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 PubU*^o^lf»iT^lir{SfMe88, Austin. , : *: 
 
B57-1022-2500 
 
 University of Texas Bulletin 
 
 No. 2239: October 15, 1922 
 
 The Producing Horizon in the 
 Rios Well in Caldwell County 
 
 BY 
 E. H. SELLABDS 
 
 Bureau of Kconomic Geology and Technology 
 
 Division of Economic Geology 
 
 J. A. Uaden, Director of the Bureau and Head! of the Division 
 
 Fll BUSHED BY THE TJNIVEBSITT FOUR TIMES A MONTH, AND ENTERED AS 
 
 SECOND-CLASS MATTER AT THE POSTOFFICE AT AUSTIN, 
 
 TEXAS, 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 govern- 
 ment. 
 
 Sam Houston. 
 
 Cultivated mind is the guardian 
 genius of democracy, . . It is the 
 only dictator that freemen acknovrl- 
 edge and the only security that free- 
 men desire. 
 
 Mirabeau B. Lamar. 
 
> CONTENTS 
 
 Page 
 
 Introduction , 5 
 
 Surface Formations 5 
 
 Regional Structural Features 6 
 
 Zone of Faulting 7 
 
 Local Structural Conditions 7 
 
 Thickness of Formations 7 
 
 Available Literature and Geologic Maps 8 
 
 Oil Production 8 
 
 The Producing Horizon 9 
 
 Description of Samples from Cartwright 2, by J. A. Udden 
 
 and P. T. Seashore 10 
 
 Note on Cartwright 2, by J. A. Udden 17 
 
 The Rios Well 18 
 
 Description of Samples from' the Rios Well, by E. H. Sellards 
 
 and P. T. Seashore 21 
 
 Description of Samples from Cartwright 3, by E. H. Sellards 
 
 and P. T. Seashore 23 
 
 Production from the Lower Cretaceous in Texas 27 
 
 Well Logs 27 
 
 Log of Cartwright 1 2S 
 
 Interpretation 29 
 
 Log of Cartwright 2 30 
 
 Interpretation 31 
 
 Log of Cartwright 3 32 
 
 Interpretation of Cartwright 3 and Cartwright 4 33 
 
 Log of Rios 1 ■ 33 
 
 Interpretation 34 
 
 Log of C. A. Schawe 34 
 
 Description of Samples from the Schawe Well, By J. A. 
 
 Interpretation 36; 
 
 Udden 35. 
 
 Log of Thompson 1 3g 
 
 The Ghormley Well in Guadalupe County 38 
 
 ILLUSTRATIONS 
 
 Figure 1. Sketch showing correlation of the Rios and Cart- 
 wright Wells 19 
 
Cornell University 
 Library 
 
 ^ 
 
 The original of this book is in 
 the Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924004034587 
 
THE PRODUCING HORIZON IN THE RIOS WELL IN 
 CALDWELL COUNTY 
 
 BY E. H. SELLAEDS 
 
 Caldwell County lies within the Gulf Coastal Plain of Texas, 
 near its west margin. The Baleones escarpment, which forms 
 the boundary line between the Coastal Plains and the Edwards 
 Plateau, passes west of this county, but within five or six miles 
 of the county line. The formations at the surface in Caldwell 
 County are those of the Upper Cretaceous and the Lower Ter- 
 tiary. The Upper Cretaceous formations include the Taylor 
 and Navarro, while of the Tertiary formations, there are present 
 the Midway and the Wilcox. To what extent other Eocene 
 formations, including the Carrizo and Mt. Selman, are developed 
 in this county has not been determined. 
 
 Except where concealed by terrace materials, the Navarro 
 and Taylor formations of the Upper Cretaceous lie at the surface 
 over a narrow belt at the west margin of the county. This 
 Cretaceous belt is widest at the south side of the county and 
 narrows to the north margin of the county Vhere its width 
 scarcely exceeds two miles, and where the Navarro formation 
 only is present. The town of Maxwell lies within the Cretaceous, 
 although near its east margin. 
 
 Next east o-f the Cretaceous is the Midway formation, which 
 occupies a narrow belt passing through the county from north- 
 northeast to south-sotitheast. Cooperative work between the 
 United States Geological Survey and the 'Bureau of Economic 
 Geology of the University has resulted in identifying several 
 Midway localities within this area. Among these localities is 
 one four and six-tenths miles slightly south of west of Lockhart 
 where clays are exposed containing a Midway fauna. Other sim- 
 ilar localities are found on the Lockhart- Austin road, one and 
 one-half andi two miles north of Lockhart. From a well about 
 eleven miles west of south of Lockhart and about two miles 
 southwest of Joliet, Midway fossils were obtained. This well, 
 which starts in the Wilcox formation, was drilled to the depth 
 of 340 feet. Shell bearing clays and shales are reported in the 
 
 Manuscript submitted in September; issued November, 1922. 
 
6 University of Texas Bulletin 
 
 well beginning at sixty feet from the surface and extending to 
 the full depth of the well. The Midway fossils obtained were 
 from the dump, their position in the well being unknown except 
 that certain of them are stated to have come from 320 feet. 
 These localities indicate that the Midway is found a few miles 
 west of Lockhart and probably extends somewhat east of Lock- 
 hart. The trend of the outcropping belt of the formation is 
 north-northeast to south-southwest. Next east of the Midway is 
 the Wilcox formation. 
 
 In traveling south from Lockhart, on the Lockhart-Luling 
 road, exposures representing the Wilcox are first seen on Clear 
 Fork Creek and its tributaries about four miles south of Lock- 
 hart. On the San Marcos Eiver six miles northwest of Luling 
 and near the Cartwright wells is an exposure consisting of 
 very sandy micaceous clays including several strata of cone-in- 
 cone concretionary layers. This exposure is referred provi- 
 sionally to the Wilcox. The eastern margin of the Wilcox has 
 not been determined, but the formation may be expected to have 
 a greater width Jhan the Midway and to pass through the county 
 from north-northeast to south-southwest. It is probable that 
 formations later than the Wilcox come into the section before 
 reaching the east county line. Sands probably representing the 
 Carrizo formation are seen near Ivy, in the southeastern part of 
 the county. 
 
 Regional Structural Features. The regional dip in Caldwell 
 County is in a southeasterly direction, so that, with the excep- 
 tion of any reversals in dips that may occur, successively younger 
 formations come into the section as one travels to the east or 
 southeast. The average rate of dip in the formations across the 
 full width of this county has not been determined. It is known, 
 however, that the Austin formation, which is found at the sur- 
 face in and near San Marcos, is encountered in the Cartwright 
 and Thompson wells at depths varying from 1742 to 1835 feet. 
 The Austin exposures at San Marcos are at an elevation approx- 
 imating 600 feet above sea, while the elevation of the Cart- 
 wright wells, as indicated by the topography map, is possible 
 150 feet lower. Taking this difference in surface elevation into 
 consideration, this record indicates that the Austin drops to a 
 
The Producing Horizon in the Bios Well 7 
 
 lower level across this interval at a rate approximating 100 
 feet per mile. It is probable that this change in level comes 
 about through faults as well as through dips. 
 
 Zone of FauUinff. The Balcones Escarpment seen at San 
 Marcos marks the west margin of the Balcones Fault Zone. 
 Faulting in this zone is particularly heavy in the vicinity of 
 San Marcos, so much so that the Austin formation, which has 
 a thickness of several hundred feet, occupies in this area no 
 more than a very limited surface exposure, and in places is 
 almost entirely faulted oiat of the section. The Balcones 
 Zone of faulting occupies a considerable width and includes 
 most if not all of Caldwell County. To what extent, however, 
 faulting is developed in this county, can be determined only 
 by careful detailed investigation. 
 
 Local Structural Conditions. In many of the faults of the 
 Balcones Fault Zone, including the large fault, which is respon- 
 sible for the Balcones Escarpment, the downthrow is to the 
 southeast. However, within this fault zone are occasional faults 
 in which the downthrow is in the opposite direction, that is, 
 to the northwest. One of these faults with downthrow to the 
 northwest is seen in an exposure on the left bank of the San 
 Marcos River, six miles northwest of Luling, and near the 
 Cartwfight wells. The fault in this place trends in a north- 
 easterly direction and the fault plane dips steeply to the north- 
 west. The faulting in this immediate locality may be somewhat 
 complicated, but that at least one fault occurs having downthrow 
 to the northwest is indicated by the "drag." 
 
 Thickness of Formations. The deep well drilled at Maxwell, 
 starting • probably in the Navarro formation, apparently pene- 
 trates all of the underlying Cretaceous. In this well white 
 rock, presumably the Austin, is recorded from 760 to 1036 feet, 
 or through an interval of 267 feet. "Gumbo," probably rep- 
 resenting the Eagleford formation, is found from 1036 to 1071 
 feet. The several lower Cretaceous formations are scarcely 
 separable, the one from the other, in the well log. However, the 
 Lower Cretaceous, as a whole, apparently extends from 1071 
 to about 3405 feet, indicating a total thickness of the Lower 
 
8 University of Texas Bulletin 
 
 Cretaceous at the locality of 2334 feet. Below the Cretaceoas 
 at 3415 feet, are found rocks of undetermined age, but believed 
 on the authority of Dr. J. A. Udden, who examined samples 
 through this interval, to be older than the Cretaceous. 
 
 A measurement of the full thickness of the Cretaceous above 
 the Austin in this county has not been obtained. However, 
 a shallow well two miles southwest of Joliet, located on the 
 Mercer farm, apparently terminated in the Midway, as indi- 
 cated by the fossils on the dump, at a depth of 340 feet. The 
 Rios well, not more than two miles to the southwest of this 
 shallow well, entered the Austin at 1635 feet. These records 
 indicate for the Cretaceous, above the Austin in this county, a 
 total thickness of approximately 1350 feet, or less. The thick- 
 ness of the Midway and Wilcox and other Eocene formations 
 in this eastern part of the county, has not been determined. 
 
 Available Literature amd Geologic Maps. The geologic litera- 
 ture on Caldwell County is limited. The Austin quadrangle 
 mapped by the United States Geological Survey includes a 
 small part of the northwest corner of the county, and the map 
 of that quadrangle indicates the distribution of the late Cre- 
 taceous and early Tertiary formations in that area. The Geo- 
 logic map which accompanies Bulletin 44 of the University of 
 Texas indicates approximately the Cretaoeous ,and Tertiary 
 areas of the county. The investigation now in progress in 
 cooperation between the United States Geological Survey and 
 the Bureau of Economic Geology and Technology of the Univer- 
 sity of Texas will afford the data for a publication to be issued 
 when the investigation has been completed, relating to the Mid- 
 way formation of this and adjoining counties. 
 
 Oil Production. One well producing oil in this county. has 
 recently been obtained. This well, which is owned by the United 
 North and South Oil Company, is located on the Rios farm 
 about six and one-half miles northwest of Luling, and about 
 one and one-half miles from the San Marcos River. The well 
 was drilled in about August 10, and is flowing by heads and 
 making some water with the oil. The gravity of the oil is 
 reported as being about 28-B. 
 
