Book T4T14 ''" DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, Director Water-Stjpply Paper 335 GEOLOGY AND UNDERGROUND WATERS OF THE SOUTHEASTERN PART OF THE TEXAS COASTAL PLAIN BY ALEXANDER DEUSSEN ■ CTpfe WASHINGTON i GOVERNMENT PRINTING OFFICE 1914 / DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, Director Water- Supply Paper 335 GEOLOGY AND UNDERGROUND WATERS OF THE SOUTHEASTERN PART OF THE TEXAS COASTAL PLAIN BY ALEXANDER DEUSSEN WASHINGTON GOVERNMENT PRINTING OFFICE 1914 i U d; af o. MN * s Mi CONTENTS. Introduction 13 Physiography 14 General character 14 Topographic features 16 Relief 16 Coast prairie 16 Kisatchie Wold 16 Nacogdoches Wold 16 Corsicana Cuesta and White Rock Escarpment 18 Bottom lands 18 Mounds and pimple plains 19 Drainage 19 Timber 21 General geologic features 21 Relation of geology to the occurrence of underground water 21 Principles of stratigraphy 22 Erosion and sedimentation 22 The geologic column 22 Subdivision of the geologic column. 23 Systems ./. 23 Formations : 23 Fossils 24 Nature and geologic distribution 24 Importance 24 Paleontologic units ; 25 Geology of the Coastal Plain 25 General features 25 Stratigraphy of the Coastal Plain in eastern Texas 26 Rock systems represented 26 Carboniferous rocks 26 Cretaceous rocks 26 Tertiary and Quaternary rocks 27 Tertiary system 29 Eocene series 29 Midway formation 29 Name and correlations 29 Occurrence and character 31 Relations to adjacent formations 31 Paleontology 32 Detailed sections 33 Brazos River section 33 Falls County 35 Limestone County 35 Kaufman County 36 Van Zandt County 36 4 CONTEXTS. Geology of the Coastal Plain — Continued. Stratigraphy of the Coastal Plain in eastern Texas — Continued. Tertiary system — Continued. Eocene series — Continued. Page. Wilcox formation 37 Name and correlation 37 Occurrence and character 39 Paleontology 40 Detailed sections 41 Brazos River section 41 North of the Brazos 44 Northeast Texas 44 Sabine River section 46 Claiborne group 51 Mount Selman formation 51 Name and correlation 51 Occurrence and character 52 Paleontology 52 Detailed sections 52 Brazos River section 52 Trinity River section 52 Cherokee County section 53 Harrison County section 54 Sabine River section 55 Cook Mountain formation 56 Name and correlation 56 Occurrence and character 56 Paleontology 56 Detailed sections 56 Brazos River section 56 Trinity River section 60 Cherokee County section 62 Sabine River section 64 Yegua formation 65 Name and correlation 65 Occurrence and character 66 Detailed sections 66 Brazos River section 66 Sabine River section 67 Jackson formation 67 Name and correlation .• 67 Occurrence and character 67 Paleontology 67 Detailed sections 68 Sabine River section _ 06 Oligocene series 68 Catahoula sandstone (including some Eocene) 68 Name and correlation 68 Occurrence and character 70 Detailed sections 70 Sabine River section 70 San Augustine County- 70 Tyler County 70 Polk County 71 Brazos County 71 CONTENTS. 5 Geology of the Coastal Plain — Continued. Stratigraphy of the Coastal Plain in Eastern Texas — Continued. Tertiary system — Continued. Page. Miocene series 72 Fleming clay 72 Name and correlation : 72 Occurrence and character 74 Detailed sections 74 Sabine River section 74 Neches River section 74 Grimes and Brazos counties 74 Dewitt formation (including some Pliocene) 74 Name and correlation 74 Occurrence and character 75 Paleontology 75 Detailed sections 75 East of Brazos River 75 West of Brazos River 75 Marine Miocene (probably including some early Pliocene) ... 76 General character 76 Details of occurrence 76 Pliocene series 77 Uvalde formation '. 77 Name and correlation 77 Occurrence and character 77 Quaternary system 78 Pleistocene series , 78 Lissie gravel 78 Name and correlation 78 Occurrence and character 78 Paleontology 80 Details of occurrence 80 Beaumont clay 80 Name 80 Occurrence and character 81 Paleontology 81 Pleistocene terrace deposits 81 Highest Pleistocene terrace 81 Middle Pleistocene terrace 82 Lowest Pleistocene terrace 83 Recent series 83 Structure 84 General features 84 Domes 84 Angelina-Caldwell flexure 85 Cooks Springs-Caddo fault and flexure 86 Minor flexures 86 Sabine uplift 86 Hydrology 87 Definitions 87 Occurrence of ground water 87 Source of ground water 87 Zone of saturation : 87 Movement of ground water 89 Perched ground-water tables 90 6 CONTENTS. Hydrology — Continued. Page. Artesian systems of the Texas Coastal Plain 90 General features 90 Nacatoch artesian system 90 Lower Eocene artesian system 91 General character 91 Quality of water 92 Yegua artesian system 92 General character 92 Quality of water 93 Catahoula artesian system 94 Dewitt artesian system 94 Coast Prairie artesian system 94 Minor sources of underground water 95 Marine Miocene beds 95 Beaumont clay 95 Salt water 95 Depth to reservoirs 96 Uses of ground water 96 Springs 97 Quality of water 97 Impurities in water 97 Living matter in water 98 Nonliving matter in water ; 98 Suspended matter 98 Dissolved matter 99 Concentration of dissolved matter 100 Water for domestic use 100 Water for drinking 100 Water for cooking 101 Water for washing 101 Classification of domestic waters 102 Water for stock 102 Water for boilers 102 Foaming 102 Corrosion 103 Scale forming 103 Classification of boiler waters 104 Water for irrigation 105 Alkali coefficients 105 Classification of irrigation waters 106 Therapeutic use of water 106 Chemical character in relation to geologic formations 107 General quality 107 Waters from the Lissie gravel 107 Waters from the Dewitt formation 108 Waters from the Catahoula sandstone 108 Waters from the Yegua formation 109 Waters from the Mount Selman formation 109 Waters from the Wilcox formation 109 Analyses 110 CONTENTS. 7 Page. County descriptions 110 Anderson County 110 Geology and hydrology 110 Nacatoch sand 110 Lower Eocene 110 Well data Ill Angelina County 114 Geology and hydrology 114 Lower Eocene 114 Yegua formation 114 Catahoula sandstone 115 Well data 115 Brazoria County 120 Geology and hydrology 120 Lissie gravel 120 Well data .. 121 Brazos County 132 Geology and hydrology 132 Lower Eocene 132 Yegua formation 132 Catahoula sandstone 133 Well data 133 Burleson County 136 Chambers County 138 Geology and hydrology 138 Well data '. 139 Cherokee County 146 Geology and hydrology 146 Well data 147 Falls County 148 Fort Bend County 149 Geology and hydrology 149 Well data 150 Freestone County 153 Geology and hydrology 153 Well data 153 Galveston County 154 Geology and hydrology 154 Well data 157 Gregg County 176 Geology and hydrology 176 Well data 177 Grimes County 180 Geology and hydrology 180 Lower Eocene 180 Yegua formation 180 Catahoula sandstone 180 Dewitt formation 181 Well data 181 Hardin County 186 Geology and hydrology 186 Miocene beds 186 Lissie gravel 187 WeU data 187 8 CONTENTS. County descriptions — Continued. p age . Harris County 220 Geology and hydrology 220 Dewitt formation 220 Lissie gravel , 220 Well data 221 Harrison County 240 Geology and hydrology 240 Well data 241 Henderson County 244 Geology and hydrology 244 Cretaceous rocks 245 Wilcox formation 245 Well data 245 Houston County 246 Geology and hydrology 246 Lower Eocene 246 Yegua formation 246 Well data 247 Jasper County 249 Geology and hydrology 249 Yegua formation 249 Catahoula sandstone 249 Marine Miocene 250 Lissie gravel 250 Well data 250 Jefferson County 259 Geology and hydrology : 259 Marine Miocene 259 Lissie gravel 259 Well data 261 Kaufman County 289 Geology and hydrology 289 Well data 289 Leon County 289 Geology and hydrology 289 Well data 290 Liberty County 290 Geology and hydrology 290 Marine Miocene 290 Lissie gravel 290 Well data 291 Limestone County 300 Geology and hydrology 300 Cretaceous rocks 300 Wilcox formation 301 Well data 301 Madison County 302 Geology and hydrology 302 Lower Eocene 302 Yegua formation 302 Well data 303 CONTENTS. 9 County descriptions — Continued. Page. Marion County 303 Geology and hydrology 303 Cretaceous rocks 303 Lower Eocene 303 Well data 304 Montgomery County 304 Geology and hydrology 304 Catahoula sandstone 304 Dewitt formation 305 Lissie gravel 305 Well data 305 Milam County , 308 Nacogdoches County 309 Geology and hydrology 309 Lower Eocene 309 Yegua formation 309 Well data ....' 