258 S. I'. EMMONS — OROGRAPHK MOVEMENTS. 



and slates, resting unconformably on the granite body of Little Cottonwood 

 (•anon and upon a Beries of schists which form the western flank of this body . 

 These were classed by the Fortieth Parallel geologists as Cambrian, while the 

 schists were assumed on lithological grounds to correspond with the Red < 'nek 

 quartzites of the Uinta mountains. In my study of the Uinta range in 1*71 

 I found only upper Carboniferous beds, as determined by their fauna and 

 their lithological correspondence with already defined horizons in the adjoin- 

 ing Wasatch range, and considered thai the great thickness of quartzites, 

 conglomerates and shales underlying them in apparent conformity and form- 

 ing the core of the range belonged to the silicious or middle member of the 

 Carboniferous. Powell, however, haying found, in the canon of the Green 

 river at the eastern end of the mountains, an unconformity by erosion betwe< a 

 the upper and lower portion of these sandstones, I assumed that the lower 

 portion, the Uinta sandstones, must correspond to the Cambrian quartzites 

 of Big Cottonwood canon.* In his later examination of the Big Cotton - 

 wood section, Mr. Walcott found lower and middle Cambrian faunas in the 

 upper 2,000 feet of the Big Cottonwood quartzites, and classed the lower 

 10,000 feel as Algonkian. According to this classification the Uinta sand- 

 stones would probably be of Algonkian age, but of a later period than the 

 Red ( Ireek quartzites. 



In the Grand (anon region, throughout the Rocky Mountain region, in 

 the Black Hills of Dakota and, so far as known, in Texas, New Mexico, 

 and Arizona, only upper Cambrian beds were deposited. It must therefore 

 be assumed that during early and middle Cambrian times, while the Big 

 Cottonwood beds were being deposited, these regions were elevated above 

 the ocean; but that a progressive subsidence was going on which initiated a 



cycle of deposition in the Rocky M tain region extending from upper 



Cambrian to middle Carboniferous time. 



The beds deposited during this interval are of extremely limited thickness 

 ;i- compared with that of corresponding horizons in Utah and Nevada, no 

 exposures thus far examined showing as much as one-tenth of the thickness 

 represented in the Wasatch section. Their fauna also has thus far proved 

 to be extremely meager. A fairly uniform succession in character of sedi- 

 ii m -ii t is observed throughout the region, the Cambrian commencing with a 

 fine basal conglomerate indicative of an advancing shore-line, followed by 

 varying thicknesses of sandstones, which pass upward through calcareous 

 sandstones and shales into silicious limestones in the Silurian and pure dolo- 

 mites or limestones in the lower < ail iferous, with a somewhal abrupt pas- 



e into clays and sandstones above, showing evidence of shallow-water 

 deposition. 



Such palseontological evidence as has Keen obtained prove- the existence 



Poi i leth Parallel Vol II, p. 100 



