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AYLOR

FALL 1987 ulletin No. 45

Stratigraphy ofthe (Upper ) and Its Source-Rock Potential in the East Basin MILTON A. SURLES, JR. ~~Creative thinking is more important than elaborate equipment--"

FRANK CARNEY, PH.D. PROFESSOR OF GEOLOGY BAYLOR GEOLOGICAL STUDIES BAYLOR UNIVERSITY 1929-1934

BULLETIN NO. 45

Objectives of Geological Training at Baylor Stratigraphy of the Eagle Ford Group The training of a geologist in a university covers but a few years; his education continues (Upper Cretaceous) and Its throughout his active life. The purposes of train­ ing geologists at Baylor University are to provide Source-Rock Potential in a sound basis of understanding and to foster a truly geological point of view, both of which are essential for continued the Basin professional growth. The staff considers geology to be unique among sciences since it is primarily a field science. All geologic research in­ cluding that done in laboratories must be firmly supported by field observations. The student is encouraged to develop an inquiring ob­ jective attitude and to examine critically all geological concepts and principles. The development of a mature and professional attitude toward geology and geological research is a principal concern of the departmen1. Milton A. Surles, Jr.

Cover: beds near the top of the Lake Waco Formation.

BAYLOR UNIVERSITY Department of Geology Waco, Texas Spring 1987

THE BAYLOR PRINTING SERVICE WACO, TEXAS , :~.~ j

CONTENTS Page Abstract ...... 5 Baylor Geological Studies Introduction•...... ••...... •...... 5 Purpose...... • ...... 5 EDITORIAL STAFF Location. . . . • ...... • ...... • . . . .. 6 Methods ...... • ...... • ...... 6 Janet L. Burton, Editor Previous Works ...... • • ...... • ...... 6 Acknowledgments ...... •. 7 O. T. Hayward, Ph.D., Advisor. Cartographic Editor general and urban geology and what have you Descriptive Geology . • ...... • ...... • ...... 7 Regional Stratigraphy...... • ...... • ...... 7 Joe C. Yelderman, Jr., Ph.D., Associate Editor East Texas. . . • ...... • ...... • ...... 7 hydrogeology Eastern Gulf Coast Basin ...... •...... 7 Southwest Texas, , and ...... 8 Peter M. Allen, Ph.D. Western Interior...... • ...... • ...... 8 urban and environmental geology. hydrology Summary .....•...... •...•...... 8 Eagle Ford Group ...... •...... •...... 9 Harold H. Beaver, Ph.D. Lithology. . . . • ...... • . . . .. 9 stratigraphy, petroleum geology Stratigraphic contacts ...... •. 9 Distribution and thickness ...... 9 Rena Bonem, Ph.D. Tarrant Sandy Clay ..•...... •...... II paleontology, paleoecology Lithology ...... •...... II William Brown, Ph.D. Stratigraphic contacts ...... •.....II structural tectonics Distribution and thickness ...... •...... II Britton Clay...... ••...... II Thomas Goforth, Ph.D. Lithology ...... •...... II geophysics Stratigraphic contacts .•...... 20 Distribution and thickness •...... •...... 20 Robert C. Grayson, Ph.D. Arcadia Park .....•...... •.....•..20 stratigraphy, conodont biostratigraphy Lithology ...... •.....•.....•20 and sedimentary petrology , Stratigraphic contacts ...... •...... •...... •..21 Distribution and thickness ...••...... •...... 21 Don M. Greene, Ph.D. physical geography, climatology, Sub-Clarksville Sand ...... •...... 21 earth sciences Lithology ..••.....•...... 21 Stratigraphic contacts ...... •...... 26 Don F. Parker, Ph.D. Distribution and thickness ...... ••.....•..••...... 26 igneous geology, volcanology, Summary .....•...... ••...... •....26 mineralogy, petrology Depositional Model ...... •...... 26 Pre-Eagle Ford Time•...... •...... •...... 26 STUDENT EDITORIAL STAFF Tarrant ...... 27 Britton Deposition ....•...... •...... 28 Todd Boring, Cartographer Arcadia Park Deposition .•..••...... •...•...... 30 Sub-Clarksville Deposition ...... 31 The Baylor Geological Studies Bulletin is published Summary •...... •...... 31 by the Department of Geology at Baylor University. Source-rock Potential of the Eagle Ford Rocks in the East Texas Basin ...... 31 The Bulletin is specifically dedicated to the dissemination , Petroleum Potential of Eagle Ford Rocks in the East Texas Basin ...... 37 of geologic knowledge for the benefit of the people of Tarrant Exploration Fairway ...... •.....•.....•...... •...... •..37 Texas. The publication is designed to present the results Britton Exploration Fairway ...... •...... 43 of both pure and applied research which will ultimately Arcadia Park Exploration Fairway •...... •...... 43 be important in the economic and cultural growth of Sub-Clarksville Exploration Fairway ...... 43 the State. ~I, Optimal Eagle Ford Exploration Faifways ...... •...... ••.... .43 ISSN 0005-7266 Conclusions ...... •..•...... •...... 44 Appendix I ...... •...... •...... •.44 Additional copies of this bulletin can be obtained from Appendix II ...... •...... •...•...... •....45 the Department of Geology, Baylor University, Waco, Appendix III ...... •...... •...... 49 Texas 76798. $1.05 postpaid. Appendix IV ...... •...... •...... •...... ••55 References .•...... •.....•...56 Index...... •...... 57 ILLUSTRATIONS Stratigraphy of the Eagle Ford Group Fig. Page 1. Index Map of the East Texas Basin ...... 6 (Upper Cretaceous) and Its 2. Stratigraphic Column for the Upper Cretaceous Eagle Ford Group and Surrounding Strata ...... 6 Source-Rock Potential in 3. Stratigraphic Correlation Chart of the Eagle Ford Equivalents in North America ...... 8 the East Texas Basin 4. Well 23, Bend Oil Corp. #1 Albowitch ...... 9 , 5. Isopach Map of the Eagle Ford Group ...... 10 6. North to South Stratigraphic Cross Sections D to D' Through F to F' ...... 12 7. West to East Stratigraphic Cross Sections A to A' Through C to C' ...... 14 8. Isopach Map of the Tarrant Sandy Clay ...... 16 Milton A. Surles, Jr. 9. Sand Isolith of the Tarrant...... 17 10. Isopath Map of the Britton Clay ...... 18 II. Sand Isolith of the Britton Clay ...... 19 12. Isopach Map of the Arcadia Park Shale ...... 22 13. Sand Isolith of the Arcadia Park Shale ...... 23 14. Isopach Map of the Sub-Clarksville Sand ...... 24 IS. Sand Isolith of Sub-Clarksville Rocks ...... 25 ABSTRACT 16. Regional Setting of the East Texas Basin During The Eagle Ford Group, of the upper Cretaceous Tarrant Deposition ...... 27 of dark gray, blocky , named the South Bosque Gulfian Series, is one of the most stratigraphically Formation. 17. Regional Setting of the East Texas Basin During complex clastic-dominated units in the East Texas basin. Geochemical analysis of Eagle Ford rocks throughout Britton Deposition ...... 28 At the type locality in County, Texas, the Eagle the East Texas basin indicates that the Eagle Ford Shales 18. Regional Setting of the East Texas Basin During Ford consists of bluish-black, carbonaceous are organically rich enough to be considered superior Arcadia Park Deposition ...... 29 ) exceeding 400 feet in thickness. In this area, the Eagle source-rocks for some of the petroleum found in Austin, 19. Regional Setting of the East Texas Basin During Ford includes the Tarrant (15 to 20 feet of brownish­ Eagle Ford, Woodbine, and Buda aged reservoirs. Sub-Clarksville Deposition ...... 30 gray ), the Britton (250 to 300 feet Within the petroleum generative province of East Texas, 20. Total Organic Carbon Isopleth, Eagle Ford, of interbedded brown calcareous mudstone), and the the Eagle Ford could have generated approximately 400 East Texas Basin ...... 32 Arcadia Park Formations (100 to 200 feet of dark gray billion barrels of oil. calcareous mudstone). 21. Total Organic Carbon Isopleth, Lower Eagle Ford, Significant petroleum reserves have been produced Eastward into the basin, the Eagle Ford thickens to from rocks of Eagle Ford age in the East Texas basin. East Texas Basin ...... 33 900 feet as the upper Eagle Ford acquires another unit 22. Total Organic Carbon Isopleth, Upper Eagle Ford, However, exploration for petroleum within Eagle Ford of terrigenous clastics on top of the Arcadia Park, called strata is at best very difficult. With the application of East Texas Basin ...... 34 the Sub-Clarksville Sands. Southward out of the basin, modified delta models, reservoir quality rocks can be 23. Gulfian Petroleum Production in East Texas ...... 35 the Eagle Ford thins by truncation and changes lithologic mapped in order to define exploration fairways for the 24. Compilation Map of Isopach Interval, Petroleum character; consequently the previously named subdivi­ individual units of the Eagle Ford. When all of these Generative Province, and Total Organic Carbon Isopleth ...... 36 sions are no longer recognizable. Near Waco, the lower fairways are compiled on the same map, two areas of 25. Sand Isolith of the Tarrant with Eagle Ford consists of mostly montmorillonitic clays major interest for Eagle Ford exploration become Exploration Fairway ...... 38 with disseminated calcium carbonate, called the Lake apparent. 26. Sand Isolith of the Britton with Waco Formation, and the upper Eagle Ford consists Exploration Fairway ...... 39 27. Sand Isolith of the Sub-Clarksville with Exploration Fairway ...... 40 28. Sand Isolith of the Sub-Clarksville with INTRODUCTION Exploration Fairway ...... 41 29. Compilation Map of the Eagle Ford 1 PURPOSE It Exploration Fairways ...... 42 The upper Cretaceous System in the East Texas basin aspects of Eagle Ford deposition. No study examines is dominated by terrigenous clastic deposits. Of these Eagle Ford rocks throughout the East Texas basin, yet rock units, one of the most complex is the Eagle Ford to properly interpret this major sequence a basin-wide Group, which exists throughout most of the East Texas study is necessary. basin and represents a long and complicated period in Some Eagle Ford facies have produced petroleum Cretaceous deposition. Various stratigraphic studies within the East Texas basin, while others have been based on local areas have described and attempted to recognized as probable source-rocks associated with interpret the Eagle Ford section, but few agree on major some of the largest oil fields in East Texas. However, 6 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 7

the Eagle Ford Group has been relatively ignored by previous works was undertaken, dealing with (I) the of not only this work, but also my academic career thus petroleum explorationists. Eagle Ford Group and associated rocks, (2) the structural far. Thanks are also extended to Robert C. Grayson, Therefore, the purposes of this investigation were: 1) development of the East Texas basin, (3) occurrence, Jr., and James L. McAtee, Baylor University, for their to describe the Eagle Ford Group throughout the East distribution and significance of dark organic shales, (4) technical advice and help in editing of this work. Others Texas basin; 2) to develop a depositional history of Eagle more general references on depositional environments, who offered helpful suggestions include Fred L. Ford rocks in east Texas; and 3) to relate this character oil generation and migration in the East Texas basin, Stricklin, Jr., Corp.; and Peter Allen, and history of the Eagle Ford to its source-rock and ~ and (5) techniques of organic analysis of Eagle Ford Joe C. Yelderman, and Rena Bonem, Baylor University. petroleum potential. and associated rocks. Sincere gratitude is expressed to the American To enhance readibility, this section of about fifty Association of Petroleum Geologist Research Commit­ LOCATION manuscript pages included in the original thesis, has been tee and the equivalent committee of the Southwest The area of interest is within the structural province t excluded from this published version of the report. If Section of that organization for Grants-in-Aid which of the East Texas basin (Fig. I). Rocks of the Eagle you wish a copy of this summary of previous works, helped fund the study. Thanks are extended to Paul Ford Group crop out on the western and northern simply write the Department of Geology, Baylor Doliver and Diane Barnes of Geomap Inc., for providing margins of the basin, marking the boundaries of the University, Waco, Texas 76798, or call (817) 755-2361. well data, Jackie Reed and Kurt Ritch with Arco Corp., study area in these directions. The eastern margin of for technical support and use of laboratory equipment, the basin is defined by the Sabine uplift, which was ACKNOWLEDGMENTS and to Mobil Oil Corp., for donation of geochemical a positive structural feature during Eagle Ford time Fig. 2: Stratigraphic column for the upper Cretaceous Eagle Ford I cannot begin to acknowledge all those who supplies. Finally, special thanks are extended to my (Granata, 1963, p. 66). The southern extent of the study Group and surrounding strata. Note the terminology and stratigraphic differences exhibited by the Eagle Ford throughout the East Texas contributed in some way to the preparation of this thesis. parents, Mr. and Mrs. Milton A. Surles, for their love, area is marked by the Angelina-Caldwell flexure which basin. However, my deepest appreciation is extended to O. T. devotion, and support, without which none of this would apparently was the shelf margin during Eagle Ford time. Hayward, Baylor University, whose advice and persistent have been possible. Beyond the flexure, the upper Cretaceous strata dip ian to late . Throughout most of the basin, encouragement was a fundamental factor in completion steeply into the Gulf Coastal basin. the Eagle Ford and Woodbine are often undifferentiated and rest unconformably on the . The overlies the Eagle Ford throughout the ARKANSAS basin and the contact between the two is generally unconformable along the updip margins of the basin. DESCRIPTIVE GEOLOGY METHODS The methods used in this investigation included a field The Eagle Ford Group and its temporal equivalents Generally, the Eagle Ford decreases in carbonates up reconnaissance, an examination of electric logs, are complex litho-stratigraphic units representing a section and increases in terrigenous clastics in the same laboratory analysis of cuttings from wells drilled in the ) significant portion of the upper Cretaceous (Gulfian) direction. TEXAS section of North America. The complexity of the section basin and outcrop exposures, and a review of the I literature. is reflected by the numerous changes in lithology, EASTERN GULF COASTAL BASIN Outcrop localities were examined for lithology, fauna, character, and stratigraphic nomenclature existing not Eastward out of the East Texas basin, Eagle Ford sedimentary structures, and stratigraphic relationships only within the East Texas basin, but also between North rocks pinch out both on the outcrop and in the sub­ as indicators of depositional models for the group. American Cretaceous basins. To understand Eagle Ford surface, apparently as a result of and non­ Representative sections were described for the different rocks, it is necessary to consider both regional and local deposition related to the Sabine uplift (Granata, 1963, formations. These sections were used to correlate Eagle aspects of Eagle Ford deposition. Therefore, the purpose p. 65). However, a narrow band of Eagle Ford rocks Ford rocks along the outcrop with electric log profiles. of this section is to describe rocks of Eagle Ford age up to 100 feet in thickness occurs both in the sub-surface Well logs were used to establish thickness and in North America, and then to describe in greater detail and as a narrow outcrop belt in southwestern Arkansas, character of the units within the Eagle Ford. This the nature and distribution of Eagle Ford rocks in the known as the Pittsburg syncline (Stehi et al., 1972, p. information was used to generate isopach maps, sand East Texas basin. 39). A change in character of the Eagle Ford in this area, from dark laminated shales of the East Texas basin LITHOLOGY \:!I!!!e isolith maps, and stratigraphic cross-sections which aid _ DeMOTIS OUTCROP OF REGIONAL STRATIGRAPHY to blue calcareous shale with abundant red clay, probably a .lUSTIN CH.lUI in understanding correlation and distribution of the Eagle Ford. As a starting point, the East Texas basin is briefly indicates proximity to a source of terrigenous clastics mm =E:OII~CROP 0. Laboratory analysis consisted of organic carbon described first. The Eagle Ford sediments are then traced (Stehi et ai., 1972, p. 46). eastward out of Texas into the Eastern Gulf Coastal Eastward, in northwestern , the Eagle Ford DE"ons OUTCROP OF analysis of samples by use of a Leco Automatic Carbon • WOOllllIft Determinator in combination with a Leco Induction basin, then southward out ofeast Texas into , thins to less than 80 feet, and consists ofdark fossiliferous Furnace. This information provided data to generate Mexico, and west Texas. Finally a comparison is made shales interbedded with greenish, tuffaceous, chloritic i an isopleth map of organic carbon for the Eagle Ford with the upper Cretaceous equivalents of the Western sands and greenish bentonitic shales (Hazzard, 1939, p. group. This map, combined with distribution of Interior region. 137). Continuing eastward, the lower-most of the upper Cretaceous section in the Eastern Gulf o 10 100 producing fields, was used to draw conclusions about .... 1ft ...... ' the source-rock potential of Eagle Ford rocks. ) EAST TEXAS region is along the contact of the Tuscaloosa (equivalent The literature review included all works pertaining Eagle Ford rocks in east Texas are dominated by dark to Woodbine rocks) and overlying Eutaw Formations Fig. I: Index map of the East Texas basin. The basin is bounded to Eagle Ford rocks of the East Texas basin, selected bluish-gray shale which varies in thickness from 200 to (possibly equivalent to lower Austin rocks) (Fig. 3) on the north and west by the outcrop belt of Eagle Ford rocks, on works on organic geochemistry, and references on 900 feet. It is thickest near the center of the basin and (Stephenson and Monroe, 1938, p. 1641). Thus, rocks the east by the Sabine uplift, and on the south by the Angelina-Caldwell thins towards the southern and eastern margins of the of Eagle Ford age are generally missing from the Eastern flexure. structure, oil production, sedimentation, and deposition of organic muds and anoxic shales. basin. The Eagle Ford also thins eastward along the Gulf Coast. northern outcrop and southward along the western Significant to the history of Eagle Ford deposition Stratigraphically, rocks of the Eagle Ford Group are outcrop towards the boundaries of the basin. While the are volcanic centers near Murfreesboro, Arkansas, which of upper Cretaceous Gulfian Series (Fig. 2). The age PREVIOUS WORKS dominant lithology is shale, the section contains were active during early Gulfian time (Ross et aI., 1929, of Eagle Ford rocks ranges from middle-late Cenoman- In the progress of this study an extensive review of interbeds of sandstone, limestone, and bentonite. p. 175). These centers have been suggested as possible EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 9 8 BAYLOR GEOLOGICAL STUDIES

