CHARAOTERISTIOS OF THE TAYLOR MARL, OF' TRAVIS COUNTY, TEXAS 
Apyroved~ 
App roved : 
Gradua e School 
7vj~~'f; I f1-.'r 
CHARACTERISTICS OF THE TAYLOR MARL 
..; 
OF TRAVIS COUNTY, TEXAS 
THESIS 
Presented to the Faculty of the Graduate School of ~he University of Texas in Partial Fulfillment of the Requirements 
For the Degree of 
MASTER OF ARTS 
BY 
Selwyn Oliver Burford, B.A. Austin, Texas 
. 
·June, 1928 
CHARACTERISTICS OF THE TAYLOR MARL OF 
TRAVIS COUNTY, TEXAS 

Table of Contents 
Page Introduction ------~-----------------------1 
N~ture of the formation --~----------------2 
Drainage ----------------------------------4 Structure ---------------------------------5 Regional structure --------------------5 Regional dip ------------------------5 Relation to the Balcones Fault ------5 Faulting and associated structure affecting the section of the formation 5 Austin-Taylor contact ---------------·.5 · 
Blue Bluff structure ----------------8 Del Valle Bluffs faulting -----------9 Taylor-Navarro contact --------------9 
Geologic section --------------------------10 Austin-Taylor contact zone ------------10 B~sal ~xogyra zone --------------------19 Blue Bluff and Del Valle Bluffs section 21 
iii 
Chalky stratum ---------------------------22 Gryphaea vesicularis zone ----------------24 Hel icoceras l edges -----------------------25 Bent onitic phase ------------------------~ 26 Taylor-Navar ro cont act zone --------------27 Foraminiferal data ---------------------------32 Graphic section ------------------------------45 Bibliography ---------------------------------46 Geological map -------------------------------54 
iv 
INTRODUCLTION 
I 
-~ 
Although the Taylor formation has been known and 
recognized as a definite division in the Gulf Series 
of the Cretaceous from an early date of geological 
investigation in Texas, it has not been seriously · 
studied in detail by the student of geology. It was 
through the realization of this fact, and also due to 
the hope that a study of both the stratigraphy anq 
faunal remains might be of benefit to the profession, 
that the assignment was accepted for investigation, 
the results of which are herein presented. 
The object of this thesis is to present in as brief 
and as logical a manner as possible, yet exhaustively, 
the data collected on this subject during a period ex­
tending over some three year1;3, and to interpret this 
data ' as accurateiy as its nature will permit. 
This will necessarily entail a description of the 
formation as to stratigraphy or sedimentation as well as . to outstanding fossil horizons. Furthermore, it will be 
advantageous both to the reader and the writer to dis­
cuss the faunal remains under two separate divisions, 
2 
those of macroscopic and those of microscopic character, each in conjunction with the related stratigraphic changes in the formation. 
Acknowledgements 
The writer is gratefully indebted to Professor F. L. Whitney, of the Geological Department of the University of Texas,. for valuable instruction, encouragement, help­ful suggestions, and for the greatly needed supervision of the .work in its various details. 
The writer is also gratefully indebted to Mr. Robert 
F. Cuyler, of the Department of Geology of the Universi~y 
' \
of Texas, for valuable data on foraminifera, for the use 
of valuable foraminiferal collections, and for the loan 
of bulletins and reports dealing with this phase of the work. 
The writer also wishes to thank the Bureau of Economic 
I 
Geology, of the University of Texas, for the use of a set of their samples from the R. R. Penn-Hardy #1, an oil w~il drilled in Bell County, Texas. 
?<· . 

3 
NATURE OF THE~ F.,0Rw\T:tQ~-T~:":-~· _;\ :~: 
, ... .... .. ~ .. .. . .. .. ~' .. ' .. ~ ...... 
The Taylor formation of Travis and adjoining Counties, throughout most of its section.of 550 feet, more or less, is a massive unctuous blue marly clay which weathers to a brownish-yellow color due to the contained iron com­pounds. Locally, this clay is called 11 joint clay11 due to its characteristic jointing or cracking into irregular blocks when seen in a fresh exposure. When freshly ex­posed, the formation is dark blue or blue-black, and shows no evidence of stratification, but when weathered slightly, most of the section shows definite stratifica­tion marks. 
The Taylor marl disintegrates rapidly, and when subjected to long continued weathering it soon erodes into low rounded hills and shallow drainage channels 

