un1vers1ty of Texas ::Pu'blioe.ttone 
University of Texas Bulletin 
No. 1850: September 5, 1918 

The Geology of Coke County 
BY 
J. W. Beede and W. P. Bentley 
Bureau of Economic Geology and Technology 
Division of Economic Geology 
J. A. Udden, Director of the Bureau and Head of the. Division 


PUBLISHED BY 
THB UNIVERSITY OF TBXAS 
AUSTIN 

Publications of the University of Texas 
Publications Committee : 
FREDERIC DUNCALF C. T. GRAY KILLIS CAMPBELL E. J. MATHEWS 
D. B. CASTEEL C. E. ROWE 
F. W. GRAFF A. E. TROMBLY 
The University publishes bulletins six times a month, so numbered that the first two digits of the number show the year of issue, the last two the position in the yearly series. (For example, No. 1701 is the first bulletin of the' year 1917.) These comprise the official publications of the University, publications on humanistic and scientific sub­jects, bulletins prepared by the Bureau of Extension, by the Bureau of Government Research, and by the Bureau of Eco­nomic Geology and Technology, and other bulletins of gen­eral educational interest. With the exception of special nqm­bers, any bulletin will be sent to a citizen of Texas free on request. All communications about University publications should be addressed to University Publications, University ef Texas, Austin. 
1328-6419-12-30-20-3 500 

University of Texas Bulletin 
No. 1850: September 5, 1918 
The Geology of Coke County 
BY 
J. W. Beede and W. P. Bentley 
Bureau of Economic Geology and Technology 
Division of Economic Geology 
J. A. Udden, Director of the Bureau and Head of the Division 

l'UBLISHED BY THE UNIVERSITY SIX TIMES A MONTH, AND ENTERBD AS 
SECOND·CLASS MATTER AT THE POSTOFFICE AT AUSTIN, TBXAS, 
UNDER THE ACT OF AUGUST 24, 1912 

The benefits of education and of useful knowledge, generally diffused through a community, are essential to the preservation of •a free govern­ment. 
Sam Houston 
Cultivated mind is the guardian genius of democracy. . . . It is the only dictator that freemen acknowl­edge and the only security that free­men desire. 
Mirabeau B. Lamar 
THE GEOLOGY OF COKE COUNTY 
By 
J. W. BEEDE and W. P. BENTLEY 
TABLE OF CONTENTS 
Introduction --------------------------------····-------------------------------------------------· 'I Geography and Physical Geography................................................ 7 History -----------------------·-----------------···········---------------------------------------· 13 Stratigraphy ..................... : ................. : ...... -----·------------······-----------... 16 Permian -----···················--------·················-----------····················-------' 16 Clear Fork Stage -················--------············-······························ 16 Choza ·Formation -------------·······-------------------·······-----------·------17 Double Mountain Stage ----------·--------······_.··········---------··········· 1() San Angelo Formation.......................................................... 19 Eskota or Greer formation.................................................. 29 Quartermaster (?) Formation ···-··························---------··---39 Logs -----------·--------·-·······-······----·········----·····················-----·----·-------------41 Correlation ·······-·---------------·······-·-·········------··---------------·-----·······-·-···· 49 Comanchean ------------------·---------------···----------·----·-·····---------------------53 Tertiary -----··········-···························-··---------·-··-------··· ······--·:......... 59 Recent ·---·------·------------··---------···-------··········-------------·-·····-------·-··----60 Economic Geology -----------------------------------····-·----······---·-·····----------·--60 Sand ···-----···········-···-······-···------------·---------------------------------····-········· 60 Clay ------------------·-·········--·····----------····-------····:--··--·······-········--·-------61 Lime ................. : .. ·----····--------··-·-------···-·-------·······---········-·······------62 Limestone ----------·-----·············-·················-------------·---············--·-······ 62 Gypsum ------·----------······---·········---····--·-·---········---··········-·················· 63 Road Metal ·-------·------·-----------------·····--------------------------------··----··------64 Oil and Gas -------.------·······················--------·····-························--------65 Structure -------------·----------------------------------···--------······-···--·····--·---65 Oil and Gas Possibilities..--------·-·--------···--------··········--··········-··· 77 
LIST OF ILLUSTRATIONS 
Figure 1. Sketch map showing physiographic r egions of Texas and location of Coke County___________ _________ __________________ _____ _____ __ 8 
Figure 2. S~etch map of Coke County region, showing Ed­wards Plateau, Callahan Divide, and Colorado River Valley 9 
Figure 3. Section across Coke County, showing Colorado River Valley -------------------------~--------------------------------------------------10 
Plate I. Geologic map of Coke County, in pocket. 
Plate II. A. Two monadnocks of the Callahan Divide. Kick­apoo Mountain in the foreground, Hayrick 
Mountain in the left background. Remnants 
of the Edwards Plateau. 

B. 	One of the Table Mountains at Table Gap, Run­nels County. Another relic of the former extent of the Edwards Plateau________________________ 12 
Plate III Pecan Creek running on bed rock and deepcni!1g its channel ------------------------------------------------------------12 
Plate IV. A. Joints in dolomit'.c limestone resting on clay 
shale. Choza formation, western Runnels 
County. Looking east. 

B. Another view at the same locality, looking south 13 
Plate V. A. Stepp Mountain. The lower part is Quarter­master (?) and the upper part is Comanchean. 

B. 	Undercut rock, Comanchean, on north side of Grubbs Canyon ------------------------------------------------60 
Plate VI. A. San Angelo conglomerate at Kickapoo Mountain. 
B. San Angelo gravel at Mount Margaret_____ ___________ 64 
Plate VII. Seaton Keiths Bluff, 3 miles west of Robert Lee. Eighty feet of Greer sandstone followed un­conformably by 40 feet of limestone con­glomerate, shown above the line A-A._______ 66 
Plate VIII. Diagram, Colorado River section______ ______________ _____ __ ____ _ 68 : Plate IX. A. Bluff on South Pecan Creek showing crushed B-C. Rocks in normal position on either side, and leached zone A-B and C-D. 
B. 	A closer and more direct view of the left side of "A" --------------------------------------------------------------68 
Plate X.  A. Reversed fault in  bluff  on  Pecan Creek, above  
Arlitt ranch-house.  
B. Crumpled shale, slightly faulted, between undis­ 
turbed  sandstone  beds in  same  bluff____________  68  
Plate XI.  Large  normal  fault  on  Pecan  Creek_________ ____ ____ _______  70  
Plate XII.  East side of  a  fault  zone  above  the  Arlitt ranch­ 
house  on  Pecan Creek  -------­---------------------------­ 70  
Plate XIII.  West side of fault block shown in  Plate 12____________  70  
Plate XIV.  A. Bluff on South Pecan Creek showing the effect of  
solution of gypsum beds from between clay  
and soft sandstone beds.  
B. Oil showing in highly cross-bedded sandstone in  
the  bed  of  Mountain  Creek  just  east  of  
Robert  Lee  -------·-------­-----------­-------------------------­ 80  
Plate XV.  Map  showing hypothetical  extension  of  Marathon  
Fold  ---------------·­--­-------------­-------------------------------­ 80  
Plate XVI. Vertical section of surface  exposures of the rocks  
of the Colorado. River section in Coke County  80  
Plate XVII.  Sections of four deep borings:  Stroud No. 1. at  
Robert Lee and Westbrook No. 1 at Tenny­ 
son, in  Coke County; Cain No.  1  near  San  
Angelo, Tom Green County; Richardson No.  
1,  Sterling County;  with  correlation.  (In  
pocket.)  

THE GEOLOGY OF COKE COUNTY1 
By J. W. BEEDE and W. P. BENTLEY 
INTRODUCTION 
The geology of Coke County was worked out in connec­tion with the study of the section of the Permian rocks as exposed along the Colorado River. This section and the larger structural phenomena encountered constituted the main work within the county. The areal geology received minor consideration and is somewhat generalized. The study of the Comanchean beds was general. However, it is hoped that the treatment of the county as a whole will prove to be of value, and that some contribution has been made to the knowledge of it. 
Mention should be made here of the generous assistance given us by the people of the county and especially to Mr. Charles Escue who devoted much time to assisting us with his detailed know~edge both of.the land surveys and of the geology of the county. 


GEOGRAPHY AND PHYSIOGRAPHY 
Coke County is situated just southwest of the center of the state in what is usually referred to as "West Texas." It is about twenty-six and one-half miles wide by thirty­three and one-half miles long and has an area of approxi­mately 888 square miles. The Colorado River flows south of east through the central part of the county. The main trib•Jtaries of the stream from the north are: Kickapoo, Co~, Indian, Mountain, Messbox, Yellow Wolf, Rough, Meadow, Sand and Silver creeks. All these streams rise on the Callahan Divide and flow south into the river. Those on the south side rise on the Edwards Plateau and flow north into the river. They are: Mule, Live Oak, Wild Cat, 
. 1Manuscript accepted December, 1920; published March, 1921. 
University of Texas Bulletin 
Paint, Salt, Pecan, Rough, Gasconade, and Heifer creeks. 
The surface of the county is, on the whole, rough. The "mountains" on the north and south sides of the river rise from 100 to 500 feet above their bases. The valley region between the mountains is fairly well dissected and has an immediate relief, from creeks to divides, of 50 to 150 feet. The lowest point in the county, on the Colorado River, is ap­proximately 1700 feet above sea-level, and the highest known 
FIGURE 1 
Sketch map showing physiographic regions of Texas, and location of Coke County. Abbreviations: HP, Panhandle High Plains; LE, ;.,1ano Estaca<lo or Staked Plains; NCP, North Central Plains; CM, Central Mineral Region; EP, Edwards Plateau; TB, Toyah Basin; CR, Cordilleran Region; SP, Stockton Plateau; GP, Grand Prairie; 
GCP, Gulf Coastal Plain. The ruled area represents Coke County. 
point, about 10 miles west of Blackwell in the eastern half of the county, has an elevation of 2558 feet. Higher points may occur in the ·western two-thirds of the county. This gives a total relief of at least 858 feet. The mountains south of the river are not so high as those on the north side of.it, though they are composed of the same strata, which were 
FIGURE 2 Sketch map of Coke County region showing Edwards Plateau, Callahan Divide, and the Colorado River Valley. A-A, location of the cross section shown in figure 3. 
once continuous over the whole county. These upper (Co­manchean) beds dip, or slope, to the southeast, making them higher north of the river. 
The "mountains" in the south part of the county form the northwest part of the Edwards Plateau. This plateau is roughly bounded on the north by the Colorado River, on the south by the Pecos River, and extends from that section of the Balcones Fault scarp, or bluff, between Austin, San Antonio and Del Rio, northwest to the Staked Plains. The 
NoRTH AND SOUTH 5ECTION ACRoss CoKE CouNTY NEAR RoBERT · LEE 
ScQle of Miles 
0 I 1 3 ~ S 6 
')l! ) N 

Section across Coke County near Robert Lee, showing Edwards Plateau, Callahan Divide, the old Colorado River Valley, and the new valley within it. It also shows a cross-section of the geologic formations of the central part of the county. 
The Geology of Coke County 
plateau was once continuous and unbroken over all of Coke County to the Callahan Divide and much fartlier both north and west to the Staked Plains. At that V.me the Colorado River flowed in the same general direction that it now does and probably near its present position. At any rate, it was over some part of the present valley between the mountains. In the course of time this river and its tributaries excavated a great wide valley which had a relatively even surface and was well drained. This valley is shown in the cross-section as the "Old Valley." In this way the northern part of the Edwards Plateau was cut away from its main body by the work of the Colorado River. The tributaries of the Colo­rado and Brazos rivers have cut the northern part of the plateau into a series of "mountains" or mesas, all of which have been called the Callahan Divide. They are remnants of the old plateau and are called "monadnocks." Moro Mountain and the Table Mountains in Runnels County, the 
Kickapoo Mountains, Hayrick Mountain, Cole Mountain and the Stepp Mountains of Coke County, are all monad­nocks. A considerable part of the Callahan Divide forms the watershed between the Colorado River and the Brazos River. 
The limestones of the Plateau and Callahan Divide .ere 
much more resistant to erosion than the soft red sandstone3 
and shales beneath them. · As soon as the Colorado cut 
through the firmer -rocks into the softer beds below them, 
the river and creeks widened the valley rapidly by under­
mining the harder rocks. This process kept the bluffs steep 
and constantly crumbling in, with the result that the valley 
was widened much more rapidly than it would have been 
had all the rocks been firm. 
After the old valley had been excavated, either the land 
was uplifted or else the Colorado River finally cut a deeper 
trench through the harder rocks farther east, so that the 
velocity of its current was sufficiently increased to cut a 
deep channel through Coke County. Even now, wherever 
the river runs on bed rock, it is still deepening it channel. 
Under these conditions the new valley was carved in the 
floor of the old valley. Small bottom lands along the river 
University of Texas Bulletin 
have been formed by the meanciering stream. The creeks have cut deeply below the old valley and are still cutting down their beds in order finally to come into adjustment with the river. 
In this manner the once relatively plane ::iurface of the old valley has become quite rugged, and the larger creeks, like the river, have very little bottom land in their valleys. On account of the firmness of the Comanchean rocks of che Edwards Piateau and the Callahan Divide and the unresist­ant soft beds beneath them, the rise from the old valley to the plateau and mountains is abrupt, forming the steep walls of the Colorado River Valley. 
SINKS 
On the plateau are sinks and depressions which have no surface outlets. The open throats, or sinks, are frequently referred to as "blowouts" or "gas blowouts." In reality these holes or openings are simply solution holes dissolved at the cross joints, or cracks, in the limestone, by downward 
soakinll, rainwater. The water enters these cracks and slowly pa::ises down until a horizontal plane between the layers is reached along which it may follow and below which the joint is closed. This water next comes out at the sur. face as a seep, or intermittent spring, in some canyon; or perhaps may continue as an underground flow beneath the gravel and boulders in the bed of the canyon without emerg. ing as a surface stream. From the moment of its entrance into the rocks, the water begins to dissolve the limestone with which it comes in contact, until a vertical throat and horizontal channel are dissolved. These are called sinks, and caves, respectively. 
(The accompanying illustrations show joints in the layers in Comanchean limestone in the mountains, and in Permian limestones on the lower plains. The latter rest·upon soft clays which creep readily when wet, so that blocks are gradually pulled away from each other along the joint .cracks and creep down the slope.) 
University of Texas Bulletin No. 1850. 	Plate II 
A. 	Two monadnocks of the Callahan Divide. Kickapoo Mountain in the foreground, Hayrick Mountain in the left background. They are remnants of the Edwards Plateau. 
B. One of the Table Mountains at Table Gap, Runnels County. Another relic of the former extent of the Edwards Plateau. 

University of Texas Bulletin No. 1850. Plate III 
Pecan Creek running on bed rock and deepening its channel. 

University of Texas Bulletin No. 1850. 	Plate IV 
A. 	Joints in dolomitic limestone resting on clay shale. The larger (major) joints run from the foreground toward the back­ground. The joint blocks are separating and creeping down the slope during wet weather. The minor joints run from right to left. Western Runnels County, Choza formation. Looking east. 
B. 	Another view at the same locality, looking south. It shows the joints and joint blocks. The limestone here is creeping down the hill as in the other picture. 

The Geology of Coke County 
The water on entering the joints usually follows down the dip of the beds of the rocks. The normal dip of the Coman­chean rocks of the plateau in Coke County is south of east. Probably much of this water ultimately finds its way into the underflow of the North Concho River. Sometimes these throats become sealed with clay, and the water stands in the basin of the sink for considerable lengths of time. In such cases the water may enlarge the sink basin by dissolving the rocks around its rim. In this way these upland lakes may grow to have a considerable area. 

HISTORY 
The first account of the geology of Coke County accom­panied by a geologic niap was given by Professor W. F. Cummins and Dr. Otto Lerch, in a paper entitled, "A Geolog­ical Survey of the Concho Country, State of 'Texas."2 The "Concho Country" comprised Tom Green, Coke and Irion counties. In this article, the Permian, Cretaceous and later deposits were briefly described and mavped. In another ar­ticle,3 Lerch describes the San Angelo beds and gives their position between the Permian beds below and the Coman-" ehean rocks above, also mentioning the fact that they are unconformable with both th~ Permian and Comanchean. His description of the formation, briefly, is as follows: 
"Above this fossiliferous limestone (at Ben Ficklin) rests a quartz conglomerate about twelve feet thick. The pebbles are well water­worn, of small size and bound with a siliceous and irony cement. The conglomerate is stratified, dips toward the ·northwest under a steeper angle, however, than the underlying deposits, and is occasionally inter­spersed with large blocks of green and red speckled quartzite, The conglomerate is very hard, takes an excellent polish and is of a yellowish red color. Above it lies a series of red and yellow colored clays and sandstones, about one hundred feet thick, overlaid by lighter buff and whitish-colored thin beds of loose, friable sandstone and clays about fifty feet thick, followed unconformably by the Trinity sands." "I have traced this conglomerate for nearly twenty miles toward the north and its stratigraphic position with the beds above, below the Trinity sands .. .and propose for them the name 'San An­gelo Beds'." 
2Amer. Geo!., Vol. V, pp. 321-325, 1890. Map. 
3Amer. Geo!., Vol. VII, pp. 74-77, L891. 

Twenty miles northward from San Angelo along the out­
crop of these rocks would carry one to the vicinity of Mount 
Margaret, Coke County, where the best known exposures 
of the beds are to be found. There can be no question but 
that Lerch was following the prominent outcrop of these 
rocks from just north of San Angelo to the Mount Margaret 
region near Tennyson. 
Since his formation closely resembled the Triassic con­glomerate of the plains farther northwest, and appeared to be unconformable with both the overlying Comanchean and underIYlng Permian beds, Lerch referred them to the Tri­assic or "Jura-Trias," as described by Marcou. Lerch states that: "I am nowl inclined to think that this group of strata is of Triassic age and may be a southward continuation and thinning out of the strata 300 miles westward called Jura-Trias byi Jules Marcou, the occurrence of which below the Staked Plains was announced many years ago by him." It is now found that in following these beds westward, they pass conformably beneath the Double Mountain beds of the Permian, as will be shown in the following pages. In the ' first of these papers Cummins and Lerch gave a section of the Comanchean rocks with a list of species. of fossils; 
and discussed the later gravel, clay, and sand deposits. 
The San Angelo beds rest upon the Clear Fork beds. In 
order that the significance of the terms "Clear Fork" and 
"Double Mountain" may be clearly understood in the fol­
lowing discussion, their original as well as later definitions 
as modified and more clearly stated in later work are repro­
duced here. 
The first mention of the terms "Clear Fork" and "Double Mountain" beds was made by Dumble in the First Annual Report of the Geological Survey of Texas,4 in which some of the characters of each were mentioned. Their first full definition was given by Cummins on pages 186 to 189 of the same report. They were more fully described later in the Second Annual Report5 from which the· following state­ments were taken. 
4Pp. lxix-Ixx, 1890. 
'•Pp. 400-402, 1891. 