with Western Interior equivalents including the Benton Euro_ 1-'·...,,'r.1 South_ Central G_I Davis Norlham Del Rio. Austin E.sI Soulham Easlern Gull AUSTIN Scale Utah ColOrado Monl."" Plains MOuntains, lX. lo!e.1eo Texa, TIl... Texas Arkansas Region Shale, Indianola Group, Mancos Shale, and Colorado Sa_ Shale. """lJ. NI_a.. San Carlo. Austin Eul_ Coniacian I Austin Austin Tokio MARIBEL formation formation Austin Chalk formation Chalk Chalk tormatlon Sandslone Chalk EAGLE FORD GROUP The Eagle Ford Group ofthe EastTexas basin consists Langlry I 'f ~ of as much as 400 feet of bluish-black laminated clay Mancos warm BELLS b> Carlile (") distributed throughout the basin. The type locality for shale auk II' Tilronlan I Eagle Ford rocks is at the townsite of Eagle Ford, t Upper ~ tc: approximately 7 miles west of Dallas, in Dallas County, ,t" iI" i 3 II" Texas (Sellards et aI., 1932, p. 422), where it is sub­ ! - Greenhorn ~ divided into the Tarrant Sandy Clay, the Britton Clay, S.ndstone I Graneros I, and the Arcadia Park Shale (Fig. 2) (Sellards et at, 1932, p. 425). Eastward into the basin, the upper Eagle Dakola I~~~~ I~. ARCADIA PARK EAGLE FORD C«!omanlan ..ndslone Ford expands by the addition of the Sub-Clarksville b ) , ,I[ U'.'"'' , . .,,. .. ,,.1,.,.,,, L'. r ,. T...... ""'.. Sand (McNulty, 1966, p. 379). Because these subdivisions formallon group are the most complete, they form the framework of the Wij/~ij///~~//~ description for this section. Each unit is described in IAlter Lonsdale, 1927. Stephenson, _, and Passagno. 19691 terms oflithologies, stratigraphic contacts, and thickness and distribution. Fig. 3: Stratigraphic correlation chart of the Eagle Ford equivalents in North America (after Lonsdale, 1927, Stephenson, 1938, and Pessagno, BRITTON 1969). Eagle Ford rocks of east Texas are equivalent to several rock units in North America including: the , the Chispa LITHOLOGY Summit Formation, the Benton Shale, the Colorado Shale, the Mancos Shale, and the Indianola Group. Note the unconformity which exists in the Eastern Gulf region representing Eagle Ford time. Eagle Ford rocks of east Texas are dark bituminous laminated clays (Shuler, 1918, p. 15). On the outcrop near Dallas, the lower two-thirds of the formation TARRANT sources ofthe volcanic ash, now represented by bentonite into two units: I) a lower 500 feet of thin-bedded buff consists mostly of blue and black laminated shale which seams in the Eagle Ford of east Texas (Miser and Ross, to gray calcareous muds, calcareous silts, marls, and grades upward into a brown weathered section of 1925, p. 123). chalks; and 2) an upper 1500 feet ofdark gray calcareous ferrigenous glauconitic sand interlaminated with clay. WOODBINE mudstone with occasional limestone concretions and Eagle Ford rocks are not normally fossiliferous, though SOUTHWEST TEXAS, MEXICO, AND WEST TEXAS nodules. The Chispa Summit Formation rests discon­ fossiliferous beds do occur in certain outcrops (Gordon, The Eagle Ford rocks thin southward from Dallas formably on the Buda Limestone and is conformably 1911, p. 17-19). North and south of Dallas, the clay Fig. 4: Well 23, Bend Oil Corp. #1 Albowitch. The Eagle Ford can be subdivided into four formations in this well: the Tarrant, the Britton, to Austin, apparently because ofnon-deposition of lower overlain by the San Carlos Formation of Austin age. in the Eagle Ford becomes less sandy as the outcrop The most complete section of Eagle Ford age rocks is the Arcadia Park, and the Sub-Clarksville which can be further units and truncation of upper beds (Brown and Pierce, belt narrows in both directions (Stephenson, 1927, p. subdivided into the Bells and Maribel Members. Note the lithologic that present in this area, ranging from late Cenomanian ~ 1962, p. 2144), possibly as a result of concurrent uplift 6; Stephenson, 1928, p. 488). Northward from Dallas, interpretations of the log signatures including sand, limestone, and in the Llano area (Stephenson, 1928, p. 487). At Austin, through late Turonian age without any detectable hiatus. the Eagle Ford continues as dominantly black laminated shale. Eagle Ford thickness is under 42 feet, and consists of clay. Eastward, near Sherman, sandstone stringers thin bedded buff marls and chalks, unconformably WESTERN INTERIOR become more common and increase in thickness and However, in the southwestern portion, beyond the resting on Buda Limestone and unconformably overlain The Eagle Ford Shale of the East Texas basin number (McNulty, 1966, p. 375). Southward from pinchout of Woodbine rocks, the Eagle Ford rests by the Austin Chalk (Pessagno, 1969, p. 63). correlates well with several units of the Western Interior Dallas, the Eagle Ford thins as upper beds are truncated directly on Buda Limestone, and the contact marks the Southward beyond Austin, the section again thickens (Fig. 3). Among these, the Benton Shale (Brown and Pierce, 1962, p. 2144). The silts and sands Comanchean-Gulfian unconformity. The Eagle Ford to 112 feet near Del Rio, where it consists of black shales is perhaps the nearest correlation. Other groups from typical of the northern basin are conspicuously absent, Group is overlain by the Austin Group in all portions subdivided into a lower Rock Pens Member, and an the Western Interior that also correlate with Eagle Ford and carbonate-rich rocks dominate the lower Eagle Ford of the basin. Throughout the basin, this contact is upper Boquillas Formation. The contact between the sediments include: the Indianola Group of west-central near Waco (Brown and Pierce, 1962, p. 2137). believed to be unconformable, with rocks of upper Boquillas and Austin Chalk is conformable and Utah; the Mancos Shale of southwestern Colorado; and Within the basin, the Eagle Ford is recognized on Turonian and lower Coniacian age missing through non­ gradational (Pessagno, 1969, p. 62). Serpentized rocks the Colorado Shale ofcentral Montana(Moreman, 1942, electric logs by a drastic decrease in both spontaneous deposition and truncation. occur as masses in the Eagle Ford from this area p. 195). potential (Sp) and resistivity in relation to the overlying (Lonsdale, 1927, p. 45), and these have been suggested and underlying rocks (Fig. 4). The contact between DISTRIBUTION AND THICKNESS as sources for bentonites in the Eagle Ford of southeast SUMMARY Woodbine and lower-most Eagle Ford rocks is normally An isopach map of the Eagle Ford Group shows a Texas. Following a late Woodbine erosional period, drawn at the base of the first shale section above the thick sequence of Eagle Ford rocks in the northcentral Westward into Mexico, the Eagle Ford equivalents Eaglefordian seas inundated several areas of the upper-most sand of the Woodbine. The upper contact portion of the basin, near area A (Fig. 5). The Eagle thicken to 188 feet and are termed Boquillas Formation. continental United States. In east Texas the sediments between the Eagle Ford and Austin is drawn at the top Ford gradually thins southward, due not only to the Disconformably overlying the Buda Limestone, the deposited from these seas consisted of 200 to 900 feet of the last shale section below the lowest known absence of the Tarrant and Sub-Clarksville Formations, Boquillas is divided into: I) the lower Rock Pens of dark bluish-gray shale interbedded with sandstone, limestone member ofthe Austin group. Occasional peaks but also as a product of gradual thinning of the Britton Member, consisting of 150 feet of gray calcareous limestone, and bentonite. The Eagle Ford is generally in both Sp and resistivity occur in the Eagle Ford section and Arcadia Park Formations (Fig. 6). Thinning along siltstones, mudstones, and limestone flags; and 2) the absent in the Eastern Gulf Coast, where Eagle Ford 1 throughout most of the basin, representing small the Belton high is reflected at area B, possibly indicating upper Langtry Member, consisting of 38 feet of buff time is represented by a major unconformity. In the carbonate and sand bodies in the dominantly shale positive expression of this feature during Eagle Ford calcareous marlstones, marls, and thin-bedded chalky East Texas basin, Eagle Ford rocks thin southward to section. time. The Eagle Ford thins rapidly eastward out of the . The Austin Chalk conformably overlies the the latitude of Austin, then thicken toward Del Rio. basin and is not present over the Sabine uplift, area Boquillas in this area (Pessagno, 1969, p. 61). Thickening continues westward into Mexico, and west STRATIGRAPHIC CONTACTS C. Another thickening of the Eagle Ford occurs south Westward into the Davis Mountains of west Texas, into the Davis Mountains, where it reaches a maximum Eagle Ford rocks unconformably overlie Woodbine of the Sabine, where the strata plunge into the Gulf rocks of Eagle Ford age are termed the Chispa Summit thickness of 2000 feet. strata along the margins of the East Texas basin. Coast basin. Formation, consisting of 2000 feet of strata subdivided Eagle Ford sediments ofthe East Texas basin correlate

l IO BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 11

The northward thickening is associated with the the northcentral portion of the basin, near Area A (Fig. northern portion of the central East Texas basin, 8). The isopach also shows the Tarrant pinching out probably indicating more rapid sedimentation possibly southward and eastward, which appears to be due to accompanied by salt withdrawal and subsidence. The a combination of thinning and facies change (Figs. 6 greatest thickness of is also coincident with and 7). Thinning occurs in the northwestern portion of an increase in sands in the Eagle Ford, while the southern the basin in area B, probably a product of slower thinning is accompanied by an increase in carbonates, sedimentation rates. suggesting that clastic influx was occurring from the Individual Tarrant sands average less than 10 feet in north during Eagle Ford time. This northern influx thickness. On a sand isolith, areas of thick sand increased the overall thickness of the group and accumulations reflect staCking of sands rather than preferentially excluded carbonates in the northern thickening of individual sand bodies (Fig. 9). Two portions of the basin. buildups of sand occur in the Tarrant, one originating in the north, near area A, and one from the west, near TARRANT SANDY CLAY area B, indicating two sources of clastic influx during 59 Lithology Tarrant time, and also that the shoreline was very near •,-. The lower-most unit of the Eagle Ford, the Tarrant the present outcrop line. Tarrant sand accumulations -- Sandy Clay, consists of 15 to 20 feet of gray to brownish­ reach a maximum combined thickness of 40 feet where .61 63. gray calcareous sandstone interbedded with brown Tarrant sediments are more than 200 feet thick and the ".,.:.... 6J siltstone, brownish limestone, and shale. The base of shale-to-sand ratio is 5: l. Thus even during the

---"'"",""1 ,"""" #...." the Tarrant characteristically has a zone of reworked deposition of the Tarrant rocks containing the most sand, 94· ./ mudstone pebbles, siderite, alunite, borings, glauconite, the dominant sediment was mud . • 101 ·92 ,'" .100 and black phosphate nodules (Brown and Pierce, 1962, The distribution of the sands in area C resembles sand 95 ) p. 2135). Throughout Johnson and Hill counties, the· distribution from a bird foot delta complex, indicative .. 102• 103. basal Tarrant contains "water worn" sandstone pebbles, of low destructive energy. The relationship between the ·93 which are as much as two inches wide in their longest accumulations of sand in areas A and C is best explained I C __" , .104 dimension (Sellards et aI., 1932, p. 423). by the transgressive nature of the lower Eagle Ford. ,- -- _.- 99·' On electric logs the Tarrant formation is represented Distributary pathways in area C were established early ( .96 by a sandy shale section above the sand-dominated in Tarrant time. As the Eaglefordian seas transgressed ',- ...... " ""- ... '- .., Woodbine signatures and below the shale-dominated into the East Texas basin, the distributary pathways , ~ signatures of the lower Britton (Fig. 4). The contact retreated to area A. The thicker sequence of sand at ,.,,:...... \ .97 • 98 .) 1~7 .110 -. ''-. -, \ 108 between the Woodbine and Tarrant is drawn at the base area A is probably a function of a longer period of <' 112 ',. e( of the sandy shale signature above the last true sand delta stabilization. './109. of the Woodbine. The contact between Tarrant and The restriction of Tarrant carbonates to the north­ .113 Britton is indicated by the abrupt transition from sandy western portions of the basin corresponds with generally "'" '-'!...'I­ shale to shale signatures. Occasional carbonates occur less sand in these areas, suggesting development of near the Tarrant-Britton contact, usually in lower Britton marginal embayments between the sand distributaries. strata. The sandy shale log signature of the Tarrant reflects BRITTON CLAY varying permeability caused by small sand stringers Lithology throughout the section (Cross Sections A - A' and D On the outcrop near Dallas, the Britton Clay consists - D'). Carbonates are generally restricted to the western of 250 to 300 feet of dark brown laminar calcareous and southwestern portions of the basin, probably mudstone interbedded with thin impure beds of reflecting reduced clastic sedimentation farther from the limestone and siltstone. Southward, the Britton thins deltas (Cross Sections B - B' and F - F'). and its upper beds are truncated (Brown and Pierce, o 50 1962, p. 2144). South of Hill County, the Britton assumes Stratigraphic Contacts the name Lake Waco (Pessagno, 1969, PI. 9). The Lake Scale In Miles At the Eagle Ford type locality near Dallas, the contact Waco is subdivided into the Bluebonnet Member, the C.1.100 Feet ISOPACH MAP: EAGLE FORD GROUP N between the Woodbine Group and Tarrant formation Cloice Member, and the Bouldin Member. Generally, is unconformable, indicated by a sharp lithologic change the Lake Waco consists of mostly montmorillonitic clays and the presence of reworked material in the base of with considerable disseminated calcium carbonate, the Tarrant, often marked by white alunite nodules numerous limestone beds near the base and top, minor (Stephenson, 1929, p. 1327; Stephenson, 1946, p. 1764). seams of bentonite, and rare kaolinitic clays (Burkett, It is not known to what extent the unconformity extends 1965, p. 28). Bentonites are concentrated in the Britton into the sub-surface. The Tarrant is overlapped from where at least 34 bentonite seams have been reported the south by the Britton Clay (Brown and Pierce, 1962, within 70 feet of strata (Brown and Pierce, 1962, p. 2135). p. 2144). The contact between the two is considered to On electric logs the Britton is recognizable by a be conformable, showing both gradational and abrupt distinctive signature indicative of shale (Fig. 4). The lithologic changes (Figs. 6 and 7). upper contact ofthe Britton with the lower-most Arcadia Park was recognized by a rapid decrease in carbonate Fig. 5: Isopach map of the Eagle Ford Group. The Eagle Ford thickens in the northern portion of the basin near area A, and thins southward accompanied by thinning along the Belton high, area B. The Eagle Ford is absent over the Sabine uplift, area C, apparently due to erosional Distribution and Thickness in upper Britton to a shale-dominated lower Arcadia removal after deposition. The Tarrant thickens basinward to over 200 feet in Park. This decrease was marked by a negative kick in 12 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 13

14' 153 28 148 52 . 3' Ap...CO Inc. Glan Ro•• Co . Htntof'l .... d Haga, . . <# 1 Jo••phl". 51ro"., .1-A C.ntra. Coal and Coke Shell on Co. #, G.,dne, Frank Gra••• as KB 348 K8 388 EST 125 '* 1 "edge Jon•• .1 ..."nnota 30 £5T559 . i KB .'1 l ••be" 8 ...d 0:1111*,. et at *1 Simpson NORTH I DF 501 SOUTH D D'

SUB-CLAAKSVIlLE SlJB.CI.ARI

STRATIGRAPHIC CROSS SECTION D TO D'

81 138 . 88 . 140 23 . Burna" OU Lon. St., Prod . . Con"".n'.' 011 ." 1 .... Roga,. $Inel••, Oil and a.. •• '* 1 01.,. Kltlo"gh #2 Roya' National Bank Bal'''':1 011 Co,o. 18 . KB 282 ." 1 Iran. Wal.t KB 428 D. H. a,rd KD 240 GL 218 .,. 1 A'bowltch . #1 D. H. Byrd DF 400 Co... DrUUna #, John Coa.e DF .054 2' DF 4.7 . SOUTH NORTH o WId D DrUUng *1 Mo,lon EST .0. E' · ~"~M-'~1'~ __,_ ~:-.~~..- ~tlL ~n __;~-"--- ==1[ li~

TARRANT TARRANT

TARRANT

STRATIGRAPHIC CROSS SECTION E TO E'

132 138 . 73 119 . GI.n H. McCarthy 5 10 . . ra II aa 'nt. Pat. Carp• #1 HoJllday L. D. . . C.'n 71 Humbta Oil and A.fif'int '" 1 Hintop A••art KII 342 Humble Oil and Refining Rotar, DrUUng .1 F. W. Patak "'1 M..... K8 470 .1 Elln "nd.,aon ",1 T. A.....wl. GL 521 . AMOCO ProducUon DF S11J K8 589 Co. EST 523 '*' J. D. Cunningham SOUTH NORTH K8 308 F F' sua·CLAfh($Vli S1J

BRITTON BRmON

TARRANT f STRATIGRAPHIC CROSS SECTION F TO F'

NORTH TO SOUTH STRATIGRAPHIC CROSS SECTIONS D TO D' THROUGH F TO F'

FOR TH£

STRATIGRAPHY OF THE EAGLE FORD GROUP ;!~ "(JlTlCAL ••AGCM:.Afl.ON (UPPER CRET ACEOUSl ~h .... .~ s AND ITS SOURCE-ROCK POTENTIAL ~ . MOIUZ<*TAL $CAL[ IN THE EAST TEXAS BASIN IIIifIlllNLU

Fig. 6: North to South Stratigraphic Cross Sections 0 to 0' Through F to F'.

.. 14 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 15

5 • 23• ~ou Bond 011 Co. 37 33 #, -.on #1 A_ell • HIlI _ • McLean KI 599 OF 4110 "... 01..... 44 #1 J.clt.on Goodman • .1 ...... - O.lII) Rock OU KI 471 DF 292 WEST #1 II. ShIrt.y EST 580 EAST A SUB-Ct.ARI(SVtlLE A'

ARCADIA PARK , BRITION .. TARRANT 'fARitWf

STRATIGRAPHIC CROSS SECTION A TO A' 73 84 82 • 88 Gael., _• K.mp L. D. Cilln D. H. Byrd • #1 F. W.P.I_ #1 D. H. 8yrd ..... on Co. #1 Allen GL 527 DF 554 #1 Adelia loDey DF 319 WEST 391 EAST B SUS-CLAAKSVlLlE B' ARCADIA PARK LIMESTONE BRITION­ TARRANT 1.1

STRATIGRAPHIC CROSS SECTION B TO B' 125 • 158 Ha"y Sh...... 151 #1 D. lit. Woodfin 138 140 KB 373 Shell Oil Co. • • .. 2 Soulhland Paper Mills T.a.. Inl. Pet. Corp. SinClair 011 and Ga. KB 304 WEST #1 Hili Top R••ort #1 Ir.ne Waist KB 470 Gl 213 EAST C C' ARCADIA PARI( BRITION BRITTON ARCADIA PARK

STRATIGRAPHIC CROSS SECTION C TO C' WEST TO EAST STRATIGRAPHIC CROSS SECTIONS A TO A' THROUGH C TO C'

FOR THE

STRATIGRAPHY OF THE EAGLE FORO GROUP (UPPER CRETACEOUS) AND ITS SOURCE-ROCK POTENTIAL IN THE EAST TeXAS BASIN 8 ~ 8 VUTICAL UAGGfAATfON i~ ! '05' a! c ... ~ 8 i; 100 10 tS 20 HMIZQIiIl7AL SCALE Fig. 7: West to East Stratigraphic Cross Sections A to A' Through C to C'. "'" ..'L£S 16 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 17

Outcrop Belt A Outcrop Belt Eagle Ford Rocks ..... Eagle Ford Rocks ..... ~

36-

44. 44.

---,--,-­ \' 45. 56.\ ---­ 55 i', 58 59 • -. ,. ..-! .J 60 • .,., 1...­

.61 63 • _61 63­

~ 62 .__ ._...... ,.­ 6~ 69. .__ ._. - ,.­ ---", I , ".., .. I , -...., ...... ;- I .101 74 ;- I .101 ·92 / -92 (.100 -/ ,/_100 / 95 ) 95 ) , 103• 103 . 102 -, 102 9d ·93 • \ 77. . 911 -93 - - / ) I 85 -, 75 / I" ___ • _ • ....:.. ' ·104 \ {S> , I,. _ _. __ ....:. -104 .' • / . \ .-," \. " < .96 99·\ \ /-­ \ 120- < .96 99-, 114 '/' .118 " .86 89 , 87 89 87 " "\. '"\--...... \ \ .121 -.. , \ - - • \ - - , , •117 " . 122· ./ -( _ .-­-, 90 \ 97 Il5- \ 122­ / '( .-­-, 90 \ 97 , ,...,.. ,­ "',. ,. """," ,­ - ...... • 98 - 98 107• > 1l9-\ . • /' ­ _ \. 148 \.. ,./ "­ J , • \. 148 \. ,./ "-, J 107 / \ \ / 137 , .145 149. <' ·1l2 "­ / / 137 \ .'45 14ge < -112 ...... -", ) ,;.,. .. " \ .108 \ .. \ _108 \ /1 135• /1 135• ) ;.,." 14;;' .. I .. ..( 109-< .111 123 \ \ ,/ ( " . \ / ( 147 "", " '..( 109-<, 138. ( / 152·' 113 125 ,/ • 125 ~ ...... 138. ( - / 152·' 113 .131 . (146/ ,­ , I • ,/ 131 ,. , /,/ ( 146" " - , 136 __ ­ ...... • /150 ,"-', - -_:-_--1---­ .136 __ .. _ "" ...... '"' • /' 1S0 ' - ~ ...... - .. \ /" ·129 \/./'\ ·129 \ • ,­ " /1 • / \' '/1 • / ~. \/ l: ~ ... ..,/ 140 l ~. " • ,.., .. -~- I ... ..,/ 140 \ ". ..,. - .. - • .130 ,. .130 ;/ _ / / 15 .' 161 .. 126• ,if • j.,/ I 151 / 154 , _157 16~'" 161 163• 126• \ /' ,'( j.. I 151_ 4 ',157 160'" 1163 /', 139 - 144·­ • / • , • L ...-­ " /' \ ' 155 , 139 • 144·'" /' / 155. - ' • . \. -162 1;4 L - ...-­ I \, ' 158 \. 162 / 134, - I { 158 / 127. , 127. , . \ - \ • 10 , • •• 141 _ 156. I ·159 \ • 142 '156 , -159 •• 141. I • , I 153 \ 133 133 1 '­ " ) 1 ••153 '-_, 143 I'. 143 I '-. \ - \ •

o 50 o 50 Scale In Miles Scale In Miles ISOPACH MAp: TARRANT C.I.10 Feet SAND ISOLITH MAP: TARRANT N CoL 50 Feet N

Fig. 8: Isopach map of the Tarrant Sandy Clay. Tarrant rocks thicken in the northcentral portion of the basin, near area A. Note the thinning Fig. 9: Sand isolith of the Tarrant. Moderate sand buildups occur in two areas within the basin, one originating in the north near area A, of the Tarrant in area B, and the southward and eastward limit of the unit, apparently a product of thinning and facies change. and one in the west near area B. Note the sand distribution pattern in area C resembles a bird foot delta complex. 18 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 19

Outcrop Belt EagleFOrd~

III • lb•

44. 44.

