252 S. K. EMMONS — OROGRAPHU MOVEMENTS. 



Cambrian (Tonto beds). He also observed unconformities by erosion be- 

 tween, first, the upper Cambrian and Devonian ; second, Devonian and lower 

 Carboniferous; tliird, upper Carboniferous and lower Permian ; fourth, lower 

 Permian and upper Permian. A similar unconformity between Algonkian 

 and upper Cambrian was observed by him in Llano county, Texas. 



With regard to the Mr-o/oic, Dr. C. A. White* first made the following 

 suggestion, based on the finding of fresh-water Jurassic fossil.- in Colorado 

 and Wyoming: 



••In conclusion, I think it may be safely assumed that the great inland portion <>f 

 our continent was nol so permanently the seat of oceanic waters during the Mesozoic 

 times as has been generally supposed." 



I have already in a previous publication stated my belief that the Archaean 



areas in Colorado occupy the sites of mountain elevations that were uplifted 



above tin ean in post-Archsean time, and which in a more or less modified 



form have constituted hind areas ever since — that is, that in the times of the 

 greatest general depression of the region they were never so completely sub- 

 merged as to admit of continuous sedimentation over them, hut some mount- 

 ainous islands always existed, from the abrasion of which the sediments in 

 the adjoining seas were formed. This view is opposed to that held by the 

 late Dr. F. V. Haydeu, and also to that expressed by Major J. \V. Powell 

 in his geology of the eastern Uinta mountains, t both of which involve a 

 former complete arching over of the present crests of the mountains by the 

 strata now upturned along their flanks. It had, however, already been ad- 

 vocated by Mr. Clarence King J in his Systematic Geology, and by Dr. 

 A. ( '. Peale§ of the Hayden survey. 



The necessity of this view was impressed upon me by the structural con- 

 dition- of the heds resting on the eastern flanks of the Colorado range long 



before I had made any special studies of Colorado geology, and my subse- 



quenl field work there has only served to confirm its general correctness hy 

 the persistent evidence it ha- afforded of the littoral character of the sedi- 

 ment- along the assumed shore line.-, which changes rapidly as they are left ; 

 and by tin- character . if much of the organic life whose remain-, found in 

 these sediment-, indicate the vicinity of land areas, and .add to the impossi- 

 bility of explaining in any other way the peculiar stratigraphies! relatione 

 observed. 



In tracing the effects of orographic movements upon the cart h's cru-t . a 



marked contrast is noted between the region- of violent disturbance, gener- 

 ally mountainous areas, and those in which the strata -how little chai 

 from the horizontal position in which they weir originally deposited, which 



ii. 



rn I'ortion of the Uinta Mountains. Washington, 1876, p. 26 el 

 o.-ii, Paralli I Reports. vo\ I. i- 



A mi JOUI . V0\. Mil. 1>77, p. 1-1. 