The Geology of Coke County 
Describing the Wichita, Clear Fork and Double Mountain beds, Cummins says : 
"I have separated the strata of the Permian into three divisions, under the names of Wichita Beds, Clear Fork Beds, and Double Mountain Beds. These divisions have been made more for the sake of convenience than for any other reason, especially the last two." 
After giving the location of the Clear Fork Beds, his definition of the Clear Fork and Double Mountain beds is as follows: 
"The Clear Fork Beds are composed of limestones, clay and shale beds, and sandstones . . . The sandstones are not so abundant as in the Wichita Beds, and are not so massive, but gen.erally thin­bedded. The clay:> ~re blue and red, the red occurring in thick, heavy beds . . ." 
In defining the Double Mountain beds their features are thus characterized: 
"These beds lie in direct contact with the Clear Fork Beds through­out the whole length, and no attempt has been made to determine a line of division between the two divisions. The beds are composed of sandstone, limestones, sandy shales, red and bluish clays, and thick beds of gypsum. The limestones are generally of an earthy variety, and in places have many casts of fossils, the newer types being more largely represented than the older. The gypsum beds are numerous and many of them are very thick. All the clays and shales are im­pregnated with gypsum, and many of them carry a large per cent of common salt. The ·sandstones are generally very friable and of various colors, red, white, ~nd spotted." . 
In short, the Clear Fork Stage is characterized by heavy shale beds, some sandstones and limestones. The Double Mountain stage is characterized by sandstones, thick gyp­sum beds, some sandy shales and earthy limestones. It should also be kept in mind that this differentiation was made in north Texas and not along the Colorado River. However, the definition holds very well for the Colorado River section. Indeed, the separation of the Double Moun­tain from the Clear Fork is much more definite and sharp than indicated by Cummins, both in the Colorado River region and in North Texas. This will be clearly shown in what follows. 
University of Texas Bulletin 


STRATIGRAPHY 

The oldest rocks exposed in Coke County are the upper 290 feet of the Clear Fork beds of the Permian system, found below Bronte along the Colorado River. Passing up the river from Cedar Mountain are the San Angelo beds, and a group of rocks between Robert Lee and the west line of the county, provisionally correlated with the Greer formation of western Oklahoma and the Panhandle of Texas. Both of these formations belong to the Double Mountain stage of the Permian system. In the northwest corner of the county is another formation, resting upon the Permian beds, which appears to belong to the Triassic sys­tem but which, as the point has not been determined with certainty, may well represent an unconformity at the base of the Quartermaster formation. The basal part of the formation is a very coarse quartz conglomerate, somewhat resembling the conglomerate in the San Angelo beds. 
In most of northern and southern Coke County the rocks of the Comanchean system (or Comanchean division of the Cretaceous system) rest upon the Permian strata, while in the northwestern part of the county they lie upon the rocks just mentioned. 
Over much of the Colorado River valley and the valley of the North Concho River are thick .deposits of gravel, boulders and silt. These deposits are above the immediate valleys of the individual streams, usually 80 to 150 feet above the Colorado River, and a less distance above its tributaries. The age of this gravel and boulder formation is uncertain. It probably belongs to the late Tertiary or Pleistocene. 
The soils, gravels and boulders of the lowest creek and river bottoms are of Recent age. 
Permian 
CLEAR FORK STAGE 
The lowest rocks exposed in the county are the Merkel dolomite and about 270 feet of shales above it. 
• 	17
The Geology of Coke County 
Choza Formation 
The Merkel dolomite is excellently shown in the bluff of a creek west of Bullnose Mound across the line in Runnels County, and constitutes numbers 1 to 14 of the following section: 
Section from Base of Merkel Dolomite as Exposed in Bluff West of Bullnose Mound and to the Base of the San Angelo Beds at Cedar Mountain. 
Feet Inches 
39. 	Shale, red, with green sandstone streak which is a dolomite locally; 1 foot of coarse brown sand­stone above; 2 feet of green shale on top . . .. 11 
38. 	Sandstone cemented with lime, 4 to 6 inches ; shale, 3 feet; some platy, or nodular-platy, green shale 4 
37. Shale, red ... . .. . ..... . .. . ....... . .... . .. ... . . 22 

36. 	Shale, 5 feet; dolomite, 4 inches; shale, 15 feet; platy dolomite sheet on top . . .. ... . ......... . 21± 
35. Shale, 18 inches; dolomite, thin, pink....... .... . 1 1 

34. Shale, red, 4 feet; 1 foot rotten dolomite .. ..... . 5 
33. Shale, red, and 1 foot of dolomite........ .... ... . 20 

32. Dolomite, 0 to ........ .... .................... . 0 6 

31. Shale, red .. ... . ............... . .. . . . ........ . 8 

30. Dolomite, rotten .. .... . . . . ... . .. . ... . ... . ..... . 1 
29. Shale, red ... . ........... . ... . ...... . ... . .... . 6 

28. Dolomite . . ........ . .... .... ..... . ...... . .... . 0 6 

27. Shale, red ................................... . 14 

26. Dolomite, 6 inches to ........... . . ... ..... . .... . 1 

25. Shale, red ..................... ......... ..... . 44 

24. Shale, red; some greenish thin dolomite on top ... . 16 
23. Shale, red . ..... .. ... . .. ... .... .. .... .. . . .... . 12 
22. Dolomite . . .. ...... .. .. . .. .. . . ....... ... .... . . 1 

21. Shale, red ............ .. .... .... ... ........... . 8 

20. Shales, variegated; dolomite on top ... . ... . .. ... . 15 
19. Dolomite bed ... ............................. . 1 

18. Shale, red ..................... .............. . 28 

17. 	Dolomite streaks, crystalline limestone and some soft sandstone, 10 to ......... .............. . 12 
16. Shale, red .......... . .... .. .... .. .......... .. . 14 

15. Shale, red, with 4 inches limestone on top . ...... . 10 4 
14. Limestone, irregular ... . . . ... . .... . ... .. . . .... . 1 
13. Shale .... . .... . ............... .. .. . ......... . 0 3 

12. Limestone . ....... ... .. . . .. . . .. . ........ . . .. . . 1 10 

University of Texas Bulletin 
11. Shale and granular limestone plate.... . . . . . . . .  1  6  
10.  Limestone  in 3 beds, platy, ripple-marked........  0  9  
9. Shale with  a  4-inch limestone in the middle . . . . . .  1  
8. Limestone, 3 beds; sheet of hematite on top . . . . . . .  1  6  
7. Shale, olive  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2  3  
6. Limestone, double bed, gray, 4 to 10 inches thick. .  0  8  
thick  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  0  8  
5. Limestone, shaly, 9 inches to.. . .. .. ... ... .......  1 ·  6  
4. Dolomite,  porous,  coarse-grained,  somewhat  brec­ 
ciated  at the top;  sheet of hematite 6 inches  
below  the  top . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2  
3. Shale,  gray  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  0  4  
2. Limestone, gray, earthy, dense,  rather ha;rd, thin  
beds  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1  3  
1. Limestone breccia  in  thin, warped beds,  some  of  
which are over a foot thick and cross-bedded. .  4·  

Numbers 1 to 14 of this section are the details of the Merkel dolomite bed as exposed in the bluff in a little creek west of Bullnose Mound near the county line. 
Beginning at the top of this limestone as exposed at Teneyck Ford southeast of Bronte, numbers 15 to 38 con­stitute the section from the Merkel dolomite to the base of the San Angelo beds as exposed in Cedar Mountain. Most of the section is to be seen on the south side of the Colorado River. · Tpe top of this section forms the top of the Clear Fork beds, in which shales predominate and soft gray im­pure limestones and magnesian limestones are prominent in surface exposures. Sandstones are relatively rare, thin, and red. 
An interesting feature in the Coke County exposures is the fact that as one goes west along an outcrop, thin dolo­mitic beds are seen to appear as parts of eastward pointing wedges. Somewhere in a shale exposure the end of a thin, light green band will be noticed, which gradually thickens toward the west. Careful examination of the point of it reveals a little calcareous cement in the sandstone or shale. If it is the latter, the streak is usually a little more sandy than the shale above or below it; Followed farther west the calcareous material increases and finally a thin bed of dolo­mite occupies the space. This is a phase of the change of 
The .Geo'logy of Coke County 19 
much of the clay and sandy sediments into limestones in a southwesterly direction. If we could follow these beds for enough we would probably find the limestone or dolomite or dolomite band thickening and the shale between them thinning. These thin beds and· some of the thicker ones appear as anhydrite in cuttings from the wells near Robert Lee. The total thickness of the Clear Fork beds in Run­nels and eastern Coke Countis is approximately 800 feet. 
DOUBLE MOUN!TAIN STAGE 
San Angelo Formation 
The rocks of the San Angelo formation rest unconform­ably upon those of the Clear Fork beds. Thus there are 270 feet of shales and thin limestones between the San An­gelo beds and the Merkel dolomite along the Colorado River, while near the Texas and Pacific Railroad only 25 feet of shale occur in this interval, according to Wrather.6 The San Angelo formation varies lithologically from place to place. In eastern Coke County it is largely composed of coarse conglomerate and sandstone with some shales, while at other localities it is of finer-grained material and con­tains more shale. The following sections reveal to some extent these different phases. 
Mount Margaret Section 
Feet Inches 
31. Limeston.e, massive ... .. . . . .... . . . . . ... ....... . 1 

30. Limestone, massive, weathers smooth, Caprina. .. . 5 
29. Limestone and concealed interval . .............. . 13 

28. Limestone, hard ................. ........... .. . 2 8 

27. Limestone, hard . .... . ....... ... ... ... . . . ..... . 5 

26. Limestone, somewhat flaky ... .. ... ..... ... ... .. . 4 
25. Limestone, very hard for these beds, fine-grained. 1 3 
24. 	Limestone, nodular, or hard nodular marl, quite 
fossiliferous, 10 feet 6 inches to .. .......... . . 11+ 

23. 	Limestone with geodes and large gastropods, pe­lecypods, etc. ; tends to weather into nodules ... . 4 
sProc. S. W. Petr. Geol. Assn. I, section, 1917. 
-University of Texas Bulletin 
22. Limestone, less resistant than number 21. . . . . . . . 4+ 
21. 	Limestone, massive, rotten, fine-grained, weathers to a smooth surface. . . . . . . . . . . . . . . . . . . . . . . . . 9 
20. Sandstone and sandy limestone. . . . . . . . . . . . . . . . . . 3 
19. Marls, fossiliferous . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 
18. Sandstone, buff, fine-grained, apparently calcareous 5 
17. Sandstones, algal, calcareous. . . . . . . . . . . . . . . . . . . . 2 
16. Clay, mostly olive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 
15. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 
14. 	Sandstone containing concretions the size of small marbles, approximately in place.. . ...... .. .. 2± 
13. Float from Comanchean rocks. . . . . . . . . . . . . . . . . . 50 
12. 	Shales, red, and some soft, thin, sandstone, hardly noticeable; possibly 10 to 20 feet or more cov­ered by float.... ........................... 50 
11. Sandstone, pink, less iron than in the one below.. . 2+ 
10. 	Sandstone, rather coarse, 20 feet thick at the place measured, upper part very ferruginous, many small iron concretions, some large ones, con­glomeratic in spots . . . . . . . . . . . . . . . . . . . . . . . . . 25 
9. 	Conglomerate contains some sandstone and shale 
lenses, coarsest about 25 feet above base.. .... 65 

8. Sandstone, top conglomeratic. . . . . . . . . . . . . . . . . . . . 5 
7. Conglomerate, 6 inches to. . ..... . .. . ... . . .. . .... 4 
6. 	Sandstone, buff, locally a conglomerate, with pebbles 
2 inches long, some concretions. .. . . . . . ..... . 4 

5. Concealed .. .. .. . . . .. . ............ . . .. ..... .. , . 8 

4. Sandstone, white-. laminated. . . . . . . . . . . . . . . . . . . . 1+ 
3. 	Shale, green, somewhat sandy, iron concretions, 
weathers buff in places. . . . . . . . . . . . . . . . . . . . . . 12 

2. Clay shales, red. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 
1. 	Sandstone, three layers with three beds of maroon 
sandy shale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Numbers 6, 7, and 8 of this section are all locally repre­sented by conglomerate. It is impossible to state just what thickness of sandstone and shale lies immediately below\ the base of this section. This is quite variable locally. Num­ber 10 is the top of the conglomerate beds which constitute the top of the San Angelo formation. On account of an inaccuracy discovered in the instrument used in measuring this section, some slight error may appear in the thickness of the beds, though this has been roughly corrected. The shales and sandstones between number 10 and the base of 
The Geology of Coke County 
the Comanchean probably represent a higher formation of the Double Mountain stage. 
Some of the coarser San Angelo conglomerate is cemented with iron, some has very little or no cement, and perhaps there are spots with calcareous-ferruginous, or even sili­ceous cement. Its appearance varies greatly from place to place. At Mount Margaret most of the large conspicuous pebbles are well rounded to subangular, iron-stained quartz pebbles. Associated with them are black and gray chert and other siliceous pebbles some of them rather intricately 
veined. There is some white and some reddish quartz. Some of the pebbles are 9 or 10 cm. in major diameter, .and range from that down to fine sand. Some of the peb­bles are coarse quartzite oxidized to a dirty dull brown and are thoroughly rounded. Most of the matrix of this con­glomerate is sand. 
A barometric section of these beds was published in the Runnels County report. 7 Later, a detailed section was mea­.sured for this report. At this locality and on Live -Oak Creek east of the Humlong ranch-house the conglomerate is very coarse, containing quartz boulders, thoroughly rounded and iron-stained; rounded and subangular chert; .some faulted and veined pebbles and boulders; and some quartzite. All minerals and rock less resistant to wear than silica are wanting. The size of grains and pebbles ranges from sand to cobbles.8 
North of Bronte, one of the features of' the lower beds of the formation is a series of layers oft brownish sandstone conglomerates with rather soft yellowish pebbles of ocher­·Colored shale. 
Permian Section at Kickapoo Mountain 
Feet Inches 
10. Shale, red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 
9. Sandstone, brownish, very even-bedded, 18 inches to 2 
8. Shales, red, and concealed beds. . . . . . . . . . . . . . . . . . 30 
7Univ. Texas Bull. 1816, p. 50, 1919. 
SGrabau. Principles of Stratigraphy, p. 287, 1913. 

University of Texas Bulletin 
7. Sandstone,  buff-gray  . . . . . . . . . . . . . . . . . . . . . . . . . .  2  3  
6.  Concealed  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2  6  
5. Sandstone, buff-gray, 3 feet to. . .................  4  
4. Shale, sandy, green and red, 8 feet to. . ..........  10  
3. Conglomerate.  16 feet of conglomerate at the base,  
the larger pebbles  an  inch or two in diameter,  
white and red quartz and black chert and some  
yellow-stained  quartz pebbles.  Matrix buffish­ 
sandy material. This conglomerate grades down  
to "chicken gravel" at the top of the bed.  The  
upper part has iron streaks in it and sandstone  
weathering gray-brown  . . . . . . . . . . . . . . . . . . . . .  26  
2.  Sandstone  8  feet  thick  in  place,  yellowish  or  
brownish-buff,  locally  conglomeratic.  Shales  
and  talus  below.. . . . . . . . . . . . . . . . . . . . . . . . . . . .  26  
1. Shales, blue, green, and brown, with some sandstone  
bands  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  76  

There is a considerable thickness of material below the base of the section which belongs to this formation. Far­ther north and a mile and a half east, the thickness between the top and base of the conglomerate is 277 feet. Itappears th1J,t some allowance should be made for an east dip which would leave from 200 to 250 feet, or even more, for the thickness of the San Angelo formation in this vicinity. East of Blackwell, the conglomerate is still finer and there are very large joint blocks of quartzite present, the cement being siliceous. Farther north still, in the region of the Texas and Pacific Railroad, this formation is a sandstone, or a series of sandstones and shales. 
It is worthy of note that the sandstones of the Clear Fork beds below the San Angelo formation which are of little im­portance in Runnels and eastern Coke counties, are largely red in color. In the San Angelo formation on the Colorado River they are buff or yellowish-brown and of quite differ~ ent t~xture. If the outcrop is followed northward across the Callahan Divide, the sandstones are found to be red. 
Above the San Angelo beds are 65 feet of the overlying Greer formation-numbers 4 to 10 of the section. 
The Geology of Coke County 
Cedar Mountafo Section Feet Inches _10. Conglomerate and standstone, 20 to 30 feet...... . 30 
9. 	Shales, sandy and clayey, containing small cal­careous nodules. Upper 2 or 3 feet of shales 
buff, carrying brown nodules, 10 feet to . . . . . . 20 

8. 	Sandstone conglomerate composed of fine-grained 
sandstone fragments, pebbles lighter colored 
than the matrix, followed by finer and less re­
sistant sandstone beds. In the upper part 
some of the beds are pale crimson to da,rk red­
brown tinged with purple. The sandstone con­
tains much iron in the south end of the mountain 42 

7. Shale, green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 
6. 	Shale, red, includes a 2-inch dolomite bed at 15 feet 
and another at 17 feet .. ... ........ .. . .... .. 27 

5. 	Shale, red, 5 feet; dolomite, drab, 4 inches; breaks into 70 degrees parallelopipeds, somewhat finely crystalline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 
4. 	Dolomite, shaly or platy, shows strongly the im­pression of sun cracks in the shale below. Forms top of main fiat-topped hillocks. An­other thin bed above it. ........ . ..... ... . . . . 3+ 
3. Shale, red, gray streak at top, sun-cracked . . . . . . . 8 
2. 	Dolomite; quartz or barite present. Ledge prom­inent near here. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 4 
1. Shale, red . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 
Numbers 8 to 10 are the partial section of the San Angelo beds. They vary at the two ends of the mountain. 
Sections from Cedar Mountain to Robert Lee 
Section West of Cedar Mountain and East of the Mouth of Cow Creek Feet 
4. 	Shale, red, exposed in bluff 48 feet. Full thick­ness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50+ 

3. Sandstone, cross-bedded, buff, and gray, 10 to. . . . 20 
2. 	Shales, sandy, white and red. A few rods farther 
east they appear twice as thick as here . . . . . . . 15± 

1. 	Conglomerate, sandstone, and shale. Sandstone, 
which contains some quartz pebbles as large 
as quails' eggs, is buff; contains lens of white 
sandy shale at foot of hill. . . . . . . . . . . . . . . . . . . 38 

At the time this section was studied the Colorado River 
University of Texas Bulletin 
was too high to permit the tracing of the beds along its banks and as a result it is impossible to state whether the conglomerate of number 1 of the section is the upper or lower conglomerate of the Cedar Mountain section. 
Section on West Side of Cow Creek Near its Ivlouth 
Feet 
4. 	Sandstone conglomerate. No quartz pebbles. Over this is a 5-foot bed of sandstone........... . . 10 
3. 	Sandstone, soft, buff, some yellow sandy conglom­erate and some concretions, upper part quite shaly, 20 feet to.... . ....... . ..... . ......... 7 
2. Shale, sandy ferruginous, upper '2 feet leached. . . . . . 17 
1. Sandstone in ravine near the river. . . . . . . . . . . . . . . . 10 
Number 1 of this section is the same bed as Number 3 of the previous section, and varies from 0 to 10 feet in thickness. It is probably a local lens. Number 2 varies from 0 to 25 feet, allowing Number 3 and Number 1 to come into contact locally. Number 3 is locally quite thin and in other places is thicker than the figures given. Number 4 varies from 0 to 10 feet, and in many places is absent from the section. 
Section near creek above Cow Creek 
Feet Inche:; 
5. Terrace conglomerate of variable thickness. 
4. 	Sandstone, buffi.sh, cross-bedded, shale parting in lower part ................ . . .. ......... . . . 7 
3. 	Shales, maroon, to base of next sandstone. Two sheets of sandstone in the shales, upper part of shale with dark crusty sandstone sheet. Upper part of shales greenish-gray......... ...... . 25 
2. 	Sandstone, cross-bedded, stained red on outcrop, buff to brown within. Somewhat pitted. Ex­posed. . . ......•.......................... 2 6 
1. Concealed, probably containing base of Number 2.. 10 
Just east of this exposure the two sandstones come to­gether, cutting out the shale bed between them. Farther on they separate again. This is characteristic of these two 
The Geology of Coke County 
beds, as shown in the outcrop along the bluff. Between this locality and the Hester place, the following section is passed over: 
Feet Inches 
12. Shales, red, sandy, 30 feet to .... .. .... ...... .. . 28 
11. Sandstone, 10 to ..............., . .... ..... .... . 20 

10. Shale, red, 25 to ... .. ....................... . 15 

9. Sandstone and foliated gypsum .. .... . .... . .... . . 4-t­
8. Shale, red. . .... ....... ............. .......... . 8 

7. Sandstone with foliated gypsum in pieces........ . 3-t­
6. Shale, red; some light-colored streaks, ......... . 18 

Number 6 rests on top of Number 4 of the previous sec­tion. 
Section at the Hester Place 
Feet Inches 
13. 	Limestone, sandy, crystalline, with sandstone and shale, sandstone below pinching out locally. . . 5 
12. Shale, red, 2 feet to. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
11. Shale, red, from 5 feet to. . . . . . . . . . . . . . . . . . . . . . . 15 
10. Sandstone, gray, 5 feet to. . . . . . . . . . . . . . . . . . . . . . . . 7 
9. Shale, blocky, sandy, red, 2 feet to.. . . . . . . . . . . . . . . I 4 
8. 	Dolomite, sandy, pink, 2 thin layers separated by a thin sheet of shale. . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5 
7. Shale, red, blocky. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 
6. Sandstone, red, conglomeratic with whitish pebbles 6 
5. Shale, red. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4 
4. Sandstone, gray, 6 inches to............ . ...... .. 1 

3. Shale, red. ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 
2. Sandstone, fine-grained, 6 inches to 2 feet. . . . . . . . 1 3 
1. Shale, blocky, red, sandy, about....... . ......... 3 

Traced westward from Bronte these formations vary somewhat at different places, the sandstones and dolomites showing a tendency to pinch out locally, but by carrying a section of considerable thickness the horizons may be fol­lowed fairly well in a general way. None of the sections of the San Angelo formation can be duplicated in detail at any place other than the one measured. 
University of Texas Bulletin 
GENERALIZED SECTION ON THE NORTH SIDE OF THE RIVER NEAR ROBERT LEE 
A little farther west of the last section, at the road going east from the Halbert Place, the green material below the dolomite becomes sandy and a dolomite sets in at its base. Still farther west the sandstone is less than a foot thick and practically pinches out. Four feet above it is a 2-inch dolomite layer, 15 inches of red shale and nearly black shale, and another thinner dolomite. Over this is a thin sheet of calcareous material and more dark red shale. Up the hol­low from this place the following section was taken : 
Feet Inches 
5. Sandstone, cross-bedded, gray, oil showing in places.  
A lens from 6 inches to......................  20+  
4. Shales,  gypsiferous,  sandy  and  clayey,  scarlet  to  
vermilion, yellow, and red in upper 3 feet ana  
at the base, 6 feet to . . . . . . . . . . . . . . . . . . . . . . . .  8  
3. Dolomite,  two  layers,  2  to  6  inches  apart,  gray  
shale  parting  wit"!!  gypsum  crystals.  (These  
are the beds crossing the road east of the Pecan  
Mott.)  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10  
2. Shales, gypsiferous, sandy, variegated. . . . . . . . . . . .  3  
1. Sandstone,  even-bedded,  oil-impregnated  . . . . . . . . .  3  3  

