164 GEOGRAPHIC DISTRIBUTION. 



region into the old Bitter Creek lake, while westward, from 'Richard's Peak 

 to the Green River, the present exposure of the strata is across the bed of 

 an ancient bay. 



West from Richard's Peak the plane of separation between the Bitter 

 Creek and Point of Rocks Groups is masked to a greater or less extent on 

 account of the exceeding friability of the lower beds of Bitter Ci'eek age ; 

 still careful examination reveals the fact that they are unconformable, and 

 this unconformity is very clearly exhibited at the eastern end of the mono- 

 clinal ridge, composed of the Upper Hogback Sandstone of the Point of 

 Rocks Group, near the foot of Richard's Peak, in an amphitheater of erosion 

 at the head of a dry gulch. 



Between the western end of the outcrop of Red Wall limestone on the 

 northwest end of the 0-wi-yu-kuts Plateau and the Po Canon district the 

 base of the Bitter Creek series is not seen, as it has been carried down by 

 the fault. On the north side of Diamond Peak the Bitter Creek beds are 

 lying horizontal, and, studying this mountain from that side, it would seem 

 to be composed of Bitter Creek beds, perhaps capped by beds of the Lower 

 Green River, but on climbing the mountain its summit is seen to be composed 

 of angular fragments of sandstones piled in an indiscriminate manner, the 

 age of which was not fully determined ; descending it on the south side 

 this same confusion is observed. Of what the principal mass of this peak 

 is composed I do not know. 



In the Po Canon district along the channel of Vermilion Creek and 

 many of its lateral tributaries, deep corrasion has produced many steep 

 escarpments of the Bitter Creek beds. Here we find the Point of Rocks 

 Group standingon edge, and near by, and separated from the former only 

 by narrow gulches, Bitter Creek beds of a horizon about midway in the 

 group are found lying hoiizontally; but in a few places lower beds of the 

 Bitter Creek series are turned up on edge with the Point of Rocks beds and 

 the middle beds of the Bitter Creek Group lie over their upturned and eroded 

 edges unconformably, and over some of the upper beds of the Point of Rocks 

 Group in like manner. Thus the middle beds of the Bitter Creek overlap 

 the lower beds, not because they were deposited over a broader area, but 

 because the lower beds in a part of their extent were exposed to erosion and 



