142 II. F. BAIN — GEOLOGY OF THE WICHITA MOUNTAINS 



through the south granite range. This outwash is far heavier on the 

 south than the north side of the mountains, and boulders 6 to 8 inches 

 in diameter were quite frequently found as much as 15 miles south of 

 the mountains in such quantity as to preclude any hypothesis of their 



adventitious character. The suggestion is that there has been a marked 

 differential rise to the north, and that any early limestone hills on the 

 south have been buried by Permian and recent outwash. 



Age of the Mountains 



The preceding sketch of the geology has perhaps shown clearly enough 

 what the conclusion must be as to the age of the mountains, but possi- 

 bly a word or two of summary may not be out of place. It is evident 

 that there was a pre-Cambrian land-mass of igneous rocks, and that over 

 this was laid down an undisturbed sequence stretching from the Cam- 

 brian up to and including the Trenton. Then came the main upheaval 

 and the intrusion of the granite. Around the edge of the new moun- 

 tains the Geronimo series was laid down. The shearing and faulting of 

 the granite and the presence of greenstone dikes cutting it, with the 

 true though slight dip of the Geronimo beds, indicate later' disturbances 

 of lesser degree. Since the intrusion of the granite, however, the main 

 history of the region has been one of vigorous and long continued ero- 

 sion, through which the mechanical sediments of the Red beds and later 

 deposits were prepared and distributed. That there was a notable in- 

 terval of erosion between the intrusion of the granite and the Geronimo 

 beds is shown by the presence of granite pebbles in the latter. Granite 

 being intrusive, these pebbles could onl3 r be obtained after the erosion 

 of a considerable amount of rock. 



Report on the Fossils from the Wichita Mountains by Stuart 



Welle r 



The following determinations of the geologic horizons in the Wichita 

 mountains have been made from a small collection of fossils submitted 

 to me by Mr H. P. Bain, supplemented by a small collection secured 

 by Professor R. D. Salisbury. The fossils are all poorly preserved 

 and in almost every instance are imperfect or fragmentary, so that defi- 

 nite identification of the species is in most cases not practicable. They 

 indicate, however, the presence of three distinct horizons, the lowest of 

 which may be referred to the Cambrian and the two upper ones to the 

 Ordovician. 



