396 WALLACE W. ATWOOD AND KIRTLEY F, MATHER 
doing much more work in the same time; the domal movement 
which caused the renewal of down cutting during the Animas inter- 
glacial epoch may have been differential. Eastward from Huerto 
Creek two other canyons have been studied in which Bighorn 
glacial deposits have been recognized. 
In the Rio Grande Valley the deposits of Bighorn drift are found 
extending downstream about two miles below the Uinta terminal 
moraine and are banked against the eastern wall of the Rio Grande 
Valley a short distance up Lime Creek (see Fig. 3) and southward 
across the latter to the eastern wall of South River Valley. The 
conspicuous ridge southeast from Bristol Head on the floor of the 
Rio Grande Valley, which stopped the further advance of the Uinta 
ice at that point, is also capped with drift bowlders dropped upon 
it when it was overridden by the more extensive Bighorn ice. 
Downstream from the terminal moraine in this valley there are very 
notable outwash terraces of considerable extent with an elevation 
of nearly a hundred feet above the present stream channel. 
In the Uncompahgre Valley on the north slope of the range 
similar relations exist between the drift of the two later epochs of 
glaciation. On the extreme southeast corner of the Uncompahgre 
plateau near Dallas there is a glacial drift deposit capping the mesa. 
The bowlders range in size up to three feet in diameter and com- 
prise quartzite, sandstone, shale, tuff, and a variety of volcanic 
rocks. Some of the stones in this deposit are striated. In this 
deposit there are also large angular blocks of Dakota sandstone 
which were certainly not carried by water. They are at present in 
the midst of the bowlder deposit some hundred feet above the 
Dakota surface beneath them. The Dakota surface rises gently 
toward the west and forms the Uncompahgre plateau. The angular 
blocks could not have attained their present position by sliding or 
by stream action. They show no signs of stream wear. Up the 
Uncompahgre canyon the nearest Dakota outcrop is several miles 
distant, and the only agent that was capable of gathering, trans- 
porting, and depositing these blocks in their present position was 
glacial ice. This fact, combined with the variety of bowlders, their 
wear and striations, is adequate proof of the glacial origin of this 
