702 S. R. CAPPS AND E. D. K. LEFFINGWELL 



erosion since its deposition. In one or two instances the older drift 

 shows something of the lateral moraine ridge form, outside and 

 above the newer lateral moraines, but more often it occurs in thin 

 sheets, or merely as scattered bowlders. 



Possibility of a still earlier epoch oj glaciation. — Certain facts 

 point to the possibility of a still earlier epoch of glaciation in this 

 region. Two miles above Granite, on the east side of the Arkansas 

 River, bowlders were found 200 feet above the river, which seem to 

 have come from the Sawatch Mountains. These bowlders are 

 rather rare, and are much weathered, although of very resistant 

 granite.^ The position of these bowlders beyond the limits of the 

 ice of both well-determined epochs of glaciation points to a possible 



Fig. I. — A generalized section across the valley of the Arkansas, to illustrate the 

 conditions in the vicinity of Granite. 



a, terminal moraine of last epoch from a side valley, b, moraine of older drift; c, high terrace 

 lying against older drift; d, low terrace corresponding in age to a; e, Arkansas River; /, granite into 

 which river has cut a post-older glacial channel; g, bowlders from mountains on opposite side of valley, 

 which appear to be older than b. 



period of glaciation older than either, the drift of which has been 

 almost entirely removed. The evidence, however, does not seem to 

 be altogether conclusive. Some other bits of evidence of like import 

 are found at other points, but they have not been sufficiently devel- 

 oped to make their significance certain. 



The general relations of the two sheets of drift to each other, 

 and of both to the valley gravels, and to the scattered bowlders of 

 still greater age, are shown in Fig. i. 



TERRACES 



High terraces. — A most striking feature of this region is the great 

 display of terraces, seen at their best on the east side of the Arkansas 

 River, south of Leadville. These terraces rise with abrupt faces 



I These bowlders were found by Mr. L. F. Westgate, before the writers visited this 

 side of the valley. 