Section of bluff facing Mountain Creek below road crossing at Pecan Mott Farm 
Feet Inches 
10. Recent conglomerate. 
9. Sandstone like those below, 8 feet to. . . . . . . . . . . . . . O 
8. 	Shale, red, 5 feet, and beds of sandstone 6 and 1h to 8 feet... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 
7. Dolomite, two layers, separated by thin shale.... 1 6 
6. Shale, lavender and other colors, 2 feet to. . . . . . . . 3 
5. Sandstone, brownish to snuff-colored. . . . . . . . . . . . 2± 
4. Shale, red, 5 feet to. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 
3. 	Dolomite, two beds a foot apart separated by lav­ender shale. Lower bed twice as thick as the upper bed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 
2. Shale, red. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 
1. Sandstone, oil-bearing, very dark grayish-brown.. 2 
The Geology of Coke County 27 
At the large dam on the Halbert place (Pecan Mott farm) sandstone Number 5 of this section is exposed. It thickens and thins considerably in short distances. The dolomite, Number 3 of the section, is below the sandstone at the WP.st end of the dam. The heav~er dolomite above the dam is Number 7 of the section. The lower of these two dolomites is only two feet above the sandstone. From this point up­ward, the lake section is as follows : 
Feet Inches 
7. Sandstone and crystalline calcareous material. ... 7 
6. Shale, red, green, sandy bed 6 feet below the top 20 
5. Shale, green, sandy .................. ..... ..... . 1 

4. ·Shale, red. . ................................... . 5 6 

3. Dolomite, double bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 
2. Shale, red. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 
1. Dolomite, two thin beds and some underlying shale 5 
Thirty feet above the dolomite, Number 7 of the section 
preceding the one above, is ~ 6-inch dolomite, and another is 
found three feet above that. The sandstone, Number 5 
of the same section, is two feet to 10 feet thick. Thirty­
five feet above Number 1 of the same section is a. 2-foot bed 
of soft sandstone. Twelve feet above this sandstone is an­
other dolomite four to five inches thick, followed by eight 
feet of shale to the base of a 20-foot sandstone, with a sheet 
of crystalline calcareous material on top, which, in places, 
is rather thick. Some of the lower beds are conglomeratic. 
The upper bed of sandstone is persistent and may be the 
one which passes under the divide to the west and appears 
on the east side of Mountain Creek north of the Bronte 
road. 
The sandstone which forms the top of the hills at the 
lake (above Number 7 of the lake section) is lenticular. 
It is quite thick at the "Bridges Well" exposure on Mountain 
Creek. It is well exposed beneath the bridge over Moun­
tain Creek on the·Bronte Road. 
The preceding sections are believed to cover the whole 
thickness of the San Angelo beds as exposed from Cedar 
Mountain to their top near Robert Lee. They are taken 
University of Texas Bulletin 
along the north side of the river and are so selected as to show as nearly as possible the most typical section of the formation. 
Most of the San Angelo beds are wedges rather than lenses. The conglomerates and sandstones grow thinner and finer toward the west and appear to split up in that direction. The result is that the shales and thin dolomites wedge out toward the east and irregularly dovetail into the coarser beds. 
In the western part of this region there are long crooked channels, of varying width and thickness, filled with cross­bedded sandstones. Some of these are hardly 40 feet across and some are quite large. One of these channels extends nearly west and is rather crooked where erosion gullies and valleys have revealed it. Such beds appear as sections of lenses of sandstone in the faces of the bluffs which cut across them. The sandstone filling these channels is al­ways buff or yellowish-brown, as are the more massive sandstones of this whole formation. They may be thought of as fossil creeks, or delta channels. 
Rarely can a section in the San Angelo formation be du­plicated a short distance away, but when all the details are worked out it is r'eadily seen that the sandstone and shale beds follow certain horizons quite closely thereby aiding in the construction of a section up the river. 
The shales appear to set in as wedges with points to the eastward or southeastward, and thicken to the westward and northwestward. They thicken faster than the sand­stones and conglomerates thin out, and in this way increase the thickness of the whole formation. It would seem that this is a delta with its crooked channels filled with sand­stones, some of which are in regular cross-bed strata. The gravel becomes smaller westward and northward until but relatively few very thin sheets of conglomerate occur near Robert Lee, and none of much consequence seems to have been encountered by the drill in either the Locke or Stroud wells. The whole San Angelo formation in these wells seems to have been 400 feet in thickness. 
The Geology of Coke County 
The whole section may not be exposed at Mount Mar­garet, but it probably does not exceed 200 feet at that place, although in the region of the northern part of the Kickapoo Mountains it is thicker. 
It seems likely that well records farther west will show this formation to contain more and more limestone, gyp­
. sum, and dolomite, less and less sand, with decreasing amounts of shale as these deposits merge with the calca­reous deposits of the central part of the basin in West Texas. This formation crosses the Texas and Pacific Railroad to the northward and in all probability forms the base of the Double Mountain formation as described by Cummins. It can possibly be traced to the Red River. To the south and southwest it is buried beneath the rocks of the Ed­wards Plateau. 
Eskota or Greer Beds 
On top of the San Angelo beds is a series of soft, evenly bedded, clayey, fine-grained sandstones and fine sandy shales provisionally referred the Greer stage: As a rule the sandstones and shales are dark red. Locally they are lea~hed to a buffish or greenish shade, and there. are oc­casionally persistent light-colored beds. In this formation are many heavy gypsum beds. Throughout its extent in Coke County only one thin sheet of limestone has been seen, and that is of very peculiar crystalline texture which lo­cally is found to be very sandy. It is correlated by Wrather with the dolomite in the Eskota gypsum. Along the Colo­rado River the Greer formatiop~, on account of its even bedding and finer composition, is sharply separated from the San Angelo formation, ,though it is probably conform­able with it. The shales are of darker color and carry very fine sand, and the sandstones are even-bedded and per­sistent for red-beds strata. They occur at Mt. Margaret and Kickapoo Mountains and continue up the Colorado River to the west line of the county. 
30 University of Texas Bulletin 
Section at "Hill Number l" 
Feet Inches 
9. Interval with some red sandy shales......... . . · .. . 12 

8. Sandstone, laminated, light red-brown.....· . ..... . 2 6 
7. Interval, sandstone near top ... . .... . ............ . 4 

6. Sandstone, blocky. . . ....... . . . :. . . ...... .. ..... . 1 

5. Shales, red. . . ............ . ............ . ........ . 8 

4. Sandstone conglomerate, quartz pebbles, mostly fine 5 
3. Sandstone and shales, ferruginous ........ .. .. . .. . 47 

2. Sandstone. . ............................... . ... . 7 

1. 	Interval in which occurs sandstone, sandy shale, and some irony material •....................... 18 
Number 8 has the same appearance as the first even­bedded sandstone· above the top of the San Angelo forma­tion elsewhere, and is in all probability the same bed. 
Section near first house on Sterling City auto road, after leaving the pike Feet Inches 
9. Limestone conglomerate, Tertiary or Recent. 
8. Shales, sandy, red . . ....... . ................. . . . 6 

7. 	Sandstone, dark brick red, massive to laminated, very evenly bedded throughout ......... . . .. ..·.. . . 9 
6. Shale, red, sandy, green band at top... .......... . 11 

5. 	Sandh'tone, laminated, dark brick red, a little shaly red sandstone on top ........................ . 22 
4. Sandstone, blocky, red, irresistant............... . 3 

3. Shales, sandy, green and red.................... . 2 

2. Sandstone, platy, red, green streaks at base..... . 1 
1. Shale, red, blocky, somewhat sandy...... .... : ... . 2 
This section appears to be above the San Angelo beds. 
LOWER WILDCAT CREEK 
The basal part of this section is nearly as low as the beds in Hill No. 1 or near the base of the Greer formation. 
Feet Inches 
19. Shaly, sandy, material, dark red. .... .. ......... . 15 

18. Sandstone, greenish-white ... ........ ... .... . .. . 10 

17. Sandstone and shaly dark chocolate beds, 8 to ..... . 10 
The Geology of Coke County 
16. 	Sandstones and shaly streaks, green, hard white layer 2 feet below top changes to laminated bed here . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 
15. Sandstone, hard, red-chocolate.................. . . 1 8 

14. 	Sandstone, massive, chocolate, shale at base, green blotches ................................... . 4 6 
13. 	Sandstone, two beds, shale parting, chocolate-colored with green blotches, upper bed massive and thicker than the lower bed .......... . ....... . 6 
12. Sandstone, soft, green, firmer than No. 11....... . 0 6 

11. Sandy bed, mottled, shaly........... ..... ....... . 4 6 

10. Sandstone, hard, red ........................... . 

9. 	Sandstone, laminated, red and greenish (all stained red on outside) ............................ . 1 6 
8. Shale, red, blocky, in part laminated, sandy...... . 2 6 
7. Sandstone, green ........... . .. .. . . . . . . .. . .... . 6 

6. Shale, sandy, and shaly sandstone.............. . . 9 

5. Sandstone, hard bed, shaly, red, 8-inch hard bed.. 3 3 
4. Sandstone, green .. • . ........... . ............... . 9 

3. Sandstone, soft, mali!sive, red, green specks....... . 4 

2. Sandy layer, green, 6 inches to................. . 1 

1. Shale, blocky, red . . .. . . . . .... .... . ... ..•.. ...... 6 
Section on Wild Cat Creek 
Above Bridge on Sterling City Road 

32. Sandstone, salmon-colored . . . . . . . . . . . . . . . . . . . . . . 2 6 
31. Sandstone, firmer than the one below. . . . . . . . . . . . . 15 
30. Shaly material, soft, dark red.... . ......... .. ... 20 

29. Sandstone, soft, laminated, brick-red. ... . . . . . . . . . . 16 
28. Interval, mostly red shale.. .. .. .. .. . .. .. .. .. . .. . 20 
27. Sandstone, evenly-bedded, soft, salmon-colored. . ... 8 
26. Shaly sands, red ..... '" . . . . . . . . . . . . . . . . . . . . . . . . . 4 
25. Sandstone, massive, red. . . . . . . . . . . . . • . . . . . . . . . . . 2 6 
24. Shale, sandy and shaly sandstone, dull red to green 3 
23. Sandstone, rather soft, evenly-bedded, dark brick-red 9 6 
22. Shale, sandy, red, 2 feet to. . . . . . . . . . . . . . . . . . . . . 3 
21. Gypsum, pink, in nodules and crystals. . . . . . . . . . . . . O 1 
20. Sandstone, laminated, green and salmon-colored. . . 7 
Section of Colorado River Bed 
Below the Wagon bridge West of Robert Lee 

Feet Inches 
7. Sandstone, green, shaly, top not seen........ . . . . . 2-. 

6. Shaly, red, green on top ........................ . 3 

5. Sandstone . .......... . ............ . . . ......... . 0 3 

4. Shale and thin sheets of sandstone.... . .. ... .... . 8 
University of Texas Bulletin 
3. Shales, red, containing gypsum.  14 inches to ... ..  4+  
2. Sandstone, shaly, gypsiferous, 4 inch denser, sand­ 
stone  at base  .. . .......... . ........ . .. . ... .  2  4  
1. Shale, red, many sheets of satinspar, blocky shale  8  6  

Section of the Seaton Keiths Bluff, Three Miles West of Robert Lee 
Feet Inches 
18. Conglomerate, Tertiary or Pleistocene. .. . .. . .... . 40 
17. 	Sandstone, evenly-bedded, friable, massive, red, some greenish specks and masses near the bottom and at the top . . ....... ......... . ........... . 15 
16. 	Earthy beds, blocky, clayey, and sandy material with few signs of stratification........... . .. . 20 
15. 	Sandstone, reddish, polka-dotted, friable, very ir­regularly bedded, 3 feet to ....... . .... .. ... . . 2 
14. Sandstone, soft, blocky, green, friable . . ... . ..... . 6 
13. Sandstone, very friabl.e, blocky, dark red ..... . . . . 9 
12. 	Sandstone, greenish gray, stained red on outside, 7 feet to ........... . ...... . .... . . ... . . .. . . . 6 
11. Shale, sandy, blocky, red, or impure sandstone . .. . . 9 
10. 	Sandstone, two or three beds, firmer than beds be­low, greenish, stained red, shaly locally..... . . 6 
9. 	Shales, sandy and soft sandstone. The top of this bed ana the base of the one above form a dom­inant line along the west cliffs, 20 feet to.. . .. 16 
8. 	Sandstone, two beds, slightly gypsiferous (three beds in west part of bluff), forms light red­brown double band along bluff, with greenish beds below it ............................... . 8 
7. Shaly material, mineralized, greenish ............ . 2 

6. Shales, somewhat lenticular, contain some gypsum 8 
5. 	Sandstone, laminated, red, thickening from a few inches to .... . ...... . .......... . .. . . .. ... . . 3 
4. Shale, red, some gypsum, contains some sandstone 8 
3. Sandstone, shaly, friable, red, much gypsum. . . . . . 2 . 
2. Sandstone, laminated, red, some gypsum . . . . . . . . . . 1 8 
1. 	Gypsum, massive, wfth masses of crystalline gyp­sum scattered through it. .The upper 5 feet contain some shale. Base shaly, with satinspar 12+ 
The basal part of this section may duplicate the base of the previous section, which is probably near the gypsum horizon above Wildcat Creek bridge. 
The Geology of Coke County 
Section of Bluff on East Side of Second Creek 
East of John Saul's place. 

Feet Inches 
5. Sandstone, red-brown ......................... . 20 

4. Sandstone, shaly, pale red ...... ... ..... ... ..... . 15 
3. Sandstone, gray .............................. . 7 

2. Sandstone, soft, red ........ ...... .... ... .. ... .. . 

1. 	Sandstone in creek (below recent conglomerate) 
cemented with gypsum and containing gypsum 
masses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5± 

Rough Creek Section, near Meneille House 
14. Sandstone, massive, light red. . . . . . . . . . . . . . . . . . . . 5 
13. Sandstone, soft, gray, and shale............... . . 1 

12. Sandstone, massive, quite friable, red............ 48 

11. 	Sandstone, greenish-gray, prominent, apparently same green bed seen in Seaton Keiths Bluff (Number 12 of that section)................. 7 
10. Sandstone, massive, reddish. . . . . . . . . . . . . . . . . . . . . 3 
9. Shale, red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 
8. 	Sandstone, massive to shaly, parti-colored, quite 
gypsiferous, masses of gypsum in upper part.. 7 

7. Shale, very gypsiferous................ . . ....... 2 6 

6. Sandstone, salmon-colored very gypsiferous. . . . . 7 
5. Shale, red and gray, small masses of gypsum. . . . . . 4 6 
4. Sandstone, parti-colored, gypsiferous . . . . . . . . . . . . . 4 
3. Gypsum, sandy, or gypsiferous sandstone......... 5 

2. Sandstone, red and green, shaly, sheets of gypsum 5 
1. Sandstone with gypsum streaks. . . . . . . . . . . . . . . . . . 20 
South Pecan Creek Section, Bluff Above· Graveyard 
10. Limestone conglomerate, Pleistocene? 
9. 	Sandstone, rather evenly-bedded, red, joints and 
cracks filled with calcareous material from con­
glomerate above . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

8. 	Sandstone, evenly-bedded, nodular, gray to deep 
red. Some small gypsum crystals. . . . . . . . . . . . 6 

7. 	Sandstone, massive, evenly-bedded, harder than that below, salmon-colored . . . . . . . . . . . . . . . . . . . . . . . 5 6 
6. Sandstone, darker and more friable than number 5 3 
5. 
Sandstone, relatively hard, massive, gray to salmon 3 

6. 
Sandstone, salmon-colored very gypsiferous .... , . 'l 


3. 	Sandstone, massive, soft, weathers into large 
rounded nodules . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

2. Sandstone, massive, soft................ . ... ..... 12 

1. Concealed from creek bed . . . . . . . . . . . . . . . . . . . . . . . . 12 
University of Texas Bulletin 
Farther down, the following section is shown in the creek: 
Feet Inches 
3. Sandstone, soft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ... 
2. 	Shale, hard, purple, and thin plates of white sand­stone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 6 
l. Sandstone, poorly stratified, soft................. 18 

The purple shale is rather persistent and in places comes in over a gypsum bed which has been dissolved away in this immediate region. This accounts for the peculiar slumped-faulted appearance of the section. 
A little farther down South Pecan Creek the following section is exposed : 
Feet Inches 
4. 	Packsand, as in previous section, residual from dis­solved gypsum beds, 4 feet to. . . . . . . . . . . . . . . . 10 

3. Sandstone, red and gray, slump at top, 2 feet to.. 3 
2. Shale, sandy, and shaly sandstone... ... .. . .. . . .. . 4 
l. Sandstone, massive, quite friable, red. . . . . . . . . . . . . 7 6 
Number 1 of this section is 10 feet thick with two feet of yellow or red shale beneath it, as shown by other nearby exposures. Beneath it are seven feet of quite petroliferous sandstone. 
Section of the Rocks of the Bluff on South Pecan Creek, Just Above the Junction of North and South Pecan Creeks 
Feet Inches 
10. Sandstone, thinner-bedded than number 9... . .. .. . 25± 
9. 	Sandstone, amorphous residual material from dis~ 
solved gypsum layers, 10 to 20 feet . .......... . 15± 

8. 	Shale, with sheet of ripple-marked sandstone, 2 feet to 6 inches .................... , .......... . 1 6 
7. Sandstone, even bed ... .... ... .. . . .. ..... . ... . . . . 3 6 
6. Shale, red ..................... ..... .......... . 2 8 

5. 	Sandstone, massive, red, cross-bedded, green at south end of bluff. . ....... . . .. . ....... ... . . . 5 6 
4. Shale, sandy, thin sandstone in the middle. . ..... . 4 6 
3. 	Sandstone, green or gray, at south end of bluff, red near the north end .................... . . 6 6 
2. Shale, yellow or gray.... ...................... . 2± 

1 	Sandstone, yellow and gray, 5 feet showing above 
creek bed ............ ...... ........ ....... . 5± 

The Geology of Coke County 
The thickness of the two upper beds is estimated. Beds 9 and 10 are crumpled due to the solution of gypsum from the rocks of Number 9. The latter bed is thinned cor respondingly. 
Section of the Rocks and Conditions from Mouth of 
Pecan Creek to Base of Last Section 

Feet Inches 
16. Sandstone, gray ... . ... . .. . .............. .... . . . 10 0 

15. Shale, red ...... ....... . .. . . .... ..... ......... . 1 0 

14. Sandstone, gray to red ....... ....... ........... . 1 8 

13. Red shale .................................... . 1 8 

12. Sandstone with shale and nodular sandstone in  
lower part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7  5  
11. Sandstone, massive, salmon-colored.. ... ...... ... .  4  0  
10. Shale, and sandstone containing boulders. . . . . . . . .  3  0  
9. Interval, 5 to 15 feet . . .. .... ... ..... .......... ..  10±  
8. Sandstone and .shale; 25 feet" of new beds; 15 feet  
of shale at east end reduced to 5 or 6 feet....  25  
7. Sandstone, massive to shaly, somewhat mottled  
mostly dark red. Rests on Number 6, just  
above Arlitt ranch-house. Lighter-colored  
blocky bed at top may be white-washed from  
caliche . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  45  0  
6. Sandstone, three beds, massive to cross-bedded,  
light-colored and red, about.... ............ . .  20  0  
5. Sandstone, red to mottled, massive, with 6 inches to  
1 foot of mottled shale at the top..... , . . . . . .  4  6  
4. Next section half mile upstream, right bank, unex­ 
posed interval between sections, 5 feet to.. . . . . .  15  
3. Sandstone, massive, cross-bedded, gray, some sal­ 
mon-colored masses, resistant, has general ap­ 
pearance of gray layer on opposite side of river  4  0  
2. Sandstone, massive, shaly at base, red, some gray  
spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6  0  
1. Sandstone, massive to knotty, red and mottled, two  
beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5  0  

Section of Bluff on south side of creek at bend 
Feet Inches 
8. Shale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
7. Sandstone, massive bed below. . . . . . . . . . . . . . . . . . . . 7± 
6. Shale..... ....... . ..... . ... ... .. ~.............. 2± 

5. Sandstone. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5­
University of Texas Bulletin 
4.  Shale..  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1­ 
3.  Sandstone.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  25+  
2. 1.  Shale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sandstone in creek bed .. .. . . . . . . . . . . . .. .. .. .. .. .  12+  

Number 3 of this section is probably Number 16 <if the previous section and is the base of the next bluff on the west side of the creek. 
The beds of lower Pecan Creek are nearly the same hori zon as some of the upper beds in Seaton Keiths Bluff sec­tion. There is a persistent greenish-gray bed traceable along the north bluffs of the river from Seaton Keiths Bluff to Rough Creek, nearly opposite the mouth of Pecan Creek, and this may be represented by Number 3 of the section at the mouth of Pecan Creek. The massive. sandstones of the bluff below forms the base of the following section on the Parsons place. 
Feet Inches 
19. Sandstone. . ............ ................... .. . 2 

18. Shale. . ................................ ...... . 2 6 

17. Sandstone, massive red or greenish ........ ... . . . 8 

16. Shale, red, sandy .......................••..... 4 

15. Sandstone, massive, red, green locally . ... .... . .. . 6 
14. Shale. . .............. .. ................ . .... . 3 

