OH A.1? TEH, IV. 



GEOGRAPHIC DISTRIBUTION OF THE GEOLOGICAL 

 FORMATIONS IN THE UINTA MOUNTAINS 



AND A DISTRICT OF COUNTRY ADJACENT THERETO. 



I propose to give a brief description of the geology of a part of the 

 Uinta Mountains and a district of country lying to the north, stretching 

 beyond the Union Pacific Railroad. The region is embraced within the 

 meridians of 108 30' and 109 52 7 .5 west longitude, and between the par- 

 allels of 40 15' and 41 40' north latitude. The Green River runs through 

 the middle of the district, having a general northerly and southerly course, 

 but from which it deflects in great curves. 



The Uinta Mountains are composed of elevated valleys, tables, and 

 peaks, the latter having a very irregular distribution, due to geological 

 structure. The axis of the range is the axis of a great flexure, having a 

 total displacement (or exhibiting an upheaval) of more than 30,000 feet, 

 This flexure terminates on the east in the little valley separating the Uinta 

 Mountains from Junction Mountain. The latter represents a short, abrupt, 

 anticlinal flexure, having a north and south axis The Uinta uplift lias 

 brought up all of the Mesozoic and Carboniferous Groups with the Uinta 

 Sandstone, and in one locality a still older group of rocks, viz, the Red 

 Creek Quartzite, is exposed. On the flanks of the range, both to the north 

 and south, Cenozoic groups are found. The grand Uinta displacement is 

 only a flexure in its general characteristics, as the down-throw on the north 

 side of the axis is, in some localities, in part produced by faulting; while 

 on the south side of the axis faults are found having throws on the north 

 side of the fissure. Thus the faults, instead of being a part of the general 



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