THE PAOOUCING HORIZON JN THE RIOS WELL IN CALDWELL COUNTY B57-1022-2500 University of Texas Bulletin No. 2239: October 15, 1922 The Producing Horizon in the Rios W ell in Caldwell County BY E. H. SELLARDS Bureau of Economic Geology and Technology Division of Economic Geology J. A. Udden, Director of the Burean and Head' of the Division PLJBLISHED BY THE UNIVERSITY FOUR TDiES A MONTH, AND EKTERED AS SECONll-CLASS lHAT'IER AT THE POSTOFFICE AT AUSTIN, TEXAS, UNDER 'J'HE ACT OF AUGUST 24, 1912 .. ' The benefits of education and o:f useful knowledge, generally diffused through a community, are essential to the preservation of a free govern• ment. Sam Houston. Cultivated mind is the guardian genius of. democracy. It is the only dictator that freemen acknowl· edge and the only security that free­men desire. Mirabeau B. Lamar. Page Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Surface Formations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Regional Structural Features............................ 6 Zone of Faulting...................................... 7 Local Structural Conditions............ .". . . . . . . . . . . . . . . . . 7 Thickness of Formations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Available Literature and Geologic :;\faps. . . . . . . . . . . . . . . . . . . . 8 Oil Production........................................ 8 The Producing Horizon.................................. 9 Description of Samples from Cartwright 2, by J. A. Udden and P. T. Seashore.................................10 Note on Cartwright 2, by J. A. Udden................... .17 The Ríos W ell ........................................18 Description of Samples from the Rios vVell, by E. H. Sellards and P. T. Seashore..................................21 Description of Samples from Cartwright 3, by E. H. Sellards and P. T. Seashore.................................23 Production from the Lower Cretaceous in Texas............27 W ell Logs............................................27 Log of Cartwright 1...................................28 Interpretation.....................................29 L-og of Cartwright 2..................................30 Interpretation.....................................31 Log of Gartwright 3.................................·. 32 Interpretation of Cartwright 3 and Cartwright 4......33 Log of Rios 1 ........................................33 Interpretation.....................................34 Log of C. A. Schawe..................................34 Description of Samples from the Schawe W ell, By J. A. Interpretation.........................................36 1::-dden...........................................35 Log of Thompson l. .................................36 The Ghormley W ell in Guadalupe County..............38 ILLUSTRATIONS Figure l. Sketch showing correlation of the Rio8 and Cart­wright W ells ........................................19 THE PRODUCIKG HORIZON IN 'l'HE RIOS WELL lN CALDWELL COUKTY BY E. H. SELLARDS Caldwell County lies within the Gulf Coastal Plain of Texas, near its west margin. The Balcones escarpment, which forros the boundary line bet1nen the Coastal Plains and the Edwards Platean, passes ·west of this county, but within five or six miles of the county line. The formations at the surface in Caldwell County are those of the Upper Cretaceous and the Lower Ter­tiary. The Upper Cretaceous formations includc the Taylor and Navarro, 1Yhile of the Tertiary formations, there are present the ::.\Iiclway and the vVilcox. To what e.xtent other Eocene formations, including the Carrizo and J\It. Selman, are developed in this county has not been dctermined. Except where concealed by terrace materials, the )l°avarro and Taylor formations cf the Upper Cretaceous lie at the surface over a narrow belt at the west margin of the county. This Cretaceous belt is widest at the south side of the county and narrows to the north margin of Jhe county where its width scarcely exceeJs two miles, and 1vhere the Navano formation only is present. 'l'he t01Yn of J\fax-vvcll lies within the Cretaceous, although near its east margin. Next east of the Cretaceons is the J\Iichvay formation, whi.ch occupies a narrow belt p1::s'3ing through the county from north­northeast to south-southeast. Cooperative work between the Unitecl States Geological Survey and the Bureau of Economic Geology of the University has resulted in identifying several Midway localitics ·within this area. Among these localities is one fonr ancl six-tenths miles sLghtly south of west of Lockhart where clays are e.xposed containing a Midway fauna. Othcr sirn.­ilar localities are found on the Lockhart-Austin road, one and one-half and two miles north of Lockhart. From a well about eleven miles west of south of Lockhart and about two miles southwest of J oliet, 1\Iiclway fossils wcre obtained. This well, which starts in the vVilcox formation, was drilled to the depth of 340 feet. Shell bearing clays ancl shales are reported in the Manuscript submitted in September; issued November, 1922. well beginning at sixty feet from the surface and extending to t11e full depth of the vvell. 'l'he :Jiid \Yay fossils obtained were from the dump, their position in the well being unkrnnvn except tlrnt certain of them are stated to have come from 320 feet. These localities indicate that the :JUidway is found a few miles west of Lockhart and probably extends somewhat east of Lock­hart. The trend of the outcropping belt of thc formation is north-northeast to south-southwest. :Next east of the Midway is the \Vilcox formation. In traveling south frcm Lockhart, on the Lockhart-Luling road, exposures representing the \Vilco:s: are first seen on Olear Fork Creek and its tributaries about four miles south of Lock­hart. On the San ·Marcos River six miles northwest of Luling and near the Cartwright vYells is an e:s:posure consisting of Yery sandy micaceons clays including several strata of cone-in­cone concretionary layers. This e:s:posure is referred provi­sionally to the Wilcox. The eastern margin of the Wilcox has not been determined, bnt the formation may be expected to have a gre:.iter width than the Midvrny and to pass throug·h the county from north-northeast to south-soutlnnst. It is probable that fomrntions latcr than the \\Tilco:s: come into the section before reaching the east county 1inc. Sands probably representing the Ca:cTÍzo formation are secn near Ivy, il1 the sontheastern part of the county. Regiona.·l Stmctural F'eatures. The regional clip in Caldwell Connty is in a southeasterly direction, so that, Tl'Íth the excep­tion of any reversals in C.ips that may occur, successively younger formations come into the section as one traYels to the east or scntheast. 'l.'he average rate of dip in the formations across the full ffidth of this county has not been detennined. It is known, hon·ever, that the Austin formation, which is found at the sur­face in and near San }farcos, is encountered in the Cartwright and Thompson wells at depths varying from 1742 to 1835 feet. The Austin exposures at San Marcos are at an elevation approx­imating 600 feet above sea, while the eleYation of the Cart­>vright wells, as indicated by the topography map, is possible 150 feet lower. Taking this difference in surface elerntion jnto consideration, this record indicates that the Austin drops to a lmrer level across this interval at a rate approximating 100 feet per mile. It is probable that this change in le"rnl comes about through faulis as well as through dips. Zone of Paulting. The Balcones Escarpment seen at San Marcos rnarks the ·west rnargin of the Balcones Fault Zone. Faulting in this zone is particularly heavy in the vicinity of San .Marcos, so much so that the Austin fonnation, which has a thickness of several hundred feet, occupies in this area no more than a very limited surface cxposure, and in places is almost entirely faulted out of the section. The Balcones Zone of faulting occupies a considerable width and includes most if not all of Caldwell County. To 1Yhat extent, lwwever, faulting is developed in this county, can be determined only by careful detailed investigation. Local Structuml Conclitions. In many of the faults of the Balcones Fault Zonc, including the large fault, which is respon­siblc for the Balcones Escarpment, the downthrow is to the sonthcast. However, \\-ithin this fanlt zone are occasional faults in which the downthrow is 1 in the opposite. direction, that is, to the northwest. One of these faults 1Yith downthrow to the northwest is seen in an exposure on the left bank of the San Marcos RiYer, six miles northwest of Luling, and near the Cartwright wells. '11he fault in this place trcnds in a north­easterly direction and the fault plane dips steeply to the north­1Yest. rrhe faulting-in this Ímmediate locality may be SOIDewhat complicated, but that at least one fault occurs having dmvnthrow to the northwest is indicated by the "drag." Thickness of Formations. The deep well drilled at .:\Iaxwell, starting probably in the Xavarro formation, apparently pene­trates all of the underlying Cretaceous. In this well white rock, presumably the Austin, is recorded from 760 to 1036 feet, or through an interval of 267 feet. "Gumbo," probably rep­resenting the Eagleford formation, is found from 1036 to 1071 feet. The several lower Cretaceous formations are scarcely separable, the one from the other, in the well log. However, the Lo\rer Cretaceous, as a whole, apparently extends from 1071 to about 3405 feet, indicating a total thickness of the Lower Cretaceous at the locality of 2334 feet. Below the Cretaceous at 3H5 feet, are found rocks of undetermined age, but believed on the authority of Dr. J. A. Udden, who examined samples throngh this interval, to be older than the Cretaceous. _.\.. measnrement of the fnll thickness of the Cretaceous above the Anstin in this county has not been obtained. Howe\er, a shallo\\. 