13. Sandstone, massive yellowish gray bed ....... .... . 4 

12. Sandstone, 4 or 5 thin beds ..................... . 6 6 

11. Sandstone, massive. . ............... .. . .. . . . . . 14± 

10. Shaly gypsum .... .. . . ... . .................... . 3 

9. Sandstone (equals No. 3 of previous section) ... . 4 6 
This section is numbered continuously with the second one above. 
Section on river at mouth of Gulch, N 28° E from Millikan Mountain Feet Inches 
18. 	Sandstone, red, knotty, green and gray, locally shaly, all very irregular. . . . . . . . . . . . . . . . . . . . . . . . . . 20 
17. Shale, yellowish and soft sands. Across canyon this bed is red and apparently gypsiferous........ 20 
16. 	Sandstone, red, and red ~hale, all very uneven; platy conglomerate of sandstone and other material 4+ 
The Geology of Coke County 
15. Sandstone, dark red, top very uneven.... .... ... . 4 6 
14. Shale, sandy. . . ........... . ................ .. . . 5 

13. Sandstone, massive, red. . .................... . 4 6 

12. Shale, red, fine sand............................ . 6 

11. Sandstone, green below, red above ............... . 12 

10. Shale, soft, sandy and red sandstone........... . 7 

9. Sandstone, soft yellowish, "gyppy?" ......... . . . 5 

8. Shale, yellowish-gray, sandy, gypsum? ........... . 10 

7. Sandstone, soft, red ................ . .... . .. .... . 3 

6. "Gyppy" material, red-gray ................... . 6± 
-5. Sand, soft, gray, gypsum ........ . .... .. . ... ... . 10 

4. Shale. soft, red and greenish sandstone, shale below 5 
3. Sandstone, rather' shaly, greenish-gray..... ...... . 4 ·2. Sandstone, massive, greenish-gray.............. . 20 
1. Shales, green, red, and gray, grading into sandstone 3 
Much gypsum has been dissolved from beds of this sec­tion, especially beds Nos. 6 to 10, and probably beds Nos. 16 to 18. It existed as beds of gypsum, or gypsum in small masses, while some of it formed the cementing material of the rock. 
In order to bring out the changing aspect of the beds from place to place-even though the beds are much better :stratified and more persistent than those of the San Angelo beds-the part of the section from Number 5 of this river section to its top is repeated in fresh exposures at the head ·of the canyon. 
Feet Inches ·33_ Limestone, siliceous ..... ... ... . ...... . ........ . 2 0 
32. Shale, mottled (probably top of river section, 6-10 
feet) only 5 feet visible.................... . 5 0 
:31. Sandstone, red ...... .. . . ...................... . 4 4 

30. Shale, red, or shaly sandstone................... . 23 

·29.  Crusty material,  calcareous  appearance.  Horrzon  
of  platy conglomerate;  equals  number  16  of  
river section  . .. ..... ... .. . ......... ....... .  5  0  
28. Sandstone, red  .................... .. ........ .. .  11  0  
· 27.  Shale, red  .................................... .  5  
26. Sandstone, soft, earthy, red; basal part of this bed  
is main uppe~ firm bed of the river section ... .  20  
··25.  Shale........................................ .  5  
: 24.  Sandstone, largely soft..... .. ............ ...... .  10  

University of Texas Bulletin 
23. Sandstone, very irregularly bedded; equals  No.  7  
of  river  section. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7  
22. Shales, purple, sandstone above and below. . . . . . . .  0  6  
21. Sandstone, earthy, and soft material  (gypsum dis­ 
solved  out)  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10  
20.  Sandstone  red,  and  calcareous  material  (gypsum  
dissolved out)  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8  
19. Gypsum, massive; equals No. 5 of river section....  7  

Beds Nos. 19-24 of ravine section and Nos. 5-9 of the river section represent Nos. 9 and 10 of the Pecan Bluff section. In the last mentioned locality, solution of the gyp­sum from between the sandstone and shaly layers has pro­duced the peculiar wavy appearance of the face of the bluff. The purple shale well up in this formation, seen above the bluff of South Pecan Creek associated with sandstone, com­prises Number 22 of the ravine section. 
Number 33 of the section is of very peculiar appearance and often has a crystalline cellular structure, sometimes sandy, and is very persistent from the high bluffs of upper Pecan Creek region to the west side of Wilson Mountain where it dips into the river. It is the only calcareous bed so. far seen in the upper part of the Double Mountain beds of Coke County. For this reason it is particularly valuable as a base on which to work out structure in this region. 
Section 	Southwest Side of Wilson Mountain 
Feet Inches 
4. 	Shales, red, some shaly sandstone and probably some gypsum lenses or beds . .-. . . . . . . . . . . . . . . . 78 
3. 	Gypsum, massive, interstratified with larger and smaller amounts of shale and sandstone. . . . . . . 78 
2. Pseudo limestone or dolomite............. .. ..... 2 

1. 	Shales, red, filled with intersecting thick sheets of satinspar, lenses of gypsum 1 to 2 feet thick at top on side mountain. . . . . . . . . . . . . . . . . . . . . 34 
Farther northwest, heavy gypsums occur immediately be­low the dolomite as well as above it. Farther westa greater thickness of similar beds comes in below the base of the overlying formations. 
The Geology of Coke County 
Quartermaster Formation ( ?) 
In the northwest corner of Coke County ~ccur some de­posits of uncertain age. They are composed of coarse quartz, 
" quartzite, and chert conglomerates, in a brownish sandy matrix associated with very dark maroon shales and im­pure sandstones. Locally these conglomerates and even the maroon sands are nearly black. Rocks of Comanchean age rest upon them. At the present writing it is impossible to state whether they are of Triassic (Dockum) age, or whether they are a formation similar to the San Angelo, occurring well up in the Double Mountain beds. If the last is the case, as seems probable, then they may represent an uncon­formity between the Greer and Quartermaster beds. These beds are best developed in the Panther Gap-Stepp Mountain region. 
On the south side of the river, southwest of Wilson Moun­tain, similar beds appear, which are covered by the old river conglomerate. Because the slopes of the scarps below the soft basal Comanchean are covered with its debris, it is difficult to find a clear contact at the exposures visited. Until this section is carried farther up the Colorado River, and its position accurately determined, it is better to leave further discussion of the age of these beds in abeyance. One of the best sections seen is at Panther Gap. 
Panther Gap Section 
15. Limestone, nodular, more above it. ...............  5±  
14. Concealed  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  15  
13. Limestone,  nodular  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7  
12. Marl, yellow,  filled  with  fossils,  Exogyra  texana,  
gastropods, etc.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4  
11. Limestone,  dark  buff,  a  fossil  conglomerate,  
Exogyra and Gryphea  . . . . . . . . . . . . . . . . . . . . . .  2  
10. Sandstone and sand.  Gray to dark buff. . . . . . . . . . .  12  
9. Conglomerate,  coarse,  white,  quartz,  etc.  in  it.  
Sand  just below  it.  Comanchean............  4  
8.  Concealed  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  25  
7. Sandstone, pink and buff, like Trinity but firmer.. .  25±  
6. Conglomerate, sandy, firm. . . . . . . . . . . . . . . . . . . . . . .  10  

40 University of Texas Bulletin 
5. Shaly material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5+ 
4. Sandstone, light brownish, 5 feet to ....... , • • . . . . 10 

3. Conglomerate resembling that at Mt. Margaret. . .. 21i 
2. Sandstone, yellow, purplish, and green. . . . . . . . . . . . 20 
1. Shales, gray-green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
· Numbers 9 to 15 are certainly of Comanchean age, while Nos. 1 to 6 appear to be older. No fossils have been col­lected from these lower beds. The conglomerate, Number 3, is made up of several components. 
Beds Nos. 1 to 6, inclusive, are quite different from the usual exposures of the Comanchean sands of Runnels and Coke counties. There is a locality near Nipple Peak south of Bronte which contains somewhat similar gravel but this 
. is apparently reworked and forms the base of the Coman­chean beds. · The conglomerate in beds Nos. 1 to 6 is composed of larger and smaller pebbles of quartz and chert. The quartz is usually thoroughly rounded and the chert less so, much of it being subangular. The matrix is sand which is some­times cemented with iron oxide. This conglomerate is on the average finer than the San Angelo conglomerate at Mount Margaret, but pebbles an inch to five inches across are to be found in thd region east of the Gap and north of the road. There are two varieties o{ quartz at Mount Margaret, white and red. The white is more common. There are fewer pebbles of quartz than of chert in the Panther Gap conglomerate, while the sand of the matrix contains much more quartz thaI.l chert. Some beautifully veined pebbles have been seen. The cherts are black, green, and gray. The green chert is quite prominent in some spots. It has the appearance of the green cherts of the Caballos formation of the Marathon region. 
The Geology of Colee County 
LOGS 
Driller's Log, Stroud No. 1 Well 
Robert Lee Oil Co. 
Located Three Miles West of Robert Lee, Texas, on Wild Cat Creek 
December 30, 1918 

Depth of feet 
below surface 
From To 
Surface . ..... .. . . ............... . .... . . ..... . . . . 0 20 
Sand rock ..................... . .. .. .. .. ... . .... . 20 46 
Gravel and red clay.............................. . 46 78 
Pack sand ... , .......... . ....................... . 78 160 
Red shale. Oil and gas showing at 175 feet ... . .... . 160 320 
Hard red shale . ............. . :....... . ..... . ..... . 320 420 
Rock ................... .. ................. . ..... . 420 422 
Red shale ... •............ ....................... . 422 454 
Soft sand rock with a little lime...... ..... ........ . 454 500 
Hard· sand and lime rock......................... . 500 560 
Red shale boulders.............................. . . 560 650 
Hard rock with lime gypsum ....... ...... ....... . . . 650 690 
Variegated shale boulders with lime................ . 690 834 
Lime rock ..... . . . ... . .... . .... .. ... . ........ . .. . 834 850 
Variegated shale .. .. . ..... . .............. . ... . .. . 850 877 
Gumbo . ....... . .... . ........ . ............. , .. .. . 877 879 
Hard sandstone . .................. . ............. . 879 ~81 
Hard variegated shale........... ........ ......... . 881 975 
Hard shale, thin strata rock........ . . . ............ . 975 1038 
Sandstone, hard ...... .... •.............. ......... 1038 1049 
Shale, thin strata hard lime rock....... ...... ..... . 1049 1182 
Blue gumbo .... ... ............. .... ........ ..... . 1182 1184 
Hard variegated shale.... ................... ..... . 1184 1202 
Gray limestone ... .. . . . .. ..... . . ... ..... . . . ...... . 1202 1356 
Blue gumbo .. . . . ...... . ...... ... ..... . . . . .... ... . 1356 1361 
Limestone ... . ...... .... .. . . . ................... . 1361 1373 
Shale .. ... ......... . . ... ..... .. ....... . ........ . 1373 1378 
Limestone ............ .......................... . 1378 1404 
Black gumbo .. . ....... .. ...... . . . ............ . .. . 1404 1407 
Limestone ............... . ....... .. . . .... . . .. . .. . 1407 1419 
Variegated shale, blue below 1502 ........ ,. . ....... . 1419 1557 
Hard limestone ........ .. .. ... ......... .. . ... . .. . 1557 1589 
Dark blue shale...... ........ .. .................. . 1589 1678 
Light colorPd limestone, fairly soft........ .. ...... . 1678 1697 
Black gumbo ..... .. . . . .. .. .. ...... . ..... . .... . . . 1697 1699 
Limestone .. . ...... .. ........ . . ... .... . .. . ... . .. . 1699 1744 

University of Texas Bulletin 
Blue shale 1744 1821 
Dark blue limestone . . ..... . ... .. ..... . .. . .. . . . .. . . 1821 2020 
Blue shale and lime .. . .. . ................. .. .. .. . . . 2020 2152 
Rock, very hard and rough drilling................ . 2152 2166 
Shale . . .................... . .......... · · · · · · · · · · 2166 2189 
Gumbo . ... .......... . .. . ... . ................ . .. . 2189 2191 
Blue shale and lime (quite a lot of lime) . ....... ... . 2191 2197 
Hard limestone ..................... . ......... . . . . 2197 2324 
Hard limestone with soft strata.............. ... .. . 2324 2411 
Hard limestone ............... .... ........ .. ·..... . 2411 2448 
Hard limestone with thin soft strata.......... ..... . 2448 2506 
Limestone with strata of soft lime shale...... ...... . 2506 2625 
Hard grayish limestone ........................ : .. . 2625 2733 
Soft limestone, very light color.................... . 2733 2785 
Hard limestone ...... ....................... .... . 2785 2825 
Soft limestone .................. : ............... . 2825 2845 
Hard limestone .... . . .. ... . . .. .. . ... . . . ......... . . 2845 2875 
Sand, salt water ... .. . . .. .. ... . ............ . .. .. . 2875 2890 
Hard limestone with many shells ... .. . . .... ..... ... . 2890 2986 
White sand, salt water, some gas ........ .......... . 2896 3004 
Limestone. hard, with pyrites ..................... . 3004 3028 
Limestone and pyrit.es: hardest drilling yet encountered 3028 3068 
Coarse sand, salt water .......................... . 3068 3078 
Hard limestone, pyrites............ ............... . 3078 3093 
Pyrites of iron. Solid strata, very hard . .. . . ...... . 3093 3108 
Sand, salt water .. . ......... . ................... . 3108 3123 
"Little lime and lots of shells''. . . . ............ .... . 3123 3131 
Limestone and lime shells ......................... . 3131 3156 
Hard limestone with pyrites of iron .... .. ........ . . . 3156 3231 
Limestone with coal. .......' .. .. . . ... ..... . ... . .. . 3231 3250 
Limestone with pyrites.... .................. ..... . 3250 3270 

Driller's Log of Westbrook No. 1 Well, at Tennyson, Coke County, Texas. Completed in December, 1919. 
Depth below surface in feet From To Red rock .... . .. .. .. . ....... . . . ................. . 0 120 Lime, hard. Water, eight hailers per hour........ .. . 120 135 Shale, brown, caving........................... .. . 135 171 Lime, gray .. . .. .. ......... . . . ... . ..... . . . ........ . 171 200 Missing ...... ....... .... . .. . ......... . .. . ... . ... . 200 290 Red rock ........... . ...................... .. ... . 290 320 Lime, gray .. . ... . ........... . ... .. . . ....... . . .. . 320 332 Red rock, lime shells ............................. . 332 410 Lime, gray hard .. ..... .... .... . . ..... . ...... .... . 410 436 
The Geology of Coke County 43 
Slate, blue, and mud .... .. ... ..... ... ... ....... .. . 436 500 
Slate, blue, and shells............. ............... . 500 540 
Lime, hard, gray ........ ...... ...... .. . : . .. ..... . 540 595 
Sand, white, soft (quartz) ........................ . 595 597 
Red rock .. . ......... . ...... . .... . .. . . .... ..... .. 597 640 
Shale, blue, soft. ... . ....... ...... ........ . .. ..... . 640 685 
Shale, brown, soft. .. .. ..... ... .... ........ .. ..... . 685 735 
Shale, blue, soft .. ..... .. .. ..... ........... . .... . 735 750 
Lime, white hard ..... .. . .... .......... ..... .. ... . 750 790 
Shale, white, soft ............................... . 790 795 
Lime, white, hard ......................... .. ... . . 795 855 
Lime, black ......... . .... . ...................... . 855 860 
Lime, white, hard ................. . .... .......... . 875 887 
Shale, blue, soft.................................. . 887 893 
Lime, white, hard................................ . 893 922 
Shale, soft, white................................ . 922 933 
Lime, white and gray............................ . 933 1022 
Shale, white . .... . .......... ... . .... ..... .. ..... . 1022 1032 
Slate, limy ....... .. . .... .. ....... .......... .. .. . 1032 1075 
Lime, hard, white................................ . 1075 1095 
Shale and shells, white........................... . 1095 1115 
Slate, dark ................ . ..... ...... ......... . 1115 . 1125 
Lime, dark, broken, sulphur water at 1195......... . 1125 1205 
Shale, white ............ ......... ....... . . ... ... . 1205 1220 
Lime, dark .......................... .. .......... . 1220 1320 
Shale and lime, dark............................. . 1320 1384 
Lime, gray ........ : .............. . ... ... . ....... . 1384 1470 
Shale, light . ....... ...... ........ ... .. ... ....... . 1470 1485 
Lime, dark blue with shale breaks.. . .. ..... ....... . 1485 1632 
Shale, brown ............. . .......... . ..... . . .. .. . 1632 1638 
Lime and shale, gray, gas sand, sulphur water at 1850, 
water up to 250 feet from collar....... : ....... . 1638 1850 
Lime, gray ........... . ........... .. ..... ... .... . 1850 1970 
Lime, dark, water, 4 hailers............... . 1970 1985 
Lime, water, hole full ....... . . ... ................ . 1985 2025 
Lime, break at 2145 feet. Parafin scum ... . .. ... ... . 2025 2145 
Lime, gray . ... ................ .. ... ... ....... .. . 2145 2330 
Lime .................... · ........ · .. · · ·· · ·· · · · · · 2330 2375 
Lime, sandy, 2 hailers water .... .. ... ... . ... ... ... . 2375 2385 
Lime . ........... ....... ..... ..... . .. ... · ... · · · · · 2385 2420 
Shale, broken, and lime shells. ............. ....... . 2420 2438 
Lime ... ..................... · · · · · · · · · · · · · · · · · · · · 

2438 2450 
Shale, blue .................... . ................. . 2450 2460 
Shell .... . .. . . ..... . ..... .. .. ........ .. .. .... .... . 2460 2465 
Shale, blue, caving....... .................... .... . 2465 2500 
Lime, gray, sandy................................ . 2500 2510 
Shale and brown shell........................... . ·. 2510 2570 

University of Texas Bulletin 
·Brown shale, light.................... ........... . 2570 2600 
Hard shell ..............•.... . ....... ... ......... 2600 2602 
Lime, broken, and shale.. ......................• . . 2602 2610 
Lime, hard ............................... . ... .. . 2610 2620 
Shale, blue •....... . ... . .................. . .... . . 2620 2622 
2622 2625

Lime .............. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 
Shale, white ...........•................. . ........ 2625 2628 
Shell ............................... . ........... . 2628 2630 
Shale, white, caving................. ............. . 2630 2645 
Shell, sandy . . ..... . . . .......................... . 2645 2650 
Red rock ................ . ........... . ..... . ... . . 2650 2652 
Shale, blue ........ . ........... . .......... . ..... . 2652 2660 
Lime .... . ....... . ........ . ................ . .... . 2660 2680 
Shale, blue . . .. . . . ...... .. ...... . ................ . 2680 2683 
Lime ....... ............................. ....... . 2683 2695 
Lime, broken .. .......... . ....... . .. . . . ... . ..... . . 2695 2705 
Shale, blue .......................... . .... . ...... . 2705 2710 
Shale, white . . . . . . . ... .. . .... . .. . ....... . ......... 2710 2715 
Lime, hard, black.... .... ...................... . . . 2715 2720 
Lime, gray ................. .. .............. . ... . 2720 2730 
Lime, white .......................... . .. . ...... . 2730 274-5 
Shale, blue .. . ....... . .. . ..... . ..... . ... .. ..... . 2745 28UU 
Slate, blue, and shells................ ............ . 2800 2815 
Lime and slate................................... . 2815 2850 
Shale, blue ............ . . . ...................... . 2850 2860 
Lime and shells .................................. . 2860 2930 
Shale, black, blue, caving. At 2930 feet a small coal 
seam ........ .. ...... . ...................... . 2930 2950 
Slate, white and blue, and shells................... . 2950 3005 

Log of the Cain Well, No. 1, San Angelo, Texas. By H. H. Jones, Superintendent. Elevation 1890 Feet 
Thickness Depth Red sandstone and chert. . . . . . . . . . . . . . . . . . . . . . . . . . O 8 Boulders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 13 Hard sandstone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 25 Red clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 45 Boulders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 50 ·Red clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 95 Blue shale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 
111 Limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 120 Sandstone, water, salt. ......... .. .. .. ... . . . ....... 3 123 Limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 129 Sandstone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 
183 ·Red clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 189 Limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
194 
The Geology of Coke County 45 
Sandstone, pyrites, mica.......................... . 11 205 
Flinty rock ....... . ......................~ ...... . 4 209 
Hard sand rock...................... ............ . 3 212 
Blue shale ...................................... . 59 271 
Hard shell ................... . .................. . 1 272 
Blue shale 33 305 
Hard limestone ..................... .. . . ........ . 31 336 
Hard sandstone ...... , . .................'. . ... . .. . 5 341 
Water sand, salt, sulphur..... ............. ....... . 5 346 
Hard shell . ........................... ..... .. ... . 1 347 
Gray shale .......... ..................... .. ... .. . 25 372 
Hard lime .................... . ..... .. ...... .. .. . 8 380 
Blue clay .................. . .................... . 12 382 
Sandstone . . . .. ..... . . . ....... . .... .. ....... .... . 8 400 
Limestone ................ ................. . ... . . 12 412 
Sandstone ................. .. ................. .. . 8 420 
Hard sandstone, pyrites. . . . . . . . . . . . . ..... . ...... . 22 442 
Blue clay . ..... . ............ ..................... 5 447 
Very hard lime . . ... . ......... . . . ..... . . .. .. .. ... . 23 470 
Limestone, pyrites .... . .................. . ........ . 7 477 
Blue clay ................................. .. .... . 2 479 
White gypsum .......................... . . .. .... . 3 482 
Blue clay ........... . ........... .......... . ..... . 4 486 
Hard gray shale...... ........................... . 2 488 
White gypsum ................. . .......... .... .. . 5 493 
Blue clay . . ................. ................ .. .. . 6 499 
Gypsum and blue clay............................ . 4 503 
Blue clay ............... . ................... . ... . 6 509 
White crystal gypsum................ ............ . 3 512 
Blue clay .. .. .. .. ............... . .. .. ...... . .. . . . 6 518 
Hard shell ............. ......... .. ... . ...... . ... . 3 521 
Blue clay and gypsum. . . . . . . . . . . . . . . . . . . . . ...... . 2 523 
Hard shell .... . .. . . . .......... , . : .. ............. . 3 526 
Blue clay ....... . . .. ............ . .. ... ... . . .. .. . . 6 532 
White gypsum .... . ....... .. ......... .. ....... .. . 4 536 
Blue clay .............................. ......... . 1 537 
White lime ......... . . . . . .......... .. ..... . . ... . . 8 545 
Blue clay ........ . ....... .. . .. ... . . . ..... . ... . .. . 55 600 
Hard gray lime............. .. : ... . . . ............ . 10 610 
Gray lime ................ . ....... . ............. . 20 630 
Blue gumbo ...................... ............... . 5 635 
Hard gray lime............................. ..... . 35 670 
Blue clay and shale............................... . 180 850 
Light blue sandy shale.. . ........ . .... . ... . . . .... . 7 857 
Blue gumbo .............. .. ..... . . . . . ......... .. . 11 868 
Lihgt blue shale. ................................. . 56 924 
Black shale ... . ..... . . . ........ .. ....... . ... . . .. . 4 928 