The Producing Horizon im the Eios Well 9 
 
 Production in this well is, with little doubt, associated with 
 'the fault already referred to as being seen near the Cartwright 
 wells on the San Miarcos River. Faults with downthrow to 
 the northwest bring about conditions favorable to production 
 for wells located near but east of the fault line. On the other 
 hand, faults with downthrow to the southeast, which are much 
 more common than those with the downthrow to the northwest, 
 do not necessarily influence production. The explanation is 
 probably found in the fact that since the regional dip is to 
 the southeast a fault with downthrow in that direction merely 
 accentuates the dip, while a fault with downthrow in the oppo- 
 site direction, that is, to the northwest, has the effect, by reason 
 of the "drag," incident to faulting, of reversing the dip. The 
 more or less complete filling of the fault plane with secondarily 
 accumulated materials may likewise assist iii forming a trap 
 for accumulation of oil. Oil pools controlled by faults of this 
 kind are likely to extend, if at all, with the trend of faults. 
 
 The Producing Horizon 
 
 In a press bulletin issued by the Bureau of Economic Geol- 
 ogy and Technology of the University of Texas, August, 1922, 
 the writer expressed the tentative conclusion that the pro- 
 ducing horizon in the Rios well in Caldwell County, known 
 as the Luling well, is probably from the Georgetown-Edwards 
 series of limestones of the Lower Cretaceous. In view of the 
 general interest as to the producing horizon in this well, it 
 seems worth while to give more fully the evidence on which 
 this conclusion is based. As in the previous paper the data 
 given are from the records of the Bureau of Economic Geology 
 and Technology of the University of Texas, and used with the 
 permission of the Director of the Bureau. 
 
 Of several wells drilled in Caldwell County, the record of. the 
 three Cartwright wells, located about one and one-half miles 
 southwest of the Rios well, is perhaps the most complete. That 
 Cartwright 2 had penetrated the Eagleford, Buda, and Del Rio 
 formations, and entered the Georgetown-Edwards series of lime- 
 stones was determined by Dr. J. A. Udden as early as April, 
 1922. The interpretation of the formations penetrated in the 
 
10 University of Texas Bulletin 
 
 Cartwright wells is greatly facilitated by having at hand a 
 core taken at the depth of 2117 feet, which contains a number 
 of fossils. The most abundant fossil in the rock at this depth 
 is the small shell known as the "ram's horn" shell, Exogyra 
 arietina. As this fossil is characteristic of the Del Rio forma- 
 tion we have from this core a definite starting point in the 
 interpretation of the record of the well. By the aid of the 
 samples and from the driller's log the Del Rio, in this well, is 
 identified as extending from 2068 feet to 2176 feet. Under the 
 Del Rio is a porous limestone impregnated with petroleum. 
 This limestone is interpreted as of the Georgetown-Edwards 
 series of limestones. Drilling in Cartwright. 2 was continued 
 to 2411 feet. 
 
 Next above the Del Rio formation in Cartwright 2 is found 
 thirty-four feet of limestone, representing the Buda formation. 
 This rock differs from the Buda as commonly observed in wells 
 in that it is for the most part chalk-like in appearance and con- 
 tains glauconite. The rock next above this limestone is identified 
 from the driller 's log and from samples as the Eaglef ord forma- 
 tion, which in this well has a thickness of forty-nine feet. 
 Next above the Eagleford is the Austin Chalk, which has, accord- 
 ing to the driller's log, a thickness of 249 feet. No samples 
 of the Austin have been received from Cartwright 2. However, 
 a core was taken from Cartwright 3 at a depth of 1923 feet, 
 and hence within the interval assigned to the Austin. 
 
 Inasmuch as the Cartwright wells afford valuable aid in the 
 interpretation of the formations in this county there is included 
 in the following paragraphs the description of samples from one 
 of these wells made while the well was in process of drilling. 
 The descriptions are by Dr. J. A. Udden, and are included with 
 his permission. The log of this well is given subsequently. 
 
 Descrii^tion of samples from the United North and South Oil Com- 
 pany's Cartwright 2, on G. C. Kimble League, six and one-half 
 miles northwest of Luling, two and one-half miles southeast of 
 Prairie Lea, Caldwell County. Submitted by W. F. Peale, Luling, 
 Texas. 
 
The Producing Horizon in the Bios Well 11 
 
 BY J. A. UDDEN AND P. T. SEASHORE 
 
 Depth In Feet 
 Sample consists of two fragments of a core of grey, 
 thinly laminated, calcareous shale containing fish re- 
 mains, such as bones and scales. This shale splits 
 readily along the laminations. In thin section 
 the shale is seen to be of uniformly fine texture, 
 and to contain a great abundance of foraminifera 
 like Orbulina, Globigerina, and Nodosaria (?). Sev- 
 eral dstracod valves noted. The laminations in this 
 shale are caused by layers which are composed 
 largely of foraminifera. The bands of foraminifera 
 are from % to 1/3 mm. apart. The more clayey 
 bands between the layers of foraminifera are com- 
 posed of still finer layers, possibly consisting of 
 flattened foraminifera. In this matrix are White 
 calcareous lentils, which probably consist of flat or 
 flattened organic fragments. There are flat layers 
 of black bituminous material. In matrass the 
 shale gives strong odor of bitumen. When inserted 
 in an open flame the shale burns and gives off the 
 odor of burning peat and tallow. In washed 
 material some yellowish calcite and a few scattered 
 crystals of pyrite noted. Fossils: Globigerina, 
 Orbulina, and Textularia. Several fragments of 
 flsh scales and Inoceramus prisms present. 
 Eagleford 1993 
 
 Very light grey, soft, almost white limestone or chalk. 
 In thin section it is seen to be of very fine texture 
 and to contain a number of cavities filled with a 
 yellowish green mineral. Several spherical cavities, 
 evidently of organic origin, filled with calcite noted. 
 These range in size from .3 mm. to .1 mm. in 
 diameter , 2038 
 
 White limestone containing many minute fragments of 
 glauconite (?) and some shell fragments. In thin 
 section the limestone is seen to be very fine-grained. 
 Several fissures and cavities filled with calcite noted. 
 Foraminifera are found in great abundance. Such 
 forms as Orbulina, Globigerina, Lagena, and 
 Nodosaria were recognized. Several ostracod valves 
 noted. In places where the green grains are not 
 found, the rock has the typical appearance of the 
 Buda limestone 2040 
 
 Sample consists of a 3" core of bluish grey calcareous 
 
12 University of Texas Bulletin 
 
 Depth In Feet 
 shale or marl. Megascopically it Is seen to con- 
 tain shells of Pelecypods. Among these can be recog- 
 nized Exogyra arietina Roemer. Considerable cal- 
 cite and pyrite toted in the washed material. 
 Fossils: Orbulina, Globigerina, Textularia, Cristel- 
 laria, Anomalina, Nodosaria, Polymorphina (?), and 
 several unrecognizable forms. A sponge spicule 
 present. Six different types of ostracods noted. Of 
 these one has a pitted, two have smooth, and three 
 have a highly ridged carapace. Del Rio in aspect 5*1.17 
 
 The sample consists of several pieces of a four-inch 
 core. It is a soft dolomitic and bituminous ^yellow- 
 ish grey limestone, containing some fossil fragments. 
 Among these were noted a piece of the test of a 
 sea urchin, several ostreid fragments, fragments 
 of a Requienia patagiata. (?) In thin section the 
 rock is seen to have a lumpy texture and to con- 
 tain imbedded fragments of fossils mostly replaced 
 by calcite. Prom below the Del Rio, probably 
 Georgetown, possibly the Edwards 2182-2184 
 
 Grey marly shale with some yellowish grey dolomitic 
 ' limestone like that of the preceding sample. The 
 shale contains foraminifera such as Textularia and 
 Globigerina, Anomalina ammonoids, and Cristellaria. 
 A large oblong ostracod, an echinoid spine, frag- 
 ments of shells and fragments of a Bryozoan (mon- 
 ticuliporoid (?) noted. The latter forms a flat tab- 
 let and the polyps or zooecia are more or less ar- 
 ranged in orderly lines 2184-2188 
 
 The sample consists of two large pieces of a grey lime- 
 stone like that in the preceding sample and two large 
 pieces which show effects of heating and wearing 
 by the drill. The rock itself, so affected, seems to 
 have been calcareous. A fifth J:ragment is perhaps 
 an impure calcareous chert. The rock is too much 
 altered by the drill to be recognized 2197-2198 
 
 The sample consists of a dozen large pieces. Five of 
 these appear to be impure soft and fragile dolo- 
 mite like some of the rock described above. It con- 
 tains sufficient oil to give a strong odor. The other 
 pieces are grey marly shale, some of which contain 
 many smiall fossils. Fossils: Cristellaria cult'rata, 
 Truncatulina, Anomalina, Nodosaria zippei(?), 
 
The Producing Horizon in the Bios Well 13 
 
 Depth in Feet 
 Bythocypris, Nodosaria radicula, Nodosaria pauper- 
 ata, Nodosaria consobrina. These foraminifera are 
 of a larger size than Is common in the Cretaceous 2218-2220 
 
 Sample consists of a piece of a core of yellowish dirty 
 grey, porous dolomite, highly impregnated with oil. 
 It contains some very large calcite crystals and 
 fragments of poorly preserved mollusk shells. In 
 thin section the limestone is finely crystalline. As- 
 pect of Edwards limestone. 2235-2236 
 
 Sample consists of a piece of a core of yellowish dirty 
 grey dolomite impregnated with oil. On a polished 
 surface this dolomite is seen to contain shreds and 
 specks of bitumen. These shreds are mostly par- 
 allel to the bedding plane. In thin section the 
 dolomite is seen to be finely granular and to con- 
 tain minute fissures filled with a bituminous ma- 
 terial I 2240-2241 
 
 Sample consists of a piece of a core of grey, somewhat 
 soft and chalk-like limestone. This limestone is 
 seen to contain many minute cavities filled with 
 calcite. These are evidently casts of foraminifera. 
 In thin section the limestone is seen to be finely 
 crystalline and to contain specks of a, black 
 material 2242-2243 
 
 Sample consists of a piece of a core of grey compact 
 limestone containing many shell fragments. There 
 are also included in the sample several pieces of 
 grey marl. The shell fragments present in the 
 limestone are believed to be Requienia. In thin 
 section the limestone is seen to be fine grained and 
 has a lumpy texture. M3,ny minute crystals of 
 calcite noted. In the washed material from the 
 marl, calcite and pyrite were noted. The pyrite 
 occurs partly In irregular grains, partly as oolitic 
 masses and very largely also as fillings in the shells 
 of foraminifera. Some minute crystals of sphalerite 
 and perhaps some of Galena (?) were noted. 
 Fossils: Nodosaria, Polymorphina, Textularia, 
 Globigerina, Anomalina, and Pulvinulina were the 
 foraminifera noted. Several prisms which resem- 
 bled those from Inoceramus and a minute shark's 
 tooth, like one previously noted in the Upper Cre- 
 taceous. . . .' 2245-2246 
 
