Physiography and Glaciation

by valley walls. The north side of the valley rises well above the highest ridge
of the complex, but on the south side the valley wall attains a comparable eleva-
tion about 2 miles south of the most southerly esker ridge, and then only as the
result of a gradual rise from the base of the esker complex toward Mount Swan-
nell. Because of the lack of a confining bedrock wall on the south side, it can only
be concluded that, at the time of formation of this esker complex, ice formed
the southern valley wall.

The origin of this esker complex is not clear but certain features suggest
some answers. The complex lies along one of the major meltwater channels and,
as it is partly in this eroded channel, it must have been formed during the active
period of meltwater run-off or later. Formation at a later date is unlikely because
the presence of abundant ice in the vicinity is indicated by the many kettles and
the probability of confining ice. It is suggested that this complex represents an
ice jam that formed along the meltwater channel, the spaces between the ice-blocks
being filled with sand and gravel. This feature was unquestionably the result of a
local condition as it has no extension or counterpart elsewhere in the area.

Crevasse Fillings

Near the western boundary of the area, 6 miles southeast of Uduk Lake, a
group of ridges are believed to be crevasse fillings. These are ridges which, al-
though possessing the cross-sectional appearance of an esker, lack the character-
istic sinuous shape. They are straight ridges with a slightly uneven top, composed
of coarse, unsorted, and unstratified material giving the impression of a coarse
till from which the fines have been washed. The arrangement in no way resembles
the usual sorted and stratified material of an esker. These ridges are believed to
have resulted from the filling of crevasses in a stagnant block of ice, the material
being washed into the crevasses without further sorting or reworking. They occur
in an area topographically suited to the existence of such a stagnant mass of ice,
and their haphazard arrangement—some at right angles to one another—precludes
the possibility of their being formed by moving ice.

Cirques

Cirques occur in the Fawnie and Nechako Ranges but, as they have been
overridden by glacier ice, they must have formed before the last glaciation. Only
in the Fawnie range is there evidence of renewed activity since that time, and
even this does not seem to have been extensive. There is no active glacier ice
in the area today.

Meltwater Channels

Two types of meltwater channels are shown on the map: (1) large channels
with well-formed terraces; and (2) small or abandoned channels. The small chan-
nels were formed mainly by streams following the lateral margins of glaciers or

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