University of Texas Bulletin 
Blue shale ....... .. . . . . ................ . ..... . . . . 
Blue gumbo, satinspar............ ............... . 
Blue gumbo ... ... . ...... . ..... . ............ .. . . . 
Hard shell lime .... .. .. .. . ....... .... . .... . ...... . 
Shales, light blue, dark blue to very dark .. .. . . . .. .. . 
Black limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 
Light blue shale ......._. ... . ..... . .......... . .... . 
Blue gumbo, bituminous.......... ....... ........... . 
Gray lime . ...... . .. .. . ........ .. . ..... ... ... . . . . 
Shale, light sandy............ .................. .. . 
Gray lime . .. . .. .... .. . .. . .......... . ...... . .. .. . . 
Blue gumbo ... . . . .. ... . ..... . ... . ... ..... . ... ... . 
Light blue sandy shale........................... . 
Gray lime . ............... . ............. .. .. .. .. . . 
Blue gumbo ............ . ......... . ... . .... .. .. . . . 
Gray lime ............ . ...... . ........ . ......... . 
Dark blue shale............................ .... . . . 
Gray lime ...... . ....... ... .. . ... . ........ . .. . .. . 
Blue shale . . ... .. ........ . ... . .......... , . . ..... . 
Gray lime . . . .. .............. . .... .. . . . ... . . . ... . 
Black gumbo ........ . ... . ..... . ...... . .......... . 
Gray lime ...... . ...... . ...... . ...... . .. . .... . .. . 
Black gumbo .............. . ..... . ... . ........ . . . 
Gray lime ............... .................... .... . 
Blue gumbo pyrites............................... , 
Gray lime . ...... . .. . ....... . .. . . . .......... .. .. . 
Black gumbo ..... ... ...... ....... ............ ... . 
Light blue shale... .............. ........... ..... . 
Black lime ............. -; ...... .................. . 
Blue gumbo . ..... .. .... . ....... . .... ... ..... .... . 
Sandy gumbo .......... .. .. . ..... .. ............. . 
Sandy shale ...... . .......... . .............. . . .. . 
Dark blue gumbo .......... ........ , ........ .... . . 
Limestone, light to gray..... ..................... . 
Black shale, pyrites... .. .. ... .. . ... ... ... . ... . ... . 
White lime .......... . .... ..... . . . . ........ ... . . . 
White and light blue shale. ... . . . ....... . .. .. . . ... . 
Dark shale, fossils . ............ .. .... . .. . .. . . . ... . 
Black lime .. . .. ... .. . .. ..... .. ........ .... .. . ... . 
Streaks shale, lime, pyrites. ...... . . . . ... .. .. . . . . . . 
White lime . . ............. . .... . .... ... ...... ... . . 
Dark' shale, lime concretions ................. ..... . 
White lime ... . ........... .. .. . .. , ... .. ......... . 
Dark blue shale.............................. .... . 
Gray lime .... .. ... . ....... . ...... . ..... .. ...... . 
Dark shale .......... .. . . .... . .......... . .... . . . . 
Gray lime ............... ........... .......... .. . 

57 985 10 995 65 1060 7 1067 323 1390 27 1417 19 1436 2 1438 39 1477 41 1518 60 1578 3 1581 14 1595 64 1659 2 1661 107 1768 2 1770 50 1820 11 1831 71 1902 3 1959 51 1956 3 1559 102 2061 4 2065 38 2103 3 2106 80 2186 20 2206 25 2231 25 2231 11 2242 61 2303 522 2825 1 2826 16 2842 4 2846 4 2850 14 2864 19 2883 12 2895 7 2902 88 2990 9 2999 27 3026 1 3027 38 3065 
The Geology of Coke County 
Dark shale 
Gray lime ......... . ... ...... .... .. ... ... . .... .. . 
Dark blue shale ................................. . 
Gray lime .......... ... ........................... . 
Light blue shale, fossils........................... . 
Limestone ...................................... . 
Black shale, coal seam.. ...... ... . .. ......... .... . . 
White silica sand, water.......................... . 
Gray lime .............. .. ...... ... ..... ........ . 
Dark shale, lime concretions sandstone lentils ...... . 
White lime ..................................... . 
Dark shale ...•....... . .......................... 
Limestone, mottled, fossils................. .. ..... . 
Black rotten lime and shale...................... , . 
Black arenaceous limestone very hard... . ......... . 
Black shale .. ... . ...... ......•...•.•............. 
Black lime 
Black lime .. .. . . ............ .................. .. . 
Black lime ...................................... . 
Black shale ..........·................. .. .. ... ... . 
Black lime ...................................... . 
Black shale .............................. . .... .. . 
Black lime ...................•................... 
Black shale .. .. ............. .•. .... . ............. 
Black lime ...................•................... 
Black shale . . ............... .................... . 
Black lime ... .......... ......•.. . ................ 
Black shale ... ... .. . . ....... .. . ................ . . 
Black lime ...................:• •.................. 
Black shale ....... . ..... .............. . ....... .. . 
Gray lime ............ . ......•................... 
Black flinty lime ..... .... . ... ... ............ . ... . 

47 
1 3066 7 3073 29 3102 4 3106 152 3258 5 3263 42 3305 10 3315 .6 3321 529 3850 1 3851 9 3860 37 3897 23 3920 10 3930 4 3934 6 3940 4 3944 16 3960 10 3970 3 3972 3 3975 4 3979 5 3984 3 3987 3 3990 2 3992 3 3995 15 4010 35 4045 3 4048 4 4052 
Log of Texas Elkhorn Syndicate Well, Richardson No. 1 
Sterling County. Elevation 2200 feet Log Kept by H. H. Jones, from 3735 Feet to Bottom. Was Kept by other Drillers 
Soil ...... ...... .. ......... . .... : ..... . ......... . 
Gravel .................. .. ... .... . . .. . . . ........ . 
Lime. ... . . .... ... .. .. . .............. . ........... . 
Red rock ........................................ . 
Red rock ........................................ . 
Hard lime· ....................................... . 
Red rock . .... .................. . .... . ...... ..... . 

Above That It 
Feet From TO 0 12 12 80 80 85 85 120 120 330 330 336 336 485 
48 University of Texas Bulletin 
Lime 485 490 
Red rock .. ......... ..................·.......... . 490 500 
White lime ..................................... . 500 540 
White lime ..................................... . 500 500 
Red rock ...................................... .. 540 550 
Blue slate ...................................... . 550 760 
Red rock .................. ........... ........... 760 790 
Shell lime ........... .. . . ....... ................ . 790 795 
Red rock ......... .. ..... ... . : . ............ ..... . 795 985 
Shell lime ....................................... 985 990 
Red rock ...... .. .. .. ............. .............. . 990 1170 
Lime .................................. · · · · · · · · · · 1170 1185 
Slate and lime blue in shells...................... . 1185 1425 
Hard gray lime.................................. 1425 1450 
Blue shale ... .. ....... .... ........... ....... . ... . 1450 1550 
Sand; hole, full water........................... . 1550 1580 
Blue shale ...................................... 1580 1633 
Lime .................................. · · · · · · · · · 16:33 1682 
Sand, salt water................................ . 1682 1696 
Pure lime ......... . .... . ............... .. ...... . 1696 1730 
Sand, water ... .... .. ......... . ...... . ... ....... . 1730 1780 
. Sandy lime ..................................... . 1780 1822 
Sand, salt .......... .. .... . .............. .. .... . 1822 1896 
Sandy lime .... . ........ . ........ .. ... . ......... . 1896 2381 
Sand, water .................................... . 2381 2387 
Sandy lime ................ .. .......... . .. .. . . . . 2387 2447 
Sand, water ............ .. .. .................. .. . 2447 2459 
Sandy lime ..•................................... 2459 2760 
Sand, sulphur water............................. . 2760 2778 
Gray shale and lime............................. . 2778 2816 
Gritty lime ..................................... . 2816 2852 
Lime and shells................................. . 2852 2935 
Hard gray lime................................. . 2935 3092 
Dark shale ..................................... . 3092 3150 
Hard, close dark gray lime ..... ~ ... . ..... ....... . . 3150 3185 
Dark calcareous shales........................... . 3185 3540 
Sand (?) .............• ..•..• ........ ; ......... . 3540 3558 
Gritty lime ..................................... . 3558 3638 
Blue shale ...................................... . 3638 3657 
Shale and lime.................................. . 3657 3750 
Black lime ..................................... . 3750 3798 
Shale, slate and lime........ , .................... . 3798 3830 
Gray lime, turning black......................... . 3830 3865 
Soft gray lime, 5 gallons 40 degree oil...... . .... . 3865 3668 
Light gray lime.................................. . 3868 3918 
Brown to black lime . ...................... .. .... . 3918 3924 

The Geology of Coke County 
Gray lime 3924 3940 Dark lime 3940 'l9'66 Gray lime ... . ... . . .. .................. . ........ . 3966 3980 Light gray fine-grained lime ............... ...... . . 3980 4000 Dark lime ......... .. ..... . . . .... . ..... .. ...... . . 4QOO 4005 Light yellow lime ................. ............... . 4005 4023 Black slate .... . ... . .... . ..... .. ... .. ... . ... . ... . 4023 4030 Slaty lime .. , ............................ ....... . 4030 4043 Dark mottled lime........... .................... . 4043 4112 White fossiliferous lime . .. . . ... . ...... ... .. . ... . . . 4112 4153 Salt water with sulphur odor, beginning about ... .. . 4140 

CORRELATION 
Before taking up the details of correlation, two general facts must be considered: First, that the Coke County beds are an upward continuation of stratigraphic succession described in Runnels County9 ; second, that an unconformity exists between the Choza and San Angelo formations which may be of very great extent. 
Near Bronte, for instance, there are 270 feet of the 
Choza formation above the Merkel dolomite, while near the 
Texas and Pacific Railroad in the next county on the north, 
this interval is reduced to 25 feet. This difference, amount­
ing to 245 feet, is probably erosional. 
There appears to be evidence to the southward, the de­
tails of which have not yet been worked out, which suggests 
a strong erosional unconformity or a considerable overlap 
by the San Angelo formation. 
The Middle or Upper Middle Choza formation of the Clear Fork Stage, when correlated by its ammonoids, may repre­sent the basal Leonard formation, according to Bose. who states :10 "But our horizon 3 (Choza formation, Runnels County) may possibly correspond with the lower part of the Leonard formation (horizon of Perrinites) ; at least, the difference in age cannot be very great." 
However, fossil ammonoids have been found in the overly­
9The Geology of Runnels County. Univ. Texas Bull. 1816, 1919. 10The Permocarboniferous Ammonoids of the Glass Mountains, West Texas, etc. Univ. Texas Bull. 1762, p. 207. 1919. 
ing Double Mountain beds which show that "Our horizons 4 and 5 certainly correspond exactly to the Horizon of Perrinites vidriensis or upper Leonard formation"11 of the Glass Mountains region. 
If the nautre of the Leonard formation is taken into ac..: count we find that throughout its thickness it is to a very considerable degree composed of conglomerate,12 and that it overlaps thousands of feet of strata to the. southward. In the Mount Ord Range, some miles south of Lenox, it is largely a conglomerate and rests upon Pennsylvanian strata which are older than the Gaptank. Passing northeast from here the Hess, Wolfcamp and Gaptank formations come in beneath it before reaching the north end of the Marathon basin. These three formations as exposed have an aggregate thickness of more than 4600 feet and their southern extermities are completely bevelled by erosion. It is now apparent from Bose's correlation that the San Angelo conglomerates lie below the upper Leonard and .that their base is at least near the base of the Lower Leonard formation of the Glass Mountains, making it possible that the unconformity at the base of the San Angelo beds may be a continuation of the Leonard unconformity. The prob-· ability of this being true is heightened to some extent by the fact that less erosion occurred in the Central Texas region than in the region of maximum disturbance in the 
Glass Mountains; and that higher beds referable to the underlying Hess formation would be left in Central Texas than would remain in the Glass Mountains. Hence, forms of ammonoids more closely related in time and form to those of the Leonard than are any known in the Hess for­mation of the Glass Mountains, might be expected in Cen­tral Texas. Another possibility is that the unconformity of Central Texas, as shown in Coke County, may represent some of the horizons of the Lower Leonard itself. In either case we would expect to find preserved in Central 
11Loc. cit. 12Udden, J. A., Notes on the Geology of the Glass Mountains. Univ. Texas Bull. 1753, Bureau Economic Geology, p. 46. 1917. 
Texas beds below the unconformity carrying younger faunas than would be found in the region of maximum dis­turbance, where a larger amount of the higher beds of the Hess formation were probably removed by erosion. At any rate it is reasonably safe to assume that the uncon­formity at the top of the Clear Fork beds is referable to the one at the base of the Leonard formation in the Mara­thon region. 
Followed still farther northward we find the Clear Fork largely composed of shales with some gypsum beds, and the Double Mountain sandstones very thick, with gypsum de­posits coming in abpve them. This is the basis for Cum­mins' separation of the two, as he points out in his papers in the Reports of the Texas Geological Survey. 
It is worthy of note that Gould records some 200 feet o{ Whitehorse sandstone followed by beds with very heavy gypsum deposits in the Panhandle region. These gypsums and associated rocks he calls the Greer formation. It is reasonably certain that the gypsums of the Double Moun­tain formation correspond in a general way to those of the Greer formation, and the succession is similar in Oklahoma and Central Texas, as Wrather pointed out.13 There is also strong reason for regarding the fossil-bearing beds of Whitehorse· sandstone seen at its type locality at White­horse Spring, 18 miles west of Alva, Oklahoma, as being unconformable with the beds upon which the sandstone rests. 
Thus it appears that this unconformity represented by the base of the San Angelo formation is of great extent and is probably the most valuable horizon marker in the Per­mian of Texas. If this conclusion is correct, the Clear Fork and the upper part of the Wichita formations are equivalent to the Hess formation of the Glass Mountains. The lower part of the Wichita beds would probably repre­sent the basal Hess formation and Wolfcamp formation, if the Wolfcamp is represented in central Texas. 
The Schwagerina horizon is doubtfully represented in the 
13Bull. S. W. Assn. Petr. Geol., p. 103. 1917. 
University of Texas Bulletin 
central part of Texas. We know of no reference to these fossils, though they may exist and have been overlooked. There is one specimen of Fusulina from the base of the Wichita beds representing a species that occurs in the Schwagerina horizon in Kansas and Oklahoma. It may be that the horizon is present and the Schwagerina want­ing, or that there is an elision of the formation in central Texas. It may be noted here that Bose and also Martin found some evidence ·of disconformity near Moran, in Shackelford County. Its extent and significance have not been determined. The horizon in the Wichita stage in which Omphalotrochus occurs on the· Colorado River is high enough above the base of the stage as now considered to make it likely that the Schwagerina beds are present; but that the fossils are absent or have not been observed. For the present, the base of the Wichita formation is to be considered as tentatively defined. The main Schwagerina horizon of the Marathon region includes the topmost part of the Gaptank and part, at least, of the Wolfcamp beds. In Kansas and Oklahoma this horizon is represented by the Neva limestone and immediately associated rocks. A fea­ture to be held in mind is the fact that in the great lime­stone sections of extreme West Texas many species have a much greater range than in the interrupted limestone-shale succession of the central and northern parts of the state, or in Kansas. 
The rocks above the San Angelo beds comprise the sec­ond formation of the Double Mountain stage. Wrather traced some of the Texas gypsums through to the Red River and in his paper on the section from Abilene to Sweetwater he placed the rocks from the top of the San Angelo f orma­tion (Blowout Mountain sandstone) to the top of the heavy gypsums, in the Greer formation of Oklahoma and the Texas Panhandle.14 The rocks above this gypsum he referred to the Quartermaster formation of the Panhandle. The heavy Coke County gypsum beds would then belong to the Greer formation. As has already been stated, Wrather tenta­
14Wrather, W. E., Notes on the Permian. Bull. S. W. Assn. Petr. Geol., p. 103. Hll7. 
The Geology of Coke County 
tively refers the limestone or dolomite in these gypsums to the Eskota dolomite. 
The conglomerate at the top of the red beds in the north­west corner of the county may well represent the base of the Quartermaster of Gould, so far as our present knowledge goes. There is a similar thickness of shales above the top of the massive gypsums of the Greer in the Coke County section to correspond with the interval between the gypsums and the sandstones of the Greer and Quartermaster beds of the Panhandle. The green chert abundant in some parts of this conglomerate probably comes from the Caballos forma­tion of the Marathon region. 
It seems that the Coke County region was sufficiently close to the region of major movements to the southwest in early Permian times to have the unconformities with their over­lying conglomerates clearly developed, which are now re­vealed in exposures on the northern edge of the Edwards Plateau. This fact will be of great importance in inter­preting the age of the Permian formations of north Texas. 
Comanchean 
Section at Mt. Margaret 
Feet Inches :31. Thin ledge at top of hill.. ... . ............. . ... . 1 :30. Limestone, massive, full of Caprina, weathers smooth ........... . ................ . ...... . 5 
29. Limestone and concealed... .. .......... . . ... .. . . 10 

28. Limestone, hard bed . .. .. .............. .... . ... . 2 8 

27. Limestone, hard .... . ..... ... ...... .. ......... . 5 

26. Limestone, somewhat flaky ... ......... ... ..... . 4 

25. Limestone, very hard, fine grained, 11 inches to .. . 1 3 ·24. Limestone, nodular, marly, or hard nodular marls, 
quite fossiliferous  .. . ......... ... ... ... .... .  10  6  
·23.  Limestone  with  geodes  and  large  gastropods,  
pelecypods  ....... .. ... . ...... ..... . ...... .  4  
·22. Limestone, less resistant than  one  below........ .  4  
21. Limestone,  massive,  rather  fine-grained,  weathers  
smooth  .... ... . . . ..... ..... . ..... . ........ .  8  
20. Sandstone and sandy limestone ... .. ...... ..... . .  3  
19. Clays-Walnut?  ..... ..... . . ... . . ... ...... .. .. .  15  
18. Sandstone, buff, fine ,apparently calcareous . .... . .  5±  
17. Sandstone, algal ( ?)  about this horizon ......... .  2  

University of Texas Bulletin 
16. Clay, olive, occupies most of interval.......... .. .  20  
15.  Soncealed  .. .. . ... . .... . ........... . . . . . .. . ... .  15  
14. Sandstone, concretionary, concretions about the size  
of marbles, at about this level. ......... . .... .  2+:  
13. Concealed, apparently wash from  higher up ..... .  45  

79 
This section rests upon the Permian section given in the, preceding pages. 
Comanchean Section of Small S.outheast Peak of Kickapoo Mountains 
Feet Inches, 
13. 	Limestone, somewhat nodular below, poorly exposed at base, 5 feet, followed by 13 feet 2 inches of massive limestone which weathers cellular in upper part. All one bed . . . ... ..... . . . .... . . 18 
12. Concealed . ... ... ........... . ... . ..... . ...... . 10 

11. 	Clays and marls lower part more buff and clayey than upper part. Exogyra texana. There is a limestone of considerable thickness partially exposed above the clays and making the whole interval 17 or 18 feet . . ... . ............ . ... . 17± 
10. 	Limestone, fossil conglomerate, Gryphaea, Exogyra texana, large and small pelecypods; weathers into small lentils below, upper part weathers into blocks and is lighter colored and firmer than the lower part of the bed ... ... . . .. . . .. . 11±­
9. Clay, sandy, calc.ireous, some concretions .. . . . ... . 5 
8. Sand, loose, fine-grained, buffish ...... . . . .. . . . .. . 6 
7. 	Sandstone, with some fine pebbles, rather da.rk­colored ............. . ........ . ..... .. ..... . 5 
6. 	Conglomerate, buff, more or less concretionary, calcareous, 7 feet to .. . . . . . .......... . ... . . . 8 
5. Sands, ashy, apparently some clay ............. . 12 

4. Sand, soft, whitish and buff, and covered slope . . . . 25 
3. Clay, an<l yellow sand streaks, 6 feet to ... . ... . . . 8 
2. 	Sands, ashy and soft sandstones, 2 feet of fine concretionary rnndstone at top . ...... . .... . . 16 
1. 	Shale, green, and sandstone nodules, some sand­stone and fine iron concretions ... . . .. ..... . .. . 
11 
152-t-­
The Geology of Coke County 
Comanchean Section of Northeast End of 
Kickapoo Mountains 

