PENNSYLVANIAN STRATIGRAPHY OF TEXAS 25 



CLASSIFICATION OF THE TEXAS PENNSYLVANIAN— Cow^i««e(i 



cedar locally along the prominent limestone ridges. The area of 

 the Bend has a rough, semimountainous topography w^hich results 

 from the resistant character of the massive, thick limestone of the 

 Marble Falls formation. The Strawn area is distinguished by 

 prominent but irregular escarpments which are produced by the 

 hard sandstone beds. The weathering of the shales and the 

 disintegration of the sandstone produces flat, sand-covered bottom 

 lands, but the bold escarpments along Brazos and Colorado rivers 

 dominate as topographic features. The Canyon, as the name some- 

 what fortuitously suggests, gives rise to a very rough, deeply 

 chiseled topography which is one of the prominent geographic 

 features of north central Texas. The massive limestone beds make 

 high, sharp-edged escarpments which make travel from east to 

 west very difiicult. The Cisco produces a topography of gentler 

 relief, with broad, open valleys and less prominent, though well- 

 defined, escarpments. 



Divisions. — -In making the new geological map of the Texas 

 Pennsylvanian, attempt has been made to present a classification 

 which, conforming as closely as possible to the well-known divisions 

 of Cummins, will apply equally to the whole area from the north 

 to the south. Carefully measured and studied sections across the 