Characteristic Taylor marl topography 
forming a rolling prairie country covered with a luxuriant growth of vegetation. Consequently, considerable outcrop­pings of fresh exposures are rare. 
The Taylor marl is easily distinguished, from the under­lyi_ng conformable massive chalky-white Austin limestone, but it _differs from the Navarro clays above only in that the Navarro clays contain much more sand and a mineral called glauconite which causes it to weather to a greenish­yellow color. Glauconite is not pre~ent in the Taylor formation in quantities large enough to be detected in 
( 
the ·field, and sand is present in an inappreciab~e..atilount. 
DRAINAGE 
Most of the major streams of the Gulf Coastal Plain are maintaining themselves at grade and meander with a sluggish current. The Colorado River is no exception to this rule. It bisects the area studied and flows at right angles to the strike of the formations. The general elevation of the country varies slightly from 500 feet so that the tributaries to the Colorado also have a gentle gradient. All but the extreme north­eastern portion of the area is drained by the Colorado and its tributaries, this portion being drained by the tributaries of the San Gabriel River in Williamson County. 
STRUCTURE 
Regional structure ~ The Taylor marl out-crops .in Travis County in a band about six miles in width, run­ning from the northeast corner of the county in a south­westerly direction to its south line between Creedmore and Manchaca Springs as shown on the accompanying map. Where the formations have not been disturbed by faulting, the area has a regional .dip of slightly more than one degree _to the southeast. 
Due to the fact that the area under consideration lies between the Balcones and the Mexia-Luling fault zones, on the down throw side of the Balcones fault, it is considerably broken by faults paralleling the trend of the major fault systems. 
This disturbance extends over the entire area, even as far east of the Balcones fault line as Bastrop, Texas. 
Faulting and other structure affecting the section of the formation -On account of the faulting encountered in the Taylor .section, it has been, up to this time, ex­ceedingly difficult to arrive at a definite conclusion as to the exact thickness of the different stratigraphic and fossil horizons encountered. With the aid of the logs of two recently drilled wells, however, many of the doubtful features of this phase of the problem, it is felt, have been somewhat explained. 
As shown on the accompanying map, at Manchaca Springs, about ;two miles north of Buda on the Buda-Austin highway, a zone of considerable faulting is exposed. This zone is at least one-fourth of a mile in width and extends, &s shown, north-eastward to the east edge of the city of 
, ... 
Austin, whence it is possible to trace it north-eastward to Pecan Spring where a similar zone of faulting is en­countered in the .bed of the creek just north. of the bridge on ~he highway from Austin to Manor. Farther northeast­ward in the west bank of Little Walnut Creek, one-fourth of a mile north of the Austin-Manor Highway, it is again exposed. 
At Manchaca Springs, the fault has a total displace­ment, to the east, of a little more than one hundred feet as shown on the profile figured in the Austin Folio by Hill and Vaughan. This condition makes a faulted con­tact between the Austin chalk and the Taylor marl. The throw to the east decreases toward Pecan Spring where the displacement is approximately thirty feet. At Little Walnut Creek the displacement is about twenty feet •
•
The next indication of faulting is near the middle of the Taylor outcrop, at Blue Bluff on the north side of the Colorado River, at Hornsby's Bend, about six miles easi of Austin. At the east end of Blue Bluff there is a zone of jointing about one hundred yards wide, which gives rise to numerous springs flowing from the gravel above the clay exposure. It is believed that the dis­placement is to the west because of the westward dip of the strata up the River from the zone of jointing.1 This dip was estimated to be slightly less than one degree. It was also found that this dip increases nearer to the zone of jointing. The strike of this jointing is approximately N. 55° E., which lines up with the strike of other jointing at the west end of Del Valle Bluffs in Sneed's Creek two miles south­west of Blue Bluff. It is evident that the course of the river between these two points is influenced by this reversal since the usual southeast flow is abruptly changed at Blue Bluff to the southwest until it reaches the west end of Del Valle Bluffs. 
At a point beginning at Sneed's Creek on the south bank of the Colorado River and extending along the river to a point about one mile east of a north and south line through Del Valle Post Office, there is an exposed bluff of Taylor marl averaging thirty feet 
1. See Photograph on page 8. 
Blue Bluffs showing ferruginous layers in the Taylor marl which have a west­ward dip . 
in height. This exposure is known as the Del Valle Bluffa. At the fartherest west end of these bluffs, the dip of the strata ia approximately the same as the normal southeast dip of the region, being about one degree. This dip holds consta.nt for about one mile down the river, then the strata dip sharply, about three degrees, to the east into a large fault having at least seventy feet of displacement to the east. This faulted area is about one hundred feet wide, and within it the strata dip at a steep angle of 45° to the east. These strata are broken at short intervals allowing each succeeding higher segment of the tilted area to settle back a few feet. 
to the west. From this point for a mile eastward to the 
eastern extremity of the Del Valle Bluffs exposure, there 
is no other evidence of f aulting or dip. The massive · blue clay in this part of the exposure had no noticeable 
stratification marks whatever. 
The Del Valle Bluffs f a.ult 
In trying to determine the contact of the Taylor marl with t he Navarro clays, a line of f aulting was encountered extending from a point about one-quarter of a mile west of Kimbro, on t he Austin-Manor Highway, towards the mouth of Onion Creek. Two and three­
fourths miles north of Dunlap, and one-half mile west of the Dunlap-Manor Road, in a cultivated field, a fault was epcountered which had a strike of N. 300 E. This strike projects into the faulting at Kimbro and is be­lieved to be the same fault. The throw of this fault is between two hundred and two hundred and fifty feet to the east, which in most exposures along that line causes a faulted contact between the Taylor and the Navarro formations. 2 
In the compilation of the data collected in the field for the construction of the geological section, the faulting described above was necessarily taken into consideration. 
GEOLOGIC SECTION 
Austin-Taylor contact zone -The best exposure of the contact of the Taylor with the Austin formation was encountered in Little Walnut Creek, about six 
.. 
miles east of Austin on the road to Manor. This con­tact is ·well exposed both north and south of the bridge. :· ·If one walks about a half mile, either up or down the creek, nar th or south of the bridge, one will 
2. See discussion, paragraph 2, page 30. 
ll 
find a twenty-five foot section of massive dark blue unctuous calcareous clay in the creek bank resting conforma.bly on top of the blue-white Austin chalk or limestone. Except that there is a stratum of rather 
./ coarse textured, somewhat fissile, blue chalk, from one to two feet in thickness, separating the two, the change is abrupt from white hard chalky limestone to the massive blue marl. Comparatively speaking, this stratum is out­standing for the abundance of ExogYra ponderosa contained therein. There is also an abundance of other pelecypods associated with these. The E. ponderosa extends upward 

View of the Austin-Taylor contact . 
12 

into the Taylor marl for one hundred feet or more, and the specimens found there are developed to a much larger size than any found in the Austin chalk. The largest specimen of this species was found in Little Walnut . Creek about one mile northwest of the road. This specimen measured seven inches across the flat valve. 
Starting in the top of the fossiliferous chalk just mentioned, the Ostrea falcata makes its first appearance. 0. falcata accurs commonly throughout the Taylor section, and it is believed that with the abrupt change of lithology -from the typical Austin chalk to the typical Taylor marl, the appearance of O~falcata, iµld the large specimens of the !:. ponderosa, the opening of the true Taylor marl times is indicated. 
At Manchaca Springs the Austin-Taylor contact is hidden on account of the faulting described above under STRUCTURE. At other points along this faulted contact between Austin and the Manchaca Springs locality, the same condition was found to exist, and in order to find more data on this part of the section, it was necessary to study other localities outside of Travis County. In Williamson County, on the San Gabriel River, near Jonah, and on Brushy Creek near Hutto, some excellent exposures 
13 