14 University of Texas Bulletin 
 
 Depth in i<'eet 
 A piece of a core of dirty yellowish brown porous dolo- 
 mite highly Impregnated with oil. This dolomite Is 
 irregularly laminated. Most of the laminations tend 
 toward about a 15° dip, one is nearly horizontal, 
 while another dips into it, the whole being perhaps 
 the result of cross-bedding. Evidence not conclu- 
 sive. In thin section the dolomite is seen to have 
 a slightly lumpy texture and to be very finely granu- 
 lar. Two limited areas in one section have a finer 
 and different texture from the rest, and appear to 
 be only slightly altered remains of fossils in the 
 original rock 2250-2251 
 
 Sample consists of several pieces of a core of light 
 grey limestone and a piece of grey very slightly cal- 
 careous clay. On a polished surface the limestone 
 is seen to contain many foramlninfera casts filled 
 with calcite. In thin section the limestone is seen 
 to be granular and to contain many foraminifera. 
 The washed material from the clay contains a few 
 fossils: Foraminifera resembling Cristellaria gibba, 
 Rotalia, Nodosaria, and Anomalina noted. Fragments 
 from larger shells, like those from pelecypods also 
 present i 2258-2259 
 
 Sample consists of several pieces of a core of dirty 
 brownish grey porous dolomite highly impregnated 
 with oil. Some of the pieces of the core are changed 
 to a porcelain-like consistency by heat developed 
 in drilling. In thin section the dolomite Is seen to 
 be very finely granular 2265-2266 
 
 Sample consists of about four cubic inches of light and 
 dark grey marl and a piece of a, core of light grey 
 limestone. Into the marl has been introduced pock- 
 ets of glauconit'i rock, almost pure glauconlte. This 
 mixing may perhaps be due to work by the drill. 
 If such is not the case the sample suggests that 
 the drill has been going through a fault breccia or a 
 cave deposit. The glauconite is in part almost black 
 and in part green. The grains show the usual ex- 
 ternal reticulated sutures. In size these grains 
 range up to % mm. In diameter. In thin section 
 the limestone is seen to be granular with small 
 pockets of calcite representing casts of foraminifera. 
 In the washed material from the marl, the follow- 
 ing fossils were found:- Foraminifera resembling 
 
The Producing Horizon in the Bios Well 15 
 
 Depth in Feet 
 Nodosaria zeppei, Nodosaria obliqua, Nodosaria radi- 
 cula, Nodosaria nitida, Nodosaria consobrina, Cris- 
 tellaria obtusata, Cristellaria cultrata, Cristellaria 
 gibba, Cristellaria mamilligera, Anomallna ammo- 
 noides, ADomalina grosserugosa, Rotalia Tritaxia, 
 Lagena, Polymorphina lactea, Polymorpbina com- 
 pressa, Pulvinulina, four types of Frondicularia, 
 one of whicli is very narrow and about 4 mm. 
 long, Globigerina, Textularla saglttula, Truncatu- 
 lina refulgens, Splrillina, and several otber forami- 
 nifera which could not be determined. Ostracods, 
 both with smooth and with fluted and pitted cara- 
 paces noted. Fragments of Pelecypod and gastropod 
 shells, Dentalium fragments and Inoceramus 
 prisms (?) present. Several otoliths, fish teeth 
 and spines and Echinoid spines were also noted 2269-2270 
 
 Sample consists of several pieces of grey marl and a 
 piece of; a core of light grey chalk-like limestone. 
 The grey limestone under the hand lens shows 
 traces of fossils, minute crystals of calcite, and 
 areas of lighter colored limestone. In thin section 
 the limestone is seen to be finely granular and 
 very uniform in texture. The washed material 
 from the marl contains some calcite and pyrite. 
 Bright red hematite grains noted. These range 
 up to 1 mm. in diameter. Fossils: A large Cristel- 
 laria cultrata measuring about 1 mm. in diameter, 
 a nodosaria resembling Nodosaria pauperata, sev- 
 eral Anomallna ammonoides and a fragment which 
 may represent Frondicularia. An ostracod pres- 
 ent, which is very wide at the hinge, this wide 
 part being covered with longitudinal flutings. Sev- 
 eral fragments of well-preserved thick fish scales 
 and many Echinoid spines present. Several frag- 
 ments of granular calcite, which were washed from 
 the marl, show slickensides with very straight and 
 delicate striations on one surface 2273-2274 
 
 Sample consists of several pieces of grey marl and a 
 piece of a core of dirty brownish grey somewhat 
 dolomitic limestone showing embedded fragments 
 of fossils. In the washed material from the marl 
 are found fragments of brownish finely crystalline 
 dolomitic limestone, a few fragments of a black 
 bituminous material, and several aggregates of min- 
 ute crystalline pyrite. Fossils: Fragments of a 
 
16 University of Texas Bulletin 
 
 Depth In Feet 
 Nodosaria, Textularia, ostracods, fragments of casts 
 from Gastpopods and Inoceramus prisms. In thin 
 section the limestone is seen to be finely crystalline 
 and to contain areas filled with clear calclte. 
 Slickensides on granular calcite noted ,. . . . 2280-2281 
 
 Sample consists of a piece of a core of soft grey porous 
 limestone and several pieces of grey calcareous 
 shale or marl. In the washed material from the 
 . marl were found fragments of white limestone and 
 grey dolomitic limestone. Considerable glauconite 
 present. These glauconite grains show the regular 
 reticulated surfaces. Fossils: Anomalina, Globi- 
 gerina, Textularia, Crlstellaria cultrata (?), Gris- 
 tellaria gibba (?), a ribbed Nodosaria, Vaginulina, 
 Nodosaria pauperata (?), an ostracod carapace, and 
 several Inoceramus prisms noted. Fragments of 
 shells like those from pelecypods, and fish remains, 
 such as fragments of spine noted. A small black 
 spherical body about .3 mm. in diameter with a 
 smooth polished exterior. This body resembles some 
 found in the Cohn Bros. No. 2, near Kyle in Hays 
 County. On a polished surface the limestone is 
 seen to/ contain small nodules of a lighter colored 
 limestone. Some very fine quartz sand and small 
 are&,s filled with calcite. In thin section this lime- 
 stone is seen to be fine grained and to have a 
 lumpy texture, rather chalk-like 2305-2306 
 
 Saifiple consists of several pieces of a grey marl and a 
 piece of a core of grey limestone. On a polished 
 surface this limestone is seen to contain some min- 
 ute cavities filled with calcite. Many black specks 
 noted. These cavities and specks are evidently 
 casts of foraminifera. The limestone is seen to con- ' 
 tain irregular lumps of darker rock surrounded by 
 a matrix of lighter colored rock. These lumps 
 range in size upward to more than an inch and re- 
 minds one of blotchings seen in the Austin Chalk. 
 In thin section the limestone is seen to be fine 
 in texture and to contain a few obscure traces of 
 foraminifera. The washed material from the marl 
 contains mainly fragments of light grey limestone, 
 considerable pyrite, and a few grains of glauconite. 
 Much of the material has been altered by the heat 
 generated in drilling. Several ostracod carapaces. 
 
The Producing Horizon in the Bios Well 17 
 
 Depth in Feet 
 a Pulvinulina, a Globigerina, and a Textularia pres- 
 ent in the sample 2408-2409 
 
 Sample consists of several fragments of grey marl 
 and a piece of a core of pure and minutely crystal- 
 line white strontianite. One surface of the core of 
 strontianite has an adhering layer of grey lime- 
 stone. The contact between the limestone and the 
 strontianite is very irregular, hut bends in such a 
 way as to suggest that the strontianite has been de- 
 posited in a cavity in the limestone or has grown 
 as a concretion. In thin section the limestone is 
 seen to be finely textured and to contain many 
 minute crystals of calcite. The washed material 
 from the marl yields mostly fragments of a light 
 grey limestone, brownish crystalline dolomite and 
 white strontianite , ( ?) . A few crystals of pyrlte 
 noted. Many of the fragments have changed to a 
 porcelain-like substance by heat developed by the 
 drill. Prisms like those from Inoceramus noted. 
 A Textularia and Globigerina present 2448-2449 
 
 Note by J. A. Udden; — The samples, from 2245-2246 down to 2280-2281 
 show several features that strongly suggest that the drill in this dis- 
 tance has been close to a fault plane. The strongest evidence is in 
 the occurrence of a shale or -marl which contains a fauna of Upper 
 Cretaceous fossils, such as occur in the upper part of the Taylor or in 
 the Navarro. Upper Cretaceous material was found occurring below 
 the Georgetown and perhaps below or in the Edwards limestone. The 
 presence of glauconite in association with the marls having an Upper 
 Cretaceous fauna corroborates such a conclusion. The same may be 
 said of the occurrence of straight slickensides and such minerals as 
 sphalerite, hematite, galena ( ? ) , and abundant pyrite. The fact that 
 limestone and bodies of glauconite have been worked into some of 
 the marl suggests that the drill may have gone through a fafilt breccia. 
 Pieces of marl in which this was observed appeared to be parts of a 
 core, but little disturbed by the work of the drill. 
 
 Another explanation that would, account perhaps equally well for the 
 finding of Upper Cretaceous material in the Upper Comanchean and for 
 the mineralization and brecciation noted would be that the drill has in 
 the distance from 2245-2281 penetrated a cavern deposit. In a fault 
 plane one would rather expect to find more calcite than occurs in the 
 present samples. On the other hand, more sand would perhaps be ex- 
 pected in a cavern deposit than was found in the present samples. 
 The strongest evidence for this material being regarded as a cavern 
 deposit Is the presence in the marl of what appears to be sorted 
 
18 University of Texas Bulletin 
 
 glauconite grains, which are most likely to have been washed together 
 by running water, such as might form a cavern deposit. Fragments 
 of harder parts of the country rock are usually present in the cavern 
 deposits, into which they are introduced either by falling from the 
 walls of the caverns or by water running in the caverns/ 
 
 Since writing the above it appears possible that the samples may 
 represent material mixed in drilling. 
 