1Yell t1rn miles southy1·est of Jolict, located on the J\Ier:::er farm, apparently terminated in the J\!Iidway, as indi­cated by the fossils on the dump, at a depth of 340 feet. The Rios well, not more than two mi}es to the southwest of this shallow vvell, entered the Austin at 1635 feet. These records indicate for the C1·etaccous, above the Austin in this county, a total thickness of approximately 1350 feet, or less. The thick­ness of the l\Iid'.rny and \Vilcox and other Eocenc formations in this eastcrn part of the county, has not been determined. Available Literature a·nd Geologic Maps. The geologic litera­ture on Caldwcll Couniy is limitecl. The Austin quadrangle mapped by the United States Geological Survey includes a small part of the northwest comer of the 'connty, and the map of that quadrangle indicates the distribution of the late Cre­taceous and carly Tertiary formations in that area. The Geo­logic map which accompanies Bulletin 44 of the University of Texas indicates approximately the Creta0eous and Tertiary arcas of the county. The inYestigation now in progress in cooperation behreen the United States Geological Survcy and the Bureau of Economic Geology and Technology of the Univer­sity cf Texas will afford the data for a publication to be issued when the investigation has been completed, relating to the Mid­way formation of this and adjoining counties. Oil Prodnction. One well producing oíl in this county has recently been obtained. This well, which is owned by the United North and South Oil Company, is located on the Rios farro about six and one-half miles northwest of Luling, and about 011e ancl one-half miles from the San Marcos R.iver. The well was drilled in about August 10, and is ffowing by heads and making sorne water 1Yith the oil. The gTavity of the oil is reported as being abont 28-B. Production in this well is, with little doubt, associated with the fault already referred to as being seen near the Cartwright wells on the San Marcos River. Faults with downthrow to the northwest bring about conditions favorable to production for wells locatcd near but east of the fault line. On the other hand, faults 1vith downthrow to the southeast, which are much more common than those with the downthrow to the northwest, do not necessarily infiuence production. The explanation is probably found in the fact that since the regional dip is to the southeast a fault with downthrow in that direction merely accentuates the dip, while a fault with downthrow in the oppo­site direction, that is, to the nortlnvest, has the effect, by rea3on of the "drag," incident to faulting, of reversing the dip. The more or less complete filling of the fault plane with secondarily accumulated materials may likewise assist in forming a trap for accumulation of oil. Oil pools controlled by faults of this kind are likely to extenc1, if at all, with the trend of faults. THE PRODucrna HoRizox In a press bulletin issuecl by the Bureau of Economic Geol­ogy and 'l'echnology of the Uni.Yersi.ty of Texas, Au_gnst, 1922, the writer expressed thc tentatiYe conclnsion that the pro­ducing horizon in the Ríos well in Caldwcll Connty, Jmown as the Luling well, is probably from the Georgetown-Ed>rnrcls series of limestones of the Lo1rnr Cretaceous. In view of the general interest as to the producing horizon in this well. it secms worth while to give more fnlly the evidence on which this conclusion is based. As in the prcvious paper the data given are from the records of the Bureau of F.Jconomic Geology and 'l'echnology of the University of Texas, and used with the permission of the Director of the Bureau. Of several wells drilled in Caldwell County, the record of the three Cartwright wells, located about one ancl one-half miles southwest of the Rios >'i'ell, is perhaps the most complete. That Cartwright 2 had penetrated the Eagleford, Buda, and Del Rio formations, and entered the Georgetown-Edwards series of lime­stones was cletermined by Dr. J. A. Udden as early as A.pril, 1922. The interpretation of the formations penetrated in the Cartwright wells is greatly facilii.ated by having at hand a core taken at the depth of 2117 feet, which contains a number of fossils. The most abundant fossil in the rock at this depth is the small shell knmYn as the ''ram 's horn'' shell, Exogyra arietina. As this fossil is characteristic of the Del Rio forma­tion we have from this core a definite starting point in the interpretation of the record of the well. By the aid of the samples and from the driller 's log the Del Rio, in this well, is identified as extcnding from 2068 feet to 2176 feet. Under the Del Río is a porous limestone impregnated with petroleum. This limestone is intcrpreted as of the Georgetown-Ec11rnrds series of limestones. Drilling in Cartwright 2 >vas continued to 2-±11 feet. ~ext above the Del Rio formation in Cartwright 2 is fo1mc1 thirty-four feet of limestone, representing the Buda formation. Thi:s rock differs from the Buda as commonly observed in wells in that it is for the most part chalk-like in appearance and con­tains glauconite. The rock next above this limestone is identified from the driller's log and from samples as the Eag.leford forma­tion, which in this well has a thickness of forty-nine feet. Next above the Eagleford is the A~ustin Chalk, which has, accord­ing to the driller 's log, a thickness of 249 fe et. No sam ples of the Austin have been received from Cartwright 2. However, a core was taken from Cart>Yright 3 at a depth of 1923 feet, and hence within the interval assigned to the Austin. Inasmuch as the Cartwright wells afford valuable .aid in the interpretation of the formations in this county there is included in the following paragraphs the description of samples from one of these wells made while the well was in process of drilling. The descriptions are by Dr. J. A. Udden, and are included with his permission. The log of this well is given subsequently. Description· of samples from the United North and South Oíl Com· pany's Cartwright 2, on G. C. Kimble League, six ,and one-half miles northwest of Luling, two and one-half miles southeast of Prairie Lea, Caldwell County. Submitted by W. F. Peale, Luling, Texas. BY J. A. "LDDE:'\ A:'\D P. T. SEASHORE Depth in Feet Sample consists of two fragments of a core of grey, thinly laminated, calcareous shale containing fish re­ mains, such as bones and scales. This shale splits readily alcng the laminations. In thin section the shale is seen to be of uniformly fine texture, and to contain a great abundance of foraminifera like Orbulina, Globigerina, and Nodosaria ( ?) . Sev­ era! ostracod valves noted. The laminations in this shale are caused by layers which are composed largely of foraminifera. The bands of foraminifera are from % to 1/3 mm. apart. The more clayey bands betweeu the layers of foramiuifera are com­ posed of still finer layers, possibly consisting of fiattened foraminifera. In this matrix are white calcareous lentils, which probably consist of fiat or fiattened organic fragments. There are fiat layers of black bituminous material. In matrass the shale gives strong odor of bitumen. vVhen inserted in an open fiame the shale burns and gives off the odor of burning peat and tallow. In washed material Eome yellowish calcite and a few scattered crystals of pyrite noted. Fossils: Globigerina, Orbulina, and Textularia. Severa! fragments of fish scales and Inoceramus prisms present. Eagleford. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1993 Very light grey, soft, almost white limestone or chalk. In thin secticn it is seen to be of very fine texture and to contain a number of cavities filled with a ye1Iowish green mineral. Severa! spherical cavities, evidently of organic origin, filled with calcite noted. These range in size from .3 mm. to .1 mm. in diameter... 2038 White limestone containing many minute fragments of glauconite ( ?) and sorne shell fragments. In thin section the limestone is seen to be very fine-grained. Severa! fissures and cavities filled with calcite noted. Foraminifera are found in great abundance. Such forms as Orbulina, Globigerina, Lagena, and Nodosaria were recognized. Several ostracod valves noted. In places where the green grains are not found, the rock has the typical appearance of the Buda limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2040 Sample consists of a 3" core of bluish grey calcareous shale or mar!. lVlegascopically it is seen to cort­tain shells of Pelecypods. Among these can be recog­nized Exogyra. arietina Roemer. Considerable cal­cite and pyrite noted in the washed material. Fossils: Orbulina, Globigerina, Textularia, Cristel­laria, Anomalina, 2\fcdosaria, Polymorphina (?) , and several unrecognizable forms. A sponge spicule present. Six differe'lt types of oscracods noted. Of thiJse one has a pittecl, two have smooth, and three have a highly ridged carapace. Del Río in aspect The sample consists of several ¡Jieces of a four-inch core. It is a soft dolomitic and bituminous yellow-i~h grey limestone, containi:lg sorne fossil fragments. Among these were noted a piece of the test cf a sea urchin, several ostreid fragments, fragments of a Requienia patagiata. ( ?) In thin section the rock is seen to have a lmnpy texture and to coci­tain imbedded flagments of fossils mostly replaced by calcite. Frcm below the Del Rio, proballly Georgetown, possibly the Edwards................ Grey marly shale with sorne yellowish grey dolomitic limestone like that of the preceding sample. The shale contains foramii1ifera such as Textularia and Globigerina, Ancmalina arnmonoids, and Cristellaria. A l:uge oblo•1g ostracod, an echinoid spine, frag­ments of óhells and fragments of a Bryozoan (mon­ticuliporcid ( ?) noted. The Jatter forms a fiat tab­let and the polyps or zoéiecia are more or less ar­ranged in orderly lines. . . . . . . . . . . . . . . . . . . . . . . . . . . The sample consists of two large pieces of a grey lime­stons like that in the preceding sample and two large pieces which show effects of heating and wearing by the drilL The rock itself, so affected, seems to have been calcareous. A fifth fragment is perhaps an impure calcarE:ous chert. The rock is too much altered by the drill to be recognized....... . . . . . . . The sample consists of a dozen larg~ pieces. Five of these appear to be {mpure soft and fragile dolo­mite like sorne of the rock described aboYe. It con­tains sufficient oil to give a strong odor. The other pieces are grey marly shale, sorne of which contain many small fossils. Fossils: Cristellaria cultrata, Truncatulina, Anomalina, Nodosaria zippei ( ?) , Depth in Feet 9117 2182-2184 2184-2188 2197-2198 Depth in Feet Bythocypris, Nadosaría radicula, Nodosaria pau per­ata, Nodosaria consobrina. These foraminifera are of a larger size than is common in the Cretaceous 2218-2220 Sample consists of a piece of a core of yellowish dirty grey, porous c'lolomite, highly irnpregnated with oil. It contains sorne very large calcite crystals and fragments of poorly preserved rnollusk shells. In thin section the limestone is finely crystalline. As­pect of Edwards Iimestone... __ ................... 2235-2236 Sample consists of a piece al' a core of yellowish dirty grey dolomite impregnated with oil. On a polished surface this dolomite is seen to contain shreds and specks of bitumen. º These shreds are mostly par­ allel to the bedding plane. In thin section the dolomite is seen to be finely granular and to con­ tain minute fissures filled with a bituminous ma­ terial. ............................1••••••••••••• 2240-2241 Sample consists of a piece of a core of grey, somewhat soft and chalk-like limestone. This limestone is seen to contain many minute cavities filled with calcite. These are evidently casts of foraminifera. In thin section the limestone is seen to be finely crystalline and to contain specks of a black material. . 