of the upper Austin and the lower Taylor formations were found. 
At the former locality, which is one mile east of Jonah on the San Gabriel River, the same type of lithological transition from Austin chalk to Taylor marl was observed as at Little Walnut Creek in Travis County, except that the San Gabriel River section was found to contain more lime. The same association of fossils was found, and the follow'ing is a description of the section found at this locality. 
At Jonah the 9oncrete bridge across the River is laid on massive beds of typical Austin chalk. One­half mile south of this c~ossing, a hill of white chalk may be seen to the east about one hundred yards from the main road. This chalk contains an abundance of E. ponderosa, specimens of which vary from an eighth of an inch to four inches across the flat valve. This hill is the beginning of a low-lying, north-facing escarpment which extends eastward for about a mile. In following this escarpment, pne finds that the exposed chalk beds contain 
E. ponderosa in abundance and character similar to the first outcrop examined. At the dist~ced.of about three-f ourths of a mile along this escarpment, the E.ponderosa 
in g~neral_ become larger in size as the chalk grades gradually upward into a softer chalk which weathers to a light yellow color. One mile east of the Jonah-Hutto Ro~d, at the top of one of the low-lying hills, on the west· side of a narrow draw through which there is ·a small flow of water, the abundance of!:_ ponderosa decreases and the chalk changes abruptly into a marly clay. The Exogyras found in these exposures are of ·the a~gular type common to the Austin chalk. Simul­taneous .with this change in lithology, the 9..:.. falcata makes its first appearance. As at Little Walnut Creek, specimens of E. ponderosa found in the typical Taylor marl above this c.hange are scarce. They are, however, larger and more rounded than those found more abundant­ly in the chalk below. 
A bearing of N. 40° E. from this point to the east end of the bluff on the river, about one-half mile away, gives the approximate strike of the formation in this locality. But the lower beds exposed in this bluff contain 9..:_ falcata and occasionally a large speciman of !:_ ponderosa, which indicate that the contact zone just described lies beneath the river bed. From this bluff up the river as far as the bridge where the massive Austin chalk is exposed, the sediments are covered with 
15 
alluvium. The bluff exposure has a decided Taylor aspect except that the sediments at the base are very calcareous and are harder. This argillaceous chalk, however, shows the Taylor marl jointing_, and it also exhibits its characteristic rapid disintegration when exposed to the elements, weathering to a yellowish-brown color at the 
top of the cliff. 
The San Gabriel River exposure one mile east of Jonah, Texas. 
This outcrop extends only three-fourths of a mile down the river where the sediments are again covered 
with alluvium. The following section was measured at this bluff. 
Section .21!. the San Gabriel River ~Mile ~of Jonah, Texas Height above river bed 
28.5 	to 50 1 -----22 feet of blue calcareous clay weathering to a brownish-yellow. Contains large !.:_ ponderosa.• 
28 to 28.5 1 -----6 inches ·of hard brown arenaceous limestone having Fucoidal markings. 
0 to 28 1 --------28 feet of massive light blue argillaceou~ chalk containing E. nonderosa and O. falcata. Alter­nating hard and soft strata of argillaceous chalk. 
0 ---------------	Water level. 
At the second loaality, on Brushy Creek, directly south of Hutto, Texas, a section was found which contains a different species of fQ_~-~iJ_ at the contact between the two formations than had hitherto been found in any of the other sections. This has been identified as Gryphaeaostrea sp. which resembles Q.:_ vomer (Morton)3 
3. Stuart Weller. Cretaceous paleontology of New Jersey: Geol. Surv. of New Jersey, Vol. IV, 1907; p. 455, Pl. XLIV. 
and occurs in the transition zone with the first
. . 
appearance of o. falcata. An approximate section was run from the creek bottom beneath the bridge to the top of the hill in the road east of a two story farm­house as follows: 
Brushy Creek Section South of Hutto, Texas 
Height above creek bed  
110 to 115 1  5 feet of black soil.  
101 to 110 1  10 feet of yellow calcareous clay  
contains Q.:. Falcata.  
100 to 1011  ----­ 1 foot  of yellow chalky clay  
containing an abundance of  
Gry;phaeaostrea ~with  a  
few specimens of Q.:_ falcata.  
90  to  100'  -----­ 10 feet of white nodular chalk.  
E. Ponderosa less abundant  
than below.  
75  to  90~ ------­ 15 feet of white,  nodular chalk  
highly impregnated with.!.:.  
ponderosa varying in size from  
an  eighth of an  inch to  four  
inches  across  the flat valve.  

60 to 75' -----15 feet of white nodular chalk 
highly impregnated with 
Gryphaea aucella. 

0 to 60 1 ------60 feet of white massive chalky limestone containing, at the base, remains of Gryphaeas, Ammonites, ·Nautili, Exogyras, etc. These beds, from two to ten feet in thickness, are separated by thin partings of blue-black, fissile shale. This part of the section grows more argillaceous in its upper ten or fifteen feet. 
0 -------------Water level. 
The peculiar Gryphaeaostrea zone noted in the top of the section above was again discovered in an exposure on an east-facing hill just west of a farm­house one mile east of the road where the above­mentioned section was found, and one-half mile south of the creek. It was also in this exposure that the O. falcata was found, making its appearance just above the Gryphaeaostrea !E.· Approximately northeast from this hill, a ·fault in the creek bed brings the white Austin limestone in vertical contact with the massive blue clay typical of the basal Taylor marl, which clay contains ~falcata and h ponderosa. The strike of this fault is N. 10° E. with the down-throw to the southwast thus hiding from view the con­tact zone exposed on the hill. The contact is evidently faulted between twenty and fifty feet beneath the surface.. 
This is the only locality found where the Gryphaeaostrea zone crops out either in Travis or Williamson Counties, and its absence in other places 
. 
is possibly due to the irregularity in depth of the sea floor of Austin chalk at the time of the transition from Austin to Taylor, or to a difference in water con­tents, or to both. 
Basal Exogyra ~-From the base of the Taylo.r, extending upward for one hundred feet in the section, ~assive beds of typical blue Taylor marl were encountered. This clay has a high percentage of calcium carbonate, is apparently unlaminated (axcept in outcrops long ex­posed to weathering) and is not exceptionally fossili­ferous. This part of the section, however, does con­tain frequent epeciments of the E. ponderosa which are 
developed to an exceptionally large size, in some in-· stances being as large as seven inches across the flat valve as previously mentioned. 
At Manchaca Springs no speciments of the !!. ponderosa were found in the Taylor which indicates that the fault at that place has a throw of more than one hundred feet. Northeastward along this fault, which is indicated on the map, more and more of the !:. ponderosa zone is found until, at a point between c--­Little Walnut and Walnut Creeks, and east of the~, the full hundred-foot section is encountered. 
At or near the top of this hundred-foot section, a much more fossiliferous zone of a few feet in thickness was encountered. This zone is located on the Austin­Manor Highway in the road cut east of Walnut Oreek, beginning at the M. K. &T. R. R. and extending to the top of the hill to the east. Near the middle of the cut, a one-foot layer of clay contains an abundance of Baculites ovatus _<?.!J:S_·t.~, and above this for a few feet, the unctuous marly clay contains several other species such as the Nautilus !!E_, Exogyra ponderosa, small ~ragile pelecypods, small Ammonites, etc. Farther above this zone, the !.:.. ponderosa is absent. 
Blue :Siuff and Del Valle Bluffs section ­
-----~--------------------­
From the top of this &:_ ponciero-sa zone, a two hundred and seventy-five-foot section of the Taylor marl has the same character stratigraphically, but it is almost barren of large fossils except for the presence of the Inoceramus .!!E.:_, and Q.:. falcata, which are present throughout the Taylor section. 
There is one Stratigraphic feature present in this section not found elsewhere in the Taylor marl. This feature may be seen in Blue Bluff and Del Valle Bluffs. These exposures extend northwest and southeast so that 
· the dip of the strata to the southeast is shown in them. At the base of Blue Bluff, several bands of ferruginous 
~ 
material are present. These bands are usually from two to three inches in thickness and weather to a ferruginous color. The material is a mixture of gypsum, calcite crystals, and iron pyrites, the latter causing the redish-yellow color when it is oxidized by exposure to the atmosphere. The ferruginous layers are also present in the west half of the Del Valle Bluffs and 
· may be in part a duplication of the section exposed in the upper part of B1ue Bluff. At the Del Valle Bluffs fault, described below, these ferruginous bands dis­appear. 
22 
Chalky stratum -Near the middle of the Del Valle Bluffs, a f~ult was encountered which has a throw to the east of nearly seventy-five feet. The fractured area of this fault has a horizontal range of about one hun­dred feet (See photograph on page nine). At the water level, on the .downthrow side, a four-foot stratum of indurated white clayey chalk was found containing .an abundance of fossils. This stratum was also found in the east bank of the Colorado River one and one-tenth miles south of the Blue Bluff. From thirty feet below this ledge, the Taylor clay gradually grows less unctuous, and just beneath the ledge it becomes darker in color and more fissile. Above the ledge, the clay is also darker in color and more fissile than that below. Accompanying this change in lithology, the clay becomes more fossiliferous. These fossils reach the peak of their abundance in the ledge itself. The fossils below the chalk are of the smaller type, O. falcata, small fragile pelecypods and Inocerami. In the ohalkey layer, these are present in abundance associated with an erratic variety of the Exogyra costata, Helicoceras ~., Pleurotoma ~., Mautilus, and Gryphaea vesicularis. It is believed that this stratum is a tongue of the 
A view of t:i.e Onalky Stratum described on page 22. 
A view of t he North-facing Del V~lle Bluffs west of above locality showin~ east­ward dip of ferruginous layers . 
24. 