309 Navarro County 318 Geology and hydrology 318 Well data 318 Newton County 318 Geology and hydrology 318 Yegua formation 319 Catahoula sandstone 319 Marine Miocene 319 Lissie gravel 319 Well data 319 Orange County 320 Geology and hydrology 320 Well data 320 Panola County 322 Geology and hydrology 322 Well data 322 Polk County 323 Geology and hydrology 323 Yegua formation 323 Catahoula sandstone 323 Dewitt formation 323 Lissie gravel 323 Well data 324 Robertson County 325 Geology and hydrology 325 Cretaceous rocks 325 Lower Eocene 325 Well data 326 Rusk County 331 Geology and hydrology 331 Well data 331 Sabine County 332 Geology and hydrology 332 Lower Eocene 332 Yegua formation 332 Catahoula sandstone 332 Well data 332 10 CONTENTS. County descriptions — Continued. Page. San Augustine County 336 Geology and hydrology 336 Wilcox formation 336 Yegua formation 336 Catahoula sandstone 337 Well data 337 San Jacinto County 339 Geology and hydrology 339 Catahoula sandstone 339 Dewitt formation 339 Lissie gravel 339 Well data 340 Shelby County 340 Geology and hydrology 340 Well data 341 Smith County 342 Geology and hydrology 342 Well data 342 Trinity County 343 Geology and hydrology 343 Yegua formation 343 Catahoula sandstone 343 Well data 344 Tyler County 347 Geology and hydrology 347 Yegua formation 347 Catahoula sandstone 348 Dewitt formation 348 Lissie gravel 348 Well data 348 Upshur County 350 Van Zandt County 351 Geology and hydrology 351 Well data 351 W T aller County 353 Geology and hydrology 353 Catahoula sandstone 353 Dewitt formation 354 Lissie gravel 354 Well data 354 Walker County 355 Geology and hydrology 355 Yegua formation 356 Catahoula sandstone 356 Dewitt formation 356 Lissie gravel 356 Well data 356 Wood County 357 Geology and hydrology 357 Well data 358 Index 361 ILLUSTRATIONS. Page. Plate I. A preliminary geological map and section of Texas east of the ninety- seventh meridian In pocket. II. Natural mounds 18 III. Characteristic fossils of the Midway formation 32 IV. Columnar sections of the Tertiary In pocket. V. Characteristic fossils of Claiborne age 56 VI. Characteristic fossils of the Jackson formation 66 VII. Preliminary map of the Nacatoch, Yegua, and Lissie artesian reser- voirs (Coast Prairie system) in southeast Texas In pocket. VIII. Preliminary map of the lower Eocene and the Catahoula artesian res- ervoirs in southeast Texas In pocket. IX. Preliminary map of the Dewitt and the marine Miocene artesian reser- voirs in east Texas In pocket. Figure 1. Map of eastern United States, showing area treated in this report and its relations to the Atlantic and Gulf Coastal Plain of the United States 14 2. Physiographic regions of Texas 15 3. Map showing the influence of the Kisatchie Bajada on the courses of the streams of Texas 17 4. Chronology of the development of drainage in east Texas 20 5. Map showing the distribution of timber on the eastern third of the Texas Coastal Plain 21 6. Principal structural features of the Texas Coastal Plain 85 7. Map showing mean annual rainfall and run-off in the State of Texas 88 8. Diagram illustrating the position of the main ground-water table in a region of undulating topography 89 9. Diagram showing common arrangement of factors producing flow- ing wells 89 10. An artesian basin 90 11. Diagram showing water conditions in the outcrop of the "Wilcox formation in Texas 91 12. Diagram showing the relation of a perched water table to the main water table 92 13. Diagram showing the artesian systems of the Texas Coastal Plain. 93 14. Section between Galveston and Houston, showing the water- bearing beds of the several flowing wells and the relations of salt and fresh water 155 15. Diagram showing effect of scattered lenticular clay masses in producing apparent water horizons with dips opposite to the true dip of the beds 156 16. Section showing the water-bearing sands in the Spindletop wells. 260 17. Wells in the vicinity of Rockland 347 11 INSERT. Page. Analyses of underground waters from eastern Texas ' 110 12 GEOLOGY AND UNDERGROUND WATERS OF THE SOUTHEASTERN PART OF THE TEXAS COASTAL PLAIN. By Alexander Deussen. INTRODUCTION. This contribution to the geology of the ground waters of east and northeast Texas is based on field work done by the writer during the summers of 1907 and 1908. The area described includes the part of the Coastal Plain of Texas occupied by the outcrop of Cenozoic rocks lying east of Brazos River and south of a line extending east and west through Jefferson, in Marion County. (See Hg. 1, p. 14, and geologic map, PL I, in pocket.) It embraces 36,317 square miles, an area as great as that of the State of Indiana. The report describes the under- ground water horizons of the region and discusses the artesian condi- tions and prospects in the several counties. Acknowledgments for valuable assistance rendered and for infor- mation furnished are due to Joe Lake, of Marshall; June Harris, of Nacogdoches; J. P. Mettauer, of Rockland; A. P. Kimmey, of Lufkin; E. T. Dumble, William Kennedy, and L. Garrett, of the Southern Pacific geologic corps; T. U. Taylor, dean of the engineering depart- ment, University of Texas; F. W. Simonds, professor of geology, Uni- versity of Texas; A. T. Dickey, city engineer of Galveston; F. B. Brown, of Longview; C. F. W. Felt, chief engineer of the Gulf, Col- orado & Santa Fe Railway; Patillo Higgins, of the Higgins Oil & Fuel Co.; F. W. Michaux, of Beaumont; Capt. F. I. Kellie, secretary of the Commercial Club of Beaumont; P. A. McCarthy, city engineer of Lufkin; and many others. Information has likewise been freely drawn from the following publications : Professional Paper 46, United States Geological Survey, Geology and underground water resources of northern Louisiana and southern Arkansas, by A. C. Veatch; An- nual reports of the Geological Survey of Texas, 1889-1892; Water- Supply Paper 190, United States Geological Survey, Underground waters of the Coastal Plain of Texas, by T. U. Taylor; Bulletin 212, United States Geological Survey, Oil fields of the Texas-Louisiana Gulf Coastal Plain, by C. W. Hayes and William Kennedy; Bulletin 282, United States Geological Survey, Oil fields of the Texas-Louisi- ana Gulf Coastal Plain, by N. M. Fenneman; and others. Detailed 13 14 GEOLOGY AND UNDERGROUND WATERS OF references are given in footnotes. The information relating to quality of water has been reviewed by R. B. Dole, who also recomputed the analyses of water into ionic form in parts per million. This report was prepared under the direction of T. Wayland Vaughan, to whom thanks are due for many suggestions. ■400 500 Miles Atlantic and Gulf coastal plains Area covered by report Fioube 1.— Map of eastern United States, showing area treated in this report (indicated by horizontal lines), and its relations to the Atlantic and Gulf Coas"tal Plain (indicated by stippling). PHYSIOGRAPHY. GENERAL CHARACTER. The Gulf of Mexico from Florida to Yucatan is fringed by a broad sublevel region that slopes gently toward the Gulf from an interior highland region. This natural physiographic province of North SOUTHEASTERN TEXAS COASTAL PLAIN. 15 America, which is known as the Gulf Coastal Plain and is the western continuation of a similar plain bordering the Atlantic, comprises all of Florida and Louisiana and portions of Georgia, Alabama, Missis- sippi, Kentucky, Arkansas, Texas, and Mexico, and a long reentrant from it extends northward up Mississippi River as far as southern Illinois. In the United States it is very broad, extending in places 500 miles back from the Gulf, but in Mexico it reaches mountains at a much shorter distance. Everywhere it is characterized by low relief and broad river valleys. Near the coast it is generally level, but in the interior it has been broadly but gently dissected and pre- sents a hilly, undulating aspect. In Texas it comprises the fol- lowing features, named from the coast inland: (1) The coast prairie; Figure 2. — Physiographic regions of Texas. (2) the Kisatchie Wold; 1 (3) the red lands, and (4) the Yegua timber belt, the two constituting the Nacogdoches Wold; (5) the Corsicana Cuesta (including the Wilcox plain and the eastern marginal prairies) ; (6) the Black Prairie; (7) the Grand Prairie; (8) the central basin region; (9) the high plains and plateaus; and (10) the Cor- dilleran region. (See fig. 2.) The area considered in this report comprises a small part of the Gulf Coastal Plain, stretching from the coast inland to and including the Wilcox plain and a part of the eastern marginal prairies. 1 In this paper the term "wold" is used to designate a range of hills produced by differential erosion from inclined sedimentary rocks. A wold is made up of a cuesta or gently sloping dip plain on one side and a bajada or abruptly sloping face on the other. These terms were first so used by Veatch, A. C, Prof. Paper U. S. Geol. Survey No. 44, 1906, p. 29. 16 GEOLOGY .L\D UNDEBGBOUND WATERS OF TOPOGRAPHIC FEATTJPvES. KELIEF. Coast prairie. — Immediately fringing the Gulf is a narrow strip of level plain (see fig. 2), called the coast prairie, winch has been slightly elevated above the sea in comparatively recent geologic time. It reaches inland about 50 miles. Near the Gulf its surface is flat and low, having an altitude of 20 to 30 feet above tide. Numerous rivers and creeks have excavated steep-sided channels across it. The di- vides between the drainways are grass covered, but the stream courses are bordered by narrow strips of timber. On its western margin this prairie merges into a rolling timber area. KisatcMe Wold. — The coast prairies are succeeded on the interior by the Kisatchie Wold, comprising a gentle dip plain ( the Kisatchie Cuesta) to the south, and a range of low hills (the Kisatchie Bajada) to the north. The Kisatchie Cuesta occupies the counties of Newton, Jasper, Tyler, Hardin, Polk, Liberty, San Jacinto, Walker, Montgomery, and Waller, and parts of Grimes, Fort Bend, Harris, Jefferson, and Orange. The topography is generally undulating, the soils are for the most part sandy, and the uplands are forested in contrast to the prairie areas on the coast. (See fig. 2.) The Kisatchie Cuesta terminates in the interior in the low hills of the Kisatchie Bajada. These hills, which represent the dis- sected portion of an interior-facing escarpment, which resulted from the greater hardness of the cap rock as compared with the underlying strata (figs. 2 and 3) are traceable across the entire extent of Texas from Sabine River to the Rio Grande. In places they attain a height of 150 feet above sea level. They are typically developed at Rockland in Tyler County, at Trinity in Trinity County, and near Fairmount in Sabine County. This range of hills exerts an important influence on the streams of the Coastal Plain, all the rivers that cross it being noticeably deflected and caused to flow along its foot for greater or less dis- tances. (See fig. 3.) Nacogdoches Wold. — A second well-defined wold succeeds the Kisatchie Wold on the north and west. (See fig. 2.) On the divides and in areas near the Kisatchie Wold the country is for the most part rolling, but toward the interior margin it becomes hilly. This wold owes its existence to the superior hardness of the cap rock, which here consists of iron ore. On the interior margin the plain has been very much eroded and is now preserved only in a great number of iron-ore capped hills which rise to considerable altitudes above the surrounding lowlands. These hills constitute by far the greatest elevations in the region, the highest, such as those in Cherokee SOUTHEASTERN TEXAS COASTAL PLAIN. 