2242-2243 Sample consists of a piece of a core of grey compact limestone containing many shell fragments. There are also included in the sample severa! pieces of grey marl. The shell fragments present in the limestone are believed to be Requienia. In thin section the limestone is seen to be fine grained and has a lumpy texture. Many minute crystals of calcite noted. In the washed material from the marl, calcite and pyrite were noted. The pyrite occurs partly in irregular grains, partly as oolitic masses and very Iargely also as fillings in the shells of foraminifera. Sorne minute crystals of sphalerite and perhaps sorne of Galena ( ?) were noted. Fossils: Nodosaria. Polymorphina, Textularia, Globigerina, Anornalina, and Pulvinulina were the foráminifera noted. Severa! prisms which resem­bled those from Inoceramus and a minute shark's tooth, like one previously noted in the Upper Cre­taceous... ·'· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2245-2246 A piece of a core of dirty yellowish brown porous dolo­ mite highly impregnated with oíl. This dolomite is irregularly laminated. Most of the laminations tend toward about a 15° dip, one is nearly horizontal, while another dips into it, the whole being perhaps the result of cross-bedding. Evidence not conclu­ sive. In thin section the dolomite is seen to have a slightly lumpy texture and to be very finely granu­ lar. Two limited areas in one section have a finer and different texmre from the rest, and appear to be only slightly altered remains of fossils in the original rcck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2250-2251 Sample consists of several pieces of a core of light grey limestone and a piece cf grey very slightly cal­ careous clay. On a polished surface the· limestone is seen to contain many foramininfera casts filled with calcite. In thin section the limestone is seen to be granular and to contain many foraminifera. The washed material from the clay ccntains a J:ew fossils: Foraminifera resemblir g Cristellaria gibba, Rotalia, Nodosaria, aI!d Anomalina noted. Fragments from larger shells, like those from pelecypods also present..............................·,. . . . . . . . . . . . 2258-2259 Sample consists of several pieces of a core of dirty brownish grey porom C:: lomite highly impregnated with oil. Sorne of the pieces of the core are changed to a porcelain-like consistency hy heat developed in drilling. In thin section the dolomite is seen to be very finely granular. . . . . . . . . . . . . . . . . . . . . . . . . . . 2265-2266 Sample consists of about four cubic inches of light and dark grey marl and a piece of a core of light grey limestone. Into the marl has been introduced pock­ ets of glauconitr; rock, almost pure glauconite. This mixing may peí·haps be clue to work by the drill. If such is not the case the sample suggests that the drill has been going through a fault breccia or a cave deposit. The glauconite is in part almost black and in part green. The grains show the usual ex­ terna] reticulated sutures. In size these grains range up to Y2 mm. in diameter. In thin section the limestone is seen to be granular with small pockets of calcite representing casts of foraminifera. In the washed material from the marl, the fcllow­ ing fossils were founcl: Foraminifera resembling Nodosaria zeppei, Nodosaria obliqua, :Nodosaria radí­cula, :Nodosaria niticla, Noclcsaria consobrina, Cris­tellaria obtusata, Cristellaria cultrata, Cristellaria gibba, Cristellaria mamilligera, Anomalina ammo­noicles, Anomalina gros.serugosa, Rotalia Tritaxia, Lagena, Polymorphina lactea, Polymorphina com­pressa, Pulvinulina, four types of Fronclicularia, one of which is very narrow ancl about 4 mm. long, Globigerina, Textularia sagittula, Truncatu­lina refu!gens, Spirillina. ancl severa! other forami­nifera which cculd not be cletermined. Ostracocls, lJoth with smooth ancl with finted ancl pittecl cara­paces notecl. Fragments of Pelecypocl ancl gastropocl shells, Dentalium fragments and Inoceramus prisms (?) present. Severa! otoliths, fish teeth ai::cl spines ancl Echinoicl spines were also noted.... Sample consists of severa! pieces of grey marl ancl a piece of a core of light grey chalk-like limestone. The grey limestone under the hand lens shows traces of fcssils, minute crystals of calcite, and areas of lighter colored limestone. In thin section the limestone is seen to be finely granular and very unifcrm in texture. The washed ma~erial from the mar! contains sorne calcite and pyrite. Bright red hematite grains notecl. These range up to 1 mm. in diameter. Fossils: A large Cristel­laria cnltrata measuring abont 1 mm. in diameter, a nodosaria resembling Noclosaria pauperata, sev­era! Anomalina ammonoides and a fragment which may represent Frondicularia. An ostracod pres­ent, whicli is very wide at the hinge; this wide part being covered with longitudinal fiutings. Sev­eral fragments of well-IU"eserved thicl;: fish scales and many Echinoid spines presenL Several frag­ments of granular calcite, which were washed from the mar!, show slickensides with very straight and delicate striations on one surface.................. Sample consists of severa! pieces of grey rnarl and a piece of a core of dirty brownish grey scmewhat dolomitic limestone showing embedded fragments of fossils. In the washed material from the marl are found fragments of brownish finely crystalline dolomitic limestone, a few fragments of a black lJituminous material, and several aggregates of min­ute crystalline pyrite. Fossils: Fragments of a Depth in Feet 2269-2270 2273-2274 Depth in Feet Kodosaria, Textularia, ostracods, fragments of casts from Gastropods and Inoceramus prisms. In thin section the limestone is seen to be finely crystalline and to contain areas filled with clear calcite. Slickensides on granular calcite noted............ 2280-2281 Sample consists of a piece of a core of soft grey porous limestone and several pieces of grey calcareous shale or marl. In the washed material from the marl were founcl fragments of white limestone and grey dolomitic limestone. Considerable glauconite present. These glauconite grains show the regular reticulated surfaces. Fcssils: Anomalina, Globi­gerina, Textularia, Cristellaria cultrata ( ?) , Cris­tellaria gibba ( ?) , a ribbed Nodosaria, Vaginulina, Nodosaria pauperata ( ?), an ostracod carapace, and several Inoceramus prisms noted. Fragments of shells like those from pelecypods, and fish remains, such as fragments of spine noted. A small black spherical body about .3 mm. in diameter with a smooth polished exterior. This body resembles sorne found in the Coim Eros. >ro. 2, near Kyle in Hays County. On a polished surface the limestone is seen to rontain small nodules of a lighter colored limestone. Sorne very fine quartz sand and small areas filled with calcite. In thin section this lime­stone is seen to be fine grained and to have a lumpy texture, rather chalk-like.................. 2305-2306 Sample consists of several pieces of a grey marl and a piece of a core of grey limestone. On a polished surface this limestone is seen to contain sorne min­ute cavities filled with calcite. Many black specks noted. These cavities and specks are evidently casts of foraminifera. The limestone is seen to con­tain irregular lumps of darker rock surrounded by a matrix of lighter colored rock. These lumps range in size upward to more than an inch and re­minds one of blotchings seen in the Austin Chalk. In thin section the limestone is seen to be fine in texture and to contain a few obscure traces of foraminifera. The washed material from the marl contains mainly fragments of light grey limestone, considerable pyrite, and a few grains of glauconite. Much of the material has been altered by the heat generated in drilling. Several ostracod carapaces, Depth in Feet a Pulvinulina, a Globigerina, and a Textularia pres­ent in the sample................................ 2408-2409 Sample consists of several fragments of grey marl and a piece of a core of pure and minutely crystal­line white strontianite. One surface of the core of strontianite has an adhering layer of grey lime­stone. 'l'he contact between the limestone and the strontianite is very irregular, but bends in such a way as to suggest that the strontianite has been de­posited in a cavity in the limestone or has grown as a concretion. In thin section the limestone is seen to be finely textured and to contain many minute crystals of calcite. The washed material from the marl yields mosUy fragments of a light grey limestone, brownish crystalline dolomite and white strontianite ( ?) . A few crystals of pyrite noted. l\!Iany of the fragments have changed to a porcelain·like substance )Jy heat developed by the drill. Prisms Iike those from Inoceramus noted. A Textularia and Globigerina present. . . . . . . . . . . . . 2448-2449 NOTE BY J. A. UDDE:'\' :-The samples from 2245-2246 down to 2280-2281 show several features that strongly suggest that the drill in this dis­tance has been close to a fault plane. The strongest evidence is in the occurrence of a shale or marl which contains a fau'la of Upper Cretaceous fossils, such as occur in the upper part of the Taylor or in the Navarro. Upper Cretaceous material was found occurring below the Georgetown and perhaps below or in the Edwards limestone. The presence of glauconite in association with the marls having an Upper Cretaceous fauna corroborates such a conclusion. The same may be said of the occurrence of istraight slickensides and such minerals as sphalerite, hematite, galena (?), and abundant pyrite. The fact that limestone and bodies of glauconite have been worked into sorne of the marl suggests that the drill may have gone through a fault breccia. Pieces of marl in which this was observed appeared to be parts of a core, but little disturbed by the work of the drill. Another explanation that would account perhaps equally well for the finding of Upper Cretaceous material in the Upper Comanchean and far the mineralization and brecciation noted would )Je that the drill has in the distance from 2245-2281 penetrated a cavern deposit. In a fault plane one would rather expect to :find more calcite than occurs in the present samples. On the other hand, more sand would perhaps be ex­pected in a cavern deposit than was found in the present samples. The strongest evidence for this material being regarded as a cavern deposit is the presence in the marl of what appears to be sorted glauconite grains, which are most likely to have been washed together by running water, such as might form a cavern deposit. Fragments of harder parts of the country rock are usually present in the cavern deposits, into which they are introduced either by falling from the walls of the caverns or by water running in the caverns.1 Since writing the above it appear¡;¡ possible that the samples may represent material mixed in drilling. T rrn Rros \VELL The record of the Rios well is made up from cores and cuttings of the rock drilled through, and from the driller 's log. Accord­ing to the log, chalk rock was rlrilled through in this vvell from 1630 feet to 1868 feet, n total of 238 feet. No samples have been obtainecl of thi" chalk. However, immediately undcr the chalk, at 1898 feet, samples were obtained which are of the character of the Eagleford formation. From the log sorne diffi­culty is experienccd in fixing the lower limits of the Eagleford in the Rios 1vell. It seems probable, hawever, that the Eagle­ford is to be regarded as extencling to 1961 feet, having thus a thickness of 93 fect. This interval of 93 feet includes 50 fe et loggecl as "broken rock" and as limestone, 1vhich may or may not be properly included in the Eagleford. Next under­lying the Eagleford is a light colorecl limestone rock idcntical in character with that regarded as the Buda in the Cartwright well, the rock being chalky in appearance, and containing glaw­conite. In my previous publication I referred to the presence of glauconite as an unusual feature of the Buda formation. Re­cently, however, Dr. R. T. Hill has called my attention to the Austin folio of the United States Geological Survey, in which the Buda limestone found on Shoál Crcek, in the vicinity of Aust:n, is said to be glauconitic. The glauconite of the Shoal Creek rock, however, is inconspicuous and not easily recognizecl, in this rcspect differing from the compicuous green glauconitic particles in the rock from thesc wells. A sample from the Rios well at 2005 feet presents the lithologic appearance of the Del Ria formation, although from this sam­ple, which is limited in quantity, no index fossils of that forma­tion were obtained. A sample taken at 2136 feet consists in part of a very porous limestone impregnated with petroleum. 