Pecan Gap Limestone and other analogous chalk strata of the Northeast Texas Taylor marl. 4 
Gryphaea vesicularis zone -From the clayey chalk layer upward through a thickness of approxi­mately seventy-five feet, the Taylor formation resembles the lower one hundred feet in lithological characteris­tics but contains the frequent remains of the Gryphaea vesicular.is (Lamarck), Race A. 5 This zone is partly expose.d in the Del Vall e Bluffs. Another good ex­posure of the same zone will be found in the east side of a high round hill about two miles southwest of Manor. In this locality, one specimen of the ,[:,_ costata was found, and evidently it is the same variety as found in the clayey chalk layer at the bottom of this section in the Del Valle Bluffs. Only two or three specimens of the ,!,:_ ponderosa were found in this exposure at the very t~p of the hill. A similar association of .Q..:_ vesicularis and E. -oonderosa was 
4 . . The Pecan Ga-o Limestone by Miss Ellisor; A. A. P. G. Bull., Dec., 1925 
Also C. H. Dane and L. W. Ste;,:ihenson; Notes on the Taylor and Navarro Formations in East-Central Texas; A. 
A. P. G. Bull., Vol. 12, No. 1, Jan., 1928. 
5. Gardner: Upper cretaceous: Maryland Geol. Surv., 1916; p. 575, Pls XXIX and XXVIII. 
fotind east of Pilot Knob and south of Moore and Berry's store, and it is believed that the combination of the two occurs at the top of the seventy-five feet of clay con­taining the Gryphaea vesicularis. 
The Helicoceras ledges -Above the .fh Vesicularis section the clay becomes less and less calcareous and more unctuous. About twenty-five feet above the last mentio~ed zone this unctuous clay cont~ins ledges of nodular yellow limestone containing an abundance of the Helicoceras navarroensis. This section of nodular lime is about twenty-five feet in thickness. The ledges are not continuous, but along a certain stratum of the clay there will be found large nodules of yellow 1i?Jle containmng the above-mentioned fossil in abundance. These nodules when broken are found to contain veins of calcite and have a high content of iron near the center. They are concretionary in character. About five of these ledges occur in the twenty-five foot section. Other fossils usually found in these ledges are the Sphenodiscus lenticularis, Placenticeras ..§J2.., Suavagesia austinensis,. Baculites ovatus, Microbacia ~., Hamites Comanchensis, large Ostrea Falcata, small pelecypods and gastropods. The Baculites of this horizon is the same species as that of the lower one-hundred foot section but in most 
cases it is much larger. 
The Helicoceras ledges are well exposed in a creek about a mile and a half southeast of New Sweden Church, or one-half mile southeast of Sandahl's farm­house. The same ledges are exposed again one mile southeast of Manor in a cultivated field. Another good exposure may be found in Williamson County on Brushy Creek one mile west of Rice•s Crossing in a bluff facing northwest. 
Bentonitic phase -Above the Helicoceras ledges, the clay becomes more and more unctuous and less calcareous as seen in an exposure one mile south and one-half mile east of the Sandahl Farm exposure in the west bank of the same creek. This change is due, it is believed, to the increase in the amount of a material commonly called bentonite, which is thought to be a finely-divided, decayed volcanic ash. To say the least, there is an increase in the greenish-white color and the greasy consistency of the clay, both of which are characteristic of the bentonite. This increase culminates at the top of the Taylor marl section in a layer of pure bentonite. This pure material has a light greenish-white color and a very. slick, greasy feeling. When dried in the sun or exposed to the atmosphere, it breaks up into very s~all pieces by cracking. When this dried material is soaked in water, it disintegrates 9ompletely by a fluffing-up process and becomes sus­pended in the water in microscopic particles. 
In this lithologic division of the upper Taylor, which .is about 40 feet in thickness, the !.:_ ponderosa is found occasionally, increasing in abundance near the top. Associated with it, the E. Cancellata is found in great·er abundance. Up to and including the Helicoceras ledges, the O. falcata is common.. In the bentonitic phase, however, this fossil is very scarce even lacking in some parts of it, as are other species. A decrease in microscopic fossils was also noticed in this part of the section. 
The exposure here discussed was found one-fourth of a mile west of Kimbro, seven miles northeast of Manor on the road to Elgin. Another exposure of part of the bentonitic phase may be found in Williamson County on the north side of Brushy Creek in a field gulley, one mile wesf of the Elgin-Taylor Highway. 
Taylor-Navarro Contact Zone -The only actual exposure of the contact of the Taylor with the Navarro formation was found in the locality one­fourth of a mile west of Kimbro. Starting at the 

~~oad one-fourth of a mile west from this place, and running north to a barn, there is a west-facing bank which is cut by deep gullies. ·rn thes,e gullies, ex­posures of the Taylor-Navarro Contact are encountered. T~ese exposures, which are usually fresh, give a fair idea of the transition from Taylor marl to XaYanro clay, there being visible about fifteen feet of the top and bottom of the respective formations. In its upper part, as already shown, the .Taylor marl is a so-called bentonitic clay. At the contact, this ben­tonite is overlain by a chalky_, sandy clay, the first six inches of which is in the form of a nodular, broken stratum. Covering this is a stratum of marly greenish-yellbw clay about ten feet in thickness which is divided into two or three intervals by thin layers of harder material of the same character. 
In the ~pper part of the Taylor marl, the E. 
pondez-osa and E.:_ Capcellata are common and extend 
upward through the section to the first nodular 
chalky layer where there is an abrupt change of 
species and the E. costata is present. The E.

-
costata is common in the Navarro formation and 
this transition is believed to be the marker for the 
Taylor-Navarro contact when considered in connection 


A view of the Taylor-Navarro contact described on page 28. 