45. 45• .-._----­57 " •58 59• 60.. " ,-' ...- .. ,-. I ...... ,. -,' 70' .61 • "118 • 6l • 111 113 • 119·' 62 1 -. I 62 I ~--_

o 50 100 o 50 Scale In Miles C.I.50 Feet ISOPACH MAP: BRITTON Scale In Miles N C.I.10 Feet SAND ISOLITH MAP: BRITTON N

Fig_ 10: Isopach map of the Britton Clay. Three areas of thickening of Britton strata occur in the north near areas A and B. Southward Fig. II: Sand isolith of the Britton Clay. Six areas of major sand accumulation are visible, A, B, C, D, E, and F. Of these, a highly complex thinning of Britton rocks to less than SO feet occurs at the Angelina-Caldwell flexure, area C. Note the absence of Britton strata over the sand body originates in area B and extends to area A. The elongate distribution of sand in area C could be due to paucity of data. Sand Sabine uplift, area D, apparently due to erosional removal after deposition. distribution near area D resembles a bird foot delta complex. Sand accumulations at areas E and F are not related to any major points of clastic influx and are apparently the result of turbidity transport related to the Angelina-Caldwell flexure. 20 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 21

the resistivity on the electric logs, which is the top of contact between the two is unconformable along most Bosque is completely noncalcareous. The upper portions uplift as the Eagle Ford sediments plunge into the Gulf the Britton. of the margins of the basin, with portions of lower to of the Arcadia Park contain Tafrs (1891) "fishbeds." Coast basin. The increase in resistivity on electric logs reflects the middle Turonian rocks missing (Pessagno, 1969, p. 69). Two distinct "fishbeds" occur in the upper Eagle Ford, Arcadia Park Sands are distributed throughout most increased limestones and disseminated carbonates The stratigraphic hiatus of the Britton-Arcadia Park a sandstone "fishbed," terrigenous in origin showing of the East Texas basin (Fig. 13). The increase in present both on the outcrop and in the sub-surface. unconformity also increases southward along the fluvial aspects, and a limestone "fishbed," distinctly thickness and distribution of large sand bodies in the Several limestone beds are laterally extensive (Cross outcrop. marine in origin suggesting a submarine platform Arcadia Park compared with older Eagle Ford Sections A - A' and E - E'). Carbonate body Brl (Cross (McNulty, 1965, p. 52,53). Formations results in a lower shale-to-sand ratio beneath Section E - E') suggests a progradation of the carbonate Distribution and Thickness The most striking feature of the Arcadia Park is the 2.5: 1. Sand accumulations occur in six areas within the environment into the basin. However, carbonate body The Britton Formation is present throughout most numerous and varied concretions that occur within the basin. Areas A and B are apparently the product of Br2 occurs at approximately the same position in each of the basin (Fig. 10). Three major areas of thickening section. These nodules, which vary widely in size, shape, delta input from the north. Sand near area C appears well, indicating that an are ally extensive carbonate occur; two in the north, near area A, which exceed 200 and pattern, are apparently the result of diagenetic to be related to delta input from central Texas. Shale­ environment existed towards the end of Britton time. feet, and one on the western margin, near area B, which mineral deposition (Shuler, 1918, p. 17). to-sand ratios for area C are greater than 10: I, indicating Small sand channels (Cross Sections C - C', D - Df, exceed 250 feet in thickness. The Britton Formation thins On electric logs the Arcadia Park is recognized by that the dominant sediment being deposited was mud. and F - F') are present, and range to 40 feet in thickness. generally southward to less than 50 feet in area C. a distinctive blocky shale signature (Fig. 4). The upper Sand accumulations at areas D and E appear to represent The wide distribution of both calcareous and Variations in thickness correspond with sediment input contact of the Arcadia Park with lower-most Sub­ westwardly migrating channels off the Sabine. This is terrigenous sediments, often overlapping, suggests points and probably reflect local differences in Clarksville (or Austin in the southern basin) is recognized the first evidence of sand being derived from the Sabine interfingering of carbonate and sand depositional sedimentation rates. The eastern absence of Britton by an abrupt increase in sands or limestones. uplift during Eagle Ford deposition, and suggests the environments during Britton time. Carbonate bodies strata is apparently a function of erosional removal of The decrease in Sp and resistivity on electric logs tectonic uplift of that positive structural feature during include calcareous mudstones, calcareous bioclastic the Britton during late Turonian uplift of the Sabine reflect the dominance of fissile to blocky mudstone this period. Shale-to-sand ratios for area E are less than mudstones, packstones, and bioclastic grainstones, all block (Granata, 1963, p. 66). The Britton Formation observed on the outcrop. Few carbonates exist in the 2.5:1, indicating high sand delivery off the Sabine. The of which indicate wide varieties ofcarbonate depositional thickens south of the Sabine uplift as Eagle Ford rocks Arcadia Park indicating that the environment in east sand at area F was deposited on the outer shelf of the environments (Charvat, 1985, p. 33, 37). Carbonate body plunge into the Gulf Coast basin. Texas was not favorable for calcareous sedimentation. basin (Siemers, 1978, p. 506). This sand, derived from Bri (Cross Sections A - A' and E - E') apparently Britton Sand is distributed throughout most portions When carbonates are present in the Arcadia Park (Cross the Sabine uplift, was apparently the product of turbidity represents an interdistributary and marginal bay deposit, of the East Texas basin (Fig. 11). Most of the sands Sections A-A', B - Bf, and F - F,), they are usually transport across the Angelina-Caldwell Flexure preserving mostly mud-dominated carbonates. Wide­ are thin, averaging less than 10 feet in thickness. thin and are ally limited. Thin individual sand bodies (Siemers, 1978, p. 506). spread carbonate deposits like Br2 (Cross Sections A Therefore, areas of thick sand accumulations usually are present in the Arcadia Park (Cross Section C - C'). The increase in thickness and distribution of sand - A', E - Ef, and F - F') are indicative of periods of reflect stacking of sands rather than thickening of However, thick sand accumulations increase in bodies, the decrease in shale-to-sand ratios, the marked low clastic influx and widespread marine conditions, as individual sand bodies. Some Britton Sands attain frequency and distribution, possibly reflecting an decrease in abundance and thickness of limestone, the indicated by extensive packstones and grainstones. Some thicknesses of 40 feet, making them the thickest Eagle increase in clastic sedimentation during this time (Cross lack oflaminar clays, and the lesser abundance oforganic of the grainstones with reworked shell material Ford Sands in the lower Eagle Ford section. The shale­ Sections D - Df and E - E'). matter suggest better circulation, more oxygenated accumulated under higher energy environments. to-sand ratio for Britton strata rarely averages less than waters, more abundant fauna, and a dominance of clastic While significant accumulations of both sand and 5: I for most of the basin, indicating that again the Stratigraphic Contacts over marine-derived sediments, probably as a result of carbonate occur in Britton strata, the dominant sediment dominant sediment was mud. In northern east Texas, the Arcadia Park is overlain vastly increased sediment supply. is shale. This shale, which is usually dark and finely Major sand accumulations originate from the north, by the Sub-Clarksville Formation of upper Eagle Ford laminated, has been extensively studied by Chamness area B, and extend southward to area A in a highly strata. While the contact between the two is lithologically SUB-CLARKSVILLE (1963), Silver (1963), Thomas (1980), and Charvat complex distribution pattern, probably caused by deltaic abrupt, it is conformable in nature. In the southern Lithology (1985), and is recognized as being highly organic, progradation across a shallow shelf in quiet water. Area portions of the basin, the Arcadia Park is overlain by The Sub-Clarksville Sand is the upper-most unit of composed of calcium montmorillonite, with scattered C resembles a simple elongated deltaic lobe. However, the Austin Group along an unconformable contact. the Eagle Ford Group in the East Texas basin. Near kaolinite and calcite. These laminated organic-rich shales the lack of typical deltaic configuration may be due to Dallas, it is probably represented by the sandstone represent deposition in waters with anoxic bottom paucity of control. Distribution and Thickness "fishbed" assigned to the upper Arcadia Park. It is not conditions. The laminar character of these rocks reflects The sand accumulation in area D shows close The Arcadia Park is present throughout most of the present along the western outcrop belt. Along the the extremely calm water conditions that existed during resemblance to a bird foot delta complex. Distribution East Texas basin (Fig. 12). While variations in thickness northern outcrop belt it expands from the single their deposition. The increased organic content of these of sand in this manner suggests both low wave energy occur throughout the basin, the Arcadia Park generally "fishbed" eastward to a thick sand accumulation of rocks also reflects sea floor conditions that enhanced and low tidal energy, even though this area was nearest thickens in the northern portions of the basin, reaching formational status (McNulty, 1966, p. 375). It is often organic preservation through exclusion of scavenging the open ocean of the Gulf Coast basin. Accumulation more than 200 feet in thickness near area A. A significant termed the Lake Crockett along the northern outcrop benthic organisms. of sand at area E probably represents offshore bar thickening of the strata occurs in the central portions belt, and is sub-divided into two members, a lower Bells deposits. The southeastern accumulation of sand, in area of the basin near area B, which exceeds 200 feet; this Sandstone Member, and an upper Maribel Shale Stratigraphic Contacts F, extends past the Angelina-Caldwell flexure, and was is possibly associated with minor thickening west of this Member (McNulty, 1966, p. 377). The Bells Sandstone In the northern portions of the basin, the Britton probably deposited by currents fed by the offshore bars area along the western margin of the basin. Thinning consists of gray to brown weathering quartz sandstone, formation conformably overlies the Tarrant. Southward from area E (Siemers, 1978, p. 506). of Arcadia Park rocks near area C is indicative of slower typically fluvial in the north and marine near the beyond the pinchout of Tarrant rocks, the Britton Clay sedimentation rates. The Arcadia Park sediments thin southern margin of the unit. The Maribel Shale consists rests unconformably on the Woodbine. The stratigraphic ARCADIA PARK SHALE eastward and are not present over the Sabine uplift, of medium to dark gray laminated shale with silty hiatus represented by the Woodbine-Britton unconfor­ Lithology area D. The eastward thinning and pinchout of Arcadia partings, and thins eastward along the northern outcrop mity becomes more significant southward along the On the outcrop near Dallas, the Arcadia Park consists Park strata are a function of diminished deposition and as the Bells thickens. The Maribel grades upward into outcrop ofthe basin. From north to south, the Woodbine of 100 to 200 feet of gray to dark gray, fissile, calcareous eventual truncation due to westward progression of the a 5 foot limestone bed that marks the top of the Eagle changes facies from sandstone to dark non-calcareous mudstone with thin laminae of siltstone, sandstone, and Sabine uplift during late Turonian time (Granata, 1963, Ford Group (McNulty, 1966, p. 375). Pepper Shale. However, even here, where shale is on fragmental limestone. Southward, the Arcadia Park p.75). The Sub-Clarksville is easily recognizable on electric shale, the Woodbine-Britton contact is easily distin­ thins and assumes the name South Bosque Shale in the A moderate accumulation of Arcadia Park sediments logs by an increase in both Sp and resistivity signatures guished (Scott, 1926, p. 160). South of Belton, the Eagle Waco area (Pessagno, 1969, p. 62). The South Bosque occurs north of the Sabine, area E, termed the Pittsburg indicative of increasing sand (Fig. 4). The upper contact Ford rests unconformably on the Buda Limestone. The consists of dark gray to black, blocky shale with few syncline (Stehi et aI., 1972, p. 41). Arcadia Park of the Sub-Clarksville with lower-most Austin is Britton Clay is overlain by the Arcadia Park Shale. The bentonite seams. The upper 30 to 50 feet of the South sediments thicken southward away from the Sabine recognized by a rapid increase in carbonates of lower 22 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 23

Outc rop Belt l:a91e Ford~:

30•

44.

45.

'.. ,.S8 _~.. 00 ,-' \..­

• 01 oJ• • 01 03• , 02 0; ...... --- .. ""-,... ---:...... -"" II" - -,",,,,-;-~ .. ~ """"",­ 94· '/ 94· ,/' .101 .101 -92 /.100 ,/.100 9S ) , 102 103 95. . ! 10J 102 \ • • • 9d ·93 -r--­ ­ ·93 \-r-----­ .. 1•. ___ ._ . ...) ·104 I D ._,''\ .104 ,- - -""T -- 99., ( .% 99-, ( .% ,~-...... '\- -. , - \ , '-­ \.97 • 98 ) 107 • 98 • '- /''-. - ) 107 , <"·112 ----, ( \ _108 \ .108 .)., , " \ ", ,; 109.(. .111 ", j 109.( IlJ , I .113 " , ' ) - ',,_ .. --9\­ -.­, ,.:;...r~-:_ -101 .... ·,61 .­ /103 157 100 '.

50 o 50 100 o , ' Scale In Miles Scale In Miles Col. 10 Feet SAND ISOLITH MAP: ARCADIA PARK C.I.50 Feet ISOPACH MAP: ARCADIA PARK N N

Fig. 13: Sand isolith of the Arcadia Park Shale. Six areas of major sand accumulations are visible, A, B, C. D. E, and F. Of these, A and B appear to be related to deltaic input from the north; C appears to be the product of deltaic input from central Texas; 0, E, and F appear Fig. 12: Isopach map of the Arcadia Park Shale. Thickening of Arcadia Park occurs in areas A and B. apparently related to sediment influx. to be sand lobes, possibly associated with streams entering from the Sabine uplift on the east. Since F occurs beyond the Cretaceous continental Thinning in area C, accompanied by an overall southward thinning appears to be related to slower sedimentation. Note the Arcadia Park margin, it may represent a turbidite sand deposit (Siemers, 1978, p. 506). is absent over the Sabine uplift, area D. 24 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 25

Outcrop Belt Eagle Ford R~~

44. 44.

45. 45•

,.58 s: 1>0." ,-,' .-­,- • • 61 63• .61 63· 69· __ 0; ,.­ ... - ... , 62 94· ./ --' ,----"-­",,-' -.... _.-Ii' 101 ·92 94­ ~./ /.100 • ·92 JOI /.100 95. ) 103 . 102 95 ) • • , 103. ·93 \ -r' . 102• 'Ill ·93 r,. _____ ~ ·104 .. r, ______• ~' ·104 '-­ .." } .' \ ./ \ .96 99 , , 1)4 \,/ -U8 89 < .96 99·, \ 87 " "\- ...... , • • 89 . •117 \ '-­ " \ '\--",,,,,,-,, lIS \ • _ - - -;." • 90 \ .97 "- • 119·\ ,­ ...... • ~ • 98 . 117 I 148'./'­ ) 107 .\ ------, "­ -" \ \ \. \. 14: ' ..... 9.0 \.97 • / / \ .145 149." r -n2 .'''-~ 119 ' • 98 ) 107 \ .108 / \ \ ••'45 " ,./',­ \ • ) ,~" / -­ 137• ) '49... ·"2 • /1 135 ,.­ I ~ '-'-, 123 14,. ./ ". ; 1090( \ /', ( 14':, ,.- , • ,,\ .108 \ I 138. { ./ ~1 135 • IH )/ '52 " 113 "-. -­ '. . . 123 / .131 \ / I ./.1 " • ./ • 138• • \ ( 146 • 125 )/ / . \. 136 _ '46 ,.­ 152' 113 ' I 1090( ./' , .129 \. 136 __ ­ " • ./ 150 • / / " ( ,..­ " /1 "'-." /' \/ 1 • r ...... ,: -' /" .. .129 ,. ,-'-" "­ 1"./ 140.;. '. , _./ _, . ./ 150 ,. .130 . ,. - / • .. \/ 1 ,...{ ''', /' '-., 126 \ ,".if • J./.,1 151 /154 16~" 161 . 'l" ... """""--­ ' \.'57 r 163 .130 ,./ ' ­ .' -161 4 .. • • \ 139. /' 144 -, ,- ­ • / 155. . • . . . 157 160" 1163 \. ·'62 126 \ I 134 7­ -­ -~,' I \{' 158 I 134• \­ ___139 >' 144·L, .151./,/15 • 155· \ • • 127. ~-/' , \. ·162 \ .141 142 '\ 156. • 1 \ ,­ \ ' 158 •. • I ·,59 127. \ • •• .141 142 I ( 156. 133/ 153 \.. ) . '\ . ·159 153 \ 143 I'. , 133/ ,. \. " \ \.p .. -, • 143 I \ • "" ... -:; .....I

o 50 100 e--w r o 50 Scale In Miles C.I. 50 Feet ISOPACH MAP: SUB-CLARKSVILLE Scale In Miles N C.I.10 Feet, SAND ISOLITH MAP: SUB-CLARKSVILLE N

Fig, 14: Isopach map of the Sub-Clarksville Sand. Sub-Clarksville strata reaches 250 feet in thickness near areas A and B. Note the southern Fig, 15: Sand isolith of Sub-Clarksville rocks. Highly complex delta-like dispersal occurs in the northern East Texas basin, near area A, with termination of the formation near the center of the basin. lobes of sand extending southwest almost to the depositional pinchout of the unit. The thickest sand accumulations exceed 100 feet near area B. and are the thickest in the Eagle Ford section. 26 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 27

Austin. This increase is indicated by large kicks in both erosional truncation along the southern margin of the outcrop belt. The lack ofrecognition of upper Woodbine to have formed the embayments and arches associated Sp and resistivity on electric logs. unit. Sub-Clarksville rocks reach a maximum thickness and lower Eagle Ford, as reported by Pessagno (1969, with the Gulf Coast (Bornhauser, 1958, p. 349). Towards The inter bedding of the Maribel and Bells observed of 250 feet in the northern East Texas basin, near areas PI. 9) may be a result of sediment starvation or the end of the Woodbine erosional period (late on the outcrop is reflected by the intermittent character A and B. condensation. There is no question that upper Wood bine Cenomanian) basinal downwarping occurred in east on electric logs. Generally, the Sub-Clarksville contains A sand isolith of Sub-Clarksville rocks shows highly strata have been eroded from the western flank of the Texas, apparently the result of sub-crustal movements more sand than any of the preceding Eagle Ford units, complex delta-like dispersal of sand in the northern Sabine. The lack of coarse sediments within the possibly accompanied by salt withdrawal (Bornhauser, suggesting a dominance of clastic sedimentation during portion of the basin, with lobes of thick sand extending stratigraphic break suggests that the lands surrounding 1958, p. 367). Spasmodic downwarping allowed Sub-Clarksville deposition. Several of the sand units like southward almost to the depositional limit of the unit the East Texas basin were of low relief (Stephenson, expansion of the Eaglefordian seas into east Texas, Sci and Sc2 (Cross Sections A - N, D - D', and E (Fig. 15). The thickest sand accumulations exceed 100 1929, p. 1324). While the details of the unconformity initiating Eagle Ford deposition (Coon, 1956, p. 87). - E') are very thick and extensive, apparently the result feet and are the thickest in the Eagle Ford section. The are uncertain, it is probable that the hiatus decreases The lower-most rocks of the Tarrant Formation of the of mUltiple stacking of smaller sand bodies. Very few shale-to-sand ratio is 1.5: 1, the lowest of any Eagle Ford basinward, and is no longer present in the central Eagle Ford group record the initial expansion of the calcareous sediments are observed in the Sub-Clarksville unit. Clearly the source of Sub-Clarksville sediments was portions of the basin. However, the southward increase Eaglefordian seas and early development of Eagle Ford as is the usual case in clastic-dominated sedimentation. from the north, apparently delta input from area A, in stratigraphic hiatus along the outcrop suggests that deposition (Fig. 16). with a complex distributary system. The input point for the southwestern margin of the basin was subjected to Early expansion of Eaglefordian seas were in a north Stratigraphic Contacts Sub-Clarksville Sands is essentially the same as that for greater erosion and/or longer periods of non-deposition to northwesterly direction. Reworked mudstone pebbles On the outcrop, the contact between the upper Eagle all coarse clastics throughout Eagle Ford time, indicating than in the north. and small "water worn" sandstone pebbles at the base Ford and lower Austin is usually considered unconform­ a major river source sustained for a very long period. of the Tarrant, and the typical electric log signature of able, being recognized by the absence of the Sub­ The abrupt increase in sand during Sub-Clarksville time TARRANT DEPOSITION the Tarrant sections, suggest that the initial transgression Clarksville Formation in the southern portion of the suggests a major change in provenance, perhaps a Differential regional subsidence, probably influenced of the Eaglefordian sea was probably only a spasmodic basin, the presence of a basal conglomerate in the Austin, product of tectonic uplift. by older structural trends in the basement, is believed creeping of marine waters across the extremely flat and the presence of borings into the surface of the Eagle Ford filled with basal Austin Chalk (McNulty, 1964, SUMMARY p. 538). However, the nature of this unconformity in Eagle Ford rocks of the East Texas basin consist of the sub-surface is not well known; the inferred hiatus the Tarrant, Britton, Arcadia Park, and Sub-Clarksville associated with the Eagle Ford-Austin unconformity Formations which have several common characteristics. appears to diminish towards the north-central portions These formations are mud-dominated with an increasing of the basin, and may disappear in the deeper portions sand content upward in the section. All of these of the basin. formations were supplied with sediment from the north and northwest except for late in Eagle Ford time when Distribution and Thickness sediments also originated from the east off the Sabine Sub-Clarksville rocks occur only in the northern half uplift. Eagle Ford rocks become more marine southward of the basin (Fig. 14). The north to south thinning of and are typically referred to as laminate deposits of Sub-Clarksville strata (Cross Sections D - D' and F ­ anoxic bottom waters. However, only the bottom two­ F') is apparently a product of sources on the north. thirds of the group have this bituminous laminated Correlations indicate that lateral thinning of Sub­ nature. Clarksville (Cross Section E - E') was the product of

