1932. Bailey, T. L., 38, pp. !13-117, 1923. Barton, D. C., 70, pp. 359-382, 1930; 74, pp. 1301-1320. 1930. 9BBHilgard, E. W., Summary of resulta of a late geological reconnaissarlce of Louisiana : Am. Jour. Sci., 2d ser., vo]. 48, pp. 331-346, 1869. decades. Geologists are in general agreement regarding its defini­tion. lt consists of 400 to 900 feet of clay and marl interbedded with lentils of clay between the Lissie formation and surface silts, surface terrace, and alluvial deposits. The type locality is regarded as the shallow well sections in the vicinity of Beaumont. The sur­face soil at Beaumont is terrace material deposited by the waters of Neches River. Beneath these silts the drill encounters 400 feet of clay mixed with a little sand. The section of a well drilled at the Gulf, Colorado and Santa Fe Railroad station at Beaumont is as follows: Depth Recent-Feet Clay and soiL·--···--·----·--------------··-----·-------·-·-----------------··--··-~6 Sand -------------------------------··-·------------··-·----------------·--·-······---·---------~ Beaumont clay- Clay, blue ---·-----··----------------···----·-··--···-·--------------------------------8-45 Sand, containing shells_.______________________________________________________________45-49 Clay, blue, containing thin streaks of sand______··-···--··-··--···-···-49-120 Thickness penetrated ··---·-··-·-·------------·--·----·---112 The Beaumont clay is well exposed in most of the deeper drainage ditches around Houston, Harris County, Beaumont, Jefferson County, and along the hluff of the hay shore at Corpus Christi, Nueces County. Regional geology.-The Beaumont clay occupies a flat, feature­less, treeless coastal plain extending in a belt ahout 40 miles wide about 10 to 15 miles from the coast from Sabine River on the east to Olmos Creek in southern Kleberg County on the south. In the Río Grande valley in Hidalgo and Willacy counties it is covered by recent and wind-blown sand and silt, but it is reached at slight depths in ali wells. lt is essentially a late coastal plain formation that stretches from the Mississippi delta to Tamaulipas Range in northeastern Mexico. Along the Gulf Coast the Beaumont clay is overlain by recent wind-blown river and beach deposits. It dips southeastward and extends beneath heach sand and waters of the Gulf as far as the continental shelf. Its thickness is fairly uniform, ranging from 450 to 900 feet with an average of about 700 feet, as shown in the following table: The Geology of Texas-Cenozoic Systems 789 LOCALITY COU1 TY THICKNESS AUTHORITY Feet Roxana Pet. Co., Seaburn No. 3, Stratton Ridge ----------------Brazoria 930 F. B. Plummer Northwest side of Bryan Heights salt dome --------Brazoria 567 Wm. Kennedy Water well at Chenango ___________ Brazoria 830 Do Water well at Amsterdam__________ Brazoria 822 Do Water well at Thompson, 12 mi. S. of Richmond____________ _ Fort Bend 186 Do Well 1h mi. N. of Markham oil field ------------Matagorda 541 Do Stratigraphy.-The Beaumont clay lies unconformably upon the Lissie formation and is overlain unconformably by stream deposits and wind-blown sands. It has not been subdivided into smaller units. Throughout its extent it is more or less a unit of plastic, poorly bedded, clay interbedded with lentils and more or less con­tinuous layers of sand. Details of its stratigraphy are best illus­trated by the following described section: Section26D o/ the Beaumont clar in a well (jrom 6 to 370 feet) on the V. E. Damstron farm, three-fourth:i o/ a mile north o/ Olivia, Calhoun County. Thickness Feet Clay, mottled, pink and green, calcareous______________________ 24 Clay, light green, calcareous_________________________________ 30 Shell bed, containing fragments of oysters, barnacles, claros (Rangia sp.) ----------------------------------------------------10 Clay, green and pink, calcareous_________________________________ 50 Clay, green and reddish pink, fairly hard calcareous clay______ 20 Clay, pink, hard, calcareous_ ________________________________________ 20 Clay, green, calcareous, medium hard___________________ 40 Clay, blue, noncalcareous, medium hard______________________ 30 Clay, reddish pink, medium hard______ 20 Clay, blue, plastic, medium hard_________________________ 35 Shell bed, containing fragments of oysters and other shells, and thin layers of light brown sand_ _____________________ _______ 20 Clay, pink, calcareous, containing rragments of oyster shells________ 15 Clay, green and pink, calcareous, medium hard________________ 32 Sand, light brown, calcareous, coarse grained__________________ 18 Total thickness measured.__________ __________364 ll!OM~red by Ale:under Deuseen 421, p. 112, 1924. Section210 o/ Beaurnont cfay e.-rcposed on Brazos River near th.e former wagon bridge at Richm.ond, Fort Bend County. Thickness Recent-Feet Sand, grayish red, river sand.: ..... ·-······-····-···············-····-··········-····-···-15 Beaumont clay- Sand, red, with gray patches, and indurated sufficiently to forro a bench ····-···············-···········-···············-····-····-····-···-····--······-···--····· 10 Clay, bluish gray, sandy, containing calcareous nodules, exposed at water's edge ··················-······················-···-··········-·························· 15 -Total thickness measured ..·-··········-····-························-·-40 Sedimentology.-The Beaumont sediments were deposited largely by rivers in the form of natural levees and deltas which coalesced by shifting of the river mouths along the coast, and to a less extent by marine and lagoonal waters in the bays and embayments he­tween stream ridges and delta banks. As the river mouths, and hence the levees and delta levees, shifted, the marine and lagoonal deposits of the interdelta areas were buried heneath the deltaic sediments. The resulting formation is la:rgely deltaic interbedded in places with marine and lagoonal heds. Northward these delta beds are contemporaneous and continuous with the later terraces that occur along all the drainage lines north of the Beaumont clay outcrop. Barton (70, pp. 359-382, 1930) has described admirably the depositional process and points out (74, p. 1309, 1930) that sand was deposited on the terraces and on the crests of the natural levees close to the old stream channels, sandy clays on the flanks, and compact clays in the hlack_bottoms between stream lines. By mapping the sands he has worked out traces of many of the ancient stream lines in the present Beaumont clay surface and found that Beaumont clay soils grade from fine sandy loams on the crests of the ridges into clay loams and from clay loams into clays in the depressions. Near the coast the black clays in places contain marine fossils. A knowledge of the method of deposition of the Beaumont clay, where the ancient ridges, delta hedding, and shifting of stream channels can be ohserved, enables one to understand het­ter the origin of similar Gulf Coast formations of earlier age. l70Mea1ured by William Keooedy, Ceology and oíl proepect1 of the lower Brazos Rher Ta1ley: Unpubliahed manuscript. The Geology of Texas-Cenozoic Systems 791 Much of the sandy clay of the Wilcox, Cockfield, Catahoula, and Lagarto undoubtedly owes its origin to processes of deposition similar to those exhibited in the Beaumont formation. Lithology.-In the northeast Gulf Coast area the Beaumont for­mation consists, according to information derived from well sec­tions, of about 60 per cent clay, 20 per cent silt, and 20 per cent sand. In the central Gulf Coast the formation in sorne sections is 80 per cent to 90 per cent clay. In the Rio Grande valley the pro­portion of sand and gravel appears to be much larger, and the for­mation contains 75 or 80 per cent sand with considerable grave! and sorne limestone originally deposited as caliche. The sands of the Beaumont are light gray or bluish gray, medium to fine grained, and range in size from one-fourth to one-sixteenth of a millimeter in diameter down to minute grains of silt one-sixty-fourth of a milli­meter, with a large part of the sand below one-eighth of a millimeter in diameter. The sand is made up largely of quartz and chert grains together with fragments of recent shells, a small amount of pyrite, and flakes of mica and the usual list of rare, heavy minerals similar to the list given for the Oakville formation. Sorne of the samples from south Texas differ in containing a larger percentage of grains derived from igneous rocks such as red and pink feldspar, rose quartz, granite, and magnetite. The clay is bluish gray, yellowish gray, pinkish gray, purple, and sorne shades of red. It is in most places calcareous in composition and contains calcareous nodules, rarely calcareous concretions, and fragments of more or less decomposed wood. In most places the. clay is highly colloidal, and when wet forms a thick, very sticky mud difficult to traverse with car or wagon in the rainy season. These clays are characterized by their low content of lime and com­paratively high silica content. The analyses undoubtedly represent the nonmarine portion of the Beaumont clay. Other deposits, par­ticularly sorne of those containing oyster beds, have a higher per­centage of lime. The following analyses reported by Ríes ( 1320, p. 241, 1908) show the chemical composition of typical samples of Beaumont clay in Harris County: HOUSTON HARRISBURG CEDAR BAYOU 85.60 Silica (Siü2) ------------------89.0 80.84 Alumina (Alzü ,) -------------3.69 8.09 6.71 Ferric oxide (Fe20 ,) -------------------------1.65 2.25 1.44 Lime (Caü) -----------------0.47 1.44 Tr. Magnesia (Mgü ) ----------------0.65 0.26 0.43 Soda ( 1a2Ü) ---------------------0.06 0.10 0.65 Potash (K20) ---------------Tr. Tr. 0.50 Titanic acid (Ti0 2) ____________ 0.84 0.78 1.00 Water (H2Ü) ----------------1.62 6.00 3.10 Total 97.98 99.76 99.43 Distinguishing characteristics.-The Beaumont clay can be recog­nized by the following criteria: l. Flat, featureless surface. The surface of the Beaumont is a flat, featureless, treeless plain undissected by broad valleys. The streams, except tbe large rivers, flow in narrow channels bordered with sand and silt built up slightly above the plain surface. In all clay formations north of the Beaumont the main streams have bro~d valleys. 2. Soils. The surface soil derived from the Beaumont is typically dark, heavy clay soil, exceedingly sticky when wet and hard when dry and known as the Lake Charles soil. The soil of the Lissie forrnation below and recent silts above are light silt loams. 3. Water holes or pitted prairies. The surface of the Beaumont day has in rnany places small hollows 10 to 15 feet in diarneter, locally known as "blow outs" or "hog wallows." These are srnall spots of poor drainage where a slight excess of alkali pre­vents or hinders growth of grass and weeds. During dry periods the wind removes dust and after a time forros a slight hol­low. Rain water fills the depression and after evaporation leaves the bottom covered with mud cracks and films of dried up alkaline silt which is removed by the next dry wind storm, so that the pits in uncultivated areas are gradually deepened to depths of 20 to 30 inches. The pits occur also on the Lissie plain and other poorly drained areas where clay is the surface formation. They are, however, more common and more char­acteristic of the Beaumont plain. 4. Pimple prairies. Small knolls 10 to 25 feet in diameter and 1 to 4 feet high occur in clusters or belts over the flat surface of the Beaumont plain in certain areas where patches of silt occur. These pimple-like knolls are especially common along the sandy belts produced by minor levees of former temporary streams. The Geology of Texas-Cenozoic Systems 793 They occur also on the Lissie formation and on other silty formations in east Texas and Louisiana. They are especially noticeable, however, on the Beaumont plain, where any slight elevation is noticeable in contrast to the generally featureless surface. These knolls were formed by the action of wind at a time when the soil was not fixed by so heavy a vegetation as at present and are thought to be ancient, small dunes now nearly obliterated by weathering and erosion. They are com· posed of silt and superimposed on an old soil line of clay or hard, silty clay. Veatch and others271 have discussed the origin of these interesting features in much detail. 5. Wood and partly decomposed organic matter. The Beaumont clay contains much organic detritus in the form of cypress logs, rot· ten and partly decomposed tree trunks, peat, and plant detritus of various kinds. N one of this is mineralized or lignitized as is the wood in the older formations. •6. Invertebrate fossils. The Beaumont clay contains in a few places near the coast oyster and clam shells and rarely a shell bed made up of large numbers of Ostrea virginica Gmelin and Rangea cuneata (Gray). Paleontology and correlation.-The Beaumont clay contains few fossils along its outcrop. In a few places brackish-water and marine shells have been found and rarely a bone or tooth of a vertebrate. 'Shells in this formation are likely to belong to one or two species that occur in large numbers. The most conunon is Rangia cuneata '{Gray) , a small smooth-surfaced clam, that occurs, in reefs or banks from 3 to 15 feet thick extending laterally for 30 to 75 feet. Such ·concentrations of shells in piles has been explained as the work of Indians, who undoubtedly lived on the animal. Charred wood, arrow heads and in sorne places lndian bones have been found in the shell heaps. Pearce,272 who has examined them critically, how· ·ever, believes that the piles of shells are not kitchen middens, that they antedated the Indian remains, and served merely as temporary -camp sites. He believes that these shell deposits are simply small "reefs" formed by wave and river action. The shells are deposited ll71Veatch, A. C., 1689, pp. 31()-311, 1905; 1690, pp. 3511-351, 1905; 1691, pp. 55-59, 1906; 1692, pp. 34-36, 1906. Udden, J. A., 1624, pp. 84-103, 1931. The Geology of Texas-Ce'nozoic Systems 799 (1560,pp.217-226, 1890; 1561,pp. 665-701, 1891; 1566,pp. 141­159, 1893). Von Streeruwitz traveled over the country, m.ade many observations and collected large numhers of specimens of minerals and volcanic rocks. His collections were studied by C. A. Osann ( 1161, pp. 123-138, 1893; 1160, pp. 341-346, 1893; 1162, pp. 394456, 1896) , who identified and described the specimens and later made an excursion into the region himself. The next impor­tant contribution to the petrography of the volcanic rocks was made by Lord (1014, pp. 90-95, 1900) who described the rocks in the vi­cinity of San Carlos and Chispa in Culberson and Jeff Davis coun­ties. A few years later Udden (1623, pp. 42-44, 1904; 1626, pp. 70­75, 1907) published brief accounts of the volcanic rocks in the Shaf­ter mining district, Presidio County, and Chisos Mountains in Brew­ster County, and Richardson (1312, pp. 6-7, 1909; 1314, pp. 6-7, 1914), aided by experts in the United States Geological Survey, pub· lished a report on the rocks in the Van Horn and El Paso quad­rangles. In recent years Baker (44, pp. 141-146, 1917; 46, pp. 34­37, 1927; 53, pp. 79-82, 1929), Lonsdale (1007, pp. 256-259, 1927; 1010, pp. 449--450, 1928; 1012, pp. 26-32, 1929), and King (936, pp. 99-103, 1931) have all made important contributions to the knowledge of vulcanism in west Texas. Most of the field work has heen of a reconnaissance character. The area is vast, and the igneous masses are scattered and represent a farge number of types so that much detailed mapping and much painstaking petrographic work: is necessary hefore an authoritative treatise of the geology of the igneous rocks can be undertak~n. This account is merely a summary of what has been written up to this time about the younger volcanic rocks of Texas. Regional geology.--1Igneous rocks of Cenozoic age occur in the Big Bend district of the Trans-Pecos area of west Texas. The prin­cipal outcrops cover the greater portion of Jeff Davis, the south comer of Reeves, the northwest portion of Brewster, and ali the eastern half and portion of the northwestern part of Presidio coun­ties. In addition there are many isolated areas of igneous rock thought to be of Cenozoic age in southern Brewster, southern Cul­berson, and southern El Paso counties. In general igneous rocke -0ccur along the belt of intense folding and faulting characteristic of the Cordilleran structure which crosses the extreme western por­ tion of Texas. Lithology.-The igneous rocks of west Texas occur in a large variety of forms, although the intrusives predominate. Porphyries in the form of dikes, plugs, and sills are common. Laccolithic bosses of granite, syenite, and diorite cover large areas. Extrusions of lava, tu:ffs, agglomerates, and ash are found throughout the area. Associated with the intrusives are minerals formed by the contact of the igneous with the sedimentary beds and metamorphic rocks produced by action of heat on the sediments in contact with the intrusives. Conglomerates, sandstones, and fine-textured pond and lake deposits are interbedded with the lava and ash beds. In sorne places the sedimentary beds contain fresh-water mollusks, plant leaves, ·and mammalian bones that help to establish the geologic age of the deposits. Altogether, west Texas presents a rich variety of igneous, metamorphic, and contact rocks and minerals in such variety of forms and so beautifully exposed as td interest and de­light every petrographer who is so fortunate as to make an excursion through the Big Bend country. The most widespread group of igneous rock is the porphyry. This group includes rhyolite porphyry, granite porphyry, andesite porphyry, trachyte porphyry, basalt porphyry, and syenite porphyry. The rhyolite is a light-colored, pinkish-buff rock made up of phenocrysts of orthoclase feldspar and quartz in an indeterminable ground mass. lt is widespread over the volcanic areas of west Texas in the form of near-surface sills, dikes," and lava flows. The granite porphyry is of similar light color but more distinctly crystalline. It consists of distinct phenocrysts of quartz and feldspar set in a granular ground mass of the same minerals. lt occurs in laccoliths and deep-seated formations. The andesite porphyry is a light-· colored rock consisting of phenocrysts of plagioclase feldspar with no quartz set in an undeterminable ground mass. The rock is less common than the rhyolites and granites. According to Baker,278 it occurs in flows and dikes especially in the area around Chispa Motintain . . The trachyte ·porphyry is similar to the rhyolite but 178]4ker, C. L., Cenozoic igneou1 90Cb of Trana-Pecoa: MS. ~obmitted to Bureau of Economic Gooloin', 1932. The Geology of Texas-Cenozoic Systems 801 contains no quartz. Tlie basalt porphyry is a dark-colored, fine­grained, dense rock containing phenocrysts of plagioclase feldspar in a black, indeterminable ground mass. lt occurs in dikes. The syenite porphyry is similar to the granite porphyry except that it contains no quartz. lt also contains traces of biotite, hornblende, and pyroxene, either as phenocrysts or in the ground mass. The syenites occur as stocks and plugs. They have domed up sedimen­tary rocks and older lavas in a number of places. Diorite intrusives occur in the Diablo Plateau. The diorite is a dark-colored rock composed of phenocrysts of plagioclase feldspar, hornblende, bio­tite, and pyroxene either separately or together in a determinable ground mass of the same minerals. Basalt, next to the porphyries, is most common. lt occurs on the surface as the most recent deposit in sorne places. In others it is interbedded with tuffs, tuff-breccias, agglomerates, and other sedi­ments. The flows range in texture from obsidian through pitch­stone and vitrophyre to porphyritic basalt. Basalt is common in Van Horn.Mountains, in the area south of Wylie Mountains, south of Malone Mountains, in Tierra Vieja Mountains (Rim Rock coun­try), and in the Presidio district. The basalt in west Texas is dark colored, mainly black, and so fine grained that no crystals can be seen with a lense. Sorne of it is cellular or scoriaceous, and in sorne places the cavities contain fillings of zeolites and chlorite. The rock grades into coarse-grained granular porphyries. The most common rock of this type is the olivine-basalt or diabase. In tex­ture it falls between the basalt porphyry and the dense cryptocrys­talline black lava. The tuff occurs in most of the igneous areas. In most places it is interbedded with other sediments or volcanic flows. It is light colored, white, pink, buff, pale brown, or variegated. This tuff is fine grained, light in weight, and has a chalky consistency. lt is, however, less calcareous and more gritty than chalk. Volcanic breccia and agglomerate occur in the Davis Mountains and doubtless in other of the volcanic ridges of west Texas. The breccia in most places is a mixture of rounded volcanic bombs, cobbles, and chunks of lava and fragments of sedimentary rocks held together in a matrix of volcanic mud. 802 The University of Texas Bulletin No. 3232 The occurrence of the different types of igneous rocks is shown in the accompanying table279 (footnotes by author). Types of igneous rocks in west Texas FORM ROCKCOUNTY LOCALITY 11 Lava flow IRhyoliteReeves andBarilla Mts. Jeff Davis Ash bed 'Tuff Big Hill Canyon Dikes !Essexite• East ftanks of Car-Presidio 1 men Range near junction of Mara,. Lava flows Brewster IBasalt villas Creek and Río Grande Lava flo-ws 1Rhyolite and basalt Chinati Mts. Presidio Dikes and sills 1Andesite and syenite Rhyolite Basalt Lava. flows Obsidian Chisos Mts. and Felsite neig hboring Brewster Dacite ranges Dikes and sills Phonolite 1Groruditeb Andesite porp\lyry Syenite porphyry Chispa Mts. (north Dikes and sills ¡Rhyolite of Chispa) Jeff Da vis- Andesite porphyry Lava fl.ows Basalt Cienega Mt . Culberson Brewster Laccolith Granite Nephelite-syenite Eleolite-.syenite Dikes and silla Phonolite Davis Mts. Jeff Davis ' Trachyte Andesite Paisanitec Lava flows Basalt Rhyolite Ash beds Rhyolite Eagle Mt. Hudspeth Lava fl.Ows Basalt Agglomerate and ¡Tuff and tuff breccias breccia beds Finlay Mts. Hudspeth 1 Syenite porphyry Hornblende porphyry Franklin Mts. El Paso Intrusions Laccolith IGranite Hueco tanks, El Paso Dikes syenite porphyryHueco Mts. 1 Iron Mt. north of Brewster Plug ¡syenite porphyry Marathon 1 Laccolith tGranite Mount Ord Range Brewster Dikes Syenite Lava ftows ¡Rhyolite porphyry Tuffs 1 ªEssexite is intermediate between a diorite, gabbro. and ncphe1ile sycnite. It contains labrado· rite, some orthoclase, and in sorne cases nephelite. bGrorudite is a fine-grained porphyry composed of alkali feldspars rich in soda. quartz, aegirite, and sometimes hornblende and mica. cpaisanite is a variety of quart í: porphyry composcd of snda orthoclasc and quartz which 1 phenocrysts of the same minerals. 279Baker, C. L., Cenozoic igneous rocks of Traas-Pecos: MS. submitted to Bureau of Economic : Geology, 1932. The Geology of Texas-Ce1Wzoic Systems 803 LOCALITY COUNTY FORM ROCK Laccolith Granite Syenite Quitman Mts. Hudspeth Intrusives IAplite Augite porphyry La va flows Keratophyre Sa ntia.go Range SiUs Pulaskited Lava fl.ows Rhyolite and trachyte Brewster Sierra Blanca Hudspeth Plugs Phonolite? Sierra Bofecillas P residio La va flows Augite andesite Culberson­¡Diorite Sierra Diablo Laccolith Hudspeth Quartz-diorite lntrusives 1Syenite porphyry Dikes 1Olivine-diabase Presidio­1Nepheline-tephrite0 Tierra Vieja Mts. Jeff Davis Lava flows Quartz-pantellerite' -Rhyolite Latite Presidio- Solitario lntrusions 1Felsite and diabase Brewster Dikes IAndesite Culberson- Va n Horn Mts. ¡Rhyolite Basalt ¡Andesite Hudspeth Lava flows Wylie Mts. 1 Culberson Lava flows Basalt E as t of Santiago Range, south and Plugs IPorphyry1 Brewstersoutheast of Mara- Basic intrusives thon 3outh of Wy!ie Mts. 1 Culberson Plugs 1Syenite porphyry dPulaskite is composed of soda-orthoclase, a subordinate amount of hornblende and biotite, little diopside, nephelite, sodalite, and sorne acccssory minerals. It is a syenite with trachytic tcxture containing a little nephelite. eNepheline tephrite rcsembles basalt but differs in its composition that includes both plagioclase and nepheline. fPantellerite is intermediate in composition betwcen dacite and liparite and is more or less trachytic in texturc. Relationship of igneous rocks and sedimentary strata.-The Ceno­·zoic igneous rocks rest upon Upper Cretaceous strata along the ·eastern escarpment of the central igneous plateau between the north­.eastern Davis Mountains on the north and the southern margin of Green Valley on the south. The underlying Cretaceous strata are thought by Baker280 to be equivalent to the Navarro or possibly somewhat younger (Laramie). The volcanic rocks along the "Rim Rock" area of western Presidio County rest upon the Rattlesnake beds, also of Upper Cretaceous age. Northward along the "Rim Rock," according to Baker, the volcanics overlie successively older Cretaceous sediments. At Chispa Summit, for example, they rest upon the Eagle Ford. Southward from San Carlos Basin the same relationship exists as on the north side. The igneous rocks rest upon the Taylor in the vicinity of Capote Ranch, on the Edwards at Silver R>Baker, C. L., Cenozoic igneous rocks of Trans-Pecos: MS. submitted to tbe Bureau of Eco· nomic Geology, 1932. Dome Mountain, and on the Word formation of Permian age in Pinto Canyon. The volcanic rocks in the northern part of the Trans­Pecos lie upon faulted and eroded Lower Cretaceous rocks. The Cretaceous strata were overthrust toward the northeast, sorne of the folds and faults were peneplained, and igneous rocks poured out from both Sierra Blanca and Eagle Mountain upon the acutely deformed strata. The volcanic rocks are overlain in valleys by sand and gravel thought to be equivalent to sorne of the Pliocene or lower Pleisto­cene deposits of the High Plains. Thus the main body of the igneous rocks of Jeff Davis and Presidio counties appears to be younger than Upper Cretaceous (Navarro) and older than upper Pliocene (late Panhandle). Age of the igneous rocks.-The volcanic rocks are of many types and represent probably a number of different epochs of eruption that may have begun in the late Mesozoic and continued spasmodic­ally through the greater portion of the Cenozoic era. Baker281 points out that volcanic ash and its alteration product bentonite are found in all Gulf Coast sediments from the W oodbine to the Goliad. The Woodbine, Eagle Ford, Navarro, Midway, Carrizo, Yegua, Jack­son, Catahoula, Oakville, Lagarto, and Goliad all contain sorne ash and tuff, but especially the Jackson and Catahoula. Basalts, accord­ing to M. B. Arick,282 are interbedded with lacustral beds in the Rio Grande valley in southern Presidio County. The lake beds are thought to be of Pliocene or Pleistocene age. lt is possible that eruptions in Texas occurred as late as the Quaternary, since late flows are known to have taken place in New Mexico. Since no re­mains of craters or other evidence of very late activity has been found, most geologists are inclined to assign an earlier age to the flows. This is true particularly for the Davis and Barilla Mountains area where the volcanic rocks are gently folded and faulted. Basal tuffs in the Barilla Mountains contain fossil plant leaves which E. W. Berry (104, pp. 1-4, 1919) has identified and correlated with the flora of the Raton and Denver formations of lower Eocene age. The rhyolitic tuffs in Eagle Mountains, Hudspeth County, have yielded bones of late Tertiary land tortoises. A tuff bed on the 2B1Baker, C. L., Cenozoic igneous rocks of Trana-Pecos: MS. suhmitted to the Bureau of Eco· nomic Geology, 1932. :S2Quoted by C. L. Baker, idem. The Geology of Texas-Cenozoic Systems 805 Casey ranch on the nortlieast flank of the Davis Mountains and 11 miles west of Balmorhea yielded also a few land snails resemhling Planorbis and vertehrate bones. The horizon is ahout 200 feet ahove the hase of the volcanic section. The most important specimen was determined by R. A. Stirton283 to be the tooth of a lower or middle Oligocene rhinoceras helonging to the genus Hyracodon. Land snails helonging to the genus Helix have heen collected by Nelson from tuff heds on 02 Ranch located 20 miles southwest of Alpine in the Davis Mountains. These were identified by Junius Hender· son284 and compared by him with similar fossils from either the Puerco or Torrejon formations in New Mexico. Baker285 helieves that the volcanic activity in the southwest por· tion of Trans-Pecos may he somewhat younger than that in the northeast portion of the province. He concludes that the rhyolites, tuffs, and tuff-hreccias of the eastern part of the Trans-Pecos rep­resent the earliest igneous activity. These were succeeded by wide­spread eruptions of syenite-trachytes and phonolites. The syenite porphyries. were the most extensive. Andesite eruptions followed, especially in the area around Chispa and the Big Bend. Latest of all seem to have heen the basalts of Van Horn Mountains, the area south of Wylie Mountains, and in the Presidio country south of Malone Mountains. Basalt porphyries and augite-hasalt porphyries cut other intrusives in Quitman Mountains. Olivine basalt por­phyries cut all older strata and other igneous rocks in the "Rim Rock" area of the Big Bend. With the exception of these important ohservations by Baker, the geologic history of the volcanic rocks of west Texas has not heen worked out in detail. Tertiary geologic history of the Trans-Pecos remains one of the many interesting and complicated prohlems that challenge the enterprise of future geolo­gists and petrographers. Economic resources.