Another view of same contact as above . 
with the cb~nge in lithology. Microscopic evidence was also found to support this idea. This will be discussed later. 
At this locality, quite a bit of faulting was encountered which had a trend of N. 300 E. Apparently, the displacement was to the east but the throw could not be determined. Following this projected line to the southwest, faulting of a similar nature was found in a cultivated field three miles north and one mile east of Dunlap, about one-half mile west of the Dunlap-Manor road. E. costata was found on the east side of this fault, but E. ponderosa and E. cancel1ata occur on the west side. The throw is to the east. The displacement could not be exactly determined, but shortly east of the fault, fossils and sediments typical of the middle Navarro were found. This fact indicates a throw of two hundred feet or more. A line joining the Kimbro fault and the one north of Dunlap has a bearing of N. 30° E. and will project into Onion Creek south of the Colorado River, where it is suspected that a similar faulted condition exists. 6 
s. A cross section along the line AB and BC has been prepared in connection with the map in order to show the apDroximate faulted condition of the Taylor in that-locality. 
31 

E Evidence of the latter is found in an exposure 9f Taylor marl seen in the west bank of Onion Creek two miles east of Del Valle on the road to Moore and Berry's store. This exposure is mappe'd by Hill and Vaughan in the Austin Folio as Navarro. Ferru­ginous layers and fossils, however, show it to be a part of the Blue Bluff section which is found in this locality on the account of faulting. Ferrug­inous layers of this character do not occur in the upper Taylor section. A1so, at a point one-half mile east of thi·S exposure (down Onion Creek from the crossing) in the north bank of the creek several springs were found issueing from the gravel, which is a good indication of a faulted condition. Ex­posures of the Taylor marl containing the !.:_ pond­erosa and E. Cancellata may be found farther down the creek to within one-fourth of a mile of the bridge on the main Del Valle-Bastrop highway. At this point exposures of clay containing glauconite in abundance were found and the disturbed, broken appearance of the formations lead one to believe that the Kimbro fault crosses at this point. The faulting must be of no small consequence for immediately north of the crossing of the Del Valle 

Bastrop Highway on Onion Creek, a long bluff of typical Navarro clay is exposed. This exposure is in the east bank of the creek and is, on an average, seventy-five feet in total heighth. In this clay ~ costata and Gryphaaa vesicularis were found, the latter being of a race entireiy different from those found in the Taylor marl. 
FORAMINIFERAL DATA 
Since the contact of the Austin chalk with the Taylor marl is decidedly marked by the change in the lithology and the species of larger fossils, foram­iniferal data would be of no special benefit in studying that horizon. But, in studying the Taylor-Navarro contact, it is advantageous to use this data since the transition is not so abrupt. 
Samples were collected for this purpose during the time that the field work was being done. Besides the samples which were taken in the creek west of 
-the
Kimbro for the study of~contact, other samples were taken.at Manchaca Spring, Little Walnut Creek, east of Pilot Knob and at other points until it was felt that a representative set of samples of the Taylor 

formation was obtained. The samples at Blue Bluff 
and Del Valle Bluffs were taken every five and one­
half feet, and the samples at the other localities 
were taken, as nearly as was possible, at the same 
intervals•. This set of samples (about one hundred 
in number) has been washed carefully in the labora­
tory and examined for foraminiferal remains. The 
results of the first washing not being satisfactory, 
a' second set were washed and examined. 
On second examination, very good results were 
obtained and some excellent specimens of the Taylor 
f oraminifera were found. The following is a list 
of the species identified from the field samples: 
Ammodiscus incertus (d'Orbigny)
Anomalina taylorensis (Carsey)
Anomalina grosserugosa (Gumbel)
Bigenerina nodosaria (d1 0rbigny)
Bolivina latticea (Carsey) or Bolivinoides 

decorata (Jones)
Bolivina plaita (Carsey)
Bulimina comnressa (Carsey)
Bulimina pupoides (d10rbigny)
Cristellaria earlandi (Plummer) 
Cristellaria gibba (d'Orbigny)
Cristellaria lineara (Carsey)
Cristellaria reniformis (d'Orbigny) 

or Lenticulina reniformis .Cristellaria rotulata (Lamarck) or Lenticulina rotulata 
Cristellaria scitula (Berthelin)Cristellaria trigonata (Plummer) Clavulina angularis (d1 0rbigny) 
34 

... _ Cibicides refulgens (Montfort) or 
TruncatU:linarefulgens. Var. conica (Carsey)7 Discorbis correcta (Carsey) Frondicularia alata (d10rbigny) Frondicularia archiaciana (d'Orbigny) F~nndicularia christneri (Carsey)Frondicularia projecta (Carsey) Gaudryina atlantica (Bailey)Gaudryina bulleta (Carsey) Gaudryina filiformis (Berthelin)Gaudryina pupoides (d10rbigny)Globigerina cretacea (d'Orbigny)Globigerina rosetta (Carsey) Globotruncana area (Cushman)Gyroidina soldanl(d' Orbigny) Haplophragmoides ~--resembles H. 
canariensis (d1 0rbigny) Haplostiche ~ Lagena hespida (Reuss) Lagena incidenta (Carsey)Lagana Sulcata (Walker and Jacob)Lituola nautifoidea (Lamarck)Marginulina glabra (d1 0rbigny)Marginulina regularis (d' Orbigny) . Marginulina tumida (Reuss)Nodosaria affins (d1 0rbigny)Nodosaria alternata (Carsey)Nodosaria communis (d'Orbigny)Nodosaria comata (Batsch) Nodosaria farcimen (Soldani)Nodosaria filiformis (d1 0rbigny) Nodosaria fra i is (Carse¥)Nodosaria granti Plummer)Nodosaria intrasegma (Carsey)Nodosaria longiscata (d10rbigny) Nodosaria marla (Carsey)Nodosaria mucronata (Neugeboren)Nodosaria pauperata (d'Orbigny)Nodosaria pseudo-obliquestriata (Plummer) Nodosaria soluta (Reuss}
Nodosaria rad"icula (Linnaeus) or !:.. larva (Cars.ey) 
7. This species is a type fossil of the Taylor marl, not being found in the formations below or above it. 
Nodosaria texana (Conrad) . . Nodosaria verteb+alis (Batsch) ~­austinensis (Carsey) . Pleurostomella .§.E.· . Robulus cultratas (Montfort) --
Cristellaria cultrata Rotalia cretacea (Carsey) Rotalia soldanii (d1 0rbigny). Var. 
subangulata (Plummer) ~ Textularia globifera (Reuss)Textularia globulosa (Ehrenberg) 
· 	Textularia semicomplanata (Carsey) 
Tritaxis tricarinata (Reuss) 
Vaginulina legumen (Linnaeus)
Yitrewebbina sollasii (Ohapman) 8 

This list of sixty-seven species is not a 
complete one of the f oraminifera of the Taylor form­
ation as there are some fifteen species as yet not 
identified due to the lack of literature on the 
subject. 
For further data on the foraminifera of the 
Taylor marl a set of well samples was examined. It 
is possible that these well samples give an accurate 
distribution of bhe species throughout the section. 
' . 
The well is located in Bell County, and the data from 
it show a thickness of about five hundred and fifty 
feet in the Taylor, which is the same as in Travis 
County. 
8. The species included in this list were identified from the following bulletins: 
Carsey -Foraminifera of the Cretaceous of Central Texas; Plummer -Foraminifera of the Midway Formation of Texas: Cushman -Contributions: The Challenger Report: A set of two hundred species of f oraminifera loaned by Mr. Robert F. Cuyler, of The University of IDexas, Department of Geology. 
36 
·The hole was started practically at the contact of the Taylor and Navarro and went into Austin chalk at six hundred and twenty feet. F1fty~five samples from this well are available for examination. The following is a list of the foraminifera in each sample given in descending order with the corresponding depth of each sample from the tep of the well. 
37 