~/ /:-.-..;" DEPOSITIONAL MODEL t. • 0-'

l " .,./. _ \..9-f' i /:­ ,. -:' Because of the highly organic nature, the abundance uncertain origin at the base and top of the Eagle Ford / ~:""" ..... of laminites, and the absence of benthic , Group, and within the group as formation boundaries; l / models for Eagle Ford deposition have generally 2) rapid alteration in sediment type, from anoxic to + -' involved deep water environments. However, laminated oxygenated, suggesting rapid changes in sediment and organic-rich sediments without benthic fauna are not bottom water chemistry; 3) progradational sediment water depth indicators. The only conclusions that can dispersal patterns suggesting shallow water deltaic c:J Mud dCllflIltfI!ed ~"'fd8lu be made from organic-rich laminites is that: I) organic depositional systems; and 4) intraformational phosphatic _ClllMi<:domtf'latfldriYlirdttnllll sedimentation was high; 2) clastic sedimentation was low; conglomerates on unconformity surfaces. All of these ~o.'p"tvoatel!l1e:.nn.mud5

3) organic preservation was high, suggesting anoxia factors combine to indicate that Eagle Ford rocks of m.m Marine ti!!IHIOI'lI c:iapm.rt. BELTON beneath the sediment-water interface; 4) bioturbation the East Texas basin were products of generally shallow ~ MalQin.l~tltOllC&~MClim.nt HIGH was lacking, due to the lack of benthic organisms, water sedimentation, with water depths ranging from r::::J Sebi~UpI!II suggesting anoxic bottom waters; 5) current and wave as shallow as a few feet to as deep as one to two hundred activity were minimal; and 6) cyclical variations in feet. c:J AnolOO: '''111'' and mudt sediment delivery were occurring. These conditions could indicate either shallow epicontinental or deeper pelagic PRE-EAGLE FORD TIME waters. With the termination of Woodbine deposition, Fig. 16: Regional setting of the East Texas basin during Tarrant deposition. As Eaglefordian seas expanded north-northwesterly in east Texas, Beyond this, Eagle Ford rocks of east Texas contain marginal parts ofthe basin were su bjected to long periods they reworked upper Woodbine sediments along the margins of the basin. Sediment influx began from the north rapidly establishing river deltas with mud-dominated sediments in the northcentral part of the basin. Finer sediments were deposited in more distant southern and numerous and varied features indicative ofshallow water of non-deposition and erosion. Little is known about western parts of the basin. Sedimentation in the deeper parts of the basin was occurring, but these sediments are indistinguishable from Britton deposition, including: I) marked of the Woodbine-Eagle Ford unconformity beyond the strata. 28 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 29

expanse of east Texas. The southern extent of the beach delta complexes suggest that rapid flocculation and facies on the western margin of the basin (Fig. 16) is sedimentation occurred as a result of high sediment not known, but probably corresponds with the southern influx and significant chemical variations between the termination of sand in Figure 9. The southwestern part runoff water and the water in the basin (Potter et al., of the basin apparently arched creating the Belton high, 1980, p. 8). The net result was river deltas with mud­ and formed a sub-marine platform subject to marine dominated sediments and few coarse clastic sediments, planation by waves and/or non-deposition. The same a condition that characterizes most of the Eagle Ford relationship occurs along the eastern margin of the basin, terrigenous deposits in east Texas. , " with no discernable beach facies south of the mapped Finer sediments were carried into more distant and -,-.~. sand termination in Figure 9. A"":"'l.;or"lo~-:::.,-' . _.-0:;.. deeper parts of the western and southern basin. In the • ~...:::.i',. With the invasion of Eaglefordian seas sediment influx ',j -.~...... northwestern part of the basin a marginal embayment . ~ \. \_, began from the north near the Ouachita Mountains. existed to the west of the delta. Sedimentation rates ~;~r~-· This influx from the northern provenance was apparently in this area were slower than in the areas of active delta ~ ~~""~ in existence prior to Woodbine deposition and existed sedimentation. Sedimentation south of the mapped ~k"~.. throughout much of Gulfian time, probably reflecting pinchout of the unit (Fig. 8) probably occurred in the major continental drainage. "<.J..--""J"'" deeper parts of the basin, but these sediments are ..... As distributaries fed into the East Texas. basin, they indistinguishable from the overlying Britton strata and ""t~·~r._ ./~,,::~ / /.-:Ji. rapidly formed deltaic complexes. The unusually high are included in that unit. shale-to-sand ratios of these deltas suggest a provenance with low relief, and probably high rainfalL The thick BRITTON DEPOSITION accumulations of mud-dominated sediments around Britton deposition marks the maximum extent ofearly

E::::J Mud domN\al1id rlV8f ~

II1II ClastiedomlNlledriYe

~ OMperwalatmarlnelnlJlk

BS3. M&rIne_me8tCl\8~ BELTON

~ ~1rni!8mbayme!'\tcalaweouti&edim.nt HIGH

EEJ Satlme Uplift

Anoillic alWn and muda

Fig, 18: Regional setting of the East Texas basin during Arcadia Park deposition. Following a brief unconformable period. Arcadia Park deposition began with re-establishment of clastic influx from the north and west, accompanied by drainage distributaries shed off the Sabine uplift. Note that these westwardly prograding deltas are the first evidence of Eaglefordian activity of this structural feature. Also note the downwarp called the Pittsburg syncline in the northeastern part of the basin. While mud from these deltas dominates east Texas, calcareous sediments were present in the marginal embayments.

Eaglefordian seas in east Texas (Fig. 17). The These conditions apparently existed throughout Britton distribution oflower Eagle Ford sediments in and around deposition. the Sabine uplift, and the truncation of lower Eagle Ford Clastic influx formed prograding deltas. The dom­ sediments on the western margin of that uplift, suggest inance of shale in the Britton section indicates that these that the uplift received sediments during Britton time deltas were mud-dominated. The distribution of sand (Granata, 1963, p. 75). The presence, variety, and can probably be attributed to progradation of the deltas ITIIID1 Mud dominated flW!' del'll.. regional extent of Britton Limestones indicate wide­ across a shallow marine shelf with extremely quiet water .. Cla1IcdCImmal8dfl_l.ieJIu spread marine conditions and lower terrigenous input (little or no destructive energy). Sand distribution in ~ Oeepervrater marine mOO5 throughout east Texas. Early Turonian time was a the southern basin, nearest the open ocean, reflects

~ Ma~na Ilmel'lOM cIIposilS carbonate-producing epoch indicating uniform climates conditions of low tidal and low wave energy, indicating

~ Margine! embaymant c:alc:araous sediment world-wide during most of Britton deposition (Reeside, that the Gulf Coastal basin was also an area of little 1957, p. 522). The mud-deltas prograded across the agitation. UIII:ITI1 Sa/)n,Up"1t shallow marine shelf of east Texas creating latterally The widespread laminated muds interbedded with c::J Merde..-.nd muds. co-existing sand, mud, and limestone depositional more normal marine limestones suggest that geochemical environments. Restricted limestone deposition existed environments were subject to rapid and major variations. in both the interdistributary areas of the deltas and as Britton rivers apparently discharged large volumes of Fig. 17: Regional setting of the East Texas basin during Britton deposition. Eaglefordian seas reached their maximum extent into east Texas carbonate banks in marginal embayments around the fresh water rich in both organic detritus and dissolved depositing laterally adjacent muds, sands, and limestones. Widespread marine conditions allowed extensive limestone deposits, Note that much deltas. The presence of abundant bentonite seams nutrients, making the East Texas basin abnormally of the Sabine uplift was receiving sediments during Britton time. Clastic influx created mud-dominated deltas which prograded across the indicates that explosive volcanism occurred during productive in organic matter (Habib, 1982, p. 125). In shalIow marine shelf. Some of the coarse sediment escaped down the Angelina-CaldwelI flexure. Exceptional conditions made the east Texas area abnormalIy productive of organic rich sediments in the form of laminated anoxic shales. Britton deposition, and that ash fell into unusually calm areas of higher sedimentation rates, as in the delta facies, water where laminites indicate toxic bottom conditions. organic matter was rapidly buried and was relatively 30 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 31

unaltered by diagenetic oxidative processes, creating from the Gulf Coastal basin across the shallow platforms Eaglefordian seas into northwest Louisiana and The regressing Eaglefordian sea exposed the south­ some of the organic-rich sediments of the Eagle Ford of southwestern east Texas. southwest Arkansas (Granata, 1963, p. 53). western portions of the East Texas basin to erosion, (Habib, 1982, p. 123). Sediments in the marginal During Arcadia Park deposition, clastic influx from The decrease in limestones in Arcadia Park sediments, which removed and truncated upper Eagle Ford embayments were enriched in organic detritus over the the north continued (Fig. 18). Drainage of the Texas the increase in size and distribution of large sand bodies, sediments. The depositional limit of the Sub-Clarksville deltaic sediments by photosynthetic productivity of craton shifted southward, abandoning the earlier input and the lowering of shale-to-sand ratios reflect an is not known because of truncation near the southern plants of either marine or land origin (Waples, 1983, points near Dallas and entering just north of the Belton increase in clastic sediment supply. Calcareous sediments margin of the formation. However, the Sub-Clarksville p.970). high. The northwestern basin was the site of a marginal were confined to interdistributary bays marginal to the once extended south of the mapped pinchout, perhaps embayment with much slower sedimentation rates than '\ deltas. Late Turonian sediments for other basins of the for a considerable distance. ARCADIA PARK DEPOSITION in the deltas. Sand accumulations off the western margins continental United States reflect this shift towards

Towards the end of Britton deposition, and continuing of the Sabine uplift represent the first Eaglefordian " increased terrigenous deposition, indicating that large­ SUMMARY through early Arcadia Park deposition, conditions in activity of this structural feature. The older Britton, scale environmental changes were responsible (Reeside, Eagle Ford deposition began following a late the southwestern portions of the basin changed from Tarrant, and Woodbine sediments which were once 1957, p. 522). Woodbine erosional period and was characterized by periods of deposition to relatively long periods of non­ deposited on the western portion of the Sabine uplift, river-dominated deltas that deposited mostly mud and deposition and possibly erosion. This stratigraphic were then eroded, reworked, and redeposited as newly SUB-CLARKSVILLE DEPOSITION prograded across the calm marine shelf of east Texas, hiatus, which marks the boundary between the Britton formed westwardly prograding deltas (Halbouty and Sub-Clarksville deposition marks the termination of supplying much of the sediments that comprise Eagle and Arcadia Park Formations, decreases northward Halbouty, 1982, p. 1051). Clastic sediments also shed Eagle Ford deposition by a shift toward land-derived Ford rocks. Exceptional conditions early in Eagle Ford along the outcrop, indicating that the northern basin southward off the Sabine and were transported by coarse clastic sedimentation (Fig. 19). The input ofclastic deposition created an abnormally productive basin was subjected to more complete periods of deposition. turbidity currents across the Angelina-Caldwell flexure sediments from the north, as implied by the Bells Sand which allowed sedimentation of carbon-rich laminated This unconformity probably diminishes basinward, into the deep Gulf Coastal basin (Siemers, 1978, p. 506). facies, created an expansive delta which occupied most shales. Later during Eagle Ford deposition, the Sabine though this is not known. Given the geologic setting The reactivation of the Sabine uplift created the of the northern portions of the basin. As the delta uplift became active as a provenance supplying clastic of the Eagle Ford during this time, the Britton-Arcadia downwarping of the Pittsburg syncline to the north. This prograded southward, it gradually displaced the sediments to the east Texas area. The highly complex Park unconformity may reflect increased wave energy shallow structural trough allowed the expansion of Eaglefordian sea in the East Texas basin. West of the Sub-Clarksville delta displaced the Eaglefordian sea over Sub-Clarksville delta the Maribel accumulated in a large a sizeable area, terminating Eagle Ford deposition. marginal embayment.

SOURCE-ROCK POTENTIAL OF THE EAGLE FORD \ ROCKS IN THE EAST TEXAS BASIN J The Eagle Ford Group and adjacent Gulfian units The Eagle Ford contains between 0.74% and 9.18% have produced the greatest amount of petroleum in east organic carbon at various locations throughout east Texas. The bituminous laminites in the Eagle Ford Texas (Fig. 20). Three areas of anomalously high organic suggest that this unit could contain the organics that carbon were observed. Two readings, near areas A and generated the Gulfian oil. Therefore, the purpose of this B, occur in sediments representing marginal embay­ section is to evaluate the source-rock potential of the ments. These high organic values reflect restricted I: "'.J-...; I ...... _ .... /.-...... '. '-. Eagle Ford Group in the East Texas basin, to examine environments with increased organic preservation of .r. ,­ '-'- /." -.'\ / '",.>'~ reservoir trends of rocks that could be producing oil these embayments. The third anomalous reading, near /'" -' .-. ~ " ...... ,/' " /' area C, had coal or carbonized wood particles within ~ ..... _ ./\..0.,(,\0 ':' . ­ ~ _. __ '~ ,-_./ ~C~LDVJf.LL originating from the Eagle Ford, and to volumetrically /",../""""'.­ ,,/ estimate the organic carbon in the Eagle Ford of east the samples which biased the reading. However, the -.. ,~\. '-./.I' ,r·':".-, Texas as an indicator of petroleum produced . presence of these particles in this portion of the basin / ~ -=::-~~~L~](~~£~\ The method of investigation for this section entailed tends to support the delta model. The I% isopleth ~ an evaluation of the total organic carbon content of roughly outlines the delta complex that supplied the Eagle Ford as an indicator of source-rock potential. sediment from the north throughout Eagle Ford The organic carbon content (Appendix III) was used deposition. Readings in the central portion of the basin, [[III] Uudoomlnatl

S~2 I • ·1\"i ~4 I ..J ...... -:- '(.;8 ... O~6" ._._-! ~O.8r"·;--·-· ...... L-----f -' s~l!n ",. -...,.... .~3 - c_5 • I I SR.13 1 I S~4 I' .... I 11.561 SR 1 V I SR6 11.0al • , ~I' 0.991 ". -. i . 1:74 I 27 I , .... , 1. ....l. --;­ -- -.-.1-1- • - • _._....1 I ./ \ -'-L I'. ~""".p,,_ .. --.-1._....I ....l }ii.... r SR.S S~ !-._. S~ I , .-\S~3 1'-­ :i2!'~J... '---, . i.~"'I' 0.97" I !i4.9t. j ­ - -'.-\ S~3 . I i i.~ \ ! ! ..... , . S,¥-8 ._. - ._1 S,¥-8 !--- . - . , 1.301 1% 1.301 I "'-_.­ . I 1 1 I\.· ~-.-.-.-.-.-.-.~, ... , I, ... .'". S~ \._~. \._-_._ . 0.93':'. s j21 ~o" 's~21 ~90~~ 1.041 'f~6 • 1.93" • 1.871 \ , \ \ " '-. \ ''-. " \ '" ' \ '".' '. \ .... ·C . \ .... C_._.-·-...... \ ",.-'-'-'-""'" ~ /' ~ /,,' \ \ ... ' \ . .... ' '­. ,. .. \ ) ... " ) ... ' . ... ' I.\ ! ~ ( • c C' , ...... "..... ' 11 ",-"" , ..... ' " .;1 :;' "" " /' ,..1(' ..;1 :r"" " • J..'" l " ,. .1('• .J..' '" l• . " I \-._._...... '-./ . \. . " ...... '-.." \. . I '\ I ~ ... --­ I (. I • 'I . I . . , . , \.''. • I , '\ '\

TOTAL ORGANIC CARBON TOTAL ORGANIC CARBON Scale In Mlle. ISOPLETH MAP: COMPLETE EAGLE FORD Scale In Mlle. ISOPLETH MAP: LOWER EAGLE FORD N SECTION N SECTION

Fig. 20: Total organic carbon isopleth, Eagle Ford, East Texas basin. Organic carbon readings for the Eagle Ford range from 0.74% to 9.18%, generally averaging greater than 1%, which is unusually high for sedimentary rocks. Note the three anomalously high organic values in areas A, B. and C, which occur in marginal embayments that were enriched in organic sediments. Also note that readings in the central portions of the basin where sediments are deeply buried in a higher temperature regime probably represent values that have been lowered by maturation Fig. 21: Total organic carbon isopleth, lower Eagle Ford, East Texas basin. Few locations with organic carbon values lower than 1% occur, of organic material and expUlsion of oil. indicating an enrichment of the lower Eagle Ford section with respect to organic carbon. 34 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 35

I

r L.-., ' I o.-. , , --'--, _ • ...1 ".1 . ~...... I L--'-­ , _...... ' :;..____ ..."l.. ~.-, ... ",,;, I I' ~-- ...... ,.,.,. • 0 I " • I, I. I'I ! I 1/--, i . 108;;;.0:-",.,....- ____,__ .... .J . ___41.~~ : ~ !VI " • I o I ." ' ..,. - 1-----) 0 I J' -- ..., -..l. \1 ~..~.A' •\. . ­ - ­ - ­ - ­ - , L01%j --.­ , .". I ' l'~y\.­ .... I 0 "'-, ' ~ , . . I . . ...:.~ "", It I , ' o . . ! " ._.•• '---._' 1% ! -."'\... -~ ..... I"'\.·_. -.. \, . --.-. -z " 1 '­ 1 Ii \'" -. r-'-'-'-'-'-'--~ .. -_ ""',..-...... ",,' ---­ ....'.'-. ' . /' • ~ I

/ ." / " IIl-­·\ \ _.\---7/-''-, i/' \ ·.1 •• .'? II., ( 'r--'-'-' \ . ~ , ;' ~.,...'L,---'-­ . . "r: ,.. , \ \ ,..,., ~ , "'., \ ..',- ­ -­ . - -- . -.-~ ., ~ --", \ ,.t1'./. •• .. '", . \" \ ~ i' .~ ( \ ... "", .­ \ \ \ ~. \\. ,',' \", , " " .'x. #..:WIt ...."'J":." ',\...... "', ,..... \ \ ./'(-----'-'. .. \ \ .,..,., - .-'". \ " ... J \ ",...... • , ,.r ..-.~ ...... t°,­ ) ~ ./ \ \." \ ,." " '<' ',-. -', ~ ( / ... .,... , \ '. '/'1' ...... , \ ~ \ " ) ,0\. ...' /' / " '­ \ ./ ( ( " \,/ ' I , , ( 1/' / '. ' ..!. ( -'" )/'\ rI ,.. ,/)" \ -. (. • /.' 1 " \,.,,~ . ., ...... " , ." ) ,. • - /I' .I'..... -:-.-' , ."" ) " \.-( .-.. 'J''SI /'. .'"..... , -' ,,, ,... / ­ \/ • 0 ./ " ' • ' r' --­ • :/ / j../ l' ,.I' ',""', '.\ r.l(', j..'. l ,/ . \ r.\!.....,...... I' ",/'\ ., It...... "'./ \.. . .lI/fII"'!..,." \ i \----- .... I (. .. . --, I (. • '" \ I \ , it' \ ., . " '\ ( \..,. ;, .~ ! \.., . " I''- ' • .... ­ ) '\ _­ '\ -­. -..JI ~

TOTAL ORGANIC CARBON Scale In Mlle. Scale In Mile. ISOPLETH MAP: UPPER EAGL~ FORD DISTRI BUTION MAP: GULFIAN N SECTION N PETROLEUM PRODUCTION