1Bull. U. S. Geol. Survey, No. 505, p. 87, 1912. Fig. l. Sketch showing formations drilled through in the Ríos and Cart­ wright wells from the Aust.in to the G e o r g e t o w n­ Edwards forma­ tion. The interpre­ tation as h e r e given is from the drillers' lo'gs and from samples. The top and bottom of each formation is determined from the drillers' log, while the identifi­cation of the form­ation itself is in m o s t instances from samples of rock cuttings or cores. The state­ment, "E. arietina alJundant," refers to the abundance of this fossil in a core taken at 2117 feet in Cartwright No. 2. Vertical scale of sketch: One inch equals 100 feet. Cartwnght 11-z §2~;52ª /t/11st1 n 2.4'1' Del R10 'ºª' ~. ~r1~1'1no obvnhl"I' Successive samples below this depth to 2160 feet consist of lime­stone, including at least one layer of black ftint. This lime­stone rock is similar in character and is to be correlated with that referred to the Georgetown-Edwards series in the Cart­wright 1vell. 'l'he oil in the Rios well is obtained at 2161 feet. Although differing more or less in thickness the formations of Ríos 1 are definitely correlated with those of Cartwright 2. The rock regarded as Georgetown-JDclwarcls, entered at 2176 fcet in the Cartvvright 2, finds its equivalent in Ríos 1, at 2136 feet, this rock in each of the weUs being porous and saturated with petroleum. The Del Río, identified by fossils in the Cart­wright well at 2068 to 2176 feet, finds its equivalent in the Rios •Yell at 2003 to 2136 feet. Limestone rock found in the Ríos well frorn 1961 to 2005 feet is identical in appearance with that regarcled as Buda in Cartwright 2 at 2034 to 2068 feet. The Eagleford in each well is identifiecl by samples. The Austin in the two wells is recorded from the driller 's log, although cores were obtainecl within this interval from Cartwright 3. ··with regara to the forrnations encountered in drilling in the Ríos and other wells in Caldwell County, it may be notecl that the rock here provisionally identifiecl as Buda is unusual for the Buda forrnation, in that in places it is scarcely to be distinguished on lithologic characteristics from the Austin forrnation, being a light colored glauconitic limestone. However. if this rock is interpreted as Austin it is then necessary to inclucle >Yithin the Austin formation the overlying shale rnember having the litho­logic appearance of the Eagleford. Moreover, upon this inter­pretation it would be necessary to· assume that the Exogyra arietina shells found in the core at 2117 feet in Cartwright 2 are seconclary fossils. These shells in the core, however, are exceptionally well preserved, having retained their most delicate ornamentation, affording no evidence o:E having been moved frorn their original resting place. I t rnay be added that the presence o:E black flint in Rios 3 is suggestive o:E the Georgetown­Edwards lirnestones rather than of the Buda, and that drilling continued into this lirnestone series for 235 feet in Cartwright 2, supported by numerous san:ples, afforded no reason to doubt the reference of the lirnestones to this series. From within the interval assigned to the Buda, cores have been obtained from Cartwright 3 indicating that alternating with or above the glau­conitic rock of the Buda are layers which are not glautonitic and which are typical of the Buda in texture. In order to complete the record available on the Rios well there is here included the desc1"iption of samples from this well, the log being given on a later page. A description of samples obtained from CartwTight 3 is likewise inclnded. The records on these wells taken as a whole are believed to justify the con­clusion that the cil from the Rios 1rell is obtained from the Georiretown-Ed1rnrds limestones in the Lower Cretaceous. In ~ ' case of an overthrust or thrust fault, if such has occurred, production may, of course, be oblained from the Upper Creta­ceous after passing through L'ower Gretaceous foTmations. Description of samples from United North and South Oil Co.'s Rios No. 1, one and one-half miles northeast of Cartwright No. 3, John Henry League in Caldwell County. Samples submitted by W. F. Peale, Luling, Texas. ' BY E. H. SELLAROS Ai\'D P. T. SEASHORE Depth in Feet Sample consi~ts of several pieces of grey, slightly micaceous, slightly calcareous shale. In the washed material were found grains of glauconite, pieces of calcite, fiakes of muscovite, and a few quartz sand grains. FossiLs: Cristellaria, Globigerina, Textu­ laria, Ancmalina, Nodosaria, Frondicularia, Vaginu­ lina, and Tritaxia, fish scales, spines, and otoliths, a part of an annelid j1aw (?), Pelecypod shell frag­ ments, ostracods, and Inoceramus prisms. Two corals noted. Probably Eagleford....................... 1898 Sample consists of two pieces of a core of light grey llmestone and a sample of cuttings consisting of grey marl and white limestone. The washed material from the marl contains sorne glauconite, a few quartz sand grains and several crystals of pyrite. Fossils: Inoceramus prisms, Textularia, Tritaxia, Globigerina, Cristellaria, Anomalina, Nodosaria, ostracods, and shell fragments. On a polished surface the lime­ stone is seen to contain a large number of minute cavities filled with microscopic crystals of pyrite. In thin section the limestone is seen to contain a very large number of foraminifera, many slender needle-like spines and Echinoid 5pines and tissue. Many of the íoraminifera llave been replaced by pyrite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample consists of a píece of grey finely textured mar!. ·washed material consists cf pieces of calcite and crystals of pyrite. Fossils: Inoceramus prisms, Globigerina, Textularia, and Ostracods. Probably Del Ria. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Grey marl and dirty yellowish grey porous limestone. The !imestone is impregnated with oil. In the washed material frcrn the marl were noted glau­conite, crystals of pyrite, a few pieces of calcite, and a number of íragments of a black sott material resembling asphalt. Fossi;s: Inoceramus prisms, Cristellaria, Tritaxia, Nodosaria, Textularia, Globi­gerina, and ~clünoid spines. In thin section the limestor e is seen to be fine-grained and to have a slightly lumpy texture. The entire ssction is filled with microscopic crystals of calcite. Several veins and larger areas are made up of crystals of caicite Like sample of 2136. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample consists of pieces of yellowish grey porous lime­stone and grey and alrnost black marl. The en­tire sample is permeated with oil. The washed material from the marl contains aggregates of minute crystalline pyrite and pieces of calcite. Inoceramus prisms, Cristellaria, Anornalina, Vag­inulina, Textularia, ostracods, and pelecypod shell fragments. In thin section the limestone is seen to be finely grained and to have a lumpy texture. A few small area:; of calcite noted. .... . . . . . . . . . . . Sample consists of dark grey marl and two pieces of a core of yellowish grey porous limestone. The entire sample is impregnated with oil. In the washed material from the marl were noted many fragments of limestone like that represented by the core, pieces o~ calcite, crystals of pyrite, grains of glauconite, and fragments of black fiint. Fos­sils: Cristellaria, Ancmalina, Nodosaria, Globi­gerina, Textularia, ostracods. Inocerarnus prisrns and fragments of shell from other pelecypods... Depth in Feet 1960 2005 2136 2138 2139-2140 2144 Depth in Feet Light grey marl. In the washed material were found ·a few pieces of calcite, crystals of pyrite, and pieces of a black asphaltic material. Fossils: Inoceramus prisms, Echinoid spines, Globigerina, Tritaxia, Cristellaria, and pelecypod shell fragments. . . . . . . 2155 Sample consists of severnl pieces of a e.ore of dirty yellowish grey porous Jaminated limestone. The Jaminations consist of thin layers of a black bitu­ minous material. Traversing the entire core and parallel to the bedding plane is a vein of black fiint. In this fiint can be seen imbedded obscure traces of organisms. In thin section the limestcne is seen to be finely granular and to contain small areas filled witl, calcite. . . . . . . . . . . . . . . . . . . . . . . . . . 2157 Sample consists of grey marl. In the washed material were found a few pieces of yellowish grey lime­ stone, pyrite, and calcite. A few grains of glauco­ nite noted. Fossils: Cristellaria, Anomalina, Globi­ gerina, Textularia, ostracods, Inoceramus prisms, fish scales, and pelecypod shell fragments.... . . . 2158 Description of samples from United North and South Oil Company's Cartwright 3, two and one-half miles suutheast of Prairie Lea and six and one-half miles northwest of Luling, G. C. Kimble Sur­vey, Caldwell Ccunty. Submitted by W. F. Peale, Luling, Texas. BY E. H. SELLARDS A'ID P. T. SEASHORE Depth in Feet Sample consists of grey mar!. The washed material consists mainly of fos~ils, pieces of calcite, a12d graíns of glauconíte and crystals of pyríte. The glau­coníte shows regular reticulated sutures. Fossils: Inoceramus prisms, pelecypcd shell fragments, a fragment of an Ammonoid, Nodosaria, Crístellaria, Pulvinulina, Vagínulína, Tritaxia, Anomalina and ostracods. In the washed material from 1;1i mm. in diameter and down were found many Textularia, Globígerína, and Orbulína. 