POST-CRETACEOUS HISTORY OF WESTERN WYOMING 215 



uplift have been eroded much more rapidly than they otherwise 

 would have been. The Archean exposures of the Owl Creek 

 Range are not large, and probably did not appear until the last 

 two or three thousand feet of denudation were accompKshed. We 

 are reduced, therefore, to a consideration of the Wind River Range 

 as the only part of the district in which the Archean rocks are 



■■-^'1 



Fig. 28. — A typical canyon in the hard Carboniferous rocks of the Wind River 

 Range, twelve miles west of Lander. 



broadly exposed and under simple conditions. The Bighorn, 

 Sherman, and certain other ranges in the state should probably be 

 put in the same category. 



significant that this is true of the Phillips Canyon fault which appears to join the main 

 Teton fault at an acute angle as if it were merely a branch of it; (c) sedimentary rocks 

 to a thickness of perhaps more than 10,000 feet have been removed from the Teton, 

 block since it was first elevated, but these are still preserved in the bottom of Jackson 

 Hole; {d) the abruptness and height of the escarpment decrease immediately and 

 markedly toward the north and south ends of the range, as quickly as the outcrops 

 of the less resistant Paleozoic and Mesozoic strata are reached; (e) the flat-bottomed 

 part of Jackson Hole coincides almost exactly with the distribution of the weakest 

 Eocene clays and the valley becomes narrow again southward as soon as the Cretaceous 

 outcrops are reached. 