17 c3 .22 M 3 a 9 ♦a 5sfi o M ft C3 8 14926°— wsp 335—14- 18 GEOLOGY AND UNDERGROUND WATERS OF County, attaining an altitude of 666 feet above sea level. 1 As a type of these hills (locally called mountains) may be mentioned Gent Mountain in western Cherokee County, Grays Mountain, Grimes Mountain, Ragsdale Mountain, and many others. The fringed and greatly dissected margin of the Nacogdoches Wold, represented by these iron-ore capped hills, which overlook the lowlands to the north and west, constitutes the Nacogdoches Bajada, whose approximate direction is indicated on the map (fig. 2). Corsicana Cuesta and White Bock Escarpment. — The Nacogdoches Wold is succeeded in the interior by the Corsicana Cuesta. It includes the Black Prairie of Hill 2 and terminates in an inward- facing escarpment known as the White Rock Escarpment. 3 The cuesta is subdivisible into a number of geographic units, including the Wilcox timber belt (called by Dumble 4 the lignitic plain), the eastern marginal prairies, the Taylor prairies, and the White Rock Prairie. 5 The Wilcox timber belt, which immediately borders the Nacog- doches Wold, is underlain by the Wilcox formation (p. 37). Its soils are predominatingly sandy, and it is entirely forested, in decided contrast to the subdivisions of the cuesta that lie farther west. The eastern marginal prairies succeed the Wilcox timber belt on the west. Their soil is clayey and approaches the " black waxy" type. The area is grass covered, in contrast to the timbered country on the east. The Wilcox timber belt and a portion of the eastern marginal prairies are the only parts of the Corsicana Cuesta that lie within the area described in this report. Bottom lands. — The large through-flowing streams, such as the Brazos and the Trinity, and many of the smaller streams, such as the Sabine, Neches, Attoyac, and Cypress, have carved out wide valleys, and in these valleys have built up extensive alluvial plains 1 to 10 miles in width, which occupy in the aggregate a much larger area than the remnants of the ancient plains from which they were carved. These alluvial or constructional 6 plains, through which the streams meander in irregular courses, are locally called bottom lands. For the most part they are sublevel and lie 100 to 200 feet beneath the i Hill, R. T. Second Ann. Rept. Gcol. Survey Texas, 1890, p. 19. 2 Hill, R. T., Geography and geology of the Black and Grand prairies, Texas, etc.: Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 7, 1901, p. 65. a Idem, p. G8. * Dumble, E. T., A comprehensive history of Texas, Dallas, 1898, vol. 2, p. 477. & Hill, R. T., op. cit., pp. 67-G8. • Constructional plains are plains formed by the deposition of sediment in sublevel sheets along the stream ways or at the margin of the ocean. They may therefore be of fluviatile or marine origin. Destructional plains are sublevel areas formed as a result not of deposition but of erosion or degradation of older and higher surfaces. . r :e:_: j :-_ ;. : . = ■ WATER-SU==LY PAPER 335 PLATE II A. ON FLAT FORK CREEK : 3 MILES FROM TENEHA, TEX. Showing tree-covered top of rround and barren surrounding country. Substructure: Wilcox (Eocene). (After Veatch ) B. ON FLAT FORK CREEK, 3 MILES FROM TENEHA, TEX. Symmetrical form partly destroyed by stream erosion. Substructure: Wilcox (Eocene). (After Veatch.) C. ON PINE FLATS, NEAR TARBINGTON, TEX. Substructure: Quaternary. Photograph by Vernon Bailey. (After Veatch.) NATURAL MOUNDS. SOUTHEASTERN TEXAS COASTAL PLAIN. 19 general level of the rolling and hilly areas of the adjacent rem- nantal plains. They are covered with hardwood timber instead of with the pine of the upland plains. These bottom lands are exceed- ingly fertile and are justly prized for farming purposes. Their chief drawback is their liability to overflow where unprotected by levees. The Brazos bottom, for instance, is one of the most fertile farming regions in the world. Owing to the lowness of their altitudes as compared with the sur- rounding country, many of these bottoms present ideal conditions for artesian wells (see pp. 87-90), and the artesian reservoirs which lie beneath them have been of inestimable economic importance in their industrial and agricultural development. Mounds and pimple plains. — Besides the physiographic and topo- graphic features previously enumerated, all of which were produced by water, the region contains certain elevations or physiographic features, the so-called mounds and pimple plains, which are of differ- ent origin. The mounds are pronounced elevations, a few hundred acres in extent. Some of them rise 40 to 50 feet above the general level of the adjacent plains. They are -irregularly distributed but are more con- spicuous on the coast prairies. Big Hill and Spindle top hi Jefferson County, High Island in Galveston County, Barbers Hill and Kiser Mound in Fort Bend County are typical. The pimple plains, which are irregularly but widely distributed over both the remnantal and the constructional plains, are charac- terized by numerous conspicuous small rounded circular elevations 15 to 30 feet in diameter and 2 to 6 feet in height. They are typi- cally developed in the Flat Fork Bottom south of Tenaha in Shelby County. (See PI. II.) DRAINAGE. Two major types of streams prevail in the area — the antecedent and the consequent. The antecedent streams antedate the formation of the Tertiary plain, having been in existence on the Cretaceous plain when the shore line of the gulf was far north of its present position. When the Tertiary area was added to the existing land, these streams extended their courses across the newer plain, growing at their mouths. The Brazos and the Trinity are of this type and constitute the largest and most important streams in the region. The consequent streams developed after the formation of the Ter- tiary plain and occupied the territory between the extended or ante- cedent drainage. These have grown at their heads, having gradu- ally worked their way backward. The Sabine, Angelina, Neches, and San Jacinto rivers are of this type. 20 GEOLOGY AND UNDERGROUND WATERS OF Of these consequent streams, four distinct systems of drainage are recognizable: (1) System developed on Eocene and Oligocene areas during Miocene time; (2) system developed during the earlier Pleisto- cene time; (3) systems developed during later Pleistocene time; (4) system developed during recent time. (See fig. 4.) LEGEND Drainage system developed during Recent time Drainage system developed during late Quaternary time and its subsequent extension across the coast prairies during Recent time Drainage system developed during early Quaternary time and its subsequent extension during late Quaternary time Drainage system developed during Miocene time and its subsequent extension across early Quaternary areas during later Quaternary time Drainage system developed on Eocene areas during Oligocene time and its subsequent extension across post-Eocene areas after their elevation Drainage system developed on the Cretaceous prairies during post-Cretaceous time and its subsequent extension across the Tertiary plain after elevation Figube 4.— Chronology of the development of drainage in east Texas. The older consequent systems occupy the relatively higher surfaces between the extended streams. The longest and oldest rise along the interior margin of the Wilcox timber belt and are antecedent relative to the coast prairie, antedating its formation. This system includes Sabine River. The youngest system begins at the interior margin of SOUTHEASTEKN TEXAS COASTAL PLAIN. 21 L/S^l A-£ .-Ar'' the coast prairie, upon which it is established, and is consequent to it. It includes a number of creeks and bayous which head close to the coast and are sluggish and brackish. TIMBER. The region comprises both prairie and forest areas. The Kisatchie Wold, Nacogdoches Wold, and Wilcox timber belt constitute a timbered region wedged between the coast prairie on the south and the eastern marginal prairie on the west. This portion of Texas, which is very often spoken of as the east Texas timber belt, repre- sents the western extension of the Atlantic timber belt. Its soils are predominatingly sandy com- pared with those of the prairies on the south and west. The general character of the timber is indicated on the map (fig. 5). On the bottoms or alluvial plains hardwood for- ests flourish, made up of cow oak, bur oak, overcup oak, com- mon white oak, red oak, Texas oak, willow oak, water oak, white ash, green ash, sweet pecan, bitter pecan, shagbark, white hickory, sweet gum, black gum, tupelo, cottonwood, syc- amore, elm, and other trees. On the uplands and divides pine forests predominate, con- sisting of short leaf, loblolly, and long leaf (fig. 5), inter- spersed toward the interior with upland oaks, black jack, blue jack, and other trees. LEGEND Alluvial bottom. Hardwoods V? Long-leaf pine m Loblolly pine Short-leaf pine Post oak Live oak Figure 5.