1195-1225 Grey slightly micaceous marl. In the washed material were found a number of fragments of Inoceramus shells, shell fragments from other pelecypods, Tex­tularia, Trítaxia, Anomalina, Criste!laria, Trunca­tulina, and severa! smooth ca;•apaced ostracods. A black, smooth surfaced, ellípsoidal body noted. Depth in Feet This body measures 1.25 mm. in length, and .4 mm. in diameter . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349-1380 Grey marl, lithologically like preceding sample. In the washed material were found a few aggregates of minutely crystalline pyrite, pieces of calcii:e, and fragments of clay-ironstone. Fossils: Inoceramus prisms, Kodosaria, severa] thin keeled Cristellaria, Pulvinulina, Frondicularia, Textularia, Globigerina, and ostracods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1500-1590 Grey mar! containing sorne fine sand. In the wasiled material were found several aggregates of minutely crystalline pyrite, fragments of fine grained highly calcareous sandstone, larger quartz sand grains. A few brown, red and pinkish chert grains also noted. Severa! pieces of ciear calcite, and sorne scattered grains of glauconite present. Fcssils: Inoceramus prisms and shell fragments, fragments from other pelecypods, a large C:ristellaria cul­trata, several thin keeled Cristellaria, Pulvinulina, Textularia, Globigerina, Anomalina, and a number of Yarieties of ostracods............... .... . . . . . . . . 1590-1642 Sample consists o[ grey marl. In the washed material are found a few quartz sand grains, piece of white calcite, pyrite and glauconite, and a number of fossils. Fossils: Fragments of Inoceramus and other pelecypod shells, Anomalina ammonoides, Cristellaria gibba, Cristellaria cultrata, Nodosaria, Lagena, Textularia, Globigerina and Orbulina...... 1642-1700 Grey slightly micaceous marl. The washed material con­sists mainly of grains of glauconite and fossils, a few quartz sand grair.s noted. Fossils: Inoceramus r1risms, Cristellaria, Nodosaria, Anomalina, Textu­laria, Pulvinulina, Globigerina, and Orbulina. A few echinoid spines also noted. A few black ellipsoidal bodies with a smooth polished exterior surface present. ... 1785-1798 Sample consists of grey mar!. In the washed material were found a few grains of glauconite and aggregates of rninutely Crystalline pyrite. Fossils: Textularia, Globigeria, Anomalina, Cristellaria, Lagena, Poly­ morphina, Pulvinulina, ostracods, Inoceramus prisms, and echinoid spines..................... .... . . . . . . . 1816-1841 Depth in Feet Sample consists of several pieces of a core of grey lime­ stone containing a large amount of glauconite and minute crystalline pyrite. On a polished surface the limestone is seen to contain a large number of lentils of lighter colored limestone. A few small shell frag­ ments noted. One piece of the core is in part made up of grey compact marl. In thin section the lime­ stone is seen to be finely textured and to contain a large number of foraminifera, echinoid spines, and many small slightly curved spines, which probably represent section of ostracod carapaces. Among the foraminifera can be recognized Obulina, Glcbigerina, and Nodosaria( ?) . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • 1923 Sample consists of a piece of a core consisting in part of grey compact marl, in part of light grey shaly lime­ stone. The washed material from the marl was seen to contain fragments of grey shaly limestone, quartz sand grains, calcite, and pyrite. Many oblate and prolate spheroids measuring from 14 to 72 mm. in diameter noted. These colitic spherules are black, and have a smooth polished exterior. They are made up of concentric layers and are partially made up of pyrite. These bodies are similar to those found in Cohn Eros. No. 2, Hays County, at a depth of 145'-150', and in the United North and South Oil Co.'s Cartwright 2, Caldwell County, at a depth of 23051-2306'. Globigerina, Textularia, Orbulina, ostracods, and a shell fragment noted. In thin sec­ tion the limestone is seen to be made up almost entirely of Orbulina and Globigerina. . . . . . . . . . . . . . 2013 Sample consists of a piece of a core of dark bluish grey, very slightly calcareous shale of fine texture. In the washed material were found pieces of calcite, pyrite, and a few fish scales. In closed tube yields enough bituminous material to sustain a fiame. . . . . 2039 Sample consists of several pieces of a core of dirty grey limestone. On a polished surface the limestone is seen to contain a large number of shell fragments. Several large crystals of calcite noted. In thin sec­ tion the limestone is seen to be fine grained and to contain a number of cavities filled with calcite. The entire section is traversed by a network of lighter colored limestone. Foraminifera like Orbu­ lina and Globigerina are found in great abundance. A :-..:odosaria ñoted. Echinoid spmes and tissue also present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample consists of several pieces of a core of grey mottled limestone. On a polished surface this lime­sto!1e is seen to contain areas of lighter colored limestone, an abnrda12ce of glauccnite, blotches of minutely crystalline pyrite, shell fragments, and a very large number of foraminifera. In thin section the limestone is seen to contain a number of cavities filled with calcite. Many foraminifera, Echinoid spines, and shell fragments ..................... _. Sample consists of severa! pieces of a ccre of white limestone together with a piece of grey limy shale. In the washed material from the marl were found a few pieces of calcite and a small amount of pyrite. Inoceramus prisms and a few shell fragments noted. On polished surface the limestcne is seen to con­tain considerable glauconite and sorne small shell fragments. In thin section the limestone is seen to be made up almost entirely of foraminifera. Scat­tered throughout the sections are found Echincid spines and tissue and small bodies of minute crystalline pyrite . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . Sample consists of grey marl arrd fragments of white limestone. In the washed material were found a few quartz sand grains, crystals cf pyrite, crystals of calcite, and grains of glauconite. Fossils: Cris· 'tellaria, Anomalina, Ncdosaria, Textularia, Globiger­ina, Trit'lxia, Inoceramus prisms, ostracod carapaces, and echinoid spines ........................ _. . . . . . Sample c0nsists of a ccre of white limestcne contain­ino' a large number of mlnnte grains of glauconite. C' A. piece of a core of greenish grey compact limy shale. This material also contains considerable glau­ccnite. In the washed material from the marl a large number of Inoceramus prisms were noted. In thin section the limestone is seen to be very fine gr::tined. Several cavities fillecl with calcite noted. The limestone is seen to be blotched with areas of a clarker colored limestone. The lime­stone contains a very large amount of foraminifera. Among these can be recognized Orbulina, Globi­gerina, and Textularia. Fragments from larger shells and echinoid spines also noted. . . . . . . . . . . . . . . Depth in Feet 2047 2052 2065 2065-2078 2078 Depth in Feet Sample consists of several pieces of a core of white limestone. On a polished surface the limestcne is seen to contain a Jarge number of minute cavities filled with microscopic crystals of pyrite. JVIany shell fragments also noted. In thin section the limestone is seen to contain a very large number cf foraminifera. Among these can be recognized Orbulina, Globigerina, Nodosaria, and Anomalina. Echinoid spines and small shell fragments. . . . . . . 2087 Sample consísts of several pieces of a core of grey limestone containing a large nurnber of minute bodies filled with micrcscopic crystals of pyrite. ln thin section the limestone is seen to be finely grained, and to contain a large number of foramini­ '.era Echinoid spines and tissue and shell fragments. Sorne of the foraminifera shells have been replacecl by pyrite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2092 PRODUC'l'ION FnoM THE LovYER CnET.\CEOUS IK TEXAS In this connection it may be noted that the Lower Cretaceous formations have previously yielded sorne oíl in the Statc. The shallow wells in the South Bosque Field in JHcLennan County obtain cil from these formations. In Panola County very large gas -vvells have been obtained from a horizon that is prob­ably about 500 feet below the top of the L01Yer Cretaceous, sorne of these gas wells ha-ving afforded a production of not lcss than t"·enty million cubic feet of gas per day. A small amount of oil has likewise been obtained from a horizon in Panola County vYhich is probably at, or near. the top of the Lower Cretaceous. The J ones >Yell near Kosse, in Limestone County, apparently obtained oil from a Lmnr Cretaceons hori­zon. These scveral gas and oil_ wells indicate that the Lower Cretaceons should not be neglected as containing possible oil producing formations in Texas. Although not inclnding all we11s drilled in the county, the wells, logs of which are given here, may be regarded as rep­Tesenta tive of drilling conditions in the 1Yest half of the county. Formations in the east part of the county may be expected at an increased depth over that shown by wells in the west part of the county. Log of A. P. Cartwright 1, United North and South Oil Co.'s, G. C. Kimble Survey, six and one-half miles northwest of Luling, and two and one-half miles southeast of Prairie Lea. Drilling com· menced March 29, 1921. Log corrected by steel line measurement at 1784 feet. Depth in Feet Depth in Feet From To Thickness Surface clay and sand................ . o 18 18 Rock............................. . 18 34 16 Sand............................. . 34 64 30 Rock............................. . 64 108 44 Shale............................. . 108 128 20 Rock............................. . 128 130 2 Shale............................. . 130 138 8 Gumbo and gyp..................... . 138 143 5 Shale............................. . 143 155 12 Gumbo-set and cemented 10" casing at 160'. Reduced hole to 9% .......... . 155 160 5 Shale and boulders.................. . 160 460 300 Gumbo............................ . 460 474 14 Shell and shale..................... . 474 504 30 Sand rock......................... . 504 507 3 Shell and shale..................... . 507 537 30 Sand rock and pyrites of iron......... . 537 538 1 Hard sand rock..................... . 538 542 4 Sandy shale, showing oil and gas at 550' Sandy shale. . ..................... . 542 552 552 593 10 41 Rock............................. . 593 594 1 Shale............................ . 594 634 40 Gypsum........................... . 634 653 19 Shale and boulders.................. . 653 656 3 Gypsum and gumbo................. . 656 697 41 Sand rock......................... . 697 699 2 Shell and shale. . . . ................ . 699 714 15 Shell............................. . 714 721 7 Gumbo........................... . 721 731 10 Shell. ............................ . 731 771 40 Gumbo........................... . 771 775 4 Shale............................. . 775 784 9 Shale (sticky) ..................... . 