-The economic resources of the volcanic rocks of west Texas are the picturesque scenery of its rugged moun­tains, deep canyons, and cactus-adorned slopes, its numerous de­posits of ore-hearing rocks, and its pasture lands. Each year in­creasing numbers of tourists travel into the Big Bend country to IB8Stirton, R. A., ]etter to C. L. Baker. """Quoted by W. S. Adkins, tbio paper, p. 514. 185Baker~ C. L., Cenozoic igneous rocks of Trans-Pecos : MS. submitted the Bureau of Eco­nomic Geology, 1932. enjoy the life in the beautifol resort towns. The ore deposits of the Trans-Pecos country have been known, prospected, and mined more or less actively for fifty years. The principal deposits are silver and mercury minerals. Silver286 has been produced at Shafter in Presidio County for more than fifty years, and has enriched the State by eight to ten millions of dollars. The silver ore is cerargy­rite (silver chloride) associated with galena (lead sulphide), cal­cite, and hematite. The ore occurs in irregular pockets or lodes from a few feet to a hundred feet in length along the contact of igneous intrusions with metamorphosed limestones (Cíbolo) of Per· mían age. Mercury mines287 are in operation near Terlingua in Presidio County, where the ore has been known since 1900. The mercury occurs chiefly in the form of cinnabar in Lower Cretaceous limestone and to a less extent in the Eagle Ford clays of the Upper Cretaceous. The ore is found in fissures, veins, mineralized fault lines, and as underground placer deposits. The lodes are cut by igneous dikes, sills, and faults. All the deposits are in the general vicinity of sorne igneous body. The cinnabar is associated with granular calcite and a pinkish earthy mass of insoluble calcium, aluminum silicate. It is mined, crushed, and refined by roasting in retorts. Lead,288 following silver and mercury, is the third most important metal in west Texas. Lead prospects are located near Altuda and north of Van Horn Mountains in Culberson County, in the Quitman Mountains in Hudspeth County, and in the Chinati Mountains and near Shafter in Presidio County. Mines and prospects from which lead, copper, and silver have been obtained are given in the table on page 808. """L1TERATl'RE-Dumble, E. T., ·459, pp. bvii-bviii, 1891. Udden, J. A., 1623, pp. 32-44, 1904. Phillips, W. B., 1219, pp. 202-203, 1914. 287L1TERATURE-Turner, H. W., 1618, p. 64, 1900; 1619, pp. 265-281, 1906. Hill, Ben F., 722, pp. 1-74, 1902. Moses, A. J., 1143, pp. 253-263, 1903. Phillips, W. B., 1202, pp. 16()-161, 1904; 1208, pp. 155-162, 1905. Hillebrand, W. F., and Schaller, W. T., 831, pp. 25~274, 1907; 832, pp. 1-174, 1909. Udden, J. A., 1648, pp. l-30, 1918. Lonadale, J. T., 1013, pp. 621Hi31, 1929. ~L1TERATURE-Phillip1, W. B., 1203, p. 364, 1904; 1219, pp. 14-15, 1914. Paige, Sidner, 1171, pp. 75-77, l9ll ; 1172, p. 14, 1912. The Geology of Texas-Cenozoic System.s 807 Mineralsº associated with Cenozoic igneous rocks NAME 1 COMPOSITION / LOCALITY COUNTY Agate Si O, 1 Chinati Mts ' Presidio Amethyst SiO, 1 Sierra Blanca Hudspeth Quitman Mts. Hudspeth Amphibole Carrizo Mts. and Cul­ 1 Van Horn Mts. 1 berson Argentite Ag,S 1 Hazel Mine, Sierra Diablo Mts. 1 H udspeth Azurite 2CuC0 3 Cu(OH) , 1 Sierra Diablo Mts. Carrizo Mts. 1 Hudspeth Calomel H g,Cl1 1 Terlingua district 1 Brewster Cassiterite SnO, 1 Quitman Mts. Franklin Mts. 1 Hudspeth and El Paso Cerargyr1te 1 AgCI Ch1sos Mts. Brewster Chalcocite 1 Cu,s Carrizo Mts. HazelMine Hudspeth Chalcopyrite 1 CuFeS, H azel Mine Hudspeth Christophite Quitman Mts. • Hudspeth Chrysocolia 1 CuSi0,,2H20 Sierra Diablo H uclspeth Cinnabar 1 HgS Terlingua Brewster Cuprite 1 Cu,o Boracho Mts. Quitman Mts. Culberson­Jeff Davis Galena 1 PbS Quitman Mts. Carrizo Mts. Mt. Ord Range H udspeth and Brewster Quitman Mts. Hudspeth Gold Carrizo Mts Sierra Blanca Hematite Fe2Ü3 Quitman Mts. Hudspeth 1 Carrizo Mts. 1 Magnetite Fe-JO., 1 Carrizo Mts. 1 Hudspetb Quitman Mts. Sierra Diablo CuCO" H udspeth Sierra Blanca Malachite Cu( OH) , and El Paso 1 Carrizo M ts. 1 Franklin Mts. Rare, north of Van Horn MoS, H udspeth Molybdenite 1 in Sierra Diablo 1 Opa! Si02 (H20) . Van Horn wells Culberson 1 Hunter district in Quitman 1 H udspeth 1 Pitchblende Mts. MnO, Sierra Blanca Hudspeth 1 1 Psilomelane Quitman Mts. Sierra Blanca Mn0 2 Hudspeth 1 Pyrolusite Quitman Mts. 1 Sierra Blanca FeC0 3 Hudspeth Siderite Quitman Mts. Silver, haloids, and Shafter district Ag, etc. Presidio argentiferous galena Chinati Mts. Stromeyerite CuAgS Haz.el mine Hudspeth Tetrahedrite 4Cu2S-Sb2Ss Diablo Mts. Hazel mine Carrizo Mts. Hudspeth Torbernite Cu( U0, )2-(PO,),­BH,O Hunter mine H udspeth Turquoise H(Al,OH) 2-PO, Quitman Mts. H udspeth Wolframite (FeMn )­W0.1 North of El Paso North of Van Horn El Paso and Culberson Quitman Mts. Hudspeth Wulfenite PbMo04 Garlin mine ªAli the mineral& are ore minerale except opal and amethyst, which are ornamental. and agate .. which is ueed for omament. marbles, and mortars. Ali the minerals are contact minerala e:r.cept magnetite, amethyst, and amphibole, which occur in igneoua rocks, and agate. whicb occurs in vugs and eavities in contact rocks. Mines and prospects that have produced lead, copper, zinc, and silver. MINE LOCALITY COUNTY METAL Hazel mine Bonanza mine A1ice Ray mine Sierra Blanca prospect 1 North of Van H orn 1 Culberson 1 Northern part of Quitma~ Mountain 1 Hudspeth 1 Northern part of Quitman Mountain j Hudspeth 1 Intrusive sil!, 1 mi. 1 H udspethSW. of Sierra Blanca Silver, copper, and lead Zinc, copper, silver, lead Zinc, copper, silver, lead Copper Plata Verde prospect Dick Love prospect 1 West foot northern Va n Horn Moun­tains \ W est side of Eagle Mountain 1 Culberson 1 Hudspeth Copper, Silver silver Most of these mines are not worked at present. In favorable years, however, as much as 320 tons of lead valued at more than $28,000 have been obtained. Supplies of building stone, china clay, and underground waters are other outstanding economic resources. The syenites of the Quit­man Mountains, Iron Mountain, and Wylie Mountains are desirable building stones. The rhyolite tuffs in many places are easily cut by saws, they withstand weathering very well, and have attractive colors. The contact metamorphic marbles of the Cienega and Sierra Diablo mountains are also noteworthy. China clay, in the form of ancient hot springs deposits, occurs, according to Baker, in consid­erable quantity north of the Fort Davis-Valentine road, sixteen miles from Fort Davis and also in other places in Trans-Pecos. Under­ground water is found in the bolson deposits of the intermontane valleys. Wells are most productive at the mouths of long draws and where branch valleys approach the outer foothills of the range. Sorne of the commonest ore minerals that are associated with Cenozoic volcanic rocks in west Texas are shown in the table on page 807. The Geology of Texas-Cenozoic Systems 809 ExPLANATIONS OF P LATES VII TO X SOM.E NOTEWORTHY CENOZOIC FOSSILS Life evolved rapidly during the Cenozoic era. The faunas from most of the zones, if studied closely, can be easily distinguished from the faunas of the overlying and underlying zones. Certain fossils, because they are common, because they bave distinctive ornamentation, and because they evolved more rapidly than others, constitute better guide fossils. These are shown on Plates VII to X. The forms illustrated, ali of which were marine in habitat, are only a few of the great number of Texas Cenozoic species selected as ~pecially useful in stratigraphic studies. In addition, the land was occupied by a land and fresh­water flora and fauna. During this era the great mammalian faunas developed, for whereas mammals originated in Mesozoic time they did not become domi­nant until Cenozoic time. Coincident with the development of the mammals was the development of herbage suitahle to the requirements of the herbivorous forms. Limitation of space prevents illustration or description of even the most striking of the Cenozoic mammals, many of which existed in the Texas region. Lists of species of vertebrales will be found under the formations in which they occur. · The foraminifera, minute miscroscopic unicellular animals, are illustrated in Plate VII. These very low forros of life have existed in the oceans from the Cambrian to the present. They developed a multitude of shell forms, and the shape and ornamentation of the shell changed from one epoch to another, so that these minute animals have preved to be of greatest help in identifying formations from well samples, where it is impossible to obtain large fossils. The diversity and complexity of the minute foraminiferal shells are well shown in the plate. A characteristic and very common genus of bivalves, V enericardia, is illus­trated by severa! species on Plate VIII. This group ranges from the lowest Eocene to recent times. The sculpture of the shell consists of radiating ribs that increased in number and complexity of ornamentation as the animal de­veloped. Two main groups of species are recognized, planicostate shells that have wide fiat radials and alticostate shells that have narrow, serrate, and noded ribs. The latter group, which is the easier to differeniiate, is illustrated in the plate. Forms of Volutocorbis, beautiful spindle-shaped snails, are shown on Plate IX. They are slightly less common than the turritellids but equally variant from one zone to another and therefore excellent zone fossils. They are more likely to be found in clay deposits than the turritellids, which liked shallow water and sandy bottoms and limestone reef zones. Species of Turritella, tall turreted gastropods, which range from the Lower Cretaceous to Recent, are illustrated on Plate X. They were common during the Eocene in Texas. The group comprises a series of beautiful, ornamented shells that vacy in details of sculpture from one epoch to another as the animal evolved and adapted itself to changing environments. The nautiloids, best exemplified today by the pearly Nímtilus of the southern seas, were common during the Eocene in Texas. Two genera are represented, Hercoglossa Conrad and Aturia Bronn. The former was especially_ plentiful in the Midway seas, and in places the shells form a nautiloid bed a foot or more thick and traceable for severa! miles. The latter appears to be confined to the Claiborne and later strata. An interesting example of Hercoglossa from the Kerens member of the Wills Point formation in the Midway group is illustrated in figure 53, page 817. Only the commonest and most noteworthy species of these groups of fossils are illustrated. Most of these can be identified by referring to the figures on the plates and to the tables in which the common measurements and charac­teristics of each shell are summarized. PLATE VII SOME CENOZOIC FORAMINIFERA Figures-­ 1. Vaginulina gracilis H. J. Plummer, X 25, holotype from roadside ditch on Commerce-Paris road, 0.7 miles by road northeast of Coromerce, Hunt County. This species is restricted to the Kincaid formation. 2. Vaginulina robusta H. J. Plummer, X 25, holotype from the clay pit in the west edge of Mexia, Limestone County. This species is diagnostic of the Wills Point formation of the Midway group and is especially abundant. in the Mexia clay member. 3. Asterigerina texana (Stadnichenko), X 40, from type locality and from original collection of material made by Miss Julia Gardner at Ever· green Crossing on Elm Creek, 5 miles north of Giddings, Lee County; Crockett formation. a, Dorsal view; b, peripheral view; e, ventral view . . This species is characteristic of the Weéhes and Crockett for· mations of the Claiborne group. 4. Eponides yeguaensis Weinzierl and Applin, X 50, holotype from core at depth of 4015 foet in the Bissonett No. 2, Humble oil field, Harris County. a, Dorsal view; b, ·peripheral view; e, ventral view. This form, especially characterized by its relatively flat dorsal face, is common in the Yegua formatlon of the Claiborne group. 5. Textularia hockleyensis ~ushman and Applin, X 40, from core at depth of 4475 feet in the Renn No. 1, Humble Oil and Refining Compariy (specimen contributed by Miss Alva Ellisor); Fayette formation. This species is characteristic of the McElroy division of the Fayette formation. 6. Nonion whitsettensis (Cushman and Applin), X 40, from core at depth of 1495 feet in the Ruckman No. 1, Adams and Lyle, Karnes County; upper part of Fayette division (specimen contributed by Miss Alva Ellisor). a, Si de view; b, peripheral view. This species, characte_r­ized by its compressed test, its subcircular peripheral outline, and its exceedingly minute spinose apertural face, is diagnostic of that part of the Fayette formation above the McEltoy division. 7. Discorbis cf. D. vilardeboana d'Orbigny, X 50, from core at depth of 4305 feet in the S. Smith No. 74, Humble Oil and Refining Company, Goose Creek oil field, Harris County (specimen contributed by Miss Alva Ellisor). a, Ventral view; b, peripheral view; e, dorsal view. This species characterizes the upper part of the Oligocene section on the salt domes of the southern Gulf Coast. 8. Marginulina cf. M. philippinensis Cushman, X 50, from core at depth of 2593 feet in Lovejoy No. 1, Humble Oil and Refining Company, West Columbia oíl field, Brazoria County (specimen contributed by Miss Alva Ellisor). a, Side view; b, apertura! · view. This species characterizes the lower part of the Oligocene section on the salt domes of the southern Gulf Coast. 9, 10. Heterostegina cf. H. antillea Cushman, from core at depth of 4765 feet in the Harrell No. 4, Humble Oil and Refining Company, Goose Creek oil field ( specimens contributed by Miss Al va Ellisor) . This species is diagnostic of the middle part of the Oligocene section on the salt domes of the southern Gulf Coast. 9. Section through a megalospheric test showing chambers and chamberlets, X 25. 10. Side view of a typical specimen, X .15. The Univeraity ofTexas Bulletin 3232 Plate VII 3 2 4 5 8. 6 ~' 7 j ~ ,J >­ :.. , , 10 9 B The Geology of Texas-Cenozoic Systems 811 IDENTIFICATION TABLE FOR EOCENE SPECIES OF VENERICARDIA Family CARDITIDAE Gill Genus VENERICARDIJA Lamarck PLATE VIII EOCENE SPECIES OF VENERICARDIA Figures­ 1. V enericardia eoa Gardner n. sp. (MS.), X .75, roadside exposure 2 miles northeast of Cedar Grove and 5 miles due north of Cobbs, about one-half mile west of the Kaufman-Van Zandt county line, Kaufman County; Kincaid formation. · 2. Venericardia bulla Dall, X .75, from creek banks 5 miles southwest of Elgin and 2 miles southeast of Littig, Bastrop County; base of Wills Point formation. 3. V enericardia wücoxensis Dall, X .75, Matthews Landing on Alabama River, Alabama; Naheola formation (middle Wills Point) formation. 4. Venericardia smithii Aldrich, X .75, from photographs of Aldrich's cotypes, taken by Miss Julia Gardner (MS.). 5. V enericardia texalana Gardner, X 1.5, roadside exposure 20.7 miles by road east of Nacogdoches on the San Augustine road, Nacogdoches County; Weches formation. 6. V enericardia natchitoches Harris, X 1.5, at side of road 2.3 miles west of San Augustine, San Augustine County; Weches formation. 7. Venericardia rotunda Lea, X 1.5, bank of Colorado River, at bridge in Smithville, Bastrop County; Weches formation. 8. Venericardia flabellum Harris, X 1.5, on Colorado River just north of the bridge in Smithville, Bastrop County; W eches formation. 9. Venericardia flabellum Harris, var. kingi* Plummer n. var., X 1.5, Shipps Ford on Colorado River just. north of the Bastrop-Fayette county line, Bastrop County; Crockett formation. *Named in honor of R. H. King. 3a Z a 4-a 3b 4-b Ga 5 b l b ea 8b The Geology of Texas-Cerwzoic Systems 813 IDENTIFICATION TABLE FOR EOCENE SPECIES OF VOLUTOCORBIS Family VOLUTIDAE Gray Genus PLEJONA Bolton Subsenus VOLUTOCORBIS Dall A, Transverse ribs about equal in height to longit undinal ribs. B, Transverse ribs trruch larger than longitudinal ribs. C. Transverse lines nearly as prominent as longitudinal ribs. D, Five fine transverse ribs. E, First 4 smooth, 5th and 6th ribbed. F, First 3 smooth, 4th and 5th ribbed, others cancellate. PLATE IX EOCENE SPECIES OF VOLUTOCORBIS Figures­ 1, 2. Volutocorbis texana Gardner n. sp. ( MS.) , var. A, X 1.5, 7 miles from Lytton Springs, Caldwell County; Kincaid formation. 3, 4. V olutocorbis texana Gardner n. sp. ( MS.) , var. B, X 1.5, Santa Clara Creek 2 miles south of Marian, Guadalupe County ; Kincaid forma­tion. 5. Volutocorbis texana Gardner n. sp. (MS.), var. C, X 1.5, bank of branch flowing into Tehuacana Creek, 3 miles north of M.exia, Lime­stone County; basal Mexia clay member of Wills Point formation. 6, 7. Volutocorbis limopsis (Conrad), X 1.5, Matthews Landing on Ala­bama River, Alabama; Naheola formation (middle Wills Point). 8. Volutocorbis k erensensis Plummer n. sp., X 1.5, bluff on Trinity River near old Humble pumping station, about 51;2 miles east-northeast of Kerens, Navarro County; Kerens member of Wills Point formation. 9. Volutocorbis rugatus (Conrad), X 1.5, 1 mile west of Oak Hill, Ala­bama; near top of Naheola (upper Wills Point) formation. 10. V olutocorbis safjordi (Gabb) , X 1.2, 1 mil e west of Oak Hill, Ala­bama; near top of Naheola formation ( upper Wills Point). 11. V olutocorbis olssoni PI ummer n. sp., X 1.5, bank of Solomon's Creek about 51;2 miles south-southwest of Elgin, Bastrop County; Seguin formation. 12, 13. Volutocorbis stenzeli Plummer n. sp., X 1.5, from dump at side of old copper prospect, 41;2 miles northeast of Harwood, Caldwell County; Reklaw fonnation. 14, 15. Volutocorbis dalli (Harris), var. smithvillensis Plummer n. var., X 1.5, Colorado River, just north of bridge, Smithville, Bastrop County; W eches formation. 16. Volutocorbis wheelockensis (Cossman) , var. bastropensis Plummer n. var., X 1.5, bank of Colorado River, just north of bridge, Smithville, Bastrop County; Weches formation. 17, 18. Volutocorbis lisbonensis (Aldrich), var. wechesensis Plummer n. var., X 1.5, bank of Colorado River, just north of bridge, Smithville, Bastrop County; Weches formation. 19. Volutocorbis lisbonensis (Aldrich), var. crockettensis Plummer n. var., X 1.5, right bank of Brazos River, at bridge on Highway No. 1 (Moseley's Ferry), Burleson County. 20, 21. Volutocorbis wheelockensis (Cossman), var. sabinensis Plummer n. var., X 1.5, 2 miles west of Columbus, Louisiana, on the Texas side of Sabine River; Crockett formation. 4 5 7 8 9 ~ 10 ~ 11 \'l \7 18 19 zo ZI The Geology of Texas-Cenozoic Systems 815 IDENTIFICATION TABLE FOR EOCENE SPECIES OF TURRITELLA Family TURRITELLIDAE Genus TURRITELLA Lamarck PLATE X EOCENE SPECIES OF TURRITELLA Figures­ 1. Turritella safjordi Gabb, X .75, quarry south of Ola, Kaufman County; Kincaid formation. 2. Turritella ola Plummer n. sp., X .75, quarry south of Ola, Kaufman: County; Kincaid formation. 3. Turritella kincaidensis Plummer n. sp., X .75, quarry south of Ola,. Kaufman County; Kincaid formation. · 3a. Turritella kincaidensis Plummer n. sp., X 3.7, 1A, mile south of the­mouth of Dry Creek on right bank of Colorado River, Bastrop County; Kincaid formation. 4. Turritella levicunea Harris, X 1.5, %• mile downstream from mouth of Dry Creek on right bank of Colorado River, Bastrop County; top­of Kincaid formation. 5. Turritella alabamiensis Whitfield, X .9, Matthews Landing on Alabama: River, Alabama; Naheola formation. a, 12th and 13th whorls, X 3.7_ 6. Turritella cf. T. abrupta Conrad, X 2, Solomon's Creek, 5% miles. south-southwest of Elgin, Bastrop County; Seguin formation. 7. Turritella bellifera Aldrich, X .75, Bells Landing on Alabama River. Alabama; Tuscahoma formation. a, about the 6th and 7th whorls. X 3.7. 8. Turritella mortoni Conrad, X .75, Pendletons Bluff on Sabine River, Sabine County; Sabinetown formation. 9. Turritella sp., X .75, Bells Landing on Alabama River, Alabama; Tus• cahoma formation. a, About the 4th to 6th whorls, X 3.7. 10. Turritella turneri Plummer n. sp., X 1.5, old copper prospect 41h miles northeast of Harwood, Caldwell County; Reklaw formation. a, lOth to 12th whorls, X 3.7. 11. Turritella nasuta Gabb, var. houstonia Harris, X 1.5, 13th to 17tir whorls, roadside exposure 3 miles east of Melrose on the San Augustine road, Nacogdoches County; Weches formation. a, 14th and 15th whorls, X 3.7. 12. Turritella nasuta Gabb, X 1.5, 9th to 17th whorls, right bank of Braws River at bridge on Highway No. 21 (Moseley's Ferry), Burleson County; base of Crockett formation. a, 14th to 16th whorl, X 3.7. Turritella /emina Stenzel, measurements of which are included in the table and whioh is characteristic of the Weches, unfortunately is not shown. It is illustrated, however, in Univ. Texas Bull. 3101, PI. VI, Fig. 14. G 1A ia 8 ?a ' /;, e = ~ r:=; ;::=::; ~ ~ ~ ~ ~ ~ ~ ~ 9a 9 (j8 (d Ja bJ 10 IOa 11 12. 12.a The Geology of Texas-Cenozoic Systems 817 Fig. 53. Hercoglossa vaughani Gardner, X .7. This unusually thick and beautifully preserved specimen of a nautiloid occurs in the uppermost Wills Point formation on Trinity River 5% miles east-northeast of Kerens, Navarro County. (Collected hy Gene Ross.) ,-, ­ Fig. 54. Pal,moxylon sp., X .17, a fossil palm from town of Dime Box, Lee County; Yegua formation. (ldentified hy G. R. Wieland; collected hy H~ C. Fountain; photographed by Joe Barher.) Palm stumps are characteristic of strata of Y egua age. CoNCLUSIONS A vast amount of information has been collected since the first review of the geology of Texas by R. T. Hill (734, pp. 1-95, 1887) forty-five years ago. Hill's bulletin contains references to 110 articles · representing all that has been written on the geology of the State at that time. Now at the end of 1932 the accompanying bibli­ography (Pt. 4 of this publication) carries over 1900 references that concern the geology of Texas. In reviewing all the accumulated information since the pioneer summation by Hill, one is impressed not so much by the bulk of the literature, which is imposing, as by the large number of yet­unanswered questions, unsolved problems, and extent of the still unstudied areas. New undescribed faunas in the Eocene are await­ing treatment. The stratigraphy of the Pliocene strata in southwest Texas needs much more concentrated attention. The Claiborne in southwest Texas requires a large amount of field work to make clear its relationships with the divisions of this group farther northeast. The problem of glacial climates in Texas and the correlation of the southern Pliocene and Pleistocene sediments with the northern de­posits should challenge glaciologists. The igneous rocks of west Texas constitute a virgin field for the enthusiastic petrographer. The undeveloped ore minerals in the western part of the State, the lignites in the central part, and the iron ores in the east should in­trigue many mining engineers. Finally in the broad strefohes of the coastal belt, undiscovered oil pools and domes of salt and sul­phur still exist to attract petroleum geologis'ts for ma'ny years to come. No geologic province having so many and so diverse natliral resources is so little known scientifically as the forests, prairies, and mountains of Texas. The large number of unsolved problems and the extent of the unknown areas make it certain that geologists during the next forty years will discover as many new resources and advance the geologic knowledge of this area as much as in the past equal period. This present account will soon be superseded by more detailed and more complete data. If, meanwhile, this review serves to indicate the unstudied areas and unsettled problems and to inspire others to supply corrections, additions, and new geologic data, then a final and more complete account of the geology of Texas may be written. Part 4 BIBLIOGRAPHY AND SUBJECT INDEX OF TEXAS GEOLOGY E. H. SELLARDS The following bibliography and subject index, containing papera relating to Texas geology through December, 1932, have been pre­pared to accompany Volume 1 of the Geology of Texas. In order to keep the bibliography within reasonable limits it has been necessary to omit publications relating to explorations with only incidental mention of geology, textbooks containing only lirnited reference to Texas, publications issued through daily·or weekly newspapers, and brief references in trade journals. Cornments or contributions by persons other than the author or authors, appearing as inclusions in a listed paper, are not separately entered in the bibliography. Such contributions are, however, cited under the narne of the con­tributor in the subject index which follows the bibliography. Re­views of papers and articles are listed under the publication re­viewed and not under the n~rne of the reviewer. The date of pub­lication given is ordinarily that found on the title page of the pub­lication; however, in sorne cases a second date is added in brackets indicating the year in which the publication is known to have ac­tuall y appeared. An asterisk following an entry indicates that the publication is to be found in sorne one of the libraries at The Uni­versity of Texas. lt has been found necessary, likewise, to restrict the subject index. Thus in paleontologic references it has been necessary to ornit, in the rnain, citation of families, genera, and species, and sorne larger groups. · lt is recognized that both the bibliography and the subject index are necessarily incomplete. Nevertheless, it is believed that both will be found useful in locating the widely disseminated literature on the geology of the State. Among those who, in addition to the geologists of the Bureau Staff, have given valuable help in .the tedious work of assernbling the bibliography and abstracting the publications for the subject index are Miss Josephine Casey, Secretary, and Assistants Velma Morrison, Faye Ricketts, Wayne Wilson, Ralph King, Gilbert Hart, Gene Ross, Leo Hendricks, and M. N. Broughton, to ali of whom the authors of this volurne are greatly indebted. BIBLIOGRAPHY For explanation of abbreviations used in the bibliography and a list of serials cited, see pp. 954-965. LIST OF PAPERS ARRANGED BY AUTHORS Ackers, A. L. l. (and DeChicchia, R., and Smith, R. H.). Hendrick field, Wink­ler County, Texas, Arn. As. Petroleurn G., B. 14:923-944. 12 figs., 1930.* 2. (and DeChicchia, R., and Smith, R. H.). Logs of Winkler pool now valuable, Oil Gas J. 29:30+, il., July 24, 1930.* Adama, George lrving. 3. Oil and gas fields of the western interior and northern Texas coal measures and of the Upper Cretaceous and Tertiary of the western Gulf Coast, U. S. G. S., B. 184:64 pp., maps, 1901. Rv., Eng. M. J. 73 :100-101, 1902. * S. Stratigraphic relations of the red beds to the Carboniferous and Permian in northern Texas, G. Soc. Am., B. 14:191-200, 3 figs., 1903. Absts., Science n. s. 16:1029, 1902; 17:292, 1903.* Sa. (and HiU, B. F.). Gypsum deposits in the United States, U. S. G. S., B. 223:129 pp., maps, 1904.* Adama, H. H. 6. Geological structure of Eastland and Stephens counties, Texas, Am. As. Petroleum G., B. 4:159-167, map, 1920.* Adama, John Emery. 7. Triassic of west Texas (with discussion), Am. As. Petroleum G., B. 13:1045-1055, 2 figs., 1929. Abst., Oil Weekly 53:70, Mar. 22, 1929. Rv., J. Pal. 4:82, 1930.* 8. Origin of oil and its reservoir in Yates pool, Pecos County, Texas, Am. As. Petroleum G., B. 14:705-717, 1 fig., 19EO. Abst., Pan­Am. G. 53 :224--225, 1930. * ·8a. Anhydrite and a.ssociated inclusions in the Permian limestones of west Texas, J. G. 40:30-45, 2 figs.., 1932.* Adams, W. H. 8b. Coals in Mexico-Santa Rosa district, Am. l. M. Eng. 10:270--273, map, 1882.* Adkina, W alter Scott 9, (and Winton, W. M.). Paleontological correlation of the Fred­ericksburg and Washita formations in north Texas, Univ. Tex. B. 1945:128 pp., 6 figs., 22 pls., 1919 [1920).* 10. The Weno and Pawpaw formations of the Texas Comanchean, Univ. Tex. B. 1856:1-172, 13 figs., 11 pls., 1918 [1920].* 11. Geology and mineral resources of McLennan County, Univ. Tex. B. 2340:202 pp., 10 figs., 4 pls. (incl. map), 1923 [1924].• 12. The geology and mineral resources of the Fort Stockton quadrangle, Univ. Tex. B. 2738:166 pp., 8 figs., 6 pls. (incl. map), 1927.* 13. Handbook of Texas Cretaceous fossils, Univ. Tex. B. 2838:385 pp., 37 pls., 1928. * 14. Mineral resources of Texas: Bel! County, Univ. Tex., Bur. Ec. G. (preprint): 16 pp., 1 fig., 1929. Rv., J. Pal. 4:81, 1930.* · 15. Sorne Upper Cretac~Óus Taylor ammonites from Texas, Univ. Tex. B. 2901 :203-211, 2 pls., 1929. • lSa. Geologic map of Bell County, Texas, Univ. Tex., Bur. Ec. G. (in cooperation with Am. As. Petroleum G.), 1930.* 16. (and Arick, M. B.). Geology of Bel! County, Texas, Univ. Tex. B. 3016:92 pp., 2 figs., map, 1930.* 17. New rudistids from the Texas and Mexican Cretaceous, Univ. Tex. B. 3001 :77-100, 1 fig., 6 pls., 1930. • 18. 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Se., J. 11 :4:25---426, 1921.* 600. Basal glauconite and phosphate beds, Science n. s. 56:171-173, 1922.* 60~. Petrography of Ordovician and Mississippian limestone at their contact in Texas (abst.), Pan·Am. G. 44:79, 1925. • 602. Petrography of salt dome cap rock, Am. As. Petroleum G., B. 9: 42-78, 33 figs., 1925; G. salt dome oil fields, 50-86, 33 figs., 1926. • 602a. Features of gypsum-anhydrite salt dome cap rock (absts.), G. Soc. Am., B. 40:99-100, 1929; Pan-Am. G. 51:143, 1929.