— Map showing the distribution of tim- ber on the eastern third of the Texas Coastal Plain. After Bray. Note the close relation of the timber to the outcrops of the different geo- logic divisions. GENERAL GEOLOGIC FEATURES. RELATION OF GEOLOGY TO THE OCCURRENCE OF UNDERGROUND WATER. The problems of underground and artesian water are problems in stratigraphy, the occurrence of such water being determined by the arrangement and relative positions of porous and nonporous (or impervious) beds. To ascertain whether flowing wells can be had 22 GEOLOGY AND UNDERGROUND WATERS OF at a given place before a hole is actually drilled, it is necessary to know what the arrangement, nature, and distribution of the rock sheets is in that region. To know whether a sufficient quantity of water can be economically secured from a well at a given place for a particular purpose, the same information is necessary. To know whether the water that may be obtained is of a quality suitable for the desired purpose, it is again necessary to know the same facts. These facts are the concern of the branch of geology known as stratigraphic and structural geology, and to ascertain them for any particular area it is necessary to know something concerning the stratigraphic and structural geology of the area. PRINCIPLES OF STRATIGRAPHY. EROSION AND SEDIMENTATION. The most obvious natural processes now in operation on the earth are those of erosion and sedimentation. The exposed rocks disinte- grate and decay into soils and rock detritus. Rains wash the soils and rock detritus into the streams, and the streams eventually carry the materials to the sea and deposit them on the sea floor. The removal of the soil and detritus by rain and wind constitutes erosion. The deposition of material on the sea floor constitutes sedimentation. If these processes continued indefinitely, and no new land appeared, the land would in time be obliterated, the ocean would become universal, and subaerial erosion would cease. But so long as the present forces remain in operation this result can never be obtained. As the continents are worn down in one place, they are elevated in another, and new land is constantly being formed. Some continents are rising; others are sinking. Evidence shows that some seashores are rising while others are subsiding, some slowly (2 or 3 inches in a century), and others rapidly. THE GEOLOGIC COLUMN. Throughout the earth's history vast quantities of the products of rock decay and material taken from the sea water by organisms have accumulated on the sea floor, in some localities to a thickness of more than 20,000 feet. From time to time one area or another has been elevated into land, causing sedimentation to cease and ero- sion to begin. Fresh submergence may have again followed and sedimentation been resumed. In any given region periods of erosion may have alternated with periods of sedimentation. The products of sedimentation are the sedimentary rocks, also called stratified, because arranged in layers or strata. They vary in character with the conditions of their deposition, gravels and sands usually being deposited close to shore, muds and clays in deeper water, and calcareous oozes, which ultimately form limestone, are deposited in areas to which earthy detritus derived from the land is not carried. SOUTHEASTERN TEXAS COASTAL PLAIN. 23 If the sea floor sinks, the place where sand was formerly deposited may be covered by clay, and if further depressed, by lime deposits. In time the sand, clay, and limy ooze will become indurated or lithified into sandstone, shale, and limestone through the action of pressure and cementing substances deposited by circulating water. Then, if the region is subsequently elevated into land and the materials are exposed (in a canyon, for instance) they will present, in columnar form, a typical stratified or sedimentary series, consisting of a bed of sandstone at the base, shale in the middle, and limestone at the top. It is obvious that in any such stratified series the beds of greatest age are lowermost and those of least age uppermost. If a place could be observed where sedimentation had been continuous since the begin- ning of the process each period of the earth's history would be seen to be represented by certain divisions of the rocks. No such complete sedimentary series has ever been found in any one place, but portions of it are found at different localities, and by visiting a sufficient number of places the geologist may inspect the whole. SUBDIVISIONS OF THE GEOLOGIC COLUMN. Systems. — Certain names have been given to the different portions of this sedimentary series, and these different portions (called systems), taken in order, represent the accumulations during corresponding periods of the earth's history. The names of these systems in order from top to bottom, or from the youngest to the oldest, are: Quater- nary, Tertiary, Cretaceous, Jurassic, Triassic, Carboniferous, Devo- nian, Silurian, Ordovician, Cambrian, Algonkian, and Archean. The major units (systems) of the sedimentary series may be called time units, because the basis of their classification is time. The materials composing a given unit are not necessarily the same in different places, because the conditions of deposition (including depth of water) may have varied greatly; during a given period sands may have been deposited in one place and clays in another. Formations. — The major units are divisible into smaller units according to the character of their materials. The lower part of a particular system may consist of sandstone, the middle part of clay, and the upper part of limestone. Such smaller units are known as lithologic units (or formations), because the classification may be based on the lithology or character of the constituent materials. They are named after places where they are well exposed. Formations are essentially local. A given sandstone, for instance, may extend laterally for a considerable distance, but will eventually be succeeded or replaced by another kind of material, because sand is deposited only in shallow water. A sandstone formed from deposits along the stretches of a long coast on a sea floor of very steep slope will extend a long distance in one direction and a short distance in 24 GEOLOGY AND UNDERGROUND WATERS OF another, being cut off seaward by deep water in which clay was deposited in place of sand. As long as the sea floor is neither elevated nor depressed, a sand- stone formation deposited on it is of the same age throughout. With a sinking sea floor, however, the zone of deposition is con- stantly advancing with the advance of the shore line, and the forma- tion may attain a wide distribution. The depression may continue for a long time, and the sand deposited along the shore may retain its character and may be laterally continuous throughout and there- fore constitute one and the same formation; and yet one extremity of the formation represents deposition when the depression began and the other represents deposition when the depression ceased. A formation is, therefore, not necessarily of precisely the same age in different places of its occurrence. Geologic maps and geologic sections are designed to show the dis- tribution of geologic formations both at the surface and underground. FOSSILS. Nature and geologic distribution. — Along with the products of land decay and material chemically precipitated from oceanic water, the shells and skeletons of animals are deposited on the sea floor, where they are soon buried beneath sediment either as a whole or in broken pieces. Very many of the shells are subsequently removed, but perfect casts of the forms may remain. Such evidences of formerly existing life, now a part of the rock masses, are known as fossils. Wherever sedimentary rocks occur fossils may be found in greater or less abundance. Study shows that fossil forms are unlike those of species now living, the greatest deviation being found in fossils deposited during the earliest periods of the earth's history. The simpler animals (animals not highly organized) characterize the lower divisions of the series and the higher types the upper divisions. Between the two there is a progressive increase in complexity. Each division is characterized by a certain set of fossils, which in the aggregate is distinctive of that division and is different from that of any other division. These facts are of universal application. Fossils, for instance ; that characterize the Cambrian system in one region of the globe characterize it in all other regions. Subdivision of the larger systems, however, may show local and specific variation. For example, a middle formation of the Cretaceous system in England and a middle formation of the same system in Texas may be characterized by slightly different sets of fossils. Importance of fossils. — The fact that each division of the stratified series is characterized by a certain group of fossils is of the greatest importance to the practical working geologist, enabling him to SOUTHEASTERN TEXAS COASTAL PLAIN. 