Foraminifera from the R. 
Bell County, 
Sample #1, 40 1 in depth 
Globigerina rosetta Globigerina cretacea 
#2, 701 Textularia globulosa Globigerina cretacea Globigerina rosetta Anomalina taylorensis Cristellaria rotulata Frondicularia projecta Frondicularia christneri Clavulina angularis ? 
#3, 95 1 Globigerina rosetta Globigerina cretacea Textularia globulosa Truncatulina refulgens 
#4, 105 1 Globigerina rosetta Globigerina cretacea Anomalina taylorensis Cristellaria rotulata 
#5, 125 1 Cristellaria lineara Anomalina grosserugosa Bulimina pupoides Nodosaria marla Nodosaria farcimen Truncatulina refulgens Textularia globulosa Globigerina rosetta Globigerina cretacea Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata 
R. Penn Hardy #1 
Texas 
#6, 135 1 
Cristellaria reniformis Anomalina grosserugosa Nodosaria intrasegma Lagena incidenta Truncatulina refulgens Globigerina rosetta Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Nodosaria texana (Microscopic, spherical 
body studded with short nodes; probably Ramulina 
SP.?) . -#7, 145 1 Frondicularia alata Vaginulina ~ Nodosaria ~ Anomalina grosserugosa Bolivina plaita Bulimina nupoides Lagena incidenta Truncatulina refulgens Bolivina latticea Globigerina cretacea Globigerina rosetta Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Nodosaria texana Textularia ~ Nodosaria communis Nodosaria filiformis Clavulina angularis ? 
#8, 155 1 Frondicularia alata Anomalina grosserugosa Textularia semicomplinata Lagena incidenta Nodosaria ~ Truncatulina refulgens Bolivina latticea Textularia globulosa Globigerina rosetta Globigerina creatcea Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Frondicularia projecta Textularia ~ Oiavulina angularis ? 
#9, 165' 
Frondicularia alata Anomalina grosserugosa Truncatulina re;fylgens Textularia globulosa flobigerina rosetta Globigerina cretacea Anomalina taylorensisOristellaria rotulata Tritaxia tricarinata Frondicularia projecta Nodosaria texana 
#10, 175 1 Frondicularia alata Nodosaria larva Nodosaria alternata Truncatulina refulgensGlobigerina rosetta Oristellaria gibba Globigerina cretacea !nomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Frondicularia christneri Nodosaria texana Frondicularia su. 
~~~~~~­
#11, 180 1 Frondicularia alata Anomalina grosserugosa Trucatulina refulgens 
Globigerina rosetta Globigerina cretacea Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Nodosaria texana Clavulina angularis ? Frondicularia .§..£:_ 
#12, 1841 Anomalina grosserugosa Boliviria plaita Bulimina pupoides Textularia globulosa Globigerina rosetta Cristellaria gibba Globigerina cretacea Anomalina taylorensis Oristellaria rotulata Tritaxia tricarinata Frondicularia projecta Gaudryina f iliformis 
#13, 194' Nodosaria marla Nodosaria farcimen Truncatulina refulgens Textularia globulosaGlobigerina rosetta Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Nodesaria texana 
#14, 1941 Nodosaria larva Anomalina grosserugosaTextularia semicomplanata Gaudryina putoidesGaudryina ~ leta Lagena incidenta Nodosaria laevigata Trunca.tulina refulgens Textularia globulosa Globigerina rosetta Cristellaria gibba Anomalina taylorensis 
Cristellaria rotulata 
. Tritaxia tricarinata Nodoearia texana Clavulina angularis ? 
#15, 205' Nodosaria larva Nodoaaria .§1?..:. Nodosaria sn. Anomalina grosserugosa Textularia aemicomplanata · Gaudryina pupoides Lagena incidenta Textularia globulosaGlobigerina rosetta Globigerina cretacea Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Frondicularia christneri Frondicularia projecta Nodosaria texana Nodosaria communis 
#16, 215' Nodosaria larva Nodosaria fil?..:_ Anom..alina grosserugosaTextularia semicomplanata Bolivina plaitaGaudryina bulleta Nodosaria farcimen Lagena incidenta Globigerina rosetta Globigerina cretacea Anomalina taylorensisCristellaria r-otulata Tritaxis tricarinata Frondicularia projecta Frondicularia christneri Nodosaria texana Lagena sulcata Nodosaria communis 
#17, 225 1 
Nodosaria larva 

Nodosaria sp. Anomalina grosserugosa Textularia semicomplanata Bolivina plaita Nodosaria farcimen Lagena incidenta Globigerina rosetta Globigerina cretacea Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Frondicularia projecta Nodosaria communis C1avulina aungularis ? Truncatulina refulgenw 
#18, 235 1 Cristellaria lineara Nodosaria fil?..:.. Nodosaria .§E.:_ Anomalina grosserugosaTextularia semicomplanataGlobigerina cretacea ~ Globigerina rosetta Nod6saria fragilis Bolivina plaita Bulimina pupoides Gaudryina bulleta Nodosaria maria Textularia globulosa Bolivina latticea Anomalina taylorensis Cristellar~a rotulata Tritaxia tricarinata Frondicularia christneri Nodosaria texana Clavulina angularis ? Frondicularia projecta 
#19, 245' Nodosaria fil?..:.. Anomalina grosserugosa Textularia semicomplinata Nodesaria alternata Bolivina latticea Textularia globulosa 
Qlobigeriria rosetta Globigerina cretacea Anomalina taylorensisCristellaria rotulata Tritaxia tricarinata Frondicularia christneri Nodosaria communis Clavulina angularis ? 
#20, 255 1 Nodosaria larva Nodosaria ~ Textularia semicomplinata Nodosaria marla Bolivina latticea Textularia globulosaGlobigerina rosetta Globigerina cretacea Anomalina taylorensisCristellaria rotulata Tritaxia tricarinata Nodosaria vertebralis 
#21, 265 1 Textularia semicomplinata Nodosaria marla Textularia globulosaGlobigerina rosetta Globigerina cretacea Cristellaria rotulata Frondicularia projecta 
#22, 272' 
Anomalina grosserugusa
Textularia globulosa
Globigerina rosetta 
Globigerina cretacea 
Tritaxia tricarinata 
Clavulina angularis ? 

#23, 275 1 Nodosaria marla Nodosaria alternata Anomalina taylorensis Oristellaria rotulata Tritaxia tricarinata Frondicularia christneri 
Clavulina angularis ? 
#24, 285 1 Gaudr!ina bulleta 
Textu aria globulosa Globigerina cretacea Anomalina taylorensisCristellaria rotulata Cristellaria gibbaTritaxia tricarinata Frondicularia christneri 
#25, 295' Globigerina rosetta Globigerina cretacea Anomalina taylorensis Crmstellaria rotulata Clavulina angularis ? 
#26, 305 1 
Textularia globulosa 
Globigerina rosetta 
Globigerina cretacea 
Anomalina taylorensis
Tritaxia tricarinata 
Clavulina angularis 7 

#27, 3351 
Gaudryina pupoides 
Textularia globulosa
Globigerina rosetta 
Globigerina cretacea 
Anomalina taylorensis 
Cristellaria rotulata 

#28, 3451 
Textularia globulosa
Cristellaria gibba
Globigerina cretacea 
Anomalina taylorensis
Cristellaria rotulata 
Tritaxia tricarinata 
Nodosaria texana 
Clavulina angularis 7 

#29, 3551 
Textularia globulosa 

Ariomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Frondicularia projectaNodosaria texana 
#365' Textularia semicomplanataBulimina pupoidesOriatellaria gibbaNodosaria texana 
#31, 3751 Text~laria globulosa Cristellaria ~ibba Anomalina tay orensis Cristellaria rotulata 
#32, 385 1 Bolivina plaitaTextularia globulosaAnomalina taylorensis Cristellaria rotulata 
#33, 390 1 Globigerina rosetta Globigerina cretacea Anomalina taylorensisCristellaria rotulata 