* 602b. Communication relating to a concretion from the Eagle Ford clay of Texas, Wash. Ac. Se., J. 20:152, 19.::0.* See 162, 696, 1354. Goldschmidt, Víctor 603. (and Mauritz, B.). Ueher Kalomel [crystallography of calomel from Terlingua, Texas], Zs. Kryst. 44:39~, 1908. Goldamith, E. 604. Gadolinite from Llano Co., Texas, Ac. N. Se. Phila., Pr. 1889: 164-165, 1890 .• Goldaton, W. L., Jr. 605. Differentiation and structure of the Glenn formation, Am. As. Petroleum G., B. 6:5-23, 1 fig., 5 pis. 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G. 53:310, 1930. * 935. (and Baker, C. L., and Sellards, E. H.). Erratic boul'ders of large size in the west Texas Carboniferous (ahst.), G. Soc. Am., B. 42 :200, 1931. * 936. The geology of the Glass Mountains, Texas, Part 1, descriptive geology, Univ. Tex. B. 3038:167 pp., 43 figs., 15 pls., map, 1931.* 936a. Pre-Carbonifemus stratigraphy of Marathon uplift, west Texas (with discussion), Am. As. Petroleum G., B. 15:1059-1085, 4 figs., 1931.* 936b. Possible Silurian and Devonian strata in Van Hom region, Texas, Am. As. Petroleum G., B. 16:95-97, 1932.* 936c. Large boulders in Haymond formation of west Texas (absts.), Pan­Am. G. 57:71-72, 1932; G. Soc. Am., B. 43:148, 1932.* 936d. Permian limestone reefs in Van Horn region of Texas (absts.), Pan-Am. G. 57:157-158, 1932; G. Soc. Am., B. 43:280-281, 1932.* 936e. Paleozoic folding in trans-Pecos Texas (abst.), Pan-Am. G. 57: 307. 1932.* 936f. Limestone reefs in the Leonard and Hess formations of trans-Pecos Texas, Am. J. Se. (5) 24:331-354, 4 figs., 1932. * 9'36g. An outline of the structural geology of the United States lnt. G. Cong. 16, Guidebook 28 :57 pp., 1 pl. (map), 1932.* ' See 396b. King, Ralph H. 936h. A Pennsylvanian sponge fauna from Wise County, Texas, Univ. Tex. B. 3201:75-85, 2 pis., 1932 [1933].* King, Robert E. 937. Mississippian and Pennsyl'vanian stratigraphy of trans-Pecos Texas (absts.), G. Soc. Am., B. 40:190-191, 1929; Pan-Am. G. 51:70 1929.* ' ' 938. Faunas and correlation of the Permian of trans-Pecos Texas (abst.), G. Soc. Am., B. 40:247, 1929. * The Geology of Texas-Bibliography 939. Correlation of Pennian of trans-Pecos Texas, Pan-Am. G. 51 :230­231, 1929.* 940. Geology of the Glass Mountains, Part II, Permian fauna of trans­Pecos Texas with description of Brachiopoda, Univ. Tex. B. 3042: 245 pp., 5 figs., 44 pis., 1930 [1931]. * See 930, 932. Kirby, Grady. See 398. Kirk, Morria P. 941. (and Malcolmson, J. W.). A new quicksilver mmmg district [Brewster Co., Tex.], Eng. M. 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Pettus zone fault make it mystery but spots encourage development, Oil Weekly 67:12+, il., Oct. 24, 1932.* Manafield, George Rogers. 1034. The potash field in western Texas, lnd. Eng. Chem. 15:494-497, map, 1923.* 1034a. How the fertilizer minerals of commerce are distributed, Eng. M. J. 123:567-570, April 2, 1927.* 1034b. New potash fields of the United States, The Mining Congress Jour­nal 13:187-188, 1927. * 1034c. American. potash, The Tech Engineering News 9:94+, il., April, 1928.* 1035. (and Lang, W. B.). Government potash exploration in Texas and New Mexico, Am. l. M. Eng., Tr. (Y. Bk.) :241-255, 1929; Tech. Pub. 212:17 pp., 2 figs., 1929. • 1035a. (and Lang, W. B.). [Potash in Texas and New Mexico] (absts.), Eng. M. J. 127:336-337, 345-346, 1929.* 1035b. Potash in the United States, Chemical Education, J. 7:737-761, 1 fig., 8 pls., 1930. • 1035c. (and Bz:oadman, Leona). Nitrate deposits of the United States, U. S. G. 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New specimen of the Pleistocene bear Arctotherium from Texas (abst.), G. Soc. Am., B. 31 :224-225, 1920. * 1070. Blanco and associated fonnations of northem Texas (abst.), G. Soc. Am., B. 36:221-222, 1925.* 1071. A new link in the ancestry of the horse [Pleisippus], Am. Mus. Novitates 131:2 pp., Sept. 23, 1924. Abst., Brit. As., Rp. 92d Meeting:380-381, 1925. • 1072. (and Stirton, R. A.). Osteology and affinities of Borophagus. Cal. Univ., Dp. G. Se., B. 19:171-216, 2 figs., 14 pis., 1930.* 1073. (and Stirton, R. A.). Equidae from the Pliocene of Texas, Cal. Univ., Dp. G. Se., B. 19:349-396, 14 pis., 1930.* 1074. Critica! observations on the phylogeny of the rhinoceroses Cal. Univ., Dp. G. Se., B. 20:1-9, 2 figs., 1931. Absts., Pan-A~. G. 54:236, 1930; G. Soc. Am., B. 42:366-367, 1931.* 1074a. A review of the rhinoceroses with a description of Aphelops ma­terial from the PHocene of Texas, Cal. Univ., Dp. G. Se., B.· 20: 411-480, 12 figs., 19 pis., 1932. * See 20Sc, ll6Sa. Mauritz, B. See 603. Maxwell, R. G. 1074b. Exceptional association of oíl and water in producing zones at Refugio, Texas, Am. As. Petroleum G., B. 15 :953-964, 7 figs., 1931. • The Geology of Texas-Bibliography 895 McCaakey, H. D. 1074c. (and othera). Our mineral supplies, U. S. G. S., B. 666:278 pp., 6 figs., 1 pl., 1919 .• McClellan, George B. See 1055. McCollum, Burton 1075. (and LaRue, Wilton W.). Use of existent wells as an adjunct to seismograph, Oil Weekly 62:29-31+, June 19, 1931.* McCollum, L. F. 1076. (and Cunningham, C. J., and Burford, S. O.). Salt F1at oil field, Caldwell County, Texas, Am. As. Petroleum G., B. 14:1401-. 1423, 7 figs., 1 pl., 1930. Abst., Pan-Am. G. 53:215, 1930.* McCormack, John. See 335a. McCoy, Alex W. 1077. A short sketch of the paleogoography and historical geology of the Mid-Continent oil district and its importance to petroleum goology, Am. As. Petroleum G., B. 5:541-584, il., 1921. * McDermott, Eugene. 1077a. Application of rellection seismograph, Am. As. 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The mineral industries of the United States; sulphur, an example of industrial independence, U. S. Nat. Mus., B. 103 pt. 3:10 pp., 1917. See 1065. Pond, Edward J. . 1240. A Cretaceous river-bed [Hays Co., Tex.], ~cience 9:536-537, 1887.* Pope, Jobn. 1241. Report of exploration of a route for the Pacific railroad near the thirty-~econd parallel of north latitude from the Red River to the Río Grande, U. S., Pacific R. R. Expl. (U. S., 33d Cong., lst sesa., H. Ex. Doc. 129, v. 18, pt. 2 [U. S. Serial No. 737]) : 324 pp., 1855; (U. S., 33d Gong., 2d sess., S. Ex. Doc. 78, v. 13, v. 2 [_lJal. S. Serial No. 760] and H. Ex. Doc. 91, v. ll, v. 2 [U. S. Sen No. 792]) :185 pp., il., 1854.* Pope, George S. . 1242. Analyses of coals purchased by the government dunng *ilie fiscal years 1908-1915, U. S. Bur. Mines, B. ll9:ll8 pp., 1916. Popplewell, Thomas E. . 1242a. Mining methods and costs at the Hart Spur p1t of the Fort "W_orth Sand and Gravel Co. (lnc.), Fort Worth, Tex., U. S. Bur. Mmes, lnf. Cir. 6652:13 pp., 5 figs., 1932.* Porch, E. L., Jr. 1243. The Rustler Springs sulphur deposits, Univ. Tex. B. 1722:71 pp., 1 fig., 9 pls. (incl. map), 1917. * See 1149. Porter, Horace C. 1244. (and Fieldner, A. C.). Weathering of the Pittsburgh coal. bed at the experimental mine near Bruceton, Pa., U. S. Bur. Mmes, Tech. P. 35 :35 pp., 14 figs., 1914. * Ports, P. L. See 1450. Post, Earl S. See 1033a, 1033b, 1223a. Potter, A. D. 1245. (and McKnight, David, Jr.). Tbe clays and the ceramic in­dustries of Texas, Univ. Tex. B. 3120:228 pp., 19 figs., 1931.* 1245a. (and Cunníngham, W. A.). Sulphur, Tbe University of Texas Engineer 1 no. 2:4+, Austin, March, 1931. See 534a. Poulsen, F. E. 1246. Development in east Texas and along the Balcones fault zone, 1929 (with discussion), Am. l . M. Eng., Tr., Petroleum Dev. Tech. 1930:492-500, 1 fig., 1930. Abst., Am. l. M. Eng., Tr. (Y. Bk.): 396, 1930.* Powers, Sidney. 1247. The Butler salt dome, Freestone County, Texas, Am. J. Se. (4) 49:127-142, 2 figs., 1920.* 1248. The Sabine uplift, Louisiana, Am. As. Petroleum G., B. 4:117-136, 2 figs., 1920. * 1249. Solitario uplift, Presidio-Brewster counties, Texas, G. Soc. Am., B. 32 :417-428, 3 figs., 1921; abst., 46-47, 1921.* 1250. (and Hopkina, O. B.). The Brooks, Steen, and Grand Saline salt domes, Smith and Van Zandt counties, Texas, U. S. G. S., B. 736:179-239, 2 figs., 4 pis., 1922.* 1251. Gastropod trails in Pennsylvanian sandstones in Texas, Am. J. Se. (5) 3:101-107, 3 figs., 1922.* 1251a. Reflected buried bilis and their importance in petroleum geology, Ec. G. 17:233-259, 2 figs., 1922.* 1252. Interior salt domes of Texas, Am. As. Petroleum G., B. 10:1-60, 14 figs., 1 pl., 1926; G. salt dome oil fields, 209-268, 14 figs., 1 pi., 1926. * 1253. Buried ridges in west Texas, Am. As. Petroleum G., B. 11:1109­1115, 2 figs., 1927. * 1254. Age of the folding of the Oklahoma Mountains-the Ouachita, Ar­buckle, and Wichita Mountains of Oklahoma and the Llano-Bumet The Geology of Texas-Bibliography and Marathon uplifts of Texas, G. Soc. Am., B. 39:1031-1071, 11 figs., 1928. • 1255. Occurrence of petroleum in North America, Am. l. M. Eng., Tech. Pub. 377 :46 pp., 15 figs., 1931; with discussion, Tr. 1931 :489-533, 15 figs., 1931. Abst., M. Met. sup.:26, Jan., 1931. • See 844. Prather, John K. 1256. On the fossils of the Texas Cretaceous, especially those collected at Austin and Waco, Tex. Ac. Se., Tr. 4 pt. 1 :85-87, 1901.* 1257. A preliminary report on the Austin chalk underlying Waco, Texas, and the adjoining territory, Tex. Ac. Se., Tr. 4 pt. 2:115-122, 1902.• Pratt, Wallace Everett. 1258. Geologic structure and producing areas in north Texas petroleum fields (with discussion), Am. As. Petroleum G., B. 3:44-70, 1919.* 1259. The present excitement [petroleum] at Fort Stockton, Texas, Am. As. Petroleum G., B. 5 :88-S9, 1921. * 1260. A note on supposed evidence of the volcanic origin of Gulf Coast salt domes, Am. As. Petroleum G., B. 5:91-94, 1921.* 1261. A new Gulf Coast salt dome [Fort Bend County, Texas], Am. As. Petroleum G., B. 6:252-254, 1922.• 1262. Oíl at Luling, Caldwell County, Texas, Am. As. Petroleum G., B. 7:182-183, 1923.• 1263. (and Lahee, F. H.). Faulting and petroleum accumulation at Mexia, Texas (with discussion), Am. As. Petroleum G., B. 7: 226--236, 3 figs., 1923; Oil Eng. Fin. 4 no. 82:119-122, 4 figs., 1923.* 1264. Oil and gas in the Texas Panhandle (with discussion), Am. As. Petroleum G., B. 7:237-249, 3 figs., 1923.* 1266. (and Sellards, E. H.). Depression of Goose Creek oil field of Texas (abst.), Pan-Am. G. 45:254, 1926.* 1267. An earthquake in the Panhandle of Texas [July 30, 1925], Seism. Soc. Am., B. 16:146--149, 1 pl., 1926.• 1268. (and Johnson, Douglu W.). Local subsidence of the Goose Creek oil field, J. G. 34:577-590, 7 figs., 1926. • 1269. (and Johnson, Douglas W.). Recent local subsidence of the Gulf Coast of Texas (absts.) , G. Soc. Am., B. 37 :169, 1926; Pan­Am. G. 45:166--167, 1926.* "1270. Two new salt domes in Texas [Moss Bluff and Boggy Creek domes], Am. As. Petroleum G., B. 10:1171-1172, 1926.* 1271. Sorne questions on the cause of the subsidence of the surface in the Goose Creek field, Texas, Am. As. Petroleum G., B. 11 :887­889, 1927.* "1272. Industry must drill 20,000 wells yearly, Oil Gas J. 30:19+, July 16, 19?1.* See 639, 640, 859, 877. Preston, H. L. 1273. San Angelo meteorite [Tom Green Co., Tex.], Am. J. Se. (4) 5: 269-272, il., 1898.• Prettyman, T. M. See 991. Price, William Armstrong. 1274. Gas and oil near Edna, Jackson County, Texas, Am. As. Petroleum G., B. 10:905, 1926. • 1275. (and Palmer, Katherine Van Winkle). A new fauna from the Cook Mountain Eocene near Smithville, Bastrop County, Texas, J. Pal. 2:20--31, 1 fig., 2 pls., 1928. • 1276. Discovery of oil in Saxet gas field, Nueces County, Texas, Am. As. Petroleum G., B. 14:1351, 1930. • 1277. Physiography of Corpus Christi area, Texas, Pan-Am. G. 53:216, 1930. • Ahstract of paper prepared for New Orleans meeting of the American Association of Petroleum Geologists. 1278. Discovery of oil in White Point gas field, San Patricio County, Texas, and history of field, Am. As. Petroleum G., B. 15 :205-210, 1931.* 1278a. Disseminated oil in Pleistocene water sands of Corpus Christi area, Texas, Am. As. Petroleum G., B. 16:385--408, 1 fig., 1932.* 1278b. Reynosa prohlem (ahst.), Pan-Am. G. 57:309, 1932.* See 999a. Pritcbett, Annie H. 1279. Fossil Cephalopoda, descrihed by Hyatt and Cragin, in the museum of Tbe University of Texas, Biol. B. 8:365-366, 1905. Prosaer, Charles Smitb. 1280. Tbe Anthracolitbic or upper Paleozoic rocks of Kansas and related regions, J. G. 18:125-161, 1910.* Prout, H. A. 1281. Description of new species of Bryozoa from Texas and New Mex· ico ... Ac. Se. St. L., Tr. l :228-235, 1858. * Purdue, A. H. 1282. (and Miaer, H. D.). Description of the Hot Springs district, U. S. G. S., G. Atlas, Hot Springs fol. (No. 215) :13 pp., il., maps, 1923.* See 1112, 1114. Quintero, J. A. 1283. The San Saba gold and silver mines, Tbe Texas Almanac, 83-85, 1867.* Ragsdale, G. H. 1284. Evidence of drift at Gainesville, Texas, Geological and Scientific B. l no. 7 :2, 1888. * Ransome, Frederick Leslie. 1284a. The Tertiary orogeny of the North American Cordillera and its prohlems. In Problems of American geology, 287-376, New Haven, Yale University Presa, 1915.* 1284b. Quicksilver, U. S. G. S., Mineral Resources of the United States, 1917, Part I, metals:367--424, 1921. * Ratbbun, Mary Jane. 1285. Two new crabs from the Eocene of Texas, U. S. Nat. Mus., Pr. 73 art. 6:6 pp., 3 pis., 1928. • Rauff, Hermann. 1286. Ueber Porocystis pruniformis Cragin ( =? Araucarites wardi Hill) aus der unieren Kreide in Texas, N. Jb. 1895, I :1-15, il., 1895.* Read, W. T. See 1377. Reed, Lyman C. 1287. Possible evidence of Pleistocene ice action in southeat'>t Texas, Am. J. Se. (5) 15:520--521. 1928.* The Geology of Texas-Bibliography 1288. (and Longnecker, Oacar M., Jr.). A Yegua-Eocene delta in Brazos County, Texas, Univ. Tex. B. 2901 :163-174, 5 figs., 1929.* 1288a. (and Longnecker, Osear M., Jr.). The geology of Hemphill County, Texas, Univ. Tex. B. 3231 :98 pp., 9 figs., map, 1932 [1933.].* Reed, R. D. 1289. Microscopic subsurface work in oil fields of United States, Am. As. Petroleum G., B. 15 :731-754, 1931.* R-ide, John Bernard, Jr. 1290. The fauna of the so-called Dakota formation of northem central Colorado and its equivalent in southeastern Wyoming, U. S. G. S., P. P. 131:199-207, 6 pls., 1923.* 1291. An Acanthoceras rhotomagense fauna in the Cretaceous of the Western Interior, Wash. Ac. Se., J. 17 no. 17:4.53-4.54, 1927.* 1291a. Cephalopods from the lower pa.rt of the Cody shale of Oregon hasin, Wyoming, U. S. G. S., P. P. 150:1-19, 8 pls., 1927. • 1292. The Scaphites, an Upper Cretaceous ammonite group, U. S. G. S., P. P. 150:21-40, 3 pls., 1927. • 1292a. The cephalopods of the Eagle sandstone and related formations in the western interior of the United States, U. S. G. S., P. P. 151: 87 pp., 1 fig., 4S pls., 1927.• 1292b. Two new unionoid pelecypods from the Upper Triassic, Wash. Ac. Se., J. 17:476--478, 1 fig., 1927.* 1293. "Triassic-Jurassic 'red heds' of the Rocky Mountain region": a discussion, J. G. 37:47-63, 1 fig., 1929.* 1294. Exogyra olisiponensis Sharpe and Exogyra costata Say in the Cre­taceous of the Western Interior, U. S. G. S., P. P. 154:267-278, 5 pls., 1929.* 1295. (and Weymoutb, A. Allen). Mollusks from the Aspen shale (Cretaceous) of southwestem Wyoming, U. S. Nat. Mus., Pr. 78 art. 17 :1-24, 4 pis., 1931.* 1295a. The Upper Cretaceous ammonite genus Barroisiceras in the United States, U. S. G. S., P. P. 170:9-29, 8 pis., 1931. * See 394. Reeves, Frank. 1296. Geology of the Ranger oil field, Texas, U. S. G. S., B. 736:111-170, 2 figs., 5 pis., 1922. • Reiter, W. A. 1297. Highest Taylor chalk in Jacksonville, Texas, embayment, Am. As. Petroleum G., B. 14:322--323, 1930.* Renick, B. Coleman. 1298. Recently discovered salt domes in east Texas, Am. As. Petroleum G., B. 12 :527-547, 1 pi., 1928. • 1299. (and Stenzel, H. B.). The stratigraphy and paleontology of the Lower Claiborne along the Brazos River, Texas, Univ. Tex. B. 3101 :73-108, 3 figs., 2 pls., 1931. • See 1086d. Requa, Mark Lawrence. 1300. Petroleum resources of the United States, U. S., 64th Cong., lst sess., S. Doc. 363, v. 42 [U. S. Serial No. 6952] :18 pp., 1916.* Rettger, R. E. 1301. Petroleum development in west Texas and southeast New Mexico (with discussion), Am. l. M. Eng., Tr., Petroleum Dev. Tech. 1930:476--491, 4 figs., 1930. Abst., Am. l. M. Eng., Tr. (Y. Bk.) : 396, 1930.* 1301a. lnterpretation of grain of Texas, Am. As. Petroleum G., B. 16: 486--490, 3 figs., 1932. * 1301b. (and Caraey, J. Ben, and Morero, J. E.). Natural gas in west Texas and southeast New Mexico (abst.), Pan-Am. G. 57: 306, 1932.* See 267. Reynold., Roy A. 1301c. Geological structure map of a part of Throckmorton Co., Texas. Oíl Gas J. 24:80--81, Aug. 20, 1925.* Rice, E.M. See 1600, 1601a, 1601b, 160lc. Richard, Louis M. 1302. Copper deposits in the "Red Beds" of Texas, Ec. G. 10:634-650. 1915. * Richardson, Clifford 1303. (and Wallace, E. C.). Petrnleum from the Beaumont, Texas. field, Soc. Chem. lnd., J. 20:690-693, 1901.* Richardson, George Burr. 1304. Report of a reconnaissance in trans-Pecos Texas north of the Texas and Pacific Railway, Univ. Tex. B. 23 (Min. Sur. Ser., B. 9): 119 pp., il., 1904. * 1305. The stratigraphic sequence in trans-Pecos Texas north of the Texas and Pacific Railway (ahst.), Science n. s. 19 :794-795, 1904. * 1306. Salt, gypsum, and petroleum in trans-Pecos Texas, U. S. G. S., B. 260:573-585, map, 1905.* 1307. Native sulphur in El Paso County, Texas, U. S. G. S., B. 260: 589-592, 1905. * 1308. Tin in the Franklin Mountains, Tex., U. S. G. S., B. 285:146-149, map, 1906.* 1309. The Franklin Mountains, Texas, (absts.), Science n. s. 23:266­267, 1906; 25:768, 1907.* 1310. Paleozoic formations in trans-Pecos Texas, Am. J. Se. (4) 25: 474-484, il., 1908. * 1311. Portland cement materials near El Paso, Tex., U. S. G. S., B. 34.0:411---414, 1908. * 1312. Description of the El Paso district, U. S. G. S., G. Atlas, El Paso fol. (No. 166) :11 pp., il., maps, 1909.* 1313. Stratigraphy of the Upper Carboniferous in west Texas and south­east New Mexico, Am. J. Se. (4) 29:325-337, il., 1910. Abst., Science n. s. 32 :224, 1910. * 1314. Description of the Van Horn quadrangle, U. S. G. S., G. Atlas, Van Horn fol. (No. 194) :9 pp., il., maps, 1914.* See 1637. Richmond, R. W. 1315. "Proration" and its effects in the Y ates pool, Oíl Weekly 56 :58, March 14, 1930. * Riddell, John Leonard. 1316. Observations on the geology of the Trinity country, Texas . . . Am. J. Se. (1) 37:211--217, 1839.* .Ridgway, Robert H. 1317. Sulphur, general information, U. S. Bur. Mines, lnf. Cir. 6329:55 pp., 5 figs., 1930. * The Geology of Texas-Bibliography Riea, Heinricb. 1318. The coa! fields of TP.Xas, Mines and Minerals 26:104-105, 1905. 1319. The clays of Texas, Am. L M. Eng., B. 11 :767-S05, 1906; * Tr. 37: 520-558, 1907. 1320. The clays of Texas, Univ. Tex. B. 102 (Se. Ser. 2 [no. 12)) :316 pp., il., 1908 .• 1320a. Clays, their occurrence, properties, and uses, 490 pp., il., 1906; 2d ed., 554 pp., il., 1908; 3d ed., 613 pp., il., 1927, New York, John Wiley and Sons. • 1321. A peculiar type of clay, Am. J. Se. (4) 44:316-318, il., 1917.* Ritcbie, Kennetb S. 1322. 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The Lacasa area, Ranger district, north-central Texas, U. S. G. S., B. 726 :303-314, 3 figs., 2 pls. (incl. map), 1921. • 1353. (and Miser, Hugh D., and Stephenson, Lloyd W.). Waterlaid volcanic rocks of early Upper Cretaceous age in southwestern Ar· kansas, southeastern Oklahoma and northeastem Texas, U. S. G. S., P. P. 154:175-202, 3 figs., 10 pls. (incl. map), 1929.* 1353a. (and Kerr, Paul F.). The clay minernls and their identity, J. Sed. Petrology 1 :55-64, 1931. • See 1113a. Roth, Robert. 1353b. New information on the base of the Permian in north-central Texas, J. Pal. 5:295, 1931.* . 1353c. Evidence indicating the limits of Triassic in Kansas, Oklahoma, and Texas, J. G. 40:688-725, 6 figs., 1932. • Roundy, P. V. 1354. (and Girty, George ·H., and Goldman, Marcua l.). Missis­sippian formations of San Saha County, Texas, U. S; G. S., P. P. 146:63 pp., 1 fig., 33 pls., 1926.* Row, Charles H. 1354a. An experiment with a drop auger, Am. As. Petroleum G., B. 10: 722-726, 3 figs., 1926 .• 1355. Darst Creek fault, Guadalupe County, Texas, Am. As. Petroleum G., B. 13:1387, 1929.* Ruedemann, Paul 1356. (and Oles, L M.). Helium-Its probable origin and concentra­tion in the Amarillo fold, Texas, Am. As. Petroleum G., B. 13: 799-810, 3 figs., 1929.• Ruedemann, Rudolf. 1357. Coralline algae, Guadalupe Mountains, Am. As. Petroleum G., B. 13:1079-1080, 1 fig., 1929.* Ruflner, E. H. 1358. Geological notes [on the Staked Plains of Texas], U. S. [War Dp.], Chief Eng., An. Rp. 1877 (U. S., 45th Cong., 2d sess., H. Ex. Doc. 1, v. 4 (no. 1, pt. 2, v. 2), pt. 2 [U. S. Serial No. 1796]) App. RR.:1431-1438, 1877 [1878].* Ruaaell, R. D. 1359. Fossil pearls from the Chico formation of Shasta County, California, Am. J. Se. (5) 18:416-428, 12 figs., 1929.* Ryniker, Charlea. 1359a. Schwagerina in Florence flint of Kansas (ahst.), Pan-Am. G. 57: 319, 1932.* Sacha, A. 1360. 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Census, United States Census. 317 Un3. U. S., -Cong., -Sesa., S. Ex. Doc.; H. Ex. Doc.; S. Mise. Doc., United States, -Congress, -session, Senate Executive Docwnent No.-; House of Representatives Executive Document No.-; ~enate Miscellaneous Document No.-. U. S. G. S., B.; An. Rp.; P. P.; W-S. P .; Mon.; Mio. Rea.; G. Atlas; Top. Atlas, United States Geological Survey, Bulletin, 557.3 Un3b; An· nual Report, L557.3 Un3; Professional Paper, L557.3 Un3p Geol. L; Watea-­Supply Paper, 557.3 Un3w; Monograph, L557.3 Un3m; Mineral Resources, 557.3 Un3mi; Geologic Atlas, -folio (No. -), Geol. L. [no call num­ber]; Topographic Atlas, Geol. L. [no call number]. U. S. G. Geog. S. Terr. (Hayden), United States Geologicai! and Geo­graphical Survey of the Territories (Hayden) [title varies]. L557.3 Un3tf. U. S. Nat. Mua., An. Rp.; B.; Pr., United States Naticnal Museum, An­nual Report, 507 Un3r; Bulletin, 507 Un3b; Proceedings, 507 Un3. U. S., Paci6c R. R. Expl., United States [War Department], Pacific Rail­road Explorations (U. S., 33d Congress, lst session, House of Representa­tives Ex. Doc. No. 129 [U. S. Serial Nos. 736-739], vol. 18, pts. 1-4) . Reports of explorations and surveys to ascertain the most practicable and The Geology of Texas-Bibliography 965 economical route for a railroad from the Mississiopi River to the Pacific Ocean, made •.. in 185~ .•• U. S., 33d Congress, 2d session, Senate Ex. Doc. No. 78 [U. S Serial Nos. 758-768] and H. Ex. Doc. 91 [U. S. Serial Nos. 791-801]. U. S. [War Dp.], Cbief Eng., An. Rp., United States [War Department], Chief of Engineers, Annual Report. 353.6 Un3. Univ. Mo. Studies, University of Missouri Studies. Colwnbia, Missouri. 061 MD9ls. Univ. Tex., B.; Min. Sur. Ser., B.; Se. Ser.; Cir.; Bur. Ee. G., The Uni· versity of Texas, Bulletin, [prenumbered and postal numbered, 378.764 UJ Geol. L., from 1915 to date, 1"061 T31] ; Mineral Survey Series, Bul­letin, T557.64 T312m; Scientific Series, 506 T312; Circulars ; Bureau of Economic Geology, T553 T312. Austin. Univ Tex., Bur. Business Res., Pr., The University of Texas, Bureau of Business Research, Proceedings. Austin. Univ. Tex., Sch. G., The University, of Texas, School of Geology. Austin. 560.9764 H555p Geol. L. W. Soc. Eng., J., Western Society of Engineers, Journal. Chicago, ID. 620.6 W525. W. Tex. G. Soc., West Texas Geological Society. San Angelo, Texas. Wagner Free l. Se., Tr., Wagner Free Institute of Science of Philadelphia, Transactions. 560.6 Wl25. Walker Museum. See Chicago University. Wasb. Ae. Se.; J.; Pr., Washington [D. C.] Academy of Sciences, Joumal; Proceedings, 506 W27. West. Eng., Western Engineering. San Francisco, Cal. World's Work. New York. 051 W893. Yale Univ., Col., Yale University, Collections. New Haven, Conn. . Zoological Bulletin. Boston, Mass. L.590.5 Z7b. Za. Ges. Naturw., Zeitschrift für die gesammten Naturwissenschaften. Berlin. Za. Kryat., Zeitschrift für Krystallographie und Mineralogie. ·Leipzig. 548.05 7.37e Physics L. Za. Prak. ·G., Jg., Zeitschrift für praktische Geologie, Jahrgang. Berlin. SUBJECT INDEX In this index, citation is by subjects or publications only, except reviews, discussions, or brief contributions included in other papers. To such publica­tions reference is made under the name of the reviewer or contributor as well as under the subject discussed. For ali other citations by authors, see the preceding bibliography, pages 819 to 965. No attempt has been made to give paleontologic references for genera but only for larger groups, and these have been placed as sub-headings of paleontology arranged under the severa! systems. The numbers refer to entries in the bibliography. For index to this volume, see pages 997 to 1007. Abilene formation. See Permian forma­ tions, Arroyo. Abo formation. See Permian formations. Acme dolomite. See Permian formations, Blaiiie. Adams Branch formation. See Pennsyl­ vanian formations, Graford. Admira! formation. See Permian forma­ tions. agricultura!: 136. 170, 172, 173, 182, 1017 Albany group. See Permian formations. alll:'ae: 406, 633 alga! reefs : 402, 1357 Algonkian system: 396a, 1314, 168lb Alibates dolomite. See Permian forma­ tions, Quartermaster. · alkali Iakes, west Texas : 1086 alkali soils : 655 alluvial deposits: 795, 803, 824, 1378 Alpine, Brewster County, meteorie iron : 1101 Alsate shale. See Ordovician formations. Alta beds. See Permian formations. Alta Vista structure. Bexar County: 1402 altitudes in Texas: 436, 562, 563 alunite: 151, 1733 Amarillo district: 32lb, 616, 625a 670 Amarillo fold : 32lb, 525a, 5Úa, 616, 623, 836, 114lb, 125la, 1288a, 1695a ammonites. See paleontology under sys­tems. Amphibia. See paleontology, Vertebra.ta, under systems. Anacacho formation. See Cretaceous for­ mations. Anadarko basin: 256, 623 analcite: 1010 analyses Alibates dolomite: 1180 alluvium : 1378 anhydrite: 1378 basalt: 1009 clays: 506, 1378 coa!: 53.0, 539, 540, 1242, 1503, 1652 crude mis : · 530, 1500a Beaumont well: 1022 Big Lake, Reagan County: 1500 Luca¿iwell, J efferson County: 1030, 133 Panhandle area: 1500 south Texas: 1499 Soindletop, Jefferson County: 954 Thrall field, Williamson County: 1377 west Texas : 953 dolomite: 1312, 1314, 1378 iron ores : 506, 530 kaolin: 530 lignites: 506, 1015, 1652 manganese : 648 ores: 1378 rocks and minera.Is: 253a, 1378 sand, Tecovas formation : 1180 soils: 656 spring water, Terrell County: 248 sulphur: 1243 water: 42, 50, 260a, 530, 656, 728a, 969, 1086, 1110, 1344b, 1345, 1378 ancestral Rocky :Mountains paleogeograpby: 1385b, 1694 stratigrapby : 1254 Anderson County: 244, 267a, 415, 461, 470, 506, 525a, 654, 665b, 668a, 843, 957, 958, 992a, 1080b, 1215, 1232, 1252, 1270, 1298, 1553, 1844a Andrews County: 56b, 190a, 1671, 1847 Angelina County: lOOa, 356b, 356c, 382b, 415, 470, 506, 569, 905, 1219, 1844a anhydrite: 1635 analyses: 1378 cycles: 50, QZ mineralogical notes : 1366a occurrence: 1, 8, 8a, 612, 1662, 1663 Annona formation. See Cretaceous for­ mations. Antelope Creek. See Pennsylvanian for­ mations, Strawn. Anthozoa (corals). See paleontology un­ der systems. Anthracolithic: 44, 91, 1280, 1652 anticlinal theory: 1648 anticlines: 40 Apache formation. See Permian forma­ tions. Apache :Mountains: 1162, 1314 Appalachian M.ountains, former exten­ sion: 145b Aransas County : 421, 952, 1841a Arapahoe formation. See Eocene forma­ tions. Arbuckle :Mountains, age of folding : 1254 Archean: 458, 671, 1681b archeology geological evidence: 284, 286 paleontological evidence: 283, 284 Pleistocene: 282, 1455 Archeozoic rocks : 1652 Archer County: 58b, 83a, 98, 208e, 247, 573, 854, 967a, 1145a, 1219, 1258, 1343, 1351, 1492, 1572, 1605, 1606b, 1742, 1745b, 1748, 184la, 1844a areas: 436 arid regions, rock fans: 877a Arkansas: 18, 392, 753. 788, 1046, 1112, 1114, 1115, 1282, 1691 Armstrong County: 42, 471, 1399, 1639, 1841a Arroyo formation. See Perm"ian forma­tions. artesian water: 454, 609, 690. 959 1336 Central Basin formations: 458 ' Gulf Coast slope : 1488 northeast Texas: 609, 803 The Geology of Texas-Subject Jndex artesian water--eontinued southwestern Texas: 414, 609, 1013d Travis County: 1462 west Texas : 780a artifacts: 282, 1444d Aspermont dolomite. See Permian for­mations, Blaine. asphalt: 455, 654, 1112, 1185a, 1200, 120G, 1219 Anacacho formation: 49 analyses : 1378 Medina County: 992 occurrence: 49, 654, 992, 1018b, 1199. 1200, 1206, 1652, 1685, 1836 asphaltum, grahamite: 469, 475, 1836 assays, Trans-Pecos ores: 1201 Atascosa County : llla, lllb, 421, 470. 510, 668a, 677, 1009, 1013b, 1013e, 1013d, 1219, 1407, 1488, 1841a Austin County: 32, 46a. 143b, 382b, 421, 842, 1025a. 1841b Austin formation. See Cretaceous forma­tions. Austin. Travis County chemical analyses of rocks of: 515 dam on Colorado River at : 798, 1592a, 1594 geology of area: 795, 808 Lake Austin silting: 1595 soil survey : 1844a structural materials : 179 tornado: 1486b water: 529, 1462 Avis sandstone. See Pennsylvanian for­ mations, Thrifty. Bailey C<>unty: 42, 56b. 471, 1086 Bailev, Thomas L.: 188 baked shale : 1O11 Balcones fault zone: 11, 49, 146b, 164, 267a, 384. 525a, 543, 544, ~17, 671P . 808. 826 . . 889a, 992, 992a, 999, 1009. 1018a, 1223a. 1246, 1326. 1401, 1402, 1404, 1433, 1441, 1651, 1652, 1695a, 1709a Balsora limestone. See Pennsylvanian formations, Graford. Bandera County: 240, 398, 683, 636, 977, 1009, 1841a Barbers Hill salt dome, Chambers Coun­ty : 32. 113, 898a, 1146, 1596b, 184lh Barinqer Hill. Burnet County : 59, 77. 84a. 710, 711, 716, 717, 718, 719, 7·20. 