146 GEOGRAPHIC DISTRIBUTION. 



THE CARBONIFEROUS GROUPS. 

 CERTAIN GEOGRAPHIC DISTRICTS DESIGNATED. 



In describing the geographic distribution of the Carboniferous and 

 Mesozoic Groups it will be found convenient to designate under general 

 terms certain districts of country, as follows : 



FLAMING GORGE DISTRICT. . 



There is a belt of country, extending from Bruce Mountain westward 

 to the border of the map, where most of the Carboniferous and Mesozoic 

 arid certain of the Cenozoic formations are turned up on edge, so that in a 

 limited area nearly all these groups can be studied. The Green Eiver enters 

 the Uinta Mountains by a flaring, brilliant, vermilion gorge, a conspicuous 

 and well known locality, to which, several years ago, I gave the name 

 Flaming Gorge, and this name has been generally accepted. I shall call 

 this the Flaming Gorge district. 



PO CANON DISTRICT. 



East of Bruce Mountain, for many miles, the Uinta displacement is 

 chiefly by faulting, and with slight exception the Carboniferous and Meso- 

 zoic Groups have been carried down and are concealed. But southeast 

 from Diamond Peak the displacement changes again into a flexure, and once 

 more the Carboniferous and Meaozoic Groups are found turned up on edge. 

 This region is at the eastern end of the 0-wi-yu-kuts Plateau, the plateau 

 itself culminating in a high monoclinal ridge at its eastern extremity, and 

 the plateau is bounded on this side by a deep monoclinal canon which divides 

 it from a region of Mesozoic and higher Carboniferous hogbacks. This 

 canon is also a well marked and well known geographic feature. Some 

 years ago I gave it the name Po Canon, and that name has been accepted 

 throughout the country. This I shall call the Po Canon district. 



YAMPA DISTRICT. 



In the Yampa Plateau by a series of flexures and faults the whole Meso- 

 zoic and Carboniferous series are brought to view. East from the Yampa 

 Plateiiu there is a simple anticlinal upheaval where all these groups are 



