STRATIGRAPHY. 25 



easily distinguished.* They consist of a stiff laminated clay,, yellow, gray, 

 blue, or bluish-green in color, frequently interbedded with seams and lammse 

 of sand, containing many concretionary masses of gray non-fossiliferous lime 

 stone, the latter much cut up by veins of brown crystalline calcite, and vary- 

 ing in size from a few inches to six feet in diameter. They are generally of 

 a flat elliptical shape, and of a gray color. Large quantities of gypsum are 

 also found in places in the clay. One of the most constant characteristics of 

 the clay is the presence in it of soft small white calcareous concretions one- 

 tenth of an inch to two inches in diameter, and often having the cauliflower- 

 like form of some of the geyserite of the Yellowstone Geyser basins. These 

 are found very plentifully, and often collect in large quantities in creek beds. 

 No lignite beds have been seen as yet in these clays. f Such deposits are 

 found well developed at Wills Point, in Van Zandt County. West of Wills 

 Point is seen a deposit of shell limestone, composed almost entirely of shells of 

 Lower Eocene fossils It is traceable up and down Rocky Cedar Creek for 

 seven miles, and underlies the divide between Rocky Cedar and Muddy Cedar 

 creeks, a distance of four miles. The following section of a well on this di- 

 vide shows the character of this bed. 



1. Sand, gray and buff color 3 feet. 



2. Gray and yellow clay (Basal Clays) 9 feet. 



3. Shell limestone 3 to 4 feet 



4. Coarse sand 1-| to 2 feet. 



5. Shell limestone 3 to 4 feet. 



6. Sand in bottom of well. 



The Rocky Cedar limestone is probably the lowermost bed of the Tertiary 

 series in this part of the State. The shell limestone bed is probably of lim- 

 ited extent, occupying no very important stratigraphical position, and appear- 

 ing at the base of, and as a component part of, the Basal Clays. It is of great 

 importance, however, as showing the geological position of the lowermost 

 Tertiary strata in Northern Texas." 



THE TIMBER BELT OR SABINE RIVER BEDS. 



"The Basal Clays, everywhere from the northern part of the State to the 

 Colorado River, blend upwards into the sandy Timber Belt Beds. These form 

 the mass of the Tertiary formation in Texas, and underlie the great timber 

 region of the eastern part of the State. They are composed entirely of sili- 

 ceous and glauconitic sands, with white, brown, and black clays. The clays, 



*The Basal Clays are probably largely derived from the destruction of the underlying Cre- 

 taceous strata. 



f These clay beds probably represent the Eo-lignitic of Heilprin's Eocene section, the base 

 of Hilgard's "Northern Lignitic" in his Mississippi section, and the Arkadelphia Shales at 

 the base of Hill's "Camden Series" in Arkansas. 



