162 GEOGRAPHIC DISTRIBUTION. 



case of the Brown's Park Group and the Bishop Mountain Conglomerate. 

 A small strip of country on the south side of the mountains has been given 

 a Tertiary color on the map for the purpose of presenting an interesting 

 fact in the relation of the groups of that region ; but this is only the border 

 of a broad area through which Ceriozoic formations are distributed, and to 

 discuss this border with clearness it is necessary to enter into a consideration 

 of the whole area, which can be done much better when we have the map 

 of that country before us. 



In the Uinta and White River basins, south of the Uinta Mountains, 

 where these Tertiaries have a great development, the lower formations of 

 this Age have been pretty thoroughly worked out, but there are higher beds 

 not so well understood. 



I now turn to a consideration of the country north of the Uinta Moun- 

 tains. 



BITTER CREEK GROUP. 



Here the Bitter Creek beds have an extensive exposure on the flank of 

 the Uinta upheaval and on either flank of the Aspen Mountain uplift. 



In the Flaming Gorge district, west of the Green River, the beds of 

 this group rapidly attenuate until they disappear, and here their lithologic 

 character is changed, as the fine grained friable sandstones are replaced by 

 conglomerates ; and as the beds here are dipping at a great angle to the 

 north, so that their upturned edges are well exposed, the harder conglomer- 

 ates are seen to stand in high ledges and walls. Eastward from the Green 

 River the beds rapidly thicken until, at Richard's Peak and Quien Hornet 

 Mountain, a section of more than 5,000 feet is presented, and here at the 

 base we have a great development of conglomerates. Richard's Peak itself 

 is a monoclinal ridge of this conglomerate. 



The disappearance of these beds by attenuation on the west side of the 

 Green River and their increase above the normal thickness east of that 

 stream, together with the change in their lithologic constitution, leads us to 

 infer that we here have the beds exposed near the old shore line that was 

 established by the upheaval of the Uinta Mountain region. Conglomerates 

 are found at the base of the group in many places on the north side of the 

 Uintas, and I suppose the conglomerates on the west side of the Green 



