524 ALLEN DAVID HOLE 
the upper part small ponds occur. Two rock streams occur at from 
12,000 to 12,500 feet in elevation. Talus slopes and precipitous 
cliffs beyond the talus mark the boundary of the cirquelike valley. 
The tributary valley from the northwest has a bottom with 
rounded ledges; but the stream is in a deep canyon part of the 
way, first at a point more than halfway up the valley and again 
near its mouth. No striated rock surfaces were observed. In 
general, the slope of the bottom of the valley is very steep, and the 
sides are made up of long talus slopes with precipitous faces above 
them. At the upper end of the valley is an unusually fine example 
of a rock stream, which extends more than a quarter of a mile from 
the precipice which forms the head of the valley. In the lower part 
of the valley of this tributary on the west side, at an elevation of 
about 11,200 feet, is a small area of uneven, hummocky ground 
inclosing a pond 30 or 40 feet in diameter; this uneven topography 
is evidently due to landsliding. 
At an elevation of about 10,300 feet, a precipitous cliff of the 
Telluride formation causes falls 100 feet or more in height in the 
streams both from the head of the main valley and from the branch 
coming from the northwest. Below the falls and down to about 
9,900 feet in elevation there is much fragmental material in the 
stream bed, rock in place being visible only occasionally. At about 
9,900 feet, the stream bed lies in a canyon cut in Dakota sandstone. 
Again at from 9,200 to 9,400 feet in elevation there are many 
bowlders along the stream. At most other places, the stream has 
its channel in bed rock or nearly so. 
Park Basin is very similar in its.main features to the valley 
tributary to Mill Creek from the northwest. It has a steep gradient 
where it joins the main valley, a grade less steep from 11,000 to 
12,000 feet in elevation, steep talus slopes, and precipitous cliffs 
beyond the talus. 
On the west side of the main stream at an elevation of from 
10,000 to 10,200 feet, is an area of irregular, hummocky topography, 
in which are some small undrained basins. The material here is 
clay, with pebbles and bowlders, some of which are rounded. This 
area clearly lies within the limits of glaciation for this valley, but 
the uneven topography is no doubt due largely to landsliding. 