Fig, 23: Gulfian petroleum production in east Texas (Geomap, 1979, PI. I). Most production is concentrated in the central portions of the Fig. 22: Total organic carbon isopleth, upper Eagle Ford, East Texas basin. Upper Eagle Ford rocks generally have less organic carbon than basin where Eagle Ford rocks are rich enough to have provided the oil found in these reservoirs, possibly reflecting conditions of heat and those lower in the sequence, reflecting the c1astic-dominated nature of these sediments. pressure on the maturation of Eagle Ford organics. 36 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 37

generally considered potential source-rocks for petro­ may have been supplied with oil from Eagle Ford rocks. leum (Barker, 1979; Waples, 1983). Shales with 0.4% However, the western limit of Eagle Ford production organic carbon are possible sources of petroleum may indicate either that Eagle Ford reservoirs are not (Barker, 1979, p. 39). Therefore, Eagle Ford rocks, with present beyond this part of the basin, or that they have organic carbon values averaging greater than I %, may not been found. be considered superior sources of petroleum. Austin production is restricted to two general areas: The map of Gulfian production shows that most I) the northern and western margins where scattered production is restricted to the central portions of east small fields typically occur; and 2) along the southerly Texas where the Eagle Ford organics may have been limit of the basin where major Austin accumulations exposed to sufficient heat and pressure to generate and occur. Economical Austin production occurs in zones yield petroleum (Fig. 23). A few fields exist up-dip away of fractured porosity usually associated with localized from the major producing centers, probably representing faulting, deep-seated structures, or flexures related to unique petroleum conditions or longer distance lateral stress (Koger, 1981, p. 73). Oil found in Austin migrations. The Eagle Ford in the central portions of rocks has two appearances: 1) a golden brown high the basin, nearest the major areas of Gulfian production, gravity crude oil found in the fracture zones; and 2) ~1'1 • '-.58 _.~9 is clearly rich enough to have provided the oil found a black low gravity tar-like oil trapped in the primary I • 60 .. ..,.! \.,.,. in these reservoirs. Therefore, individual reservoir units matrix, which is uneconomical to produce (Hayward, I -,,' 70 • .61 63· are considered in the following section. oral communications, 1985). The high grade crude oil ~8 • I Buda production is generally restricted to the central (uncharacteristic of authigenic Austin oil) associated 69.:.... 6j portions of the basin. Two areas of Buda production with fractures (which could supply migration pathways) ---"-.-'.. -"I...... _...... " .. 94· ./ are up dip from the central portions of the basin, areas is indicative of oil derived from a different source than .101 .9'2 A and B. While Buda rocks in the basin are separated Austin rocks, possibly from the organic-rich Eagle Ford .".'00 from organic-rit-:h Eagle Ford clays by hundreds of feet clays. 95. ) 102 103. of Woodbine sttata, this may not have been an effective Potential volume of petroleum generated can be • seal against migration of Eagle Ford oil. Buda estimated on a local level by using total organic carbon, . production is most often associated with faulting or salt thickness of source-rocks, and areal distribution of the '.______~, ·104 tectonism, either of which may have afforded migration petroleum-generative province (Bishop et at, 1984, p. ( .96 99·, pathways for Eagle Ford oiL 44). The potential volume of oil generated by Eagle Ford '\- ..... Woodbine production dominates most of the organics can be derived by applying this technique \, -~'- \.97 production of east Texas. Most Woodbine production regionally, using an average organic carbon value of • 98 . . .",,:', , ) 107 occurs in the central part of the basin, although several 1%, planimetered thickness intervals (Fig. 24), and <'·112 ...... -., \.108 large fields exist towards the western margin, near area assuming that: I) Eagle Ford organics are uniformly .~. 'i 1090( A. The reservoir sands, which often dominate as much distributed in the section; 2) the organics in the center / .' "'­ as 70% of the Woodbine section, are due to complex of the basin are residual in nature, and since they are 152', .'ll -r' -'-._.!.... deltaic systems composed of land-derived clastics substantially lower than organic carbon values in (Oliver, 1971, p. 1). Eagle Ford source-rocks in the center peripheral areas, maturation has occurred; and 3) the of the basin appear to have been rich enough to account central area of the basin (defined by Gulfian production) for oil in Woodbine reservoirs. is the petroleum generative province for Eagle Ford Eagle Ford production is also restricted to the central rocks. The potential volume of oil, therefore, equals part of the basin. Eagle Ford production does not extend approximately 400 billion barrels (Appendix IV). as far west as the Woodbine and Buda fields, which

o so PETROLEUM POTENTIAL OF EAGLE FORD ROCKS Sca Ie In Miles IN THE EAST TEXAS BASIN C.1.100 Feet COMPILATION MAP: ISOPACH INTERVAL, N PETROLEUM PROVINCE, AND TOTAL Significant volumes of oil have been produced from reservoir rocks existent in the four formations herein LEGEND ORGANIC CARBON ISOPLETH. Eagle Ford Sands of the East Texas basin. These sands recognized to compose the Eagle Ford. - Denotes Isopach have generally been related to the regressive delta facies The method of investigation for this section entailed Interval - Denotes Total OrganiC of Sub-Clarksville time, even though reservoirs are use of the sand isoliths (already presented) to define Carbon Isopleth Interval present in the southern portions of the basin, beyond areas with sand intervals thick enough to be considered Denotes Boundary of the mapped pinchout of the Sub-Clarksville Formation. possible reservoirs. Generally, a potential reservoir area Petroleum Province This interpretation has not encouraged exploration was considered to be any area with cumulative sand beyond the Sub-Clarksville facies limits. However, with thickness in excess of TO feet. Areas up dip from Eagle the application of a multiple delta model for the overall Ford production were not considered to be optimum Eagle Ford sequence, the distribution of all Eagle Ford exploration areas. Fig. 24: Compilation map of isopach interval, petroleum generative province, and total organic carbon isopleth. By planimetering isopach sands is better understood, and offers a refined approach intervals within the petroleum generative province, using an average organic carbon value of 1%, the potential oil generated by Eagle Ford and renewed incentive for future exploration. The TARRANT EXPLORATION FAIRWAY rocks can be estimated as approximately 400 billion barrels. purpose of this section is to define major fairways of The net sand map for the Tarrant Formation shows 38 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 39

Outcrop Belt Eagle Ford Rocks ...... ~

36•

44. 44.

45• .-----­57 59 • '[ '. 58 : I """-"\...,. / ,. .-­ I t . , 54 60 ",....,,'" ""'­ I'" ,I - I I .. -.... ;.-" 70 • • 61 103• r .....,'" 70 I 61 • 66 "68 • ~"~I. • 63 • ,---- I 69·' .,L I 69. 62 ~ J .. -- -'--...... ;. --;...... ,,­ 67 I '-'--.­ ,...... ,..; 74 ''-. • I • , 94· I ,..;'--­ . • . .101 94 .101 "'" "'" \~ [·92 /.100 ·92 /.100 95 ) . "" , 102 103• 95 ) . ., 102 103• 911 ·on • • \ \-r--' ---. 9,1 ·93 \-r----­ - 75 \ I 85 • .' \ ~ -" , • 81 I '\ .104 I . • \. " - -- ­- -, "" .' " _ • _. _ • ..), ·104 "'" 120• \ ..:.-.-" '­ .86 " (.96 99·, "'" 120• ( .96 99·' 114 ,,,,,,' .118 , 17 89' \ , \ \ 121 ". ,. \ . '\-\ --­ .. "'"'- .. \ • • .. 121 115 \ 117 . 122.,' -" ( _ - - -..... 90 \ ~7 , _. ,'" ,--­ ...... ,.'" 122• 90 \ .97 , 119·\ • 98 ) 107 '" .. ' • \. 148 \. ,/"-., • 98 ) 107• "" \ \ ...... 137 ...'45 14ge < -112 '--,,- .. •• /'..... , 108 .108 ~ '. 2 ...... -, \ • "" \ ...) J..." \ '< II ", 0( -" 1 135 ' - • 149. 109, ( 147. '.\ ", I 1090( .111 J... ". I .m \ ,/ ' . "I 125 } ...... • 138. ( ./ 152' 113 " ' 138. ( ' • \ 113 " _.( • ./ 131 , (146'" • " .-.-. 12 152', • :_' -" I 136 .. _...... • /' 1S0 """-w,,",, _-",,- .. ­ \ • ( \ ,.," "" .129 \..­ " /1 • / -:.... -' "..---_ ...... \/ ) ''I ., .. ..,./ 140," I '. t" - .. - • , .130 ; I' • ./ / 154 • .' 161 . ·161 .. 126• t"'"''( J. ..! 151, 157 160" 11103 /163 " ." 139. / #' 144 .. , /' • / ISS­ \. • • 134\...----· I '-,' , 158 \. 162 I " 127. . \ . \ .141 .142 'I 1510. I ·159 13:t !.153 l., \ ) 143 \ • '-.

o 50 o 50 Scale In Miles C.I.10 Feet SAND ISOLITH MAP: TARRANT Scale In Miles N C.I.10 Feet SAND ISOLITH MAP: BRITTON WITH EXPLORATION FAIRWAY N WITH EXPLORATION FAIRWAY

Fig. 26: Sand isolith of the Britton with exploration fairway. Britton fairways are distributed in three areas of east Texas. Of these, the northern fairway is the most attractive because of stacking of sands and thickening of sand units which may offer multiple pay horizons. Sands of Figure 25: Sand isolith of the Tarrant with exploration fairway. The Tarrant exploration fairway covers parts of seven counties and consists the southwestern fairway are thinner and more widely separated, averaging between 10 and 15 feet in thickness. The southeastern fairway of thin sands which can form significant reservoirs on low relief structures. is composed of sands which probably represent turbidite fan facies that are thin and difficult to locate. EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 41

40 BAYLOR GEOLOGICAL STUDIES

36• 31>• ~..

~~.

~S. .58 59 ....- •... \...,. 58 59 :, " ...." ,...... ! • ..., \.0­ .1>1 63·

I .1>1 63• 6J ~ ,.- .. "'-. ~ --,"" 69.:..... I>J -­94 '/ ---_.. ;"--:,'*'"" ... ..",,; ... ·92 . .'0' ,,,.100 94 10' 95 • I ~~~~~~~'Y.....~~~,. I • 92 /.100I • -. \ ,/ .93 \. 103. ~ 9,1 '~2 95. ) 102 103. •. r---­ . . I ~ --­ ( ___ ._, ,o~ 9'\ ·93 \_,------­ ,- ­ . ". " ..96 99·, '­ _____ • ..)' I ·,o~ .' 89 \ "I-­ '( .96 99·' • I •117 '\ 122­ ~ ___ - -"­ 90 '\ 97 , -- . ~ ...... "\--... "'-'"',- ... . _.. . . 'I \ ,­ 119 , " '\ '.8' /'..... • 98 ) 107• , \ /' • ",... 'It " 137, .'.~ 1.9. <' 112 ...... -, \ 108 ( ',.97 '07• , 9~ • 98 " \ -'.) A..'. /'-, . ( 1 13S • , ".J 111 •'-<:'.112 -­ -', \ ~oa 123 " 1~7 / 1 '. J 109"' • ~ ., J 111 • 125 \ " - / ~ 138. { ../ 152· '."3 '. j __ . ,,,' ...... 131 109"" • . . 'I \ (146 / \ " .--,-' _ ,113 ',',I -- /' ", 129 136 _ ...... " • ./ lS0 ,"­ .. , ...--...­ t ~~~~ , • ',__ --r--' . \. ,-­ " ,.,( . / -:.....­ ~ ~/ )' ~/ .. ./ 140. ~. /.,.. .. -'"'-;, -161 .'30 \ 126• \ ,y • J.' / I lSI, 1S~ , 157 160' ,..; -'" /', 139 , I....·... -.,/ ISS. \ • • • • • \ • _, .... I" \ • \ 162 '-::-1-­ ·,61 I 134.­ ---- I < \ .'58 \ .157 • .,,2 \ • 142 '\ 156., .,59 •• 141 • \ \ \ 133 1 153 L 151>. , \ \, . \

o 50 100 e=j r Scale In Miles C.I. 10 Feet. SAND ISOLITH MAP: SUB-CLARKSVILLE 50 N o SAND lSOLlTH MAP: ARCADIA PARK WITH EXPLORATION FAIRWAY Scale In Miles CJ.10 Feet WITH EXPLORATION FAIRWAY N

Fig, 28: Sand isolith of the Sub-Clarksville with exploration fairway, Petroleum production from this widely distributed fairway is limited to major structures. However, due to linear sands and local thinnings, stratigraphic pinchouts in conjunction with minor structural features Fi,. ", ",.d i"Ii'" .f 1M A,~d~ .", wilh ",.,,"i" f....'· Thre' .re...f ,.".tio! "pl'''.'' .,,'" f" A~"'i••", ,odim,""· may have created petroleum traps away from the narrow structural fairways. Of th,~ 1M n.rth"n .u' i. ",oil, ox""i" ... ,,,,bobl' 100 m." """,ti". wilh to,,1 ..nd lhi"''''i .f ,. f"l••ruI inoli,iduo! "od thi""'" ""ot" Ih" 20 f"t. wh<, ,,,d, .f 1M "ulh"""'" f.i,,'" .re IW,. wmuloti" ".,n. , lhi,''''" " highl, """Ii'" S..d, i.lho .oolh''''''" f.""., '" ,,""id"to! with Britt.n " ...... re lhin "d diffi

EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 43 42 BAYLOR GEOLOGICAL STUDIES

potential reservoir sands in the northcentral portion of The sands of the southcentral fairway are thinner than the basin, over parts of seven counties (Fig. 25). Discrete the northern fairway. However, the cumulative reservoir sands are in this area averaging 10 to 15 feet in thickness. thickness is still highly attractive. Individual sand Because these sands are thin, minor structural features thickness averages between 10 to 15 feet. Drilling depths such as low relief faults have the potential to produce range from 2000 feet along the western margin of the effective traps. Drilling depths for Tarrant rocks in this fairway down to 11,000 feet in the southeastern portion. area range from 3700 feet along the northern margins The third fairway for Arcadia Park exploration is in of the fairway down to 5100 feet at the southern the extreme southeastern portion of the basin, boundary of the fairway. coincidental with the Britton accumulation. Arcadia Park Sands are thin and difficult to predict, much like BRITTON EXPLORATION FAIRWAY the Britton. Since the drilling depths range from .11 ,000 The net sand map of the Britton Formation shows to 15,000 feet, this area is high risk for Eagle Ford more widely distributed sands. Three areas of sand exploration. concentrations have reservoir potential (Fig. 26). The northcentral portion of the basin has high reservoir SUB-CLARKSVILLE EXPLORATION FAIRWAY ., potential due to stacking of sands and thickening of The net sands for the Sub-Clarksville are distributed / 1 " .--\.._ . ..." individual sand units offering multiple pay possibilities. throughout most of northcentral east Texas. Petroleum /1 -,' . Britton Sands in this area range to 40 feet in thickness. in these sands, which are generally thick and multiply Drilling depths for Britton rocks in the northern fairway stacked, is produced around major structures. In range from 1700 feet along the northwestern margin of addition, due to the linear sands and local thinnings, .----­'"' # ...... ",.". .. the fairway down to 5400 feet along the southern ..... stratigraphic pinch-outs probably occur in conjunction ."" boundary. with minor structures, which may have created /' The southwestern reservoir fairway extends over parts petroleum traps away from the major structural trends. ) of eight counties. The reservoir sands in this area are Therefore, the Sub-Clarksville fairway has the potential \ thinner and more widely separated than those in the for reservoir development throughout the area of -r·----­ north, averaging between 10 and 15 feet in thickness. deposition (Fig. 28). Drilling depths for this fairway 1,- ______~. Drilling depths in this area range from 2000 feet along extend from 1500 feet along the northern and western ( \, the western margin of the fairway down to 7500 feet margin down to 5000 feet along the southern boundary \ ,...... along the southeastern margin. of the fairway. . -. The third potential fairway occurs in the extreme ET ..... \ ----.-...... '. '. "- .. -­ southeastern portion of the basin. These sands, which OPTIMAL EAGLE FORD : ilutJ£@ "

Fig. 29: Compilation map of the Eagle Ford exploration fairways. Two areas of major interest for Eagle Ford exploration occur. The northern area has sands from all four units stacked at depths from 3000 to 5000 feet. The southern area has sands from both the Britton and Arcadia Park stacked at depths from 2000 to 4000 feet. 44 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 45