25 recognize the division in widely separated places. If he finds certain fossils in a limestone exposed at a given place at the surface and finds them also in a similar-appearing limestone at a depth of 2,000 feet in a well 20 miles away, he may be confident that the same rock sheet is present in both places, and that it has a decided slope (dip) which in the course of the 20 miles has carried it 2,000 feet beneath the surface. If coal underlies the limestone where the latter is exposed at the surface it is probable that it also underlies it in the well and can be found by boring a little deeper. Fossils are thus the earmarks of geologic formations and distinguish them as much as does the character of their rocks. In this paper, however, no attempt is made to describe the fossils of the re- spective formations, such matter being unessential in the present connection. Their occurrence, however, is noted and some charac- teristic forms are figured. Paleontologic units. — In a sedimentary series given kinds of rock may be repeated many times. A limestone of a certain lithologic character may appear at the base, another in the center, and still another at the top. If it were not for the fossils it might be difficult to tell whether any particular limestone is the one in the middle or at the top or the bottom. If, however, a given fossil is known to char- acterize one of the beds and not the others, identification by its aid is easy. A sedimentary series may thus be divided not only into time units and into lithologic units or formations, but also into pale- ontologic units or biologic zones, each characterized by the presence of a given fossil or a set of fossils. A paleontologic unit, like a time unit, is not characterized by any particular kind of rock. The shells of the same kind of animals may be accumulated in clay as well as in limestone. The clay and the lime- stone are parts of the same time unit and the same biologic zone but they belong to different lithologic units or formations. Again, certain animals may be living at a given time and may be accumulated in connection with a deposit of sand. If the sea floor is sinking, the same kind of sand may continue to be deposited (the zone of depo- sition constantly shifting), long after the race of animals has died out and has given place to other races. The sand is all a part of the same formation, but it is not a part of the same biologic zone nor of the same time unit. GEOLOGY OF THE COASTAL PLAIN. GENERAL FEATURES. The materials exposed on the Coastal Plain of Texas and encountered in the wells drilled in the region are members of a sedimentary series, the deposition of which was at times interrupted by land epochs and periods of erosion, during which sedimentation ceased. Such times 26 GEOLOGY AND UNDERGROUND WATERS OF of erosion are indicated by gaps in the series, spoken of as uncon- formities. Originally the beds composing this series were nearly horizon- tal. Since their formation, however, the region has been gradually elevated and the entire series slightly tilted toward the Gulf. Since their elevation, these beds have been subjected to erosion, those having the highest altitude and the longest period of exposure having suffered the most. The result is that the surface of the Coastal Plain no longer coincides with the surface of the uppermost rock layer, but bevels across the gently inclined layers at a small angle. Conse- quently, in passing from place to place different rock sheets or forma- tions are exposed to view, the lowermost formation being exposed at the greatest distance from the coast, and the uppermost forma- tion at the coast. Traveling from the coast toward the interior, the geologist may inspect the entire series just as he could by descending a shaft sunk to the bottom of the series at the coast. By determining the sequence in his cross-country travels, he can predict very accu- rately the sequence and the character of the materials that would be encountered in sinking such a shaft or well. STRATIGRAPHY OF THE COASTAL PLAIN IN EASTERN TEXAS. ROCK SYSTEMS REPRESENTED. In the stratigraphy of the Coastal Plain in eastern Texas the Car- boniferous, Cretaceous, Tertiary, and Quaternary systems are represented. These different systems comprise two structural divi- sions. The Carboniferous rocks, which make up one structural unit, constitute the basement upon which the Cretaceous and younger rocks have been deposited. The Cretaceous, Tertiary, and Quater- nary rocks, which make up the other structural unit, and which constitute the outcropping formations of the Coastal Plain, lie unconformably upon the Carboniferous rocks and have a general southeast dip of 1 to 200 feet to the mile. CARBONIEEROUS ROCKS. The Carboniferous rocks are not exposed and have been reached by no drill holes within the limits of the region described in this paper. Their presence beneath it is inferred from their exposure farther west where they have a dip to the northwest, and from their occurrence in drill holes in the nearer Cretaceous area. CRETACEOUS ROCKS. The Cretaceous rocks, consisting for the most part of chalk, lime- stone, and marls, underlie the entire Coastal Plain. Their water- bearing beds, however, are too deeply embedded beneath nearly all the counties with which this report deals to make them available as SOUTHEASTERN TEXAS COASTAL PLAIN. 27 sources of artesian supplies, and therefore they have little economic interest in the present connection. That these beds occur beneath the later rocks is proved by drill holes that have reached them and by the existence of certain inliers (isolated bodies of rock lying at a distance from the main body and surrounded on all sides by rocks of later age) within the area of the post-Cretaceous sediments. At least three Cretaceous inliers are known to occur in the area — the Steen Dome and Brooks Dome in Smith County, and the Anderson Dome in Anderson County. Where these domes occur, they introduce complications into the artesian conditions. TERTIARY AND QUATERNARY ROCKS. Resting on the Cretaceous rocks are the Tertiary and Quaternary sediments, which constitute the exposed rocks and supply the water to artesian and other deep wells. The sequence of the rocks is shown in the following table: Cenozoic deposits of the Texas Coastal Plain. Sys- tem. Series. Formation. Thick- ness. Lithology and characteristic fossils. Recent. Feet. 0-50 Fluviatile deposits, consisting of brown, red, or black sandy clay or silt of the low, overflow terraces of the streams; also present flood-plain materials, including sand and giavel bars. Recent buffalo bones, etc. Sea- ward, these fluviatile deposits grade into interstream de- posits consisting of yellow and blue clays and yellow wave-formed sand, sand and shell beaches, bars, and bar- riers, carrying Rangia cuneata and other fossils. >. Pleistocene. Beaumont clay. 800 max. Blue, calcareous clay, with nu- merous lime concretions about 1 inch through. Lenses of sand and sandy clay. The clays carry Rangia cuneata, etc.; embedded logs are com- mon. Farther inland the Lis- sie gravel and Beau- mont clay are repre- sented along the stream valleys by the lowest and the mid- dle of the three Pleis- tocene terraces. a u S3 3 Lissie gravel. —Unconformity- Highest Pleis- tocene ter- race (farther inland). —Unconformity- Thin to 900 Gravels and coarse sands, with some small lenses and pockets of red clay in places; limy clays, gravels, and limy con- glomerates or "adobe" in others. The fossils include Equus semiplicatus, Megal- onyx, etc. 0-50 Fluviatile deposits consisting of gravels of granitic origin in and adjacent to certain drainage areas; flints, lime- stone de'bris, and limy conglomerates in others; ferru- ginous sands and silts, with fragments of iron ore, in still others. In the stream valleys these materials appear as terraceslying 200 to 225 feet above the level of the present stream channels, and grading laterally into an inter- stream or upland phase veneering the uplands with a sheet of gravel where the Yegua and Jackson formations constitute the country rock, but thinning and disap- pearing south of the Yequa-Catahoula or the Jackson- Catahoula boundary. No fossils. 28 GEOLOGY AND UNDERGROUND WATERS OF Cenozoic deposits of the Texas Coastal Plain — Continued. Sys- tem. ■=, Series. Pliocene. Miocene. Oligocene. Eocene. Formation. Uvalde forma- tion (late Pliocene). — Unconformity- Dewitt forma- tion. o Fleming clay, b ~ Unconformity- Catahoula sandstone, c Jackson forma- tion, c Yegua for- mation. Cook Moun- tain for- mation. Mount Sel- man for- mation. Thick- ness. Feet. 0-100 1,250- 1,500 200-500 500-800 Lithology and characteristic fossils. Fluviatile deposits, consisting of flint gravel and limestone debris embedded in a clay matrix. In the plateau region west of the Coastal Plain the formation appears as the uppermost terrace of the major streams, lying about 350 feet above the levels of the present stream channels. Along the Cretaceous-Tertiary boundary, the terraces grade laterally into an upland gravel deposit, which caps the interstream areas, but thins and disappears a short distance to the east and south. Lacustrine and littoral deposits, consisting of cross-bedded, coarse, gray, semi-induratea, highly calcareous sand- stones. Lenses of clay in places. Aceratherium and other fossils. East of the Brazos these beds are almost com- pletely overlapped by the lissie gravel. Seaward, the time equivalent of the Dewitt formation is represented by about 800 feet of marine sands and clays, carrying Area carolinensis and other upper Miocene marine fossils and believed to involve some of the lower Pliocene. These marine deposits do not outcrop and are not a part of the lacustrine Dewitt formation, which also includes some deposits of early Pliocene age. Palustrine deposits, consisting of gray, white, and bluish- white, bedded, calcareous clays, with numerous small concretions of lime and some lenses of sand. Littoral deposits, consisting of hard, blue, semiquartzitic, noncalcareous sandstones, with interbedded lenticular masses of green clays. 