784 823 49 Gumbo........................... . 823 833 10 Shale and shell. . . ................. . 833 853 20 Rock............................ . 853 854 1 Soft shale......................... . 854 928 74 Gumbo........................... . 928 976 48 Lime rock-reduced hole w 81h" . .... . 976 988 12 Shale............................ . 988 1,062 74 Gumbo........................... . 1,062 1,071 9 Shale............................ . 1,071 1,109 38 Gumbo........................... . 1,109 1,121 12 Shale............................ . 1,121 1,264 43 Shale and boulders................. . 1,264 1,334 70 From To Thickness Gumbo........................... . 1,334 1,342 . 8 Shale............................ . 1,342 1,489 147 Gumbo........................... . 1,489 1,496 7 Hard shale........................ . 1,496 1,514 18 Shale............................ . 1,514 1,522 8 Gu1nbo........................... . 1,522 1,542 20 Shale. . ......................... . 1.5•±2 1,567 25 Sandy gu1nbo...................... . 1,567 1,581 14 Shale............................ . 1,581 1,586 ;:¡ Shale and shell.................... . 1,586 1,630 44 Gumbo........................... . 1,630 1,636 6 Shale............................ . 1,636 1,700 64 Broken lime rock. . . ............... . 1.700 1.708 8 Sandy shale....................... . 1,708 1,73b 30 Gumbo........................... . 1,738 1,744 6 White shale. . . . .................. . 1,744 1,766 22 Broken lime rock.................. . 1.766 1,778 12 Gumbo........................... . 1,77S 1,786 8 Chalk rock (hard) ................. . 1,786 1,788 2 Measurement with steel line showed 17 84 Chalk rock........................ . 1,784 1,786 2 Reamed hole to 9%"-set 8" from 9 8 8 casing ( did not cement) cnalk rock.. '...................... . 1,786 1,9 81 193 C11alk and flate.................... . 1,981 2,075 84 Shov.ing cil and gas at 2,000'. Shale and slate..................... . 2.07 5 2,105 30 Blue slate......................... . 2;1 05 2,135 30 Shale with pyrites grayel ............ . 2,135 2,190 55 Broken lime. . . . ................. . 2,190 2,200 10 vVater sand-cooJ sulphur w'ater ..... . 2,200 2,211 11 Pyrite rock....................... . 2,211 2,215 4 Very hard-set 6" casing but failed to shut off warer. vVater sand-hot sulphur water...... . 2,215 2,229 14 Hard sand rock-very fine sand. . . . .. . 2.229 2,231 2 Oil sand-showing oil and gas ........ . 2,231 2,236 5 Measurement with steel line .......... . 2,232 Sandy lime with iron ............... . 2,232 2,240 8 Hard lime. . ................... . 2,240 2,276 36 Sandy lime with iron............... . 2,276 2,288 12 Soft lime ......................... . 2,288 2,304 16 Hard lime......................... . 2,304 2,332 28 Interpretation: This well which starts probably in the vVilcox appears to have entered the Austin formation at or near 178 4 feet. The record is indefinite as to the base of the Austin, and the thick­ness of the Eagleford and Buda. However. these two formations probably lie between 1,981 and 2,075, the "blue slate" at 2105 to 2135 probaJ!y represents a part of the Del Rio. The Georgetown· Edwards limestones are probably entered at or near 2,J 9O, the su1phur water obtained at 2,200 and at 2,215 being quite certainly from th~se limestones. The well probably terminates in the Edwards. Log of tlle Cartwright Xo. 2, of the Lnited Xorth and South Oll Comipany, Ca.'dwell County. Depths Cori•ected By Steel Line Measurement. Surface........................... . Dob,y............................. . Sand.................. ·. · · · · · · · · · · C!ay............................ ·. Rock............................ . Sandy shale. . . . . .................. . Rock............................. . Rock sand (gas) ................... . Lignite........................... . Rock, sand........................ . Gumbo........................... . Rock sand........................ . Clay............................. . Hard sand........................ . C!ay............................. . Sha!e............................ . Clay............................. . Shale............................ . Sand (water). . . .................. . Shale............................ . Clay............................. . Shale............................ . Clay............................. . Sand............................. . Clay............................. . Boulder.......................... . Clay............................. . Rock............................. . Hard sandy shale. . ................ . Rock............................ . Shale............................ . Pyrite........................· · . · · C!ay................ · · · · · · · · · · · · · · Sand rock........................ . Cla,Y............................. . Boulder.......................... . Shale. . . ........................ . C!ay................. · .... · ·. · · · · · Rock............................. . Hard shale........................ . C!ay and gyp...................... . Shale and gyp_ ..................... . Boulders......................... . Shale and gyp..................... . Shale............................. Shale and gyp_ .................... . C'!ay............................. . Rock............................. . Clay.............................. . Shale...........................· · Clay........................-· ·. ·. Shale.....................•....... C!ay............................. . Shale........................... · · Depth in Feet From To Thickness o 3 3 3 6 3 6 8 2 8 12 4 12 14 2 14 59 45 59 65 6 65 104 39 104 108 4 108 134 25 134 138 4 138 141 3 141 149 8 149 164 15 164 168 4 168 198 30 198 204 6 204 237 33 237 250 13 250 283 33 283 338 55 338 359 21 359 396 37 396 401 5 401 434 33 434 435 1 435 497 62 497 498 1 498 507 9 507 .508 1 508 529 21 529 562 3'r 562 580 rn 580 581 1 581 639 58 639 640 1 640 665 25 665 697 32 697 698 1 698 705 7 705 724 19 724 744 20 744 745 1 745 798 53 798 803 5 803 809 o 809 898 89 898 899 1 899 1,084 185 1,084 1,095 11 1,095 1,162 67 1,162 1,188 26' 1,188 1,201 13 1,201 1,244 43 Clay and gyp, ..................... . Shale............................ . Clay........... · · · · · · · · · · · · · · · · · · · Shale............................ . Clay............................. . Gyp_ ............................ . Shale............................ . Clay, ............................. . Shale and gyp..................... . Clay and g,YP............ · · .. · · · · . · · Clay with sand. . .................. . Shale and gyp, .................... . Gu1nmy shale. . ... : ............... . Gyp, ............................ . Chalk............................ . Shale and pyrites.................. . Gu1nmy shale. . . .................. . Shale and pyrites.................. . Lime and shale..................... . Gummy shale...................... . Sandy gumbo and boulders .......... . Sandy shale and pyrites............. . Sandy shale....................... . Sandy shale, hard .................. . Hard sand rock, sulphurous.......... . Conglomerate. . . . ................. . Shale. . . . ........................ . Sandy lime and pyrites. . ........... . Pack sand (shale) .................. . Shale and lime..................... . Sandy lime pyrites.................. . Pyrites rock....................... . Hard sand........................ . Rock pyrites. . .................... . Shale............................ . Sandy lime rock, sulphurous and gaseous Shale............................ . Sandy lime........................ . Shale.....•....................... Sandy lime........................ . Sandy shale. . ..................... . Sandy lime........................ . Sandy shale and lime................ . Sandy shale and lime (doby) ......... . Sandy shale and lime................ . Pure lime......................... . Pyrite............................ . Lime............................. . Shale............................ . Shale and lime..................... . Depth in From 1,244 1,250 1,369 1,426 1,494 1,519 1,535 1,542 1,556 1,580 1,634 1,654 1.688 1,697 1,736 J ,985 2,000 2,008 2,034 2,068 2,098 2,112 2,130 2,J52 2,176 2,177 2.186 2;192 2,194 2,195 2,219 2.222 2,224 2,232 2,233 2,234 2,257 2,260 2,262 2.263 2,270 2,2 7 6 2,277 2,294 2,312 2,326 2,340 2,341 2,350 2,352 To 1.250 1,369 1,426 1,49-± 1,519 1,535 1,542 1,556 1,580 1,634 1,654 1,688 1,697 1,736 1,985 2,000 2,008 2,034 2,068 2,098 2,112 2,130 2,152 2,176 2.177 2,186 2,192 2,194 2,195 2,219 2,222 2,224 2,232 2,233 2,234 2.257 2,260 2,262 2,263 2,270 2,276 2,277 2,294 2,312 2,326 2,340 2,341 2,350 2,352 2,411 Feet Thickness 6 119 57 68 25 16 7 14 24 54 20 34 9 39 249 15 8 26 34 30 14 18 22 24 1 9 6 2 1 24 3 2 8 1 1 23 3 2 1 7 6 1 17 18 14 14 1 9 2 59 Interpretation: The interpretation of this well has already been given. The Austin is regarded as extending from 1736 to 1983 feet; the Eagleford from 1985 to 2034 feet; the Buda from 2034 to 2068 feet; the Del Rio from 2068 to 2176 feet. At or near 2176 feet the Georgetown-Edwards limestones are entered, in which for­mations the well probably terminates. Log of Cartwi:ight No. 3, l:nit.ed Xorth and South Oil Company, Located to the East of, and N car Cartwright Ko. 2 Depth in Feet From To Thickness Surface........................... . o 7 7 Sand, shale and gravel. ............. . 7 36 29 Broken rock....................... . 36 5!l 23 Sandy shale. . ..................... . 59 85 26 Rock............................. . 85 86 1 Clay............................. . 86 89 3 Rock............................. . 89 90 1 Clay............................. . 90 120 30 Rock............................. . 120 125 5 Hard shale........................ . 125 145 2D Hard shale........................ . 145 304 159 Boulder.......................... . 304 306 1 Gumbo........................... . 305 416 111 Shale............................ . 416 ' 467 51 Rock............................ . 467 468 1 Hard shale........................ . 468 516 48 Rock............................. . 516 518 2 Broken rock. . . .................... . 518 522 4 Shale and boulders~showing gas about 5501 522 595 73 Gumbo............................ 595 629 34 Rock. . . ........................ , 629 631 2 Gumbo and boulders................ . 631 647 16 Sticky shale....................... . 647 713 66 Rock............................. . 713 714 1 Shale and boulders................. . 714 780 66 Gumbo........................... . 780 796 15 Shale............................ . 796 803 7 Gumbo........................... . 803 821 lS Gumbo and lime.................... . 821 838 17 Hard sh.ale........................ . 838 843 5 Gumb1................... , ....... . 843 864 21 Shale and sorne gas ................ . 864 893 29 Gumbo........................... . 893 944 51 Shale............................ . 944 995 51 Gumbo........................... . 995 l,UU~ 10 Soft lime......................... . 1,005 1,008 3 Gumbo........................... . 1.008 1,012 4 Gumbo........................... . 1,012 1,063 51 Hard shale........................ . 1,063 1,071 8 Shale and gumbo................... . 1,071 1,079 8 Gumbo........................... . 1,079 1,144 6" Mucky shale....................... . 1,144 1,190 46 Shale and shells. gas showing......... . 1,180 1,220 30 Mucky shale. ..................... . 1,220 1,235 15 Gumbo........................... . 1,235 1,320 85 Mucky shale....................... . 1,320 1,344 24 Shale and shell. .................... . 1,344 1,375 31 Mucky shale....·.................. . 1,375 1,420 45 Gumbo........................... . 1,420 1,429 9 Shale............................ . 1,429 1,500 71 Gypsy gumbo...................... . 1,500 1,525 25 Shale, lime, shell. . ................ . 1,525 1,622 97 Hard shale and lime................ . 1,622 1,637 15 The Prodiicing Horizon in the Rios Well 33 Depth in Feet From To Thickness Gyp-gumbo........................ . 1,637 1,675 38 Mucky shale....................... . 1,675 1,695 20 Gyp-gumbo........................ . 1,695 1,709 14 Shale and boulders, sorne gas ......... . 1,709 l,1::rn 27 Hard shale, gumbo................. . 1,736 1,760 24 Broken lime....................... . 1,760 1,790 30 Took tape line measurement 1795' .Austin chalk-use roller bit.......... 1.790 2,004 214 Shale and lime.. . . . . . . . . . . . . . . . . . . . . 2;004 2,019 15 Broken chalk and shale... . . . . . . . . . . . . 2,019 2,034 1.5 Shale and gypsum................... 2,034 2,036 2 Buda lime.......................... 2,036 2,058 22 Clay............................. ·' 2,058 2,060 '2 Lime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,060 2,087 27 Interpretation: .Austin, 1760 to 2004; Eagleford from 2004 to 2036; Buda entered at 2036 feet. Cartwright 3 was abandoned on account of difficulties in drilling and a second well started on this locaiity, kno•vn as Cartwright 4. In Cartwright 4 chalk is recorded as extending from 1768 to 1994; Eagleford shales from 1994 to 2035: Buda limestone entered at 2035 feet. Depths in both wells cor­rected by steel line measurements. Log of United North and South Oil Co.'s Rios No. 1 Wcll, Caldwell County. Surface clay. . .................. . Sand and gravel. ................ . Gummy shale and boulders. . ... . Gumbo, boulders. . .............. . Gumbo. . .................. · ... · Sand and gravel. ................ . Shale and boulders. . ............. . Gummy shale. . ................. . Gumbo and boulders. . ............ . Rock. . ........................ . Gummy shale. . ............... . Rock. . ...................... . Gumbo and boulders ................ . Rock. . ....................... . Gummy shale. . . . . . . ......... . Gumbo. . ..................... . Rock. . ........................ . Gumbo. . .......... · .. · · · · · · · · · · Shale and boulders. . ............ . Gumbo. . ...................... · Shale and boulders. . ............ . Gumbo. . ...................... . Shale and boulders. . ........... . Saltwater sand. . ................ . Shale and boulders. . ............ . Gumbo. . ....................... . Shale and boulders. . ........... . Gummy shale. . ................. . Chalky shale. . .................. . Chalk and shell. ................ . Hard sandy shale. . ............. . Gumbo. . ...................... . o 25 55 115 171 176 197 282 430 480 482 514 517 564 565 609 620 627 . 638 703 724 1,055 1,130 1,175 1,195 1,270 1,29 o 1,3 85 1,405 1,440 1,499 1,570 25 55 115 171 176 197 282 430 480 482 514 517 564 565 609 620 627 638 703 724 1,055 1,130 1,175 1,195 1,270 1,290 1,385 1,405 1,440 1,499 1,570 1,630 25 30 60 56 5 21 85 148 50 2 32 3 47 1 44 11 7 11 65 21 331 75 45 20 75 20 95 20 35 59 71 60 Chalk rock........................ . Hard shale and shell. ............... . Broken chalk and shale.............. . Hard rock and pyrites............... . Broken chalk rock. .. ............... . Lime rock......................... . Shale............................ . Limy rock......................... . Gray marl at...................... . Gray marl and yellow limestone at .... . Fine grained limestones at ........... . Yellowish gray porous limestones at ... . Light gray marl at................. . Yellowish gray porous rock at........ . Gray marl at...................... . Sand (?) Containing oil.............. . Depth in From To 1,630 1,868 1.868 1,875 1,875 1,905 1,905 1,911 1,911 1,918 1,918 1.955 1,955 1,961 1,961 2,005 2,005 2,136 2,139 2,144 2.155 2,157 2,158 2,161 Feet Thickness 238 7 30 6 7 37 6 44 Interpretation: This well starts in the Wilcox and enters the Austin at or near 1,635 feet. The formations below the Austin are difficult to interpret from the driller's log, but from an examina­tion of a number of samples it seems probable that the-formations penetrated include the Eagleford, Buda and Del Rio, the well ter­minating in the Georgetown-Edwards limestones. The record at and below 2,005 feet is made up from samples, except the last entry which is the driller's record. (See Fig. 1.) Log of the C. T. Schawe \Vell in Caldwell County (Elevation B. M. at Maxwell is 604. Completed in 1914. Casing: 600', 10"; 800', 8"; 6" set from 1400' to 3312' with 300' of SQreen at bottom.) Depth in Feet From To Thickness White rock. .. ..................... . o 10 10 Gravel. .......................... . 10 14 4 Rock............................. . 14 15 1 Yellow clay_ ...................... . 15 54 39 Black soapstone. . . . ............... . 54 90 36 Blue gumbo. . . ................... . 90 110 20 Soapstone......................... . 110 120 10 Blue gumbo....................... . 120 164 44 Black shale. . . ................... . 164 234 70 Black gumbo...................... . 234 374 140 Shale............................. . 374 399 25 White gumbo...................... . 399 659 260 Shale............................ . 659 690 31 'IVhite gumbo...................... . 690 760 70 White rock, show of oil............. . 760 1,03 6 276 Gumbo........................... . 1,036 1,071 35 White lime rock. . . . ............... . 1.071 1.113 42 \Vhite rock........................ . 1,113 1,142 29 Brown rock, porous................. . 1,142 1,354 212 Brown rock, porous ................. . 1,3ii4 1,425 71 Erown rock, porous ................. . 1,425 1,470 45 Brown rock....................... . 1,470 1,516 46 White rock, very hard, sulphur....... . 1.516 1,524 8 Brown rock. porous, with hard white layers. . . . ..................... . 1,524 1.567 43 Depth in Feet From To 'l'hickness Gray rock, hard. . . . . . . . . . . . . . . . . . . . . 1,567 1,615 48 Rock, porous, sulphur water. . . . . . . . . . 1,615 1.629 14 Hard gray rock, sulphur water.. , . . . . . 1,629 1,652 23 White lime rock.. . . . . . . . . . . . . . . . . . . . 1,652 1,786 134 Hard gray rock.. .. .. . .. .. . .. .. .. .. . 1,786 1,808 22 White lime rock. . . . . . . . . . . . . . . . . . . . 1,808 1,843 35 Brown rock, layers white. . . . . . . . . . . . . 1.843 1,922 79 Hard white rock. . . . . . . . . . . . . . . . . . . . 1,922 1,929 7 Brown rock, layers white.............. 1,929 1,961 32 Brown rock. . . . . . . . . . . . . . . . . . . . . . . . 1,961 2,038 77 Gumbo, mud hole. . . . . . . . . . . . . . . . . . . 2,038 2,046 8 Brown rock, very hard. . . . . . . . . . . . . . . 2,046 2,054 8 Brown porous rock. . . . . . . . . . . . . . . . . . 2,054 2,161 107 Hard gra,y rock...................... 2,161 2,175 14 Soft gray rock.. . . . . . . . . . . . . . . . . . . . . 2,175 2,238 63 Hard gray rock. . . . . . . . . . . . . . . . . . . . . 2,238 2,284 46 Gumbo, mud hole. . . . . . . . . . . . . . . . . . . 2,284 2,290 6 White lime rock. . . . . . . . . . . . . . . . . . . . . 2,290 2,377 87 Soft brown rock, show of water........ 2,377 2,462 85 Brown rock, white layers............. 2,462 2,498 36 Hard brown rock. . . . . . . . . . . . . . . . . . . 2.498 2,525 27 Gray sand rock. . . . . . ... . . . . . . . . . . . . . 2,525 2,540 15 Soft brown rock.. . . . . . . . . . . . . . . . . . . . 2,540 2,677 137 Hard white lime. . . . . . . . . . . . . . . . . . . . 2,677 2,717 40 Soft yellow sand rock................ 2.717 2,763 46 White lime rock..................... 2,763 2,773 10 Yellow sand rock. . . . . . . . . . . . . . . . . . . . 2,773 2,907 134 Hard blue rock. . . . . . . . . . . . . . . . . . . . . 2,907 2,918 11 Hard gray rock..... -'. . . . . . . . . . . . . . . 2,918 2, 937 19 Yellow sand rock. . . . . . . . . . . . . . . . . . . 2,937 2,986 49 White sand rock. . . . . . . . . . . . . . . . . . . . . 2.986 3.025 39 Gumbo, mud hole. . . . . . . . . . . . . . . . . . . 3.025 3,061 36 Yellow rock, gumbo mixed.. . . . . . . . . . . 3,061 3,070 9 Red and blue gumbo, mixed. . . . . . . . . . . 3,070 3,104 34 Hard white sand rock. . . . . . . . . . . . . . . . 3,104 3,J 17 13 White sand rock, soft and hard streaks.. 3,117 3,312 117 The driller·s log extends to 3,312 feet only. However, samples were obtained at intervals to a der1th of 3,445 feet. Description of these samples follow: Descriptions of samples from C. T. Schawe Well at Maxwell. Samples obtained by Alexander Deussen. BY J. A. UDDEN Depth in Feet Reddish-brown, medium-grained, quartzitic, calcareous sand; sand consists largely of sub-angular clear quartz grains. Other minerals present are ortho­clase (?), hornblende, hematite, etc. Trinity sands. (11 ft.).. . . . . . . .. .. . .. .. .. . .. .. . . .. . . .. .. . . . .. .. . 3323 Medium coarse-grained red sand. slightly calcareous; sand consists of angular grains of clear quartz. and fragments of hematite, orthoclase ( ?) , etc.; quartz is predominant. Typical Trinity formation. (20 ft.) 3375 Depth in Feet Reddish-brown, slightly caicareous, medium coarse­grained sand; cclor is not so red as preceding; sand consists chiefly of angular clear quartz grains aver­aging .5 mm. in diameter; also present limonite, hematite, orthoclase ( ?) , etc. Trimty formation. ( 15 ft.). . . . . . . . .. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 3405 Large fragments of red, compact, non-calcareous shale; sorne large angular fragments of greenish-grey talc­like compact non-carcareous shale; sorne large fragments of angular milky quartz, averaging Ys inch in diamcter. This material talrnn out while bailing the well. l\farJ:ed as sample No. 5. Repre­sents probably the Trinity formation.. . . . . . . . . . . . . 3400 Fragments of bluish-black, non-calcareous shale; nm­terial is friable; a few grains of quartz possibly from the stratum above. :\faterial has an entirely different aspect and color from the materials above. Probably represents Carboniferous or earlier. (10 ft.) ......................... ·--·.................. 3415 Fragments of blue, non-calcareous shale; friable. Car­ boniferous (?). (10 ft.). . . . . . . . . . . . . . . . . . . . . . . . . 3425 Small, sub-angular fragments of drab, non-calcareous shale. Carboniferous ( ?) . (14 ft.) . . . . . . . . . . . . . . . 3439 Sub-angular fragments of blue and gray non-calcareous shale. Material pulverizes into small fragments averaging .5 mm. in cl'.ameter. (6 ft.). . . . . . . . . . . 