24S - I. EMMON OROGRAPHIC MOVEMENTS. 



/• oeU Survey. — Major J. W. Powell* in his flrsl account of the Colorado 

 river, explains the tortuous nature of the upper portion of its course (the 



■ I, river athwar! the Uinta mountains on the hypothesis that the coun 

 being already determined previous to the uplift of these mountains its bed 

 was deepened paripauu with the slow uplifting of the mountains, furnish- 

 ing an illustration, which has been widely quoted in text booksf and els 

 where, of the bIow rate of mountain elevation. This hypothesis involves a 

 conformable deposition of all the beds involved in or affected by the Dinta 

 fold, Bince it is evident that sedimentation could not be going on in a region 

 through which a river was running and cutting down or corrading its bed. 

 1 1 . ii.-. the Uinta fold should have commenced after the deposition of the 

 latest sediments deposited along its flanks — that is. in Tertiary or Recent timi 8. 

 In lii- second volume, however, he recognizes tin 1 fact that tin- Uinta fold 

 was formed at the close <>i' Mesozoic time, and that during Tertiary times 

 no less than four lake- were successively formed and drained during dry-land 

 epochs, in which 8,000 feet of sediments were accumulated, largely from 

 materials resulting from the degradations of the Uinta fold, ami that th< 

 Bediments did not arch over the crest of the Uinta fold. He found, what 

 hail not been observed by the geologists of the Fortieth Parallel, an uncon- 

 formity by erosion between the Carboniferous and underlying Uinta sand- 

 stone, to which he assigned provisionally a Devonian age, showing that a land 

 surface must have existed there during <>v previous to Carboniferous time. 

 II. ;il-., recognized, in accordance with the previous observations <>t' the 

 Fortieth Parallel geologists, the existence of a submerged cliff of Eozoic 

 rocks at Red creek Red Creek quartzites) against which 8,000 feet of Uinta 

 sandstone were deposited. He considers Cenozoic time as the main mount- 

 ain-building epoch, and regards the Park province or Rocky Mountains as 

 of the Uinta type of structure — that i-. that the sedimentary beds now rest- 

 ing against their Hanks formerly formeda complete arch over their crests, or 

 that they were completely submerged during the deposition of these beds. 



Win > h r Sun-i ii. Of the geologists of the Wheeler Survey,} Gilbert re< 

 ni/.es in Utah, Nevada, Arizona, and New Mexico the universality of the 

 unconformity between Archaean and succeeding sediments, whether Cambrian 



later. He accepts King's assignment of the Jurassic a- the date of orig- 

 inal formation of the Basin Ranges, but considers that the Plateau region 

 was submerged from early Palaeozoic t" the close of Mesozoic time, though 

 cted to oscillations of level producing changes in depth of waters and 

 [uently in characl diments. While remarking upon the mea 



I ■ Expl ■ ■ ■ ido Kiver ol the 



\ v ..i the Eastern Portion "i the Uinta 



■ i i. "f Geology. 



J Ian; Vol. Ill, Waahlngtoi eld work, 1871,1872, and 



