34 RAYMOND C. MOORE AND FREDERICK B. PLUMMER 



section along Brazos River, that is, from the base of the massive 

 limestone on the East Fork of Keechi Creek, now named the Palo 

 Pinto limestone, to the top of the massive limestone which outcrops 

 near Finis on the line between Jack and Young counties. The 

 latter has been found to be equivalent to the Home Creek limestone 

 of Drake in the Colorado River Valley. Conditions were more 

 uniform in the north Texas region during the Canyon epoch, and 

 it is possible to trace many of the stratigraphic subdivisions for 

 very long distances. As shown in the table of formations, there 

 are four formations in the Canyon of the Brazos Valley, in order 

 from the bottom: Palo Pinto, Graford, Brad, and Caddo Creek; 

 in the Colorado Valley there are three, the Palo Pinto not being 

 represented. The total thickness of the group ranges from an 

 average of about 500 feet in the south to 800 or 900 feet in the north. 

 The outcrop is correspondingly wider in the north. 



The Palo Pinto limestone is a thick, crystalline, dark gray rock 

 made up typically of beds 2 to 6 inches in thickness and having a 

 total thickness of 50 to 100 feet. It forms a prominent escarpment 

 across Palo Pinto County and has been traced for a long distance in 

 the Brazos Valley. It has not, however, been identified south of 

 the Cretaceous overlap in Eastland County which separates the 

 Pennsylvanian outcrops. The basal beds of the Canyon consist 

 here of wave-worked sands, thin, brecciated limestone containing 

 pebbles of black limestone, chert, and conglomerate. Evidently 

 there was land no great distance farther south, in the region of the 

 present Llano Mountains. The chief distinguishing feature of the 

 fossils which have been found in the Palo Pinto formation is their 

 very robust size, many species being represented by individuals 

 more than twice the normal size. 



The Graford formation, named from the town of Graford in 

 northern Palo Pinto County, consists of a thick, locally very 

 fossiliferous shale, the Brownwood member, below, and a massive 

 escarpment-forming limestone, the Adams Branch member, above. 

 These divisions are well developed both in the south, where they 

 were differentiated by Drake, and in the north. The Brownwood 

 shale is about 160 feet thick near Brownwood, but at least 400 feet 

 near Graford. A conglomerate at the base of the formation in the 



