52 



GULF TERTIARY OF TEXAS. 



country; thence into the flat prairies about Sealy, San Felipe, and other 

 places, where we finally reach the Post-Tertiary strata. Timber occurs along 

 the streams and in inland groves throughout this region, and has already 

 been mentioned on page 8. The sections of the Fayette Beds on the Colo- 

 rado and Brazos Rivers and the Rio Grande are described below. 



COLOEADO EIVEE SECTION. 



As we enter the country underlaid by the "Fayette Beds," going down 

 the Colorado, we pass a series of low bluffs, composed of dark gray or black 

 clays, much jointed and faulted, until the mouth of Barton Creek is reached. 

 Here there is a bluff over 100 feet high and composed of clay and sandy 

 strata, as represented in the following section: 



1. Red quaternary gravel and sand 12 feet. 



2. Light brown sand and clay 16 feet. 



3. Lenticular bed of lignite 1| feet. 



4. Chocolate colored sand and clay, with gypsum and sulphur 10 feet. 



5. Lignite 1 foot. 



6. Interlaminated beds of gray sand and clay of a black, chocolate or watery- 



green color, with gypsum and sulphur 55 feet. 



7. Lignite 2 to 4 feet. 



8. Similar strata to those of (6) , 3 feet. 



The whole formation is much faulted and jointed, and dips 2 to 5 degrees 

 southeast. A representation of one of the jointed lignite beds is seen in Fig. 2. 



Fig-. 2. — Faulted lignite bed, Barton Creek Bluff. 



From here to within twelve miles, by river, of La Grange we pass^over a 

 series of outcrops of similar sand and clay strata, all dipping in the same 

 direction, and frequently containing rusty masses of carbonate of iron. At 

 this point we come to what is locally known as Chalk Bluff, on account of the 

 resemblance of the hard clay to chalk. It dips 5 degrees southeast, and is 100 

 feet high. The following section is made up from different parts of the bluff. 