 The Rios Well 
 
 The record of the Rios well is made up from cores and cuttings 
 of the rock drilled through, and from the driller 's log. Accord- 
 ing to the log, chalk rock was drilled through in this well from 
 1630 feet to 1868 feet, a total of 238 feet. No samples have 
 been obtained of this chalk. However, immediately under the 
 chalk, at 1898 feet, samples were obtained which are of the 
 character of the Eagleford formation. From the log some diffi- 
 culty is experienced in iixing the lower limits of the Eagleford 
 in the Rios well. It seems probable, hawever, that the Eagle- 
 ford is to be regarded as extending to 1961 feet, having thus a 
 thickness of 93 feet. This interval of 93 feet includes 50 
 feet logged as "broken rock" and as limestone, which may or 
 may not be properly included in^the Eagleford. Next under- 
 lying the Eagleford is a light colored limestone rock identical 
 in character with that regarded as the Buda in the Cartwright 
 well, the rock being chalky in appearance, and' containing glau- 
 conite. In my previous publication I referred to the presence 
 of glauconite as an unusual feature of the Buda formation. Re- 
 cently, however. Dr. R. T. Hill has called my attention to the 
 Austin folio of the United States Geological Survey, in which 
 the Buda limestone found on Shoal Creek, in the vicinity of 
 Austin, is said to be glauconitic. The glauconite of the Shoal 
 Creek rock, however, is inconspicuous and not easily recognized, 
 in this respect differing from the conspicuous green glauconitic 
 particles in the rock from these wells. 
 
 A sample from the Rios well at 2005 feet presents the lithologic 
 appearance of the Del Rio formation, although from this sam- 
 ple, which is limited in quantity, no index fossils of that forma- 
 tion were obtained. A sample taken at 2136 feet consists in 
 part of a very porous limestone impregnated with petroleum. 
 
 ^BuU. U. S. Geol. Survey, No. 505, p. 87, 1912. 
 
The Producing Horizon in the Bios Well 
 
 19 
 
 Rios*"/ 
 
 Cartwnghf ^2 
 
 Fig. 1. Sketch 
 showing formations 
 drilled through in 
 the Rios and Cart- 
 wright wells from 
 the Austin to the 
 Georgetown- 
 Edwards forma- 
 tion. The interpre- 
 tation as here 
 given is from the 
 drillers' logs and 
 from samples. The 
 top and bottom of 
 each formation is 
 determined from 
 the drillers' log, 
 while the identifi- 
 cation of the form- 
 ation itself is in 
 most instances 
 from samples of 
 rock cuttings or 
 cores. The state- 
 ment, "B. arietina 
 abundant," refers 
 to the abundance 
 of this fossil in a 
 core taken at 2117 
 feet in Cartwright 
 No. 2. 
 
 "Vertical scale of 
 sketch: One inch 
 equals 100 feet. 
 
 /630 
 
 Eag/eford 
 ^1' 
 
 6«orferown 
 Edwards 
 
20 University of Texas Bulletin 
 
 Successive samples below this depth to 2160 feet consist of lime- 
 stone, including at least oneJ^yer of black flint. This lime- 
 stone rock is similar in character and is to be correlated with 
 that referred to the Georgetown-Edwards series in the Cart- 
 wright well. The oil in the Eios well is obtained at 2161 feet. 
 
 Although differing more or less in thickness the formations 
 of Rios 1 are definitely correlated with those of Cartwright 2. 
 The rock regarded as Greorgetown-Edwards, entered at 2176 
 feet in the Cartwright 2, finds its equivalent in Bios 1, at 2136 
 feet, this rock in each of the wells being porous and saturated 
 with petroleum. The Del Rio, identified by fossils in the Cart- 
 wright well at 2068 to 2176 feet, finds its equivalent in the Rios 
 well at 2005 to 2136 feet. Limestone rock found in the Rios 
 well from 1961 to 2005 feet is identical in appearance with that 
 regarded as Buda in Cartwright 2 at 2034 to 2068 feet. The 
 Eagleford in each well is identified by samples. The Austin 
 in the two wells is recorded from the driller's log, although 
 cores were obtained within this interval from Cartwright 3. 
 1 "With regard to the formations encountered in drilling in the 
 Rios and other wells in Caldwell County, it may be noted that the 
 rock here provisionally identified as Buda is unusual for the 
 Buda formation, in that in places it is scarcely to be distinguished 
 on lithologic characteristics from the Austin formation, being 
 a light colored glaueonitic limestone. However, if this rock is 
 interpreted as Austin it is then necessary to include within the 
 Austin formation the overlying shale member having the litho- 
 logic appearance of the Eagleford. Moreover, upon this inter- 
 pretation it would be necessary to assume that the Exogyra 
 arietina shells foTJnd in the core at 2117 feet in Cartwright 2 
 are secondary fossils. These shells in the core, however, are 
 exceptionally well preserved, having retained their most delicate 
 ornamentation, afCording no evidence of having been moved 
 from their original resting place. It may be added that the 
 presence of black flint in Rios 3 is suggestive of the Georgetown- 
 Edwards limestones rather than of the Buda, and that drilling 
 continued into this limestone series for 235 feet in Cartwright 
 2, supported by numerous samples, afforded no reason to doubt 
 the reference of the limestones to this series. iFrom within the 
 
The Producing Horizon in the Bios Well 21 
 
 interval assigned to the Buda, cores have been obtained from 
 Cartwright 3 indicating that alternating with or above the glau- 
 conitic rock of the Buda are layers which are not glautonitic 
 and which are typical of the Buda in texture. 
 
 In order to complete the record available on the Rios well 
 there is here included the description of samples from this well, 
 the log being given on a later page. A description of samples 
 obtained from Cartwright 3 is likewise included. The records 
 on these wells taken as a whole are believed to justify the con- 
 elusion that the oil from the Rios well is obtained from the 
 Georgetown-Edwards limestones in the Lower Cretaceous.. In 
 case of an overthrust or thrust fault, if such has occurred, 
 production may, of course, be obtained from the Upper Creta- 
 ceous after passing through Lower Cretaceous formations. 
 
 Description of samples from United North and South Oil Co.'s Rios 
 No. 1, one and one-half miles northeast of Cartwright No. 3, 
 John Henry League in Caldwell County. Samples submitted by 
 W. F. Peale, Luling, Texas. 
 
 BY E. H. SBLLABDS AND P. T. SEASHORE 
 
 Depth in Feet 
 Sample consists of several pieces of grey, slightly 
 micaceous, slightly calcareous shale. In the washed 
 material were found grains of glauconite, pieces of 
 calcite, flakes of muscovite, and a few quartz sand 
 grains. Fossils: Cristellaria, Globigerina, Textu- 
 laria, Anbmalina, Nodosaria, Frondicularia, Vaginu- 
 lina, and Tritaxia, fish scales, spines, and otoliths, 
 a part of an annelid jaw ( ? ) , Pelecypod shell frag- 
 ments, ostracods, and Inoceramus prisms. Two corals 
 noted. Probably Eagleford I.. 1898 
 
 Sample consists of two pieces of a core of light grey 
 limestone and a sample of .cuttings consisting of 
 grey marl and white limestone. The washed material 
 from the marl contains some glauconite, a few quartz 
 sand grains and several crystals of pyrite. Fossils: 
 Inoceramus prisms, Textularia, Tritaxia, Globigerina, 
 Cristellaria, Anomalina, Nodosaria, ostracods, and 
 shell fragments. On a polished surface the lime- 
 stone is seen to contain a large number of minute 
 cavities filled with microscopic crystals of pyrite. 
 In thin section the limestone is seen to contain a 
 very large number of foraminifera, many slender 
 
22 University of Texas Bulletin 
 
 Depth in Feet 
 needle-like spines and Echinoid spines and tissue. 
 Many of the foraminifera have been replaced by 
 pyrite I960 
 
 Sample consists of a piece of grey finely textured marl. 
 "Washed material consists of pieces of calcite and 
 crystals of pyrite. Fossils: Inoceramus prisms, 
 Globigerina, Textularia, and Ostracods. Probably Del 
 Rio , 2005 
 
 Grey marl and dirty yellowish grey porous limestone. 
 The limestone is impregnated with oil. In the 
 washed material from the marl were noted glau- 
 conite, crystals of pyrite, a few pieces of calcite, 
 and a, number of fragments of a black soft material 
 resembling asphalt. Fossils: Inoceramus prisms, 
 Cristellaria, Tritaxia, Nodosaria, Textularia, Globi- 
 gerina, and Echinoid spines. In thin section the 
 limestone is seen to be fine-grained and to have a 
 slightly lumpy texture. The entire section is filled 
 with microscopic crystals of calcite. Several veins 
 and larger areas are made up of crystals of calcite 2136 
 
 Like sample of 2136 2138 
 
 Sample consists of pieces of yellowish grey porous lime- 
 stone and grey arid almost black marl. The en- 
 tire sample is permeated with oil. The washed 
 material from the marl contains aggregates of 
 minute crystalline pyrite and pieces of calcite. 
 Inoceramus prisms, Cristellaria; Anomalina, Vag- 
 inulina, Textularia, ostracods, and pelecypod shell 
 fragments. In thin section the limestone Is seen to 
 be finely grained and to have a luriipy texture. A 
 few smalli areas of calcite noted 2139-2140 
 
 Sample consists of dark grey marl and two pieces of 
 a core of yellowish grey porous limestone. The 
 entire sample is impregnated with oil. In the 
 washed material from the marl were noted many 
 fragments of limestone like that represented by the 
 core, pieces of calcite, crystals of pyrite, grains 
 of glauconite, and fragments of black flint. Fos- 
 sils: Cristellaria, Anomalina, Nodosaria, Globi- 
 gerina, Textularia, ostracods. Inoceramus prisms 
 and fragments of shell from other pelecypods . . . 2144 
 
TTie Producing Horizon in the Bios Well 23 
 
 Depth in Feet 
 Light grey marl. In the washed material were found 
 a few pieces of calcite, crystals of pyrite, and pieces 
 of a black asphaltic material. Fossils: Inoceramus 
 prisms, Bchinoid spines, Globigerina, Tritaxia, 
 Cristellaria, and pelecypod shell fragments 2155 
 
 Sample consists of several pieces of a core of dirty 
 yellowish grey porous laminated limestone. The 
 laminations consist of thin layers of a black bitu- 
 minous material. Traversing the entire core and 
 parallel to the bedding plane is a vein of black 
 flint. In this flint can be seen imbedded obscure 
 traces of organisms. In thin section the limestone 
 is seen to be finely granular and to contain small 
 areas filled with calcite 2157 
 
 Sample consists of grey marl. In the washed material 
 were found a few pieces of yellowish grey lime- 
 stone, pyrite, and calcite. A few grains of glauco- 
 nite noted. Fossils: Cristellaria, Anomalina, Globi- 
 gerina, Textularia, ostracods, Inoceramus prisms, 
 fish scales, and pelecypod shell fragments 2158 
 
 Description of samples from United North and South Oil Company's 
 Cartwright 3, two and one-half miles southeast of Prairie Lea and 
 six and one-half miles northwest of Luling, G. C. Kimble Sur- 
 vey, Caldwell County. Submitted by W. F. Peale, Luling, Texas. 
 