0-250 375-750 400 Marine deposits, consisting of calcareous blue clays, with large limestone concretions. Carry Levifusus branneri and other Eocene forms. Palustrine deposits, consisting of green clays with concre- tions of selenite; in places, lenses of sand and lignite. Palustrine and marine deposits, consisting of lenticular masses of yellow sand and clay; in places, lenses of green calcareous, glauconitic, fossiliferous marl. Beds of limo- nite and lignite. Some of the clays carry fossiliferous calcareous concretions. Formation as a whole is de- cidedly ferruginous. Fossils: Ostrea sellseformis, Ostrea divaricata, Anomia ephippioides, and others. 350 Palustrine and marine deposits, consisting of red, ferrugi- nous, indurated, and probably altered greensand, with casts of shells, lenses of lignite and clay, beds and concre- tions of limonite. The formation as a whole is conspicu- ously ferruginous. Carries casts of Venericardia plani- costa. a Studies made after the manuscript of this report was prepared seem to indicate that what is here called the Dewitt formation is represented alon^ the Sabine by the beds described as the Fleming clay. 6 As paleontologic studies made after the manuscript of this report was prepared show that deposits con- sidered part of the Fleming clay are not older than M iocene, this formation is referred to the Miocene. (See subsequent list of fossils.) A discrepancy thus exists becween the text of the report and the legend of PI. I, which had already been printed. c Studies made by the author since writing this report seem to indicate that the Catahoula sandstone as here described is not a stratigraphic unit but comprises two formations of similar lithologic character; the one at the base being of Jackson age, whereas the upper sandstone is of Oligocene age. SOUTHEASTERN TEXAS COASTAL PLAIX Cenozoic deposits of the Texas Coastal Plain — Continued. 29 Sys- tem. Series. Formation. ness Lithology and characteristic fossils. >> u 09 U s Eh Eocene. Wilcox forma- tion. Feet. 800- 1,100 Palustrine, marine, and littoral deposits. The littoral de- posits comprise the Queen City sand member, at the top of the formation, consisting of 50 to 200 feet of white, por- ous, loose, water-bearing sands, with someinterstratified clays. The palustrine deposits consist of lenticular masses of sandj clay, and lignite, carrying large, espe- cially characteristic concretions (20 to 30 feet in diame- ter) of hard fhntlLke sandstone; the palustrine clays are leaf bearing, and in places carry teeth of Crocodylus gry- pus. The marine deposits consist of calcareous, glauco- nitic, fossuiferous marls, alternating with beds of sand, clay, and lignite; they are exposed only on Sabine River. Characteristic fossils of the marine phase are Kellia prima, Natica aperta, and Pleurotoma silicata. Midway forma- tion. 250-500 Marine deposits, consisting of black and blue clays with interbedded strata of limestone and some lenses of sand, which are somewhat rare north of the Brazos. Plejona limopsis, Enclimatoceras ulrichi, and other fossils. In the descriptions of the several f orrnations, the symbols used in the several synonymic tables have the following meanings: = Equal in every respect; = equal in a general way; greater than. TERTIARY SYSTEM. EOCENE SERIES. MIDWAY FORMATION. NAME AND CORRELATION. The formation here called the Midway takes its name from Midway Landing, 1 on the west side of Alabama River in Wilcox County, Ala., where it is exposed. The formation extends from Georgia on the east to Texas on the west. Smith and Johnson originally (1887) used the term Midway in describing the beds which represent the lowermost part of what is here termed the Midway formation. In 1889 Penrose described the formation in Texas under the name "Wills Point or Basal clays," from the exposure at Wills Point, in Van Zandt County. In 1892 Harris pointed out the fact that the calcareous beds lying above the Cretaceous and below the Wilcox in Alabama extend east- ward into Georgia and westward into Texas and retain essentially throughout these States the same lithologic and paleontologic char- acter. This stratigraphic division, which is the one recognized in this report, he called the Midway stage. 1 Harris, G. D., The Tertiary geology of southern Arkansas: Ann. Rept. Geol. Survey Arkansas, vol. 2, 1894, pp. 8, 9, 22; The Midway stage: Bull. Am. Paleontology, vol. 1, 1896, pp. 11-13. 30 GEOLOGY AND UNDERGROUND WATERS OF The formation in Arkansas and Louisiana has been described by Harris, in Mississippi by Crider, in Alabama by Smith, and in Georgia by Harris. Beds now recognized as belonging to the Midway have been re- ferred to and described as — <^Eolignitic, lleilprin, Angelo, Notes on the Tertiary geology of the southern United States: Proc. Acad. Nat. Sci. Philadelphia, vol. 33, 1881, p. 159. ^>Black Bluff division of the Lignitic in Alabama (representing the medial portion of the present Midway). Smith, E. A., and Johnson, L. C, Tertiary and Cretaceous strata of the Tuscaloosa, Tombigbee, and Alabama rivers: Bull. U. S. Geol. Survey No. 43, 1887, p. 18. > Midway division of the Lignitic in Alabama (representing the lower portion of the Midway as here recognized). Idem, p. 18. ^>Naheola division of the Lignitic in Alabama (representing the upper portion of the Midway as here recognized). Idem, p. 18. <^Lignitic in Alabama (the present Midway constitutes the lower portion). Idem, pp. 18, 38-63. ~> Matthew's Landing division of the Lignitic in Alabama (representing the upper portion of the Midway as now recognized). Idem, pp. 18, 57-60; and Smith, E. A., and Johnson, L. C, Report on the geology of the Coastal Plain of Alabama: Geol. Survey Alabama, 1894, pp. 27, 181-185. —Basal or Wills Point clays in Texas (representing the equivalent of the Midway as here recognized). Penrose, P. A. F., jr., A preliminary report on the geology of the Gulf Tertiaries of Texas from Red River to the Rio Grande: First Ann. Rept. Geol. Survey Texas, 1890, p. 19. > Clayton in Alabama (corresponding to the lower portion of the present Midway). Langdon, D. W., Variations in the Cretaceous and Tertiary strata of Alabama: Bull. Geol. Soc. America, vol. 2, 1891, p. 594. =Basal or Wills Point clays in Texas (equivalent of the Midway as here recognized). Kennedy, William, A section from Terrell, Kaufman County, to Sabine Pass, on the Gulf of Mexico: Third Ann. Rept. Geol. Survey Texas, 1892, pp. 47-50. = Midway in Arkansas (equivalent of the Midway as here recognized). Harris, G. D., The Tertiary geology of southern Arkansas: Ann. Rept. Arkansas Geol. Survey, vol. 2, 1892, pp. 8, 9, 22; The Midway stage: Bull. Am. Paleontology, vol. 1, 1896, pp. 11-13, 36-37. —Oak Hill-Pine Barren group in Alabama (representing the exact equivalent of the Midway as here recognized). Smith, E. A., Johnson, L. C, and Langdon, D. W., jr., Report on the geology of the Coastal Plain of Alabama: Geol. Survey Alabama, 1894, p. 188. >Sucarnochee or Black Bluff division of the Lignitic in Alabama (representing the medial portion of the Midway as here recognized). Idem, p. 186. > Clayton (Midway) in Alabama (representing the lower portion of the Midway as here recognized). Idem, pp. 192 et seq. =Basal beds or Wills Point clays in Texas (representing the Midway as here recog- nized). Kennedy, William, The Eocene Tertiary east of the Brazos River: Proc. Acad. Sci. Philadelphia, 1895, pp. 144-149. = My rick formation in Texas (including in a general way the Midway and perhaps portions of the Wilcox). Vaughan, T. W., Uvalde folio (No. 64), Geol. Atlas U. S., U. S. Geol. Survey, 1900, p. 2. =Lytton formation in Texas (equivalent of the Midway as here recognized). Hill, R. T., and Vaughan, T. W., Austin folio (No. 76), Geol. Atlas U. S., U. S. Geol. Survey, 1902, p. 6. SOUTHEASTERN TEXAS COASTAL PLAIN". 