30 GULF TERTIARY OF TEXAS. 



trop County. It consists of thin interstratified layers of glauconitic marl, 

 black clay, and dark siliceous sand with glauconite specks, and is the first 

 fossil-bearing stratum seen since leaving Travis County. Interstratified with 

 these deposits is a hard indurated ledge of calcareous rock, made up largely 

 of glauconite and weathering white.- Dark gray round and oblong calcareous 

 concretions are found throughout the clay and sand. The oluff is about ten 

 feet high, and about half way up it is a bed three to eight inches thick, very 

 much rusted and with streaks of hard-pan. This seam is the one which con- 

 tains most of the fossils, and in some places is almost entirely made up of 

 them. They are largely of the Claiborne age. The sands are cross-bedded 

 and the whole bluff is heavily charged with iron pyrites. Numerous specks 

 of lignite are found, even with the shell-bearing strata, proving beyond a 

 doubt the littoral character of the deposit. The dip is about horizontal. For 

 four miles below this are seen similar ledges of the same strata, all preserving 

 an almost horizontal dip. Frequently gypsum crystals are found in the clays. 

 Four miles below the beginning of this fossiliferous area we come to what is 

 locally known as the Devil's Eye, an eddy at a low ledge of a similar forma- 

 tion to those just described. The strata here belong to the same series as those 

 just passed. The fossil bearing bed is six to twelve inches thick, is semi- 

 indurated, and composed almost entirely of glauconite and shells. Specks 

 of lignitic matter are found throughout the associated chocolate clays, and 

 also, occasionally, small quantities of rusty clay ironstone are seen. Dip, 

 horizontal. Alum Creek Bluff is at the mouth of Alum Creek and a short 

 distance above Smithville. It is forty feet high, and shows the same char- 

 acter of strata and the same shell bed as is seen at Devil's Eye. It is under- 

 laid by twenty feet of much cross- bedded sands, and dips 3 degrees to the 

 southeast. Between here and Smithville is seen a series of interlaminated 

 sands and clays, barren of fossils and dipping 5 degrees southeast. At Smith- 

 ville, in the eastern part of Bastrop County, are found interbedded deposits 

 of glauconitic marls and chocolate clays in a bluff thirty feet high and capped 

 with Quaternary gravel. The glauconitic marl is hardened and rusty in 

 places, and in others is soft, green, and entirely unaltered. It is highly fossil- 

 iferous and contains numerous Claiborne species.* Dip 3 to 8 degrees south- 

 east. One mile below is a small lignite bed underlaid and overlaid by choco- 

 late sands. Below here the river makes a turn to the northeast and again 

 intersects the same bed as is seen at Smithville. White Marl Bluff is near 

 the Fayette County line, is ten feet high and composed of interbedded strata 

 of dark gray clay, glauconite, gray sand, and a creamy white shell-bearing 

 calcareous marl. These beds vary from one to twelve inches thick, and are 



* This is the locality referred to by Dr. Buckley "near Mrs. G-azeley's." First Annual 

 Report, Geological and Agricultural Survey of Texas, S. B. Buckley, 1874, p. 64. 