721, 828, 947a, 974a, 1368a barite: 62, 1126, 1127, 1810 Barnett formation. See Mississippian formations. Barrilla Mountains: 44, 104. Barton Creek. Travis County: 929 Barton Creek limestone. See Pennsyl­ vanian formations. Garner. basal clays, strati«raphy : 458 basalt, analyses :' 1009, 1160 basement rocks, Pecos County oil wells : 882 Basement sands. See Cretaceous forma­tions. Basin RaTige. Guadalupe Mountains : 919 Bassett, H P.: 1066 Bastroo County: 57a. 267a. 268. 413, 421, 456. 470. 544. 664a, 668a. 899b, 1009, 1219. 1238b, 1275, 1320a, 1422, 1442, 1488. 1687a, J844a Batson oil field, Hardin County: 62, 1365 bauxite: 1185a Baylor County: 247, 572b. 669a, 1082. 1156, 1742, 1745b, 1748, 1749c, 1752. 1769. 1853 Baylor Mountains : 936c Beach Mountain, Van Horn quadrangle: 1107a, 1314 Bead Mountain limestone. See Permian formations, Belle Plains. Beaumont, J efferson County, oil field: 3, 67. 250, 490, 804, 806, 811, 1022, 1197, 1303 Beaumont formation. See Pleistocene formations. Beaumont oil field : 3, 811 Beaverhurk limestone. See Permian for­mations, Belle Plains. Bee County: 40, 97, 145, 421 , 678a, 896c, 1033b, 1596a, 184la Beede, J. W.: 592 Belknap limest.one. See Pennsylvanian formations. Harpersville. Bel! County: 14, 15a, 16, 18, 373, 421, 515, 682, 803, 1119a, 1219, 1674, 160lc, 1841a, 1844a, 1853 Belle City formation. See Pennsylvanian formations. Belle P!ains formation. See Permian for­ mations. bench márks: 1056b, 1055c Bend arch: 140, 20la, 244a. 245a. 249e, r~;:;. 549. 990, 1151. 1693, 1695. Bend group. See Pennsylvanian forma­tions. Benton formation. See Cretaceous for­mations. bent;'~~1: : 1, 16lb, 1113a, 1185a, 1378a. Bethany church fault: 164 Bethany gas pool : 860 Bethel dome, Anderson County : 992a Bexar County: 3, 76b, 421, 610, 513b, 515, 544, 681, 795, 888, 889a, 896b, 1009, 1086c, 1113a, 1145, 1219, 1320a, 1378a, 1401, 1402, 1404, 1407, 1477, 1529, 1579, 1838a, 1841a, 1844a bibliography: 144, 1382, 1476, 1843, 1484, 1716c, 1716d, 1716e, 1716f, 1724, 1758, 1833e Big Bend region. See also Trans-Pecos Texas: 807, 1080a, 1456, 1597 Big Creek salt dome, Fort Bend Coun­ ty: 1261 Big Hill salt dome, Jefferson County: 705 Big Hill salt dome, Matagorda County: 645, 1795, 1796 Big Lake oil field, Reagan County : 269, 510d, 525a, 653, 706, 880a, 895, 1020, 1020a, 1021, 130lb, 1322, 1414, 1421, 1425, 1428, 1841c analyses of crude oil: 1500 engineering problems : 269 Foraminifera: 510d geothermal gradients : 694 oil and gas development: 706, l 700a oil and gas production : 1322 producing horizons : 1021, 1428 Silurian stratigraphy: 1017, 1019 stratigraphy: 706, 1021, 1444c structure : 706, 1020, 1414, 1444e subsurface geology: 1414 sulphide poisoning: 1813 type Jog: 706 "Big Lime." See Permian formations. Big Spring, Howard County, under­ground waters: 674 Big Valley bed. See Pennsylvanian for­mations, Strawn. Bigford formation. See Eocene forma­tions. bismuth, north Texas : 171 968 The University of Texas Bulletin No. 3232 Bissett formation. See Permian forma· tions. bitumen in asphalt rocks : 664 Blach Ranch limestone. See Pennsylva­ nian formations, Thrüty. "Black Lime" formation. See Pennsyl­vanian formations. Black and Grand Prairies : 803, 1789, 1790 Black Prairie ·region, roade : 750 Blaine formatiOn. See Permian forma­ tions. Blanco Canyon: 340, 342 Blanco County: 274, 891, 164la, 1727a, 184la Blanco formation. See Pliocene forma­tions. blast fumace locations, east Texas: 1216a Bliss sandstone. See Cambrian forma­ tions. Blossom formation. See Cretaceous for­ mations. Blowout Mountain sandetone. See Per­ mian formations, San Angelo. Blue Ridge salt dome, Fort Be:o.d Coun­ty: 32, 638 Bluff Bone bed. See Permian formations, Belle Plains. Bluff Creek shale. See Pennsylvanian formations, Graham. Bluff meteorite, Bandera County: 240 Boggy Creek salt dome, Anderson and Cherokee counties: 267a, 1080b, 1270, 1298, 1553 bolson deposite: 1312, 1314 bolson plains: 1605b Boone Creek limestone. See Pennsylva­ . nian formations, Graford. Boone formation. See Misaissippian for­mations. · Bone Springs member. See Permian for­ mations. Bonham formation. See Cretaceous for­ mations. Boquillas tlags. See Cretaceous forma­ tionÍI. Bordas escarpment: 1613a Borden County: 471, 1619a borings Colorado County: 38 Cooke County: 675 Dickens County : 1636 Galveston: 472, 473, 778 Lytton· Springs oíl field: 188 Midland County: 1418 northem Texas: 1449 northwestern Texas: 1639 Palo Pinto County: 699 Panola County: 1408 potash borings: 1418 Potter County: 1180 Travis Cóunty: 1462 Webb and Zapata counties: 1406 Bosque area, Cretaceous formations: 1674 Bosq~e44~ounty: 10, 263, 546, 671a, 803, Bosque escarpmerit: 11 Bosque formation. See CretsceoUJI for­ mations. J;::~d':,;. Rio Grande Valley : 1163 Brazos River : 1287 Carboniferous : 66a, 82, 935 boundaries : 436 Cretaceous-Jurassic: 791 dispute, Red River valley: 595, 824, 1410, 1410&, 1411, 1597 northwest: 56b survey, M.exican boundary: 526, 643, 1043, 1177, 1178, 1380, 1381 Bowie County: 470, 609, 840, 1186a, 1219, 1232, 1320a, 15llc. 184la, 1844a Bowie, M.ontague County, coal mine: 1823a · Brachiopoda. See paleontology under sys­tems. Brad formation. See Pennsylvanian for­ mations. Brannon limestone. See Pennsylvanian formations, Millsap Lake. Brazoria County: 32< 33, 46a, 61, 113, 114, 196, 415, 418, 421, 522, 897a, 913, 952, 1219, 1488, 1596b, 1650, 184la, 184lb, 1844a Brazos County : 58, llla. 184, 185a, 186b, 185e, 186d, 415, 470, 471, 506, 668a, 906, 1219, 1288, 1488, 184la, 1844a Brazos coa! field, Palo Pinto County : 36 Brazos River : 69a, 387a, 1595a delta: 70 geology west of: 421 lignitic stste: 664 meteorite from: 1464 paleontology :· 679, 1811 profile: 1848 (44) valley, stratiiraphy, Tertiary : 1299 Brazos sandstone. See Pennsylvanian formations, Garner. Breckenridge limestone. See Pennsylva­ nian formations. Thrifty. Brenham gas field : 552 Brenham salt dome, Washington County: 842 Brewer pool: 6 Brewster County : 15, 44, 47, 130, 131, 133, 179; 194, 259a. 396b, 411, 428, 492, 512, 603, 672, 722, 723, 725, 807. 808, 830, 831, 845, 936a, 936c, ·941, 942, 988, 990, 1006, 1010, 1013, 1035c, 1080a, 1101, 1143, 1202, 1204, 1206, 1207, 1208, 1209, 1210, 1211, 1216c, 1249, 1284b, 1860, 1362, 1362&, 1868, 1368b, 1442, 1444b, 1604, 1626, 1628, 1643, 1645, 1647. 1648, 1660, 1664, 1695b, 1753&, 176ld, 1846 (02) (05) (06) (07) (09) (10) (17) Brewster formation. See Cambrian for­ mations. Bridgeport coa!. See Pennsylvanian for­ mations, Graford. · Bridgeport, Wise County: 132 brines: 1066 briquetting of lignite : 1218 Bris.coe County: 42, 22lb, 471, 689a, 1614, 1615, 184la Brooks County: 421, 161Sa, 1660, 184la Brooks salt dome, Smitb County: 244, 1250, 1262 brown coa!. See lignite. Brown County: 82, 342, 364, 369, 1180, 449, 610!, 661, 803, 856c, 1216, 1219, 1227, 1228, 1258, 1353b, 1408, 1654, 1660, 1673, 1701, 1727b, 1727c, 1853 Brown Creek. See Pennsylvanian forma.­ tions, Stra.wn. Brown~ L. S. : 71 Brownstown formation. See Cretsceous formations. Browna:!ille area, Cameron County, aoil survey: 1844a Brownwood shale. See Pennsylvanianformations, Graford. Brucks, E. W . . : 164, 165 The Geology of Texas-Subject Index Bryan Heights salt dome, Brazoria Coun­ ty: 913 Bryozoa. See paleontololO' under syatems. Bryson oil field, .Jack County: 141a · Buchana.n oil field : 1444a. Buda formation. See Creta.ceous forma.. tions. Buffalo Creek. See Pennsylvanian for­ mations, Straw.IL Buffa.lo Hill sandstone. See Permia.n for­ mations, Vale. building material : 142, 179, 22lb, 271, 274, 339, 340, 341, 342, 399, 412, 412b, 412.d, 413, 464, 459, 461, 472, 513b, 515, 709, 766, 808, 907' 992, 996, 107 4c, 1092, 1172, 1188, 1189, 1209a, 1219, 1246, 1311, 1319, 1320, 1321, 1426, 1448, 1665, 1678, 1688, 1610, 1652, 1839, 1840 Bulcher field, Cooke County : 675 Bull Creek. See Pennsylvanian forma­ tions, Strawn. Bullard dome, Smith County: 992a Bullwagon formation. See Permian for· mations, Vale. Bulverde Cave, Bexar County: 681 Bunger limestone. See Pennsylvanian formations, Graham. Buresu of Economic Geology : 982a., 1417, 1646, 1666 Burkburnett field : 594­buried ridges importance in petroleum geology : 1251a. Pa.nhandle: 1264 west Texas: 1263 Burleson County: 16lb, 413, 415, 421, 470, 668a, 682, 1219, 1488, 1687& Burnet County : 84a, 138a, 274, 592, 654, 710, 711, 803, 947a, 974a, 1148, 1172, 1203, 1219, 1470, 1471, 1481, 1525c, 1568, 1567a, 1574, 164la., 1650, 1673, 1674b, 1703a, 1703e, 1704, 1727a, 1841a, 1846 (19) Burnt Branch. See Pennsylvanian for­ ma.tions, Strawn. Butler salt dome, Freestone County: 244, 567, 1247, 1252 Caballos nova.culite. See Devonian for­ mations. Caddell clay. See Eocene formations. Caddo Creek formation. See Pennsylva­ nian formations. Caddo oil and gas field, Harrison Coun­ ty: 1059 calcite: 612, 1362 Caldwell County: Sla, 69b, 76b, 164, 165, 165a, 188, 267, 267a, 378, 421, 470, 526a., 644, 64'i'a, 664a, 697, 728a, P~F."'· V~2•. 1009 1075. 1076 1186a, 1223&, 1288b, 1262, 1409, 1412, 1442, 1716, 1838a, 1841a, 1844a. Calhoun County: 421, 1477, 1624, 184la caliche : 673a Callaban County: 82, 247, 510f, 728, 967a, 1227, 1228, 1268, 1403, 1673, 1699, 1727b, 1753a Callaban divide: 92 Callisburg a.rea: 189 Cambrian algal reefs : 402 Central Basin formations : 458 correlation: 618a, 879, 1470, 1674b, 1703 formations Blia.s sandstone: 1312, 1662 Brewster: 936a, 1652 Cap Mountain : 1652, l 695b Dagger Flat sandstone: 936a Hickory sandstone: 1695b Van Horn sa.ndstone : 46, 1314, 1662 Wilberns: 402, 1652, 1695b greensand : 546d map : 1440 microscopic cha.racteristics: 1656 nomenclature: l 703f pa.leogeogra.phy: 1382b, 1382g, 176lc paleontology: 402, 1702a, 1703a, 1703f Brachiopoda : 1304, 1382, 1465, 1702b, 1703a, 1708b, 1703d, 1703e, 1703f, 1703g Llano region : 1172 Marathon region : 44 Trilobita. : 1703f stratigra.phy central Texas : 173, 271, 274, 468, 879, 891,. 1172, 167 4b, 1696b, 1702, 1703, 1761d Trans-Pecos Texas: 46, 936a, 986g, 1312, 1314, 1696b, 176ld Cambro-Ordovician correlation : 618a, 879, 167 4b Ellenburger formation correlation : 386b, 618a. maps: 676, 1408 microscopic characteristics: 601, 1666, 1669 paleontology: 1330, 1471 petrology : 1354 stratigraphy: 16, 891 Central Mineral region: 271, 274, 468, 879, 1172, 1471 north-central Texa.s: 6, 245a, 247, 641, 1021, 1064, 1296, 1403 water of: 549 Cameron County : 962, 1613a, 18'4a Camp Bowie: 1453 Camp Colora.do limestone. See Pennsyl­ vanian formations, Pueblo. Camp County : 1232, 184la, 18441!­Camp Cteek shale. See Pennsylvanian formations, Pueblo. Cana.dian River valley: 769, 1182 Caney formation. See Pennsylvanian for­mations. cannel coal. See coa!. Canyon group. See Pennsylvanian for.. mations. Cap Mounta.in formation. See Ca.mbria.n formations. cap rock Damon Mound: 114 minerals: 61, 163 origin of: 1344 petrogra.phy : 71, 162, 163, 602, 602a salt domes: 71, 602 Ca.pitan formation. See Permian forma­ tions. Capps limestone. See Pennsylva.nian for­ mations, Strawn. Caprina limestone. See Creta.ceous for­ . mations. carbon ratios, Pennsylvanian coals: 648 Carboniferous. See also Mississippian, Pennsylvanian, and Permian : 131, 338, 928, 1042, 1313, 1683, 1652, 1677b Central Ba.sin formations : 458 Colora.do coa1 field region : 449 Creta.ceous conta.ct: 1005 El Paso quadra.ngle: 1312 paleontology: 656, 693a, 1006, 1330, 1428, 1456 bibliographic index, invertebrates: 1724 Brachiopoda: 1041, 1465 Bryowa: 1281 970 The University of Texas Bulletin No. 3232 Carboniferous-continued paleontology-continued Cephalopoda: 335, 560, 698, 863, 864, 1234e, 1396, 1397, 1496 Foraminifera: 367, 561, 1601 Gastropoda: 1465 Mollusca: 589a, 1041 Ostracoda : 408 Vertebrata: 219 (and) Permian, stratigraphy of red beds: 5 sediments, Mid-Continent oil fields : 246 stratigraphy: 620, 1042 central Texas: 339, 1582, 1583 homogeny: 914 north-central Texas: 132, 172, 620 Trans-Pecos Texas: 932 terminology : 923 Van Horn quadrangle: 1314 west Texas: 1313 erratic boulders: 56a, 935 Carey Lake dome: 992a Carlsbad Cavern: 396b Carlsbad formation. See Permian forma­ tions. Carolina.-Texas oil field: 1613a Carrizo formation. See Eocene forma­tions. . Carrizo Mountain formation. See pre­Cambrian formations. Carrizo Mountains: 1314 Carson County : 42, 78, 410b, 525a, 854b, 1264, 1639, 1775a, 1841a casinghead gasoline: 1846 (17) (18) Cass County: 180, 609, 903, 905, 1186a, 1219, 1232 Castile formation. See Permian forma­tions. Castro County: 42, 471, 184la Catahoula formation. See O!igocene for­ mations. catalogue contributions to N orth American geol­ ogy: 392b Cretaceous paleontology: 555 Mesozoic Invertebrata: 144 Cave Creek formation. See Permian for­mations. cavern deposita bat guano: 1196 Permian in west Texas: . 1660 Cedarton shale. See Pennsylvanian for­ mations, Brad. Cedar Hills formation. See Permian for­ mations. Cedartop formation. See Permian for­ mations. celestite: 16lc, 712, 956 cement: 412b, 513b, 515, 1074c, 1219, 1245, 1311, 1378a, 1402, 1578, 1652 cementing oil wells: 1760 Cenomanian: 134, 15lla Cen_ozoie. See also individual systems. h1story, Texas Plains: 54 paleobotany, catalogue: 949 paleontology: 253, 306, 313, 314, 381, 950, 1031, 1165a realm: 299 stratigraphy : 4 7 8 Bel! County: 16 Blanco Canyon: 340, 342 salt domes: 1111, 1250 McLennan County: 11 Panhandle: 615 Staked Plains : 305 west Texas: 305, 841 Central Basin formations: 458. Central Mineral region. See also central Texas: 271, 274, 458, 874b, 1652 natural resources: 1170, 1171 Central Mineral region-continued building materials: 271, 274, 472, 1172 greensand: 546d minerals: 138a, 271, 274, 472, 574, 604, 715, 717, 718, 719, 721, 828, 947a, 1029, 1172 graphite: 450, 1172 iron: 1172 lead: 1203 metals: 271, 274, 472 rare earth : 1172 tin: 273, 275, 276, 1347 water supp]y: 1172 pa!eogeography: 1172 physiography: 413a, 1172, 1328 porphyry, quartz-feldspar: 868 stratigraphy: 116a, 271, 274, 1005, 1170, 1171, 1172, 130la, 1330, 1471, 1525c, 1567a, 168lb, 1682, 1682&, 1695b, 1702, 1761a, l 76ld, 1814a structure: 140, 271, 274, 1172, 1254 central Texas Balcones fault zone : 1441 Carboniferous area: 1582, 1583 coa! fields : 339 drainage: 1581 igneous rocks: 736, 757 natural resources building materials: 179, 339, 766, 996, 1448 clays: 1319 coa!: 339, 1584 copper: 172 gold: 172 ichthyol: 1846 (19) iron ores: 169, 170, 172, 1212, 164la kaolin: 530 1ea:d: 112 manganese: 1190 minerals: 169, 170, 172, 173, 273, 275, 276, 530, 648, 712, 996, 1190, 1846 (03) (04) (07) (08) (09) (10) (12) (13) (18) (83) (84) (87) (89) (90) mineral springs : 997 oil and gas: 339, 967a, 992a, 1064, 1192a, 1695a Portland cement: 1578, 1841) (10) road material: 750 silver: 172 strontium: 712 tin : 273, 275 topaz: 1846 (07) (08) (10) (12) (13) water: 339, 457, 472, 530, 780, 959, 1086b, 1336, 1575, 1581, 1603 paleobotany, Eocene: 109 paleogeography: 503, 743, 776, 1580 Cretaceous: 1240, 1587 Eocene: 500 paleonfology : 199, 1130, 1131 1727 physiography: 457, 538, 761, '776, 1017, g~g· 1330, 1575, 1580, 1581, 1585, pre-Cretaceous in wells: 1651 soils: 136, 472, 766, 1575, 1603, 184la stratigraphy: 182, 383, 1709a Cretaceous : 172, 323, 339, 383, 390, 461, 732, 733, 746, 750, 766, 772, 808, 820, 1017, 1042, 1060 1331 1389, 1462, 1463, 1467, 1477, 1573' 1574, 1575, 1749, 176ld • Paleozoic: 1130, 1131, 1471 1583, 1584, 1702, 1703 • Pennsylvanian: 339, 1130, 1583, 1584 pre-Cambrian: 1682 structure: 564, 671a, · 743, 766, 1693, 1695 The Geology of Texas-Subject lndex central Texas--continued topographie mapping: 427 voleanoes: 793 Cephalopoda. See paleontology unde~ systems. ceramie industries: 1245, 1378a Cer.ro de Muleros : 128a, 129 Chadwick, G. H. : 327 Chaffin limestone. See Pennsylvanian formations, Thrifty. chalk: 427, 1185a Cretaceous, origin : 7 44 formations: 621, 608, 816 Chalk-Roberts field: 1675a Chambers County: 32, 113, 416, 896g, 898a, 1146, 1278a, 1711, 1841b Chaney formation. See Permian forma­ tions. Chapman oíl field, Williamson County : 1430, 1444a Charc<>-Redondo oíl: 1406, 1787a Chazy formation. See Ordovician forma­tions. Chazy-Sylvan uneonformity, Big Lake, Reagan County: 1020a chemical analyses fossil bones : 141O minerals: 1378 rocks : 516, 1878 salt dome waters, Goose Creek and Orange: 1110 well waters: 260a chemical composition of waters of north­ eastern Texas : 609 Cherokee County: 180, 267a, 415, 460, 470, 506, 668a, 876, 905, 992a, 1080h, 1219, 1223, 1232, 1270, 1297, 1298, 1553, 1687a, 1688c, 1844a. Cherry limestone. See Pennsylvanian for­ mations, Caddo Creek. Cheyenne sandstone. See Cretaceous for­ mations. Chickasha formation. See Permian for­ mations. Chico, Wise County : 132 Chico Ridge limestone. See Pennsylva­ nian formations, Graford. Childress Cot;nty: 247, 1353c, 1841a Childress dolomite. See Permian form:i­ tions, Blaine. Chinati Mountains : 44a, 46 Chinati series. See Permian forma.tions Chinle formation. See ·Triassic forma­ tions. Chisos country: 46, 827a, 1626 Chisoe ~ountains : 1202, 1626 Chisoe rift, Río Grande canyons : 799 chloride concentration, underground wa­ ters.: 1233 Choctaw and Grayson terranes : 325 Choza formation. See Permian formn­tions. Chupadera formation. See Permian for­ mations. Church and Fields pool, Crane County : 1787 Cíbolo basin·, map of : 63 Cíbolo formation. See Permian forma­ tions. Cieneguita beds. See Permian forma­ tions. Cimarron group. See Permian forma­tions. cinnabar. See also mercury : 121, 807, 845, 1013, 1822 Cisco group_ See Pennsy)vanian forma­tions. Citronelle group. See Pliocene forma­ tiona. Claiborne group. See Eocene formations. Clarendon formation. See Pliocene for­ mations. Clarksville, age of ehalk at: 621 classification Cephalopoda: ·446 Echinodermata: 972, 973 geological: 1044 J urassic : 1048 Jurassic-C1:.etaceous: 791 (and) nomenclature of physiographic features: 821 · Permian red beds : 618 rudistids : 443 Triassic : 1048 Clay County: 3ld. 5~<>. 82. 83a, 22lb, 249c, 64la, 902, 114óa, 1216b, 1216d, 1219, 1227. 1228, 1346, 1449, 1450, 1492, 1606b, 1630, 1632, 1673, 1849a Clay Creek salt dome, Washington Coun­ ty : 267a, 696, 967, 968, 184lb clay dunes, origin of in south Texas : 260 clay industries in McLennan County : 11 clays: 105a, 386, 413, 415b, 506, 709, 837b, 907, 992, 1185a, 1219, 1245, 1311, 1319, 1320, 1320a, 1321, 1353a, 1378, 1378a, 1402, 1591, 1652, 1789, 1790, 1841, 1846 (91) (92) (10) Claytonville dolomite. See Permian for­. mations, Cloud Chief. Clear Creek limestone. See PennsylvlV nian formations. Brad. Clear Fork group. See Permian forma­ tions. climate: 881, 1522d Clo~d Chief formation. See Permian for­ mations. CJyde formation. See Permian forma­tions. coal. See also lignite: 36, 172, 339, 345, 412d, 413b, 415b, 449, 470, 485 817 837b, 883, 983, 1108, 1186a, ' 1200: 1206, 1214a, 1215, 1218, 1219, 1318, 1503, 1556, 1557, 1577, 1584, 1652, 1722, 1823, 1823a analyses of: 530, 539, 640, 1016, 1215, 1242, 1378, 1503 beds : 1215, 1244 Central Basin formations: 458 composition of : 1215, 1218 Cretaceous, Río Grande region : 1739 description of samples: 1016 fields central Texas : 339, 1584 éhisos country: 1626 east Texas: 172, 470 north-central Texas : 35, 120. 170, 172, 449, 454, 548, 1206, 1214c, 1?.15, 1360, 1460, 1577, 1584, 1603, 1722&, 1823, 1846 (83) (884) (87) (88) (91) (92) (09) (10) southwest Texas : 8b, 36, 105a, 412, 540, 872a, 1108, 1166, 1206 1215 1214c, 1373, 1610, 1684, 1687, 1739: 1846 (83-4) (85) (86) (87) (88) (92) (10) Trans-Pecos Texas: 1304 1684 18'6 (93) • • • Trinity region: 1316 fixed carbon ratio comparison : 962 Government contract, delivery and an­alyses : 1242 Guadalupe Mountains: 1588 ~ale, Sidne,y : 1846 (21-22)mdustry: 1214e Lesher, C. E. : 1846 investigation : 152 occurrence and production : 883, 1200 972 The University of Texas Bulletin No. 3232 coal-continued origin and oecurrence : l 7 50 Coa! Measures northern Texas : 1466 oil and gas: 3 paleoñtology: 1495, 1713, 1755 Coastal Plain. See Gulf Coastal Plain. Cochran County: 42, 56b, 471, 1086 Cockfield formation. See Eocene forma­ tions. Coelenterata. See paleontology under sys­ tems. Coetas formation. See Pliocene forma­ tions. Coke County: 9, 80, 87, 88, 90, 92, 247, 432b, 886, 1264 Cole-Bruni oil field: 1613s. Colems.n County: S2, 90, 247, 342, 371, 380, 432b, 449, 511, 649, 855b, 970, 1215, 1219, 1227, 1228, 1258, 1673, 1727b, 1727c, 1753a, 1844a, 1853 Coleman Junction limestone. See Per­ mian formations, Putnam. Coleman limestone and abale. See Per­ mian formations. Admira!. collecting methods, paleontological : 1544, 1545 Collin County: 31a, 3lb, 373, 3821, 391, 515, 554a, 803, 844, 899b, 1188, 1282. Collingswortb County :' 854b, 1841s. Collingsworth gypsum. See Permian for­ mations, Blaine. Colorádo, Mitcbell County, artifacts: 282, 283, 284 Colorado coa! field : 449, 1603 Colorado County: 38, 421 Colore.do forms.tion. See Cretaceous for­ mations. Colore.do River: 167s., 387s., 743, 1575 Austin dam : 1592a, 1594 coa! fields: 1584 Lake Austin : 1594a, 1595, 1595a Lake McDonald, 1592a Midway section: 662 profile of: 1848 (44) terraces : 1585 colors, use of in geo]ogic mapping : 834 C9lum.bia: 1382b Coma! County: 164, 421, 515, 889a, 1009, 1086c, 12,!!5a, 1727a, 1841a Comanche . County: 82, 549, 598, 970, 1064, 1215, 122.7, 1228, 1258, 1848, 1403, 1673, 1699, 1759a Comanche Creek. See Pennsylvanian for­ mations, Strawn. Comanche Peak formation. See Creta­ ceous formations. Comanche series. See Cretaceous forma­ tions. composition of iron ores of Texas: 514 Concho bluffs, Winkler County: 1787 Concho County: 247, 449, 984, 1403, 1650 Concho country : 341, 984 Concho divide: 247 Concho River, profile of : 1848 (44) concretion fo~mation: 185b, 185c, 185d cone-domes, 01! from : 13 64 conglomerates : 82 Conroe oil field: 1596 conservation methods, gas and oil: 123 contact Carboniferous-Cretaceous: 1005 Cretaceous-Tertiary: 746, 1528 Ellenburger-Boone:-1354 Franklin Mountains : 1012 metamorphism, Hueco limestone: 933 Mississippian-Ordovician : 1354 Midway-Wilcox, foraminiferal evi­ dence : 1238b Cook Mountain formation. See Eoéene formations. Cooke County: 9, 10, 69b, 189, 583, 64la, 654, 675, 803, 967a, 1232, 1284, 1353c, 1606b, 1727b, 1727c Cooledge chalk. See Cretaceous forma­ tions. Coon Mountain sandstone. See PennsYl.­ vanian formations,. Pueblo. Cooper area. Delta County, soil survey: 1844a copper: 346, 651, 1005, 1219, 1302, 1338, 1662 Archer County: 573 central Texaa : 172, 1846 (83-4) Llano-Burnet region : 1171 nortb-central Texas: 172, 340, 342, 551, 573, 1216, 1302, 1374, 1846 (83-4) Permian ores: 41, 1216, 1302, 1374 west Texas: 340, 342 coprolites, Permian : 1150 coral reefs and ·oil fields : 896b coral reefs in Oligocene: 522 corals. See Anthozoa under systems. Cordilleran front range, the: 44 Cordilerra, Tertiary orogeny: 1284a core from Lytton Springs oil fields, de­ scription by M. A. Hanna : 188 core drill tests for potasb: 1418, 1808 cores, metamorphism of: 1260, 1803 Corpus Christi area, Nueces County: 896, 1277, 1278a, 1844a correlation. See aleo individual systems. Algonkiii.n and Archean: 1681b basis fossil vertebrates: 688 basis paleogeography : 1382c foraminiferal: 507, 508, 1229 glacial epochs : 827 e Neocene: 387a paleontological: 9, 607, 508, 1229 oil wells, nortb-central Texaa : 879 Rustler Springs : 1637 strata in deep wells, Reagan County : 102.1 Texas coaat slope: 827c Corrigan formation. See Oligocene for­ mations, Gueydan. corrosion and corrasion, Barton Creek, Austin: 929 Corsica.na area, ·,Navarro County : 3. 1062, 1109, 1834a Coryell County: 421, 803, 1228, 1403 Cottle County: 247 Cottonwood Creek. See Pennsylvanian formations, Strawn. Cotylosauria. See paleontology under systems, Vertebrata. county geologic mapa: 1343, 1853 Cox sandstone. See Cretaceous forma­ tions. cracking, processes atid patente: 519 Crane County: 76b, 190a, 1477 1671 1787, 1847 ' ' crater, Ector County: 69a, 1415 Cretaceous: 13, 176, 277, 300, 829, 584, 585, 663, 732, 733, 735, 736, 7 40, 7 44, 746, 746, 748, 762, 755, 764, 766, 820, 822, 1042, 1047, 1051, 1331, 1335, 1389, 1444g, 1456, 1463; 1467, 1469, 1474, 1475, 1623, 1524, 1628, 1577a, 1587, 1652, 1656, 1741, 1746 correlation : 9, 173a, 300, 391, 42.4, 425, 439, 440, 521, 585, 608, 618a 643 678, 732, 746, 769, 782, 787, 78IÍ 791' 792, 816, 822, 870, 1042, 1046, '1062: 1053, 1144, 1291, 1327, 1328 1330 1331, 1389, 1390, 1391, 1511,' 1522a: The Geology of Texas-Subject Index Cretaceous--continued correlation--continued 1523, 1524, 1532a, l535a, 1538, 1590a, 1601a, 1621, 1681, 1691, 1741, 1744, 1746, 1749, 1749a formations: 135, 175, 391, 392, 782, 803, 820, 1234b, 1331, 1332, 1353, 1520a, 1532a, 1575, 1621, 1741 Anacacho: 49 paleontology: 13 stratigraphy: 578, 992 Annona : 389a, 391, 520, 816, 1601c paleontology: 31a, 31c, 38lc, 382e, 382k, 3821, 521, 1363b Austin: 31b, 142a, 385, 513b, 820, 1113a, 1140 correlation: 806, 816, 870, 1534 paleontology: 13, 30, 3la, 31c, 119, 134, 38lc, 382d, 382e, 557, 867, 976, 1077a, 129la, 1292a, 1295a, 1393, 1540, 1554a source of Portland cement ma­ terial: 412b, 515, 1577a stratigraphy: 11, 16, 144a, 188, 458, 506, 578, 609, 971, 992, 1257, 1402. 1407, 1454, 1601c, 1652 Basemeñt sands: 20la, 629b, 1394, 1398c Benton: 45 Bingen : l 700d Blossom, paleontology : 521 Bonham: 3lb, 870 Boquillas flags: 1626 Bosque: 827 Brownstown : 31e, 521, 870, 1538 Buda: 134, 385, 822, 1447, 1652, 1756 paleontology : 10, 13, 520, 732, 752, 1295a, 1447, 1688, 1756, 1757 stratigraphy: 16, 28a, 201a, 578, 992, 1324, 1402 Caprina limestone: 124a, 784 Cheyenne: 323 Colorado: 1312 Comanche Peak: 142a, 385 paleontology : 13, 1520b stratigraphy : 16, 578, 704 Comanche series: 647a, 772, 789, 1520a, 1522a, 1522c, 1524 correlation. See Cretaceous corre­ lation. paleobotany : 98a, 545, 783, 789 paleontology: 10, 17, 19, 199, 316, 326, 329, 3821, 474, 583, 586, 626, 642, 787, 789, 796, 1363c, 1388, 1621, 1678, 1689, 1727 stratigraphy: 11, 16, 91, 177, 189, 201a, 323, 325, 458, 596, 674a, 706, 766. 772, 789, 841, 913i, 917, 1172, 1288a. 1312, 1314, 1524, 1621 Cooledge chalk : 1297 Dakota: 45, 108la, 1288a, 1522e Del Río: 134, 1378, 1635 paleontology : 10, 13, 31a, 3lc, 133, 199, 1237, 1628 stratigraphy: 11, 16, 201a, 578, 992, 1152 Denton paleontology : 9, 10, 13, 30, 31a, 381a stratigraphy : 12, 189, 383, 1790, 1791, 1798 Devils River limestone: 1324 Duck Creek paleontology: 9, 10, 13, 30, 31a, 38la, 1388, 1511b stratigraphy: 11, 12, 189, 383, 820, 1391, 1398c, 1790, 1791, 1798 Durango member : 891 Eagle Ford : 385, 1140 Cretaceous--continued formations-eontinued paleontology: 13, 30, 199, 1141 stratigraphy: 11, 16, 128a, 144a, 247d, 458, 506, 521, 578, 602b, 609, 971, 992, 1113a, 1141, 1324, 1353, 1405, 1454, 1534, 1652 Edwards: 142a, 385 paleontology: 13, 784, 1738 stratigraphy: 16, 20la, 578, 820, 896a, 936, 1223a, 1402, 1652 Escondido paleontology: 13, 31a, 499 stratigraphy: 502a, 578, 992 Etholen: 46 Finlay: 46 Fort Benton: 1081a Fort Pierre: 1081& Fort Worth: 1493a paleontology: 9, 13, 30, 31a stratigraphy: 11, 12, 189, 383, 1789, 1790, 1791 Fredericksburg group: 9, 27, 515, 1395, 1522e paleontology: 9, 13, 125, 784, 865, 1392 stratigraphy: 9, 11, 12, 16, 45, 46, 177, 201a, 458, 506, 896a, 992, 1652, 1789 Georgetown : 385, 1598a paleontology: 3la, 31c, 199 .• 520 stratigraphy: 11, 16, 201á, 383, 578, 1601c · Glen Rose : 161b, 161c, 385, 406&, 612, 948a paleontology: 13, 1452, 1688a, 1727&, 1805 stratigraphy: 11, 16, 20la, 247e, 578, 612, 674a, 936, 992, 1394, 1398c, 1402, 1652, 1789, 1790 Gober: 31a, 31c, 1534, 1601c Goodland : 513b Pªis~btology : 9, 30, s1a, 31c, 381a, stratigraphy: 173a, 189, 674a, 1398c, 1681a, 1790, 1791 Grayson: 822 paleonto!ogy: 9, 10, 30 str1;~~raphy: 31, 325, 1789, 1790, Gulf series: 609, 1534, 1539 paleontology: 16, 21, 1363c str1"stJraphy: 392, 458, 1534, 1539, Kiamichi paleontology: 9, 13, 30 3le stratigraphy: ll, 12, i89, 383, 820, 1398c, 1789, 1790 1791 Laramie group: 296b 736 1567a 1744 • • • Lewisville : 1455b Lott ehalk: 391, 1601e Main Street: -822 paJ~ntology: 10, 13, 30 strat1graphy: 383 1791 Marlin ehalk: 391, '160le Mip:on sandstone: 936 Naeatoeh : 382i, 850 Navarro; 385, 546d paleontology: 13, 30, 3la, 31e 199 35lb, 356e, 378a, 381e '382a' 382e, 382i, 382k, 3821. sin 537' m~ª· 1363a, 1363b, 1363e.' 1700: stratigraphy: 391, 506, 609, 637, 1402, 1534, 1652 Niobrara: 45, 1081a Olmos: 578 Ozan: 1601e 974 The University of Texas Bulletin No. 3232 Cretaceous--continued formations-eontinued Paluxy: 16, 247e, 274a, 1394, 1398c, 1652, 1789, 1790 Pawpaw: 134 paleontology: 9, 10, 13, 30 stratigraphy: 383, 1789, 1790, 1791 Pecan Gap: 531, 899b paleontology: 3la, 3lc, 382k, 391, 521, 1077a stratigraphy: 144a, 391, 15llc Pierre: 45 Rattlesnake: 1626 Ripley: 1363a, 1363b, 1363c, 1520a 1522c, 1700 San Miguel: 578, 1541 Saratoga chalk: 382e, 382k, 3821 . 1577a, 160lb Taylor: 16lb, 385, 546d,. 1297, 1534. 1541 paleontology: 13, 15, 30, 3la, 8lc. 199, 356a, 356d, 378, 38lc, 38ld, 382a, 382e, 382k, 3821, 391, 521, 1363a, 1363b, 1688b stratigraphy: 11, 16, 144a, 391. 506, 609, 1297, 1402, 160la, 165~ Terlingua beds: 1626 Tokio: l 700d Tornillo clay: 1626 Travis Peak: 385 paleontology: 13, 180a, 1727a stratigraphy: 16, 180a, 1894, 1652 Trinity group : 98b, lOOb, 545, 948a, 1046, 1323, 1567a, l 707a, 1759a paleontology: 13, 180a, 762, 783, 1046, 1678, 1679, 168la, 1727a stratigraphy: 11, 16, 45, 177, 189. 20la, 247d, ·458, 506, 629b, 742. 827, 913d, 1088, 1394, 1652, 1679, 1759a, 1789, 1790, 1791 Walnut: 385, 67 4a · paleontology: 13, 80, 3la stratigraphy: 16, 173a, 20la, 674a, 704, 1398c, 168la, 1790, 1791 wr:~~~a group: 9, 27, 197, 1032, pa!eontology: 9, 10, 13, 19, 1727 stratigraphy: 9, 12, 16, 45, 46, 177, Wen~~\32Íla, 458, 506, 992, 1652 p8iri.W;'1ogy , 9, lo, 13, 3o, 3la stratigraphy : 11, 12, 189, 383. 