31 = Midway group in Mississippi (subdivided into a lower formation, the Clayton limestone, and an upper formation, the Porters Creek clay; representing the equivalent of the Midway as here recognized). Crider, A. F., Geology and mineral resources of Mississippi: Bull. U. S. Geol. Survey No. 283, 1906, pp. 22-24. == Midway group in Alabama (consisting of a lower formation, the Clayton lime- stone, a medial formation, the Sucarnochee clay, and an upper formation, the Naheola or "Matthews Landing" formation; representing the equivalent of the Midway as here recognized). Smith, E. A., The underground water resources of Alabama: Geol. Survey Alabama, 1907, pp. 5, 15. OCCURRENCE AND CHARACTER. The Midway is the lowermost of the Tertiary formations in the Coastal Plain of Texas. It lies unconformably above the Cretaceous and conformably below the Wilcox formation. The formation consists of a series of clays and limestones of marine origin. At the base are usually found bluish micaceous clays or clayey sands, containing some light-yellowish fossiliferous lime- stone layers of marine origin. These are succeeded by sandy ledges, on top of which generally rest black selenitic clays. In Texas the formation is from 250 to 500 feet thick and dips from 1° to 5° SE. The geographic location of the outcrop of the Midway formation in the area is shown on the map (PI. I). The outcrop constitutes the eastern marginal prairies and occupies a narrow belt extending approximately north and south in Robertson, Falls, Limestone, Freestone, Navarro, Henderson, Kaufman, and Van Zandt counties. Much of the exposure is obscured by materials of later age. The impervious clay, which is the preponderating material in the composition of the Midway, makes the formation a very poor water carrier. It serves, however, as a confining sheet for the waters of the overlying porous sands of the Wilcox formation and constitutes an important datum plane to guide the well driller. RELATIONS TO ADJACENT FORMATIONS. The structural relations of the Midway formation to the under- lying Cretaceous deposits and to the overlying Wilcox formation are indicated in the geologic sections. (PI. I, in pocket.) Owing to the absence of good exposures it has not thus far been possible to recognize a structural unconformity between these beds and the underlying Cretaceous deposits. The only satisfactory sec- tion showing the relation to the underlying terranes is found on the Brazos, 1 J miles above the Milam County line, and here the Midway apparently rests conformably upon the Cretaceous. But in Missis- sippi, 1 in Alabama, 1 in Arkansas, 1 and on Frio River in Texas, 2 where the » Harris, G. D., The Midway stage: Bull. Am. Paleontology, vol. 1, 1890, pp. 38, 39. 2 Vaughan, T. W., Geological reconnaissance in the Rio Grande coal fields of Texas: Bull. U. S. Geol. Survey No. 164, 1900, p. 36. 32 GEOLOGY AND UNDERGROUND WATERS OF Tertiary-Cretaceous contact is exposed, an unconformity is evident, proving the intervention of a land epoch between the Cretaceous and the Tertiary deposition, and it may be safely inferred that similar conditions exist in the east Texas area. In the region of the Brazos no sharp lithologic differentiation exists between the clays of the Midway and the underlying Cretaceous marls, and the two can be discriminated only by the aid of fossils. The paleontologic break, however, is very marked. PALEONTOLOGY. In Texas the Midway is characterized by the presence of Encli- matoceras ulrichi White, Ostrea pulaslcensis Harris, CucuUsea macro- donta Whitfield, Plejona limopsis (Conrad), Pseudoliva unicarinata Aldrich, and other fossils. (See PI. III.) Plejona limopsis has not thus far been found in the Midway east of the Brazos, but has been found in some material taken from a well at Elgin, in Bastrop County. Fossils were found (1) at Blue Shoals Bluff, (2) at Black Bluff., (3) half a mile up Salt Branch of Little Brazos River, (4) at Smileys Bluff, (5) 5 miles east of Elmo, (6) at Cribbs League Bluff, (7) at Tehuacana, (8) at Josiah Hogan League Bluff, (9) near Tehuacana (10) 4 miles northeast of Kemp, (11) 1 mile up Salt Branch of Little Brazos River, (12) near Kemp, (13) 5 miles northeast of Kemp, (14) near Elmo, (15) at Horn Hill, (16) on Rocky Cedar Creek near Elmo, (17) and on Salt Branch on Dennis Herald survey. A detailed list, with references to the above numbers, follows: Enclimatoceras ulrichi White, 1, 2, 3. Pleurotoina (Pleurotomella?) anacona Harris, 4, 5. P. (Surcula) ostrarupis Harris, 4. Plejona rugata (Conrad), 2, 6. P. precursor (Dall), 4. P.sp.,7. Fusus ostrarupis Harris, 4,6. Pseudoliva ostrarupis Harris, 4. P. ostrarupis var. pauper Harris, 4. Calyptraphorus velatus var. compressus (Aldrich), 1,2,6,8. Aporrhais gracilis Aldrich, 8. Aporrhaissp., 7, 8. Cerithium penrosei Harris, 4. C. whitfieldi Heilprin, 4. Turritella alabamiensis Whitfield, 1, 8, 9, 10. T. mortoni Conrad var., 2, 6, 7. T. mortoni Conrad, 6. T. nerinexa Harris, 2 T. humerosa Conrad, 9. Mesalia pumila var. wilcoxiana Harris, 11. M. var. hardemanensis Harris, 12. M. alabamiensis (Whitfield), 10. Isucula magnifica Conrad, 2, 6. Leda milamensis Harris, 4. Yoldia eborea (Conrad), 1, 2, 6, 8. Cucullsea macrodonta Whitfield, 1, 2, 6, 8. 13, 14. C. saffordi Gabb, 10. Ostrea crenulimarginata Gabb, jr., 4, 9, 15. O. pulaskensis Harris, 1, 6, 8, 16. Modiola saffordi Gabb, jr., 15. Crassatellites gabbi (Safford), 1,2,5,6,8. Venericardia planicosta Lamarck, 5, 7, 15, 17. V. alticostata Conrad, 5, 17. V. alticostata Conrad var., 1, 2, 6, 8. Cytherea ripleyana Gabb, 10. C. sp.,7, 10. U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER 335 PLATE III CHARACTERISTIC FOSSILS OF THE MIDWAY FORMATION. 1, l :l , lb. Enclimatoceras ulrichi White. 2, 2". Ostrea crenulimarginata Gabb. 3, 3*, 3b, 3c. 3d, 3e. Ostrea pulaskensis Harris. 4. Plejona limopsis (Conrad). 5. Plejona rugatus (Conrad). 6, 6 a , Flabellum conoideum Vaughan. SOUTHEASTERN TEXAS COASTAL PLAIN. 33 DETAILED SECTIONS. Brazos River section. — The beds belonging to the Midway formation are typically exposed along Brazos River (see PL I, in pocket) from 1^ miles by river north of the Milam-Falls county line to 2 miles north of the mouth of Pond Creek in Milam County, a total distance of 5f miles by river or about 4^ miles by linear measure across the outcrop at right angles to the strike. The bluff highest upstream that shows these beds and also their contact with the underlying Cretaceous is about 1 J miles north of the Milam-Falls county line : 1 Section exposed in bluff on west bank of Brazos River, southeast line of the Josiah Hogan League, Falls County, Tex. Quaternary: Feet. River alluvium 4 Gravel I Unconformity. Eocene: Midway formation: Blue clay and sand breaking into nodules and conchoidal pieces, weathering into a grayish-yellow clay and con- taining fossils as follows: Calyptraphorus velatus var. compressus Aid. ; Aporrhais gracilis Aldrich; Turritella ala- bamiensis Whitf.; Yoldia eborea (Con.); Cucullsea macro- donta Whitf .; Ostrea pulashensis Harris; Crassatellites gabbi (Safford) .' 5 Transitional blue clay 1 Cretaceous: Massive blue clay with Baculites and other Cretaceous fossils 14 25 One-half mile below the Cretaceous-Tertiary contact just described a bluff at Blue Shoals shows the following section : 2 Section about 1 mile above the Milam County line, west bank of Brazos River, Falls County, Tex. Feet. Pleistocene: Brown sand and river alluvium 10 Unconformity. Eocene: Midway formation: Blue indurated clay with concretions of limestone, contain- ing the following fossils: Enclimatoceras ulrichi White; Calyptraphorus velatus Con. var. compressus Aid.; Turri- tella alabamiensisWhiti.; Yoldia eborea (Con.); Cucullsea macrodontaWhiti., var.; Ostrea pulashensis Harris; Crassa- tellites gabbi (Safford); Venericardia alticostata Con. var.. 5 Laminated blue, almost black fossiliferous clay 4 19 ' Kennedy, William, The Eocene Tertiary east of the Brazos River: Proc. Acad. Nat. Sci. Philadelphia, 1895, p. 145. The fossils were determined by Harris; the list has been partly revised. • * Idem, p. 148. The fossils were determined by Harris; the list has been partly revised. 14926°— wsp 335—14 3 34 GEOLOGY AND UNDERGROUND WATERS OF At the very northern limit of Milam County, 1 mile below the ]) receding section, on the west bank of the river, is Black, or Milam Bluff, about one-third mile long and 40 feet high. Its lower part is composed of very dark, almost black clays containing shell fragments and running into lighter yellowish and greenish clays toward the top. The upper part contains highly calcareous indurated strata showing a nodular structure and containing many fossils. The lower part of the bluff is not so calcareous as the upper part. The beds dip southeast 276 feet to the mile. From them have been collected 1 Enclimatoceras ulrichi White; Plejona rugata (Con.); ( alyptrapJiorus velatus Con. var. compressus Aid.; Turritella mortoni Con. var.; T. nerinexa Harris; Nucula magnified Con.; Yoldia eborea (Con.); Cucullsea macrodonta Whitf.; Crassatellites gabbi (Safford); and Venericardia alticostata Con. var. About three-fourths mile below Milam or Black Bluff on the west bank of the river, on the C. Cribbs League of Milam County in Cribbs League Bluff, the following section is exposed : 2 Section exposed at Cribbs League Bluff, Milam County, Tex. Feet. Quaternary : Surface soil, brown sand and gravel 2 Eocene: Midway formation: Yellow clay 4 Ledge of fossiliferous siliceous limestone 2 Yellow clay ; similar to No. 2 5 Ledge of fossiliferous siliceous limestone 2 Dark-blue laminated jointed clay 30-35 45-50 The fossils collected at this locality include Plejona rugata (Con.), Fusus ostrarupis Harris, Calyptraphorus velatus Aid. var. compressus, TurriteUa mortoni Con., Yoldia eborea (Con.), Cucullaea macrodonta Whitf., Ostrea pulaskensis Harris. Venericardia alticostata Con. var., and Crassatellites gabbi (Safford). Thiee miles by river below Cribbs League Bluff and 2 miles above the mouth of Pond Creek, on the west side of Brazos River and on the northeast corner of the Byrum Wickson League of Milam County, is located Oyster Bluff or Smileys Bluff. The beds exposed represent the uppermost portion of the Midway formation and are the equiva- lent of the Naheola ("Matthews Landing") formation of the Alabama section. 3 » Harris, G. D., The Midway stage: Bull. Am. Paleontology, vol. 1, 1896, p. 128. 2 Kennedy, William, The Eocene Tertiary of Texas east of the Brazos River: Proc. Acad. Nat. Sci. Philadelphia, 1895, p. 147. The list of fossils has been partly revised. 3 Harris, G. D., New and otherwise interesting Tertiary mollusca from Texas: Proc. Acad. Nat. ScL Philadelphia, 1895, p. 45. SOUTHEASTERN TEXAS COASTAL PLAI^. 