CONCLUSIONS northwest of Midlothian, Ellis County, Texas. Calcareous sandstone unnamed gravel road, 1.75 miles north of Highway 82, 2.8 miles west bed with scattered reworked , borings, and small rounded quartz of Kersey Cemetery, Grayson County, Texas. Tan brown massive grains; has channel-like appearance. silty shale. l. The Eagle Ford Group, one of the most complex become more clastic-dominated and preserve the first 12: Arcadia Park-20 foot exposure in road cut on Farm Road 18: Arcadia Park-9 foot section in Iron Ore Creek at intersection clastic units of the upper Cretaceous Gulfian System, evidence of the Sabine activity during late Eagle Ford 1362, .75 miles west of Cedar Hill, Dallas County, Texas. Black fissile with Farm Road 131,3 miles southwest of Denison, Grayson County, has been re-examined throughout the entire basin. deposition. The Sub-Clarksville is the sand-dominated shale beneath the Eagle Ford-Austin contact. Texas. Red silty clay with two mud diapirs. Inside diapirs, mud is 13: Arcadia Park (type locality)-20 foot exposure in railroad cut mottled black and white. Emphasis has been placed on regional relationships, local unit of upper Eagle Ford strata in the northern portions at intersection of Highway 20 and unnamed railroad beneath White 19: Arcadia Park-18 foot section in drainage ditch just north of stratigraphic changes, subdivisions of the group, and of the East Texas basin. Rock escarpment. 6 miles southwest of Dallas, Dallas County, Texas. intersection of Farm Road 131 and Farm Road 691. Large section mapping of sands and source-rocks in depositional sub­ 5. Following a late Woodbine erosional period. Black fissile shale. of dark black fissile shale. units. crustal downwarping set the stage for transgression of 14: Eagle Ford (type locality)-15 foot exposure in river cut on 20: Tan'ant-8 foot section in road cut along Highway 82, just 2. Eagle Ford sediments within the East Texas basin Eaglefordian seas into east Texas. Tarrant deposition , .3 miles east of intersection of Trinity River and Loop east of intersection with Mill Creek, 1.3 miles west of Bells, Grayson 12 (Highway 408), northern limits of the townsite of Eagle Ford, County, Texas. 4 feet of fissile gray shale overlain by a 2 foot resistant are confined by the outcrop on the western and northern marks the initial formation of complex mud-dominated 7 miles west of Dallas, Dallas County, Texas. Black fissile calcareous quartz sandstone bed which is overlain by more shale. margins, the Sabine uplift on the eastern margin, and deltas. Britton deposition marks the maximum extent shale. 21: Sub-Clarksville-5 foot section in bar ditch on east side of Farm the Angelina-Caldwell flexure along the southern of Eaglefordian seas and deposition of the richest source­ 15: Britton-4 foot exposure in Case Creek at intersection with Road 1499, 1.4 miles south ofintersection with Farm Road 197, Lamar margin. rocks in the form of carbon-rich anoxic muds on an Farm Road 902, 2 miles southeast of Ethel, Grayson County, Texas. County, Texas. White silty clay which weathers to red, consists of Laminated shale interbedded with small micritic limestone ledges. small quartz sand bound together in a white clay matrix. Limonite 3. Eagle Ford rocks of east Texas and their equiv­ embayed shallow marine shelf. Arcadia Park deposition 16: Britton-9 foot section in road cut of unnamed gravel road, nodules are spread allover the ground. alents in other upper Cretaceous basins consist mostly began following a late Britton erosional period, and re­ .1 mile east of intersection with another unn;,med gravel road, due 22: Sub-Clarksville-5 foot section in road cut along Farm Road of shale. Generally, the Eagle Ford thins southward out established most of the old deltas, accompanied by east of Hagerman National Wildlife Refuge, .15 miles west of 2648,3 miles east of intersection with Highway 271, Lamar County, of east Texas over the San Marcos platform, and then westwardly prograding deltas shed off the Sabine uplift. Hagerman Baptist Church, Grayson County, Texas. Tan brown Texas. Red silty clay which is white in fresh exposure. Consists of thickens westward to the paleontologically complete Sub-Clarksville deposition, which marks the termination massive silty shale. small quartz sand bound together in a white clay matrix. section of the Chispa Summit Formation in the Davis of Eagle Ford deposition, was a product of a highly 17: Britton-6 foot section in Harris Creek at intersection with Mountains. The Eagle Ford can be closely correlated complex delta system which built seaward from previous with several groups from the Western Interior. deltas and displaced the Eaglefordian seas in east Texas. 4. The Eagle Ford of east Texas is a shale-dominated 6. The Eagle Ford Group of east Texas contains sequence containing localized deltaic and fringing marine highly organic sediments which are sufficiently rich to APPENDIX II sands and consists predominantly of bluish-black have generated the oil produced from reservoirs of Buda, bituminous laminated clays which are sub-divided into Woodbine, Eagle Ford. and Austin age rocks. WELL DATA the Tarrant, Britton, Arcadia Park, and Sub-Clarksville 7. The recommended approach in exploring for Eagle Formations. The Tarrant consists of interbedded Ford oil is usage of the expanded delta model to define sandstone and shale, which records the initial transgres­ exploration fairways for the individual units of the Eagle Well Log Total Well Log Total Well Name sion of the Eaglefordian seas. The Britton consists of Ford. The stacking of these fairways delineates two No. Count~ Date De2th No. Count~ Well Name Date DeEth finely laminated highly organic clays which characterize optimum areas for Eagle Ford exploration. Arcadia Sub- Arcadia Sub- Eagle Ford rocks of east Texas. Arcadia Park sediments Thickness Tarrant Britton Park Clarksville Thickness Tarrant Britton Park Clarksville Arcadia Sub- Arcadia Sub- Net Sands Tarrant Britton Park Clarksville Net Sands Tarrant Britton Park Clarksville Collin Deep Rock I-Shirley 8/21/52 8876 12 Kaufman Gibson Drlg. I-Lupe 4/8/57 3050 90 130 145 55 75 170 100 50 APPENDIX I 0 0 10 15 0 0 10 18 2 Collin Manziell-Alexander 9/13/47 5667 13 Van Zandt Trinity Drilling l-{No Name) 8/19/49 4488 OUTCROP LOCALITIES 71 174 170 45 105 200 120 60 0 8 14 22 18 34 24 26 3 Fannin Lynn I-Brown 3/11/52 5103 14 Van Zandt Cooper-Herring I-Gibbs 10/9/52 4235 LOCALITY Highway 81 behind the VFW hall, Hillsboro, Hill County, Texas. 60 190 120 70 130 125 85 55 I: South Bosque (Arcadia Park)-I 5 foot exposure in Foster Creek Interbedded laminated clay, bentonite, and thin limestones composed 0 33 18 24 10 38 24 40 by an unnamed gravel county road, 4.3 miles east-northeast of Moody, of reworked prisms. 4 Fannin Hawkins I-Shelton S/3/54 4153 15 Van Zandt Hootkins I-Persons 7/24/60 6984 Mclennan County, Texas. Blue gray fissile calcareous mudstone with 7A: Arcadia Park-4 foot exposure at the intersection of Farm 85 175 165 250 133 130 160 85 thin laminae of siltstone, sandstone, and fragmental limestone. Road 67 and Cottonwood Creek, 5 miles north-northeast of Itasca, 8 40 18 40 14 16 16 42 2: South Bosque (Arcadia Park)-46 foot total exposure in unnamed Hill County, Texas. Massive blocky shale which weathers to a tan 5 Hunt Humble I-Anderson Not Given 6271 16 Van Zandt Fair I-Swinney 11/7/47 3718 tributary of South Bosque River, 5.2 miles south-southeast of orange. 35 225 105 62 50 137 64 97 McGregor Airport entrance on unnamed gravel road between Farm 7B: Arcadia Park-3 foot exposure 1.2 miles east of 7A, at the 8 32 18 30 12 26 10 4 Roads 2416 and 2837, Mclennan County, Texas. Blue gray fissile intersection of the eastern branch of Itasca Creek and unnamed gravel 6 Hunt Cox I-Hill 10/27/60 9482 17 Rains Delta I-Dowell 3/24/54 3921 to blocky shale with thin micritic limestone beds near the base of road towards Maypearl, Hill County, Texas. Bedded fissile shale which 75 210 40 155 90 205 140 100 the section. weathers to a buff color. 0 0 0 55 10 32 26 37 3: Lake Waco (Britton), Cloice Member-56 feet total exposure 8: Tarrant-3 foot exposure at intersection of the north fork of 7 Hunt Pan Am I-Cooksey 9/4157 9501 18 Rains Coats Drlg. I-John Coats 2/ 1/53 6603 in unnamed tributary of South Bosque River in Midway Park, Chambers Creek and Farm Road 1807, 1.5 miles southeast of 125 210 ISO 128 115 145 165 92 Woodway, Mclennan County, Texas. Laminated montmorillonitic Alvarado, Johnson County, Texas. Interbedded fossiliferous 5 18 32 28 10 27 10 38 clays with disseminated calcium carbonate, abundant bentonite, and limestone, red-gray clay, and sandstone near base of Eagle Ford 8 Hunt Humble I-Graham Not Given 5990 19 Hopkins Amoco I-Matherly 5/18/14 9925 limestone beds near the top of the section. section. 65 205 143 95 105 135 215 155 4: Lake Waco (Britton), Cloice Member-I 6 feet of section exposed 9: Arcadia Park-4 foot exposure in the western branch of Bagby 6 19 26 41 22 40 46 91 along a bar ditch of unnamed county road, .5 miles south of Farm Creek, .4 miles south of Farm Road 1807, I mile west of intersection 9 Rockwall Farmer I-Herndon 6/10/56 3955 20 Hopkins Sunray I-Seamon 12/29/63 12183 Road 2114. Intersection of unnamed road and Farm Road 2114 is of Farm Road 1807 and 157, Johnson County, Texas. Fissile shale 145 160 160 80 170 65 210 160 2.5 miles west of the town of West, Mclennan County, Texas. with concretions ranging up to 6 inches in diameter. 4 12 32 28 22 38 14 123 Laminated blue gray shale interlaminated with bentonite. 10: Arcadia Park-30 foot exposure along the west loop of Highway 10 Rockwall Rotary I-Lewis 3/21/65 7876 21 Hopkins McAlester I-Helm 11/25162 11812 5: Britton-8 foot section in Aquilla Creek at intersection with Farm 67,.2 miles south ofintersection with Highway 287, west of Midlothian, 110 185 140 60 100 120 80 70 Road 2114, Mclennan County, Texas. Laminated blue gray to black Ellis County, Texas. Blocky to fissile black shale with bedded calcite­ 6 0 12 10 6 8 0 0 shale. pyrite concretions 20 feet beneath the Eagle Ford-Austin contact. 11 Kaufman Hughes I-Jones 11/16/74 10000 22 Hopkins Grelling I-Thompson 1/25/59 10449 6: Britton-8 foot exposure at the intersection of Highway 71 and II: Britton-3 foot exposure in road cut on Highway 287, 2.5 miles 113 180 97 73 110 95 90 60 4 12 12 23 10 18 0 20 EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 47 46 BAYLOR GEOLOGICAL STUDIES

Well Log Total Well Log Total Well Log Total Well Log Total No. County Well Name Date Depth No. County Well Name Date Depth No. County WelI Name Date Depth No. County Well Name Date Depth Arcadia Sub- Arcadia Sub­ Arcadia Sub­ Arcadia Sub- Thickness Tarrant Britton Park Clarksville Thickness Tarrant Britton Park Clarksville Thickness Tarrant Britton Park Clarksville Thickness Tarrant Britton Park Clarksville Arcadia Sub­ Arcadia Sub­ Arcadia Sub­ Arcadia Sub­ Net Sands Tarrant Britton Park Clarksville Net Sands Tarrant Britton Park Clarksville Net Sands Tarrant Britton Park Clarksville Net Sands Tarrant Britton Park Clarksville 67 Smith GreJling and Oldham I-Pope 8/31/55 4041 10150 23 Delta Bond I-Albowitch 5/21/60 5893 45 Cass Gilger I-Davis et al. Not Given 6043 89 Cherokee Tel(.aco I-Whiteman 6/10/52 0 23 o 90 170 237 233 40 o o 40 32 o o o o 004 o 15 66 32 122 o o o 000 o o 68 Gregg Euon I-McCubbin 2/23/83 12017 18120 24 Delta Naylor I-Young 12/13/59 7804 46 Camp Humble I-Carpenter 9/ 4/70 12444 90 Cherokee Teuco I-Dean 5/24/73 000 o 100 110 160 125 50 55 115 40 000 o 000 48 26 46 78 22 15 20 32 o 000 o 69 Gregg Key Prod. 4-Adkin-Ross 3/5/82 7806 9094 25 Delta Kirkwood I-Foster 7/9/49 3212 47 Camp Humphrey I-Nickerson 2/ 28/ 67 10725 91 Cherokee Hansbro I-Bolton 2/ 13/51 000 o 95 145 200 75 40 40 90 50 000 o 000 12 33 66 40 8 10 22 35 o 000 o 70 Gregg Ward Oil2-Bodenheim Gas 5/5/66 11820 10964 26 Lamar D. and D. Drlg. I-Morton 9/1/48 2935 48 Camp Sun I-Dyer 9/2/81 8872 92 Rusk Hinton I-Childress 4/18/42 000 84 145 165 85 45 45 145 100 o 000 o 000 o 5 45 45 20 o 18 32 48 000 o 71 Dallas South Tel(.as Pet. I-Stadden 8/9/72 2202 8194 27 Lamar Stephens I-Tidwell . 4/11/80 2338 49 Wood Sohio I-Morgan Not Given 6579 93 Rusk Ft. Bend I-Barron 3/31/72 75 250 70 45 110 140 130 70 65 30 90 55 000 o 25 68 40 16 12 34 30 25 4 16 20 000 o o 72 Ellis Faulds Whitehead I-Curtis Hill 1/15/60 3629 28 Lamar Hagar I-Gardner 5/12/51 5417 50 Wood Felder and Erwin I-Hulsey 12/11/51 5815 94 Rusk J. C. Trahan 16-Tatum Crane 6/16/62 7068 90 235 45 40 220 240 200 255 70 90 90 95 000 o 6 10 21 55 39 76 75 12 14 14 29 o 000 o Cain I-Patak 5/26/53 3673 29 Lamar Cosden I-Adams Not Given 3050 51 Wood Southland I-Judge 73 Ellis 95 Rusk J. P. G. Oil 2-Troy Welch 1/18/66 7391 1015/56 9507 80 255 45 30 95 125 140 110 68 105 80 120 000 o 23 16 10 25 15 22 58 10 5 14 o o 000 o 74 Ellis Banks I-Southard 3/6/71 17344 9301 30 Red River Hager 3-Tate 10/26/59 2716 52 Wood Shell 1-Highnote 12/28/52 5189 96 Nacogdoches Palmer I-Sitton McLain 101 23/82 70 165 32 58 85 85 105 125 52 32 60 70 000 o 040 6 8 5 20 25 10 20 6 16 000 o 75 Hill Dalton J. Woods I-Estes 8/14/47 1258 7944 31 Red River Bowden I-Welch 11/20/49 3087 53 Upshur McBee and Rudman I-Ray 5/18/77 10768 97 Nacogdoches Tes. Gen. Pet. I-Byrd 4/5/82 105 100 o 80 40 135 110 0 65 20 o 000 o o o 14 18 o 6 4 50 36 o 0 16 20 000 o 76 Navarro Falcon I-Keitt 8/8/42 6455 9689 32 Red River Lee I-Stiles 12/13/53 5008 54 Upshur Edson I-Payton 1/4/64 8127 98 Nacogdoches Palmer I-Simpson Adams 11/3/8-1 15 125 80 17 55 45 120 145 0 30 65 000 o o 066 2 5 5 18 28 000 36 000 o 77 Navarro Amoco I-Cunningham 4/27/80 10154 33 Bowie Hill and Mclean I-Jackson 8/2/61 9591 55 Upshur McBee and Rudman I-Indian Ro. 11/17/72 12205 99 Nacogdoches Bancroft-Watson I-Martindale 2/10/75 8137 1M 20 35 75 45 80 0 33 90 90 000 o o o 20 10 14 18 12 55 000 o 8 000 o o Sundance I-Arnett 7512 34 Bowie Coats I-Sims 12/29/48 3853 78 Navarro 12/ 12/78 100 Panola Carter and Jones I-Crawford 4/2/57 7133 56 Upshur Teuco I-Newsome 1/17/67 11797 60 20 20 70 90 145 138 102 000 o o 0 85 60 20 IS 27 5 10 10 o 000 o o 004 13 7638 35 Bowie Pan Am I-Bradham 10/21/66 6506 79 Henderson Humphrey I-Key 2/4/55 101 Panola Arkla I-Cummings 9/10/44 4950 57 Marion Magnolia I-Hall 2/14/47 10014 30 o o 43 75 e I" 90 000 o 000 o 16 6 18 10 000 o o o o 000 o o 80 Henderson Delta 3A-Hustead 5/13/55 7535 102 Panola Arkla 2-Hardin 12/4/52 6125 36 Bowie Barnsdall I-Greenwood 3/16147 8188 58 Marion Hollandsworth I-Mathis 9/4/56 6204 60 145 78 37 000 o o 0 50 o 000 o 0 o o 0 25 20 000 o o o 000 o Lonestar I-Dil(.ie Killough 8216 37 Franklin Graves I-Jones 9/30/82 6684 81 Henderson 10/19/47 103 Panola Blalock and Walter I-Sabine 11/17/54 6081 59 Marion Purnell 1-Deltic 2/13/60 6409 75 101 140 SO 50 95 125 90 000 o 000 o 35 19 32 32 43 14 47 37 000 o 000 o Windsor I-Burkhart 5523 38 Titus Pal(.ton, et al. I-Burford-AI. 12/23/65 12133 82 Henderson 11/23/53 104 Shelby Champlin I-Langston 12/18/80 10286 60 Harrison Placid I-Allen 5/20/47 8006 23 45 100 145 120 90 60 125 000 o 000 o 16 25 35 17 8 43 69 51 000 o 000 o 10987 39 Titus Stephens I-Driggers 1/6/62 7575 83 Henderson British Am. I-Anderson 7/17/66 105 Shelby Carter-Jones I-Pickering 4/8/58 7323 61 Harrison Norton I-Neal 4/6/58 7243 110 145 45 45 90 170 145 o 000 o 000 o 38 6 16 74 78 o 20 40 000 o 000 o 7596 40 Titus Hinton l-Stephenson 3/ 14/ 50 4898 84 Van Zandt Byrd I-Byrd 1/5/52 106 Shelby Coats I-Pickering 12/ 1/59 7000 62 Harrison Gilster and Kemp I-Allen 8/23/54 7535 49 125 105 65 47 88 195 115 o 0 o o 000 o 27 18 34 8 16 88 68 o o 0 o o 000 o TXO Prod. I-Glenn 9537 41 Morris Humble I-Wright 1/27/44 11810 85 Anderson 2/23/83 107 San Augustine Fairway I-Matthews 4/23/63 9187 63 Harrison Phillips I-Valley 6/5/51 8358 195 135 60 40 45 ISO 125 o o o o o 000 o 000 25 o o o 6 14 30 65 000 o o 86 Anderson Continental 2-Royal Nat. Bank 3/14/52 9864 108 San Augustine Carter-Jones I-Long Bell 3/6/56 9154 42 Morris Hunt I-Robinson 11/ 10/45 8431 64 Smith Howard I-Waters 12/13/54 5809 o 128 110 25 000 o 25 50 120 130 90 105 140 65 o 0 10 25 000 o 6 18 24 51 20 20 21 4 87 Anderson Phoenil(. I-Mathis 9/30/79 12503 109 San Augustine Lester-Culbertson I-Childers 8/28/ 53 10029 43 Cass Phillips I-Leonard 5/ 18/62 10725 65 Smith Talbert and Gulley I-Simpson 5/18/57 5958 o 90 90 o 000 o o 70 o 45 105 110 o 60 o 0 29 o 000 o o o o o 6 16 43 17 88 Anderson Herring I-Carpenter 1/26/64 8426 110 Sabine Humble I-Harvey 12/19/ 72 7073 44 Cass Shell I-Smith Not Given 10801 66 Smith Pure Oil I-Lolley 11/22/50 4325 o 96 98 o 000 o o o 90 o 35 0 55 25 o 5 25 o 000 o o o o o o 0 17 12

~, 2~~?:{;";:~:"':"" I' ,;,,:~!\l 48 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 49

Well Log Total Well Log Total No. County Well Name Date Depth No. County Well Name Date Depth Well Log Total Well Log Total No. County Well Name Date Depth No. County Well Name Date Depth Arcadia Sub- Arcadia Sub- Thickness Tarrant Britton Park Clarksville Thickness Tarrant Britton Park Clarksville Arcadia Sub- Arcadia Sub- Thickness Tarrant Britton Park Clarksville Thickness Tarrant Britton Park Clarksville Arcadia Sub­ Arcadia Sub­ Net Sands Tarrant Britton Park Clarksville Net Sands Tarrant Britton Park Clarksville Arcadia Sub­ Arcadia Sub­ Net Sands Tarrant Britton Park Clarksville Net Sands Tarrant Britton Park Oarksville III Sabine Millican lA-Temple 10/28/72 8104 133 Brazos Cayuga Expl. I-Wooten 3/27/18 12298 000 o o 50 95 o 155 Polk Wainoco I-Carter Bros. 12/27173 12274 160 Tyler Kelly-Brock 2-Arco-Abbott 3/22/73 10277 000 o o 20 15 o o 20 0 o 000 o 112 Angelina Gulf I-Angelina Lbr. 11/3/64 11310 134 Brazos Williams I-Payne Not Given 11345 050 o 000 o 000 o o 75 70 o 156 Polk Shell I-Southland Paper 7/1/62 15150 161 Jasper Kelly-Brock I-Arco Huling 2/20/18 11222 000 o o 14 8 o o 295 149 o 000 o 113 Angelina Southland Paper I-Copes Hiers 12/27/63 10987 135 Leon Tenneco I-Diehl 10/25/82 14643 000 o 000 o 000 o o 135 35 o 157 Tyler Amoco I-Kirby Trust 6/17/72 11095 162 Jasper C.K. Pet. I-Cameron Heirs 8/4/15 13158 000 o o 20 10 o o 20 0 o o 48 0 o 114 McLennan J.L. Myers Sons I-Elk City 1/21/64 2902 136 Leon Tipco I-Hilltop 12/21/77 11542 000 o 000 o o 65 163 o o 92 48 o 158 Tyler Delta I-Carter 3/2/74 17000 163 Newton Pan. Am. I-Brown 11/2/62 14111 040 o o 14 8 o o 100 183 o o 65 70 o 115 McLennan Porter I-Kophlll 4/10/57 1405 137 Leon Humble I-Lester Foran 8/12/73 9720 o 30 0 o 000 o o 80 173 o o 127 68 o 159 Tyler La. Land and Exp. I-Int. Paper 6/2178 15138 164 Newton A.N.P. Prod. I-Southern Pines 2/8/81 13717 o 6 15 o o 10 22 o o 190 240 o o 145 80 o 116 McLennan Chapel Hill I-Waco Water Well 3/19/57 2091 138 Leon Burnett I-Max Rogers 1/28/11 8008 o 32 50 o 000 o o 128 133 o o 120 lOS o o 10 24 o o 6 57 o 117 Limestone Hunt I-Union Central Life 12/1/48 5195 139 Madison Anardarko I-Hightower 11/4/74 12999 o 129 106 o o 95 55 o o 14 30 o o 6 14 o 118 Limestone Wise and Windfohr I-Collins 2/24/49 2299 140 Madison Sinclair I-Irene Waist 3/13/65 11017 APPENDIX III o 197 130 o o 55 55 o o 12 38 o o 6 25 o SOURCE-ROCK DATA 119 Limestone Humble I-Muse 5/4/55 8223 141 Grimes Wainco I-Davis 2/23/79 11435 o 193 92 o o 80 50 o o 16 17 o o 15 10 o LABORATORY PROCEDURE 120 Freestone Lonestar I-Miller 5/17/72 12122 142 Walker Skelly OUI-Gibbs "A" 3/1/66 15969 The following laboratory procedure was modified from the Geochem 4. Samples were treated with phosphoric acid (H,Po.), washed with 30 170 170 o o 50 45 o Laboratories' Source-Rock Evaluation Manual ( 1980). distilled water, then dried in an oven set at 80° Celsius. (Liquid was o 10 24 o o 14 20 o I. Rock samples were obtained from outcrops and cuttings from leached through samples by a vacuum suction during treatment.) 121 Freestone Wilson I-Utsay Not Given 8125 143 Walker Lonestar I-Central Coal-Coke 12/ 16/72 16109 wells drilled in the East Texas basin. 5. Samples were run through a LECO automatic carbon 30 110 222 o o 40 50 o 2. Samples were ground until they fit through a 100 mesh screen. determinator in conjunction with a LECO induction furnace at the o 8 9 o 080 o 3. Samples were measured in disposable crucibles. Sample weight Arco Research Laboratory in Plano, Texas. Iron chips and copper 122 Freestone Humble 3·RLGU Not Given 9384 144 Walker Union Prod. I-Smither 8/11/56 11706 varied between 0.2 and 1.8 grams. were added as accelerator. o 160 105 15 o 80 80 o o 5 4 o 10 18 o 123 Falls Jenkins and Perkins I-Porter 1/17/51 1102 145 Houston Wessely I-Wilcox 10/3/80 11648 Sample Sample Depth o 176 75 o o 87 65 o No. Local. County Well Name/Outcrop Interval o 8 10 o o 10 6 o 124 Falls Humble I-Elanor Carroll 8/16/51 3718 146 Houston Marshall I-Odom 2/8/83 10893 Sample Wt. o 78 52 o o 45 20 o (grams) % Carbon o 6 12 o o 6 35 o 0-1 McLennan Locality I 125 Falls Harry Sheaves I-Woodfin 5/21/66 2709 147 Houston Apexco I-Strong 2/16/78 12992 0.645 6.624 o 105 65 o o 0 o o 2 0-1 McLennan Locality I o 8 16 o o 0 o o 0.833 5.463 126 Milam Rim Rock Tidelands I-Crawford 5/8/56 6995 148 Houston Inexco I-Davy Crockett 3/10176 11501 3 0-1 McLennan Locality I o 85 45 o o 42 48 o 0.335 4.322 o 4 10 o o 10 17 o 4 0-1 McLennan Locality I 127 Milam D. H. Byrd I-Green 5/23/53 8209 149 Houston Kirby I-Williams 7/31174 11721 1.061 6.154 o JI3 50 o o 15 0 o 5 0-1 McLennan Locality I o 15 25 o 000 o 0.842 6.129 128 Milam Gen. Crude I-Coffield 3/15/60 6737 150 Trinity Goldking I-Joyce 2/ 10/80 11719 0·1 Average =5.74% o 89 56 o o 47 35 o 6 0-2 McLennan Locality 2 024 o o 10 20 o 0.3975 5.701 129 Robertson Caraway I-Yezak 7/28/66 9589 151 Trinity Amoco I-Trinity Lumber 8/1/80 11582 7 0-2 McLennan Locality 2 o 50 33 o o 65 80 o 0.681 5.292 o 20 6 o o 10 15 o 8 0-2 McLennan Locality 2 130 Robertson Humble I-Margie Michael 7/30/68 17260 152 Trinity Shell I-Temple 6/19171 18035 1.111 5.352 o 55 20 o 000 o 9 0-2 McLennan Locality 2 o 10 12 o 000 o 0.983 4.369 131 Robertson Hammon I-Corn 9/ 12/73 12712 153 San Jacinto Glen Rose I-Central Coal-Coke 10/2/74 16468 10 0-2 McLennan Locality 2 o 100 42 o o 87 70 o 1.114 5.785 o 18 12 o o 0 o 0·2 Average =5.299% 132 Brazos McCarthy I-Holliday 11/24/65 10975 154 Polk Am. Libr. et al. I-Cameron 9/ 14/54 12701 11 0-3 McLennan Locality 3 o 105 75 o o 35 0 o 0.215 8.314 068 o o 0 0 o 12 0-3 McLennan Locality 3 0.454 9.825

