250 S. I. I.MM<»\ OKOGRAPHK MOVEME2* 



1. The elevation of the Rocky Mountains, as we now see them in Colorado, is 

 the result of an elevation commencing in early Tertiary time and continuing through 

 the period, i I aps at tl of the Lignitic and after the deposition of 



M i ene strata. " 



This was written at the time when Dr. Peale, in accordance with the views 

 of hi- chief, Dr. V. V. Hay den, regarded the Lignitic Laramie) as of Ter 

 tiary a§ 



Black Hills Survey. -In the Black Hills of Dakota* Newton and Jenney 

 recognized two distinct series of crystalline schists, with some faint evidence 

 of unconformity between them. Thegreat breaks determined by them were 

 between these crystalline schists and the Cambrian (Potsdam sandstom 

 More recently W. 0. Crosbyt has found evidence of an uplift of the region 

 at the close of the marine Jurassic. 



orado Plateau Region. Gilbert, in his Geology of the Henry Moun- 

 tains,^ remark- on the physical break at the close of the Cretat as, and 



notes three unconformities by erosion, one at the close of the Carboniferous 

 arid two within the -eric- called by him Jura-Trias. 



In the preface to Captain Dutton's work on the High Plateau-. J Major 

 Powell states with regard to the Plateau province — 



• A marked unconformity exists between the Silurian and Devonian rocks; another 

 between the Devonian and Carboniferous; another, but not so well marked, between 

 the Carboniferous and Mesozoic, and lastly an unconformity between Cretaceous and 

 Ti rtiary is usually well defined." 



In the region of the Grand Cafion of the t lolorado, Captain Dutton notes, 

 besides the universal unconformities at the close of the A.rchsean and the 

 Cretaceous, that the Carboniferous rests unconformably upon the Silurian 

 or Devonian, as the case may be. He also timls unconformities by ero- 

 sion between Carboniferous and Permian, between Permian and Trias, be- 

 tween Trias and Jura, and between Jura and Cretaceous. He considers 

 that the Carboniferous was deposited in deep waters, but that during the 

 Permian and Mesozoic, shallow-water conditions prevailed; also that the 

 Eocene was a fresh-water deposit, that a slow elevation began about the 

 middle of this epoch, and that the Colorado river commenced as a drains 

 channel of the Eocene lake in early Tertiary times, gradually eating its way 

 hack until it reached its presenl extension, and cutting across an} elevations 

 produced during subsequent movements as they rose without changing it- 

 already determined com 



I find it difficult to reconcile my own observations in the Uinta mountain 



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field 



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