GLACIATION IN THE TELLURIDE QUADRANGLE 611 
has been worn away to a steep, irregular slope, affording lodgment 
for glacial débris in greater or less amounts, so that the whole 
eastern side of the valley from the stream to the eastern limit of 
the drift presents a steep, irregular surface, with but little change 
in slope at the elevation corresponding to the edge of the mesa 
farther north. Landsliding within this area has been noted by 
Cross;* such action is clearly responsible, in part, for the irregular, 
hummocky topography. 
On the west side of Lake Fork, the precipitous face of the sedi- 
mentary rocks outcropping below the edge of the mesa extends 
from the valley of the San Miguel River to about one mile south of 
the mouth of Turkey Creek. From this point southward for about 
two miles to the precipice formed by the diorite-monzonite intrusion 
northeast of Sunshine Mountain, the west slope of the valley, like 
the eastern, is rough, irregular, and steep, but without precipitous 
outcrops of rock in place. Unlike the eastern side, however, there 
is much less glacial débris evident, though rounded pebbles and 
bowlders, some of them striated, occur at frequent intervals. 
In cross-section, the valley of Lake Fork changes from a flat- 
bottomed, U-shaped form below the mouth of Turkey Creek, to a 
broadly open, V-shaped form two miles below the mouth of Howard 
Fork. In general, bed rock in the bottom of the valley is covered 
with rock waste in the form of alluvium, alluvial fans, or morainal 
deposits. The alluvial fans are numerous, but comparatively 
small. Distinct morainal deposits occur only at and a little above 
the mouth of Turkey Creek—a small recessional moraine, and a 
fragment of a lateral moraine, respectively. 
On the right side of the valley, opposite the junction of Howard 
Fork with the upper valley of Lake Fork, the drift is found in the 
form of a well-marked ridge 200 to 300 feet higher than at points 
above or below. This is clearly another instance of the effect of ice 
crowding up on the side of a valley opposite to the entrance of a 
tributary glacier. 
The maximum thickness of ice in the lower valley of Lake Fork 
was about 1,200 feet. 
' Telluride Folio, p. 11. 
