48 COLORADO COLLEGE STUDIES. 



concealed beneath a blanket of Cretaceous and later 

 deposits. 



It might naturally be considered by some that the 

 transitional character of the horizon of passage from the 

 Big Basin sandstone to the Cretaceous sandstone rein- 

 forced the earlier generalh^ accepted view that the "red- 

 beds" were Jura-Trias, or at least partly so; but the bond 

 of continuity which has already been referred to as appar- 

 ently existing between the Cimarron series of Kansas and 

 the paleontologically proven Permian of northern Texas 

 outweights any argument of that sort, and indicates rather 

 that the upper and here lighter-colored zone of the Big 

 Basin sandstone was softened by the invading waters of 

 the Belviderean sea, and its sediments partially and then 

 wholly rearranged as the (for this point) initial deposits of 

 the latter, only gradually becoming supplanted by sedi- 

 ments conveved from other sources. 



Supplementary Note. — The Sumner division is named after 

 Sumner county, which includes nearly the entire breadth of the area 

 of its outcrop in southern Kansas. The Cimarron series is named 

 from the Cimarron river, in whose basin the rocks of both of its divi- 

 sions are so extensively displayed. 



