CGRG Bibliography of Canadian Geomorphology
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Author : Fisher, T. G
Date : 1996
Title : Sand-wedge and ventifact palaeoenvironmental indicators in Northwest Saskatchewan, Canada, 11ka to 9.9 ka BP.
Publication : Permafrost and Periglacial Processes
Issue : 7:
Page(s) : 391-408
Abstract
Exhumed sand wedges and ventifacts in the upper Churchill watershed of northwestern Saskatchewan indicate that aeolian and periglacial processes were dominate from c. 11 to c. 10.5 ka B.P. Nineteen sand wedges were identified that display vertical foliation, form polygonal nets, and penetrate either till, glaciolacustrine sediment or glaciofluvial diapiric sand. The sand wedges, and sand lenses within the till and glaciolacustrine sediments indicate permafrost aggradation after glaciation and lake drainage. Ventifacts that overlie the sand-wedges have preferred keel orientations that correlate with paleo-katabatic wind directions interpreted from stabilized parabolic dune orientations. Rat-tail lineaments on faceted surfaces of coarse-grained, granitic ventifacts also indicate paleo-wind flow direction. Strong and weakly developed lineaments on the same einkanter are explained by opposing >flow from prevailing winds, katabatic winds and anticylonic air flow from the adjacent Laurentide Ice Sheet, or by flow separation at the ventifact keel under unidirectional air flow. Two geomorphic surfaces are identified: (1) an older surface with sand wedges and weakly-developed ventifacts indicative of permafrost and brief aeolian activity; and (2) a lower and >younger segment of the former Lake Agassiz basin, without permafrost indicators and well-developed ventifacts. The upper surface developed in association with the Beaver River Moraine and glacial Lake Meadow-McMurray, is 11-10.5 ka BP in age, synchronous with the Younger Dryas cold period. The younger, lower surface was last modified beginning at 9.9 ka BP, when the northwest outlet of Lake Agassiz opened, was susceptible to greater aeolian reworking than the upper surface, and post-dates the Younger Dryas.
Bibliography of Canadian Geomorphology