#34, 3901 Textularia globulosaGlobigerina rosetta Globigerina cretacea Anomalina taylorensis 
#35, 415 1 Textularia semicompl~nata Nodosaria marla Globigerina rosetta Globigerina cretacea Anomalina taylorensisCristellaria rotulata Tritaxia tricarinata Nodosaria texana 
#36, 420 1 Globigerina cretacea 
Anomalina taylorensisCristellaria rotulata 
#37, 430 1 Textrilaria globulosa Glob±gerina rosetta Globigerina cretacea Cristellaria rotulata Nodosaria texana 
#38, 4401 Globigerina cretacea Anomalina taylorensisCristellaria rotulata (small gastropod) 
#39, 450 1 Globigerina rosetta Globi~erina cretacea Anoma ina taylorensisCristellaria rotulata 
#40, 460 1 Textularia globulosaGlobigerina cretacea Anomalina taylorensisCristellaria rotulata Frondicularia projecta 
#41, 470' 
Gaudryina pupoides
Textularia globulosa
Globigerina rosetta 
Globigerina cretacea 
Cristellaria rotulata 

#42, 480' Bolivina plaitaTextularia globulosaGlobigerina cretacea Anomalina taylorensisCristellaria routlata Frondicularia projecta 
#43, 490' 
Nodosaria alternata 
Textularia globulosa 
Globigerina rosetta 

Globigerina cretacea Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata 
Frondicularia christneri Nodosaria texana Frondicularia !E..:.. 
#44, 5001 Bolivina plaita Textularia globulosa Globigerina rosetta G1obigerina cretacea Anomalina taylorensis Cristellaria rotulata Frondicularia christneri Nodosaria texana 
:j/:45, 510 I Globigerina rosetta Globigerina cretaces Anomalina taylorensis Cristellaria rotulata Tritaxia tricar.inata Frondicularia projecta 
' #46, 520 1 Globigerina rosetta Globigerina cretacea Textularia globulosa Anomalina taylorensis Cristellaria rotulata Tritaxia tricarinata Frondicularia christneri 
#47, 530 1 
Globigerina rosetta 
G1obigerina cretacea 
Anomalina taylorensis 
Oristellaria rotulata 

#48, 540 1 
Bolivina plaita 
Bulimina DUDoides 
Textularia globulosa 
Globigerina rosetta 

Globigerina cretacea Anomalina taylorensis Cristellaria rotulata 
#49, 550 1 Textularia globulosa Globigerina rosetta Globigerina cretacea Anomalina taylorensis Cristellaria rotulata Nodosaria communis 
#50, 560 1 G1obigerina rosetta G1obigerina cretacea Anomalina taylorensis Cristellaria rotulata Frondicularia christneri 
#=51, 580' Textularia globulosa Globigerina rosetta Globigerina cretacea Anomalina taylorensis Cristellaria rotulata Frondicularia christneri 
#52, 590 1 
Bulimina pupoides 
Nodosaria marla 
Nodosaria alternata 
Textularia globulosa 
Globigerina rosetta 
G1obigerina cretacea 
Anomalin~ taylorensis 
Cristellaria rotulata 
Tritaxia tricarinata 
Frondicularia projecta · 
Ammodiscus incertus 

#53, 600' 
Bolivina plaita 
Textularia globulosa 
Globigerina rosetta 
G1obigerina cretacea 
Anomalina taylorensis 

Cristellaria rotulata Tritaxia tricarinata Frondicularia christneri Ammodiscus incertus 
#=54, 610 I Nodosaria marla Textularia ~lobulosa Globigerina rosetta Globigerina cretacea Anomalina taylorensisCristellaria rotulata Frondicularia christneri P'!roD.dicularia ~ Ammodiscus incertus 
#=55, 6201 Bulimina pupoides Textularia globulosa Globigerina rosetta Anomalina taylorensisCristellaria rotulata Tritaxia tricarinata 
44 

The information obtained from this set of samples will be found to be of no great value other than a good index to the distribution of the common species through­out the Taylor section, since the slides available for inspection apparently did not contain all of the species that might be found in the Taylor marl. 
The data obtained from a study of the field samples affords several important facts to be noted. 
I 
First, that Truncatulina refulgens is a type fossil of the Taylor marl, since it is not present in any other formation of the Comanchean or Gulf Series of 
the Cretaceous. Second, that so far as known, Lituola nautifoidea is no't found in any horizon of the Taylor other than the four-foot stratum of clayey chalk ex­posed in the Del Valle Bluffs of the Colorado River. This should be a definite marker for subsurface in­vestigations. Third, that the change in lithology and larger fossils, found at the Taylor-Navarro contact, 
is accompanied by a similar change in micro-faunal remains. This is shown in the fact that below the contact, Taylor fossils are present while above the contact these disappear and typical Navarro species such as Vaginulina webbervillensis and Polymorphina 
communis are found. 
AN APPROXIMATE TAYLOR KARL SECTION 
DETER:flNED FR.OU FIELD DATA 
Scale 111 =100 1 

Massive blue marl : Gryphaea vesicularis in l ower half . 
Clayey chalk : Upper one-foot hard and fossiliferous ~ costata var . ~ Lituola nautifoidea . 
Massive blue marl containing two-inch layers of 
Ferruginous material not regularly spaced. (more 
abundant in lower part . ) ·t. 

?-~assive blue marl : ~req_uent specimens of ~pond­erosa present (rounded type) at the top of ~hich is found a one-foot stratum of Baculites oratus casts . First Ostrea Falcata appears at base ~ith Gryohaeaostrea sp . (afL G. Vomer. ) 
Massive glaring white Austin chalk or limestone. 
E. ponderosa present (angular type) . No O. falcata present . 

46 

BIBLIOGRAPHY OF THE TAYLOR MARL 
(STRATIGRAPHY) 

Publications having a bearing on the Taylor marl formation of the Cretaceous of Central Texas are listed herewith. M0 st of these articles refer to the Taylor marl of the Austin vicinity, while a few deal with the more remote regions of Texas and adjoining states, which have formations that may be correlated with the Taylor marl of the Austin region. While this bibliography is not complete, most of the literature on the Texas formation is included. The index volumes of the U. S. Geological Survey bulletins between the dates 1886 and 1928 have been checked for literature on the subject. Also, the bul letins of the American Association of Petroleum Geologists and other current publications have been examined for similar data. 
Adkins, W. S.: Geology and Mineral Resources of McLennan County, University of Texas, Bull. No. 2340, 1923. 
Baker, C. L.: The Cretaceous of West Texas and its 
~ ~ · ~
~~~­
Oil Possibilities, American Association of 
Petroleum Geologists, Bulletin Vol. 5, No. 1, 1921. 
Branner, John C.: Neozoic Geology of Southwestern Arkansas, Geological Survey of Arkansas, Ann. Rept., 1888, Pt. 2. 
Brucks, E.W.: The Geology of the San Marcos Quadrangle, Texas, A.A.P.G. Bull. Vol. 11, No. 8, August, 1927. 
Bybee, H. p. and Short, R. T.: ~Litton Springs Oil Field, University of Texas, Bull. No. 2539, 1925. 
Carsey, Dorothy Ogden: Foraminifera of the Cretaceous of Central Texas, University of Texas, Bull. No. 2612, 1926. 
Collingwood D. W. and Rettger, R. E.: The Litton Springs Oil Field, Caldwell County, Texas, American Association Petroleum Geologists, Bull. Vol. 10, No. 10, 1926. 
Dane, C. H. and Stephenson, L. W.: Notes .£!!. the Taylor and Navarro Formations .!£East-Central Texas, A.A.P.G. Bull. V0 1. i2, No. 1, January, 1928. 
48 

