3IO 



ELIOT BLACKW ELDER 



Fremont cycle : The oldest cycle recognized, of which the visible 

 result was the "Wind River peneplain," may for the sake of uni- 

 formity be called the Fremont cycle, from the fact that the principal 

 remnants of the Wind River plateau (Figs. 12-15) ^^Y be over- 

 looked from Fremont Peak. In the Wind River Range the rem- 

 nants of this surface attain elevations of 11,300 to over 12,000 feet, 

 and in adjacent regions to the west other remnants supposed to be 

 of the same age are between 10,500 and 11,000 feet above sea-level. 

 Its features have been sufficiently described in Jour. GeoL, XXIII 

 (19 1 5), 193-94- 



TABLE II 



Epoch 



Erosion Cycles 

 (Largely Interglacial) 



Glacial Stages 



Stages according to 

 Westgate and Branson 



Recent .... 



Post-glacial 



















Pinedale 



Late glacial and 







terraces 





Lenore 



















Bull Lake 



Early glacial 









Circle 





Plain No. i 



Pleistocene 













Buffalo 















Black Rock. . . . 





Plain No. 2 













Union Pass 





Plains Nos. 3 and 









4 



Pliocene 



Fremont 





Summit peneplain 











Union Pass cycle : The next stage in the denudation is typically 

 represented by a post-mature surface cut upon the resistant 

 Archean and Paleozoic rocks near the west end of the Wind River 

 Range notably below the summit peneplain. It is evidenced by 

 the broad, shallow, and well-graded valleys with elevations of from 

 9,000 to 9,500 feet at Union Pass and west of Sheep Mountain. 

 East of Kendall, Little Flat-Top Mountain, of about the same ele- 

 vation, is a beveled remnant of highly inclined Cretaceous rocks. 

 Along the northeast slope of the Wind River Range, aged topo- 

 graphic forms high up on the mountain sides probably represent 