1789, .1790, 1791 Wolfe City: 391, 899b Woodbine: 13, 30, 99, lOOc, 105 247e, 502a, 546b, 726b, 855d, 855g 1080a, lllla, 1140, 1231, 1232. 1233, 1234b, 1234d, 1853 1391 1455~, 1502a, 1522e, 1700d° ' strat1graphy: 105, 144a, 189, 247d. 389a, 506, 546b, 609, 971, 1232. 1234d, 1322a, 1353 1891 1454 1455b, 1632, 1709b' 1789' 1790, 1791 , , oil and gas: 45, 423, 506, 963 965 1062, 1109, 1193, 1255 1402 '1407. 1501, 1650 • .. Paleobotany: 13, 37a, 57a, 98a, 98h 99, lOOb, lOOc, 105 111 545 633 767, 783, 789, 948a, '949, '1286,' 1410 1416._ 1474, 1627, 1707a, 1758a, 175'.> paleochmate: 1522d, 1750 paleogeography: 135, 145b, 181 7211' 745, 753, 788, 1240, 1363, ' 1382b. 1382g, 1385a, 1536, 1567a, 1587 . 1744, 1746, 1761c paleontology: 12, 13, 31, 127, 129, 14' 266, 277, 277a, 277b, 324, 326, 33r 368, 375, 381, 392, 421, 441, 442 . Cretaceous-oontinued paleontology-eontinued499 555a, 568a, 578, 584, 585, 630, 664h, 732, 748, 752, 753, 755, 762, 767 783 784, 787, 789, 803, 1005, 1009, 1041, 108la, 108lb, 1106, 1256, 1286 1295a, 1330, 1331, 1389, 1456, 1463, 1464a, 1469, 1497, 1518, 1520, 1520;., 1527, 1528, 1530, 1532a, 1533, 1575, 1621, 1674, 1681, 1687a, 1691, 1700, 1734, 1735, 1736, 1738, 1743, r!:b.o!¿:~ 9, 837, 1528a, 1687a, 1688, 1727, 1722,a. 1743 Brachiopoda: 9, 555, 559, 1363, 1382 Bryozoa: 127, 767, 871, 1382 catalogue: 144, 555 Cephalopoda: 9, 10, 11, 15, 18, 20, 125, 134, 180a, 265, 330, 407, 426, 446 557, 789, 866, 867, 976, 1222a, 1256. 1279, 1290, 1291, 1291a, 1292, 1292a, 1372, 1372a, 1388, 1389, 1392, 1393, 1505, 1506, 1507, 1507a, 1508, 1509, 1510, 1511, 15lla, 1518, 1738, 1812 check list, Invertebrata: 735, 755 Coelenterata: 1256 Crustacea: 1383, 1518 Echinodermata: 9, 10, 17, 18, 19, 21, 31, 251, 252, 253, 322, 383, 409, 435, 747, 972, 973, 974, 1256, 1334, 1371, 1474a, 1491, 1493, 1518, 1757 Foraminifera: 9, 10, 18, 29, 3la, 65, 134, 199, 249, 35lb, 353, 354, 356, 356a, 356c, 356d, 356e, 357, 358, 359, 362, 365, 368, 370, 373, 375, 376, 377, 378, 378a, 381, 381a, 38lb, 38lc, 38ld, 38le, 382, 382a, 382d, 382e, 382f, 382i, 744, 1057, 1237, 1238, 1238a, 1362a, 1363a, 1363b, 1363c, 1474a, 1479a, 1600, 1681, 1681a, 1688a, 1753 Gastropoda. See also Mollusca: 9, 10, 388, 520, 664a, 1256, 1290, 1518 Mollusca: 124a, 126, 128, 129, 168, 277, 280, 326, 327, 329, 373, 388, 474, 555, 557, 559, 584, 702, 703, 752, 945, 946, 976, 984, 1106, 1256, 1295, 1330, 1333, 1334, 1835, 1339, 1375, 1379, 1447, 1464&, 1469, 1520b, 1522, 17 40 Ostraeoda: 18, 28, 30, 31c, 869, 1678 Peleeypoda: 10, 22, 126, 128, 133, 280, 320, 474, 520, 586, 642, 702, 703, 703a, 796, 872, 946, 947, 1045, 1047, 1175, 1256, 1290, 1294, 1359, 1372, 1487, 1518, 1522, 1527, 1540, 1680, 1737, 1740 rudistids : 17, 437, 438, 439, 440, 443, 444, 445, 447, 945, 1175, 1335, 1532, 1609 Porifera: 1103 Vermes: ' 1518 Vertebrata: 57a, 299, 318, 583, 626, 679, 1119a. 1256, 1290, 1452, 1554a, 1567a, 1755 sedimentation: 629b, 1567a stratigraphy: 755, 1375, 1749, 176ld central Trucas: 14, 16, 164, 172, 177, 182, 199, 267, 268, 323, 339, 383, 390, 421, 647a, 727, 732, 744, 746, 750, 766, 772, 808, 888, 1017. 1042, 1062, 1076, 1157, 1168, 1331, 1389, 1401, 1402, 1404, 1407, 1412, 1462, 1463, 1467, 1475, 1520a, 1523, 1574 1575, 1576, 1613a, 1802 ' north Texas : 9, 132, 17 4, 17 5, 176, 182, 189, 247d, 825, 38.3, 392, 401, 421, 461, 506, 521, 541, 542, 543, 608, 609, 643a, 674a, 781, 732, 742, The Geology of Texas-Subject Index Cretaceous-continued stratigraphy--continued north Texas-continued 744, 746, 750, 753, 766, 772, 788, 803, 816, 820, 840, 843, 844, 859, 964, 1037, 1038, 1Q59, 1060, 1064, 1079, 1088, 1113b, 1114, 1141, 1142, 1157, 1232, 1247, 1248, 1250, 1252, 1296, 1297. 1298, 1389, 1391, 1394, 1398b, 1449, 1477, 1512, 1520a, 1528, 1530, 1534, 1574, 1575, 160la, 1679, 1691 southwest Texas: 135, 181, 192, 201a, 468, 480, 564, 643, 722, 782, 794, 795, 807, 822, 896, 1249, 1379, 1541, 1590, 1623, 1625, 1681, 1684, 1686, 1746, 1747 west Texas : 8, 12, 44, 45, 87, 129, 135, 153, 200, 331, 341, 343, 346, 395, 467, 474, 492, 577, 615, 643, 707, 787, 789. 791, 807, 841, 936, 944, 1037. 1038, 1046, 1047, 1048, 1051, 1053, 1249, 1263, 1259, 1304, 1306, 1312, 1314, 1414, 1442, 1520, 1522b, 1561, 1666, 1573, 1623, 1684a, 1744, 1746, 1787 Crinoidea: See paleontology under sys­tems. Crockett County: 8, 190a, 491, 913a, 991, 1477, 1814b, 184la, 1847 Crosby County: 42, 236d, 236e, 471, 847, 848 Cross Timbers region : 731, 735 Croton gypson. See Permian formations, Peacock. crude oil: 530, 654, 953, 954, 1022, 1030, 1303, 1877, 1499, 1500, 1500a Crystal Falls limestone. See Pennsylva­ nian formations, Harpersville. crystalline rock: 433, 617 crystallography: 603 cuestas : 1453 Culberson County : 33a, 46, 94, 396a, 396b, 432b, 474, 936a, 936b, 936d, 1013b, 1035c, 1080a, 1217, 1219, 1222, 1234e, 1243, 130la, 1304, 1314, 1357, 1444e, 1477, 1645a, 1546b, 1549, 1634, 1647, 1662, 1663 Culebra structure, Medina County : 992, 1402 Cundiff limestone. See Pennsyltvaniam formations, Caddo Creek. Currie field, Navarro County: 961, 967, 1816 cycads. See paleobotany under systems Dagger Flat sandstone. See Cambrian · formations. Dakota formation. See Cretaceous for­ mations. -· Dale oil field : 1444a Dallam County: 42, 56b, 392a, 1841a Dallas County: 31c, 167a, 277a, 515, 547, 803, 1027, 1060, 1219, 1232, 1320a, 1448, 1454, 1455, 1844a Damon Mound, Brazoria County : 32, 113, 114, 418, 522, 1345 dams: 166, 1181, 1182, 1592b Dangelmayr field, Coóke County: 675 Darst Creek field, Guadalupe County: 896a, 1355 Davis Mountains: 44, 396b. 1162, 1455a Dawson County: 42, 471, 689a, 1619a Day Creek formation. See Permian for­mations. Deaf Smith County: 42, 56b, 471, 1841a declination. See magnetic declination. decline curves: 1322, 1526 deep borings, Balcones fault zone: 1661 Deep Creek field, Callahan County: 1699 deep drilling : 693a, 890, 893, 89~. 895, 955 deep wells : 473, 609, 659, 661, 778, 880a, 1116, 1117, 1421, 1425, 1492, 1682b Delaware-Guadalupe dome: 44 Delaware Mountain formation. See Per­ mian formations. Delaware Mountains: 44a, 116a, 122, 201, 919a, 1110, 1118, 1314 Del Rio formation. See Cretaceous for­ mations. Delta County : 609, 844, 160lc, 1844a deltaic Coastal Plain : 70 deltas : 208c, 1288 Dennis Bridge limestone. See Pennsyl­ vanian formations, Millsap Lake. density, Coastal Plain rocks: 1370 Denton County: 9, 10, 3lc, 381a, 675, 844, 967a, 1219, 1232, 1320a, 1455b, 1464, 1673, 1791, 184la, 1844a Denton formation. See Cretaceous for­ mations. depositional history : 50 descriptive terms, physiographic : 1381 1esert, American: 810 desert range tectonics, Trans-Pecos Tex­ as: 48 development methods : 728, 1063 Devils Den limestone. See Pennsylvanian formations. Graford. Devils River Jimestone. See Cretaceous formations. Devin«: structure, Medina County : 992 Devon1an : 44, 618a forrnations Caballos novaculite : 44, 936, 936a, 936c, 1626, 1652, 1696b Percha shale: 936b paleogeography : 629a. 1382g, 1761c s '.ratigraphy : 396, 936a, 936b, 1020, 1021, 1695b DeWitt County: 40, 421, 1033d, 1477, 1488, 1841a Diablo Plateau region: 91 491 936d, 1682a ' ' d!amond drilling, Navarro County: 423 d1amonds : 1846 (11) (12) d!astrophism, Marath.on basin: 47 d1.atomaceous deposita : 1185a, 1245, 1798 D1ckens County: 7, 42, 482, 913a, 1264, 1617, 1619a, 1635, 1844a Dickerson member. See Pennsylvanian formations. Millsap Lake dikes: 636, 1009 · Dimmitt County: 109a, 421, 1013b, 1186a, 1613a, 1841a Dimple formation. See Pennsylvanian formations. dinosaur tracks : 1452. 1805 disconformities : 822 discovery and development: 1104, 1111, 1262, 1270 d!sc~>Ve~y methods, oil and gas: 67, 250 d1stdlation of oíl: 49 Dockum ser!es. See Triassic formatione. Do¡r Bend hmestone See Pennsylvanian · formations, Mineral Wells. Do¡, Cr<;ek formation. See Permian for­ mabons. dolomite: 80, 618, 1003 1567b dolomitization: 647a, 9G2 dome-f~rming materials: 1344 . domes in east Texas : 606 Donley C?unty: 42, 1546b, 1841a Doth~n hmestone. See Permian forma­ tions, Moran. Double Mountain group. See Permian formations. n. See Cretaceous formations. Eskota formation. See Permian forma­tions, Peacock. Esperson salt dome, Liberty County : 76 Estacado meteorite : 84 7, 848 etched potholes : 1664 Etholen formation : 46 euhedral orthoclase crystals : 1007 Evaporite series. See Permian forma­tions. explorations: 118, 119, 120, 642, 763, 774, 827b, 1006, 1036, 1087, 1039, 1064, 1056, 1176, 1241, 1466, 1476a exploratory geology, Trans-Pecos Texas: 46 Falfurrias salt dome: 66 Falls County: 38lc, 415, 421, 606, 644, 662, 803, 160lc Fannin County: 616, 803, 844, 1232, 1292a, 1363 faults: 67, 827a, 999, 12'6, 1268 Fayette County_: 16lb, 240, 253a, 418, 421, 470, 103lb, 1087, 1097, 1105, 1219, 1320a, 1343, 1707a, 1'108, 1709, 1754, 1764a Fayette formation. 8ee Eocene forma­ tions. feldspar deposita : 77, 1186& Ferguson formation. See Permian for­ mations. 978 The University of Texas Bulle-tin No. 3232 fertilizers : 469 field geology: 970a Finis shale. See Pennsylvanian forma­ tions, Caddo Creek. Finlay formation. See Cretaceous forma­ tions. Finlay Mountains : 1622b Fisher County: 247, 114la, 1727a, 1863 Fisk-Shields pool, Coleman County: 610, 511 Ffeniing group. See Miocene formations. fiint industry: 812 floating sand: erosiona! force: 1480 Floresville oil field, Wilson County: 896d Flower .Pot formation. See Permian for­ mations. Floyd County: 42, 342 Foard County: 83a, 96, 108, 247, 990, 1606a, 1727b, 1846 (12), 1863 footprints. See tracks and trails under paleontology of systems. Foraminifera. See paleontology under systems. guides to Texas coast deposita : 507 re-classification: 361 r4i'6t~ve measurements in study of : formations. See same under systems. aids to identification of: 1652 peculiar : 814 Fort Belknap, geological collections: 556, 834a, 1476b Fort Bend County: 32. 143b, 415, 421, 630, 638, 6(6, 1261, 1372b, 1488, 1569a, 1696b, 1763b, 1811, 1841b Fort Benton formation. See Cretaceous formations. Fort Peña formation. See Ordovician formations. Fort Pierre formation. See Cretaceous formations. Fort Stockton quadrangle: 12 Fort Worth area: 1449, 1788 Fort Worth formation. See Cretaceous formations. fossil horizon markers : 1800 fossil ice crystals: 1628, 1647 fossils, index : 630 Four Six dome, Potter County: 670 Fox Ford bed. See Pennsylvanian for­ mations, Strawn. Fox Hills: 45 Franklin County: 470, 609 1232 184la 1844a ' ' ' Fran.klin Mountains: 242, 396, 429, 913c 1012, 1304, 1308, 1309, 1312 1674b0 1682a, 1846 (10) ' ' Frasl~2lrocess, sulphur production by : Frederick, Oklaboma: 1444d FI'"edericksburg group. See Cretaceous formations. Freestone Caunty: 404, 415 470 506 567, 726c, 966, 1011, Í060, ' 1232: m~~· 1247, 1262, 1444g, 184la, Frio County: 421, 470, 678, 668a, 1013b 101Sc, 1013d, 1488, 1841a ' Frio .formation. See Oligocene forma­ bons,. Fry 9~:n area, magnetometer survey of : fuels: 469, 1218, 1819 fue! tests: 1015, 1806, 1807 Fulda sandstone. See Permian forma· tions. Clyde. fuller's earth: 397, 413, 506, 1179, 1185a, 1246, 1378, 1378a, 1402, 1662, 1846 (10) fungi, fossil: lOOd Fusulinidae. See Foraminifera under paleontology of systems. Fusselman formation. See Silurian. gabbro, analyses of: 1009 gadolinite, Llano County: 604 Gaines County: 66b, 190a, 471, 1947 Gainesville, Cooke County, evidence of drift : 1284 galena in salt dome: 646 Galveston Bay, soundings: 861 Galveston city artesian wells: 661, 778, 1488 Galveston County: 32, 145b, 416, 473, 641b, 645, 669, 661, 778, 851, 952, 1080, 1343, 1488, 1650, l 763b, 184lb Gaptank formation. See Pennsylvanian formations. Gaptank-Wolfcamp problem, Glass Moun­ tains: 924 Garza County: 42, 236d, 471, 1847 gas. See oil and gas and natural gas. gasoline: 729 Gastropoda. See paleontology under sys­ tems. gazetteer: 662a, 1848 (448) gems and precious stones: 1219, 1359 geochemical investigations: 1230, 1231, 1233 geographic development: 761, 782, 802. 809, 821, 1486a geography: 138, 343, 412e, 415a, 436, 487, 628, 647c, 780, 800, 803, 1128, 1486, 1494a, 1567a, 1589, 1603a. 1688c geologic classification : 104• collections: 118, 119, 120, 1476b conferences, west Texas : 1837 formations aids to identification of: 1653 areal distribution : 760 at railway stations : 1030a indicated by vegetation: 385 history: l 76lb Antillean region: 1385a Cretaceous: 7 45 Gulf of Mexico: 721b Pennsylvanian : 691a Permian : 194a Van Horn quadrangle: 1314 literature: 1155a, l166b, 1165c, 1166d, 1833e museum : 1862 nomenclature: 1044 proceases: 238 profile: 432b railway guide: 1018 relations of water-bearing fonnations : 609 time measurements : 59 Geological Survey: 270, 453, 454, 458, ~~~8 471, 472, 476, 777, 1098, 1339, activities: 1417, 1434, 1444 (af7~~ 1:f~icultura1 survey: 170, 172, field operations: 1827, 1829, 183t history of: 734, 1098, 1419 progresa : 1468 reporta : 170, 172, 173, 182, 454, 468 469, 462, ·472, 477, 1460, 1546, 1831: 1832 The Geology of Texas-Subject Index Geology Department, The University of Texas, plan of instruction, 1888 : 1851 geology of Texas, record of, 1887-1896: 1483 geopbysical investigations: 69b, 73, 405, 513a, 572d, 572e, 697, 1525b, 1569a Bend-Ellenburger contact: 1655 Gulf Coast salt domes: 61b, 143b, 606, 1075, 1372b, 1711, 1815a magnetometer surveys: 994, 1513, 1514, 1515, 1649 seismograph: 1077a Sunberg method: 1815 torsion balance: 69b, 73, 75, 1525b Georgetown formation, See Cretaceous formations. Georgic sea: 1382b geosyncline, sites: 1382ggeothermal data: 58a, 676, 694, 695, 975a, 1230, 1233, 1234b, 1682b Gillespie County: 454, 572c, 891, 1148, 1219, 1343, 1477, 1563, 1707a, _184la Gilliam formation. See Permian forma­tions. Girty, G. H.: 1172 glaciated regions. origin of terraces : 1585 glaciation: 208a, 1287 glass : 40, 506, 1180 Glass Mountains: 44, 44a, 131, 133a, 510c, 927, 928, 930, 933, 934, 936 stratigrapby: 913k, 924, 925, 927, 930, 936, 936f, 937' 1643, 1652 Glasscock County: 76b, 432b, 1619a, 1847 glauconite: 185b, 458, 594, 597, 600 Glen Rose formation. See Cretaceoeus formations. Glenn formation. See Pennsylvanian for­mations. Gober formation. See Cretaceous forma­ tions. gold: 172, 500, 530, 1219, 1283, 1366, Goen15f¡;;..,!~~e. See Pennsylvanian for­ mations, Garner. Goliad County: 32, 421, 602, 1033b, 1488, Gonz1.:i:!\:.!!!i;: 32, 40, 164, 355, 382b, 421, 899b, 1219, 1488, 1733 Gonzales limestone. See Pennsylvanian formations, Grabam. Goodland formation. See Cretaceous for­ mations. Goodland Uplands: 1790 Goodnight beds. See Pliocene formations. Goose Creek, Harris County, salt dome oíl field: 418, 5858., 876, 877, 1110, 1111, 1266, 1268, 1269, 1271, 1345, 1427, 1502 Government Wells oil field: 1033a graben, Balcones-Mexia : 544 Graford formation. See Pennsylvanian formations. Graham County: 651 Graham formation. See Pennsylvanian formations. grabamite: 469, 475, 1836 Grand Gulf series. See same under Ter­tiary. Grand Saline, Van Zandt County: 1250, 1252, 1592 . granite: 84a, 179, 399, 891, 1148, 1171, 1185a, 1219, 1312, 1625c, -1662, 1846 (90) Granite Mountain area: 1481 Grape Creek shale and limestone. See Permian formations, Clyde. graphite: 450, 1074c, 1171, 1172, 1185á, 1333, 1652, 1846 (09) (13) (18) grave!: 1147, 1149, 1636 Gray County: 42, 410b, 525a, 643a, 854b, 855a, 1841a Grayson County: 9, 10, 3la, 31c, 173a, 177, 325, 381a, 382d, 382f, 515, 803, 844, 1232, 1320a, 1477, 1606b, 1841a, 1844a ­ Grayson formation. See Cretaceous for­ mations. Great Pla.ins: 672a, 776, 1652, 1713a greensand: 379, 456a, 546d, 1378, 14()2 Gregg County: 144a, 415, 460, 470, 546b, 855d, 855h, 896c, 971, lllla, 1232, 1322a, 1512, 1833g Grimes County: llla, 161b, 415, 470, 471, 506, 554, 906, 1488, 1753b Grindstone Creek member. See Pennsyl­ vanian formations, Millsap Lake. Groesbeck dolomite. See Permian forma­ tions, Blaine. ground water: 415b, 585a, 780a, 855h, 881, 1018d, 1086c, 1822a, 1'90b, 1602c, 1848 (375G) Guadalupe County: 76b, 164, 165, 421, 647a, 728a, 896a, 1009, 1223a, 1238b, 1355, 1442, 1444a, 1838a, 1844a Guadalupe group. See Permian forma­tions. Guadalupe Mounta.ins: 44a, 394a, 689, 913m, 1458, 1461, 1688 alga! reefs : 1357 natural resources: 1588 reef theory of origin: 918, 919, 921, 1002 stratigraphy: 122, 332, 590, 913j,. 1459, 1588 Guadalupian formation. See Permian for­mations. guano: 992, 1196, 1378 Gueydan group. See Oligocene forma­ tions. guidebook: 936g, 1833a Gulf Coastal Pla.in : 32, 74, 150, 416, 421, 508, 510, 513a, 692, 693, 801, 874b, 912, 1223a, 1671, 1577b, 1593, 1610, 1652, 1709a artesian wells : 1488 density of rocks: 1370 faulting: 1637 · geophysical investigations: 6lb, 143b, 606, 1075, 1649 igneous rocks: 1444a maps: 3, 40, 250, 416, 602, 641, 692, i~~~;. 1427, 1527.. 1628, 1636, 1610, marine movements: 1636 natural mounds, origin: 386, 647d, 813, 836, 1624, 1689, 1690, 1691, 1692, 1729 natural resources building materials : 1189 clays: 413 fullers earth : 413 iron ores : 1189 lignite6 : 1189 oil erude oil: 76a deep oíl deposita : 1026 fields : 34a, 46a, 64, 67, 143b, 146, 418, 486, 488, 604, 610, 536, 636, 537, 641, 688, 606, 636, 637, 641, 666, 692, . 693, 801, 811, 893, 1024, 1063, 1144a, 1198, 1255, 1346, 1596a, 1693, 1695a, 1700b, 1760 from igneous rocks : l444a 980 The University of Texas Bulletin No. 3232 Gulf Coastal Plain---eontinued natural resources-continued oil-continued (and) gas discovery: 67, 250, 135lb development: 72, 88, 143b, 418, 419, 433a, 510a, 546c, 606, 897a, 1024, 1255, 1568, 1596a production: 46a, 72, 250, 536, 893, 894, 1760 prospecting: 536, 1063 paraffin dirt : 159a, 1449a. producing horizons : 488, 1074b reserves: 76b • variation with depth : 1700b well stratigraph:¡o: 508, 1144a salt: 1024 paleogeography : 502, 503, 72lb, 776, 896c, 911, 1124, 1125, 1157, 1288, 1385a, 1536 paleontology: 26, 507, 950 physiography: 34a, 40, 69a, 421, 761, 776, 779, 1017, 1063, 1080, 1129, 1189, 1277. 1316, 1330, 1571, 1589, 1793 salt domes: 65, 69, 244, 249a., 250, 286a, 386a, 404a, 405, 406, 406a, 418, 419, 525a, 537, 585a, 641, 645, 647, 647b, 666, 668, 818, 887, 896g, 898, 1167a, 1250, 1261, 1270, 1298, 1344, 1351a, 1372b, 1427, 1569a, 1613a, 1728, 1792, 1834b cap rock petrograJ)hy : 63a, 71, 162, 163, 602, 602a Cretaceous formations on : 1142 geophysical investigations,: 76c, 513a, 1075, 1351b, 1372b interior domes : 1252 minerals : 6la, 63a, 69, 163, 406, 645, 646, 647 oil and gas development: 33, 34a, 63a, 69; 76, 143, 241, 249c, 249e, 419, 433a, 510a., 537, 693a, 893, 894, 897a. 1022. 1063, 1144a, 1198, 1568. 1596a, 1693, 1695, 1720 oil and sulphur development: 1841b origin : 162, 241, 244, 404a, 405a, 406, 406a, 505, 666, 811, 818, 819, 879, 912, 960, 1023, 1025, 1063, 1065, 1157, 1167a, 1247, 1250, 1260, 1344, 1344a, 1728, 1795 physionaphy : 63a, 65 prf~~:bting methods : 1063, 1372b, stratigraphy : 1449b structure: 63a, 898a 999a 1063 subsidence: 1427 ' ' sulphur concentration : 63 69, 708 sedimentation : 1448a ' soils: 136; 1844a. stratigranhy: 32. 74. 150, 458, 523, 692, 693, 72lc, 889. 1524b, 1709a Cretaceous: 18, 421, 766, 1157, 1252 1528, 1535a, 1761d ' Paleozoic : 1116 pre-Cretaceous : 1117 Quarternary: 143. 421 458 472 473 ~78, 481. 506, 537• • 778.' 905.' 906: i~~il074b, 1146, 1157, 1652, ·1716b, Tertiary: 40, 135, 143, 145, 390, 4l3a. 421, 458, 472 478 481 502 510, 524, 537, 578'.' 699.' 727: 778: 842. 884, 905, 906, 911, 1063, 1076, l139, 1146. 1157, 1189, 1299, 1330 1412, 1528, 1569, 1652, l 761d • structure: 250, 421 537 641 811 889 1025, 1063, 1065', 11:\4 Ú25 '1157' 1255, 1536, 1537, 1693 ' 1695 ' 1695a' 1793 • . • subsidence : 877, 1080, 1268, 1269, 1271, 1426a, 1427, 1445, 1502 Gulf Coastal Plain---eontinued subsurface methods in: 951, 1289 sulphur development: 143e, 163a, 1024 sulphur water: 708 volcanic activity : 39 Gulf of Mexico : 72lb . Gulf series. See Cretaceous formations; Gunsight 'limestone. See Pennsylvaman formations. Graham. Guthrie dolomite. See Permian forma­tions, Blaine. gypsum: 5a, 6la, 120, 336, 340, 342, 343, 506 534a 602a, 614, 618, 724, 837b, 921: 995,' 1074c, 1118, 1152a, 1185, 1219, 1306, 1362, 1378a, 1548, 1549, 1652, 1846 (91) Hager, D. S.: 549 Hale, Sidney A. : 1846 Hale County: 42, 471, 847, 848, 1095, 1096, 1652 Hall County: 1064, 1264, 1652, 184la Hamilton County: 5llb, 583, 803, 853, 1227. 1228, 1343, 1403, 1652, 1805 Hanna, Marcus: 188 Hanna Valley. See Pennsylvanian for­ mations. Strawn. Hansford County : 42, 56b, 1841a Hardeman County : 83a, 247, 1652, 1698, 1718 Hardin County: 3, 32, 62, 40Sb, 415, 418, 495, 506, 579a, 678a, 981, 1126, 1127, 1219, 1341, 1342, 1365. 1426a, .1427, 1569, 1650, 1652, 1841b Harlton, Bruce H. : 936 Harpersville formation. See Pennsylva­ nian formations. Harria County: 32, 143a, 239, 382b, 382h, 415, 417, 418, 420, 585&, 876, 877, 952, 1013b, 1110, 1111, 1219, 1266, 1268, 1269, 1271, 1320&, 1345, 1427, 1488, 1502, 1596, 1650, 1652, 1753b, 1844a . Harrison County : 103, 415, 460, 470, 632. 948, 1039, 1186a, 1219, 1232, 1488, 160lb, 1601c, 1652, 1682c, 1683, 1683a, 1841a, 1844a Hartley County: 42, 56b, 854b, 1841a Haskell County: 247, 537a, 1343, 1652 hauerite: 645, 1796 Hawley, H . J .: 577 Hawtof, E. M.: 675 Haymond formation. See Pennsylvanian formations. Hays County: 164, 421, 515, 889a, 1009, 1086c, 1240, l 727a, 184la, 1844a helium: 3ld, 432a, 1346, 1356 Hel)lphill bed. See Pliocene formations. Hemphill Cou.nty: 42, 532, 1072, 1073, 1074a, 1288a, 1841a Henderson area, Rusk County, soil sur­ vey: 1844a Henderson County: 415, 460, 470, 506, 1077a, 1219, 1232, 1320a, 1432, 1652, 1844a Hendricks field, Winkler County: 1, 2, 247e, 896b, 1225, 1649, 1675a Henrietta field, Clay County: 1216b, 1632 Hercynian folding, Trans·Pecos Texas : 44 . Hess formation. See Permian formations. Hickory sandstone. See .Cambrian for­ mations. Hidalgo County: 387a, 421, 546b, 673a, 1014, 1488, 1613a, 1684, 1_841a, 1844a High Island salt dome: 641b High Plains: 881, 1661 Hill, R. T. : 300 Hill County: 10, 3'82d, 391, 515. 803, 1219, 1232, 1652 The Geology of Texas-Subject lndex 981 Hill Creeh: heda. See Pennsylvaniap for­mations, Millaap Lake.­ historical geology: 6', 70, 246, 517, 578, 73(, 836, 1077, 1312, 1386 history geologic investigation : 734 oil fields in .Mexia and Tehuacana fault zones: 969 petrolemn: 76& Hocldey County: 42, 471, 1086 Hockley aalt dome: 32, 239, 420, 1596 Hog Cieek shale. See Pennsylvanian for­mations, Caddo Creeh:. Hog .Mountain sandstone. See Pennsylva­nian formations, .Mineral Wells. Holloman terrace: 1444d Home Creek limestone. See Pennsylva­nian formations, Caddo Creek. Hood County: 9, 803, aos, 1652, 1673, 1759& • Hopkins County: 382j, 470, 609, 844, 1186a, 1219, 1232, 1652 Hordes Creek limestone. See Permian formations, Admira!. horizon markers, paleontological: 7(8, 1800 Horse Creek. See Pennsylvanian forma­tions, Strawn. Houston County: 379, 416, •so, '61, •'70, 471, 606, 569, 668a, 904, 905, 1016, 1219, 1652, 1687a, 1844.a Howard County: 76b, 221b, 236b, 236d. 471, 674, 1652 Hudson Bridge limestone. See Pennsylva.­nian formations, Graford. Hudspetb County: 44, •6, 66, 56b, 89, 91, 331, 432b, 1007. 1035c, 1304, 131', 1521, 1522b, 1549 Hueco bolson, El Paso quadrangle: 1U2 Hueco limestone. See Pennsylvanian for­mations. Hueco .Mountains: 89, 91, 97a, 122, 510e, 1312 Hull aalt dome: 32 human artifacts, Pleistocene : 282, 1444d, 1'55 human remains, Lagow sand pit: 1455 Humble oil field. Harris County: 417, 1345 Hunt County: 356e, 358, 382j, 803, 8((, 1232, 1652 Hutcliinson County: 42, 78, 410b, 625a. 854b, 865&, 18'ia ice crystals, fossil : 1628, 164 7 ichnology: 1121, 1452 Ideal gypsum. See Permian formations, Blaine. identification, aids to geologic forma­tions: 1653 ldolo lsland well. Wilcox formation: 509 igneous dikes, Bandera County: 398 intrusions: 994 rocks, occurrence: 53, 1'5b, 188, 267, 433, 617, 636, 648, 722, 736, 757, 900, 917. 936, 97 4a. 992, 1007. 1009, 1014, 1160, 1161, 1162, 1180, 1219, 1312, 1314, 1378, 1442, 1444a. 1525c, 1625, 1638, 1641, 1652, 1686, 1803 imbibition of rocks : 773 indexes: 392b, 630, 1716c, l 716d, 1716e, 1716f, 1724, 1768 Indian Creeh:. See Pennsylvanian forma.­ tions. Strawn. Indian maunds: 1729 Indio formation. See F.ocene formations. industry, steel : 272 lnsecta. See paleontology under systems. interior aalt domes: 1252 Invertebrata. See paleontology under BYBtemS. Iredell meteorite, Bosque County: 268, 546 Irion County: 408, 1477 iron ore: 116, 169, 170, 172, 180, 274, 340, 342, 452, 454, 460, 461, •72, 483, 489, 506, 514, 530, 709, 714, 781, 880, 902, 903, 908, 909, 910, 1000, 1005, 1170, 1171, 1172, 1185a, 1189, 1191, 1212, 1216a, 1219, 1378, 1460, 1464, 1479, 1641a. 1705, 1818, 1842, 1846 (87) (14) Ivan limestone. See Pennsylvanian for­mations, Tbrifty. .Tack County: 33b, 58b, 82, 141a, 247, 342, 380, 510f, 549, 650, 936h, 1152b, 1215, 1219, 1227, 1228, 1274, 18'8, 1403, 1650, 1652, 1752, 1753a, 1853 .Jacksboro limestone. See Pennsylvanian formations, Caddo Creeh:. ' .Tackson County: 668a, 127 4. 1841& .Tackson group. See Eocene formations. .Jacksonville area, Cherokee County, · soil survey : 1844a .Jagger Bend limestone. See Permian for­mations, Belle Plains. .Jasper County : 415, 470, 506, 654, 1219, 1652 .Tasper Creek beds. See Pennsylvanian formationi¡, Graford. .Jeff Davis County: 44, •6, 104, 723, 1013b, 1014, 1080a, 1444f, 1652 .Jefferson County: 3, 66, 249a. 398a. 416, 490, 664c, 705, 804, 806, 811, 905, 909, 952, 954, 1022, 1197, 1219, 1303, 1320a. 1570, 1650, 1652, 18'la, 1841b, 184'& .Tenninga gas pool, Zapata Connty: 1406 .Ti!D Hogg County: 40, 97b, 421, 625a, 884, 885, 1613a, 1787a. 1838a Jim Wells County: 421, 1841a .Johnson, R. H.: 1'28 Johnson County: 9, 10, 421, 808, 1282, 1790 .John Ray dome: 624, 627, 670 .Tones County : 247, 1105b, 1595a, 175llb, 1853 .Juraasic: lOOb, 828, 334, 736, 792, 978, 1052, 1053, 1330, 1652, 1674& correlation: 146, 148, 618a, 673, 791, 1052, 1293, 1522& formations .Malone: 46, 328, 331, 944, 1522c .Morrison: lOOb, 1522a paleogeography : 146, 148, 33.¡, 978, 1293, 1382b, 1382g, 1385a. 1761c paleontology : 144, 299, 328, 331, 38le, 944, 1052, 1758 stratigraphy: 46, 146, 148, 828, 831, 458. 913d, 1047, 1052, 1053, 1288&. 1293, 1622b, 1522c, 1674a Kansas-Texas Permian correlation: 93 kaolin: 530, 1245, 1S78, 1378a, 1652 kaolinite. Brazos County: 58 Karnes County: 40, 16lb, 421, 1477, 1652, 1841& Kaufman County: 35lb, 415, 544, 662, 803, 906, 1060, 1232, 160lc, 1743 Keechi Creek limestone. See Pennsylva­nian formations, .Mineral Wells. Keechi salt dome, Anderson County : 244, 843, 1252 Kemp, .Mrs. A. H. : 624 Kendall County: 1186a, 1477, 1841a Kenedy County: 421, 1613a 982 The University of Texas Bulletin No. 3232 Kennedy, William, memorial to: 90la Kent County: 1633, 1775a Kent section, Culberson County: 474 Kerens, Navarro County, diamond· drill­ ing: 423 Kerr County: 1814b, 184la Kiamichi formation. See Cretaceous for­ mations. Kickapoo Falls limest.one. See Pennsyl­ vanian formations, Millsap Lake. Kimble County: 896a, 896b, 1234e, 1814b, 184la King County: 247, 854a, 1853 Kinney County: 889a, 994, 1009, 1086c, 1295a, 1477, 1628, 1639a, 1650, 1652, 1688b, 184la Kleberg County : 421, 952 kleinite: 1360, 1361 Knox County: 83a, 537a Lacasa area, Eastland County: 1352 laccoliths: 1009 Lafayette formation. See Pleist.ocene for­ mations. Lagarto formation. See Miocene for­·mations. LaGrange, Fayette County, meteorite: ll<í5, 1708, 1709 Lake Austin, Travis County: 1592a, 1594a, 1595 Jake deposits: 46 Lake Kemp limest.one. See Permian for­ mations, Lueders. Lake Pinto sandstone. See Pennsylva­ nian formations, Mineral Wells. Lak96~ichland fault, Freestone County : Lake Trammel sandstone. See Permian . formations, Whitehorse. Lamar County : 105, 38lc, 515, 609, 803, 844, 1186a, 1232, 129la, 1292a, 1320a, 1353, l 707a, 1844a Lamb County: 42, 471, 1086 laminated structure: 1662, 1663, 1672 Lampasas County : 82, 449, 80.3, 1227, 1228, 1403, 1471, 1563, 1574, 1650, 1652, 1673, 1703g Lampasas cut plain: 11, 16 Lanoria formation. See pre-Catnbrian formations. Lapara formation. See Plioeene forma­ tions. Lar~~ide thrusts, Trans-Pecos Texas: Laramie group. See Cretaceous forma­tions. Laredo district, Webb County: 97c 896 1078, 1844a ' ' Larremore area, Caldwell County: 1716 LaSalle County: 267b, 416, 421, 1013b, 1013d, 1488, 1652, 1841a · 1848 (375G) ' Lavaca County: 40, 421 1844a laws, mining: 1201a ' Lazy Bend member. See Pennsylvanian formations, Millsap Lake. lead ~6Jiº· 172, 1171, 1172, 1203, 1219, Lee County: 23, 413, 421, 470 569 668a 1488, 1687a, 1707a, 1841a: 1844a ' Leon County: 378, 382k, 415 470 606 1232, 1525e, 1687a ' ' ' Leon~ formation. See Pleistocene forma­ t1ons. Leo~~8.formation. See Permian forma- Lesher, C. E.: 1846 leveling resulta: l055b, 1055c Lewisville formation. See Cretaceous formations. Liberty County: 32, 46a, 68, 75, 143, 143b, 386a, 415, 897a, 1270, 1278a, 1488, 1650, 1753b, 1841b lignite. See also coa!. analyses of: 506, 845a, 1015, 1215, 1218, 1378 briquetting: 1218, 1806 east Texas: 170, 454, 460, 470, 471, 506, 575, 983, 1200, 1206, 1216a, 1460, 1565, 1846 (83) (87) (91) (96) (10) occurrence and production: 80, 296b, 412d, 709, 837b, 983, 1011, 1185a, 1189, 1200, 1214a, 1215, 1218, 1219, 1402, 1557, 1652 pseudo-igneous rock and baked shale from burning: 1011 utilization: 87, 464, 840a, 983, 1819 lignitic stage. See Eocene formations. lime-making plants : "i245 limest.one: 8, 11, 12, 14, 16, 167, 515, 1003, 1074c, 1219, 1311, 1378, 1378a, 1402, 1444g, 1636, 1652, 1789, 1790, 1839, 1840 Limestone County: 76b, 358, 359, 365, 370, 38lc, 415, 470, 506, 542, 548a, 662, 665a, 860, 964, 965, 969, 992a, 1060, 1193, 1219, 1232, 1255, 1263, 1444e, 1501, 1802, 1816; 1817 Lipscomb County: 42, 56b, 1841a Lissie formation. See Pleistocene forma­ tions. Live Oak County: 32, 40, 421, 510, 572a, 884, 1033b, 1113a, 1596b 1841a Llano-Burnet region. See ';,,1so Central ~~~~ral region i 140, 1172, 1254, Llano County : 59, 77, 84a, 138a, 27 4, 604, 710, 711, 715, 716, 717, 718, 719, 720, 721, 828, 829, 868, 947a, 1029, 1148, 1170, 1171, 1172, 1212 1219 1343, 1367, 1368a, 1471, 1525c,' 1545a; 1563, 164la, 1650, 1673, l 702a, l 702b, ~~~r:· 1103b, 1103e, 1703g, 176ld, Llano Estacado: 5a, 42, 314, 343, 346, 415a, 472, 873, 913e, 913h 1065a 1358, 1478, 1567a, 1605b, "¡7Í3a ' Llano River: 1848 (44) Llano series. See pre-Catnbrian forma.