PLEISTOCENE HISTORY OF SAN JUAN MOUNTAINS 403 
these localities these deposits suggest by their physical and litho- 
logical heterogeneity, by their lack of assortment, subangular 
stones, by huge bowlders up to 25 feet in diameter, and topographic 
situation that they are of glacial origin. At one locality over an 
area of about one square mile there is an old morainic topography, 
and on Horsefly Peak, West and South Baldy striated stones were 
found. The striae were all found on surfaces that had not been 
exposed. Most of the striated stones found were small, but on the 
underside of a huge bowlder on South Baldy, Professor R. D. 
Salisbury found a remarkable example of a smoothed, polished, 
and striated surface. There is no question but that the material is 
of glacial origin. 
Landslides have frequently affected the disposition of these 
earliest glacial deposits, but this later topography can be easily 
distinguished from the morainic topography. Scattered over the 
mesa surface to the east and northeast of Horsefly Peak there are 
several small deposits of bowlders which point to a former much 
more widespread deposit of glacial drift. 
On the eastern side of the Uncompahgre Valley between Cow 
Creek and Cimmarron Ridge there are extensive bowlder deposits 
which have now been referred to the San Juan epoch of glaciation. 
The portion of this deposit which lies within the Ouray quadrangle 
has been mapped in the Ouray folio as ‘earlier moraine” and the 
same formation extends some distance north of that quadrangle. 
The deposit is similar to that at Horsefly Peak as far as the size 
and assortment of the bowlders is concerned, although no quartzites 
and very few granites were observed there. In one locality on 
Burro Creek a good section of the bowlder-gravels is exposed and 
here it is seen that the bowlders are imbedded in a typical 
bowlder-till. 
The components, arrangement, and topographic relations of 
these several deposits on the north side of the range show that they 
are remnants of a once more widespread formation which covered a 
large area in this vicinity. The size and distribution of the 
materials composing the detritus, the fact that these huge bowlders 
have been transported many miles, and the glacial markings which 
some of them bear, point unmistakably to their glacial origin. 