11. 	Limestone, chalky, very cellular, higher beds back in ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 
10. Limestone, chalky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 
9. Limestone, chalky, seven or eight layers. . . . . . . . . . 10 
8. Limestone, chalky, upper part cellular, chert. . . . . . 6 
7. Limestone, upper part filled with chert. . . . . . . . . . . 12 
6. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 
5. Limestone, massive . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 
4. Limestone, nodular, and concealed, very fossilifeous 15 
3. Limestone, nodular, base a fossil conglomerate. . . 12 
2. Clays, Exogyra texana, Gryphaea.. . ....... . . .. . 5 

1. Sand. Trinity, and material like it.. ... .. .. . .. . .. 114 
221 
Section at "Mount Q." "Butterfield" is given on an old map but it is uncertain whether this refers to the name of the mountains er the survey. In our notes it is given the designation "Mount Q." It is a high outlier just in front of •the plateau escarpment in Surveys 10 and 11, south of the oil well being drilled by Mr. Tucker. 
Feet  Inches  
43.  Limestone, top of section,  almost completely com­ 
posed of foraminifera,  some  gastropods.  Pos­ 
sibly  .. . . . ................. . ..... . ........ .  1  
42.  Concealed  . . .. .. ...... . . .. .... . . ....... . .... . . .  7  
41.  Limestone,  concealed  .......... . ............. . .  2  
40.  Limestone, coarsely crystalline,  about ...... ..... .  1  
39.  Interval.  . . . . ... ..... .. ..... .. ................ .  1  
38.  Limestone, hard, resistant, in four  layers .. . . . .. .  12  
37.  Limestone,  massive, hard, white,  weathers  to  cel­ 
lular surface, in three or more  layers.  about. .  9  
36.  Interval  ..... ... .................... . ....... . .  1  6  
35.  Limestone,  massive, weathers cellular.  Layers  51h  
feet above base with  numerous  gastropods... .  11  
34.  Concealed  .. ... .. ... .. . ..... . ....... . ..... . ... .  6  
33.  Limestone,  laminated,  yellowish white .. . . ....... .  8  
32.  Concealed  .. ... ... .. . ..... .. . .. ... .... .. . .... . .  1  
31.  Limestone,  rotten.  cherty.. ................... . .  2  
30.  Concealed. . . . .. .. .. . ... . . . .. . . ........ . ... . ... .  2­ 
29.  Limestone, chalky, white. with yellow streak.. : .. .  1­ 
28.  Concealed  . . ........... . .................... .. .  8  
27.  Limestone. nodular, white, eccasional geodes, about  6  

56 University of Texas Bulletin 
26. 	Limestone, white, platy, bottom half soft, top hard and resistant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 
25. Concealed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
24. Limestone, nodular, rather soft. sandy.... . . . ... . 4 
23. Limestone. white, foraminiferal . . ...... . .... . .. . 1 6 
22. Concealed .................................... . 2 

21. Limestone. hard. white....... . . . . . . . . . . . . . . . . . . . 10 

20. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 
19. Limestone, hard, sponges?..... .................. 3 

18. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . 2 
17. 	Limestone, massive, weathers into nodules, lower ten feet soft, upper part hard, dense. Foram­inifera, Pecten, etc.. . . . . . . . . . . . . . . . . . . . . . . . . 22 6 
16. Interval. Upper 3 or 4 feet marl.. . . . . . . . . . . . . . 11 
15. Limestone. nodular . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10± 
14. Concealed, some shale. . .. . ... . . . ...... . ........ 6± 

13. Sandstone, yellow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9± 
12. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 
11. Sand, yellow, soft..................... ......... 6 

10. Clay, soft dirty-white. . . . . . . . . . . . . . . . . . . . . . . . . . . 18 
9. Sand, soft, yellowish. . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 
8. Sandstone, soft, gray, shot-like concretions. . . . . . . 3 6 
7. Sand, loose, yellowish-whit~..... . ... . . . ... . . . ... 5 
6. shale, reddish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 
5. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 
4. Sandstone, gray, fine shot-like concretions. . . . . . . . 4 
3. Sand, soft, yellowish .... ...... : . . . . . . . . . . . . . . . . 11 4 
2. Concealed ...... ......... ·. . . . . . . . . . . . . . . . . . . . . . 10 

1. 	Sandstone dark-buff, fine-grained. . . . . . . . . . . . . . . . 10 The entire section is composed of Comanchean rocks. It is uncertain whether or not the section reaches the base of them. 
Section, Southwest Corner of Cole Mountains 
44. 	Limestone, massive, even-bedded, composed of small fragments of shells, forms top of mountain . . . . 10 
43. 	Limestone, soft, chalky, weathers into large blocks, especially the basal part. Chert nodules and layers, more chert in the lower part. Top much harder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 
42. Limestone, fine-grained . . . . . . . . . . . . . . . . . . . . . . . . 6 
41. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4 
40. Limestone, hard, fine-grained. . . . . . . . . . . . . . . . . . . . 16 4 
89. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5 
The Geology of Coke County 
-38.  Limestone, hard, massive, resistant, numerous gas­ 
tropods. Weathers into spalls from 7% feet  
above the base up for the next 5 feet; next 12  
feet Radiolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38  
37.  Concealed. Lower 5 feet yellowish white clay.  
Exogyra texana (in place?) . ... . .... .. . . . . .. 117  
36.  Concealed, partly, mostly red sandy shale, upper  
part red shelly sandstone. . . . . . . . . . . . . . . . . . . 19  
35.  Concealed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5  
34.  Sandstone, red, thin-bedded, shelly. . . . . . . . . . . . . . . 6  
33.  Shale, greenish-yellow. . . . . . . . . . . . . . . . . . . . . . . . . . . 1  
32.  Sandstone, shelly, yellowish-white, fine-grained. . . 2  4  
31.  Shale, red, sandy, streaks of greenish-white sand,  
upper 12 inches nearly all sand. . . . . . . . . . . . . . 2  6  
30.  Sandstone, yellowish-white, thin-bedded, fine- 
grained, jointed . . . . . . . . . . . . . . . . . . . • . . . . . . . . 5  5  
29.  Sandstone, red, shelly, upper three inches greenish- 
white . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0  9  
28.  Sandstone, • yellowish-white, fine-grained, thin­ 
bedded, jointed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10  
27.  Sandstone, red, shelly, thin streaks greenish-white  
sand ...-. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  9  
26.  Shale, yellowish-green, calcareous, crusty. . . . . . . . 1  
25.  Sandstone, yellowish-gray, fine, thin-bedded, much  
jointed, cross-bedded . . . . . . . . . . . . . . . . . . . . . . . 7  
24.  Sandstone, like No. 20, upper part more massive. . 5  6  
23.  Sandstone, like No. 21........ . . . . . . . . . . . . . . . . . . 1  
22.  Sandstone, reddish, shelly, like No. 20. ........ . .. O  6  
21.  Sandstone, gray-white, yellow streaks, cross-bedded 1  
20.  Sandstone, fine-grained, reddish, with white streaks,  
cross-bedded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  7  
19.  Shale, red, shelly, sandy, with greenish-white sandy  
streaks, gypsum . . . . . . . . . . . . . . . . . . . . . . . . . . . 6  
18.  Sandstone, alternating red and greenish white, at  
top, lightly cross-bedded. Thin, massive gyp  
sum layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6  6  
17.  Sandstone, greenisb. with alternating thin beds of  
massive gypsum . . . . . . . . . . . . . . . . . . . . . . . . . . . 4  O  
16.  Shale, red, sandy, with streaks of greenish sand  
and layers of massive gypsum. . . . . . . . . . . . . . . . 6  6  
15.  Gypsum, massive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4  2  
14.  Shale, red, with greenish-white streaks of fine  
sand, joints filled with foliated gypsum . . . . . . . 3  2  
13.  Sandstone, fine, greenish-white......... . .... . ... 2  6  
12.  Shale, red, sandy. ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  o  
11.  Gypsum, massive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  4  

University of Texas Bulletin 
10. 	Sandstone, red, with greenish streaks, joints filled with gypsum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 R 
9. Sandstone, greenish, with gypsum streaks. . . . . . . . 1 
8. Shale, red, sandy, with gypsum streaks....... ... 9· 

7. 	Sandstone, greenish-white, with nodules of gypsum, joints filled with gypsum. . . . . . . . . . . . . . . . . . . . 4 & 
6. 	Shale, red, satinspar in thin plates filling joints in 
all directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

5. 	Sandstone, greenish-white, with gypsum in vertical 
and transverse joints . . . . . . . . . . . . . . . . . . . . . . . . 11 

4. 	Partly concealed, upper 15 feet red shale with 
massive gypsum and thin streaks of greenish 
white sand ........ .... .. ..... : . . . . . . . . . . . . 39 

3. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 
2. Shale, red ............ ·. . . . . . . . . . . . . . . . . . . . . . . . . . 5 

1. Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 
This section gives a clear ·idea of the locfl,l condition of the Greer beds at this place. The. gypsum beds seem to be thinner than in some other places. · It is difficult to say how much represents the gypsiferous beds above the limestone in the Grubbs Canyon and Wilson Mountain sections. The limestone is either absent or was not especially distinct in this section. This limestone bed is locally quite inconspic_­uous and looks like a secondary crust of little importance. It had not been studied at the time this seetion was meas­ured and it may have escaped attention. The Greer beds here may reach to the top of Number 36 of this section. Number 37 is apparently the base of the Comanchean. 
It is 	quite possible that. some of the sandstone below 
Number 37 may belong to the beds above the Greer, which 
are represented but a short distance farther north by con­
glomerates which extend to the Panther Gap section. 
The Comanchean section is well developed here and is ex­cellently exposed. On the Edwards Plateau along the Rob~ ert Lee-Carlsbad road, the barometer shows a thickness of approximately 350 feet of Comanchean rocks. 
Section of South End of West Stepp Mountain 
Near Northwest Part of Coke County 

Feet 
27. Limestone, even-bedded, massive, 1 to 3 beds.. ..... 15 
26. 	Limestone, somewhat laminated, porous, top quite 
craggy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

The Geology of Coke County 
25.  Limestone, marly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3  
24.  Limestone, massive bed, top of cliff. . . . . . . . . . . . . .  4  
23.  Limestone, brecciated . . . . . . . . . . . . . . . . . . . . . . . . . .  10  
22.  Limestone massive, Caprina and larger fossils . . . .  12  
21.  Limestone, darker colored bed, weathering into  
quite rough blocks with geode-like pits. . . . . . . .  4  
20.  Limestone, massive, much like lower bed but firmer  25  
19.  Limestone, marly, to massive-nodular, Exogyra  
texana, slim gastropods. . . . . . . . . . . . . . . . . . . . .  25  
18.  Concealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  65  
17.  Sandstone, buff-brown, calcareous, Grypluiea, grad­ 
ing into limestone at top, total thickness prob­ 
ably . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10  
16.  Sands ashy and sandy clays probably much thicker  
than seen ............................ .-. . . .  15  
15.  Shale light-colored red. . . . . . . . . . . . . . . . . . . . . . . . . .  5  
14.  Sandstone dark maroon . . . . . . . . . . . . . . . . . . . . . . . .  5  
13.  Shales deep m!'.roon, somewhat sandy, with thin  
sheets of sandstone . . . . . . . . . . . . . . . . . . . . . . . . .  5  
12.  Sandstone, laminated, buff-gray. . . . . . . . . . . . . . . . . .  10  
11.  Conglomerate :md coarse sandstone, chert and  
quartz pebbles . . . . . . . . . . . . . . . . . . . . . . . . .  5  
10.  Shale, one sand bed. . . . . . . . . . . . . . . . . . . . . . . . . . . .  6  
9.  Sandstone, more evenly and thinly bedded than  
those below, soft.................. .. .......  15  
8.  Sandstone, cross-bedded, coarse, large lenses of  
coarse conglomerate which contains slabs of  
sandstone 2 feet across, yellowish. . . . . . . . . . .  20  
7.  Shales, greenish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10  
6.  Sandstone, coarse, soft, friable, buff to light red  
or pink; much of it very coarsely conglomeratic,  
iron-cemented, very dark brown to gray. . . . . .  10  
5.  Shale, buff to olive. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6  
4.  Shale, gray to red, more or less platy and sandy. .  15  
3.  Sandstone, gray to maroon, slabby, ripple-marked  5  
2.  Shale, gray to greenish, and red, more or less fer­ 
ruginous, in places sandy.............. , . . . . . .  5  
1.  CAnr.ealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  20  
336  
Tertiary ( ? ) Pleistocene ( ? )  

The floor of the old valley between the Edwa.rds Plateau and the Callahan Divide is covered with coarse conglom­erate, some sands and silt. The age of this deposit has not been determined. It is probably Late Tertiary, or Pleis­
University of Texas Bulletin 
tocene. 
These deposits vary in thickness from a thin veneer to 60 feet, and in elevation from 90 or 100 feet above the river to probably 150 feet near the margins of the old valley. Much of this material is a coarse limestone conglomerate, locally loose boulders, but in other places well cemented. Some of it is rather fine, while other parts of it carry peb­bles as large as hens' eggs, and at still other localities buol­ders a foot or two in diameter. The stones are usually well rounded. Most of the boulders and pebbles are the hardest of the Comanchean limestone mingled with some chert from the Edwards limestone. Frequently these lime­stones are almost entirely composed of foraminifera. 
Where these deposits are favorably located they are very often tightly cemented with caliche and contain sufficient amounts of iron oxide or red clay to form a dense, whitish­to reddish-mottled conglomerate. Otherwise the beds are white. 
There is, in many places, a considerable layer of silt or soil over this conglomerate. 

Recent 
The clay and sand beds along the present first and second bottoms of the river, and in the river bed, and the soil of the first bottom with some gravel beds, constitute the recent deposits. They are very limited in this county and are shown approximately on the map. 


ECONOMIC GEOLOGY 
Sand 
Probably the most notable sand deposit in the county is on Sand Creek, south of the "Colorado Road," in the north­western part of the county. The sand here is largely dune sand. It is present in great quantities though it is distant from points where it could be extensively used, and is not on any transportation line. 
There are sand beds which occur as bars and similar 
University of Texas Bulletin No. 1850. Plate V 
A. Stepp Mountain. The lower part is Quartermaster (?) and the upper part is Comanchean. 
B. Undercut rock, Comanchean, on north side of Grubbs Canyon. 

The Geology of Coke County 
deposits along the Colorado River of sufficient size and purity, if carefully selected, for local use. 
Occasionally three are sand beds in the old valley such as the one in the road west and north of Bronte. Sometimes these beds contain considerable clay. 
Another source of sand is that found in the basal part of the Comanchean rocks at the foot of the Edwards Pla­teau and the Callahan Divide. These sand beds are indi­cated in the sections of the Comanchean deposits. On the whole, the county is well supplied with sand. Should cheap fuel be developed in the county it may be that beds of sand of sufficient purity may be found in the basal Comanchean formations, to make a good glass sand. 



Clay 
In the study of the rocks of Coke County only low grade clays were encountered, that is, clays suited only for the manufacture of building brick, drain tile, etc. 
The alluvial clays of the county are quite limited and im­
pure. They are the soil of the first and second bottoms of 
the Colorado River. The shales of the Choza formation 
in the eastern part of the county, and of the San Angelo 
formation near Robert Lee, are of most importance. The 
former outcrop along the bluffs on the ~outh side of the 
river as far north as the Kansas City, Mexico and Orient 
tracks and a short distance beyond. These beds also occur 
on the north side of the river as far as Bronte. The out­
crop of this formation is shown on the map. 
Near Robert Lee and eastward in the exposed bluffs along the river and main creeks are beds of clayey shales in the San Angelo beds and in the base of the Greer beds. Clay will be found among these shales which are suitable for the manufacture of ordinary brick. 
Some of the lighter-colored clays of the lower part of the Comanchean rocks exposed in the base of the mountains north and south of the Colorado River may be of such a constituency as to burn a light-brown brick suitable for ordinary use, should cheap fuel be available. 
Lime 
About the only source of limestone for lime in Coke County is the limestone of the Comanchean formations found in the mountains of the county. 
This limestone occurs in abundance and many of the beds are of sufficient purity to burn excellent "hot" or "fat" or quick-setting limes, such as as are most used for ordinary purposes. They would have no superior for "hard wall finish," if ground and made into the hydrated limes of com­merce. Distance from market, and costly fuel preclude their manufacture except for local use. A less important but more accessible deposit would be the Comanchean limestone boulders of the old valley. 

Limestone 
The limestone resources of the county are the same as those just mentioned for lime. These Comanchean lime­stones outcrop in the mountains in such a way that but slight work is necessary in quarrying them. The rocks from many of the beds can be readily shaped into large­sized blocks with but little work and many of them can be sawed Into any desired shape. This work can be done at times when farm work is slack or other work is not press­ing. Work of this character can go on for several years and the rock can ·be accumulated until a sufficient amount is at hand which, with very little cash outlay, can then be used in erecting buildings. The lime can be burned from the spalls and the sand for the mortar is readily available. These are the best buildings that can be constructed, as wen as the cheapest. 
Many fine houses have been built in this way in other 
parts of the country and give very satisfactory results. 
They are permanent improvements that add materially to 
the value of any property. 
Three precautions are necessary to good results. First, 
a firm foundation which will permit of no settling of the 
walls is necessary. Excavation must be carried deep enough 
to secure a firm foundation; and then it is a good plan to 
place a layer of good concrete one or two feet thick and a foot or so wider than the wall. Second, only large-sized blocks should be used. Third, the rocks should not be blasted in quarrying, as it fills them with invisible cracks that shorte the life of the stone as well as weakening the build­ing. If blastnig can not be avoided, the smallest charges capable of doing the work should be used. The explosive should be a slow burning coarse black powder. Dynamite should never be used in quarrying rock to be used for build­
ing or other structural purposes. 

Gypsum 
The gypsum resources of the county are large. The available deposits are IOcated in the western half of the county. Their occurrence is given in the description of the sections in this report. The easternmost point where gypsum is likely to be available in commercial quantities is the Seaton Keiths Bluff, three . miles west of Robert Lee. The thickness of the beds is given in the section of the bluff on page -, and in the general section of the county. 
Another bed is found near Grubbs Canyon, which is good 
pure gypsum. A still higher deposit should occur under 
the mountains west of Grubbs Canyon. This is the same 
general deposit, composed of the several beds, found near 
Wilson Mountain in the northwest part of the county where 
the beds have an aggregate thickness of about 80 feet. 
Very little advantage can be taken of the deposits at 
present, owing to lack of fuel, transportation, and market. 
However, should it happen that gas in quantity should be 
struck in the terrace of western Coke County, the material 
could be quarried and burned with that fuel so cheaply that 
these deposits might become of economic importance. The 
products made from these gypsums might include plaster 
of Paris, dental plaster, and the "cement plasters." The 
process of manufacture of these products is simple. 
University of Texas Bulletin 


Road Metal 
One of the resources likely to prove to be of much value to the county is the material for road construction. There are two kinds to be had. First, there is the gravel from the San Angelo beds in the eastern part of the county. These gravels or conglomerates occur from the Tom Green county line along the Kansas City, Mexico and Orient Railroad to Tennyson around Fort Chadbourne, in the Kickapoo Moun­tains, Cedar Mountain, and in lower Live Oak Creek on the Humlong ranch. This is essentially a quartz gravel with sand. Some of it is firmly consolidated into a conglomerate or "concrete" and would require crushing. while at least a fair amount can be had as free gravel. This deposit has been described under the head of the San Angelo formation. 
"In the western part of the county the quartz found con­glomerate at Panther Gap on the Colorado City road, and heretofore described, is equally useful as a road metal." 
This gravel lacks binding cement to a considerable ex­tent, but treated with a foreign binder would make the best of modern gravel roads if they are properly constructed.15 From the section given it is evident that there is an ample supply of it for local use, as well as for shipping. There should be a demand for it. It is one of the best gravels for heavy traffic in all West Texas, and nearly all of the deposit is in Coke County. Two photographs of this material are reproduced on Plate 8. 
The other deposit .of road gravel is good for the side roads of the county and it is much more widely distributed along the broad valley of the Colorado River. lt is the limestone gravel or "concrete" of the old valley floor. It extends entirely across the county and from the mountains on one side of the valley to those on the other. There are considerable areas without it, but there are few places where it can not be reached economically. The larger areas are shown on the map, in black shading. 
On~ of the best exposures known is in the top of the 
15Univ. Texas Bull. 1839, pp. 151-159. 1919. 
University of Texas Bulletin No. 1850. Plate VI 
A. San Angelo conglomerate at Kickapoo Mountain. 
B. San Angelo gravel at Mount Margaret. 

