SEDIMENTARY ROCKS 141 



all evidence as to the age of the beds must be derived from the stratig- 

 raphy. They are manifestly later than the granite intrusion, and in 

 composition and character resemble the known Paleozoic rocks of the 

 region. They are earlier than the Red beds (Permian), as they pass 

 under the latter. It is to be hoped that further study may be devoted 

 to them. 



RED BEDS 



The sandstones and shales of the Permian cover much of the prairie 

 between the Washita river and the mountains. They were observed at 

 many points in the course of the present work, but nothing with regard 

 to them can be added to previous knowledge. They were nowhere seen 

 to have been involved in the dynamic movements which have given a 

 slight dip even to the Geronimo beds. They were seen quite near the 

 mountains and wholly undisturbed. It would not be strange if at some 

 point escaping observation they showed a certain amount of disturbance 

 which might be traced to relatively recent and slight movements. 



CRE TA CEO US A ND TER TIAR Y 



Mr Robert T. Hill reports the former entirely absent from the moun- 

 tains, and this accords entirely with our own observations. Comstock 

 has assigned to the latter, under the name of Fort Sill beds, certain of 

 the surface materials covering the intermontane pastures. There seems 

 no good reason for this. The material is, as Vaughan remarks, litho- 

 logically similar to that which makes up. the Red beds. Community of 

 genesis probably accounts for this. The outwash from the mountains 

 would be of much the same character, regardless of the time when it was 

 deposited, and, while the matter may in its present condition be fully 

 conceded to be one mainly of opinion, the author is inclined to treat 

 these beds as of recent origin. 



ALLUVIUM 



Whatever may be the ultimate decision in regard to the beds just 

 mentioned, it is perfectty certain that there is along the south side of the 

 mountains a vast quantity of material which can not be considered to be 

 other than recent. On West Cache creek beyond Quanas there are great 

 beds of sand and recent conglomerate rising 50 feet above the present 

 stream. The passes in the south range of mountains show great alluvial 

 fans, which curiously enough in one or two instances seem to have choked 

 the old passes and led to the capture of the headwaters of intermontane 

 creeks by younger streams, which have cut new and sharp walled canyons 



