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The moraines are composed of materials deposited at the ends of the
valley glaciers. Their surface is usually characterized by irregular hillocks
and undrained basins; and the materials consist in part of stratified sands
and gravels, in part of boulder clay, and in places, for example opposite
the mouth of Devils Lake creek, mostly of angular blocks of the country
rock.

Glacial outwash gravels deposited by streams coming from the melting
ice in the upper parts of the valleys occur in considerable quantities as
valley filling. The glacial gravels in the beds of the streams frequently
show imbricated structure (Plate V A), that is, the pebbles dip upstream
and overlap downstream and have their long axes in the direction of the
current. Glacial gravels also occur in places, as opposite the mouth of
Little valley and along the west side of the upper part of the valley, in the
form of irregular hills or kames and as long, winding ridges or eskers. The
gravels are in many places coarse and in places are overlain and underlain
by boulder clay.

The stratified combination of silt and clay, usually recognized in
drilling by its uniform character and almost complete freedom from stones,
in many cases forms a considerable part of the valley filling, and in places,
as on the east side of Antler creek opposite the head of Guyet creek, forms
part of the filling of a tributary valley as much as 300 feet above the
bottom of the main creek. The silt and clay combination varies somewhat
in character in different parts of the area. In places it is a fairly stiff and
nearly impervious clay, but for the most part it is composed of fine sand and
silt glacial flour—which is readily permeable by water, hence the name
“slum.” The glacial gravels, especially the coarse gravels and occasionally
the fine gravels, referred to by the miners as “‘chicken-feed,” contain con-
siderable quantities of it. The silt shows a fairly regular banding due to
an alternation of fine and coarse layers, but no evidence of any definite
seasonal banding was noted. It is overlain and underlain in places by
boulder clay and in a few places, as at Hamshaw’s hydraulic pit on lower
Summit creek, is partly cemented. “Dry slum” or compressed and partly
cemented glacial silt is reported to occur on a few of the creeks below
water-level. The silt, judging by its even stratification and wide extent,
was deposited in a series of lakes formed during Pleistocene time through
the blocking of the valley drainage by uneven deposition of drift or-—in the
case of the northward drainage—by an advance of glaciers from Cariboo
mountains. It is possible, also, that lakes were formed as the result of
uneven uplift or depression of parts of the region, but this does not seem
very probable as cutting down of the outlet would probably take place as
rapidly as the area was uplifted. The oceurrence of stratified silts at heights
of several hundred feet above the present valley bottoms shows that they
were formerly much more extensive than at present, and the fact that they
are overlain at these high levels by boulder clay shows that they were
deposited during an early stage of valley glaciation and were much eroded
either during a time of temporary retreat of the glaciers or as a result of
readvance of the ice. The stratified deposits form a large part of the
glacial drift of the area and indicate the great volumes of flood-water
which must have existed during parts of Pleistocene time—a remarkable