The Geology of Coke County 
Seaton Keiths Bluff, three miles west of Robert Lee. Here there are about 50 or 60 feet of it, 40 feet showing in the face of the bluff. The bluffs of Pecan Creek are covered with it, as is much of the region near the root of the Ed­wards plateau, where it is cemented with caliche. All the highlands between the creeks in the "Old Valley" of the river, especially between Bronte and Robert Lee, carry de­posits of it. It caps the low mesas east of Bronte and the longer one on the east side of the railroad between Bronte and Tennyson. In these latter localities it is accessible to the railroad. Its composition varies from place to place. As a rule it is coarse, and the boulders range from fine ma­terial to pieces a foot in diameter. Much of it is composed of the hardest of the Comanchean limestone rolled and ground in the old river until the large·as well as the small pieces are well rounded. All the softer stones have been ground up to powder and most of it washed away. How­ever, in many places this gravel is relatively fine and closely cemented into a hard conglomerate which would make an 
excellent road metal for the most of the roads of the county . . 
It would have to be crushed before being used. Some of 
the better roads of the county are roadbeds crossing natural 
deposits of the material. An example of this is the high­
land with the white road between Bronte and Robert Lee. 
In such localities the roads need but little u.ttention except 
to provide drainage. 
The iimestone and marls of the mountains make a good 
road for very light traffic, but are too soft for heary traffic. 
This material is available for most of the county. 

Oil and Gas 
STRUCTURE 
After studying the Pennsylvanian and lower Permian along the Colorado River in Coleman and Runnels counties one does not find the structure of the rocks in Coke County as simple one would expect. 
University of Texas Bulletin 
Dip 
The general dip of the Permian beds is in a direction north of west. It is much more nearly west than is the case in Runnels County where over a large part of the county it is about northwest. In a general way, the dip is approximated up the Colorado River.. In the eastern part of the county the dip is approximately 50 feet per mile; locally it is more than that. From Robert Lee westward it is slight and may be level and even locally reversed for some considerable distance; near the west edge of the coun­ty, however, a steeper dip is resumed. The average dip of the Permian rocks up the Colorado River for the whole county will probably not exceed 30 feet to the mile, and may be less. The general dip of the Comanchean beds is to the southeast. 
IM.ajor Structures 
The interruption of the normal dip noted above forms the major structure of the county. It is really a terrace with minor structures upon it, consisting of both faults and folds. The real axis of this terrace has not been determined but is assumed to be nearly north and south in the north­west part of the county. It is most apparent and most easily studied on the south side of the river from Edith to Wilson Mountain which is located in the large northward loop of t,he river near the northwest corner of the county. The best horizon marker is a peculiar dolomite bed, part of the way quite sandy, frequently cellular and crystalline, with black spots in it. Its appearance hardly suggests a limestone. It varies from about a foot to two feet in thic'k­ness, and is exposed from the hills just east of the junction of North and South Pecan· creeks to the west side of Wilson 
Mountain, above which it enters the river. On the north 
side of the river this limestone is found exposed in Silver 
Creek at the Colorado Road crossing, and thence eastward, 
at numerous points on either side of this road for several 
miles.. Its position with respect to the Panther Gap con­
University of Texas Bulletin No. 1850. 	Plate VII 
Seaton 	Keiths Bluff, three miles west of Robert Lee. 80 feet of Greer sandstone followed unconformably by 40 feet of limestone conglomerate shown above the line A-A. The conglomerate is the old river bed conglomerate of the Colo­rado. It is 60 feet thick just back of the cliff. 

The Geology of Coke County 
glomerate is clearly seen in the Gap. It is possible that an east dip due to faulting or folding will be traced on this limestone east of Panther Gap. A series of heavy gypsum beds set in on top of this limestone bed and these have been dissolved away, leaving the horizon of this bed forming the top of the general plain near the river between the points mentioned. 
One of the most interesting features of this structure is that it seems to overlie a much stronger and steeper structure beneath the unconformity at the base of the San Angelo formation. Another matter of interest is the fact that the minor structures visible at the surface are much sharper and more broken on th~ eastern part than on the weste'tn part of the terrace. Indeed, there seem to be few disturbances on its western part. The structural features of the terrace as a whole will be discussed along with other smaller folds and faults. 
Minor Structures 
Structures on the major terrace fall into two classes: Folds and faults. The folds are noted east and west of Robert Lee, near Edith, and probably will be found at other kcalities. One of the features that must be considered here is the fact that at Robert Lee and the mouth of Pecan Creek the Colorado River appears to be synclinal. The same thing is true east of Robert Lee as far as Cedar Mountain. There is little likelihood of its being synclinal west of the mouth of Pecan Creek. These small synclines along the river may be regarded as saddles on the larger terrace. Aside from these somewhat local sags there are also arches, one on Wildcat Creek, and one on Pecan Creek near the junction of North and South forks, another on the side of Mountain 
Creek just northeast of Robert Lee. Others are probably 
present. Apparently there is one on the north side of the 
river near Rough Creek. It is to be regretted that funds 
were not available to detail the structures of the Colorado 
River Valley from near Robert Lee to the west line of the 
county. No attempt has been made to locate all these struc­
tures. 
University of Texas Bulletin 
On the eastern third of the terrace are numerous faults and zones where the rocks are locally crushed. These zones probably represent slight faulting with some-lateral pres­sure which crushed the rock in vertical zones six to 50 feet or more in width. There is usually a slight displacement of the beds vertically on the sides of the crushed zone, and the crushed beds themselves show slight downward displace­ment. This crushing passes below the rocks in the beds of the creeks. 
The sandstones and sandy shales of these regions are soft and friable. The sand grains are fine and cemented with clay and fine iron oxide, and the shales are but little less sandy than the sandstones". These rocks would stanq only a slight lateral compression or strain without rupture. 
Crushed zones are associated with normal faults, though the faults themselves are usually well separated. Fre­quently they are found a quarter of a mile apart, with even­bedded undisturbed rocks between them. 
The faults are best seen on Pecan Creek. The other ex­amples seen were located in the bluffs of Pecan Creek. The accompanying photographs illustrate the appearance of these features. They occur from just above the old Arlitt ranch-house to a point a quarter of a mile above the road which crosses . the creek just below the junction of North and South Pecan creeks. One of the first bluffs above the house shows a crushed zone. The next shows a reversed fault of almost four feet, and a little forther upstream the same bluff shows crumpled light and dark shale, slightly faulted, between the sandstone layers. Some distance above this are more crushed zones and faults. The largest fault of the number discovered on the creeks is of the normal type. The largest block in htis fault is shown in the accom­panying photograph. The fault is open · above the creek level and closed below it, but the middle part contains an eight inch sandstone dike. The upper part is filled with sand and clay of surrounding beds and a triangular block of sandstone of considerable dimensions occupies the fault in the top of the exposure. There are several smaller faults on the right of the main fault, one with a displace­

University of Texas Bulletin No. 1850. 
\...) 
" 
'­
.l 
APPROXIMAll: DIAGRAMMATIC SF.CTION OF PERMIANROCKS OI' COKE COU/\TY. n:xAS. AS EXPOSED ~'EAR Tl!E COLORADO RIVllt 
J. W. BEEDE 
NOTE: Arrow1 along the fault line show direction of 
~rtical displacement, downthrow being to east. The lines 
A-A and B-B indicate the position of the corresponding 
::w~~ioru if faulted, lines C-C the same for't11ations if 

Plate VIII 
FAULTS AND OIL SHOW!NQS I 
'-' " .:uoo 

.uoo 
2.000 
1000 
1000 rm 
16\X) 
!:CO 1400 
1::.ro 
12.00 
1100 1000 
g;X) 
fil) 
TCO 
6CO 
m 
• 
Sc ole or Mdea 
University of Texas Bulletin No. 1850. 	Plate IX 
A. 	Bluff on South Pecan Creek showing crushed zone B-C. Rocks in normal position on either side, and leached z:me A-B and C-D where the rocks are light-colored. The deep red color is shown outside the leached zones. The crushed zone is also leached to a light color. Oil showing near this place. 
B. A closer and more direct view of the left side of A. Note the sharp line of change in color. 

Plate X
University of Texas Bulletin No. 1850. 
A. Reversed fault in bluff on Pecan Creek, above Arlitt ranch-house. 
Crumpled shale, slightly faulted, between undisturbed sandstone 
beds. Same bluff. No leaching of color has occurred in 
this bluff. 

The Geology of Coke County 69 . 
ment of over 10 feet. On the left side of the large fault is another in which the top bed of sandstone shown on the left side of the main fault is opposite the basal sandstone of the block next to it. This makes a total displacement of about 80 feet in this series of faults. The creek bluff is cut away on the left of the exposure and whether or not further fault­ing occurs there can not be determined. The direction of this fault is N 65° E. The direction of the thrust fault is S 30° E. Other quite small faults occur which are shown in the illustrations and which need not be described here. While no two are precisely alike, yet they all fall in one class. 
Origin: These faults are peculiar in several respects and arouse considerable interest regarding their origin. Ordinarily they are absent over nearly all the region of Central Texas. 
One of the first things to be noted here is the fact that in the case of the large fault, as well as the smaller ones, the rocks are overlaid by thick deposits of old river gravel which are practically undisturbed by these structures and, though some of the faults are open, none of them contains any of this material. In other words, these structures antedate the final development of the old valley 80 to 150 feet above the present valley of the Colorado River. The age of these graveis is unknown but it is probably either late Tertiary or Pleistocene. · In any case, the age of the structure is probably as great as the iater Tertiary. The faults have not been noted in the Comanchean beds but may be present. 
Numerous suggestions have been made regarding the pos­~sible origin of these faults, such as solution of rather deep­seated salt beds, deep-seated faulting or folding, consolida­tion of sediments, slumping, etc. 
Solution: The most apparent explanation at first thought 
would be the solution of rather deep-seated salt or gypsum beds. This might well produce structures similar to the ·Ones seen. However, it becomes necessary to assume the removal of beds as thick as, or thicker than, the largest structures seen, or 80 to 100 feet or more thick. This ~presupposes the presence of thick salt or gypsum beds (not 
University of Texas Bulletin 
an incongruous assumption in these red beds) which were removed, producing collapse structures. Most of the struc­tures are small, and well separated from each other, and the beds in the intervening areas are very even and undisturbed. Further, it is necessary to assume the complete removal of the bed at the time of origin of the structures or else struc­tures would have been forming for a long time afterward, the movements of which would probably have involved the overlying conglomerate. This is not the case, however. The disturbances are far too slight and too distant, as a rule, to be attributed to this cause. In such cases the beds should be quite broken and haphazard in their appearance as a whole. On the contrary, the beds are very even and undis­turbed except here and there. 
Consolidation of sediments: The settling of the beds might under some circumstances produce similar results~ but to account for larger faults in that manner presupposes too large an amount of differential settling. Likewise the phenomenon is too local, since it should at least be dis­tributed over the whole terrace, if not over the whole region where the same succession of beds is involved. 
Slumping: The beds of the formation here considered. show negligible evidence of slumping along the creek and river bluffs where it would likely be noticeable. They are sandstone and sandy shales which do not slump readily. 
Deep-seated movements: This agency could produce. any of the results shown here in two ways: First, by dis­locations which extend to the surface from deeply buried structure; second, by folding or slight movements of deeper­structures without rupture but producing rupture in the suface beds. This latter would seem highly improbable­unless the character of the surface strata is considered. These clayey sandstones and sandy shales are so friable that. movements causing slight local tension or compression or flexure of the beds might result in just such structures as·. are seen. Furthermore, these faults and crushed zones are associated with gentle folds upon a large structural ter­race, and the possibility of their origin from deeper-seated causes can not be thoroughly comprehended without taking­
University of Texas Bulletin No. 1850. Plate XI 
Large fault on Pecan Creek. None of the beds checks across the fault. Another fault on the left not shown. All are faulted in the same direction. 

University of Texas Bulletin No. 1850. Plate XII 
East side of a fault zone above the Arlitt ranch-house on Pecan Creek. The west side of the fault zone, broken and crushed, is shown in the next plate. 

University of Texas Bulletin No. 1850. Plate XIII 
West side of fault block shown on previous plate. The beds shown in the pictures are leached. 

The Geology of Coke County 
this terrace and all its peculiarities and relationships into account. 
General Considerations: The terrace itself is broad, extending from near Robert Lee to Wilson Mountain, or beyond; a distance of about 12 miles in an air line. The surface indications of its western limit are stronger than of its eastern edge. So far as observed, faulted structures are confined to the eastern half of the structure, and are strongest near the center of the terrace. This localization of these peculiar structures has some considerable interest if the broader relations of the terrace itself are taken into account. For instance, a similar terrace having a known length of some fifteen to twenty miles at Sheffield, Texas, is described by Liddle in another bulletin.1The Sheffield
G 
terrace extends almost directly toward the Coke County ter­race (N 40°-60° E) is as wide; and, like the Coke County terrace, has its chief local minor structural features on the southeastern side. In addition .to this the Sheffield terrace is almost in line with the general axis of the Marathon structure as a whole, and is nearly in line with a very steep fold of the mountain type in Pennsylvanian sediments of the Marathon region. This Marathon fold disappears under the nearly level Comanchean sediments east of Mara­thon. The Marathon structure has been described by Ud­den,11 and further discussed by Liddle in the paper above referred to. In view of these facts, it is by no means im­possible that the Coke County terrace is a part of a gel'lerul structure extending from the Marathon region to Coke County. This structure may persist the whole distance either with local arches and intermediate saddles or without them. 
The details upon which this conclusion is based, aside from the general surface similarities already mentioned, are to be had in the comparison of three wells : the South­western Petroleum Syndicate Cain No. 1, locat~d aboyt four miles west of San Angelo; the Texas Elkhorn Oil Syn­
16Liddle, R. A., Univ. Texas Bull. 1847, pp. 9-16. 1920. 
11Udden, J. A., Univ. Texas Bull. 1753, pp. 56-57. 1918. 

University of Texas Bulletin 
dicate Richardson No. 1 in the southeast corner of Sterling County; and the Robert Lee Oil Company Stroud No. 1, near Robert Lee. We are indebted to Mr. H. H. Jones for samples and valuable data regarding these San Angelo and Sterling County wells. The data are as follows: 
The elevation of the Texas Elkhorn Oil Syndicate Rich­ardson No. 1 well is 2200 feet, and it is located near the southeast corner of Sterling County. The Southwestern Petroleum Syndicate's Cain No. 1 well has an elevation of 1890 feet, leaving the Richardson well 310 feet higher than the Cain well. The graphic logs are given on Plate 17. The distance of the Richardson well from the Cain well is approximately 22 miles in an air line and is in the d!rection of the dip. Over western Runnels, eastern Coke, and prob­ably eastern Tom Green counties, the dip is approximately 50 feet per mile to the northwest. 
If this condition continues from the Cain well to the Richardson well the same formations should be about 1100 feet lower in actual elevation than in the Cain well, or 1410 feet deeper in the well. As a matter of fact, the lower part of the log shows an actual elevation 463 feet higher in the Richardson well than in the Cain well. This conclusion is based upon three sets of data. 
First, the top of the known Bend formation as determined by the samples, was-204018 feet in the Cain well, and -1575 feet in the Richardson well, leaving the top of this forma­tion 465 feet lower in the Cain well than in the Richardson well. 
Second, the top of the formation determined by the drillers and some geologists to be the Smithwick shale, in the two wells was: Cain well, -1431 feet; Richardson wen; -985 feet, a difference of 446 feet in favor of the Richard­son well. 
Third, the top of a black limestone of considerable thick­ness recognized as identical in the two wells by the driller, was -2030 feet in the Cain well ·and -1550 feet in the Rich­
18The symbol "-" signifies below sea-level datum. 
The Geology of Coke County 
.ardson well, leaving a difference of elevation of 480 feet in. favor of the Richardson well. 
Averaging the difference in elevation of the three hori­zons in the two wells gives 463 feet. The greatest varia­tion of the levels of the horizons is at one extreme 17 feet higher and at the other 19 feet lower than the average. This is practically within the limit of error of determination by usual drilling, on one hand, and is certainly within the limits of variation in thickness of a set of formations 600 feet thick in a distance of 22 miles. 
Thus we are forced to concede that the basal part of the sections in these wells demonstrates an actual structure showing an elevation of 463 feet in the level of these beds in the southeast corner of Sterling County, when the con­tinuation of the dip should show an actual depression of 1100 feet for them in this locality. The position of the Richardson well would fall in the Coke County terrace, if continued, and the San Angelo well would not. This should be regarded as strong evidence of the continuation of the large sub-surface structure shown in Coke County at least as far as the south line of Sterling County. 
Regarding the correlation of the deeper rocks of Coke County, and the apparent changes which the formations undergo to the westward and southwestward from the Run­nels County region, the interpretation of the drill logs is necessary in order to reach any positive conclusions. 
The Westbrook well near Tennyson started in the Choza formation of the Clear Fork stage, The base of the Clear Fork and the top of the Wichita Stage appear to have been reached at 750 feet. The base of the Wichita is probably .somewhere between 2375 and 242.0 feet. Samples are not available and this point can not be determined with any de­gree of certainty. According to this record, the Vale for-: mation has a thickness of 153 feet, while the estimated thickness of the formation in Runnels County was 154 feet. 
The Choza formation in which the well started shows a thickness of 597 feet including the Bullwagon dolomite. The well began below the top of the formation as exposed 
University of Texas Bulletin 
on the Colorado River. The thickness in Runnels County and eastern Coke County is estimated at 626 feet.19 The thickness of the Clear Fork will be seen to check out almost exactly with the Runnels County section. 
The base of the Wichita in the Cain well is proably about 3000 feet below the surface. This can not be positively stated until the Fu'Sulinae of the central Texas region are known. It certainly should be between 2800 and 3000 feet; probably much nearer the latter than the former figure. If this is the case, the whole of the Strawn and Canyon is. wanting here, and, if the driller's diagnosis of the top of the Smithwick shales is a correct one, at 3321 feet, the Cisco is reduced in thickness from 800 feet on the Colorado River in Coleman County to about 321 feet in the Cain well, or at the very most, 525 feet. 
In comparing the upper parts of the Cain and Westbrook wells, it is difficult to fix definite limits for the Wichita­Clear Fork and the Clear Fork-Double Mountain stages in the Cain well. 
From the nature of the sediments it would seem that the 
base of the San Angelo beds and top of the Clear Fork beds. 
was at 447 feet, at the bottom of the sandstone members. 
Comparison of the logs shows that the Clear Fork has ap­
parently thickened at the expense of the Wichita beds, 
whether by replacement of the upper limestones by shales, 
or otherwise, can not be said. The top of the Clear Fork 
is consequently at 447 feet below the surface, and its base 
-upon purely lithological grounds-seems to be at 139(). 
feet. This gives it a thickness of 948 feet, showing a slight. 
thickening to the southward, in the Cain well. 
If 3000 feet be considered the base of the Wichita, the 
formation has a thickness of 1610 feet, or 80 feet less than. 
on the Colorado River, all but a little over 200 feet of which 
is limestone. It should be noted that there are two sand­
19The statement on page 49 that the "thickness of the whole forma­tion is 870 feet," should read "thickness of the Clear Fork Stage­is 870 (or 880) feet on the Colorado River." Univ. Texas Bull. 1816~ 1919. 
The Geology of Coke County 
stones near the top of the Wichita. The Cisco below the Wichita is largely shales with limestone streaks. The coal streak may be near the base of the Cisco in the Cain, West­brook well, if the underlying bed3 belong to the Smithwick. The identification of these shales from logs of tests far sep­arated, and from samples frequently leaveil much to he de­sired. A sample of the limestone at 38t)2 feet ·was studied by Waite who pronounced it to be Marble Falls limestone. 
In the Richardson well there are 80 feet of sandstone and conglomerate at the top, apparently belonging to the San Angelo formation. However, it is not impossible that much of the basal San Angelo formation is here represented by shales and occasional thin limestones. 
If we conclude that only the 80 feet belong to the San Angelo formation, then it follows that the Clear Fork has thickened to 1345 feet, the base being at 1425 feet is much more probable that the base is as high as 1170 feet. The top of the Wichita in this well seems to be at the depth of 1425 feet, and its base may be regarded tentatively as at 2852 feet, though it may be below that point. This gives a thickness of 1427 feet for the Wichita, a continued thinning over the Cain well, of 83 feet, or 163 feet over the surface section in Runnels and Coleman counties. 
A marked increase in the number of sandstones in the upper and lower Wichita is of interest, there being four here as compared with two in the upper Wichita of the Cain well. These four sandstones have an aggregate thick­ness of 158 feet. In the lower part there are three sands with an aggregate thickness of 36 feet, while nearly the whole limestone of the Wichita beds is reported as sandy. The base of the Cisco may be 3185 feet, or a thickness of 333 feet. Whether or not the beds below this all belong to the Smithwick shales or to the Cisco ir uncertain. The known Bend occurs at 3735 feet and continues to the bot­tom of the well. Several oil horizons seem to have been struck in the lower part of the well. 
The limestones of the Wichita Stage show a marked in­
crease in thickness in the Sterling County well, compared 
University of Texas Bulletin 
with the Cain well and the shales are thinner and more cal­careous, according to the driller, H. H. Jones, who had charge of the drilling of the Cain well and the deeper part of the Richardson well. 
One striking feature of the Richardson well is its sandy nature, according to the log. This may indicate extensive sandstones farther southwest, but hardly speaks well for shales there, since it would seem that there was sufficient current present at the time of deposition to sort out the finer material and carry it away. We have seen no samples of this sandy limestone. 
While the shales decrease in the lower part of this well they increase very markedly in the upper part, and some of the limestones thin out or become thinner than in the Cain well. In the Stroud well the base of the San Angelo beds is found at 560 feet. The top of the Merkel dolomite, he1·e an anhydrite, is probably at 650 feet below the surface. The heavy limestone which sets in at a depth of 1202 may be the top of the Wichita, or the top may begin with the limestone at 1680 feet. Judging by the Westbrook well, 1680 feet may be considered as approximately the top of the Wichita. This gives the Bullwagon dolomite here a thick­ness of 217 feet, and the Vale formation thickens from 153 feet in the Westbrook well to 261 feet in the Stroud well, which is a material thickening of the lower Clear Fork beds. 
Beginning the Wichita at 1680 feet, its base may be con­sidered roughly at 2986 feet. It may be somewhat above or below this point. This would leave the thickness of the Wichita stage at 1306 feet, a thinning of more than 380 feet over the surface section in Coleman and Runnels coun­ties. This thinning is accompanied by a disappearance of nearly all the shales, and an introduction of sandstone beds in the lower part. The well probably ends near the base.of the Cisco. The Cisco will probably be as thin here as in the Cain and Richardson wells. 
In view of these circumstances it seems reasonable to in­terpret the Coke County faults in the light of their position 
The Geology of Coke County 
upon this larger structure. As is shown in the section along the Colorado River, the structure beneath the Double Mountain series of rocks appears to be very much greater than that revealed in the surface strata. Whether this structure is due more to faulting or to folding is unknown. As has been stated, the character of the sediments involved in the faults and crushed zones is such that in case of slight disturbance by either folding or faulting, just such struc­tures would likely be formed as actually occur. For this reason the assumption of faulting is unnecessary. How­ever, the oil filling the sandstones of fossil delta channels built in the margin of a sea of highly concentrated waters can but doubtfully be regarded as indigenous and would indicate that there has been sufficient faulting of underly­ing beds to permit its escape into surface rocks. 
OIL AND GAS POSSIBILITIES 
Coke County is unique in Central Texas in having good showings of oil in surface sandstones. Some of these sandstones were the sands of delta channels on the margin of a shallo.w Permian sea. The presence of salt seeps and · of gypsum and anhydrite replacing dolomites, as shown by drill cuttings, indicates that the waters of this shallow sea were very concentrated. It is quite doubtful if oil ac­cumulations would occur under such circumstances on ac­count of the scarcity of marine life in such waters. Indica­tions of fossil remains in these sediments are very rare. Moreover, it is yet to be demonstrated that commercial oil accumulations have been found which were indigenous to this type of red beds sediments. Several oil fields have been found beneath or ·in the red beds. .Ohern20 citeR a list of such. cases, and a few more have since come to light. . So far as we are aware, all of the known oil in cor!1­
mercial quantities in the red beds is either in a region of 
known faults, or overlies highly-inclined bituminous b('dR 
20 Qhern. D. W., A Contribution to the Stratigraphy of the Red 
Beas. Bull. Amer. Assn. Petr. Geol., II, p. 114. 1918. 