3445 Interpretation of the log: This well, starting probably in the Navarro formation, apparently enters the Austin at 760 feet and passes the base of the Austin at 1,036 feet. The Eaglefórd probably extencls from 1,036 to 1.071 feet, being loggecl as "gumbo." The Lower Cretaceoas apparently extends from 1,071 to 3,405 feet. From 3,405 to 3,445 feet the formation is identified by Dr. J. A. Udden as inclicated in the description of the samples, as pre­Cretaceous. Log of the Te'>:as Southern Oil and Lease Syml.lcate's Thompson No. 1, 2% l\Iiles S. E. 01' PraiI-ie Lea, Cald.wen Connty Depth in Feet From To Thickness Clay and grave]. ................... . o 35 35 Rock............................ . 35 53 18 Shale............................ . 53 88 35 Rock...................... _...... . 88 94 o Gumbo........................... . 94 135 61 Shale (oil ancl gas showing) .......... . 155 160 5 Gumbo........................... . 160 455 295 Shale............................. . 455 47i 20 Depth in Feet From To Thickness Gumbo. . ...................... . 475 494 19 Shale. . ....................... . 494 514 20 Gumbo. . .................... . 514 525 11 Rock. . ........................ . 525 528 3 Gumbo. . ................... . 528 545 17 Sandy shale (showing gas). . ..... . 545 555 10 Rock. . ........................ . 555 5 60 5 Gumbo. . . . . . . . . . . . . . ....... . 560 588 28 Sandy shale. . . . . . . . . . . . . . . . . . .. . 588 610 22 Gumbo. . ...................... . 610 628 18 Sandy shale. . .................. . 628 636 8 Gumbo. . ...................... . 636 680 44 Shale (showing of oil and gas) ....... . 680 684 4 Gumbo........................ . 684 698 14 Shale (showing of oil). . ......... . 698 710 12 Gumbo. . ................... . 710 7 3 o 20 Shale. . ...................... . 730 739 9 Gumbo. . ...................... . 739 751 12 Shale. . ........................ . 751 764 13 Gumbo. . ...................... . 764 772 8 Shale and streaks of gumbo. . . . . . . . . . 772 812 40 Gumbo. . ................... . 812 823 11 Shale and gas. . .............. . 823 830 7 Gumbo. . ...................... . 830 848 18 Shale. . ....................... . 848 855 7 Soft gumbo. . .................. . 855 861 6 Hard gumbo. . ............... . 861 871 10 Shale. . . . . . . . . . . . . . . . . . . . . . . . . 871 890 19 Gumbo. . ....................... . 890 89 5 5 Shale. . . . . . . . . . . . . . . . . . ...... . 895 901 6 Hard gumbo. . ................. . 901 932 31 Shale (showing of oil and gas) ....... . 932 945 13 Sticky shale. . .................. . 945 9 9 8 43 Shale. . ...................... . 998 1,011 13 Gumbo with streaks of shale. . ..... . 1,011 1,037 26 Gumbo. . ..................... . 1,037 1,058 21 Shale. . ....................... . 1,058 1,070 12 Gumbo......................... . 1,070 1,078 8 Sticky shale. . .................. . 1,078 1,200 122 Gumbo. . ...................... . 1,200 1,300 100 Shale. . ....................... . 1,300 1,334 34 Gumbo. . ..................... . 1,334 1,345 11 Shale. . ....................... . 1,345 1,407 62 Gumbo. . ..................... . 1,407 1,411 4 Shale. . ....................... . 1,411 1,445 34 Gumbo. . .........•............ 1,445 1,478 33 Shale. . ........................ . 1,478 1,493 15 Gumbo. . ..................... . 1,493 1,49 8 5 Shale. . . . . . . . . . . . . . . . . . . . . . . . . 1,498 1,620 122 Gumbo. . ..................... . 1,620 1,633 13 Shale. . ......•......•.......... 1,633 1,674 41 Gumbo. . ...................... . 1,674 1,700 26 Shale. . . . . . . . . . . . . . . . . ........ . 1,700 1,721 21 Gumbo. . ...................... . 1,721 1,735 14 Shale (good gas pressure showing of oil) 1,735 1,835 100 Austin chalk. . ................ . 1,835 2,050 215 Gray shale (oil). . ............. . 2,050 2,063 13 Depth in Feet From To Thickness Black shale. . . . ................... . 2,063 2,067 4 Slaty shale (black) ................. . 2,067 2,073 6 Shale and lime (oil) uncertain ....... . Gray limestone (large per cent of sand) Total depth........................ . 2,092 At 2,063 to 2,067 there was suffcient gas to shake the fioor of the derrick. Interpretation: This well, which is located to the east of and near the Cartwright wells, enters the Austin at 1,835 feet, drillers record. No samples have been obtained, but from the log it seems probable that the base of the Austin was passed at 2,050 feet, and that the gray and black shales from 2,050 to 2,073 represented the Eagleford, the gray limestone next below being probably the Buda. The depth given in the log are those recorded by the driller. A steel line measurement made after the well had been completed and cleaned is said to have indicated that the total depth of the well is 2,044 feet, or 48 feet less than the depth given in the· drillers record. This correction of 48 feet is to be applied in whole or in part to the Austin chalk and other formations in the well. THE GHoRMLEY WELL IN GUADALUPE CouNTY In a well now being drilled by the United North and South Oil Company, on the Ghormley farm, near Sullivan, in Guada­lupe County, chalk is recorded by the driller at having been entered at 2084 feet. From a core taken at 2371 feet (corrected depth) E. W. Brucks has obtained a shell, which appears to be the right valve of Exogyra arietina, a fossil characteristic of the Del Rio formation. INDEX Page Anomalina ....................12, 13, 14, 21, 22, 23, 24, 26, 27 Anomalina ammonoides................................15, 24 Anomalina grosserugosa...................................15 Austin Formation......................................6, 10 Austin Quadrangle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Balcones Escarpment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Bituminous material. .................................11, 15 Bryozoan...............................................12 Buda formation ...................................10, 11, 18 Bythocypris............................................13 Carrizo formation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Cartwright wells..................................10, 28, 18 Cavern deposit...........................................17 Clear Fork Creek, exposures on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Cristellaria...........................21, 21, 22, 23, 24, 26 Cristellaria cultrata............................12, 15, 16, 24 Cristellaria gibba..............................14, 15, 16, 24 Cristellaria mamilligera...................................15 Cristellaria obtusata ......................................15 Del Rio formation .................................10, 12, 18 Dentalium.............................................15 Dolomite........................................12, 13, 15 Eagleford formation ...................................10, 11 Echinoid spínes...................................15, 2 2, 2 3 Edwards limestone.........,.................................. 9, 13 Exogyra arietina ..................................10, 12, 20 Fault on San Marcos River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Físh scales .......................................11, 21, 23 Frondicularia....................................15, 21, 24 Georgetown formatíon.........................................9, 12 Ghormley Well in Guadalupe County.........,.....................38 Glauconíte........ , ..........................14, 16, 21, 25 Globigerina .....·...11, 12, 13, 15, 16, 17, 22, 23, 24, 25, 26, 27 Inoceramus..............1, 13, 15, 16, 17, 21, 22, 23, 24, 26 Ivy, exposure near. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 .Toliet, well near. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . & Hill, R. T...............................................18 Lagena.........................................11, 15, 24 Local Structural Condítíons............................... 7 Lockhart, Midway exposure near. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Lower Cretaceous, productíon from .........................2 7 Lulíng well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Maxwell, well near. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Page Mercer farm well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Midway formation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Mount Selman formation ............. : . . . . . . . . . . . . . . . . . . . . 5 Navarro formation ....................................... 5 Nodosaria .........11, 12, 13, 14, 15, 16, 21, 22, 23, 24, 25, 26, 27 Nodosaria consobrina..................................13, 15 Nodosaria nítida .........................................15 Nodosaria pauperata..................................13, 16 Nodosaria obliqua........................................15 Nodosaria radícula ....................................13, 15 Nodosaria zippei ......................................12, 15 Oil from the Rios Well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Orbulina............................11, 12, 23, 24, 25, 26, 27 Orthoclase. . . . . . . ...................................3 5, 36 Ostracods ................11, 12, 15, 16, 21, 22, 23, 24, 25, 26 Otoliths............................................15, 21 Polymorphina....................................12, 1~3, 24 Polymorphina compressa..................................15 Polymorphina .1actea......................................15 Producing horizon in Ríos Well.......,. . . . . . . . . . . . . . . . . . . . . . 9 Pulvinulina...............................13, 15, 17, 23, 24 Regional Structural Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Requienia patagiata.........................................., ..12 Ríos Well.....................................8, 18, 19, 33 Rotalia............................................14, 15 San Marcos, faulting near. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 San Marcos River, exposures on....... . . . . . . . . . . . . . . . . . . . . . 6 Schawe well.............................................34 Seashore, P. T....................................10, 21, 23 Sharks tooth............................................13 Shoal Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......18 Sponge Spicules ..........................................12 Spirillina. . . . . . ........................................15 Taylor formation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Textularia............11, 12, 13, 16, 17, 21, 22, 23, 24, 25, 26 Textularia sagittula......................................15 Thickness of formations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Thompson well..........................................3 6 Tritaxia.................................15, 21, 22, 23, 26 Tritaxia globigerina......................................21 Truncatulina....................................... . 12, 2 3 Truncatulina refulgens....................................15 Udden, J. A....................................8, 11, 17, 35 Vaginulina....· ..............................16, 21, 22, 23 Wilcox formation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5