 BY E. H. SELLAEDS AND P. T. SEASHOBE 
 
 Depth in Feet 
 Sample consists of grey marl. The washed material 
 consists mainly of fossils, pieces of calcite, and 
 grains of glauconite and crystals of pyrite. The glau- 
 conite shows regular reticulated sutures. Fossils: 
 Inoceramus prisms, pelecypod shell fragments, a 
 fragment of an Ammonoid, Nodosaria, Cristellaria, 
 Pulvinullna, Vaginulina, Tritaxia, Anomalina and 
 ostracods. In the washed material from % mm. in 
 diameter and down were found many Textularia, 
 Globigerina, and Orbulina. 1195-1225 
 
 Grey slightly micaceous marl. In the washed material 
 were found a number of fragments of Inoceramus 
 shells, shell fragments from other pelecypods, Tex- 
 tularia, Tritaxia, Anomalina, Cristellaria, Trunca- 
 tulina, and several smooth cailapaced ostracods. 
 A black, smooth surfaced, ellipsoidal body noted. 
 
24 University of Texas Bulletin 
 
 Depth in Feet 
 This body measures 1.25 mm. in length, and .4 mm. 
 in diameter 1349-1380 
 
 Grey marl, lithologically lilie preceding sample. In the 
 washed material were found a few aggregates of 
 minutely crystalline pyrite, pieces of oalcite, and 
 fragments of clay-ironstone. Fossils: Inoceramus 
 prisms, Nodosaria, several thin keeled Cristellaria, 
 Pulvinulina, Frondicularia, Textularia, Globigerina, 
 and ostracods 1500-1590 
 
 Grey marl containing some fine sand. In the washed 
 material were found several aggregates of minutely 
 crystalline pyrite, fragments of fine grained highly 
 calcareous sandstone, larger quartz sand grains. 
 A few brown, red and pinkish chert grains also 
 noted. Several pieces of clear calcite, and some 
 scattered grains of glauoonite present. Fossils: 
 Inoceramus prisms and shell fragments, fragments 
 from other pelecypods, a large Cristellaria 'cul- 
 trata, several thin keeled Cristellaria, Pulvinulina, 
 Textularia, Globigerina, Anomalina, and a number 
 of varieties of ostracods 1590-1642 
 
 Sample consists of grey marl. In the washed material 
 are found a few qilartz sand grains, piece of white 
 calcite, pyrite and glauconite, and a number of 
 fossils. Fossils: Fragments of Inoceramus and 
 other pelecypod shells, Anomalina ammonoides, 
 Cristellaria gibba, Cristellaria cultrata, Nodosaria, 
 Lagena, Textulai-ia, Globigerina and Orbulina 1642-1700 
 
 Grey slightly micaceous marl. The washed material con- 
 sists mainly of grains of glauconite and fossils, a 
 few quartz sand grains noted. Fossils: Inoceramus 
 prisms, Cristellaria, Nodosaria, Anomalina, Textu- 
 laria, Pulvinulina, Globigerina, and Orbulina. A few 
 echinoid spines also noted. A few black ellipsoidal 
 bodies with a smooth polished exterior surface 
 present 1785-1798 
 
 Sample consists of grey marl. In the washed material 
 were found a few grains of glauconite and aggregates 
 of minutely Crystalline pyrite. Fossils: Textularia, 
 Globigeria, Anomalina, Cristellaria, Lagena, Poly- 
 morphina, Pulvinulina, ostracods, Inoceramus prisms, 
 and echinoid spines 1816-1841 
 
The Producing Horizon in the Bios Well 25 
 
 Depth In Feet 
 Sample consists of several pieces of a core of grey lime- 
 stone containing a large amount of glauconite and 
 minute crystalline pyrlte. On a polished surface the 
 limestone is seen to contain a large number of lentils 
 of lighter colored limestone. A few small shell frag- 
 ments noted. One piece of the core is in part made 
 up of grey compact marl. In thin section the lime- 
 stone is seen to be finely textured and to contain a 
 large number of foraminifera, echlnoid spines, and 
 many small slightly curved spines, which probably 
 represent section of ostracod carapaces. Among the 
 foraminifera can be recognized Obulina, Globigerlna, 
 and Nodosarla(?) 1923 
 
 Sample consists of a piece of a core consisting in part of 
 grey compact marl, in part of light grey shaly lime- 
 stone. The washed material from the marl was seen 
 to contain fragments of grey shaly limestone, quartz 
 sand grains, calclte, and pyrlte. Many oblate and 
 prolate spheroids measuring from % to % mm. in 
 diameter noted. These oolitic spherules are black, 
 and have a smooth polished exterior. They are 
 made up of concentric layers and are partially 
 made up of pyrite. These bodies are similar to those 
 found in Cohn Bros. No. 2, Hays County, at a depth 
 of 145'-150', and in the United North and South 
 Oil Co.'s Cartwright 2, Caldwell County, at a depth 
 of 2305'-2306'. Globigerlna, Textularla, Orbulina, 
 ostracods, and a shell fragment noted. In thin sec- 
 tion the limestone is seen to be made up almost 
 entirely of Orbulina and Globigerlna 2013 
 
 Sample consists of a piece of a core of dark bluish 
 grey, very slightly calcareous shale of fine texture. 
 In the washed material were found pieces of calcite, 
 pyrite, and a few fish scales. In closed tube yields 
 enough bituminous material to sustain a flame 2039 
 
 Sample consists of several pieces of a core of dirty grey 
 limestone. On a polished surface the limestone is 
 seen to contain a large number of shell fragments. 
 Several large crystals of calcite noted. In thin sec- 
 tion the limestone is SQen to be fine grained and to 
 contain a number of cavities filled with calcite. 
 The entire section is traversed by a network of 
 lighter colored limestone. Foraminifera like Orbu- 
 lina and Globigerlna are found in great abundance. 
 
26 University of Texas Bulletin 
 
 Depth in. Feet 
 A Nodosaria noted. Echinoid spines and tissue 
 also present 2047 
 
 Sample consists of several pieces of a, core of grey 
 mottled limestone. On a polished surface this lime- 
 stone is seen to contain areas of lighter colored 
 limestone, an abundance of glauconite, blotches of 
 minutely crystalline pyrite, shell fragments, and a 
 very large number of foraminifera. In thin section 
 the limestone is seen to contain a number of cavities 
 filled with calcite. Many foraminifera, Echinoid 
 spines, and shell fragments 2052 
 
 Sample consists of several pieces of a core of white 
 limestone together with a piece of grey limy shale. 
 In the washed material from the marl were found 
 a few pieces of calcite and a small amount of pyrite. 
 Inoceramus prisms and a few shell fragments noted. 
 On polished surface the limestone is seen to con- 
 tain considerable glauconite and some small shell 
 fragments. In thin section the limestone is seen to 
 be made up almost entirely of foraminifera. Scat- 
 tered throughout the sections are found Echinoid 
 spines and tissue and small bodies of minute 
 crystalline pyrite 2065 
 
 Sample consists of grey marl and fragments of white 
 limestone. In the washed material were found a 
 few quartz sand grains, crystals of pyrite, crystals 
 of calcite, and grains of glauconite. Fossils: Cris- 
 tellaria, Anomalina, Nodosaria, Textularia, Globlger- 
 ina, Tritaxia, Inoceramus prisms, ostracod carapaces, 
 and echinoid spines 2065-2078 
 
 Sample consists of a core of white limestone contain- 
 ing a large number of minute grains of glauconite. 
 A. piece of a core of greenish grey compact limy 
 shale. This material also contains considerable glau- 
 conite. In the washed material from the marl a 
 large number of Inoceramus prisms were noted. 
 In thin section the limestone Is seen to be very 
 fine grained. Several cavities filled with calcite 
 noted. The limestone Is seen to be blotched with 
 areas of a darker colored limestone.^ The lime- 
 stone contains a very large amount of foraminifera. 
 Among these can be recognized Orbullna, Globl- 
 gerlna,; and Textularia. Fragments from larger 
 shells and echinoid spines also noted 2078 
 
The Producing Horizon in the Bios Well 27 
 
 Depth in F'eet 
 Sample consists of several pieces ot a core of white 
 limestone. On a polished surface the limestone is 
 seen to contain a large number of minute cavities 
 filled with microscopic crystals of pyrite. Many 
 shell fragments also noted. In thin section the 
 limestone is seen to contain a very large number 
 of foraminifera. Among these can be recognized 
 Orbulina, Globigerina, Nodosaria, and Anomalina. 
 Echinoid spines and small shell fragments 2087 
 
 Sample consists of several pieces of a core of grey 
 limestone containing a large number of minute 
 • bodies filled with microscopic crystals of pyrite. In 
 thin section the limestone is seen to be finely 
 grained, and to contain a large number of foramini- 
 fera Echinoid spines and tissue and shell fragments. 
 Some of the foraminifera shells have been replaced 
 by pyrite 2092 
 
 Peoduction From the Lower Cretaceous in Texas 
 
 In this connection it may be noted that the Lower Cretaeeoiis 
 formations have previously yielded some oil in the State. The 
 shallow wells in the South Bosque Field in McLennan County 
 obtain oil from these form(ations. In Panola County very 
 large gas wells have been obtained from a horizon. that is prob- 
 ably about 500 feet below the top of the Lower Cretaceous, 
 some of these gas wells having afforded a production of not 
 less than twenty million cubic feet of gas per day. A small 
 amount of oil has likewise been obtained from a horizon in 
 Panola County which is probably at, or near, the top of the 
 Lower Cretaceous. The Jones well near Kosse, in Limestone 
 County, apparently obtained oil from a Lower Cretaceous hori- 
 zon. These several gas and oil wells indicate that the Lower 
 Cretaceous should not be neglected as containing possible oil 
 producing formations in TexE^s. 
 
 Well Logs 
 
 Although not including all wells drilled in the county, the 
 wells, logs of which are given here, may be regarded as rep- 
 resentative of drilling conditions in the west half of the county. 
 
28 University of Texas Bulletin 
 
 Formations in the east part of the county may be expected at 
 
 an increased depth over that shown by wells in the west part 
 of the county. 
 
 Log of A. p. Cartwright 1, United North and South Oil Co.'s, G. C. 
 Kimble Survey, six and one-half miles northwest of Luling, and 
 two and one-half miles southeast of Prairie Lea. Drilling com- 
 menced March 29, 1921. Log corrected by steel line measurement 
 at 1784 feet. 
 