35 Section exposed at Smiley s Bluff, west bank of Brazos River and northeast corner of Byrum Wickson League, Milam County, Tex. Quaternary : Feet. River alluvium 4 Conglomerate 2 Coarse conglomerate with bowlders 2± Eocene: Wilcox formation: Thinly stratified, yellowish-gray clay, sand and blue clay, with some rounded concretions of calcareous sandstone 10 Midway formation: Blue laminated clay, fossiliferous 4 Thin bed of concretions and hard fossiliferous limestone. . 1 Thinly laminated gray clay and sand 3 Bluish-gray sand 1 Thinly laminated dark-blue clay and sand 3 Dark-blue laminated fossiliferous sand 2 32 The fossiliferous beds of the Midway cany Pleurotoma (Pleuroto- mella) anacona Harris, P. (Surcula) ostrarupis Harris, Plejona precursor Dall, Fusus ostrarupis Harris, Pseudoliva ostrarupis Harris, CeritJiium penrosei Harris, C. wMtfieldi Heilprin, Leda milamensis Harris, and L. milamensis Harris, large var. 1 The complete section along Brazos River is indicated in the dia- gram on Plate IV (in pocket). Falls County. — Along Salt Branch of Little Biazos River on the Dennis Herald Survey in Falls County, limestone of the Midway for- mation is exposed. One-half mile above the confluence of the two streams specimens of Enclimatoceras ulrichi White, Venericardia planicosta Lam., and Venericardia alticostata Con. var. are found, and a mile above the confluence, Mesalia pumila var. wilcoxiana (Aid.) occurs. 2 Limestone County. — At Horn Hill in Limestone County, the Mid- way formation is exposed and carries Turritella Jiumerosa Con., Ostrea crenulimarginata Gabb, jr., Modiola saffordi Gabb, jr., and Venericardia planicosta Lam. In the vicinity of Tehuacana are exposed limestones of the Mid- way formation, which are probably the correlative of limestone No. 14 in Smith and Johnson's section near Oak Hill, Wilcox County, Ala. 3 The stratum is probably the same as that exposed at Horn Hill and represents about the medial portion of the Midway forma- tion. The section follows. 1 1 Kennedy, William, The Eocene Tertiary of Texas east of the Brazos River: Proc. Acad. Nat. Sci. Philadelphia, 1895, p. 146. The list of fossils has been partly revised. 2 Harris, G. D., The Midway stage: Bull. Am. Paleontology, vol. 1, 1896, p. 129. 3 Harris, G. D., The geology of the Mississippi embayment, with special reference to the State of Loui- siana: Rept. Geol. Survey Louisiana, 1902, p. 9. 3(i GEOLOGY AND UNDERGROUND WATERS OF Section of Midway formation near Tehuacanu, Limestone County, Tex. Whitish to grayish- white limestone carrying Plejona sp., Turritella Feet. humerosa Con., T. alabamiensis Whitf., Venericardia planicosta Lam., and Cytherea sp 40 Brownish-gray sand changing to brown near base. Black ahaly clay. The brownish-gray sand near the base carries many indefinite fossil remains, among them fairly well preserved imprints of Turritella mortoni var. These fossils occur about 45 feet below the base of the limestone. About 70 feet below the base of the limestone, in black shaly clay, the same fauna includes fragments of Nautilus?, Pleuro- toma and Aporrhais; and large calcareous concretions are common. Ostrea crenulimarginata has been found in the vicinity of Tehuacana. The attitude of the limestone varies considerably; in places it dips 45°; the direction is generally to the south-southeast. 1 Kaufman County. — Four miles northeast of Kemp the Midway formation is represented by light-gray and yellowish calcareous sand- stones yielding Turritella alabamiensis Whitf., Mesalia alabamiensis (Whitf.), M. pumila var. Jtardemanensis (Gabb), Cucullsea macrodonta Whitf., and Cytherea ripleyana Gabb. Five miles east of Elmo, on the public road crossing of Rocky Cedar Creek, outcropping limestones of the Midway formation carry 2 Pleuro- toma anacona Harris, CucuUgea macrodonta "Whitf., Ostrea pulaskensis Harris, CrassateUites gabbi (SarTord), Venericardia planicosta Lam., and V. alticostata Con. var. Van Zandt County. — It was from the exposure of the Midway for- mation in the vicinity of Wills Point, in Van Zandt County, that Pen- rose gave it the name " Wills Point clays." The general section ex- posed in this vicinity, as reported by Kenned j", 3 is as follows: Section exposed in the region around Wills Point, Tex. Midway formation : Feet. Yellowish-brown sand containing calcareous bowlders of sand- stone, limestone with thin veins or seams, some nodules of crys- talline calcite, and occasional fossil remains 30 Yellow laminated clay with thin partings of yellow sand and some bowlders of siliceous limestone 90 Massive bedded clay, showing no signs of lamination, containing numerous bowlders similar to those of No. 1 30 White limestone containing great quantities of fossil casts, chiefly Turritella (?), Cardita ( Venericardia) planicosta, Ostrea (?), and other bivalve shells S 1 Harris, G. D., The Midway stage: Bull. Am. Paleontology, vol. 1, 1896, p. 129. 2 Idem, pp. 129-130. 3 Kennedy, William, A section from Terrell, Kaufman County, to Sabine Pass on the Gulf of Mexico: Third Ann. Rept. Geol. Survey Texas, 1892, p. 49. SOUTHEASTERN TEXAS COASTAL PLAIN. 37 Midway formation — Continued. Brown sand 2 Limestone similar to the white limestone above 10 Bluish-gray sand 30 Dark-blue laminated and much-jointed clays with thin sandy partings, containing occasional small bivalve shells chiefly, and having a thin pavement of siliceous nodules near its upper surface 62 262 The beds dip southeast 91 to 276 feet to the mile. WILCOX FORMATION. NAME AND CORRELATION. The formation here considered is called the Wilcox, 1 after Wilcox County in Alabama, where it is characteristically exposed. It was first recognized and described in 1894 by Harris, who gave it the name "Lignitic." The same group of beds was called " Chickasaw" by Dall in 1896, "Sabine" by Veatch in 1906, and Wilcox by Crider in 1906. "Lignitic" is a lithologic and not a geographic name and therefore is not in accord with the rules of geologic nomenclature. "Chickasaw" was originally proposed by Hilgard as an equivalent for the beds he called the "Northern Lignitic," in which he included beds belonging to the Wilcox, Claiborne, and Jackson ; Dall used the term later to apply to beds here recognized as Wilcox. "Sabine River beds" was applied by Penrose in 1890 to deposits that in- cluded a portion of the Claiborne, and his use of this term would have precedence over Yeatch's use of "Sabine." Wilcox is thus the only name to which there are no objections, and it is therefore adopted in this report as the proper designation for this division of the Eocene. The Wilcox formation occurs in Texas, Arkansas, Louisiana, Mississippi, Alabama, 2 and Georgia. 3 In his classification of the Tertiary sediments of Mississippi, Hilgard in 1860 recognized at the base of the system a group of beds containing lignite which he called the "Northern Lignitic" and in which he included the Midway formation and the Wilcox formation as here recognized. In 1881 Heilprin called attention to the fact that the basal Tertiary deposits in Alabama contained lignite, and he named the deposits that appeared below the Claiborne and above the Cretaceous the "Eolignitic." These beds were the same as those called by Hilgard Crider, A. F., Geology and mineral resources of Mississippi: Bull. L T . S. Geol. Survey No. 2S3, 19CH5, pp. 25-28. a Smith, E. A., The underground water resources of Alabama: Geol. Survey Alabama, 1907, pp. 15, 16. 8 McCallie, S. W., A preliminary report on the underground waters of Georgia: Bull. Geol. Survey Georgia No. 15, 1908, pp. 34, 35. 88 GEOLOGY AND UNDERGROUND WATERS OF "Northern Lignitic." Later (1887) Smith and Johnson substituted "Lignitic" for "Eolignitic." The first authentic account of the Texas representatives of the Wilcox was given in 1890 by Penrose, who described them, in con- junction with what are now called the Mount Selman and Cook Mountain formations, as the u Timber Belt or Sabine River beds." He fixed their stratigraphic position correctly as lower Tertiary overlying the Midway, but made no attempt to correlate them with the various divisions of the Tertiary established by Hilgard in Mississippi in 1860, and by Smith and Johnson in Alabama in 1887. In 1894, Harris pointed out for the first time that the group of beds that contained lignite in the Coastal Plain region was strati- graphically continuous from Alabama on the east to Texas on the west, and that it was lithologically distinct from the formation below now recognized as Midway, which had been considered heretofore as a part of the lignitiferous group. He r therefore, recognized two units in place of the "Northern Lignitic" of Hilgard and the ''Lig- nitic" of Smith and Johnson. The lowermost he called the Midway and the uppermost the "Lignitic." This classification has been found to be valid, and is the one followed in this report, though the name Wilcox is substituted for "Lignitic," because the latter is not a geographic name. In 1897, Harris . pro ved that the lower lignitiferous formation in Texas was also paleontologically equivalent to the lithologically and stratigraphically similar group in Alabama and Mississippi. Beds here considered as constituting the Wilcox formation have been previously referred to as — ^Northern Lignitic in Mississippi (included also the Midway). Hilgard, E. W., Report on the geology and agriculture of the State of Mississippi, 1860, pp. 110-123, and map. Mansfield group (included only a portion of the Wilcox as here recognized ; re- ferred by Hilgard to the Vicksburg). Hilgard, E. W., Summary of results of a late geological reconnaissance of Louisiana : Am. Jour. Sci., 2d ser., vol.48, 1869, p. 340.