C H AFTER I Y. 



DISPLACEMENTS. 



This district possesses unusual geological interest, because it is the 

 ground upon which displacements of the strata belonging to two differ- 

 ent orographic systems, those of the Uinta and Park Range Mountains, 

 meet and blend together. The district is so small, however, that it does 

 not embrace within' its limits a very considerable portion of either of 

 these mountain systems. Some of the minor flexures, or the vanishing 

 ends of more important ones, of the Park Eauge system, reach within 

 the eastern border of the district ;• but the greater part of the displace- 

 ments which the strata of the district have suffered belong to the Uinta 

 system. The relation of these displacements to the Park tiange system 

 are not clearly perceivable until they are traced beyond the eastern and 

 southern limits of the district here especially reported on ; therefore 

 the acconipanying map is made to embrace considerable additional space 

 beyond both its eastern and southern borders. The labors of the other 

 geologists of the survey have made known the orographic character- 

 istics of that portion of the Park Range tbat lies to the eastward and 

 southeastward of this district ; while those of Mr. King and Professor 

 Powell have made us acquainted with the structure of the Uinta Range. 

 The main displacements of these two systems being thus known, their 

 relation to and connection with each other and with accessory flexures 

 within this district may be easily traced upon the accompanying geolog- 

 ical map. 



The general plan of structure of the Uinta Uplift has been shown by 

 Mr. King and Professor Powell to consist essentially of one great flexure 

 of ui)lift, the axis of which is approximately east and west. The last- 

 named geologist has shown that this great Axial Uplift of the Uinta 

 Mountain system is distinctively characterized by an abruptflexureof the 

 strata, which is in some places a true fault, on each side of the great 

 fold, and that between the two abrupt side bendings the anticlinal bend- 

 ing of the strata is comparatively slight. This peculiar form of folding 

 of the flexures seems to be generic, so to speak, to the Uinta system, 

 since it is found to characterize certain of the principal accessory flexures 

 as well as the Yampa and Junction Mountain upthrusts, as will be ex- 

 plained in connection with their description on following pages. 



The Uinta system ends, as a mountain-range, upon and about mid- 

 length of the northern border of this district; but the Axial Flexure, 

 abruptly and very greatly diminished in scope, continues eastward from 

 the end of the mountain-range through the strata of the eastern portion 

 of the district and blends with certain flexures of the Park Range, as 

 will be explained on following pages. The accessory or subordinate 

 flexures or uplifts pertaining to the Uinta system, that lie within this 

 district, are of a peculiar and interesting character. The larger ones 

 lie approximately parallel with and closely adjacent to the Axial Uplift, 

 and constitute an integral portion of the eastern end of the mountain- 

 range; but the outlying smaller flexures are not only separate from the 

 first named, but also from each other. The smaller ones diminish iu 



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