Deussen, A1e.xander: Notes Q!l ~Clays from Texas, U. S.. Geological Survey, Bull. No. 170, 1911. 
Dumble, E. T.: 1.h:£ Geology of East Texas, University of Texas, Bull. No. 1869, 1918. 
Ellisor, Miss_: ~Pecan Gap Limestone, American Asso­ciation of Petroleum Geologists, Bull. June, 1926. 
Fohs, F. Julius and Robinson, Heath M.: Structural and Stratiographic Data of Northeast Texas Petroleum Area, Economic Geology, Vol. 18, No. 8, 1923. 
Hammill, Chester A.:~ Cretaceous of Northwestern Louisiana, American Association Petroleum Geologists, Bull. Vol. 5, No. 2, 1921. 
Hill, Robert T.: Salient Geologic· Features of Travis County, Texas, Austin Statesman, December 15, 1886. 
Hill, Robert T.: Cretaceous Rocks of Texas, Geological Survey of Texas, First Ann. Rept., 1889. 
Hill, Robert T.: Geology of Parts of Texas, Indian Territory, and Arkansas Adjacent to the Red River, Geological Society America Bulletin., Vol. 5, 1894. 
Hill, Robert T. and Vaughan, T. W.: Geology of the Edwards Plateau and Rio Grande Plain Adjacent to 
Austin and San Antonio, Texas, U. S. Geological Survey, Eighteenth Ann. Rept., 1898. 
Hill, Robert T.: Geography and Geology of Black and Grand Praries, Texas, U. S. Geol. Surv., Twenty­first Ann. Rept., Vol. 7, 1899-1900. 
Hill, Robert T. and Vaughan, T. W.: Nueces Folio, Texas, 
U. S. Geol. Surv., Folio, No. 42, 1900. 
Hill, Robert T. and Vaughan, T. W.: Austin Folio, Texas, 
U. S. Geol. Surv. Folio No. 76, 1901. 
Hopkins, 0. B., Powers, Sidney, and Robinson, H. M.: The Structure of the Madill-Dennison Area, Oklahoma and Texas, U. S. Geological Surv., Bull. No. 736, 1916. 
Hull, J. P. D.: Notes on the Strati¢graphy of Producing Sands in Northern Louisiana and S0 uthern Arkansas (with discussion), Amer. Assoc. Petroleum Geologists, Bull. Vol. 7, No. 4, 1923. 
Liddle, R. A.: The Geology and Mineral Resources of Medina County, Texas, Univ. of Texas, Bull. No. 1860, 1918. 
Lonsdale, J. T.: Igneous Rocks of the Balcones Fault Region of Texas, Univ. Texas Bulletin No. 2744, 1927. 
(Taylor Marl in connection witt Pilot Knob, pp. 35-39) 
Matson, G. C.: ~Prospects 80 uth and Southeast of Dallas, U. S. Geol. Surv. Bull. No. 629, 1916. 
Matson, G. C.: The Caddo Oil and Gas Field, Louisiana and Texas, U. S. Geol. Surv. Bull. No. 619, 1916. 
Matson, G. C. and Hopkins, O. B.: De Soto-Red River Oil and Gas Field, Louisiana, U. S. GeoL Surv. Bull. No. 661, 1917. 
Matson,-G. C. and Hopkins, O. B.: Corsicana Oil and Gas Field, Texas, U. S. Geol. Surv. Bull. No. 661, 1917. 
Miser, Hue D.: Geology and General Topographic Features of Arkansas, Outlines of Arkansas Geology, Little Rock, Arkansas, 1920. 
Pace, Lula: Geology of McLennan County, Texas, Baylor Univ. Bull. Vol. 24, No. 1, 1921. 
Powers, Sidney and Hopkins, 0. B.: Brooks, Steen, and Grand Saline Domes, Texas, U. S. Geol. Surv. Bull. No. 736, 1916. 
Ries, Heinrich: The C1ays of Texas, Univ. of Texas Bull. No. 120, 1908. 
Rubey, W. W.: Wildcat Exploration in South Central Arkansas, Amer. Assoc. Petroleum Geologists, Bull. Vol. 6, No. 4, 1922. 
Sellards, E. H.: Geology and Mineral Resources of Bexar County, Texas, Univ. of Texas Bull. No. 1923, 1919. 
Sellards, E. H. Structural Conditions in the Oil Fields of Bexar County, Texas, Amer. Assoc. Petroleum Geologists, Bull. Bol. 3, 1919. 
Sellards, E. H.: The Producing Horizon in the Rios Well in Caldwell County, Univ. of Texas, Bull. No. 2239, 1922. 
Sellards, E. H.: The Luling Oil Field in Caldwell County, Texas, Amer. Assoc. Petroleum Geologists, Bull. Vol. 8, No. 6, 1924. 
Sellards, E. H.: Geologic Section in Milam County, Texas, Bureau of Economic Geoiogy, Univ. of Texas, July, 1925. 
Shuler, Ellis W.: The Geology of Dallas County, Texas, Univ. of Texas Bull. No. 1818, 1918. 
Stephenson, L. W.: Cretaceous and Eocene Contact, Atlantic and Gulf Coast Plain, U. S. Geol. Surv. Prof. Paner, 
4 
No. 90, 1914. 
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