PENNSYLVANIAN STRATIGRAPHY OF TEXAS 



23 



and sand are much the most important rock types, but the Hme- 

 stones form persistent escarpments and are prominent, especially 

 in the upper part and to the south. Conglomerates are found 

 chiefly in the north. They are composed, for the most part, of 

 small angular fragments of the resistant materials from other 

 sedimentary formations. The shales are commonly sandy. The 

 limestones are for the most part fine-grained and yellow to gray 

 in color. 



Thickness. — The total thickness of the Pennsylvanian of Texas, 

 computed from measurements of the surface outcrops, is as a 

 maximum about 6,800 feet. A compilation of average thicknesses 

 for each of the divisions gives a total of 5,350 feet. As a matter 



Fig. 2. — Diagrammatic section through the Pennsylvanian of Texas 



of fact, the thickness of the total section is somewhat less than 

 the total of measurements of thickness at the outcrop, for there 

 appears to be a very important overlap of the beds from east to 

 west, so that above the Bend the older divisions disappear suc- 

 cessively in going to the west. This is illustrated by the diagram- 

 matic section. Figure 2. 



The average thicknesses of the divisions of the Pennsylvanian in 

 Texas are indicated in the table of formations. 



Topography. — The outcrop of the Pennsylvanian rocks and of 

 each of the major divisions of the Pennsylvanian in north Texas 

 is characterized by the topography. The Pennsylvanian area as a 

 whole is distinguished by its prominent and very persistent escarp- 

 ments. Due to the character of the soil and the climate, there is a 

 widespread cover of mesquite, scrub oak, and cactus, with belts of 