 Depth in Feet 
 
 From To Thickness 
 
 Surface clay and sand 18 18 
 
 Rock 18 34 16 
 
 Sand 34 64 30 
 
 Rock 64 108 44 
 
 Shale 108 128 20 
 
 Rock 128 130 2 
 
 Shale 130 138 8 
 
 Gumbo and gyp 138 143 5 
 
 Shale 143 155 12 
 
 Gumbo — set' and cemented 10" casing at 
 
 160'. Reduced hole to 9% 155 160 5 
 
 ^hale and boulders 160 460 300 
 
 Gumbo 460 474 14 
 
 Shell and shale. 474 504 30 
 
 Sand rock 504 507 3 
 
 Shell and shale. .'.... 507 537 30 
 
 Sand rock and pyrites of iron 537 538 1 
 
 Hard sand rock. , 538 542 4 
 
 Sandy shale, showing oil and gas at 550' 542 552 10 
 
 Sandy shale 552 593 41 
 
 Rook 593 594 1 
 
 Shale. . 594 ■ 634 40 
 
 Gypsum... 634 653 19 
 
 Shale and boulders 653 656 3 
 
 Gypsum and, gumbo. 656 697 41 
 
 Sand rock 697 699 2 
 
 Shell and shale 699 714 15 
 
 Shell... 714 721 7 
 
 Gumbo 721 731 10 
 
 Shell 731 771 40 
 
 Gumbo... 771 775 4 
 
 Shale... 775 784 9 
 
 Shale (sticky) .- 784 823 49 
 
 Gumbo 823 833 10 
 
 Shale and shell. . 833 853 20 
 
 Rock. . . 853 854 1 
 
 Soft shale 854 928 74 
 
 Gumbo.... 928 976 48 
 
 Lime rock — reduced hole to8%" 976 988 12 
 
 Shale 988 1,062 74 
 
 Gumbo 1,062 1,071 9 
 
 Shale. 1,071 1,109 38 
 
 Gumbo 1,109 1,121 12 
 
 Shale '. 1,121 1,264 43 
 
 Shale and boulders. . ; . . . 1,264 1,334 70 
 
The Producing Horizon in the Bios Well 29 
 
 Depth in Feet 
 
 Prom To Thickness 
 
 Gumtio 1,334 1,342 8 
 
 Shale 1,342 1,489 147 
 
 Gumbo. 1,489 1,496 7 
 
 Hard shale 1,496 1,514 18 
 
 Shale 1,514 1,522 8 
 
 Gumbo 1,522 1,542 20 
 
 Shale. 1,542 1,567 25 
 
 Sandy gumbo 1,567 1,581 14 
 
 Shale 1,581 1,586 5 
 
 Shale and shell 1,586 1,630 44 
 
 Gumbo 1,630 1,636 6 
 
 Shale. 1,636 1,700 64 
 
 Broken lime rock. 1,700 1,708 8 
 
 Sandy shale 1,708 1,738 30 
 
 Gumbo. 1,738 1,744 6 
 
 White shale 1,744 1,766 22 
 
 Broken lime rock 1,766 1,778 12 
 
 Gumbo 1,778 1,786 8 
 
 Chalk rock (hard) 1,786 1,788 2 
 
 Measurement with steel line showed 1784 
 
 Chalk rock 1,784 1,786 2 
 
 Reamed hole to S7s" — set 8" from 988 
 
 casing (did not cement) 
 
 Chalk rock 1,786 1,981 193 
 
 Chalk and slate 1,981 2,075 84 
 
 Showing oil and gas at 2,000'. ^ 
 
 Shale and slate 2,075 2,105 30 
 
 Blue slate 2,105 2,135 30 
 
 Shale with pyrites gravel 2,135 2,190 55 
 
 Broken lime ' 2,190 2,200 10 
 
 Water sand — coo/ sulphur water 2,200 2,211 11 
 
 Pyrite rock 2,211 2,215 4 
 
 Very hard — set 6" casing but failed to 
 
 shut off water. 
 
 Water sand — hot sulphur water. 2,215 2,229 14 
 
 Hard sand rock — very fine sand 2,229 2,231 2 
 
 Oil sand — showing oil and gas 2,231 2,236 5 
 
 Measurement with steel line 2,232 
 
 Sandy lime with iron 2,232 2,240 8 
 
 Hard lime 2,240 2,276 36 
 
 Sandy lime with iron 2,276 2,288 12 
 
 Soft lime 2,288 2,304 16 
 
 Hard lime 2,304 2,332 28 
 
 Interpretation: This well which starts probably in the Wilcox 
 appears to have entered the Austin formation at or near 1784 feet. 
 The record is indefinite as to the base of the Austin, and the thick- 
 ness of the Bagleford and Buda. However, these two formations 
 probably lie between 1,981 and 2,075, the "blue slate" at 2105 to 
 2135 probably represents a part of the Del Rio. The Georgetown- 
 Edwards limestones are probably entered at or near 2,190, the 
 sulphur water obtained at 2,200 and at 2,215 being quite certainly 
 from these limestones. The well probably terminates in the 
 Edwards. 
 
30 University of Texas Bulletin 
 
 Log of Uie Cartwright No. 2, of the United North and Sonth Oil 
 
 Comipany, Ca'dwell County. Depths Corrected By 
 
 Steel Line Meaistereinent. 
 
 Depth In Feet 
 
 Prom To Thickness 
 
 Surface 3 3 
 
 Doby. 3 6 3 
 
 Sand 6 8 2 
 
 Clay. 8 12 4 
 
 Rock 12 14 2 
 
 Sandy shale. 14 59 45 
 
 Rock 59 65 6 
 
 Rock sand (gas) , 65 104 39 
 
 Lignite 104 108 4 
 
 Rock, sand. . 108 134 25 
 
 Gumbo 134 138 4 
 
 Rock sand 138 141 3 
 
 Clay 141 149 8 
 
 Hard sand. . 149 164 15 
 
 Clay 164 168 4 
 
 Shale. 168 198 30 
 
 Clay 198 204 6 
 
 Shale 204 237 33 
 
 Sand (water) 237 250 13 
 
 Shale.... 250 283 33 
 
 Clay. 283 338 55 
 
 Shale... .' 338 359 21 
 
 Clay 359 396 '37 
 
 Sand 396 401 5 
 
 Clay.... 401 434 33 
 
 Boulder. . . 434 435 1 
 
 Clay. . 435 497 62 
 
 Rock 497 498 1 
 
 Hard sandy shale 498 507 9 
 
 Rock, . . 507 508 1 
 
 Shale 508 529 21 
 
 Pyrite 529 562 33 
 
 Clay 562 580 18 
 
 Sand rook. . 580 581 1 
 
 Clay '. 581 639 58 
 
 Boulder 639 640 1 
 
 Shale 640 665 25 
 
 Clay 665 697 32 
 
 Rock. 697 698 1 
 
 Hard shale 698 705 7 
 
 Clay and gyp 705 724 19 
 
 Shale and gyp 724 744 20 
 
 Boulders. 744 745 1 
 
 Shale and gyp 745 798 53 
 
 Shale '798 803 5 
 
 Shale and gyp 803 809 6 
 
 Clay 809 898 89 
 
 Rock 898 899 1 
 
 Clay 899 1,084 185 
 
 Shale. 1,084 1,095 11 
 
 Clay 1,095 1,162 67 
 
 Shale... 1,162 1,188 26 
 
 Clay 1,188 1,201 13 
 
 Shale 1,201 1,244 43 
 
The Producing Horizon in ike Bios Well 31 
 
 Depth In Feet 
 
 Prom To Thickness 
 
 Clay and gyp 1,244 1,250 6 
 
 Shale. . . 1,250 1,369 119 
 
 Clay. 1,369 1,426 57 
 
 Shale 1,426 1,494 68 
 
 Clay 1,494 1,519 25 
 
 Gyp... 1,519 1,535 16 
 
 Shale 1,535 1,542 7 
 
 Clay 1,542 1,556 14 
 
 Shale and gyp. 1,556 1,580 24 
 
 Clay and gyp 1,580 1,634 54 
 
 Clay with sand 1,634 1,654 • 20 
 
 Shale and gyp 1,654 1,688 34 
 
 Gummy shale 1,688 1,697 9 
 
 Gyp.. 1,697 1,736 39 
 
 Chalk 1,736 1,985 249 
 
 Shale and pyrites 1,985 2,000 15 
 
 Gummy shale -■ 2,000 2,008 8 
 
 Shale and pyrites. 2,008 2,034 26 
 
 Lime and shale 2,034 2,068 34 
 
 Gummy shale. 2,068 2,098 30 
 
 Sandy gumbo and boulders 2,098 2,112 14 
 
 Sandy shale and pyrites 2,112 2,130 18 
 
 Sandy shale. . .' 2,130 2,152 22 
 
 Sandy shal^e, hard 2,152 2,176 24 
 
 Hard sand rock, sulphurous 2,176 2,177 1 
 
 Conglomerate 2,177 2,186 9 
 
 Shale 2,186 2,192 6 
 
 Sandy lime and pyrites 2,192 2,194 2 
 
 Pack sand (shale) 2,194 2,195 1 
 
 Shale and lime. . 2,195 2,219 24 
 
 Sandy lime pyrites 2,219 2,222 3 
 
 Pyrites rock 2,222 2,224 2 
 
 Hard sand 2,224 2,232 8 
 
 Rock pyrites 2,232 2,233 1 
 
 Shale 2,233 2,234 1 
 
 Sandy lime rock, sulphurous and gaseous 2,234 2,257 23 
 
 Shale 2,257 2,260 3 
 
 Sandy lime 2,260 2,262 2 
 
 Shale 2,262 2,263 1 
 
 Sandy iime 2,263 2,270 7 
 
 Sandy shale 2,270 2,276 6 
 
 Sandy lime 2,276 2,277 1 
 
 Sandy shale and lime. 2,277 2,294 17 
 
 Sandy shale and lime (doby) 2,294 2,312 18 
 
 Sandy shale and lime 2,312 2,326 14 
 
 Pure lime. .. 2,326 2,340 14 
 
 Pyrite 2,340 2,341 1 
 
 Lime 2,341 2,350 9 
 
 Shale 2,350 2,352 2 
 
 Shale and lime. 2,352 2,411 59 
 
 Interpretation: The interpretation of this well has already been 
 given. The Austin is regarded as extending from 1736 to 1985 
 feet; the Bagleford from 1985 to 2034 feet; the Buda from 2034 to 
 
 2068 feet; the Del Rio from 2068 to 2176 feet. At or near 2176 
 feet the Georgetown-Edwards limestones are entered, in which for- 
 mations the well probably terminates. 
 