University of Texas Bulletin 
beneath an unconformity between the Permian and Pennsyl­vanian rocks from which the oil might have migrated, as is the case in the western Oklahoma fields around the Wichita and Arbuckle Mountains. Regions near the mar­gin of the red beds and remote from gypsum and salt de­posits are excepted. 
If these premises be true, it is unlikely that the Coke County oil showings originated in the beds in which they are found, unless they may possibly have been formed in relatively small lagoons of fresher water. 
If the oil did not originate in the beds where it now exists it could only reach its present position in ·one of two ways: First, by lateral migration; and second, by vertical migra­tion. 
It is difficult to see how the oil could be formed in this horizon at any other point any better than where it is found. Such concentrated waters are too barren of life to warrant this conclusion. It could be argued that it may have come a long distance from outside of an embayment where the waters were less concentrated. No such sea is known with­in reasonable distance. The land lay to the east of this region. Almost certainly, the Mount Margaret conglom­erate is very near the debouchure of a river of considerable size, since the coarse conglomerate occupies an area 30 miles across. This condition clearly precludes a westward migration. Since the oil showings are about equally pro­fuse in both the San Angelo and the lower Greer forma­tions, separated by considerable thickness of rock, it might have originated in either, but, if anything, the Greer is a less likely source of it than the San Angelo formation. These beds wherever found are ch~racterized by their very extensive gypsum and salt deposits. 
The only other possible source· that occurs to us is a deep-seated one. It may have been formed in rocks far below the surface and have reached its present position by rising through faults. If we turn our attention to the structure of the rocks of this region a few things are vis­ible which throw some light on the problem. One of these 
The Geology of Coke County 
is that, as far known, the oil is found on or near the east side of the terrace in positions coincident with the faulted surface beds of their eastward extension. Another point to be considered is that in the Locke NQ. 1 well at Robert Lee the driller reported all the rocks encountered as being in normal position and condition. The same driller re­ported all hard rocks encountered in the Stroud No. 1 well as broken up and not in normal position for a depth of nearly a thousand feet. If this is true, there is some additional evidence of faulting in the rock below the Double Mountain beds. Such a condition could account for the presence of the oil as it is found at the surface. So far as has been determined the larger faults in the surface beds, and for that matter the more pronounced structures as seen at the surface, are in the Pecan Creek region, where oil showings occur. They also occur near Robert Lee. 
In the light of available data it seems most reasonable at present to ascribe the origin of the surface oils in Coke County to deep-seated beds. 
An inspection of the section along the Colorado River shows the east side of a sub-surface structure, and indicates that much of the top of the buried structure was removed by erosion before the San Angelo and Greer beds were de­posited, and further indicates that some 500 or more feet of the structure may have been carried away, bringing any possible oil-bearing bed that much closer to the surface. In this connection, the Texas Elkhorn Oil Syndicate's Rich­ardson No. 1 test in southeast Sterling County is of especial interest since it throws light upon the subject, as has al­ready been pointed out. The difference in elevation of the heavy limestone penetrated in the Stroud No. 1 test and the Lo~ke well, where it was not drilled into, is about 150 feet. Whether this is due to folding or faulting cannot be said, and both possibilities are indicated on the accompany­
ing chart. The driller's report of conditions encountered 
in the Stroud well would favor the hypothesis that the beds 
are faulted. Both faulting and folding may have occurred. 
Structures not on the Terrace: The structures in the 
University of Texas Bulletin 
eastern half or third of Coke County are low gentle folds and noses closely related to similar structures described from Runnels County. These have not been worked out in detail, but are suitable structures for oil accumulation should proper sub-surface conditions exist for producing oil. The region has not been sufficiently exploited to de­termine the point. Four wells have been drilled or are· drilling in this part of Coke County but none is of sufficient depth at this writing to form a true test of the presence or absence of these conditions. 
In the eastern part of Coke County occur other folds formed by gently dips which are quite similar to those oc­curring in Runnels County and the region east and north­east. They are rarely conspicuous. . Some of the struc­ture::i of Runnels County were described in the bulletin on Runnels County.21 
The Westbrook test at Tennyson apparently entered the Arroyo formation at 690 feet and the base of the Lueders at 117 4 feet. According to these figures, if the formations maintain their thickness westw.ard, the top of the Cisco in the neighborhood of Tennyson should be reached at about 2350 feet, and the base of the Canyon at about 3300 feet. Just how much of the Canyon may be present is a question, since in some places in this western region there appears to be nothing between the Cisco and the Bend. Whatever tests are made here should be carried through the Bend to the Ellenburger and samples and logs of all the beds pen­etrated carefully kept and studied. 
The main difficulty likely to be encountered in this part of the county is the lack of extensive sandstone or other porous beds to serve as reservoirs for the oil. However, some sandstones were encountered in the Stroud well and more may be encountered if the well should be drilled deeper. Very little sandy material was encountered in the Westbrook well, down to a depth of 3000 feet, as will be noted in the log. 
21 Univ. Texas Bull. 1816, pp. 55-59. 1919. 
University of Texas Bulletin No. 1850. 	Plate XIV 
A. 	Bluff on South Pecan Creek showing the effect of solution of gypsum beds from between clay and soft sandstone beds. The sandstone below the gypsum zone is in normal condition. 
B. Oil showing in highly cross-bedded sandstone in the bed of Mountain Creek just east of Robert Lee. 

University of Texas Bulletin No. 1850. Plate XV 
Map showing hypothetical extension of Marathon Fold. Explanation on map. 
DOUBLE MOUNTAIN STAGE 
GREER l FOflMATIQ N -~ ­
;;!
~ ....... . .. ] .. 
,,, ..,: ,:, ,:ir:,1 u111111111111111m1111111111111111111i111m~1HH1111111111 ~ 
ilr!H1mmm111ITT11mmmi11111a:::m11111111111m111m111111lm1m11111111!m111111m1111111111rn11....t...jll.... It i1t . ~ 
0
.... 
DOUBLE MOUNTAIN STAGE 
---~­
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(1) 
SAN ANGELO FORMATION RE'E'R ? FO~MATION ~ 
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--:::l CLEAR FORK -'----y-DOUBLE MOUNTAIN STAGE . . ­
t
l C:HOZA FORMATION SAN ANGELO r ORMATION . 
~----·---...... 
00 
01 
0 
CLEAR FORK STAGE 
UPPER CHOZA f"ORMAT10N 
mmi~m~1~m111111m11111111111m11111111111111111111111111111111111111111111m11111111111111111111111m111111111111111111111111111111111111111111111 111111111 1 
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· 5cole (1) 
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·Vertical section of surface exposures of the rocks of the Colorado Rinr section in Coke County. ..... 


INDEX 

Alva, Oklahoma. . . . . . . . . . . . . . . . . . 51 Arbuckle Mountains .... , . . . . . . . . . . 78 Austin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Blackwell .. ............ . ....... . ..9, 22 Balcones Fault Scarp . . . . . . . . . . . . . . 9 Bend Formation . . . . . . . . . . . . . . . . . . . 72 Ben Ficklin . . . . . . . . . . . . . . . . . . . . . . . 13 Blowout Mountain Sandstone . . . . . . . 52 Blowouts . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Boese, Emil . . .. . . ...... .. ....49, 50, 52 Brazos River . .. .. ... .......... ....11, 17 Bronte .........16, 21, 25, 39, 49, 61, 65 Bullnose Mound . . . . . . . . . . . . . . . . . . . 18 Bullwagon Dolomite . . . . . . . . . . . . . . . . 76 Caballos Formation ....... . ... . , . 40, 53 Callahan Divide .....7, 11, 12, 22, 59, 61 Canyon Formation. . ............74, 80 
Caprina. . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Cedar Mountain ........13, 16, 23, 64, 67 Choza Formation ......17, 18, 49, 61, 73 Cisco Formation ................74-76, 80 Clear Fork Beds ....... . .. .. . ...... . 
.... . . 14, 15, 18, 19, 21, 49, 51, 74, 76 Clay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Coleman County .............. . 65, 74-76 Cole Mountains ...... ............11, 56 Comanchean . ......... . ... . 13, 53, 61, 65 Concho Country . . . . . . . . . . . . . . . . . . . 13 Consolidation of Sediments. . . . . . . . . . 70 Correlation. . . . . . . . . . . . . . . . . . . . . . . . 49 Cow Creek .................... .7, 13, 24 Cummins, W. F .............3, 14, 29, 51 Deer-seated Movements . . . . . . . . . . . . . 70 Del Rio ......·..... ................. 9 Dockum Beds . . . . . . . . . . . . . . . . . . . . . . 39 Double Mountain Beds............ . . 
..... .. ....14-16, 29, 38, 50-52, 74, 77 Dumble, E.T..................14, 15, 21 Edith. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Edwards Plateau ..7, 9, 12, 29, 53, 61 , 64 Ellenburger Formation. . . . . . . . . . . . 80 Eskota Gypsum .. . . . ...... . .......29, 53 Escue, Charles . . . . . . . . . . . . . . . . . . . . . 7 Exogyra texana ... . ....39, 54, 55, 57, 59 Faults. . ......... , ................67-77 Foraminifera. ... . .... .. ......... . 56, 6') 
l 'ort Charlhourne. . . . . . . . . . . . . . . . . fi{ 
Fossil Creeks . . . . . . . . . . . . • . • . . . . . . . . 28 
Fossil delta . . . . . . . . . . . . . . . . . . . . . . . . 28 
Fusulina. . . . . . . . . . . . • . . . . . . . . . . . . 7tl 
Gaptank Formation ........ , ......50-52 

Gas................... ........... 65-80 

Gasconade Creek ......•... , . . . . . . . . 8 
Geography. . .............. , . . . . . . . . 7 

Glass Mountains ........... . .....50, 51 

Glass sand . . . . . . . . . . . . . . . . . . . . . . . . 61 
Gould, C. N .................. . .. 51, 53 

Gravel. . . . . . . . . . . . . . . . . . . . . . . . . . . 64 
Greer Formation . , ............ ... . 

16, 22, 29, 30, 39, 51-53, 58, 61, 78, 79 
Grubbs Canyon ....... ...........58, 63 

Gryphaea .......... ......39, 54, 55, 59 

Gypsum ........28, 32, 37, 38, 51, 52, 63 

Halbert Place ............... .....26, 27 

Hayrick Mountain . . . . . . . . . . . . . . . . . 11 Heifer Creek . . . . . . . . . . . . . . . . . . . . . . 8 H ess Formation . ... .. ............50, 51 Hester Place . . . . . . . . . . . . . . . . . . . . . . 25 Humlong Ranch . . . ....... . . . ....21, 64 Indian Creek. . . . . . . • . . . . . . . . . . . . . . 7 Irion County. . . . . . . • . . . . . . . . . . . . . . 13 Jones, H. H.... , ......... ....... .i2, 76 Jura-Trias. . . . . . . . . . . . . . . . . . . . . . . . 14 Kansas. . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Kickapoo Creek. . . .. . ....... . .... . Kickapoo Mountains ... .11, 21, 29, 54, 64 Lenox. . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Leonard Formation ...... .... ..... 49-51 Lerch, Dr. Otto .. ...... ....... . . . 13, 14 Liddle, Ralph A. . . . . . . . . . . . . . . . . . . . il Lime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Limestone. . . . . . . . . . . . . . . . . . . . . . . . . 62 Live Oak Creek ................ 7, 21, 64 Lueders Formation . . . . . . . . 80 Ma rathon. . . .... .... .......40, 51-53, 71 Marathon Fold. . . . . . . . . . . . . . . . . . . . . 71 Marble Falls Limestone . . . . . . . . . . . . 15 
Marcou, Jules. . . . . . . . . . . . . . . . . . . . 14 Meadow Creek . . . . . . . . . . . . . . . . . . . . . 7 Merkel Dolomite ..... .... . . . 16-18, 49 76 Messbox Creek. . . . . . . . . . . . . . . . . . . . . 7 Millikin Mountain . . . • . . . . . . . . . . . . . 36 Monadnock. . ............... , . . . . . . 11 Moran................. , . . . . . . . . . . 52 Moro Mountain. . . . . . . . . . . . . . . . . . . . 11 Mountain Creek . . ..............7, 26, 67 Mount Margaret....14, 19, 21, 40, ii3, 78 Mount Ord Range . . . . . . . . . . . . . . . . . 50 Mount "Q" . . . . . . . . . . . . . . . . . . . . . . . . 55 Mule Creek .......... , . . . . . . . . . . . . . 7 Neva Limestone . . . . . . . . . . . . . . . 52 Nipple Peak ...... ..... , . . . . . . . . . . . 40 North Concho River . . . . . . . . . . . . . . . . 13 North P ecan Creek.. .. .... . ...34, 66 
Ohern, D. W. . . . . . . . . . . . . . . . . . . . . . . 1 1 Oil. ..................... . ........65-80 Oklahoma...... ............16, 51, 52, 78 0 'Ylphalotrochus. . . . . . . . . . . 52 Origin of structures . . . . . . . . . . . . . . . . 69 Paint Creek ... . .. ....... ........ ..8, 67 Panhandle...... ............. . . 16, iil-53 Panther Gap .......... . . 39, 40. 64, 66, 67 Pecan Creek ..........8, 35, 36, 65-77, 79 Peoten. . . . . . . . . . . . . . . . . . . . . . . ... . . . 56 Pennsylvanian. . . . . . . . . . . . . . . . . . . . . . 50 Permian. . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Perrinites. . . . . . . . . . . . . . . . . . . . . . . . . . 49 Perrinites vidriensis . . . . . . . . . . . . . . . . 50 Physiography. . . . . . . . . . . . . . . . . . . . . . i Pleistocene....................16, 59, 69 Quartermaster Formation ( ? ) 16. 39. 52, 53 
Radiolites. . . . . . . . . . . . . . . . . . . . . . . . . . 57 Recent......... . .. ...... ..... . ..16, 60 Red River. .... ... .. ...... .. . . ....29, 52 Road Metal. . . . . . . . . . . . . . . . . . . . . . . 64 Robert Lee....... ................ . 
..16, 18, 27' 28, 30, 61, 63, 66, 67. 79 Robert Lee section near ........25, 26, 64 Roui:<h Creek ..... . ......7, 8, 33, 36, 61 
Index 
Runnels County . .... .. .... . . .. .. .. . 
......11, 17. 19, 21, 40, 49, 66-76, 80 Salt Creek. . . . . . . . . . . . . . . . . . . . . . . . . 8 San Angelo ....... . 14, 49, 50, 71, 73, 74 San Angelo Beds .... . .. . .. .. . 13, 16, 
20-23, 28-30, 40, 51, 62, 61, 67, 76-79 San Antonio. . · . . . . . . . . . . . . . . . . . . . . 9 Sand.. ............... ........... 60, 61 Sand Creek. . . . . . . . . . . . . . • . . . . . . . . 60 Saul, John Place . . . . . . . . . . . . . . . . . . 33 Schwagerina. . .... ... ... ... .....51, 52 Sections. geologic : 
Cedar Mountain . . . . . . . . . . . . . . . . . 23 Cedar Mountain to Robert Lee. . . . . 23 Clear Fork, upper . . . . . . . . . . . . . . . 18 Cow Creek, east of. . . .. . . .. . .. . . 23 
Cow Creew, west .,r.... .. ...... .. 24 
Hester Place. . . . . . . . . . . . . . . . . . . 25 Kickapoo Mountain, Permian . . . . 21 
Kickapoo Mountains Comanehean . 64 
Merkel Dolomite . . . . . . . . . . . . . . . . . 18 North 200 E Millikin Mountain.. 36 Mount Margaret •... ..... ......19, 53 Pecan Creek ... . .. . .... . .. ... ..36, 36 Robert Lee, below .. ............25, 26 Robert Lee, west of. . . .. . . .. . . .. . 30 Rough Creek. . . . . . . . . . . . . . . . . . . . 33 Saul, John, Place. . .. ...... . . . . . .. 33 Seato~ Keiths Bluff . . 30, 36, ref. 63, 64 
South Pecan Creek. . ......... . 33, 31 

Sterling City Auto Road. . . . . . . . . . 30 
Wild Cat Creek, lower .. .. . .....30, 31 
Wilson Mountain . . . . . . . . . . . . . . . . . 38 Shackleford County. . . . . . . . . . . . . . . . 62 
Sheffield. • . . . . . . . . . . . . . . . . . . . . . . . . . 70 Silver Creek. . . . • . . . . . . . . . . • . . . . . . . 7 Sinks.. ....... .... .......... ....... 12 Smithwick. . ......................74, 75 Solution. . . . . . . . . . . . . . . . . . . . . . . . . . . 69 South Pecan Creek ... . 33, 34, 38, 66, 67 Staked Plains. . . .. .. .... . .. . .... ..9, 11 Stepp Mountain . . ... . .. . ......11, 39, 60 Sterling County. . .. .• ... ... .. . ...72-75 Structure. . .. .......•.• ....... .... 65-67 Table Mountain. . . . . • . . . • . . . . . . . . . . 11 Teneyck Ford. . . . . . . . . • . . . . . .. . .. . 18 Tennyson. . . .. . ...... . . . .. ...64, 65, 80 Tertiary................... ..16, 69, 69 Tom Green County. . . .•... ..13, 64, 72 Triassic. . .. . .... .. . ... . . ........16, 39 Udden, J. A . ....................50, 71 
Vale Formation. . . . . . . . . . . . . . . . . . . 76 Waite, V. V. .. .. . .. .. .. .. . .. .. .. . 76 Wells, oil 
Cain No. 1...... ..... ....44, 71-75, 76 
Richardson No. I . .... . .... . . 71-76, 79 
Stroud No. 1. .. .............. 72-76, 79 

Westbrook No. 1..........42, 73-76, 80 

UNIVERSITY OF TEXAS BUREAU OF ECONOMIC GEOLOGY AND TECHNOLOGY 
BULLETIN 1850, PLATE 1 
J. A. UDDEN, DIRECT OR 

Z 
-I 
T 0 M 
~===-~.....;3'====~---G~~~files 



GEOLOGIC MAP OF COKE COUNTY, TEXAS 
J. W. BEEDE AND W. P. BENTLEY 
1920 . 
LEGEND 
~ ~; Recent river gravel, silt ~ ~
~ 1"'1'°;and sand 
--<"' 
G lr1"" 
Tertiary or early Pleis-1~ ~ tocene conglomerate orj -?;; gravel. j-< 
G l~z
Comanchean, undiffer­entiated: Limestone, Im~ 
marls and sandstones. 
I~ 
..) 

Quartermasterf?)conglom­erate,sandstone,and some shale. 
GJ 
0 
~ 
Greer formation: Sand-m 
stone, shale1 and thick ~ 
gypsum bea. c 

~~ 
)> 
"' 
s::
I z 

>z 
San Angelo formation: 
Conglomerates, sand­
stones and gypsum 
beds. j 

-!
Choza formation:Shales, }§with thin dolomites and ~I thin gypsum beds. ~j 
University -0f Texas Bulletin No. 1860 Plate XVII