103

glacial drift in the valley, for the materials immediately above the rock are
quite fresh and unweathered. On the other hand, if the weathering has
taken place before the deposition of the glacial drift, it is difficult to under-
stand how it was that the stream in cutting down its valley did not entirely
remove the soft clay. Slow percolation of water along the bedrock in the
bottom of the valley—for the stream has a fairly high gradient—during
Pleistocene and Recent times, although there could have been little under-
ground flow of water during the times of occupancy of the region by the
ice-sheet and valley glaciers, may have caused disintegration of the rock.

Scale of feet
To) 1/000

Contour jnterval 4O reet <= Ea
Fecent alluvium

Bedrock outcrop

g
aS)
:
<<
5
K
NS

Geological boundary

tYydraulic pit

Geological Survey, Canedea.

Figure 16. Stouts-Lowhee divide, Cariboo district.

If so it would be expected that the bedrock would be disintegrated generally
in the old buried channels of high gradient streams, but this is not the case.
There is a barrier of hard rock across the valley below the occurrence and
the rock above is soft and easily disintegrated. It may be that the residual
clay in the stream bed is all that remains of a deeply weathered zone formed
preglacially and mostly cut away by stream erosion. There are numerous
angular fragments and large blocks of bedrock (slide rock) in the bottom of
the channel, which evidently slid in from the sides of the channel before it
was filled with glacial drift and are, therefore, preglacial or interglacial in
age. There is no evidence that the bedrock valley was formed after a first
advance and retreat of the ice, and the hanging character of the valley at its