32 
 
 University of Texas Bulleiim, 
 
 Log of Cai-twright No. 3, United North and South Oil Company, 
 
 Located to the East of, and Near Cartwrlght No. 2 
 
 Depth in Feet 
 
 From To Thickness 
 
 Surface 7 7 
 
 Sand, shale and gravel 7 36 29 
 
 Broken rook 36 59 23 
 
 Sandy shale 59 85 26 
 
 Rock 85 86 1 
 
 Clay... 86 89 ' 3 
 
 Rock 89 90 1 
 
 Clay 90 120 30 
 
 Rock 120 125 5 
 
 Hard shale 125 145 20 
 
 Hard shale 145 304 159 
 
 Boulder. . 304 305 1 
 
 Gumbo 305 416 111 
 
 Shale 416 467 51 
 
 Rock ; 467 468 1 
 
 Hard shale. . 468 516 48 
 
 Rock 516 518 2 
 
 Broken rock 518 522 4 
 
 Shale and boulders — showing gas about 
 
 550'.... 522 • 595 73 
 
 Gumbo 595 629 34 
 
 Rock 629 631 2 
 
 Gumbo and boulders 631 647 16 
 
 Sticky shale 647 713 66 
 
 Rock 713 '714 1 
 
 Shale and boulders 714 780 66 
 
 Gumbo 780 796 16 
 
 Shale 796 803 7 
 
 Gumbo 803 821 18 
 
 Gumbo and lime. 821 838 17 
 
 Hard shale 838 843 5 
 
 Gumbc 843 864 21 
 
 Shale and some gas 864 893 29 
 
 Gumbo 893 944 51 
 
 Shale 944 995 51 
 
 Gumbo. . 995 l.uuff lO 
 
 Soft lime 1,005 1,008 3 
 
 Gumbo 1,008 1,012 4 
 
 Gumbo.... 1,012 1,063 51 
 
 Hard shale 1,063 1,071 8 ' 
 
 Shale and. gumbo 1,071 1,079 8 
 
 Gumbo 1,079 1,144 6.^ 
 
 Mucky shale 1,144 1,190 46 
 
 Shale and shells, gas showing 1,190 1,220 30 
 
 Mucky shale 1,220 1,235 15 
 
 Gumbo 1,235 1,320 85 
 
 Mucky shale 1,320 1,344 24* 
 
 Shale and shell 1,344 1,375 31 
 
 Mucky shale. . 1,375 1,420 45 
 
 Gumbo 1,420 1,429 9 
 
 Shale 1,429 1,500 71 
 
 Gypsy gumbo. . 1,500 1,525 25 
 
 Shale, lime, shell 1,525 1,622 97 
 
 Hard shale and lime 1,622 1,637 15 
 
The Producing Horizon in the Bios Well 33 
 
 Depth in Feet 
 
 _^ Prom To Thickness 
 
 Gyp-gumbo. 1,637 1,675 38 
 
 Mucky shale 1,675 1,695 20 
 
 Gyp-gumbo 1,695 1,709 14 
 
 Shale and boulders, some gas 1,709 l,V3« 27 
 
 Hard shale, gumbo. 1,736 1,760 24 
 
 Broken lime 1,760 1,790 30 
 
 Took tape line measurement 1795' 
 
 Austin chalk — use roller bit 1,790 2,004 214 
 
 Shale and lime 2,004 2,019 15 
 
 Broken chalk and shale 2,019 2,034 15 
 
 Shale and gypsum 2,034 2,036 2 
 
 Buda lime 2,036 2,058 22 
 
 Clay 2,058 2,060 2 
 
 Lime... 2,060 2,087 27 
 
 Interpretation: Austin, 1760 to 2004; Eagleford from 2004 to 
 2036; Buda entered at 2036 feet. Cartwright 3 was abandoned on 
 account of difficulties in drtilling and a second well started on this 
 
 locality, known as Cartwright 4. In Cartwriglit 4 chalk is recorded 
 
 as extending from 1768 to 1994; Eagleford shales from 1994 to 2035; 
 
 Buda limestone entered at 2035 feet. Bepths in both wells cor- 
 rected by steel line measurements. 
 
 liog of United North and South OH Co.'s ORios No. 1 Well, 
 Caldwell County. 
 
 Surface clay 25 25 
 
 Sand and gravel. 25 55 30 
 
 Gummy shale and boulders 55 115 60 
 
 Gumbo, boulders 115 171 56 
 
 Gumbo 171 176 5 
 
 Sand and gravel 176 197 21 
 
 Shale and boulders 197 282 85 
 
 Gummy shale 282 430 148 
 
 Gumbo and boulders 430 480 50 
 
 Rock 480 482 2 
 
 Gummy shale 482 514 32 
 
 Rock... 514 517 3 
 
 Gumbo and boulders 517 564 47 
 
 Rock 564 565 1 
 
 Gummy shale 565 609 44 
 
 Gumbo... 609 620 11 
 
 Rock 620 627 7 
 
 Gumbo 627 638 11 
 
 Shale and boulders 638 703 65 
 
 Gumbo... 703 724 21 
 
 Shale and boulders 724 1,055 331 
 
 Gumbo 1,055 1,130 75 
 
 Shale and boulders 1,130 1,175 45 
 
 Saltwater sand. . 1.175 1,195 20 
 
 Shale and boulders 1,195 1,270 75 
 
 Gumbo 1,270 1,290 20 
 
 Shale and boulders 1,290 1,385 95 
 
 Gummy shale 1,385 1,405 20 
 
 Chalky shale 1,405 1,440 35 
 
 Chalk and shell 1,440 1,499 59 
 
 Hard sandy shale .- 1,499 1,570 71 
 
 Gumbo... 1,570 1,630 60 
 
34 University of^ Texas Bulletin - 
 
 Depth in Feet 
 From To Thickness 
 
 Chalk rock ].,630 1,868 238 
 
 Hard shale and shell 1,868 1,875 7 
 
 Broken chalk and shale 1,875 1,905 30 
 
 Hard rock and pyrites , . . . . 1,905 1,911 6 
 
 Broken, chalk rock 1,911 1,918 7 
 
 Lime rock 1,918 1,955 37 
 
 Shale.... 1,955 1,961 6 
 
 Limy rock 1,961 2,005 44 
 
 Gray marl at. . , 2,005 
 
 Gray marl and yellow limestone at. . . . . 2,136 
 
 Fine grained limestones at 2,139 
 
 Yellowish gray porous limestones at. . . . 2,144 
 
 Light gray marl at 2,155 
 
 Yellowish gray porous rock at 2,157 
 
 Gray marl at 2,158 
 
 Sand(?) Containing oil 2,161 
 
 Interpretation: This well starts in the Wilcox and enters the 
 Austin at or near 1,635 feet. The formations below the Austin are 
 difficult to interpret from the driller's log, but froih an examina- 
 tion of a number of samples it seems probable that the formations 
 penetrated include the Eagleford, Buda and Del Rio, the well ter- 
 minating in the Georgetown-Edwards limestones. The record at and 
 below 2,005 feet is made' up from samples, except the last entry 
 which is the driller's record. (See Fig. 1.) 
 
 Log of the C. T. Schawe Well in Caldwell County 
 
 (Elevation B. M. at Maxwell is 604. Completed in 1914. Casing: 
 
 600', 10"; 800', 8"; 6" set from 1400' to 3312' with 300' of screen 
 at bottom.) 
 
 Depth in Feet . 
 
 From To Thickness 
 
 White rock. 10 10 
 
 Gravel 10 14 4 
 
 Rock 14 15 1 
 
 Yellow clay 15 54 39 
 
 Black soapstone 54 90 36 
 
 Blue gumbo. . 90 110 20 
 
 Soapstone 110 120 10 
 
 Blue gumbo 120 164 44 
 
 Black shale ' 164 234 70 
 
 Black gumbo 234 374 140 
 
 Shale 374 399 25 
 
 White gumbo 399 659 260 
 
 Shale.. 659 690 31 
 
 White gumbo 690 760 70 
 
 White rock, show of oil 760 1,036 276 
 
 Gumbo 1,036 1,071 35 
 
 White lime rock 1,071 1,113 42 
 
 White rock 1,113 1,142 29 
 
 Brown rock, porous 1,142 1,354 212 
 
 Brown rock, porous 1,354 1,425 71 
 
 Brown rock, porous 1,425 1,470 45 
 
 Brown rock 1,470 1,516 46 
 
 White rock, very hard, sulphur 1,516 1,524 8 
 
 Brown rock, porous, with hard white 
 
 layers. . . ; 1,524 1,567 43 
 
The Producing Horizon in the Bios Well 
 
 35 
 
 Depth, in Feet 
 Prom To Thickness 
 
 Gray rock, hard. . 1,567 1,615 48 
 
 Rock, porous, sulphur water 1,615 1,629 14 
 
 Hard gray rock, sulphur water 1,629 1,652 23 
 
 White lime rock. . . 1,652 1,786 134 
 
 Hard gray rock 1,786 1,808 22 
 
 White lime rock. . 1,808 1,843 35 
 
 Brown rock, layers white. 1,843 1,922 79 
 
 Hard white rock 1,922 1,929 7 
 
 Brown rock, layers white 1,929 1,961 32 
 
 Brown rock • 1,961 2,038 77 
 
 Gumbo, mud hole 2,038 2,046 8 
 
 Brown rock, very hard 2,046 2,054 8 
 
 Brown porous rock 2,054 2,161 107 
 
 Hard gray rock 2,161 2,175 14 
 
 Soft gray rock 2,175 2,238 63 
 
 Hard gray rock 2,238 2,284 46 
 
 Gumbo, mud hole 2,284 2,290 6 
 
 White lime rock 2,290 2,377 87 
 
 Soft brown rock, show of water 2,377 2,462 85 
 
 Brown rock, white layers 2,462 2,498 36 
 
 Hard brown rook 2,498 2,525 27 
 
 Gray sand rock 2,525 2,540 15 
 
 Soft brown rock. 2,540 2,677 137 
 
 Hard white lime 2,677 2,717 40 
 
 Soft yellow sand rook 2,717 2,763 46 
 
 White lime rock 2,763 2,773 10 
 
 Yellow sand rock " 2,773 2,907 134 
 
 Hard blue rock 2,907 2,918 11 
 
 Hard gray rock 2,918 2,937 19 
 
 Yellow sand rock 2,937 2,986 49 
 
 White sand rock 2,986 3,025 39 
 
 Gumbo, mud hole. . 3,025 3,061 36 
 
 Yellow rock, gumbo mixed 3,061 3,070 9 
 
 Red and blue gumbo, mixed 3,070 3,104 34 
 
 Hard white sand rock 3,104 3,117 13 
 
 White sand rock, soft and hard streaks. . 3,117 3,312 117 
 
 The driller's log extends to 3,312 feet only. However, samples were 
 
 obtained at intervals to a depth of 3,445 feet. Description of these 
 samples follow: 
 
 Descriptions of samples from C. T. ScTiawe Well at Maxwell. Samples 
 obtained by Alexander Deussen. 
 
 BY J. A. TJDDEN 
 
 Reddish-brown, medium-grained, quartzitic, calcareous 
 sand; sand consists largely of sub-angular clear 
 quartz grains. Other minerals present are ortho- 
 clase(?), hornblende, hematite, etc. Trinity sands, 
 (lift.) 
 
 Medium coarse-grained red sand, slightly calcareous; 
 sand consists of angular grains of clear quartz, and 
 fragments of hematite, orthoclase(?), etc.; quartz is 
 predominant. Typical Trinity formation. (20 ft.) 
 