­ tions. Llanoria: 7, 16, 936b, 1113, 1115, 1134, ~~~!~· 1382f, 1385b, 1695b, 1761e, Llanoria-Ozark area: 1090 Lockhart _field, Caldwell County: 3 loess, vertical weathering: 1410 Lohn shale. See Pennsylvanian forma­tions, Thrifty. Lonsdale, J . T. : 188 Los Olmos oil field: l 787a Lost .Creek sh'!-1e. See Permian forma.­t1ons, Admira!. Lost Lake salt dome, Chatnbers County · 1711 . Lot~ ~alk. See Cretaceous formations. Lou1s1ana, Mesozoic : 18, 1691 Loup. Fork beds. See Pliocene forma.­ t1ons. Loving County: 56b, 432b 913a 1619a 1847 • • • Lower Cretaceous. See Cretaceous. Lubbock County: 42, 471, 1035c 1841a 1844a ' ' Lueders formation. See Permian forma­ tions. The Geology of Texas-Subject Index Lufkin area, Angelina County: 1844a Luling-Burdett wells, Cibolo fault: 164 Luling oil fteld, Caldwell and. Guadalupe counties: 164; 165, 165a, 728a, 896a, 1262, 1312, 1412 Luling-Powell fault zone: 69b, 1693, 16lló Lundberg method of prospeeting: 1815 Lynch Creek. See Pennsylvanian forma­ tions, Strawn. Lynn County: 42, 471, 1086 Lytle limestone. See Permian formations, Arroyo. -Lytton Springs oil fteld, Caldwell Coun­ ty: 164,_188, 267, 1444a mackintoshite, Llano County: 718 Madill-Denison area : 844 Madison County: 415, 506 magnesite, Winkler County : 1013a magnetic deelination tables: 120la magnetometer investigations: 268, 874b, 994, 1513, 1514, 1515, 1525, 1649 Main Street formation. See Cretaceons formations. Malakoff image, Henderson County: 1482 Malone formati¡m. See Jurassic forma­ tions. Malone Mountains: 55, 328, 331, 944, 15'a2b Mamm~Iia. Listed as Vertebrata under paleontology of systems. man, Pleistocene: 283, 284 Manford fault : 164 manganese: 645. 648, 1074c, 1190, 1324 Mangum dolomite. See Permian forma­ tions, Blaine. mapping, geologic, 834 maps. See individual areas and systems. Marathon basin: 44, 47, 396b, 510e, 936, 1254, 1435 Marathon fold, west Texas: 672, 990 Marathon formation. See Ordovician for­ mations. Marathon uplift: 44, 56a, 936a, 936g,1254, 1442 Maravillas chert. See Ordovician forma­ tions. marble: 996, 1185a, 1378, 1652 Marble Falls formation. See Pennsy)vll­ nian formations. Marcy's expedition: 119, 1176 Marion County: 180, 415, 460, 470, 905, 1059, 1219, 1232, 1343, 1448, 1650 . Marion formation. See Permian forma­tions. marine movements. See paleogeography. m1trine Wilcox. See Eocene formations. Markham fteld, Matagorda County : 32, 63a, 1606a mar), ana]yses of: 1378 Marlin chalk. See Cretaceous form1ttions. Marlow formation. See -Permian forma­ tions. Martín County: 471, 1847 Martín Lake limestone. See Pennsylva­ nian formations, Graford. Mason County: 274, 402, 1105a, 1148, 1219, 1471, 1477, 1490a, 15.ft;a, 1568, 1601, 164la, 1673, 184ia mastodons. See Pliocene and Plelstocene, paleontology, Vertebrata. Matagorda County: 32, 143b, 421, 625a, 645, 913a, 952, 1219, 1896b, 1606a, 1650, 1795, 1796, 1841a, 1841b Maverick County: 8b, 97b, 406a, 568a, 678, 578a, 647a, 713, 714, 936, 1013b, 1215, 1219, 1292a, 1541, 1613a, 1627, 1681, 1707&, 1758a, 1841a Maxon sandstone. See Cretaceous forma­tiop.s. Maybelle Iimestone. See Permian forma­tions, Lueders. McCamey, sulphide poisoning at: 1813 McCaulley dolomite. See Permian forma­tions; Blaine. McCulloch County: 82, 274, 449, 1215, 1228, 1343, 1403, 1471, 1673 McKittrick Canyon: 201 McLennan Coun~y: 10, 11, 240, 421, 515, 680a, 682, 803, 1093, 1094, 1168, 1219, 1232, 1257, 1320a, 1841a, 1844a McMullen County: 39, 40, 267b, 416, 421, 510, 884, 1033b, 1113a, 184la, 1848 (376G) Medicine Lodge formation. See Permian formations. medicated waters. See also Mineral springs: 997 Medina County: 161b, 237, 267a, 421, 470, 510, 889a, 992, 1009, 1013b, 1016, 1031, 1219, 1292a, 1407, 1477, 1650, 1841& Meek Bend limestone. See Pennsylvanianformations, Millsap Lake. Melikaria: 185 memorials Dumble, E. T.: 1486c Kenedy, William: 901a Udden, J . A.: 1841c Memphis sandstone. See Permian forma­tions, Whitehorse. Menard County: 27 4, 408, 652, 1403, 1471, 1477, 184la Merkel dolomite. See Permian forma­tions, Choza. mercury: 121, 410, 411, 413b, 428, 807, 837b, 845, 942, 988, 1074c, 1080a, 1185a, 1199, 1209, 1210, 1216c, 1219, 1221, 1284b, 1360, 1361, 1387, 1387b, 1456, 1597, 1618, 1629, 1646, 1662 effect of structure on accumulation of: 1629, 1648, 1651, 1654 metallurgy of: 511a, 1387a, 1387b minerals, from Terlingua, Brewster County: 194, 411, 612, 603, 722, 725, 807, 831, 832, 845, 941, 1143, 1202, 1204, 1205, 1208, 1211, 1360, 1862, 1368, 1368b, 1504, 1619, 1626, 1648 production statistics: 1846 (02) (06) ~06) (~7) (09) (10) (11) (17) Merr1man hmestone. See Pennsylvanian formations, Brad. Mesozoic. See also individual systems: ¡~¡¡/44, 458, 978, 1304, 1662, 1746a, paleobotany: 99, 105, 948a, 949, 1608 paleontology : 144, 1519, 1622c 1738, 1745b, 1758 • Ecbinodermata: 252, 258 Foraminifera : 861 Vertebrata: 214, 318 stratigrapby: 46, 1306 1521 metallic minerJl]s. See i~dividual metals. metallurgy, mercury: 511a, 1387a 1387b metamorphic rocks: 643, 1878 ' metamorphism: 962, 1206, 1808 meteor crater : 59a 116 meteori.c iron. · See 'meteorites. me~":l~es : 253a, 261, 262, 344, 354, Alpine, Brewster County: 1101 Ballinger, Runnels County :" 1155e Bluff, Fayette County: 240 Brazos River: 261, 262; 1033, 1378, 1464, 1479 984 The University of Texas Bulletin No. 3232 meteorites--eontinued Carlton, Hamilton County : 51lb, 8112, 853, 1378 Cedar, Fayette County: 1097 Davis Mountains, Jeff Davis County: 534 "Denton County," Brazos River: 1378, 1464 Deport, Red River County: 1174a Estacado, Hale County : 84 7. 848 Fayette County, Blufl', Cedar, La Grange: 1097, 1105, 1378, 1708, 1709, 1754, 1754a. Florence, Williamson County: 1008 Fort Duncart, Maverick County: 713, 714, 1378 lredell, Bosque County: 263, 546, 1378 J une 28, 1928 : 1420 Kendall County : 262 Kimble County: 1646 La Grange, Fayette County: 1105, 1708 Mart, McLennan County: 240, 1093, 1094, 1878 Oetober 1, 1917 : 1644, 1646 Odessa, Ector County: 59a, 115, 1100, 1415 Peek's Spring, Midland County: 1102 Pipe Creek, Bandera. County : 977 Plainview, Ha.le County: 1095, 1096 Red River: 1'79 Sal 1ngelo, Tom Green County: 1273, 37stony: 511b Travis County: 5llb, 1378 Troup, Smith County: 1099, 1656, 1657 Tulia, Swisher County: 1174 W~~~~a County: 261, 262, 1033, 1378, meteors. See meteorites. M""ia.-Groesbeck gas field : 1060 Mexia oil field, Limestone County: 542, 543a, 964, 965, 969, 1255, 1268 1501 1802, 1817 • • Mexia. fault zone: 543, 544, 964, 965, 969, 999, 1192a, 1255, 1263, 1326 Mexican boundary survey. See boundary survey. Mexico: 18, 781 mica: 1545&, 1545b micrology: 27, 197, 601, 1032, 1140, 1656. 1669, 1701, 1791 micropqJeontology. See pa.leontology un­ der systems. microscopic charaeteristics of formar . tions.. See micrology. m1croacop1c methods : 951, 1289 Mid-Continent oil fields: 140, 564, 1077, l344b, 1501 Paieogeogra.phy: 246, 1077 Midland County: 22lb, 432b 471 915 1102, 1418, 1619a, 1847 ' ' ' M~dway group. See Eocene formations. Milam County: 251a., 415, 421, 470, 506, 544, 637, 803, 1016, 1219, 1238b 1320a, 1574, 1838a, 1844& ' Milburn. shale. See P.ennsylva.nian for­ mations, Graford. Millica.n formation. See pre-Cambrian formations. · Milis County: .82, 449 808 1227 1228 1408 . • • • • Millsap forma.tion. See Pennsylvania.nforma.tions, Millsa.p La.ke. mineralogy. See minerals and the indi­ vidual minerals. · mineral production. See individual min· erais. mineral resourees. See natural resources. minerals, list of by counties: 1218, 1219, 1863b, 1485 by Jocalities: 171, 503, 1186, 134d, 1413, 1484, 1485, 1846 (83) (87). 1855 by minerals: 1413, 1485 . See also individual areas and mmerals. mineral springs: 530, 997, 1186a., 1219, 1341 mineral survey repe>rt: 1207, 1488a Mineral Wells formati<>n. See Pennsyl­ vanian formations. Mineral Wells gas field, Palo Pinto County: 1229b, 1450 Minerva <>il field, Milam C<>unty: 637 mines. See índividual minerals. Mingus shale. See Pennsylvanian forma.­ tions, Garner. mining laws: 120la Miocene. See also Tertiary : 466, 64lb, 1532b, l 76lc formations Fleming group: 32, 420, 506, 688, 1061a Lagarto: 38, 506, 1278a, 1278b Oakville: 88, 40, 105a, 506, 1033a, 1278b, 1613a. paleontology Foraminifera: 32, 35lb, 356c, 361, 38lb, 381e Vertebra.ta: 299, 303, 314, 582, 677, 683, 689, 897, 980, 1066, 1165b stratigraphy: 32, 196, 346, 420, 478, 571, 582, 638, 668, 672a, 1532b, l 76ld Mirando oil field, Webb County: 145, 896c, 1364, 1406 Mission field, Bexar Ce>unty: 1402 Mississippi emba.yment: 632a Mississippian : 1652 correlation: 89, 618a., 1131, 1364 formations Barnett: 1131, 1228, 1695b Boone: 601, 1354 microiC>gy: 601, 1364 paleogeography: 1382b, 1382g, 1694, 1761c paleontology: 635, 1364, 1496 stratigraphy: 91, 145, 247, 937, 1354, 1695b Mitchell Ce>unty: 153, 22lb, 518, 526a, 578, 665b, 689a, 1264, 1291, 1707& Mollusca. See paleontology under sys­ . tems. me>lybdenum: 1367, 1662 Me>ntague Ce>untY : 3ld, 58a, 82, 88a, 176, 221b, 342, 641&, 664, 1145a, 1215, 1219, 1227, 1228, 1843, 1606b, 1650, 1727e, 1828a, 1849a. Montgomery County: 32, 415, 506, 1686b, 1753b, 1844a, 1846 (11) Me>ntoya formation. See Ordovieian for­ mations. Monument Sprinirs formation. See Ordo­ vician formations. Moore Ce>unty: 42, 32lb, 410b, 525a, 854b, 1264, 184la Moran formation. See Permian forma.­ tions. Morris County: 180, 460, 470, 1219, 1282 1844a ' Morrison formation. See Jurassic for­mations. mosesite. See eJ,so mercury minerals : 194, 1368b MC>Ss Blufl' ealt dome, Liberty County : 68, 1270 . Me>tley County : 42 mounds: 38, 198, 886, 583, 641, 647d 813, 836, 1089, 109la, 1624, 1689' 1690, 1691, 1692, 1729 • Mount Sel.man formation. See Eoeene formabons. The Geology of Texas-Subject Index Mount Sylvan dome, Smith County: 1728 Mueneter arch, Cooke County: 247 Muenster field, Cooke County: . 675 "Munn's mystery" : 649 museum, geological: 1852 N acatoch formation. See Cretaceous for­ mations. Nacogdoches County: 3, 415, 417, 451, 460, 470, 506, 531, 1219, 1232, 1844a Nacogdoches field, Nacogdoches County: 3, 417, 451, 531 natural gas. See aleo oil and gas fields : 79, 97b, 123, 177, 183, 249b, :i2lb, 413b, 432a, 506, 552, 612, 632, 670, 854b, 885, 1060, 1062, 1155, 1159, 1185a, 1214b, 1216b, 1219, 130lb, 1346, 1356, 1449, 1450, 1501, 1579, 1597a, 1630, 1632, 1652, 1717, 1792, 1795, 1825, 1828 natural mounds. See mounds. natural regions : 87 8 natural resources. See also individual areas and resources: 169, 171, 412d, 413b, 763, 1074c, 1176, 1213, 1219, 1339a, 1340, 1363c, 1413, 1484, 1485, 1562, 1565, 183Sd, 1836 Navarro County : 15, 31c, 76b, 356e, 359, 373, 382k, 382j, 3821, 398a, 415, 423, 506, 525a, 726b, 727, 803, 961, 962, 963, 966, 967, 1060, 1062, 1077a, 1109, 1192a, 1232, 1238b, 1320a, 1444g, 1650, 1816, 1834a, 1844a Navarro formation. See Cretaceous for­ mations. ­N avaeota beds. See Pliocene formations. Neceesity sbale. See Pennsylvanian for­ mations, Graham. Neighbors, Maj. R. S., meteorite preeent­ed by: 1464 Neocene : 387a, 506, 661, 827c Neocomian sands. See Cretaceous forma­tions. Neozoic: 763 New Mexico, adjacent to Texas : 395 New Richland field, Navarro County: 963 Newton County: 416, 470, 506, 850a Nigger Creek field, Limestone County: 860, 1193 Nimrod Jimestone. See Pennsylvanian formations, Pueblo. Niobrara formation. See Cretaceous for­ mations. nitrat.is : 560a, 1006, 1035c, 1387 Nolan County: 247 nomenclature geograP.hie: 821 Wilcox and "Wilcox" : 629 North America: 176ld north-central Texas natural reeources · building material& : 34~ 342 casinghead gasoline: 1846 (17) (18) clays: 1841 (02). 1846 (92.) coa!: 35, 120, 170, 172, 454, 525a, 548, 1206, 1460, 1577, 1846 (83) (83-4) (87) (88) (91) (92) (09) (10) copper: 172, 340, 342, 346, 551, 573, 1216, 1302, 1374, 1846 (83--4) gypeum: 340, 342, 1549, 1846 (91) iron : 340, 342 natural gaa : 1449 oil and gaa: 3, 58b, 140, 141, 244a, 245a, 247b, 249d, 400, 525a, 568, 564, 689, 640. 901, 987, 989, 1064, 1155, 1198, 1256, 1258, 1325, 1449, 1501, 1695a, l 727b, l 727c, 1730, 1731, 1753b water supply : 340, 342, 457, 611, 614a, 780, 1086b, 1336 paleogeography: 140, 22lb, 203, 245, 503, 1234a Pennsylvania.n-Permia.n well correla­ tions : 879 physiography: 120, 457, 538, 761, 1017, 1038, 1041, 1055, 1176, 1241, 1476a, 1597 sedimentation : 1234a soils: 1841a etratigraphy Cretaceous: 325, 1064, 1449 Ellenburger: 1064, 1403 Pennsylvanian: 5, 81, 83a, 107, 172, 176, 178, 207, 220, 247, 247b, 249d, 257, 598, 611, 620, 639, 1064, 1133, 1145a, 1227, 1228, 1234a, 1362, 1385, 1398b, 1449, 1465, 1577, 1582, 1583, 1606b, 1673, 1695b, 1761d, 1854 Permian : 5, 85a, 96, 178, 207, 216, 220, 22la, 221b, 247, 247a, 255, 257, 316, 840, 341, 346, 349, 467, 610, 611, 622, 1064, 1302, 1353b, 1385, 1577, 1605, 1695b, 1718, 176ld, 1854 structure: 140, 178, 247, 257, 563, 564, 598, 639, 640, 858b, 1064, 1255, 1258, 1352, 1405, 1449, 1673. 1693, 1695 well data : 879, 1403 northeast Texas c:leep wells: 1116, 1117 map: 609 natural resources clays : 1319, 1320 iron ores: 180, 460, 514, 880 · natural gas: 612, 1450 oil and gas: 543, 844, 859, 888, 1530, 1834b road material : 7 50 water supply: 472, 609, 731, 1284b, 1575 Pªlmeography: 753, 774, 788, 1116, physiography : 460, 538, 731, 761, 774, 1017. 1055, 1675 salt domes : 244, 898, 1728, 1834b soile: 1575, 184la stratigraphy Cretaceous : 9, 174, 175, 182, 825, 383, 392, 521, 541, 542, 543, 608, 609, 643a, 731, 732, 742, 746, 750, 753, 772, 788, 840, 844, 859, 964, 1088, 1118b, 1114, 1141, 1232, 1389, 1398b, 1530, 1534, 1574, 1575, 1577a, 1601a, 1679, 176ld Quaternary : 609 Tertiary: 392, 460, 542, 543, 609, 753, 964, 1604, 1728 ­ structure: 17 4, 392, 542, 643, 609, 788, 840, 844, 859, 964, 969, 1117, 1826, 1540, 1607, 1698, 1695, 1834b temperature measurement: 1284b water-laid volcanic rocks: 1353 North Leon limestone. See Penneylvanianformatione, Graham. northweet Texas : 56b, 842, 848, 1005 paleogeography : 1694 physiography: 42, 353, 537a, 761, 779, 1017, 1054, 1476a soils: 1841a, 1844a stratigraphy Cretaceoue: 346, 1017, 1038 Miocene: 846, 478, 582 986 The University of Texas Bulletin No. 3232 northwest Texas-eontinued stratigraphy-continued Permian: 85a, 216, 255, 346, 31)4a, 622, 623, 1184 Pleistocene: 200, 343, 346, 478, 682, 1070, 1652 Pliocene: 346, 478, 682, 1070 Triassic: 85a, 216, 394a, 448, 918e structure: 175, 255, 256 water supply: 614a, 1181, 1182 novaculite: 44, 936c, 1378 Nueces County: 387a, 421, 678a, 952, 1276, 1277, 1278a, 1488, 184la, 1844a Nueces quadrangle, Edwards County: 794 Nueces River: 1848 (44) Oakville formation. See Miocene forma­ tions. Oatman Creek granite. See pre-Cam­ brian formations. Ochiltree County: 42, 56b, 1841a Ogalalla formation. See Pliocene forma,. tions. oil and gas. See also separate fields: 3, 34a, 76a, 78, 83, 188, 245a, 247e, 267, 335b, 486, 525a, 643, 685a, 632, 641, 692, 706, 811, 846, 1059, 1062, 1074c, 1186a, 1198, 1199, 1219, 1306, 1346, 1413, 1449, 1691, 1596b, 1641, 1660, 1693, 1695, 1696, 1761, 1834b aecumulation, effect of structure: 69, 76, 241, 249a, 249e, 527, 537, 726, 990, 1009, 1144a, 1251a, 1382e, 1444a, 1598, 1650, 1693, 1695, 1720 analyses of: 630, 963, 964, 1022, 1030, 1303, 1377, 1499, 1600, 1600a, 1598 distillation from sediments : 49 geology of: 67, 424, 625a, 1144a, 1602 migration of: 1322a refining: 397, 519 relation to fixed carbon ratio: 648 reserves : 33c, 72, 76b, 83, 1272, 1300, 1591a, 1700a, 1846 wel! spacing: 1814 Ojo Bonito intrusive: 53 Oklahoma adjacent to Texas: 83a, 173a, 174, 176, 606, 614a, 788, 1115, 1146a, 1444d Oldham County: . 42, 66b, 471, 126la, 1264, 1841a Oligocene: 101, 622, 721c, 1113a, 1532b, 1761e correlation : 624, 572a formations Catahoula: 40a, 101, 161b, 421, 596, 970d, 1031b, 103Sa, 1601a Frio: 38, 40, 40a, 421, 672a, 970d, 1033a, 1690a, 1613a Gueydan group: 30, 40, 40a, 572a, 970d, 1613a paleontology: 522, 103lb, 1061a, 1166b Anthozoa: 1687a Foraminüera: 32, 361b, 356c, 366d, 381b, 382b stratigraphy: 114, 196, 420, 421, 606, 622, 524. 571, 696, 638, 668, 672a. 1624a, 1596b, 1652, l 761d Ohnos 'formation. See Cretaceous forma­ tions. oolites: 1598a Oran sandstone. See Pennsylvanian for­mations. Graford. Orange County : 32, 415, 1110, 1841b Orange dome, Orange County: 1110 g~~~!i!a~ome, Fort Bend County: 646 correlation: 618a formations Alsate: 936a Chazy: 1020a, 1444c, 1814a ~~rf~~ñ!~rga~~on: 1312, 1314 Marathon: 936a, 1652 Ordovician--continued formations-eontinued Maravillas chert: 936, 936a MontOya: 936b, 1107a, 1304, 1312, 1314 Monument Springs : 936a Woods Hol!ow: 936a paleogeography: 629a, 1382b, 1382g, 1437, 1761c stratigraphy: 44, 641a, 663, 936a, 936b, 936g, 1020, 1021, 1304, 1306, 1310, 1312, 1314, 1428, 1652, 1695b, 176ld, 1814b Ordovician-Mississippian contact: 601 ore veins, origin of : 1567 . ores. See individual resources. Organ Mountains: 873 organic remains. See paleonto]ogy under systems. Oriana gypsum. See P.ermian formations, Peacock. orogeny. See aleo separate areas: 625, 1137, 1677 Ostracoda. See paleontology under sys­tems. Ostreidae. See paleontology under sys­ tems. Otterville formation. See Pennsylvanian formations. Ouachita facies. See Paleozoic rocks of Ouachita facies. Ouachita Mountains : 77 4, 838, 1116, 1117a, 1254 Ouachita syncline: 16, 246, 936g, 1134, 1385b, 1439 overthrusting. See structure under indi­vidual areas. Ozan formation: See Cretaceous forma­tions. Ozarkian. See Cambrian. ozokerite: 1376 Packsaddle schist. See pre-Cambrian for­ mations. Paint Rock beds. See Permian forma­tions, Lueders. Palangana salt dome, Duval County : 60, 66 paleobotany. See paleobotany under sys­tems. paleoclimate: 216a, 220, 22la, 334, 1136, 1287, 1622d, 1760 paleogeography. See also pa!eogeography under systems and areas: 1382g, 1383, 1385b, 1761b, 1761c paleontology. See also paleonto!ogy un­der systems : 1646 Paleozoic. See also individual systems: 618a, 1077, 1113, 1264, 1761c Paleozoic rocks of Ouachita facies: 1116,nn· 1117a, 1254, 1433, 1439, 1441, Palestine dome, Anderson County : 244, 543, 843, 1252, 1326 Palo Duro basin : 623 Palo Duro beds. See Pliocene formations. Palo Pinto County: 36, 82, 247, 320b, 342, 364, 510f, 649, 561, 1064, 1186a, 1192, 1216, 1219, 1227, 1228 1229a 1229b, 1403, 1449, 1450, 1524.c, 1650• 1673, 1717, 1763a, 1853 ' Palo Pinto limestone. See Pennsylvanianformations, Graford. Paluxy formation. See Creta.Ceous forma. tions. Paluxy reservoir, Grayson County i 189 Pandale-Stone bend structure, Terre!J County: 966 Panhandle earthquake: 1267, 1667 igneous rocks: 433, 670 magnetometer survey : 1525 The Geology of Texas-Subject Index Panhandle--continued mapa: 78, 255, 616, 623, 1004, 1844a natural resources helium: 1366 natural gas: 79, 1356 oil and gas: 78, 264, 336b, 410b, 544a, 865, 855a, 1004, 1264, 1500, 1591a, 1695a, 1763b, 1813 water supply: 614a, 614b, 616, 1086b, 1181, 1182, l 713a paleogeography: 613, 623, 1694 physiography: 118, 537a, 614b, 615, 690, 1039, 1358, 1713a soils : 1841a, 1844a stratigraphy: 78, 22lb, 247a, 329a, 340, 342, 343, 346, 478, 613, 614b, 616, 616, 623, 627, 690, 912a, 1004, 1066a, 1070, 1141b, 1184, 1358, 1489 structure: 78, 256, 32lb, 433, 544a, 613, 618, 623, 1004, 1264, 1353c, 1356, 1489, 1490, 1693, 1696 Panhandle beds. See Pliocene formations. Panola County: 247e, 416, 460, 470, 506, 612, 612a, 643a, 1232, 1378, 1406, 1408 Parker, E. W.: 1846 (01-16) Parker County: 9, 33c, 82, l45b, 342, 366, 610e, 674a, 803, 1215, 1219, 1227, 1228, 1320a, 1394, 1398c, 1673, 1753a, 1853 Parks-Cottonplant structure, Eastland and Stephens counties : 6 Parks Mountain sandstone. See Pennsyl­ vanian formations, Thrifty. paraffin dirt: 61c, 159a, 1449& Parmer County: 42, 56b, 471, 1841a Pawpaw formation. See Cretaceous for­mations. pearls, fossil: 9, 1359 Peacock formation. See Permian forma­tions. pebbles, solution faceted: 167 Pecan Gap formation. See Cretaceous formations. Pecos County: 8, 12, 76b, 190, 190a, 22lb, 408, 410, 434a, 625a, 546a, 577, 648a, 650, 651, 707, 882, 896b, 936, 936h, 1013b, 1086c, 1104, 1219, 1259, 1315, 1675a, 1700c, 1712a, 1847 Pecos River valley: 656, 991, 1844 ( 44) Pedernales River valley : 891 Pelecypoda. See paleontology under sys­ tems. Pennsylvanian conglomerates : 82 correlation: 5, 89, 173a, 249d, 594, 618&, 879, 926, 1132, 1135, 1137, 1228, 1313, 1382a, 1384, 1385, 1495, 1723 Bend group: 692, 698, 839, 1130 methods used : 1723 microfaunas : 1135 north Texas: 1132 west Texas : 1313 erratics in: 56a, 935, 1435, 1675 formations Avis sandstone: 82 Belle City: 661 Bend group: 6, 33a, 244a, 247, 247a, 247e, 649, 576, 692, 593, 698, 599, 839, 923a, 1130, 1131, 1228, 1234e, 1490a, 1665, 1669, 1673, 1701 "Black Lime": 6, 516, 549 Brad: 449, 1227, 1228, 1296, 1398 Brazos sandstone: 82 Caddo Creek: 33b, 82, 449, 510e, SlOf, 1227, 1228, 1753a Caney: 650, 1675 Canyon group: 247, 247a, 4.&9, 561, 998, 1227, 1228, 1652, 1712, 1713 Cisco group: 133a, 221b, 247, 247e, 371, 380, 449, 561, 589a, 594, 649, 660, 651, 1228, 1635 Dimple: 66a, 930, 936, 1652 Gaptank: 44, 22lb, 510e, 650, 651, 924, 930, 936, 936h, 1643, 1652, 1753a Garner: 1227, 1228, 1229a, 1398c, 1763a, 1853 Glenn: 605, 649, 651 Graford : 33b, 33d, 82, 132, 145a, 342, 449, 510e, 1228, 1236, 1398b, 1398c, 1524c, 1584, l 727d, 1753a, 1853 Graham: 58b, 320a, 449, 5.JOe, 510f, 561, 650, 651, 1107b, 1138, 1227, 1228, 1234e, 1296, 1352, 1753a Harpersville : 449, 1228, 1584, l 753a Haymond: 44, 56a, 930, 935, 936c, 1435, 1652 Hueco: 394a, 59la, 913g, 92la, 933, 936b, 1312, 1314, 1652 Marble Falls: 141, 434, 510f, 1228, 1601, 1606b, 1753a Millsap Lake: 510e, 650, 1228, 1398c, 1753& Mineral Wells: 82, 320b, 1228, 1229a, 1398c, 1524c, 1753a, 1853 Otterville : 605 Pueblo: 449, 1228, l 727d, 1853 Smithwick: 1228 Strawn group: 16, 81, 247, 247a, 247e, 449, 510e, 510f, 549, 561, 923a, 1228, 1652 Tesnus: 56a, 930, 936, 1662 Thrifty: 82, 449, 510e, 510f, 1227, 1228, 1753a Wapanucka: 651 micrology: 1656 orogeny: 1137, 1677 paleobotany: 1005 paleoclimate: 216a, 22la, 11]16, 1760 paleogeogr_aphy: 97a, 145b, 246, 986, 987, 1091, 1133, 1234a, 1382b, 1382g, 1385a, 1495, 1694, 1723, 1761c paleontology: 610f, 693a, 630, 636, 635a, 650, 651, 673, 1005, 1041, 1132, 1138a, 1152b, 1228, 1330, 1456, 1496, 1624c, 1724 Brachiopoda: 642, 1382, 1713 Bryozoa: 998, 1138, 1138b, 1281 cat&togue: 1476b Cephalopoda: 131, 133a, 336, 660, 698, 863, 864, 866, 1107. 1107b, 1234, 1234c, 1234e, 1396, 1397, 1398, 1473, 1496 conodonts : 635, 635a, 1624c Echinodermata: 335a, 1476 Foraminifera: 95, 112a, 364, 366, 367, 369, 371, 372, 380, 381e, 610d, 510e, 661, 650, 1236, 1359a, 1440a, 1601, 1712, 1713, 1763a Gastropoda: 1251, 1461, 1465 Ostracoda: 320a, 408, 649, 661, 662 Pelecypod~: 556, 589a, 642, 1001, 1081, 1737, 1756 Porifera : 936h tracks: 1261 Vertebrata: 1138a, 1624e sedimentation: 81, 914, 923a, 1234, 1234a, 1398a, 1567a, 1722b, 1723 stratigraphy north-central Texas: 6, 6, 107, 172, 176, 178, 207, 220, 247, 247b, 249d, 267' 339, 432, 694, 698, 611, 613, 620, 639, 879, 891, 902, 1064, 1133, 1146a, 1172, 1227, 1228, 1234a, 1280, 1296, 1351, 1362, 1385, 1398b, 1449, 1465, 1492, 1554, 1672, 1677, 988 The University of Texas Bulletin No. 3232 Pennsylvanian-eontinued stratigraphy-, 841, 913a, 915, 918, 975, 1034, 1034a, 1034b, 1034c, 1035, 1035a, 1035b, 1086, 1185a, 1220, 1369, 1369a, 1369b, 1369c, 1378, 1418, 1525a, 1547, 1550, 1551, 1552, 1619a, 1620, 1631, 1635, 1639, 1657a, 1658, 1659, 1671, 1751, 1808, 1809, 1833, 1834, 1838, 1846 (23), 1847 potholes, etched: 1664 Potter County: 3ld, 42, 78, 79, 236d, 236e, 32lb, 471, 525a, 616, 625a, 627, 670, 854b, 1180, 125la, 1264, 1619a, 1841a Potter formation. See Pliocene forma­ tions. pottery. See clays. Pottsboro gas field, Grayson County: 177 Powell field, Navarro County: 726b, 727, 1192a, 1525b Pratt well, Webb County: 8Q2 pre-Cambrian: 396a, 1382g, 1423, 1424, 1438, 1545b, 1656, 1681b, 1703c formations Carrizo Mountain: 46, 1314 Lanoria quartzite: 396a, 1312, 1652 Llano series : 1703c Millican: 396a, 1314 Oatman Creek granite: 1525c Packsaddle schist: H 72, 1525c, 1652 Sixmile granite: 1525c Town Mountain granite: 1525c Valley Sprin,g gneiss: 1172, 1525c, 1652 stratigraphy : Central Mineral region: 271, 274, 1005, 1170, 1171, 1172, 1301a, 1330, 1525c, 1567a, 1681b, 1682, 1682a Red River uplift: 64la Trans-Pecos Texas: 46, 173, 1301a, 1304, 1306, 1310, 1312, 1682a Presidio County: 46, 130, 221b, 253a, 396b, 492, 723, 849, 943, 1035c, 1080a, 1207, 1214; 1219, 1249, 1292a, 1442, 1444b, 1563, 1623, 1846 (93) Preeton anticline,-Grayson County: 177 189, 1606b • producer gas : 1215 proration : 434a Proterozoic. See pre-Camhrian. Putnam formation. See Permian forma­ tions. Quanah gypsum. See Permian forma­ tions, Blaine. quarries, listed by loca!ities and prod­ucts : 1836 (12) Quartermaater formation. See Permian formations. Quaternary. See Pleistocene. Queen qity formation. See Eocene for­ Dlations. Queen formation. See Permian forma­ tions. quicksands: 184 quicksilver. See mercury. Quitman Mountaln: 46, 1522b Raccoon Bend field, Austin County · 143b radioactive minerals: 59 947a • railway guide, geologicaÍ: 1018 Rains County: 470, 1232, 1443 Rainy limestone. See Perm.ian forma­ tions, Arroyo. Randad.o oil field: 1613a, l 787a Randall County: 42, 471, 1619a, 1841a Ranger field, Eastland County: 432, 434, · 516, 549, 1296, 1352, 1450, 1526 . Ranger limestone. See Pennsylvaruan formations. Brad. rare earth minerals: 59, 77, 84a. 138a, 574, 604, 710, 711, 715, 716, 717, 718, 719, 720, 721, 828, 829, 947a, 974a, 1029, 1172, 1821 Rattlesnake beds. See Cretaceous forma­ tions. Reagan County: 76b, 269, 410b, 510d, 525a, 543a, 653, 694, 706, 880a, 895, 913a, 1017, 1019, 1020, 1020a, 1021, 130lb, 1322, 1414, 1421, 1425, 1428, 1444c, 1477, 1500, 1619a, 1700a, 1813, 1814a, 184lc, 1847 Real County: 1219, 1378a Recent Foraminifera: 351b, 381e, 950, 952 Gastropoda: 259a terrace deposits : 74 Vertebrata: l 720a, 1720b reclamation, Dallas County : 54 7 red beds: 41, 43, 50, 52, 86a, 146, 148, 220, 221b, 1293 Red Bluff formation. See Permian for­ mations. Red River County: 363, 373, 515, 521, 609, 1174a, 1186a, 1232, 1343, 1353, 15llc, 1601c, 184la, 1844a Red River syncline: 836 Red River up!ift: 58a, 140, 617, 64la, 902, 1254, 1693, 1695, 1814a Red River valley boundary dispute : 595, 824, 1410, 14i.Oa, 1411, 1597 physiography: 595, 824, 1055, 1410, 1476a, 1597, 1849a reef structure, Capitan limestone: 896b, 918, 919, 921, 936f, 1002 Reeves County: 44, 430, 432b, 1013b, 1035c, 1086b, 1243, 1259, 1304, 1477, 1707, 1844a refining. See oíl and gas, refining. Refugio County: 421, lOUb, 1488, 1596a, 1596b, 1597a, 1841a Refugio field, Refugio County: 1074b, 1597a Reiser oil field: 1613a Reklaw formation. See Eocene forma­tions. Relay Creek formation. See Permian for­mations. Reptiles. · See Paleontology, Vertebrata, under systems. reservoirs: 166, 1595a Reynosa escarpment : 97e, 525a, 546b, 884, 1018b, 1613a, 1695a, 1787a Reynosa formation. See Pleistocene for­mations. Richland field, Navarro County: 963, 966 Ricker bed. See Pennsylvanian formar · tions, Strawn. -· Rim Rock : 1661 Rio Grande embayment: 578, 826, 884, 1613a, 1625 Rio Grande valley. See also southwest Texas : 387a, 468, 546c, 656, 662, 673a, 794, 795, 799, 805, 913j, ll08, 1153, 1166, 1177, 1178, 1312, 1364, 1373, 1379, 1380, 1456, 1490b, 1606. 1610, 16~1. 1613, 1613a, 1625, 1636a, 1687. 1739, 1848 (44) Rios well, Caldwell County: 1409 Ripley formation. See Cretaceous forma­tions. ripple marks : 1395, 1642 road materials: 750, 992, 1147, 1149, 1324 991 The Geology of Texas-Subject lndex Robert Lee structure. Coke County: 87 Roberts Coup.ty: 42, 1841a Robertson County: 415, 470, 606, 664a, 666a, 668a, 906, 1016, 1186a, 1219, 1488, 1687a, 1844a Rochelle conglomerate. See Pennsylvanian formations, Graford. Rock Creek fossil lociility: 1165a, 1165b, 1614, 1615, 1616 rock fans: 877a Rock Hill limestone. See Pennsylvanian formations. Graford. rock salt. See salt. Roekwall County : 145b, 391, 644, 899b, 1169, 1183; 1232, 1535, 1844a Roeky )lfountain strueture: 526, 916, 1036, 1626, 1694 Roemer, F . V.: 672e, 1484a Roma antieline: 1613a Rough Creek. See Pennsylvanian forma­tions, Strawn. Royston formation. See Permian forma­tions, Peaeock. Runnels County: 87, 247, 320e, 432b, 449, 1403 Rusk County: 144a, 247e, 415, 460, 470, 506, 646b, 856d, 866h, 896e, 971, lllla, 1219, 1232, 1322a, 1512, 160lb, 1700d, 18S3g, 1844a Rush Springs member. See Permian for­mations. Whiteborse. Rustler formation. See Permian forma­tions. Rustler Springs sulphur deposits: 1243 Sabine County: 103, 379, 416, 470, 606, 664a, 664e. 72la, l 60lb, l 688e Sabine River: 1688& Sabine uplift : 247q. 861, 1124, 1126, 1248, 1675b, 1695a. l 709b Sacramento Mountains : 122 Saddle Creek shale. See Pennsylvanian formations. Harpersville. Saddlehorse gypsum. See Permian for­mations, Quart.erinaster. St. Mauriee formation. See .Eocene for­ mations. Salesville shale. See Pennsylvanian for­ mations, Mineral Wells. salines: 461, 506, 709, 960, 1167 salt : 69, 113, 286a, 340, 342, 386a, 393, 406a, 506, 666b. 668, 841, 1024, 1074c, 1194, 1196, 1219, 1304, 1306, 1378, 1592, 1596, 1662, 1808, 1833g, 1846 (8~) (12) salt domes. See Gulf Coast, salt domes, and individual domes. Salt Flat field, Caldwell County: 267a, 697. 