086 J. W. BEEDE BEDS OF APPALACHIAN AND WESTERN SECTIONS 



"A feature of importance in the Cisco formation, and one which it shares 

 with the next formation, is the series of changes observed as the formation is 

 traced northward along the strike. These changes relate both to changes in 

 lithologic character and to thickness of beds. In the Colorado Valley, inter- 

 stratified with sandstones, clays, and conglomerates, are six or more beds of 

 limestone, each from 5 to 25 feet thick and all aggregating a thickness of 100 

 to 150 feet. In the southern part of the Brazos Valley the calcareous divisions 

 are only about half as thick as they are farther south, and clays show a corre- 

 sponding increase in thickness. In Young County the calcareous material 

 diminished in thickness northward at an increased rate until, at the northern 

 boundary of the county, the limestones have practically disappeared, and be- 

 yond that point they are represented apparently by irregular nodular masses 

 of earthy limestone in a matrix of clay. With the thinning out of the lime- 

 stones, the shales and sandstones increase in thickness. In Stephens County 

 and farther south the shales are prevailingly blue and the sandstones gray. 

 Red beds are dispersed sparingly through the formation. The blues gradually 

 give place to reds until in the vicinity of Red River the red color dominates. 

 In this part of the region the rocks consist, for the most part, of red sand- 

 stones, clays, and sandy shales, with a few beds of blue shale and bluish to 

 grayish white sandstones. Limestones are conspicuously absent."' - 1 



The data here briefly summarized clearly show that the red sediments 

 set in quite as early in the Ar buckle Mountain region, or north and south 

 of it, as they did in the Appalachian region. Indeed, were all the Ap- 

 palachian red beds still intact, there would be little reason to doubt that 

 they would be found to be practically equivalent in age with the lowest 

 of the red beds of the Pottawatomie- Seminole region and similar regions 

 south of the Arbuckle Mountains. 



For this reason it is apparent that it is unnecessary to postulate a dif- 

 ferent climate for the Appalachian region than that which existed in the 

 western interior region. 



Nevertheless, the fact that the red beds are as old in the western in- 

 terior region as in the Appalachian Plateau does not explain the peculiar 

 distribution of the vertebrates under consideration — that is, that the 

 younger forms occur in the western region, while the older forms are 

 known only from the region east of the Mississippi Eiver. There are two 

 factors bearing on this point that need to be discussed, neither of which 

 is necessarily conclusive in itself, but between them they appear to include 

 the probabilities of the case. 



First. In the basal Permian, White, as quoted above, has shown that 

 Waichia and some other plants are present in the western province while 

 wanting in the eastern. This would imply that at the inauguration of 

 the basal Permian the Appalachian region was isolated from the western 

 region in such a manner as to prevent the intermigration of the plants. 



C. IT. Gordon: U. S. Geol. Survey, Water Supply Paper .".17, 1913, p. 18. 