., ,'1l.ift~..'!tJfiiaa ...... 50 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 51

Sample Sample Depth Sample Sample Depth No. Local. County Well Name/Outcrop Interval No. Local. County Well Name/Outcrop Interval Sample Wt. Sample Wt. (grams) % Carbon (grams) %Carbon 13 0-3 Mclennan Locality 3 1.183 1.052 0.726 9.598 SR-3 (lower) Anrage = 1.255% 14 0-3 Mclennan Locality 3 SR-3 Average = 1.116% 1.056 10.040 44 SR-4 Tyler Humble I-Howell 14767 15 0-3 Mclennan Locality 3 0.452 0.9353 0.354 8.145 45 SR-4 Tyler Humble I-Howell 14767 0·3 Average = 9.18% 0.685 0.9303 16 0-7 Ellis Locality 10 46 SR-4 Tyler Humble I·Howell " (4767 0.305 1.452 1.162 0.9108 17 0-7 Ellis Locality 10 SR-4 (14767) Anrage = 1.925% 0.604 1.402 47 SR-4 Tyler Humble I·Howell 14803 18 0-7 Ellis Locality 10 0.468 1.373 0.868 1.451 48 SR-4 Tyler Humble I-Howell 14803 19 0-7 Ellis Locality 10 0.709 1.220 1.080 1.113 49 SR-4 Tyler Humble I-Howell 14803 20 0-7 Ellis Locality 10 1.141 1.342 0.882 1.687 SR-4 (14813) Anrage 1.31% 0.7 Average = 1.411 % 50 SR-4 Tyler Humble I-Howell 14816 21 0-16 Grayson Locality 17 0.389 1.976 0.307 2.611 51 SR-4 Tyler Humble I·Howell 14816 22 0-16 Grayson Locality 17 0.723 2.177 0.531 2.617 52 SR-4 Tyler Humble I-Howell 14816 23 0-16 Grayson Locality 17 1.206 2.227 0.841 2.684 SR-4 (14816) Average = 2.127% 24 0·16 Grayson Locality 17 SR·4 Average 1.45% 1.133 2.650 53 SR-5 Rockwall Riek I-Whilden 1430 25 0-16 Grayson Locality 17 0.335 1.069 0.900 2.658 54 SR-5 Rockwall Riek I-Whilden 1430 0.16 Average 2.64% 0.681 1.188 26 SR-I Hunt Barnsdall I-Hielbron 860-1000 55 SR·5 Rockwall Riek I-Whilden 1430 0.397 1.451 1.240 1.112 27 SR-I Hunt Barnsdall 1-Hielbron 860-1000 SR-5 (upper) Average ='1.12% 0.757 1.518 56 SR-5 Rockwall Riek I-Whilden 1585 28 SR·I Hunt Barnsdall I-Hielbron 860-1000 0.446 1.190 1.065 1.305 57 SR-5 Rockwall Riek I-Whilden 1585 29 SR-I Hunt Barnsdall I-Hielbron 860-1000 0.799 1.132 1.299 0.823 58 SR-5 Rockwall Riek I-Whilden 1585 SR-t Average = 1.27% 1.085 1.234 30 SR-2 Red River Hinton I-Pryor 566-721 SR·5 (middle) Average = 1.19% 0.417 0.659 59 SR·5 Rockwall Riek I-Whilden 1605 31 SR-2 Red River Hinton I-Pryor 566-721 0.391 2.461 0.634 0.771 60 SR-5 Rockwall Riek I-Whilden . 1605 32 SR-2 Red River Hinton I-Pryor 566-721 0.791 0.6604 0.931 0.683 61 SR-5 Rockwall Riek I-Whilden 1605 33 SR-2 Red River Hinton I-Pryor 566-721 1.500 1.070 1.111 0.611 SR·S (lower) Average =1.397% SR·2 (upper) Average = 1.68% SR·5 Average = 1.14% 34 SR-2 Red River Hinton I-Pryor 875·1000 62 SR-6 Cass Arkansas I·Duncan 3150-3330 0.301 2.452 0.385 0.7928 35 SR-2 Red River Hinton I-Pryor 875-1000 63 SR·6 Cass Arkansas I-Duncan 3150-3330 0.793 1.081 0.7360 0.7117 36 SR-2 Red River Hinton I·Pryor 875-1000 64 SR-6 Cass Arkansas I-Duncan 3150-3330 1.029 0.888 1.169 0.7143 37 SR-2 Red River Hinton I-Pryor 875-1000 SR..(i Average = 1.7396% 1.223 1.567 65 SR-7 Wood Ace I-Winchester 4600-4650 SR-2 (lower) Average = 1.49% 0.408 1.081 SR·2 Average = "19% 66 SR-7 Wood Ace I-Winchester 4600-4650 38 SR-3 Lamar Kamann I-Bywater 855-880 0.872 0.9954 0.387 1.047 67 SR-7 Wood Ace I-Winchester 4600-4650 39 SR-3 Lamar Kamann I-Bywater 855-880 1.170 0.9555 0.557 0.968 SR-7 (upper) Average = 1.111% 40 SR-3 Lamar Kamann I-Bywater 855-880 68 SR-7 Wood Ace I-Winchester 4700-4750 1.060 0.918 0.456 0.9983 SR·3 (upper) Average =1.977% 69 SR-7 Wood Ace I-Winchester 4700-4750 41 SR-3 Lamar Kamann I-Bywater 920-980 0.853 1.005 0.343 1.267 70 SR-7 Wood Ace I-Winchester 4700-4750 42 SR-3 Lamar Kamann I-Bywater 920-980 1.149 0.9943 0.756 1.436 SR-7 (middle) Average =1.999% 43 SR·3 Lamar Kamann I-Bywater 920-980 71 SR-7 Wood Ace I-Winchester 4800-4850 52 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 53

Sample Sample Depth No. Local. County Well Name/Outcrop Interval Sample Sample Depth No. Local. Sample Wt. County Well Name/Outcrop Interval !sramsl % Carbon Sample Wt. 0.437 0.9557 !srams! % Carbon 72 SR-7 Wood Ace I-Winchester 4800-4850 100 SR-13 Hunt Humble I-Anderson 1549-1701 0.967 0.8894 1.336 2.825 73 SR·7 Wood Ace I-Winchester 4800-4850 SR-13 (upper) Average:: 1.04% 1.353 0.9026 101 SR-13 Hunt Humble I-Anderson 1828-1980 SR-7 (lower) Average:: 0.9159% 0.405 1.106 SR-7 Average:: 0.97% 102 SR-13 Hunt Humble I-Anderson 1828-1980 74 SR-8 Morris Coats I-Reese 2395-2485 0.830 1.035 0.376 0.8442 103 SR-13 Hunt Humble I-Anderson 1828~198O 75 SR-8 Morris Coats I-Reese 2395-2485 1.262 1.121 0.770 0.8450 SR-13 (lower) Average:: 1.09% 76 SR·8 Morris Coats I-Reese 2395-2485 SR·13 Average:: 1.5fi% 1.155 0.8112 104 SR-14 Hopkins Shell I-Hedrick 2290-2440 SR-S (upper) Average :: 0.8335% 0.330 1.281 77 SR-8 Morris Coats I-Reese 2530-2605 105 SR-14 Hopkins Shell I-Hedrick 2290-2440 0.375 0.8665 0.917 0.9781 78 SR-8 Morris Coats I-Reese 2530-2605 106 SR-14 Hopkins Shell I-Hedrick 2290-2440 0.772 0.7518 1.254 .0.9477 79 SR-8 Morris Coats I-Reese 2530-2605 SR·14 (upper) Average:: 1.07% 1.112 0.753 107 SR·14 Hopkins Shell I-Hedrick 2590-2740 SR-S (1ower) Average:: 0.79% 0.451 1.013 SR-S Average:: O.SI% 108 SR-14 Hopkins Shell I-Hedrick 2590-2740 80 SR-9 Henderson Am. Liberty I-Larve 5190-5250 0.827 0.9042 0.426 1.009 109 SR·14 Hopkins Shell I-Hedrick 2590-2740 81 SR-9 Henderson Am. Liberty I-Larve 5190-5250 1.179 0.8177 0.898 0.9809 SR-14 (lower) Average:: 0.91% 82 SR-9 Henderson Am. Liberty I-Larve 5190-5250 SR·14 Average:: 0.99% 1.372 0.8070 110 SR-15 Franklin Byars I-Clifton 3100-3260 SR·9 Average:: 0.93% 0.256 15.74 83 SR-IO Fannin City of Trenton I-W.W. 429-613 111 SR-15 Franklin Byars I-Clifton 3100-3260 0.557 8.119% 0.640 11.35 84 SR-II Delta Freedman I-Deering 1870-2020 112 SR-15 Franklin Byars I-Clifton 3100-3260 0.437 0.9226 1.224 4.493 85 SR-II Delta Freedman I-Deering 1870-2020 SR-15 (upper) Average :: 10.53% 0.853 1.132 113 SR-15 Franklin Byars I-Clifton 3367-3547 86 SR-Il Delta Freedman I-Deering 1870-2020 0.411 0.893 1.314 1.667 114 SR-15 Franklin Byars I·Clifton 3367-3547 SR·ll (upper) Average:: 1.14% 0.582 2.538 87 SR·II Delta Freedman I·Deering 2210-2390 115 SR·15 Franklin Byars I-Clifton 3367-3547 0.447 0.9839 1.240 1.432 88 SR-II Delta Freedman I·Deering 2210-2390 SR-15 (lower) Average :: 1.61% 0.883 1.009 SR-15 Average:: 6.07% 89 SR·II Delta Freedman I-Deering 2210-2390 116 SR-16 Cherokee Humble I·Maness 5820-5940 1.310 1.I38 0.511 1.040 SR·lI (lower) Average:: 1.04% 117 SR-16 Cherokee Humble I-Maness 5820-5940 SR-ll Average:: 1.14% 0.882 2.251 90 SR·12 Anderson Killam I-McKee 4890-4950 118 SR-16 Cherokee Humble I-Maness 5820-5940 0.424 0.891 1.222 2.667 91 SR-12 Anderson Killam I-McKee 4890-4950 SR·16 (upper) Average:: 1.9S% 0.773 0.808 119 SR·16 Cherokee Humble I-Maness 6030-6150 92 SR-12 Anderson Killam I·McKee 4890-4950 0.465 1.385 1.51 I 0.549 120 SR·16 Cherokee Humble I-Maness 6030-6150 SR·ll (upper) Average 0.749% 0.882 1.757 93 SR-12 Anderson Killam I-McKee 5010-5100 121 SR·16 Cherokee Humble I·Maness 6030-6150 0.398 0.928 1.217 2.479 94 SR-12 Anderson Killam I-McKee 5010-5100 SR·16 (lower) Average:: 1.87% 0.977 0.732 SR·16 Averale:: 1.93% SR·ll (middle) Average:: 0.897% 122 SR·17 Cherokee Humble I·Martin 4315-4328 95 SR·12 Anderson Killam I-McKee 5175-5230 0.377 0.876 0.418 0.977 123 SR-17 Cherokee Humble I-Martin 4315-4328 96 SR-12 Anderson Killam I·McKee 5175-5230 0.578 0.956 0.852 0.956 124 SR-17 Cherokee Humble I-Martin 4315-4328 97 SR-12 Anderson Killam I-McKee 5175-5230 1.217 0.857 1.291 1.172 SR·17 Averale:: 0.90% SR·ll (lower) Averale:: 1.035% 125 SR·18 Kaufman Atlantic Ref. I·Griffith 3240·3280 SR-ll Average:: 0.90% 0.333 0.974 98 SR-13 Hunt Humble I·Anderson 1549-1701 126 SR·18 Kaufman Atlantic Ref. I·Griffith 3240-3280 0.384 1.775 0.770 1.229 99 SR·13 Hunt Humble I·Anderson 1549·1701 127 SR-18 Kaufman Atlantic Ref. I·Griffith 3240-3280 0.761 1.525 1.150 1.205 54 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP, SOURCE-ROCK POTENTIAL 55

Sample Sample Depth Sample Sample Depth No. Local. CountI Well Na,melOutcr01! Interval No. Local. CountI Well NamelOutcr01! Interval SampleWt. Sample Wt. !sramsl % Carbon !lramsl % Carbon SR·18 (upper) Average =1.14% 156 SR-24 Titus Coats I-Scott Lizzie 3030-3090 128 SR·18 Kaufman Atlantic Ref. I-Griffith 3350·3380 0.766 0.7381 0.389 1.393 157 SR·24 Titus Coats I-Scott Lizzie 3030-3090 129 SR-18 Kaufman Atlantic Ref. I-Griffith 3350-3380 1.538 0.6087 0.733 L264 SR·14 (upper) Averale =0.75% 130 SR-18 Kaufman Atlantic Ref. I-Griffith 3350-3380 158 SR-24 Titus Coats I-Scott Lizzie 3120-3170 L234 1.318 0.307 0.828 SR·l. (middle) Averale = 1.33% 159 SR-24 Titus Coats I-Scott Lizzie 3120-3170 131 SR·18 Kaufman Atlantic Ref. I·Griffith 3470·3480 0.746 0.7907 0.410 LS57 160 SR-24 Titus Coats-Scott Lizzie 3120-3170 132 SR-18 Kaufman Atlantic Ref. I-Griffith 3470-3480 1.355 1.044 0.743 1.144 SR·1" (middle) Averale =0.89% 133 SR-18 Kaufman Atlantic Ref. I-Griffith 3470-3480 161 SR-24 Titus Coats I-Scott Lizzie 3230-3295 1.241 1.327 0.461 0.999 SR·l. (lower) Average =1.44% 167 SR-24 Titus Coats I-Scott Lizzie 3230-3295 SR·18 Average 1.30% 0.642 0.9282 134 SR-19 Wood Humble I-Robinson 4409 168 SR-24 Titus Coats I-Scott Lizzie 3230-3295 0.488 1.027 1.127 0.9022 135 SR-19 Wood Humble I-Robinson 4409 SR·1" (lower) Averale =0.94% 0.927 0.958 SR·1" Averale =0.86% 136 SR-19 Wood Humble I-Robinson 4409 1.242 0.962 SR·19 Average =0.98% 137 SR-20 Smith Arkansas Fuel I-Marsh 3470 0.485 LOl2 138 SR-20 Smith Arkansas Fuel I-Marsh 3470 APPENDIX IV 0.927 0.9586 139 SR·20 Smith Arkansas Fuel I-Marsh 3470 CALCULATIONS: POTENTIAL OIL GENERATED 1.255 1.172 PROCEDURE SR·lO Averale =1.03% Kerogen 140 SR-21 Navarro Collins I-Green Lee 1402-1591 The following procedure was adapted from Bishop et aI. (1984, Thickness Residual Quantity 0.395 0.857 p. 44) for estimating kerogen quantity in a petroleum-generative prov­ Province !ft! Area!mi2! Area tft2! Carbon !ftl! 141 SR·21 Navarro Collins I-Green Lee 1402·1591 ince as an indicator of volume of oil generated (Fig. 24). The equation 0.780 0.748 used is: a. 400 462.4 1.3 X 1010 1% 5.1 X 10 10 142 SR-21 Navarro Collins I·Green Lee 1402·1591 b. 500 1329.6 3.7 X 1010 1% 1.8 X 1011 1.186 0.7632 c. 600 876.8 2.4 X 1010 1% 1.5 X 1011 SR·l1 (upper) Averale =0.77% Effective d. 700 65.6 1.8 X 109 1% 1.3 X 10 10 Kerogen Drainage Source·Rock Residual 10 143 SR-21 Navarro Collins I·Green Lee 1741-1892 X X e. 400 1280.0 3.5 X 10 1% 1.4 X 1011 0.378 0.813 Quantity Area Thickness T.O.C. f. 400 587.2 1.6 X 10 10 1% 6.5 X 10 10 144 SR-21 Navarro Collins I-Green Lee 1741-1892 g. 500 182.5 5.1 X 1010 1% 2.5 X 1010 0.673 0.803 An average of 1% T.O.C. was used for all calculations. h. 600 41.6 1.2 X 109 1% 6.9 X 109 145 SR-21 Navarro Collins I-Green Lee 1741-1892 A conversion factor of 6 ftl = I barrel of oil was used for the i. 700 57.6 1.6 X 109 1% 1.1 X 1010 1.186 0.6739 final answer. j. 300 9632.0 2.7 X 1011 1% 8.0 X 10" SR·11 (lower) Average =0.76% k. 400 1856.0 5.2 X 1010 1% 2.1 X 1011 146 SR-22 Lamar Cooper Bros. I·Hays 1126·1217 I. 200 7088.0 2.0 X 10" 1% 4.0 X lOll 0.464 0.882 m. 100 8960.0 2.5 X lOll 1% 2.5 X 1011 147 SR·22 Lamar Cooper Bros. I-Hays 1126-1217 n. SO 4032.0 1.1 X 1011 1% 5.6 X 1010 0.972 0.845 o. SO 1056.0 2.9 X 1010 1% 1.4 X 1010 148 SR-22 Lamar Cooper Bros. I·Hays 1126-1217 p. SO 896.0 2.5 X 1010 1% 1.2 X 1010 1.238 0.822 12 SR-ll Average =0.85% Total 2.4 X 10 149 SR-23 Rains Humble I-Mainord 4140-4260 2.4 X 1012 ftJ + 6 ft l/barrel 4.0 X lOll barrels 0.440 1.179 = or 400 billion barrels ISO SR-23 Rains Humble I-Mainord 4140-4260 0.767 1.53 151 SR-23 Rains Humble I·Mainord 4140-4260 1.269 1.328 SR-13 (upper) Average =1.34% 152 SR-23 Rains Humble I-Mainord 4320-4440 0.396 1.421 153 SR-23 Rains Humble I-Mainord 4320-4440 0.890 1.361 154 SR-23 Rains Humble I-Mainord 4320-4440 1.325 1.117 SR·13 (lower) Average = 1.30% SR·13 Average =1.31% 155 SR-24 Titus Coats I·Scott Lizzie 3030-3090 0.430 0.9138