728a, 896a, 1076, 1076 Salt Flat, Van Horn quadrangle : 1314 Salt Plain formation. See Permian for­ mations. San Angelo formation. See Permian for­ mations. San Antonio reg-ion. See Bexar County. San Augustine County: 416, 470, 506 San Carlos coal field, Trans-Pecos Texas : 1684, 1687 . San Jacinto County: 415. 606, 1763b San Jacinto River: 69a San Mareos area. See Hays County. San Marcos River valley: 164 San Miguel formation. · See Cretaeeous formations. San Patricio County: 418, 421, 686, 889, 952, 1278, 1278a, 1650, 1794, 184la San Saba County: 82, 247, 274, 369, 449, 464, 510f, 560a, 6~2, 693, 1036e, 1215, 1219, 1227, 1228, 1283, 1343, 1364, 1406, 1471, 1524e, 164la, 1650, 1673, 1703e, 1703g, 184la, 1844a San Saba mines : 1283 San Saba River : 1848 (44) sand and grave!. See also building ma­ terial: 1219, 1378, 1448, 1454, 1652 sand dunes: l , 823, 1410 sand rivers: 823 Sanders Bridge limestone. See Pennsyl­ vanian formations, Graford. sandstone. See also building material: 142, 1219, 1378, 1652 sandstone dikes: 899b, 1169, 1183, 1635 Santa Anna Braneh beds. See Permian formations, Putnam. Santa Anna shale. See Permian forma­ tions, Moran. Santa Rosa formation. See Triassic for­ mations. Santo limestone. See Pennsylvanian for­ mations, Garner. Santo Tomas coal, Webb County: 36 Saratoga chalk. See Cretaeeous forma­ tions. Saratoga field, Hardin County, 32, 62, 403b, 418, 495, 1126, 1127. 1669 Saxet gas field, Nueces County: 1276 Sehleieher County : 408, 14 77 Sehott-Avia.tors field, Zapata County : 1406, 1613a Seurry County : 236d . Seaman Ranch beds. See Pennsylvan1a.n formations, Brad. Sedwiek limestone. See Permian forma­ tions, Moran. serpentine : 188, 267, 268, 1009, 1378, 1444a, 1638, 1641 . . Seven Rivers format1on. See Perm1an formations. Shaekelford County : 82, 247, 696a, 651, 1145a, 1193a, 1216, 1219, 1228, 1449, l 727b, l 727e, 1853 Shadriek Mili. See Pennsylvanian forma­ tions, Strawn. Shafter district, Presidio County: 849, 943, 1214, 1623 Sheffield terraee, Croekett County: 991 Shelby County: 416, 460, 470, 506, 1091a, 1219, 1232, 160lb Sheridan formation. See Pleistoeene for­ mations. Sherman County : 42, 66b, 392a, 184la Sherman syneline, Grayson County : 177 Shields field. See Fisk-Shields field. Shimer formation. See Permian forma­tions. Sierra Blanca, El Paso County.: 1007, 1521, 1522b Sierra del Carmen : 44 Sierra Diablo Mountains: 33a, 122, 1314 Sierra Madera structure, Pecos County : 936 Sierra Madre structure·: ·827a, 827d Silurian eorrelation: 618a, 1019 Fusselman formation : 936b, 1312. 1695b paleogeography: 629a, 1382b, 1382g. 176le stratigraphy: 936b, 1019, 1020, 1021, 1312, 1444c, 1696b, 1662, 176ld silver: 172, 530, 849, . 943, 1201, 1214, 1219, 1283, 1562, 1623.-. 1626, 1652, 1846 (83) (87) (05) (09) (10) (11) (12) sinks : 38, 42, 1427 Sipe Springs field, Coml!nche · County :. 1699 992 The University of Texas Bulletin No. 3232 Sitting Bull Canyon: 122 Sixmile granite. See pre-Cambrian for­mations. Smith County : 415, 460, 4 70, 709, 855d, 855h, 905, 971, 992a, 1099, lllla, 1219, 1232, 1250, 1252, 1322a, 1657, 1728, 1833g, 184la, 1844a Smith-Ellis field, Brown County : 1554 Smithwick formation. See Pennsylvanianformations. · soils. See also individual areas: 199a, 484, 489, 1017. 1354a, 1477, 1841a, 1844a Solitario uplift: 44, 1249, 1486, 1442, 1444b, 1H4c solution, faceted limestone: 1636 Somerset field, Bexar County: 1402 Somervell County: 803, 1013b, 1462 Sonoran sea : 1382b, 1882g, 1386b Souixia: 1382b, 1386b Sour Lake field, Hardin County: 3, 418, 1341, 1342, 1426&, 1427 South Bend field, Young County: 141, 245 South Bend shale. See Pennsylvanian formations, Graham. South Bosque field, McLennan County : 11 South Dayton dome, Liberty County: 32, 143 South Medina field, Bexar County: 1402 south Texas: 135, 139, 472, 641, 699, 1610, 1613a, 1844a clay dunes : 260 magnetometer prospecting: 1514 natural resources alunite: 151 building stone: 454 clays: 413 grahamite: 469, 476 lignite: 470, 471 soili.~ter8:r:ply: 780, 1336, 1844a stratigraphy . crm~d°us: 135, 564, 194, 1590, 1681, Pleistocene: 1613 Tertiary:4oa, 135, 502a, 564, 672a, 970d, 1590, 1613a sout~~e.;it earthquake, July 30, 1925: southwest Texas: 122, 124, 139, 472, 494, • 771, 794, 807, 1577, 1687 1gneous rocks: 1625 natural resources asphalt rock : 1206, 1836 building material: 412, 1610 coa!: 105a, 412, 1206, 1378, 1610, 1739, 1846 (83--4) (86) (86) (87) (88) (92) (10) greensand: 646d oil and gas: 97b, 97c, 249e, 287 890 896, 967a, 1018b, 1167, 1631 '1610' 1626, 1695a, 1753b, 1838a ' ' water supply: 414, 1625, 1686, 1844a paleontology: 579a physiography: 494, 526, 771, 814, 815, sof~~\8~\~4, 1178, 1373, 1380, 1606 stratigraphy Cretaceous: 135, 181, 468, 480, 647a, 782, 896, 1625, 1684, 1686 Qhaternary: 416, 494, 1078, 1610, 1612, 1652, 1686 Tertiary: 416, 468, 494, 896, 1590a, 1610, 1611, 1686 structure: 416, 793, 1531, 1625, 1686 spacing of oil wells: 1814 Spanish explorations: 827b Sparta formation. See Eocene forma­ tions. Specks Mountain limestone. See Pennsyl­ vanian formations, Thrifty. Spindletop field, Jefferson County: 3, 66, 249a, 954, 1570 Spring Creek. See Pennsylvanian forma­ tions, Strawn. springs. See also mineral springs : 12, 248, 1055a, 1086b, 1086c Spur, Dickens County, deep boring: 1635 Squirrel Creek formation. See Eocene formatioDs. Staff limestone. See Pennsylvanian for­mations, . Graford. Staked Plains. See also Llano Estacado: 236d, 305, 308, 343, 579a, 758, 1358 Standpipe limestone. See Permian for­ mations, Arroyo. Starr County: 32, 40, 97c, 421, 546b, 884, 1613a, 1787a, 1841a statistics, mineral production: 1841, 1846 Steen dome, Smith County: 1250, 1252 Stephens County: 6, 82, 145a, 22lb, 246, 342, 364, 369, 380, 432, 510f, 527. 549, 651, 967a, 1064, 1215, 1219, 1227, 1228, 1258, 1403, 1524c, 1673, 1753a, 1853 Sterling County : 482b Steussy shale. See Pennsylvanian forma­ tions, Millsap Lake. Stockwether · limestone. See Pennsylva­ nian formations, Pueblo. stone. See building material. Stonewa!J County: 247, 467, 1185, 1553a, 1863 stratigraphy. See under systems and areas. stratigraphy, text on: 631 Stratton Ridge dome, Brazoria County: 33 streams, gazetteer of: 1848 ( 448) strontium minerals : 712 structure. See separate areas. subsidence: 877, 108_0, 1268, 1269, 1271, 1426a, 1427, 1445, 1502 subsurface methods: 951, 1289 sulphide poisoning: 1813 sulphur: 57, 63, 69, 84, 113, 143b, l63a, 195, 415b, 420, 708, 830, 831, 832, 837b, 913, 1024, 1034a, 1074c, 1185a. 1199, 1217, 1219, 1222, 1239, 1243, 1245a, 1304, 1307, 1317, 1494, 1599, 1652, 1726, 1795, 1799, 1824 Suman, J. R. 549 Sutton County: 367, 408, 1841a Sweetwater dolomite. See Permian for­mations, Cloud Chief. Swenson gypsum. See Permian forma­tions, Peacoek. Swisher Coti_!lty: 42, 471, 1174, 1841a Taff, J. A.: 549 tale: 1172 Talpa limestone. See Permian forma­tions, Clyde. Tarrant County: 9, 10, 31, 3la, 31c, 377, 381a, 38lb, 513b, 674a. 726, 803, 1060, 1232, 1234b, 1242a, 1395, 1448, 1453, 1595a, 1675, 1788, 1789, 1844a Taylor County: 247, 624, 1105c, 1128, 1768a, 1841a, 1844a, 1853 Taylor formation. See Cretaceous forma.­ tions. Tecovas formation. See Triassic forma­tions. tectonics: 48, 56 The Geology of Texas-Subject Index Tehuacana fault zone. See Mexia-Tehu&­ cana zone. temperature gradients. See geothermal data. Terlingua area, Brewster County: 15, 194, 512, 603, 722, 725, 807, 808L 830, 831, 83~ 845, 941, 942, 986, 1143, 1202, 1204, 1205, 1207' 1208, 1209, 1210, 1211, 1360, 1362, 1368, 1442, 1504, 1618, 1619, 1645, 1648, 1654 Terlingua beds. See Cretaceous forme.­ tions. Terlingua fault: 1626 Terlingua quadrangle: 1207 terraces: 6, 38, 1585 Terrell County: 42, 248, 955, 1732 Terry County: 471, 1086 Terry field, Orange County : 32 Tertiary. See also systems, as Eocene. correlation: 146, 148, 501, 618a, 1065a, 1144, 1165, 1293, 1691 Grand Gulf series: 387a, 106la, 1688c micrology : 1656 orogeny : 1284a paleobotany: 57a, 100, 102, 108, 191, 949, 1226, 1608, 1707a paleunty: 415, 506, 905, 1320s. 184la, 1844a Udden, J. A.: 184lc IDrieh, E. O.: 44, 1172, 1304, 1312, 13H unconformities: 597, 600 undulations in clay deposits : 386 United States: 834, 1516 unit operation of oil fields: 970, 1018d University deep well, Reagan County. See also Big Lake field: 1421 University land: 94, 991 Upshur County: 247e, 415, 460, 470, 855d, 971 lllla 1232, 1322a, 160lc, 1833g Upson formati~n. See Eocene formations. Upton County: 76b, 190a, 913a, 1477, uran\~!!· ~~~~rals. See rare earth min· erals. · Uvalde County: 45, 145b, 253a, 421, 470, 502a, 544, 578, 578a, 654, 889a, 994, 1009, 1013b, 1018b, 1113a, 1160, 1206, 1219, 1292a, 1295a, 1442, 1477, 1613a, 1639a, 1685, 1686, 1688b, 184la Uvalde formation. See Pliocene for· mations. Uvalde quadrangle: 253a, 1686 Vale formation. See Permian formations. Valera shale. See Permian formations, Belle Plains, Valley Spring gneiss. See pre-Cambrian formations. Val Verde County: 192, 889a, 1035e, 1086c, 1323, 1324, 1477, 1531, 1628, 1647, 1814b, 1841& Van field, Van Zandt County: 73, 247e, 970, 993, 1018d ' Van Horn quadrangle: 936b, 1314, 1545a, 1545b Van Horn sandstone. See Cambrian for­ mations. Van Zandt County: 73, 76b, 247e, 415; 460, 470, 665b, 905, 970, 993, 1018d, 1219, 1232, 1250, 1?52, 1601e vegetation : 385, 878 Vertebrata. See paleontology under s:va­ tems. vertebrate localities: 1026, 1165a, 1351 vertebrate types in University of Texas museum: 1119 Victoria County: 421, 1477, 1488, 1841a, 1844a Vidrio formation. See Permian forma­tions. Village Bend limestone. See Pennsylva,. nian formations, Mineral Wells. voleanie ash: 506, ll13a, 1288a, 1353, 1613a, 1633 volcanie dust: 412, 466, 482, 1617 volcanism: 39, 46, 765, 793 Wagon Yard gypsum. See Permian for­ mations, Blaine. Waldrip limestone. See Pennsylvanian form~tions, Harpersville. Walker County : 161b, 415,. 506, 1378a Waller County: 415, 1753b, 184lb Walnut formation. See ·Cretaceous for­ mations. Wapanucka formation. See Pennsylva­nian formations. Ward County: 190a, 913a, 1619a, 1671, 1847 Ward gypsum. See Permian formatioiis, Cloud Chief. · The Geology of Texas-Subject lndex Washington County: 143b, 267a, 413, 421, 552, 696, 842, 967, 968, 980, 1841a, 1841b, 1844a Washita group. See Cretaceous forma­ tions. Waskom gas field, Harrison County: 632 water absorption, porous rocks: 609, 773 water analyses. See analyses, water. water supply. See also separate areas: 42, 454, 1336, 1652, 1848, 1849 Watts Creek shale. See Permian forma­ tions, .Moran. Wayland shale. See Pennsylvanian for­ mations, Graham. Weatherford formation. See Permian for­mations. Webb County: 36, 40, 46a, 97b, 97c, 145, 251a, 296b, 412, 421, 470, 525a, 540, 543a, 572a, 668a, 697a, 884, 886b, 892, 896c, 1018b, 1078, 1215, 1216d, 1219, 1320a, 1364, 1406, 1407, 1488, 1613a., 1632, 1687, 1838a, 184la, 1844a Weches formation. See Eocene forma­ tions. Wellington formation. See Permian for­mations. Wells Creek district, Anderson County: 843 well spacing: 1814 Weno formation. See Cretaceous forma­tions. Westbrook field, Mitchell County : 518 West Columbia dome, Brazoria County: 32, 61, 196, 418 West Point dome, Freestone County: 404 west Texas core drilling: 1808 geologic conference in: 1837 magnetometer survey: 1515 maps: 97, 122, 190, 723, 807, 841, 881, 1001, 1034, 1833g, 1844a micrology : 1289 natural resources : 1559 asphalt: 1685 gypsum: 120, 336, 614, 724, 1152a oil and gas. See also separate fields : 45, 410b, 510c, 525a, 895, 967a, 989, 1198, 1253, 1301, 1301b, 1675a, 1712a, 1727a, 1727c, 1814 potash. See potash. salt: 393, 841, 1194, 1195, 1808 water supply: 120, 457, 472, 479, 690, 780, 785, 881, 1086b, 1086d, 1181, 1241, 1323, 1336, 1478, 1881 paleogeography: 146, 148, 841, 1293 physiography: 120, 538, 779, 810, 1017, 1036, 1038, 1041, 1054, 1241 1589 soils: 184la, 1844a ' stratigraphy: 454, 517, 578, 739, 841, 926, 1253, 1814b Cenozoic: 305. 841 Cretaceous: 45, 395, 480, 789, 841, 913j, 1253 Jurassic: 146, 148, 1293 Tertiary: 200, 775 Triassie: 7, 146, 148, 340, 342, 841, 913i, 1253, 1293 structure: 122, 190, 201, 672, 841, 1253, 1693, 1695, 1763, 1765, 1787 Wharton County: 421, 678a., 184la, 1841b Wh1s'lri.aCounty: 78, 525a, 537a., 854b, Whipple's reconnaissance: 118, 642, 1039 White, D.: 592, 936 White. J. c.: 549 White Point gas field, San Patricio County : 418, 889, 1278, 1794 Whitehorse formation. See Permian for­mations. Wichita conglomerate. See Permian for­ mations. Choza. Wichita County: 58a, 83a, 208c, 249c, 694, 611, 64la, 1035, 1145a, 1216d, 1258, 1410, 1411, 1449, 1492, 1595a., 1630, 1632, 1673, 1745b, 1749c, 1800a, 1803, 1844a, 1853 Wichi.ta group. See Permian formations. Wichita Mountains: 836, 1254 Wilbarger County: 58a, 83a, 208c, 550, 858b, 967a, 1258, 1444d, 1492, 1606b, 1727c, 1844a Wilbarger Creek. See Pennsylvanian for­mations, Strawn. Wilberns formation. See Cambrian for­mation::;. Wilcox formation. See Eocene forma­tions. Wiles area, Stephens County : 432 Wiles limestone. See Pennsylvanian for­mations,. Graford. Willacy County: 421, 1613a, 184la, 1844a Williamson County: 31c, 187, 188, 421, 525a, 803, 1008, 1009. 1113a, 1219, 1320a, 1366, 1376, 1377, 1430, 1444a, 1574, 1639a, 1641, 1645, 1650, 1838a, 1844a Williams pool, Callaban County : 728 Willis area: 1844a Willow Point limestone. See Pennsylva­nian formations, Graford. Wilson County : 103, 421, 869d, 899b, 1210, 1477, 1841a, 1844a Winkler County: 1, 2, 76b, 19-0a, 410b, 432b, 546a, 896b, 1013a, 1225, 1671, 1675a, 1712a, 1787, 1847 Wise County: 9, 33d, 82, 129, 132, 342, 583. 803, 936h, 1215, 1236, 1320a, 1398a, 1398b, 1524c, 1759a, 1853 Wizard Wells Iimestone. See Pennsylva­ nian formations, Brad. Wolfcamp formation. See Permian for­mations. Wolfe City member. See Cretaceous for­ mations. Wood County: 415, 460, 470, 905, 1016, 1186a, 1232, 1528a, 1601c Woodbine formation. See Cretaceous for­ mations. woods, fossil: 1187, 1226 Woods Hollow formation. See Ordovician formations. Woodville area: 1844a Woodward formation. See Permian for­ mations. Word formation. See Permian forma­ tions. Wortham field, Freestone County: 726c, 966 Wortham-Mexia earthquake: 1444e Wrather, W. E. : 549­ Wylie Mountains: 919a, 1314 Yancey structure, Medina County: 992 Yates field, Pecos County: 8, 12, 190, 190a, 410b, 434a, 525a, 577, 648a, 707, 1104, 1315, 1675a, l 712a Yeager e.lay. See Eocene formations. Yegua formation. See Eocene formationB­ Yoakum County: 42, 56b, 471 Yoast fleld, Bastrop County: 267a, 268, 1444a Young County: 44a, 58b, 82, 133a, 141, 22lb, 245, 245a, 247, 342, 364, 366, 369, 371, 380, 510e, 510f, 549, 589a, 651, 665b, 967a, 1152b, 1215, 1219, 996 The University of Texas Bulletin No. 3232 Young County-eontinued 1227, 1228, 1229c, 1258, 1320a, 1343, 1403, 1476b, 1492, 1678, 1727b, 1853 yttrium minerals. See rare· earth min­erals. Zapata County : 40, 97b, 525a, 668a, 884, 886b, 1406, 1407, 1613a, 1632, 1878a, 1804, 1888a, 184la Zavala County: 45, 421, 470, 578, 578a, 872a, 1009, 1013b, 1018d, 1444a, 1613a, 1686, 1688b, 184la zinc: 646, 1171, 1219, 1634, 1652, 1846 (15) Zwolle field, .Sabine Parish: 513 INDEX TO VOLUME 1 The references in this index are to pages in this volume. For subject index to Texas geology with references to the bibliography, see pp. 966-996. Abilene formation: 169, 175 Acme dolomite: 168, 179 Adams Branch limestone : 104, 111 Admira! formation: 146, 170, 171, 172 Aguja formation: 271, 474, 481, 605, 509, 517 Alabama Blulf: 657, 663 Albany group : 144, 17 4 Albian: 271, 284, 291, 293, 295, 301, 327 Alexandrian: 84 algae: 59 Algonkian system : 31 Alibates dolomite: 167, 243 Alsate formation: 70, 77 Alta formation: 146, 164, 165 Altuda member: 154 Amarillo region : 82, 85 Amarillo uplift: 49, 97, 123 Americus limestone: 140, 141, 143 Ammobaculites midwayensis zone: 567, 569 ammonite fauna: 179 ammonites: 173 Anacacho formation : 270, 445, 456, 467, 468, 517 Ancestral Rockies: 22 Anderson County: 394, 493, 534, 557, 598, 636, 638, 652 Andrews County: 247 Angelina County: 622, 629, 632, 638, 652, 653, 656, 658, 659, 665, 666, 668, 672, 676, 698 anbydrite : 161, 301, 303 Ankareh formation : 241 Annona formation: 270, 456, 457, 462, 474, 482 Antelope Creek sandstone: 105, 109 Antlers sand: 270, 300, 301, 306, 307, 311, 320, 323, 328 Apache Mountains: 156 Appaiachia: 67 Aptian: 271, 284, 293, 294, 295, 301, 327 Arbuckle formation: 88 Arbuckle region : 69 Arbuckle uplift: 141 Arcadia Park: 270, 425 Archeozolc sY•tem : 20, 27, 31 Archer County: 123, 141, 171, 172, 180, 192 Argovian : 256 Arizona : 246, 280 Arkadelphia formation : 270, 480 481, 483, 495 • Arksnsas: 409, 412, 440, 444, 456, 457, 458, 480, 481, 482, 483, 492 Arkansas novaculite: 87 Armstrong County: 251 Arroyo formation: 14.6, 169, 174, 175 artesian water: 259, 314, 327, 348, 401 Asher sandstone: 140 Aspermont dolomite : 168 Atascosa County: 598, 618, 621, 637, 652, 657. 666, 669, 683, 686, 687. 694, 703 Aurora limestone: 325 Austin County: 741, 742, 762 Austin formation: 263, 270, 294, 405, 407, 417, 422, 4391f, 444, 452 "Austin marble": 338 Austin-Taylor contact: 440, 447, 448 Avis sandstone: 103, 114 "Azoic": 17 Bailey County: 247, 358 Balcones fault zone: 137, 139, 187, 268 Balsora limestone: 105, 110 Bandera County: 122, 319, 515 Barnett formation: 91, 92, 93, 96, 97, 99 Barringer Hill: 53 Barstow formation : 242 Barton Creek limestone: 106, 338 "Basement sands": 284, 319 Bastrop County: 533, 558, 566, 567, 57 4, 575, 576, 577, 578, 580, 584, 585, 586, 593, 594, 595, 596, 598, 601, 602, 621, 625, 629, 636, 640, 645, 647, 657 batholiths : 34 Baylor County: 169, 171, 173, 175, 358, 776, 778 Bayl0r Mountains: 63, 75 Beach Mountain : 63, 75 Bead Mountain limestone: 169, 173 Beaumont clay: 530," 781, 787 Beaverburk limestone: 169, 173 Bee County: 682, 752, 754, 760, 787 Beekmantown series: 70, 74, 76, 77, 83 Belknap limestone: 103, 115 Bell County: 85, 89, 130, 132, 134, 187, 316, 323, 330, 331, 336, 339, 341, 343, 350, 362, 366, 367. "372, 373, 376, 381, 384, 390, 394, 396, 398, 399, 411, 418, 423, 430, 434, 445, 448, 450, 456, 463, 464, 796 Belle Plains formation : 146, 169, 171, 173, 180 Bend arch: 73, 94, 123 Bend group: 49, 91, 93, 99, 100, 116, 117, 120, 122, 123, 125, 126 Berinington limestone: 382 Benton formation : 263, 427 bentonite: 669, 672, 690, 716, 719, 722, 734, 804 Bethany gas field: 301, 492, 493 Bexar County: 128, 130, 188, 298, 348, 394, 399, 401, 445, 449, 450, 467, 496, 533, 545, 554, 556, 557, 563, 574, 575, 584, 585, 586, 595, 596, 598, 601, 602, 603, 604, 605, 608, 796 bibliography: 819 Big Bend : 481 Big Fork formation: 130, 131, 191 Big Horn Mountains : 69 " Big Lime": 174, 177, 182, 184 Big Valley bed: 105, 109 Bigford formation : 607, 608, 619 Bingen formation : 265, 458 Bissett formation : 146, 148, 153, 186 Blach Ranch limestone: 103, 114 Black Hills: 69 Black Land belt: 401 Black Mountain : 354 B!ack Prairie region : 444 Blaine formation : 146, 166, 168, 177, 178, 181, 184 Blalock sandstone : 86 Blanco beds: 765, 766, 774 Blanco County: 83, 86, 122, 132, 188, 192, 332 Rliss formation : 44, 56, 62, 69 Blossom formation: 270, 440, 441 , 443, 444, 458 Blowout Mountain sandstone: 168 998 The University of Texas Bulletin No. 3232 "Blue Blutfs division": 455 Blutf beds: 286, 297 Blutf Bone bed : 169 Blutf Creek shale: 104, 114 Boehms, E. F. : 183 Bone Canyon member : 157 Bone Springs member: 157, 162, 181 Bonham clay: 270, 413, 423, 428, 440, 441, 443 Bonneterre formation: 58 Boone Creek limestone: 105, 110 Boone formation : 90, 92 Boquillas flag: 271, 436 Borden County: 250 Bosque County: 124, 126, 330, 341, 350 1'oulders: 120 Bowie County: 557 Brackenridge Park: 448 Brad formation: 99, 104, 110, 111, 112 Brannon limestone: 106, 107 Brazoria County : 707, 708, 732, 734, 738, 742, 748, 783, 789 Brazos County: 657, 665, 668, 669, 670, 726 Brazos River sandstone : 106, 108 Brazos River valley : 585 Breckenridge limestone: 103, 114 Brewster County: 119, 130, 305, 351, 361, 392, 394, 402, 426, 451, 505, 799, 802, 803, 807 brick and tile clays : 519 Bridge, J osiah : 60, 71 Bridgeport coal: 105 Bridgeport limestone: 105 Britton : 270, 408, 425 Brooks County: 682 Brooks dome: 262, 491 Brown County: 66, 73, 80, 96, 107, 111, 115, 193, 306, 308, 312, 316 Brown Creek sandstone: 105, 109 Brownstown formation : 270, 456, 457, 474 Brownwood shale: 104, 112 Bryan County, Oklahoma: 350 Buckley Survey: 18 Buckrange: 474 Buda formation: 270, 277, 363, 390, 391, 396tf, 401, 408, 431, 436, 455 Buda-Eagle Ford contact: 423 Butfalo Creek shale: 105, 109 Butfalo Hill sandstone: 169 Buhrstone formation : 606, 607, 608 building stone: 760 Bull Creek sandstone: 105, 109 Bullard dome: 262 Bullwagon dolomite: 169, 176, 181 Bunger limestone : 104, 113 Bunter sandstone: 244 Burditt mar): 270, 407, 441, 442, 449tf Burleson County : 628, 636, 663, 665, 668, 681, 683 Burnet County: 53, 122, 197, 321 " Burnt limestone" : 396 Burnt Branch bed: 106, 109 Butler clay: 530, 575, 587 Butler dome: 262, 491, 557 Bybee, H. P.: 183 Caballos formation: 79, 87, 89, 118, 121, 305 Caballos Mountain: 88 Caddell member: 530, 680, 685, 686, 693, 695 Caddo Creek formation : 99, 104, 110, 112, 114. 370, 492 Caddo limestone: 370 Caddo oil field, Louisiana: 489, 492, 495 Caddo sand: 492 Caldwell County: 45, 80, 130, 132, 188, 197, 303, 394, 567, 575, 576, 579, 584, 625 Caldwell Knob oyster bed: 530, 574, 575, 576, 577, 580 Calhoun County: 789, 795 caliche : 755, 759, 778, 782, 785, 791 Callaban County: 80, 96, 115, 123, 171, 172, 173, 174, 197, 331, 345 Callaban Divide : 324, · 336, 345 Callovian : 256 Calvert Blutf clay beds : 580, 586, 588 Cambrian system: 27, 49, 51, 59, 61, 66, 67, 72, 122, 130, 309 Cambrian-pre-Cambrian contact: 37 Camden series: 572 Cameron County: 732 Cameron Park: 447 Camp County: 629 Camp Colorado limestone: 103, 115 Camp Creek shale: 103, 115 Camp Springs formation: 242, 244, 249 "Campagrande" formation: 285, 309, 353 Campanian : 271 Campbell sand : 492 Canadian system : 57 Cane River sand: 656 Caney shale: 93, 97, 127 Canyon group: 102, 104, 110, 113, 127, 137 Cap Mountain formation: 56, 58 Capitan formation: 146, 148, 152, 153, 156-159, 181, 182, 186 Capps limestone: 105, 109 Caprina limestone: 338 Caprotina limestone: 315, 360 Carboniferous: 90, 130, 139, 148 Cárdenas shale : 263 Carlsbad !imestone: 160 Carrizo formation: 37, 38, 530, 586, 607, 608, 610, 611, 612, 634 Carrizo Mountains: 38, 163 Carrizo Mountain formation: 38, 39, 42, 54, 63, 163 Carson County: 50, 198 Cass County: 628, 629, 636, 649 Castile formation: 146, 156, 158, 159, 160, 161, 182, 186 Catahoula formation : 530, 634, 710 Cayugan series: 84 Cedar Park member: 3·31 Cedarton shale: 104, 111 celestite: 302, 303 Cenomanian: 271, 401, 420, 425, 436 Cenomanian-Turonian boundary: 437 Cenozoic formations: 180, 519 Cenozoic lands and seas : 24, 248 Central Basin Platform: 52 Central Mineral region: 30, 34, 57, 61 central Texas : 463ft' Chaffin beds: 103, 114 Chalk Blutf: 679 Chambers County: 702 Channel sandstone: 244 Chappel formation : 91, 92, 96 Chatfleld gas sand: 495 Chattanooga group: 88, 91, 95, 96 Chazy series: 77, 80, 83 Cherokee County: 491, 493, 534, 614, 620 622, 623, 629, 630, 632, 636, 638, 539' 648 • Cherry limestone: 104 chert: 87 cherty dolomite: 71 Chester group : 91, 92, 94, 97 Cheyenne formation : 269 Chickasha formation: 178 The Geology of Texas-Index to Volume I 999 Chickashaw heds : 672 Chico Ridge Jimestone: 105, 111 Childress County : 168 Childress dolomite and gypsum: 168, 179 Chinati Mountains: 145, 163, 185 Chinati series: 164 Chinle formation: 241, 243, 244, 249, 251 Chireno oil fie)d: 650 Chisos beds : 513 Chisos Mountains: 513 Chisos quadrangle: 452 Chispa Summit: 271, 426, 431 Chita member: 530, 715, 717 Chittim anticline: 266, 500 Choetaw fault: 137 Choetaw limestone: 382 Choza formation: 146, 168, 174, 176 Chupadera formation: 160, 162 Chusa member: 630, 716, 717 Cibolo formation: 145, 146, 164, 165 Cieneguita formation: 146, 164 Cincinnatian series: 70, 75, 79, 83 Cisco group : 102, 103, 113, 127, 170 Citronelle group: 530, 749 Claibome group : 530, 606 Clarendon beds: 765, 766, 774 clays: 519, 545, 553, 570, 680, 694, 697, 600, 675, 677, 749, 795 Clay County: 47, 66, 123, 141, 171, 172, 198 • Claytonville dolomite and gypsum: 167, 180 Clear Creek Jimestone: 104 Clear Fork group: 165, 168, 171, 174, 181, 184, 185 Cloud Chief formation: 146, 161, 177, 179, 182, 184 Cloud Chief-Whitehorse formation: 167 Clyde formation: 146, 169, 171, 178 coa!: 627 Coa! Measures: 170, 179 coa! series: 467 Cochran County: 247 Cockfield Ferry heds : 607, 667 Coekfield member: 656, 668, 676 Coetas formation : 765 Coke County: 176, 178, 331, 346 Coleman-Albany group: 170 Coleman County: 80, 96, 171, 198 Coleman JunctiOn limestone: 140, 170, 172 Coleman Jimestone and shale: 170, 173 Collier shale:. 67 Collin County: 137, 428, 429, 444, 462, 463, 489 Collingsworth County: 50, 167, 168 Colorado: 369 Colorado County: 732, 742, 748, 748, 752, 754, 759, 761, 762, 784, 797 Colorado River valley: 109, 586 Colquitt formation: 271, 441, 462 Columbia, :Mexico: 22 Columbia sands : 782 Coma! County: 130, 515 Comanche County: 80, 96, 107, 201, 308, 312 Comanche Creek shale: 105, 109 Comanche-Gulf contact: 401 Comanche-Gulf unconformity: 274 Comanche Peak formation : 270, 302, 323, 325, 327, 328. 334ff, 342, 347, 353, 355, 357 Comanche series: 187, 248, 272ff, 303, 306, 316, 317, 330, 335, 336, 345, 409 Concho County: 80, 171, 203 Concho divide: 30 Conchos Valley: 286 concretions: 661, 673 Coniacian : 271 conodonts : 87 Cook Mountain series: 530, 608, 609, 610, 611, 612, 635, . 661, 655, 656 Cooke County: 47, 66, 67, 74, 80, 85, 123, 125, 203, 350, 367, 372, 373, 376, 378. 383, 389, 394, 409, 412, 413 Cooledge chalk : 466 Coon Mountain sandstone: 103 copper: 40, 53, 294, 806, 808 Cornish sandstone: 141 Cornudas Mountains : 354 Corrigan sandstone: 711, 712, 715 · Corsicana: 270, 460, 464, 480, 485, 492 Coryell County: 80, 206, 321, 323, 330, 336, 341, 350, 351 Cost zone: 663, 665 Cotter fossils: 72 Cottonwood Creek bed: 105, 109 Cottonwood limestone: 140 Cow Creek member: 314, 315 Cox formation: 271, 284, 285, 295, 296, 309, 321, 327, 328, 352, 353 Crane County: 247, 249, 330 Cretaceous system: 24, 64, 86, 93, 107, 122, 139, 147, 153, 155, 163, 180, 186, 187, 259ff, 404, 514, 516 Crockett County: 80, 83, 122, 182, 206, 247, 319, 330, 351, 355 Crockett formation: 530, 611, 612, 634, 655 Crosby County: 250, 767, 775 Croton gypsum: 167 Crystal Falls limestone: 103, 115, 140 Cuchillo formation: 271, 292ff, 318 Culberson County: 161, 799, 802, 803, 807, 808 Cundiff limestone: 104, 112 Cushing limestone: 141 Custer formation : 244 cycads: 261, 319 cystids: 59 Dagger Flat anticlinorium: 76 Dagger Flat formation : 56, 64, 66 Dake, C. L. : 71 Dakota group: 241, 258, 283, 400, 402, 409, 412 Dallam County: · 283, 410, 412 Dallas County: 130, 188, 258, 329, 350, 362, 410, 417, 422, 424, 429, 433, 445, 447, 463 Danian: 517 • Darst Creek field: 394 Davis formation : 59 Davis Mountains: 399, 402, 427, 431, 472 Dawson County: 247 Deepkili shale : 7 6 Delaware basin: 184 Delaware Mountains: 37, 152, 156, 158, 161 Delaware Mountain formation: 146, 157, 158, 162, 181, 182 Delaware Plateau: 158 Del Norte Mountains: 121, 147, 152 Del Río formation : 384, 387 Delta County: 460, 461 Dennis Bridge limestone: 106, 107 Denton County: 47, 67. 80, 123, 125, 137, 206, 306, 310, 335, 350, 367, 372, 373, 378, 379, 384, 385, 389, 394, 395, 396, 397, 410, 414, 416, 420, 425 Denton formation : 270, 363, 368, 372, 373, 381. 385 De Queen limestone: 301, 305, 316, 318 Devils Den limestone: 105, 111, 112 Devils River limestone : 325 1000 The University of Texas Bulletin No. 3232 Devonian novaculite: 79 Devonian system: 64, 86, 89, 130 DeWitt County: 730, 731, 752, 754, 755, 760, 761 DeWitt formation: 728 Dexter formation : 270, 408, 410, 411, 414, 415 "Diablo" formation : 39 Diablo lllountains: 84, 98, 116, 127, 152, 157, 185 Diablo Plateau: 37, 53, 63, 86, 89, 94, 115, 145, 162 Dickens County : 242, 246 Dickerson beds: 106, 107 dicotyledonous leaves: 400 Dierks limestone : 316 dikes: 34 dikes and sills: 515 Dimmit County: 501, 534, 585, 586, 614, 615, 616, 618, 619, 620, 621, 626 Dimple formation: 99, 117, 118, 120, 121 dinosaurs : 320 "Dinoeaur sand" : 310 Discorbis zone: 530, 709 Divesian: 256 Docklj.lll group: 24lft Dog Bend limestone: 106 Dog Creek formation : 178 dolomite: 70, 176 dolomitic limestone : 86 Dolores formation: 241 Dothan limestone: 170, 172 Double lllountain group : 165, 167, 175, 177, 181, 185, 253 Dripping Springs formation: 242 Duck Creek formation: 270, 277, 323, 339, 341, 344, 351, 352, 356, 357' 358, 360, 363, 365, 366ff, 368, 369, 381, 402 Dugout lllountain : 149 Dumble Survey : 18 Duncan formation: 178 Durango sand : 270, 456, 467, 463, 465 Duval County : 71311, 730, 732, 742, 752, 764, 787 Eagle Ford formation : 263, 270, 277, 360, 381, 398, 401, 405, 407, 410, 417, 419, 422tt Eagle lllountains: 37, 163 "Eagle Pass beds": 467 Eagle Pass coal: 502 East lllountain shale: 106, 108 East Texas embayment: 265, 381, 393, 403, 409, 411, 491 East Texas oil field : 417 Eastland County : 46, 80, 96, 207 Eastland limestone: 104 Eaton lentil : 653 Eau Claire formation : 58 economic products : 53 Ector chalk: 441, 443 Ector County: 2'7 Edens sand : 463, 494 Edwards County: 80, 95, 96, 122, 125, 210, 307, 317, 339 Edwards formation : 270, 302, 323, 324, 326, 327, 328, 332, 334, 336, 33811, 347, 348, 355, 366, 465, 516 Edwards Plateau: 268, 309, 329 346 365 361, 388, 399 ' ' • El Abra formation: 263 347 El Capitan Peak: 157, 169 El Paso County: 799, 802, 807 El Paso fo"'!'