510 ALLEN DAVID HOLE 
evidences of glacial action are noted at numerous places. The amount of 
morainal drift remaining in the quadrangle is observed to be relatively very 
small; the extent of grooved and polished surface of bare rocks, very large. 
From evidences of the latter kind within the quadrangle and from other 
evidences in adjacent quadrangles, the conclusion is reached that when glacia- 
tion was at its maximum the “greater part of the Needle Mountains area was 
buried beneath a thick mantle of ice and snow, from which only the higher 
summits projected.’ Only one stage of glaciation is recognized so far as 
observations made in this quadrangle are concerned. 
1905. Whitman Cross and Ernest Howe.—In the Silverton Folio numerous 
references are made to the evidences of glacial action at points in various parts 
of the quadrangle. As in the Needle Mountains Folio, the small amount of 
morainal material is noted, as well as the extensive development of cirques. 
The authors express the opinion that the amount of glacial erosion in the 
glacial epoch recognized in the Silverton quadrangle was slight. 
1906. T. C. Chamberlin and R. D. Salisbury.—In Vol. III of their Geology, 
Pp. 334-36, Chamberlin and Salisbury include the San Juan Mountains in the 
term ‘‘mountains of southwestern Colorado,” and, in addition to noting the 
former size and the altitude of the source of the glaciers in these mountains, 
state that the drift is referable to two or more glacial epochs. 
1906. Whitman Cross and Ernest Howe.—In a paper entitled “Glacial 
Phenomena of the San Juan Mountains, Colorado,” published in the Bulletin of 
the Geological Society of America, XVII, 251-74, Cross and Howe cite the 
evidences of glaciation at various points in the San Juan Mountains as noted 
above, and make mention of conclusive proof of two distinct stages of glaciation 
obtained especially in the Uncompahgre valley in the Ouray quadrangle in the 
summer of 1904. The chief differences noted with respect to the drift deposits 
of the two stages are (1) the slight modification due to weathering and erosion 
in the more recent deposits; relatively great changes in both these respects in 
the earlier; (2) the occurrence of the older drift ata greater distance from the 
mountains, capping ridges, and hills which had been formed by erosion before 
the last stage of glaciation; and (3) stratified deposits of gravel associated 
closely with the older deposits at relatively high elevations, and a series of 
gravel terraces intermediate in position between these and the earliest valley 
trains of the more recent stage. 
1907. Whitman Cross and Ernest Howe.—In the Ouray Folio, pp. 7 and 15, 
the authors present again substantially the same data and conclusions in regard 
to glaciation in the Ouray quadrangle as were included in their paper just 
referred to on glaciation in the San Juan Mountains. 
1909. Ernest Howe.—In Professional Paper 67, U.S. Geological Survey, Mr. 
Howe refers briefly in a number of places to the evidences of glaciation in the 
San Juan Mountains, but records no observations not included in publications 
already named above. 
rgt0. Stephen R. Capps, Jr—In the Journal of Geology, XVIII, 370 and 