~. 56 BAYLOR GEOLOGICAL STUDIES EAGLE FORD GROUP. SOURCE-ROCK POTENTIAL 57

REFERENCES INDEX

alunite II Del Rio, Tex. 8 petroleum production 5, 31,35,37-43 BARKER, C. (1979) Organic geochemistry in petroleum exploration: and central Texas: Journal of Paleontology, v. 16, no. 2, p. Angelina-Caldwell flexure 6, 18, 19,20,21, downwarping 27,30 phosphate II American Association of Petroleum Geologists, Course Note 192-220. 28,30 Pittsburg syncline 7, 21, 29, 30 Series, no. 10, 159p. OLIVER, W.B. (1971) Depositional systems in the Arcadia Park Eagle Ford BISHOP, R.S.; GEHMAN, H.M., JR.; and YOUNG, A. (1984) Concepts (upper Cretaceous), northeast Texas: Texas Bureau of deposition 29, 30 reservoirs 5, 6, 31, 37 Rock Pens Member, see Boquillas fm. for estimating hydrocarbon accumulation and dispersal, in Economic Geology Report of Investigation 73, 28p. exploration fairway 40, 42, 43 , Tex. 9 Petroleum geochemistry and basin evaluation (G. Demaison PESSAGNO, E.A., JR. (1969) Upper Cretaceous stratigraphy of the fm. 5,9, 11,20-23,30 Eutaw fm. 7 Sabine uplift 6, 7, 9, 10, 18,20,21,22,23, and R.J. Murris, eds.) American Association of Petroleum western Gulf Coast area of Mexico, Texas, and Arkansas: Arkansas 7, 31 28,29,30 Geologists. Memoir 35, p. 41-52. Geological Society of America, Memoir III, 139p. Austin faulting 37 salt tectonism 37 BORNHAUSER, M. (1958) Gulf Coast tectonics: American Association POITER, P.E.; MAYNARD, H.B.; and PRYOR, W.A. (1980) Sedimen­ Chalk 6-9, 21, 26 "fishbeds" 21 San Carlos fm. 8 fossiliferous beds 9 of Petroleum Geologists Bulletin, v. 42, no. 2, p. 339-370. tology of shale: Springer-Verlag, New York, 303p. reservoirs 31, 37 sand 9, II, 17, 19,20,21,23,25,26,28,29, ,Tex. 8 31,37-43 BROWN, C.W. and PIERCE, R.L. (1962) Palynologic correlations in REESIDE, H.B., JR. (1957) Paleoecology of the Cretaceous seas of the glauconite II sandstone 5, 7, 8,9, 11,20,21,27 Cretaceous Eagle Ford Group, northeast Texas: American Western Interior: Geological Society of America, Memoir 67, Bells Sandstone Member, see Sub-Clarksville grainstones 20 serpentized rocks 8 Association of Petroleum Geologists Bulletin, v. 46, p. 2133- ch. 18, p. 505-54\. fm. Gulf Coast basin 7, 8, 20, 21, 27,29,30 shale 5, 7, 8,9, 11,20,21,26,28,29,31, 2147. Ross, C.S.; MISER, H.D.; and STEPHENSON, L.W. (1929) Waterlaid Belton 37 BURKEIT, J.M. (1965) Urban geology of greater Waco part I: Geology: volcanic rocks of early upper Cretaceous age in southwestern high 9, 10,28,30 Hill Co. II Sherman, Tex. 9 Baylor Geological Studies Bulletin, No.8, 45p. Arkansas, southeastern Oklahoma, and northeastern Texas: ,Tex. 20 siderite II CHAMNESS, R.S. (1963) Stratigraphy of the Eagle Ford Group in U.S. Geological Survey Professional Paper 154-F, p. 175-202. Benton Shale 8, 9 Indianola Group 8, 9 siltstone 8, II, 20 McLennan County, Texas: Unpublished master's thesis, Baylor SCOTT, G. (1926) On a new correlation of the Texas Cretaceous: bentonite 7, 8, II, 20, 29 source-rock potential 5, 6, 31, 37 University. American Journal of Science, ser. 5, v. 12, no. 68, p. 157- bird foot delta II, 19,20 Johnson Co. II South Bosque fm. 5, 20 CHARVAT, W.A. (1985) The nature and origin of Eagle Ford rocks, 161. Bluebonnet Member, see Lake Waco fm. Southwest Texas 7, 8 central Texas: Unpublished master's thesis, Baylor University. SELLARDS, E.H.; ADKINS, W.S.; and PLUMMER, EB. (1932) The geology Boquillas fm. 8 kaolinite 20 Sub-Clarksville COON, L.A. (1956) Tertiary-Cretaceous growth ofthe East Texas basin: of Texas, I: stratigraphy: The University of Texas Bulletin No. , Langtry Member 8 kaolinitic clays II , Bells Sandstone Member 9,21,26,31 Transactions of the Gulf Coast Association of Geological 3232, p. 422-439. , Rock Pens Member 8 deposition 30, 31 Societies, v. 6, p. 85-90. SHULER, E.W. (1918) The geology of Dallas County: The University Bouldin Member, see Lake Waco fm. Lake Crockett fm. 21 exploration fairway 41, 42,43 GEOMAP COMPANY (1979) Executive reference map No. 302, East of Texas Bulletin No. 1818, 54p. Britton Lake Waco fm. 5, II fm. 5,9,21,24,25,26,31,37 , Bluebonnet Member II Texas: Geomap Company, Dallas, I Plate. SIEMERS, C. T. (1978) Submarine-fan deposition of the Woodbine-Eagle deposition 28, 29 , Maribel Shale Member 9,21,26,31 exploration fairway, 39, 42, 43 , Bouldin Member II GORDON, C. H. (191 I) Geology and underground waters of northeastern Ford interval (upper Cretaceous), Tyler Co., Texas: Transac­ fm. 5,9, II, 18-20" 27-30 , Cloice Member II Tarrant Texas: U.S. Geological Survey Water Supply Paper 276, 78p. tions of the Gulf Coast Association of Geological Societies, Buda Langtry Member, see Boquillas fm. deposition 27, 28 GRANATA, W.H. (1963) Cretaceous stratigraphy and structural v. 28, p. 483-533. limestone 6, 8, 9, 20 limetsone 7, 8,9, 11,20,21,28,29,31 exploration fairway 37, 38,42,43 development of the Sabine uplift area, Texas and Louisiana: SILVER, B.A. (1963) The Bluebonnet Member, Lake Waco Formation reservoirs 5, 6, 31, 37 Llano area 8 fm. 5,9, II, 16, 17,20,30,37 Report on selected north Louisiana and south Arkansas oil (upper Cretaceous), central Texas-a lagoonal deposit: Baylor Louisiana 7, 31 tectonic uplift 21, 26 and gas fields and regional geology, Shreveport Geological Geological Studies Bulletin, No.4, 46p. calcite 20 terrigenous clastics 5, 7 Society Reference Report, v. 5, p. 50-96. STEHI, F.G.; CREATH, W.B.; UPSHAW, C.F.; and FORGOTSON, J.W., carbonates 5,7,9, 11,20,21,29 Mancos Shale 8, 9 Turonian age 6, 8,9,20,21 HABIB, D. (1982) Sedimentary supply origin ofCretaceous black shales, JR. (1972) Depositional history of Gulfian Cretaceous of East Cenomanian age 6, 8, 27 Maribel Shale Member, see Sub-Clarksville Tuscaloosa fm. 7 in Nature and origin of Cretaceous black carbon-rich facies Texas embayment: American Association of Petroleum Chispa Summit fm. 8 fm. (S.O. Schlanger and M.B. Cita, eds.): Academic Press, New Geologists Bulletin, v. 56, no. I, p. 38-67. clay 9 marl 8 Utah 8 York, p. 113-127. STEPHENSON, L. W. (1927) Notes on the stratigraphy of the upper Cloice Member, see Lake Waco fm. marlstone 8 HALBOUTY, M.T. and HALBOUTY, J.J. (1982) Relationships between Cretaceous formations of Texas and Arkansas: American Colorado 8 Mexico 7, 8 volcanic centers 7 East Texas field region and Sabine uplift: American Association Association of Petroleum Geologists Bulletin, v. II, p. 1-17. Colorado Shale 8, 9 Montana 8 volcanism 29 of Petroleum Geologists Bulletin, v. 66, no. 8, p. 1042-1054. ----(1928) Correlation of the upper Cretaceous or Gulf Series Coniacian age 9 montmorillonite 20 HAZZARD, R.T. (1939) The centerpoint volcanics of southwestern of the Coastal Plain: American Journal of Science, ser. 5, v. Cretaceous montmorillonitic clays, 5, II Waco, Tex. 5,9,20 Arkansas, a facies of the Eagle Ford of northeast Texas: 16, no. 96, p. 485-496. age 5 mudstone 5, 8, 11,20,21,27 West Texas 7, 8 Shreveport Geological Society Guidebook, 14th Annual Field ----(1929) Unconformities in upper Cretaceous Series of Texas: deposition 5 Murfreesboro, Ark. 7 Western Interior 7, 8, 9 Woodbine Trip, p. 133-151. Gulfian Series 5, 6, 7 American Association of Petroleum Geologists Bulletin, v. 13, organic carbon 31-37 deposition 26, 28 KOGER, C. (1981) Depositional and diagenetic history of the Austin p. 1323-1334. Dallas Co. 5, 9 Ouachita Mountains 28 erosional period 27 Clalk, central Texas, and its relationship to petroleum potential: ---- (1946) Alunite at Woodbine-Eagle Ford contact in Dallas, Tex. 8,9,20,21 reservoirs 5, 6, 31, 37 Unpublished master's thesis, Baylor University. northeastern Texas: American Association of Petroleum Davis Mountains 8 packstones 20 rocks 7, 9, 11,20,26,27,28,30 LONSDALE, H.T. (1927) Igneous rocks of the Balcones Fault region Geologists Bulletin, v. 30, no. 10, p. 1764-1771. of Texas: The University of Texas Bulletin No. 2744, 178p. STEPHENSON, L.W. and MONROE, W.H. (1938) Stratigraphy of upper McNULTY, C.L. (1964) Foraminifers from the Eagle Ford-Austin Cretaceous Series in Mississippi and Alabama: American contact, Northeast Texas: American Association of Petroleum Association of Petroleum Geologists Bulletin, v. 22, no. 12, Geologists Bulletin, v. 48, no. 4, p. 537-538. p. 1639-1657. ---- (1965) Lithology of the Eagle Ford-Austin contact in TAFF, J.A. (1891) The Cretaceous area north of the Colorado River: northeast Texas: Texas Journal of Science, v. 17, p. 46-53. Geological Survey of Texas, Third Annual Report, p. 269-379. ----(1966) Nomenclature of upper-most Eagle Ford formation THOMAS, J.A. (1980) The environmental significance of the thinly in northeastern Texas: American Association of Petroleum laminated deposits in the Cloice Member of the Lake Waco Geologists Bulletin, v. 50, p. 375-379. Formation, Eagle Ford Group, central Texas: Unpublished MISER, H.D. and Ross, C.S. (1925) Volcanic rocks in the upper bachelor's thesis, Baylor University. Cretaceous of southwestern Arkansas and southeastern WAPLES, D.W. (1983) Reappraisal of anoxia and organic richness with Oklahoma: American Journal of Science, ser. 5, v. 9, no. 50, emphasis on Cretaceous of north Atlantic: American p. 113-126. Association of Petroleum Geologists Bulletin, v. 67, no. 6, p. MOREMAN, W.L. (1942) Paleontology of the Eagle Ford Group north 963-978.

-416. BAYLOR GEOLOGICAL PUBLICATIONS·

Baylor Geological Studies 26. Davis, Keith W. (1974) Stratigraphy and depositional environ­ I. Holloway, Harold D. (1961) The Lower Cretaceous Trinity aqui­ ments of the , north-central Texas: Baylor fers, McLennan County, Texas: Baylor Geological Studies Bull. Geological Studies Bull. No. 26 (Spring). No. I (Fall). Out of print. 27. Baldwin, Ellwood E. (1974) Urban geology of the Interstate 2. Atlee, William A. (1962) The Lower Cretaceous Paluxy Sand in Highway 35 growth corridor between Belton and Hillsboro. central Texas: Baylor Geological Studies Bull. No.2 (Spring). Out Texas: Baylor Geological Studies Bull. No. 27 (Fall). $1.00 per of print. copy. 3. Henningsen, E. Robert (1962) Water diagenesis in Lower Cre­ 28. Allen. Peter M. (1975) Urban geology of the Interstate Highway taceous Trinity aquifers ofcentral Texas: Baylor Geological Stud­ 35 growth corridor from Hillsboro to Dallas County, Texas: ies Bull. No.3 (Fall). Out of print. Baylor Geological Studies Bull. No. 28 (Spring). $1.00 per copy. 4. Silver. Burr A. (1963) The Bluebonnet Member, Lake Waco 29. Belcher. Robert C. (1975) The geomorphic evolution of the Rio Formation (Upper Cretaceous), central Texas-A lagoonal de­ Grande: Baylor Geological Studies Bull. No. 29 (Fall). $1.00 posit: Baylor Geological Studies Bull. No.4 (Spring). Out of print. per copy. 5. Brown. Johnnie B. (1963) The role of geology in a unified conser­ 30. Flatt, Carl Dean (1976) Origina and significance of the vation program. Flat Top Ranch. Bosque County. Texas: Baylor banks in the Walnut Clay Formation, central Texas: Baylor Geo­ Geological Studies Bull. No.5 (Fall). Out of print. logical Studies Bull. No. 30 (Spring). Out of print. 6. Beall. Arthur 0 .. Jr. (1964) Stratigraphy of the Taylor Formation 31. Dolliver. Paul Noble (1976) The significance of Robert Thomas (U pper Cretaceous). east-central Texas: Baylor Geological Stud­ Hill's contribution to the knowledge of central Texas geology: ies Bull. NO.6 (Spring). Out of print. Baylor Geological Studies Bull. No. 31 (Fall). $1.00 per copy. 7. Spencer. Jean M. (1964) Geologic factors controlling mutation 32. Pool, James Roy (1977) Morphology and recharge potential of and evolution-A review: Baylor Geological Studies Bull. No.7 certain playa lakes of the Edwards Plateau of Texas: Baylor (Fall). Out of print. Geological Studies Bull. No. 32 (Spring). $1.00 per copy. 33. Bishop. Arthur L. (1977) Flood potential of the Bosque basin: Urban geology or Greater Waco. A series on urban geology in coopera­ Baylor Geological Studies BulL No. 33 (Fall). $1.00 per copy. tion with Cooper Foundation or Waco. 34. Hayward. Chris (1978) Structural evolution of the Waco region: 8. Pan I: Geology (1965) Geology and urban development by Peter Baylor Geological Studies Bull. No. 34 (Spring). $1.00 per copy. T. Flawn; Geology of Waco by J. M. Burket: Baylor Geological 35. Walker. Jimmy R. (1978) Geomorphic evolution of the Southern Studies Bull. No.8 (Spring). $1.00 per copy. High Plains: Baylor Geological Studies Bull. No. 35 (Fall). $1.00 9. Part II: Soils (1965) Soils and urban development of Waco by W. per copy. R. Elder: Baylor Geological Studies Bull. NO.9 (Fall). $1.00 36. Owen. Mark Thomas (1979) The Paluxy Sand in north-central per copy. Texas: Baylor Geological Studies Bull. No. 36 (Spring). $1.00 10. Part Ill: Water (1966) Surface waters of W!lco by Jean M. per copy. Spencer: Baylor Geological Studies Bull. No. 10 (Spring). $1.00 37. Bammel, Bobby H. (1979) Stratigraphy of the Simsboro Forma­ per copy. tion. east-central Texas: Baylor Geological Studies Bull. No. 37 II. Part III. Water (1976) Subsurface waters of Waco by Siegfried (Fall). Out of print. Rupp: Baylor Geological Studies Bull. No. II (Fall). $1.00 per 38. Leach. Edward Dale (1980) Probable maximum flood on the copy. Brazos River in the city of Waco: Baylor Geological Studies Bull. 12. Part IV: Engineering (1967) Geologic factors affecting construc­ No. 38 (Spring). $1.00 per copy. tion in Waco by R. G. Font and E. F. Williamson: Baylor Geolog­ 39. Ray. Bradley S. (1980) A study of the genus Camarocri­ ical Studies Bull. No. 12 (Spring), Out of print. nus in the Hunton Group of Pontotoc County. Oklahoma: Bay­ 13. Part V: Socio-Economic Geology (1967) Economic geology of lor Geological Studies Bull. No. 39 (Fall). $1.00 per copy. Waco and vicinity by W. T. Huang; Geology and community 40. Corwin, Linda Whigham (1982) Stratigraphy of the Fredericks­ socio-economics-A symposium coordinated by R. L. Bronaugh: burg Group north of the Colorado River, Texas: Baylor Geologi­ Baylor Geological Studies Bull. No. 13 (Fall). Not yet published. cal Studies Bulletin No. 40 (Spring). $1.00 per copy. 14. Part VI: Conclusions (1968) Urban geology of greater Waco­ 41. Gawloski, Ted (1983) Stratigraphy and environmental signifi­ Summary and recommendations by Editorial Staff: Baylor Geo­ cance of the continental rocks of Texas: Baylor Geologi­ logical Studies Bull. No. 14 (Spring). Not yet published. cal Studies Bulletin No. 41 (Spring). $1.00 per copy. 15. Boone. Peter A. (1968) Stratigraphy of the basal Trinity (Lower 42, Dolliver, Paul N. (1984) Cenozoic evolution of the Canadian Cretaceous) sands. central Texas; Baylor Geological Studies Bull. River basin: Baylor Geological Studies Bulletin No. 42 (Spring). No. 15 (Fall). $1.00 per copy. $1.00 per copy. 16. Proctor. Cleo V. (1969) The North Bosque watershed. Inventory 43. McKnight, Cleavy L. (1986) Descriptive Geomorphology of the of a drainage basin: Baylor Geological Studies Bull. No. 16 Guadalupe Mountains, South-Central New Mexico and West (Spring). Out of print. Texas: Baylor Geological Studies Bulletin No. 43 (Spring). $1.00 17. LeWand. Raymond L.. Jr. «(969) The geomorphic evolution of per copy. the Leon River system: Baylor Geological Studies Bull. No. 17 44. Matthews, Truitt F. (1986) The petroleum potential of"serpentine (Fall). Out of print. plugs" and associated rocks, central and south Texas: Baylor 18. Moore. Thomas H. (1970) Water geochemistry. Hog Creek basin, Geological Studies Bulletin No. 44 (Fall). $1.00 per copy. central Texas: Baylor Geological Studies Bull. No. 18 (Spring). Baylor Geological Society Out of print. IO 1-133, 138. Out of print. For titles see earlier Baylor Geological 19. Mosteller. Moice A. (1970) Subsurface stratigraphy of the Studies Bulletins. Comanchean Series in east central Texas: Baylor Geological Stud­ 134. The Black and Grand Prairies. A physiographic study of two ies Bull. No. 19 (Fall). Out of print. central Texas Prairies, 1974. Out of print. 20. Byrd. Clifford Leon (1971) Origin and history of the Uvalde 137. Structural geology of central Texas. A professional level Gravel of central Texas: Baylor Geological Studies Bull. No. 20 guidebook. Out of print. (Spring). Out of print. 139. Urban development along the White Rock Escarpment, Dallas, 21. Brown. Thomas E. (1971) Stratigraphy of the Washita Group in Texas (1978). $1.50 per copy. central Texas: Baylor Geological Studies Bull. No. 21 (Fall). Out 140. Paluxy Watershed. Geology of a river basin in north central of print. Texas (1979). $1.50 per copy. 22. Thomas. Ronny G. {I 972) The geomorphic evolution of the Pecos 141. Geomorphic evolution of the Grand Prairie, central Texas (1979). River system: Baylor Geological Studies Bull. No. 22. (Spring). $1.50 per copy. Out of print. 142. The nature of the Cretaceous-precretaceous contact, Central 23. Roberson. Dana Shumard (1972) The paleoecology, distribution Texas (1979). $4.00, a professional level guidebook. and significance of circular bioherms in the Ed wards Limestone of 143. The Geology of Urban Growth (1979). $UO per copy. central Texas: Baylor Geological Studies Bull. No. 23 (Fall). Out 144. A day in the Cretaceous (1980). $1.50 per copy. of print. 145. Landscape and Landuse (1980). $UO per copy. 24. Epps, Lawrence Ward (1973) The geologic history of the Brazos 146. Southeastern Llano Country (1983). $1.50 per copy. River: Baylor Geological Studies Bull. No. 24 (Spring). Out of print. 25. Bain. James S. (1973), The nature of the Cretaceous-pre­ • Publications available from Baylor Geological Studies or Baylor Geo­ Cretaceous contact in north-central Texas: Baylor Geological logical Society, Baylor University. Waco. Texas 76798. Studies Bull. No. 25 (Fall). Out of print. Texas residents add five cents per dollar for state tax. FALL 1987 ~ .Bulletin No. 45

Stratigraphy ofthe Eagle Ford Group ~ (Upper Cretaceous) and Its Source-Rock Potential in the East Texas Basin MILTON A. SURLES, JR.