&tion : 63, 74, 83, 367, 394 El Paso reg10n : 20, 43, 69 70 74 75 82--84, 88 ' ' ' ' Ellenbnl'ger group: 56, 68, 61, 69, 70, 92, 93, 310 Elliott Creek shale: 106, 109 Ellis County : 130, 188, 420, 426, 433, 440, 464 Elm Creek limestone: 170, 172, 173 Elmdale shale: 140, 143 Elstone Jimestone: 539, 550 Eminence formation: 56, 61, 71 Eocene system: 137, 531 Eolian Jimestone: 103 Equus beds: 782, 797 Erath County: so; 96, 107, 211, 308, 312 Escondido formation : 270, 407, 467, 481, 500, 502, 516 Eskota gypsum: 167, 180 Etholen eonglomerate: 285, 295, 309, 353 "Exogyra arietina marl": 386 extrusives : 513 Falls County: 85, 130, 188, 466, 463, 465, 466, 486, 491, 496, 537, 657 Fannin County: 82, 130, 188, 301, 303, 409, 413, 423; 428, 441, 443, 444, 458, 459, 479 Fant member : 630, 716, 717, 719 Farias beds : 270, 481, 501 Fayette County: 665, 669, 679, 681, 683, 692, 694, 697, 698, 699, 713, 714, 724, 730--732, 754 Fayette formation : 634, 666, 667, 678 Finis shale: 104, 112, 114 Finlay dome: 163 Finlay limestone: 271, 309, 328, 352, 353, 368 fish bed conglomerate: 442 Fisher County: 177, 211, 776 Flabellum conoideum zone: 567, 569 "Flag limestones" : 338 Flatwoods beds : 556, 572 Fleming group: 530, 727 F!oyd County: 247 Foard County: 47, 66, 67, 74, 80, 82, 85, 123, 175, 211 Foraker limestone: 141, US foresta: 519, 583, 584, 594, 597, 629, 668, 675, 697 Fort Bend County: 742, 789, 790 Fort Bliss : 62 Fort Peña Colorada: 76 Fort Peña formation : 70, 77 Fort Riley limestone: 143, 144 Fort Sill formation: 56, 59 Fort Stockton: 367 Fort Worth basin: 266 Fort Worth formation: 270, 363, 365, 367, 370ff fossil wood : 87 Fox Ford bed : 105, 109 Fox Bilis: 263 Franconian : 59 Franklin County : 486, 557 Franklin lllountains: 27, 43, 55, 62, 75, 84, 98, 116, 145, 162 Fredericksburg group: 263, 270, 277, 299, 301, 304, 322ff, 347 Freestone County: 491. 537, 557, 569, 566, 584, 587' 588. 693 Frijo!e limestone: 159, 160, 181 Frio County: 485, 500, 551, 558, 576, 615, 618, 621. 622, 637 Frio formation : 530. 703 Fulda sandstone: 169 fuller's earth : 519, 690, 697, 698, 717,719, 722 . Fusselman formation: 84, 86, 88, 94 Gaines County: 247, 357 Galveston County: 732 Gasconade formation: 67, 70, 71 The Geology of Texas-Index to Volume I 1001 geologic section: 183 Georgetown formation : 270, 277, 309, 344, 346, 354, 360, 366, 371, 384, 391 Gaptank formation: 99, 117, 121, 186, 148, 149 Garner formation: 106, 108 Garza County: 246, 247, 251, 356 Gargasian : 293, 294 Gillespie County: 46, 66, 93, 122, 212, 302, 304, 306, 309 Gillespie formation: 269, 301, 309, 314, 319, 322 Gilliam member: 153 Girvanella zone : 59 glacial inftuences: 757 Glass Mountains: 144, 145, 146, 156, 166, 181, 184, 185 glass sand: 619 glauconite: 58, 485, 545, 553, 554, 562, 641, 650 . glauconitic division : 480 Glen Rose formation: 269, 270, 274, 284, 291, 295, 296, 299, 302, 304-309, 313, 315lt, 322, 515 Glen Rose-Cuchillo : 284 Glen Rose-Walnut contact: 323 Gober formation: 270, 443, 456ff, 479 ·Goliad County: 752ff Goliad formation: 530, 740, 741, 750, 754, 782 Gonzales County : 636, 657, 665, 669, 682, 683, 699, 713, 714, 7al Gonzales ·limestone: 104, 113 Goodland formation : 270, 307, 311, 328, 334lt, 366 Goodnight beds: 765, 766 Gordon: 105 Graford formation: 99, 104, 110, 111 Graham formation: 99, 103, 110, 112, 113 Grand Gulf sandstone: 710 Grand Gulf series : 666 granite: 31, 33, 56 granitic boulders: 164 Grape Creek shale and limestone : 169, 178 graphite: 27 graptolites: 76 Gray County: 50, 212 Grayson County: 80, 82, 83, 130, 189, 306, 311, 329, 335, 349, 362, 372, 378, 375, 379, 383, 384, 387. 388, 394, 401, 409, 413, 417, 424, 429, 432, 440, 444, 445, 447 Grayson formation: 270, 860, 863, 368, 881lt, 401, 408, 411, 420, 428 greensand: 421 greensand division : 480 Gregg County: 417, '40, 629, 630 Grimes County: 608, 668, 699, 713, 730, 738, 741 Grindstone Creek beds: 106, 107 Groesbeck dolomite: 168 Guadalupe County: 533, 534, 575, 585, 586 . Guadalupe Mountains: 37, 152, 156, 181 Guadalupe Mountain group : 146, 159, 181, 184 Guadalupe-Delaware-Apache Mountains : 145 Guadalupe Point: 157, 158, 159 Gueydan group : 530, 700 Gulf Coastal Plain: 129, 268, 491 Gulf-Comanche contact: 277 Gulf series: 400ff Gunsigbt limestone: 103, 113, 114 Guthrie dolomite : 168, 179, 18~ Gym formation: 162, 163 gypsum: 160, 162, 163, 166, 303 Hale County: 248 Hall County: 179, 358 Hamilton County: 213, 320 Hanna Valley shale: 105, 109 Hardeman County : 177, 179, 181 Hardin County: 707, 7 42, 7 48, 787 Harper formation: 178 Harpersville formation: 99, 103, 113, 115, 144 Harris County: 682, 702, 704, 707, 742, 791 Harrison County: 595, 630 Hart limestone: 140 Hartley County: 50, 213 Haskell County: 171, 175, 776 Haymond formation: 99, 117, 120, 122, 136 Hays County: 85, 130, 189, 424, 430, 440 "Hazel" formation : 39 Hazel Mine: 54 Helderbergian : 89 Helms group: 91, 94, 96, 97 Hemphill, H. A. : 183 Hemphill beds: 765, 766, 775 Hemphill County: 767, 775 Henderson County: 537, 538, 559, 584, 593, 598, 601 Hensell sand member: 314, 315 Hess formation: 146, 148, 149, 151, 162, 180, 184 Heterostegina zone: 530, 709 Hickory formation: 56, 57, 69 Hidalgo County: 752, 788 High Plains : 124, 184, 763, 795, 797 Hill County: 124, 130, 135, 189, 302, 303, 317, 321, 329, 336, 340, 350, 378, 384, 386, 394, 410, 415, 421, 425, 430. 440, 465 Hill Creek beds: 106, 107 Hockley County: 358 Hog Creek shale: 104, 112 Hog Mountain sandstone: 106 Home Creek limestone: 104, 112, 114 Honey Creek formation : 59 Hood County: 80, 308, 334, 345 Hopkins County: 484, 534, 538, 557, 558, 559, 584, 585, 593, 601 Hordes Creek limestone: 170, 173 Horse Creek shale: 105, 109, 170, 172 "Houston" clay: 441 Houston County : 622, 629, 638, 652, 655, 656, 657, 658, 659, 668, 670, 674, 675, 676, 697 Houston group : 530, 780 Howard County: 161, 247, 248, 250, 321, 331, 336 Hudson Bridge limestone: 105, 110 Hudspeth County: 213, 253, 254, 289, 295, 802ff Hueco Bolson: 53 Hueco Moimtains: 43, 53, 75, 84, 88, 90, 91, 94, 98, 115, 126, 127, 162 Hueco Tanks: 116 Humboldt, Baron Alexander von: 16 Hunt County: 428, 460, 462, 484, 489, 493, 538, 539, 540, 559, 797 Hunton series : 86 Hutchinson County: 50, 82, 214 Ideal gypsum: 168 igneous rock: ·33, 38, 40, 44, 48, 50, 139, 514 Indian Creek heda: 105, 109, 170, 173 Indio formation: 516, 613 intrusive rocks: 515 Iowa group : 91 1002 The University of Texas Bulletin No. 3232 Irion County : 80, 123, 214, 248, 308, 319, 320, 355, 369 . iron ore: 519, 637, 639, 643, 644, 648 Ivan limestone : 103, 114 Jack County: 80, 110, 112-115, 123, 214 J ackfork formation: 95, 131 J acksboro limestone : 104, 112, 113 J ackson County : 795 J ackson group: 530, 634, 677 Jagger Bend limestone: 169, 173 Jasper County: 741 Jasper Creek beds : 105, 111 Jeff Davis County: 393, 431, 799, 802, 803 J efferson City fossils : 72 Jefferson County: 742, 787 Jelm formation: 241 Jim Hogg County: 704 Jim Wells County: 754 J obnson County: 124, 329, 340, 350, 372, 376, 378, 379, 381, 384, 394, 410, 415, 417, 420, 425 Jones County : 171, 174, 175, 776 Jurassic: 23, 186, 253ff, 277, 286, 289, 299 Kansas: 282 Karnes County: 683, 699, 705, 713, 714, 730, 731, 754 Kaufman County: 461, 462, 486, 489, 493, 533, 534, 538, 539, 541, 551, 553, 559 Keechi Creek limestone and shale: 106, 108 Keechi dome: 262, 491, 496, 557 Kemp formation: 270, 481, 485, 486, 495ff Kendall County: 80, 93, 96, 122, 130, 132, 189, 215 Kennedy, William: 16 Kent County: 180, 184 Kent, Culberson County : 367 Kerens member: 530, 559, 562 Kerr basin : 136 Kerr County : 122, 125, 126, 215 Keuper beds: 242, 244 Kiamichi formation : 270, 277, 323, 327, 328, 336, 339, 341, 344, 347, 348ff, 363, 366, 368, 410 Kiamichi-Duck Creek contact: 327, 360 Kickapoo Falls limestone : 106, 107 Kimble County: 80, 93, 215, 320 Kimmeridge : 254, 256, 289 Kincaid formation: 530, 532, 634 Kinderhook group : 91, 95 Kinney County: 130, 134, 189, 304, 317, 320, 467, 468, 476, 515 Kirk, Edwin : 66, 75-78, 83 Kleberg County: 788 Knox County: 175, 779 Labahia beds: 530, 752, 754 Lafayette formation : 761, 777, 781 Lagarto formation: 530, 729, 740, 751 Lagarto Creek beds : 530, 753, 754 Lagrange group : 572 Lake Bridgeport shales: 105, 111 Lake Kemp limestone: 169, 174 Lake Pinto sandstone: 106, 108 Lake Trammel sandstone: 167, 179 Lamar County: 82, 130, 190, 409, 413, 421, 428, 441, 444, 459, 479 Lamb County: 248, 358 Lamotte sandstone: 611 Lampasas arch : 73 Lampasas County : 66, 73, 80, 96, 107, 216, 303, 314, 317, 321, 330 Lampasas cut plain : 342 Lampasitas arch : 266 Lanoria formation: 43, 44 Laramide folding : 64 "Laramie" : 467, 502 Larremore field : 394 La Salle County: 618, 652, 657, 669, 681, 683 Las Vigas formation : 271, 284, 291, 292, 294, 296, 297, 318 Lavaca County: 730, 731, 741, 752, 764 Lazy Bend member: 106, 107 lead : 806, 808 lead-silver prospect : 147 Lee County: 655, 663, 666, 667, 668, 669, 683 Leon County: 621, 622, 623, 629, 630, 631, 638, 656 Leon sands: 314 Leona formation : 781, 795, 796 Leonard formation: 146, 148, 149, 150, 152, 157, i62, 165, 181, 288 Lewisville formation: 270, 408, 410, 411, 414, 421, 434 Liberty County: 707, 742 lignite: 519, 594, 597, 598, 605, 625, 626, 627, 634, 669, 672, 673, 675, 692, 697, 698 Lignitic beds: 572, 607 Limestone County: 303, 416, 445, 463, 465, 466, 486, 490, 494, 496, 633, 584, 537, 539, 542, 551, 556, 559, 567, 584, 602 limestone reef : 159 Lion Mountain formation : 58 Lipan beds: 530, 680, 685, 686 Lipscomb County: 775 Lissie formation: 530, 761, 781 Littig member: 530, 536, 550, 554 Little Brazos limeetone: 658 Live Oak County: 619, 683, 686, 694, 703ff, 713, 714, 716, 719, 723, 730ff, 740, 741, 752-755 Llano County : 58, 59, 122 Llano Estacado: 241ff, 257, 324, 345, 410, 412, 423, 763, 795 Llano region : 30, 82, 83, 99 Llano series : 31, 182 Llano uplift: 20, 27, 45, 55, 57, 67, 69, 85, 86, 90, 93, 96, 127, 266 Llanoria geosyncline: 23, 84, 85, 97, 122ff, 187 Llanoria land mass: 21, 82, 83, 86, 129, 131, 136, 139 Lohn shale: 103 Lone Oak limestone: 536, 539, 553 Lost Creek shale: 170, 173 Lott chalk : 270, 456, 457, 463, 465 Louisiana: 318, 484 L<>up Fork beds: 765 Loving County: 249 Low Creek beds : 685 Lueders formation: 146, 169, 171, 174 Lufkin member : 655, 666, 679 Luling oil field : 45 Lynch Creek shale and sandstone : 106, 109 Lynn County: 356, 357 Lytle limestone: 169, 175 Lytton Springs : 394 Madison County: 676 Magdalena group : 94, 99, 116, 117 Maestrichtian: 271, 402 Main Street formation·: 270, 360, 362, 365, 368, 382ff, 887 Malone f<>rmation : 254ff, 288 Malone M<>untains : 163, 286 Manc<>s shale: 426, 481 Mangum dolomite: 168, 179, 181 Manning heds : 685 The Geology of Texas-lndex to Volume 1 1003 Mansfield group: 572 Marathon formation: 70, 76, 78 Marathon geosyncline: 89, 129 Marathon region : 21, 64, 69, 78, 82, 83, 87, 90, 95, 117. 125, 127, 130, 132. 191 Marathon uplift: 55, 67, 86, 98, 146, 267 Maravillas formation: 70, 78, 121, 191 marble: 69 Marble Falls formation: 92, 93, 99, 100, 117 marine beds: 607, 608, 635, 655, 667 Marion County: 620, 648 Marlbrook mar!: 270, 456, 457, 462, 481, 482 Marcy, R. B.: 17 Marginulina zone: 530, 709 Marlin cbalk: 270, 456, 457, 466 Marquez dome: 262 Martin County: 247, 248 Martín Lake limestone: 105, 110 Mason County: 46, 217 Matagorda County: 783, 789 Maverick County: 274, 297, 304, 317, 324, 333, 348, 394, 456, 469, 481, 496, 500, 534, 543, 574, 576, 582 Maxon sand: 271, 284, 285, 319, 321, 332, 353 Maybelle limestone: 169, 17 4 MeCaulley dolomite: 168 McCulloch County: 46, 66, 73, 80, 96, 110, 113, 217' 330 McElroy member : 530, 680, 685, 686, 687, 693, 696 McLennan County: 130, 132, 135, 190, 321, 330, 340, 349, 350, 360, 362, 367, 372, 376, 381, 384, 387' 389, 390, 394, 398, 401, 409, 411, 415, 417, 418, 423, 430, 434, 440, 449, 450, 456, 463, 796 McMullen County: 652, 669, 677, 681, 683, 704, 713, 714, 716, 723, 741, 754 Medina County: 130, 190, 320, 362, 390, 394, 399, 419, 445, 449, 450, 451, 456, 467' 469, 473. 475, 509, 515, 533, 534, 539, 550, 557, 584, 585, 586, 614, 618 Meek Bend limestone: 106, 107 Memphis sandstone: 167, 180 Menard County: 80, 218, 304, 355 Mendez shale: 263 mercury: 806 Merkel dolomite: 168, 176 Merriman limestone: 104, 111 Mesozoic lands and seas : 23 metamorphic rocks of Pecos uplift: 52 Mexia: 22 Mexia member: 630, 659, 562 Mexico: 256, 280, 286, 291, 358, 470 Midland Connty: 161, 182, 247, 248 Midway: 400, 402, 485, 496, 517. 530, 531, 634 Milam County: 394, 445, 456, 492ff, 534, 558, 666, 667, 568, 576, 577, 583, 584, 585, 689, 590, 59i, 593, 594, 598 Milams member: 656 Milburn shale: 104 Millican formation : 39, 42, 53, 63, 163 Millican Ranch: 40 Mills Connty: 66, 73, 80, 96, 107, 218;. 304 Millsap Lake formation : 99, 106, 107, 109, 123, 124 Mineral Wells formation: 99, 106, 108, 124 Minerva sand: 492, 495 Mingus shale: 106, 108 Miocene system : 727 Mississippi Valley : 83 Mississippian system: 88, 90, 95, 96, 99, 107, 117. 126, 131, 192 Missouri Mountain slate: 85, 130 Mitehell County: 248 Moenkopi formation: 241 Mohawkian series : 70 Montague County: 47, 66, 80, 85, 112, 114, 115, 125, 141, 171, 219, 311, 350 Montgomery County: 677, 741 Montoya formation: 70, 75, 79, 83 Monument Spring dolomite: 76 Moore County: 220 Moran formation: 102, 113, 140, 144, 146, 170, 171 Morita formation: 291 Morris County: 629 Morrison beds : 243, 257, 283 Moseley limestone lentil: 658, 663 llloseley's Ferry, fossils at: 663 Mount Selman series: 530, 608, 609, 610, 611, 612, 635 Mountain bed: 286, 294, 297, 318, 325 Muschelkalk beds: 244 Nacatoch sand : 270, 456, 480, 481, 483, 485, 486, 487, 492, 497, 509 Nacogdoches beds: 651 Nacogdoches County: 650, 655 N.avarro County: 303, 464, 480, 486, 488, 490, 493, 495, 533, 537, 539, 541, 556, 559, 560, 566 . Navarro group: 263, 270, 405, 407, 456, 467' 480, 497, 509, 516 Navasota County: 730 Navarro-Midway contact: 401 Navarro-Tertiary contact: 500 Necessity shale: 104, 113, 114 Neocomian : 273, 286, 292, 299 Neva limestone: 140, 143, 144 New Mexico: 83, 88, 243, 280, 427 Newton County: 713, 741, 748 Neylandville formation: 481 N iagaran series : 84, 85 Niobrara formation: 261, 263 Nolan County: 167, 331 Normanskill: 77 "North Denison sands": 37-4 North Leon limestone: 104 northeast Texas : 442, 456, 457, 4 73, 484, 486, 495 novaculite: 87 Nueces County: 795 Oakville formation: 530, 729 oil: 519, 650, 651, 655, 675, 677, 683, 697, 699, 731, 738, 739, 749 Ojinaga series: 401 Oklahoma: 83, 251, 281, 335, 349, 866, 369, 372, 383, 388, 394, 410, 412, 413, 444 Oldham County: 49, 220, 242, 247 Oligocene system : 530, 700 Olmos formation: 270, 481, 496, 501, 503 Ornen greensand member: 630 Onalaska member: 530, 715, 717 Onondaga series: 87, 89 Oran sandstone: 105 Orange County : 707 Orange sand: 781 Organ range: 43 Oriana gypsum: 168 Oriskany: 87, 89 Ordovician: 49, 51, 57, 61, 63, 66, 69, 74, 75, 77, 78, 80, 81, 92, 122, 130, 192 Osage group: 91, 95, 96 Osage Plains region: 101, 145, 165 Ostrea multilirata zone: 582 Ouachita facies: 80, 139 Ouachita geosyncline: 21. 67, 82, 89. 129 1004 The University of Texas Bulletin No. 3232 Ouachita Mountains region: 88, 84, 86, 87, 89, 95, 97, 126, 127,_131, 186, 191 oyster bed in Seguin formation : 57 4, 575, 577, 580 Ozan member: 270, 456, 457, 474, 482 Ozark region: 61, 69, 71, 72 Ozarkian system : 57, 65 Packsaddle schist: 31, 33, 86 Paint Rock beds: 169, 174 Paleozoic landa and seas: 21, 22 Palestine salt dome: 262, 362, 396, 402, 427, 598 Palo Pinto County: 73, 80, 93, 96, 99, 107, 109, 110, 111, 112, 220 Paluxy sand: 269, 270, 284, 300, 301, 308, 319, 320, 329, 353 Panhandle formation: 749, 765, 767, 773 Panhandle region: 67, 80, 125, 243, 369, 763 Panola County: 274, 301, 303, 495 Parker County: 107, 303, 306, 308, 311, 316, 317, 335 Parks Mountain aandstone: 103 Pawpaw formation: 269, 270, 362, 374, 377, 380, 381, 385 Peacock formation: 167, 177, 179 Pecan Gap chalk: 270, 456, 461, 465, 466, 474, 478, 493 Pecan Gap-Wolfe City contact : 462 Peco8j County: 67,' 80, 123, 125, 182, 221, 248, 361, 894 Pecos uplift: 52, 97 Pecos Va!ley: 361, 891 pegmatites : 34 Pennsylvanian ayatem : 52, 64, 82, 88, 94, 96, 98, 99, 103, 122, 125, 140, 148, 162, 163, 165, 171, 185 Pennsylvanian-Permian contact: 140 Pepper formation: 270, 360, 401, 408, 409, 411, 417ff, 423, 436 Percha abale: 88, 89 Permian baain: 80, 183 Permian syatem: 52, 113, 116, 124, 148, 145, 180, 185, 288 Phillipa, W. B.: 18 phosphatic pebble zone: 449 phyllite: 85 Pierre formation : 263 "Pinto" limestone: 439, 467 Pisgah memher: 530, 536, 540, 550 Placid abale: 104, 111, 112 Pleistocene: 776, 780 Pliocene system: 727, 7 49, 763 Plomosas formation : 257, 292 Plummer, Helen Jeanne: 419, 438, 454, 476 Polk County: 682, 694, 697, 698, 699, 715, 718, 726, 727. 729 Popo Agie formation: 241 porphyry: 34, 87 Port Hudson deposita : 787 Portland cement: 338 Portlandian : 256 potash: 145 Potosi formation: 56, 61, 71 Potter County: 49, 177, 178, 222, 242, 247, 253 Potterformation: 765 Powell sand : 492 pre-Cambrian system: 27, 35, 37, 41, 45, 51, 121, 122, 124, 132, 163, 192 Presidio County: 119, 130, 163, 305, 894, 426, 456, 470, 505, 509, 799, 802, 803, 806, 807 Presidio formation: 271, 286, 304 Preston anticline: 266 Proterozoic: 20, 27 Pueblo formation: 99, 103, 118, 115 Pulliam formation: 468, 480, 500 Purgatoire formation: 258, 263, 283 Putnam formation: 102, 113, 146, 170, 172 Quanah gypsum: 168 Quarry limestone: 375, 376 Quartermaster formation: 146, 161, 167, 177, 178, 179, 182, 184, 186, 252 quartzites : 38 Quaternary : 776 Queen City formation: 609, 611, 612, 618, 628 Queen sand zone: 160, 181, 182, 184 Quitman bed: 286, 297, 318 Quitman Mountains: 286, 292ff, 393, 472 Quitman-Eagle Mountaina: 402 Quito formation : 242 Rainey limestone: 169, 175 Rains County : 538, 557, 599 Rancheria Mountain : 116 Randall County: 247 Ranger limestone: 104, 111, 112 "Rattlesnake" formation: 505 Reagan County: 66, 70, 80, 82, 83, 84, 89, 96, 122, 125, 175, 182, 184, 222, 855 Reagan sandstone: 58, 69 Real County: 122, 125, 832, 839 red beds : 98, 186, 270, 299 "Red Cave" beds: 17 4, 177 Red River County: 82, 180, 185, 190, 413, 441, 444, 458, 463 Red River uplift: 47, 49, 70, 74, 80, 85, 97, 123, 126 Reeves County: 799, 802 Refugio County: 677 Reklaw formation: 580, 609, 611, 612, 618, 614, 619, 634 Resser, C. E.: 60 Reynosa formation: 740, 751, 755, 761, 777, 781, 782 rhyolite porphyry : 44 Rice aands: 684 Richardson, G. B. : 84 Richmond: 79, 83, 84 Ricker bed: 105, 109 Rio Grande embayment: 267, 298, 325, 381, 427, 467, 500 Rio Grande Valley: 582, 614, 621, 622, 626, 637 Ripley group : 269, 400, 480 road materials: 553, 583, 779 Robertson County: 584, 585, 588, 622, 630, 638, 646, 647, 652, 655, 658, 663 Robinson'a Ferry: 681, 693, 695 Rochelle conglomerate: 104, 111 Rock Creek beds : 797 Rock Hill limestone: 105, 111 Rockdale formation : 530, 57 4, 583, 634 Rockwall County: 460, 461, 465, 489 Rocky Ceda.r Creek limestone: 536, 539, 540, 641, 553 Roemer, Ferdinand : 17 Rogers chalk: 270, 456, 478 Roubidoux formation : 71 Rough Creek beds: 105, 109. 118 Royston formation: 167, 177 Runnels County: 80, 171, 174, 175, 181, 223, 331, 336, 346 Rusk County: 417, 620 Rustler formation: 146, 157, 161, 182, 184, 186, 244 Rustler Hills: 161 Ryan sandstone: 141 Sabinas basin : 502 Sabine County: 602, 608, 605, 635, 636, 639, 656, 668, 685, 686 The Geology of Texas-lndex to Volume l 1005 Sabine formation : 572 Sabine River beds : 607 Sabine River valley : 585 Sabine uplift: 265, 325, 417, 614, 620 Sabinetown formation : 57 4, 601, 634, 530 Saddle Creek limestone i 103, 115, 144 Saddlehorse gypsum: 167 St. Maurice beds: 667 St. Peters sandstone: 57 Salesville sbale: 106, 108 Saline Bayou member : 656 salt: 619 Salt Flat: 87, 63, 156, 167 "Salt Series": 177 San Andres range: 43 San Angelo formation : 146, 168, 177, 178, 184 San Augustine beds: 635 San Augustine County: 656, 663, 685 San Carlos formation: 456 San Felipe formation : 263 San Jacinto County: 713, 731, 738, 741 San Marcos arch: 266, 276, 403 San .Miguel formation : 270, 466, 467, 469, 481, 603 San Patricio County: 754, 797 San Saba County: 46, 66, 80, 90, 94, 96, 107, 223 Sanders Bridge limestone: 106, 110 Santa Anna Branch heda: 170, 172 Santa Anna sbale: 170, 172 Santa Rosa sandst.one: 243, 244, 249 Santiago cbert: 87 Santo limestone: 106 Santo Tomas coa!: 627 Santonian: 271 Saratoga formation : 270, 480, 481, 482, 484, 486 schists: 38 Scbleicher County : 122, 356 Scurry County: 249, 260, 776 Seaman Ranch beds : 104, 112 Sedwick limestone: 170, 172 Seguln formation: 630, 658, 674, 68' serpentine: 406, 616 Seven Heart Gap: 166, 167, 168 Seven Rivers gypsum: 160 Seymour deposita: 776, 779 Sbackelford County: 80, 96, 171, 172, 174, 224 Sbadrick Mill sandstone: 106, 109 Sbafter formation: 271, 286, S04 Shafter mines: 164 Shafter region: 145, 399 Sbelby County: 303 Shinarump formation : 244 Sblpp's Ford: 667 "Sboal Creek limestone" : 396 Shereveport sands: 492 Sbumard, B. F.: 17 Shumard, G. G.: 17 Shumard Survey: 18 Sierra Diablo: 63 Sierra Madera: 147 Sierra Madera uplift: 145, 162, 166 Sierra Prieta : 367 Signa! Mountain formation : 56, 69, 71, sills:34 silver: 40, 68, 146, 806, 808 silver-copper mines: 42 Silurian system: 84, 94, 130 Silurian seas : 86 Simpson series : 80 . Simsboro sand : 530, 576, 686, 58'1 Siouxia: 22 slates: 88 Smith County: 417, 614, 622, 629, 630, 638, 653 Smithwiek formation: 99, 101, 107, 117, 123 soils: 619, 546, 564, 570, 684, 597, 626, 665, 697, 749, 792 Soledad member : 530, 716, 717, 719 Solitario: 21, 55, 64, 65, 67, 69, 76, 77, 78, 82, 83, 86, 87, 95, 98, 117, 130, 267, 296, 306, 318, 332, 346, 355, 393, 397, 399, 431 Solms-Braunfels, Prince Car!: 17 Solomon Creek sandy clay: 530, 675, 576, 677 Somervell County: 303, 315, 320 South Bend shale: 104 "South Bosque marls" : 426 South Liberty salt dome: 262, 402 south Texas : 467 southwest Texas: 431 Sparta formation: 530, 611, 612, 634, 651 Specks Mountain limestone: 103 sponge spicules: 59. Spring Creek beds : 105, 109 Springer formation : 127 Stalf limestone: 104 Standpipe limestone: 169, 175 Stanley formation : 95, 130 Stanley-Jackfork series: 97, 126, 127. 138 Starr County: 683, 689, 704, 733, 787 Steen dome: 262 Stephens County: 80, 96, 113, 115, 224 Sterling County: 123 Steussy shales : 106, 107 Stockwether limestone: 103, 115 Stonewall County: 167, 168, 176, 177, 178, 179, 180, 253, 321, 330, 336, 346 stratigraphie data from wells : 187 Strawn basin : 136 Strawn group: 102, 105, 106, 109, 124, 126 Stringtown. shale: 130, 181 sulpbur: 519 Sutton County: 80, 122, 226, 255, 317, 369 Sweetwater dolomite: 167 Swenson member: 168, 179 Swisher County: 797 Sycamore sands : 314, 316 Tabor well: 132 Talpa limestone: 169, 173 Tamasopo limestone: 263 Tarrant County: 270, 307, 329, 336, 360, 362, 367. 370, 372, 373, 376, 376, 378, 379, 381, 384, 394, 408, 410, 414, 417, 420, 425, 429, 796 Taylor County: 46, 73, 96, 123, 171, 176, 176, 226, 321, 331, 346 Taylor formation : 242, 263, 269, 270, 406, 407, 443, 456tf, 467, 472, 474, 476, 497, 508, 617 Taylor-Navarro eontact: 466, 494 Tecovas formation : 242, 248, 244, 261, 262 Tehuacana limestone: 496, 632, 636, 639, 541, 642, 644, 645, 653 Tennesseian serles: 91 Terlingua arcb: 267 Terlingua bed : 271 Terlingua region: 381 Terlingua,.Chisoe area : 472 terrace deposita : 796 Terrell arcb: 267, 276, 881, 388 Terrell County: 180, 182, 190, 361, 394, 402, 426, 427' 481, 461 Terry County: 248 1006 The University of Texas BuUetin No. 3232 Tertiary: 138, 520 Tesnus formation: 90, 95, 99, 117, 118, 120, 121 Tessey member : 153 Texas geology, subject index of: 966 Texas Mineral Survey : 18 Texas Panhandle: 66 Textularia hockleyensis zone : 684, 685, 696 Thrifty formation : 99, 103, 113, 114 Throckmorton County: 80, 96, 115, 123, 171, 172, 173, 174, 226 Thurber coal: 106, 108 Tierra Vieja Mountains: 472 Timber Belt beds: 607 Tithonian : 256 Titus County : 599 Tokio formation: 270, 417, 440, 444 Tom Green County: 123, 175, 176, 177, 178, 330 Torcer formation: 271, 284, 28611', 318 Tornillo formation : 271, 505, 50811', 513 Trans-Pecos Texas: 277, 373, 388, 436, 45111', 472, 505 Travis County: 130, 135, 191, 285, 294, 302, 303, 308, 310, 316, 320, 332, 362, 372, 384, 394, 424, 425, 430, 434, 440, 441, 445, 446, 449, 450, '453, 455, 456, 466, 467, 470, 473, 496, 497, 509, 515, 536 Travis Peak formation : 270, 284, 285, 294, 297, 298, 300, 304, 31011', 317, 327 Trenton limestone: 78, 79 Triassic formation: 23, 101, 155, 177, 180, 184, 186, 241 Trickham shale: 103 trilobites : 59 Trinity County : 622, 638, 652, 656, 658, 668, 686, 687, 698, 699, 724 Trinity group: 263, 270, 273, 277, 28411', 29511', 29811', 299, 303, 309, 311, 319, 368, 410 Trujillo formation : 242, 243, 244, 251, 253 Tule formation : 773, 795, 797 Turkey Creek sandstone: 106, 108 Turonian : 271, 437 Turritella turneri zone: 583 Tye formation: 169, 176 Tyler County: 699, 718, 738, 741 Tyler greensand : 653 Uddenites member: 110, 112, 122, 144, 148 Ulrich, E. O.: 75, 79, 83, 85, 88 Ultima Thule grave!: 305 University Mesa: 271, 328, 339, 347 Upsbur County: 676, 614, 629 Upson: 270, 456, 467, 469, 473, 503 Upton County: 248 Uvalde area : 399 Uvalde County: 297, 304, 320, 339, 348, 390, 394, 426, 445, 467, 468, 473, 476, 515, 532, 534, 543, 557, 574, 685, 586, 614, 618 Uvalde gravels: 776, 777, 781 Val Verde County: 130, 132, 145, 191, 270, 297, 304, 307, 362, 394, 399, 402, 426, 427, 431 Valanginian: 271, 284 Vale formation: 146, 169, 174, 176, 181 Valera sbale: 169, 173 Valley Spring gneiss : 31, 32, 36 Van Horn arkoses: 74 Van Horn formation: 66, 63 Van Horn Mountains: 37, 54, 163, 332, 402, 438 Van Horn region : 20, 27, 37, 65, 69, 74, 7 5, 82, 83, 84, 88 Van Zandt County : 538, 561, 653, 566, 556, 559, 584, 621 Variscan Mountain system: 139 Velasco formation: 263 Venericardia bulla zone: 635, 536, 666, 569, 566 Venericardia eoa zone: 550 Venericardia hesperia zone: 550 Venericardia smitbii zone : 551, 552 Ventioner beds: 112 Vicksburg group: 700, 702 Victoria County: 702, 704, 707, 754, 766 Victoria Peak member: 157, 162 Vidrio member : 152, 153 "Vieja series": 513 Village Bend limestone: 106 Vivian sand: 492 "Vola limestone" : 387, 396 volcanic ash: 515, 669, 673, 678, 684, 686, 689, 691, 694, 698, 700, 702, 703, 706, 71311', 734, 735, 747, 804 volcanic rocks : 798 Wagon Yard gypsum : 168 Waldrip limestone: 103 Walker County: 713, 726 Walnut : 269, 270, 274, 318, 323, 326, 327, 32811', 333, 334, 336, 353, 355 Wapanucka formation: 127 Ward County : 249 Ward gypsum: 167 Washington County: 534, 652, 656, 656, 658, 682, 698, 702, 704, 713, 714, 730, 732, 738, 741, 745 Wasbita : 263, 270, 299, 307, 36911', 363, 366 water horizons: 346, 519, 663, 618, 634, 655 Watts Creek shale: 170, 171 Waverlian series: 91 Wayland shale: 103, 113, 114 Wealden facies : 290 Webb County: 550, 557, 558, 621, 627, 657, 669, 682, 683, 704, 705, 713, 714, 723, 730 Webberville formation: 480 Weches formation: 530, 609, 610, 611, 612, 635 Wellborn sandstone: 685, 686 Weller, Stuart: 94 Wellington formation: 185 Weno formation : 270, 363, 365, 368, 37811' west Texas : 467 · Wbarton County : 782, 787 Wheeler County : 49, 82, 226, 797 Wbite Rock escarpment: 447 Whitehorse formation: 146, 177, 181, 182, 184 Whitehorse-Cloud Cbief formation: 178, 179 Whitsett beds: 630, 680, 686, 686, 687, 694, 695, 696 Wicbita County: 47, 80, 123, 146, 171, 173, 227 Wichita group: 113, 144, 168, 169, 170, 171, 175, 180, 181, 184, 185 Wichita Mountains: 51, 59 Wichita paleoplain : 241, 260 Wilbarger Creek: 109 Wilbarger Creek sandstone: 105 Wilbarger County: 47, 80, 85, 123, 174, 175, 177, 228 Wilberns formation: 66, 58 Wilberns Glen formation : 69 The Geology of Texas-lndex to Volume 1 1007 Wilcox group: 411, 530, 571, 634 Wiles limestone: 104, 111 Willacy County: 788 Williams, H. S.: 9Q Williamson County : 89, 128, 130, 132, 135, 191, 304, 329, 331, 344, 361, 362, 394, 425, 430, 445; 466, 497 Willow Point limestone: 105, 110 Wills Point formation: 530, 532, 656, Wilson County: 595, 614, 616, 618, 621, 629, 637, 641, 683 Winchell, Alexander: 90 Wingate sandstone: 243, 259 Winkler County: 182, 248 Wise County: 109, 110, 111, 112, 113, 124, 126, 306, 311, 316, 350 Wizard Wells limestone: 105 Wolfcamp formation: 117, 122, 144, 146, 148, 150, 162, 164, 181 Wolfe City formation: 270, 456, 457, 459, 460, 464, 473, 474, 495 Wood County: 585, 599, 629, 681 Woodbine district: 307 Woodbine formation: 269, 270, 276, 360, 387' 396, 400, 401, 403, 408ff, 428, 433, 440 Woodford chert: 88 Woods Hollow formation: 65, 70, 78 Word formation: 146, 148, 151, 153, 158, 164, 165 Wortham lentil: 530, 537, 538, 559 Wreford limestone: 140, 143, 144 Wylie Mountains: 37, 163 Yates sand: 182, 184 Yeager formation-: 703 Yegua formation: 608, 609, 611, 634, 655, 666 Yeso limestone and gypsum: 355 Yoakum County: 248 Young County: 66, 80, 83, 96, 114, 116, 171, 228 Yucca sand: 285, 296 Zapata County: 657, 669, 682, 683, 697, 704, 714, 730 Zavala County: 476, 515, 534, 615, 618, 619, 621 zinc: 808 THE UNIVERSITY OF TEXAS BULLETIN 3232 PLATE XI U th. A. Hoen & Co .• lnc.