 Depth in Feet 
 
 3323 
 
 3375 
 
36 University of Texas Bulletin 
 
 Depth in Feet 
 
 Reddish-brown, slightly calcareous, medium coarse- 
 grained sand; color is not so red as preceding; sand 
 consists chiefly of angular clear quartz grains aver- 
 aging .5 mm. in diameter; also present limonite, 
 hematite, orthoclase(?), etc. Trinity formation. 
 (15 ft.) 3405 
 
 Large fragments of red, compact, non-calcareous shale; 
 some large angular fragments of greenish-grey talc- 
 like compact non-carcareous shale; some large 
 fragments of angular milky quartz, averaging % 
 inch in diameter. This material taken out while 
 bailing the well. Marked as sample No. 5. Repre- 
 sents probably the Trinity formation 3400 
 
 Fragments of bluish-black, non-calcareous shale; ma- 
 terial is friable; a few grains of quartz possibly 
 from the stratum above. Material has an entirely 
 different aspect and color from the materials above. 
 Probably represents Carboniferous or earlier. (10 
 ft.) 3415 
 
 Fragments of blue, non-calcareous shale; fri-able. Car- 
 boniferous (?). (10 ft.) 3425 
 
 Small, sub-angular fragments of drab, non-calcareous 
 
 shale. Carboniferous (?). (14ft.) 3439 
 
 Sub-angular fragments of blue and gray non-calcareous 
 shale. Material pulverizes Into small fragments 
 averaging .5 mm. in diameter. (6 ft.) * 3445 
 
 Interpretation of the log: This well, starting probably in the- 
 Navarro formation, apparently enters the Austin at 7 60 feet and 
 passes the base of the Austin at 1,036 feet. The Bagleford probaljly 
 extends from 1,036 to 1,071 feet, being logged as "gumbo." The 
 Lower Cretaceous apparently extends from 1,071 to 3,405 feet. 
 From 3,405 to 3,445 feet the formation is identified by Dr. J. A. 
 Udden as indicated in the description of the samples, as pre- 
 Cretaceous. 
 
 Log of the Texas Southern Oil and Lease Syndicate's Thompson No. 
 1, 3% Miles S. E. of Prairie Lea, CSaldiveU County 
 
 Depth in Feet 
 
 From To Thickness 
 
 Clay and gravel. 35 35 
 
 Rock 35 53 18 
 
 Shale... 53 88 35 
 
 Rock 88 94 6 
 
 Gumbo 94 155 61 
 
 Shale (oil and gas showing) 155 160 5 
 
 Gumbo.... 160 455 295 
 
 Shale.... 455 475 20 
 
The Producing Horizon in the Bios Well 37 
 
 Depth in Feet 
 
 From To Thickness 
 
 Gumbo 475 494 19 
 
 Shale...... 494 514 20 
 
 Gumbo.... 514 525 11 
 
 Rook 525 528 3 
 
 Gumbo 528 545 17 
 
 Sandy shale (showing gas). . 545 555 10 
 
 Rock 555 560 5 
 
 Gumbo 560 588 28 
 
 Sandy shale 588 610 22 
 
 Gumbo 610 628 18 
 
 Sandy shale. 628 636 8 
 
 Gumbo 636 680 44 
 
 Shale (showing of oil and gas) 680 684 4 
 
 Gumbo 684 698 14 
 
 Shale (showing of oil) 698 710 12 
 
 Gumbo 710 730 20 
 
 Shale. . . 730 739 9 
 
 Gumbo 739 751 12 
 
 Shale 751 764 13 
 
 Gumbo 764 772 8 
 
 Shale and streaks of gumbo 772' 812 40 
 
 Gumbo 812 823 11 
 
 Shale and gas 823 830 7 
 
 GumlJo 830 848 18 
 
 Shale. . ". 848 855 7 
 
 Soft gumbo 855 861 6 
 
 Hard gumbo 861 871 10 
 
 Shale. ...1 871 890 19 
 
 Gumbo 890 895 5 
 
 Shale 895 901 6 
 
 Hard gumbo. . 901 932 31 
 
 Shale (showing of oil and gas) 932 945 13 
 
 Sticky shale 945 998 43 
 
 Shale 998 1,011 13 
 
 Gumbo with streaks of shale 1,011 1,037 26 
 
 Gumbo 1,037 1,058 21 
 
 Shale..' 1,058 1,070 12 
 
 Gumbo 1,070 1,078 8 
 
 Sticky shale 1,078 1,200 122 
 
 Gumbo 1,200 1,300 100 
 
 Shale 1,300 1,334 34 
 
 Gumbo 1,334 1,345 11 
 
 Shale 1,345 1,407 62 . 
 
 Gumbo 1,407 1,411 4 
 
 Shale 1,411 1,445 34 
 
 Gumbo 1,445 1,478 33 
 
 Shale....' ,1,478 1,493 15 
 
 Gumbo 1,493 1,498 5 
 
 Shale 1,498 1,620 122 
 
 Gumbo 1,620 1,633 13 
 
 Shale 1,633 1,674 41 
 
 Gumbo 1,674 1,700 26 
 
 Shale 1,700 1,721 21 
 
 Gumbo..-. 1,721 1,735 14 
 
 Shale (good gas pressure showing of oil) 1,735 1,835 100 
 
 Austin chalk 1,835 2,050 215 
 
 Gray shale (oil) 2,050 2,063 13 
 
38 University of Texas Bulletin 
 
 Depth in Feet 
 From To Thickness 
 
 Black shale 2,063 2,067 4 
 
 Slaty shale (black). . 2,067 2,073 6 
 
 Shale and lime (oil) uncertain 
 
 Gray limestone (large per cent of sand) 
 
 Total depth 2,092 
 
 At 2,063 to 2,067 there was sufEcient gas to shake the floor of 
 the derrick. 
 
 Interpretation: This well, which is located to the east of and near 
 the Cartwright wells, enters the Austin at 1,835 feet, drillers record. 
 No samples have been obtained, but from the log it seems probable 
 that the base of the Austin was passed at 2,050 feet, and that the 
 gray and black shales from 2,050 to 2,073 represented the Eagleford, 
 the gray limestone next below being probably the Buda. 
 
 The depth given in the log are those recorded by the driller. A 
 steel line measurement made after the well had been completed 
 and cleaned is said to have indicated that the total depth of the 
 well is 2,044 feet, or 48 feet less than the depth given in the drillers 
 record. This correction of 48 feet is to be applied in whole or in 
 part to the Austin chalk and other formations in the well. 
 
 The Ghoemlby Well in Guadalupe County 
 
 In a well now being drilled by the United North and South 
 Oil Company, on the Ghormley farm, near Sullivan, in Guada- 
 lupe County, chalk is recorded by the driller at having been 
 entered at 2084 feet. From a core taken at 2371 feet (corrected 
 depth) B. W. Brueks has obtained a shell, which appears to be 
 the right valve of Exogyra arietina, a fossil characteristic of the 
 Del Rio formation. 
 
INDEX 
 
 Page 
 
 Anomalina 12, 13, 14, 21, 22, 23, 24, 26, 27 
 
 Anomalina ammonoides 15, 24 
 
 Anomalina grosserugosa 15 
 
 Austin Formation 6, 10 
 
 Austin Quadrangle 8 
 
 Balcones Escarpment 5 
 
 Bituminous material 11, 15 
 
 Bryozoan 12 
 
 Buda formation 10, 11, 18 
 
 Bythocypris. . . 13 
 
 Carrizo formation 5 
 
 Cartwright wells 10, 28, 18 
 
 Cavern deposit 17 
 
 Clear Fork Creek, exposures on 6 
 
 Cristellaria 21, 21, 22, 23, 24, 26 
 
 Cristellaria cultrata 12, 15, 16, 24 
 
 Cristellaria gibba 14, 15, 16, 24 
 
 Cristellaria mamilligera 15 
 
 Cristellaria obtusata 15 
 
 Del Rio formation 10, 12, 18 
 
 Dentalium. . . ... 15 
 
 Dolomite 12, 13, 15 
 
 Eagleford formation 10, 11 
 
 Bchinoid spines 15, 22, 23 
 
 Edwards limestone i 9, 13 
 
 Bxogyra arietlna 10, 12, 20 
 
 Fault on San Marcos River : 9 
 
 Fish scales 11, 21, 23 
 
 Frondicularia 15, 21, 24 
 
 Georgetown formation 9, 12 
 
 Ghormley Well in Guadalupe County , 38 
 
 Glaueonite 14, 16, 21, 25 
 
 Globigerina 11, 12, 13, 15, 16, 17, 22, 23, 24, 25, 26, 27 
 
 Inoceramus 1, 13, 15, 16, 17, 21, 22, 23, 24, 26 
 
 Ivy, exposure near 6 
 
 Joliet, well near 8 
 
 Hill, R. T 18 
 
 Lagena • H. 15, 24 
 
 Local Structural Conditions 7 
 
 Lockhart, Midway exposure near 5 
 
 Lower Cretaceous, production from 27 
 
 Luling well 9 
 
 Maxwell, well near 7 
 
40 TJniversity of Texas Bulletin 
 
 Page 
 
 Mercer farm well 8 
 
 Midway formation 5 
 
 Mount Selman formation ■ 5 
 
 Navarro formation 5 
 
 Nodosaria ; ... 11, 12, 13, 14, 15, 16, 21, 22, 23, 24, 25, 26, 27 
 
 Nodosaria consobrina 13, 15 
 
 Nodosaria nitida 15 
 
 Nodosaria pauperata 13, 16 
 
 Nodosaria obliqua 15 
 
 Nodosaria radicula : 13, 15 
 
 Nodosaria zippei 12, 15 
 
 Oil from the Rios Well 8 
 
 Orbulina 11, 12, 23, 24, 25, 26, 27 
 
 Orthoclase 35, 36 
 
 Ostracods 11, 12, 15, 16, 21, 22, 23, 24, 25, 26 
 
 Otoliths. 15, 21 
 
 Polymorphina 12, 13,24 
 
 Polymorphina compressa. 15 
 
 Polymorphina lactea 15 
 
 Producing horizon in Rios Well .^ 9 
 
 Pulvinulina 13, 15, 17, 23, 24 
 
 Regional Structural Features 6 
 
 Requienia patagiata , 12 
 
 Rios Well 8, 18, 19, 33 
 
 Rotalia 14, 15 
 
 San Marcos, faulting near 7 
 
 San Marcos River, exposures on 6 
 
 Schawe well 34 
 
 Seashore, P. T 10, 21, 23 
 
 Sharks tooth 13 
 
 Shoal Creek 18 
 
 Sponge Spicules 12 
 
 Spirillina 15 
 
 Taylor formation 5 
 
 textularia 11, 12, 13, 16, 17, 21, 22, 23, 24, 25, 26 
 
 Textularia sagittula ' 15 
 
 Thickness of formations 7 
 
 Thompsoh well 3 g 
 
 Tritaxia , 15^ 21, 22, 23, 26 
 
 Tritaxia globigerina .' 21 
 
 Truncatulina , 3^2 23 
 
 Truncatulina refulgens ' \h 
 
 Udden, J. A g, n^ 17^ 35 
 
 Vaginulina. 16, 21, 22, 23 
 
 Wilcox formation 5