Geology Reference
In-Depth Information
Figure 2.3. Vertical air photo of part of northwestern Banks Island showing the morainal contact
between Late-Wisconsinan ice lobe in McClure Strait and never-glaciated Beaufort Plain. A series
of meandering meltwater channels, some plugged by fl ow till, parallel the coastal moraine. A spill-
way channel, formed by overfl ow from a glacially-dammed lake to the east, is shown incised within
the fl uvially-dissected surface of the Beaufort Plain. Air Photograph A 17381-137, National Air
Photo Library © 1996. Produced under licence from Her Majesty the Queen in Right of Canada,
with permisssion from Natural Resources Canada.
In this regional context, it is informative to describe the landscape. J. G. Fyles, the
Canadian Quaternary geologist, was the fi rst to study the geomorphology. He desceribed
the Beaufort Plain in these terms:
Northwestern Banks Island is a fl uvial plain, . . . underlain by thick gravels and sands. The
Beaufort Plain rises gradually from sea level at the west coast to an altitude of about 800
feet at its eastern boundary. It is drained by more or less parallel, west-fl owing, consequent
major rivers and by dendritically arranged tributary streams . . . River valleys are cut a few
feet to 500 feet below the plain surface. The larger valleys . . . have fl at fl oors and steep
walls. Some are asymmetrical in cross section, with a steep undercut north wall. Many of
the rivers are strikingly braided . . . Large abandoned valleys just south of the morainal
belt appear to be ancient, west-draining courses of the rivers that now fl ow to the north
coast . . . The valleys are separated by broad areas of fl at plain, and dissection has only
locally progressed beyond early youth. The plain surface is remarkably uniform and com-
pletely free of lakes . . . The plain has not yielded clear evidence of having been overridden
by glacial ice. ( Fyles, 1962, in Thorsteinsson and Tozer, 1962, pp. 15-17 ).
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