CGRG Bibliography of Canadian Geomorphology
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Author : Broster, B.E.; and Stumpf, A.J.
Date : 1998
Title : Landward shifts of Late Wisconsinan ice growth centres and reversals in ice flow directions along the Atlantic and Pacific Coasts of Canada.
Publication : AMQUA 1998 - American Quaternary Association Program and Abstracts of the 15th Biennial Meeting, Puerto Vellarta, Mexico, 5-7 September 1998.
Issue :
Page(s) : 77.
Abstract
In the Northern Hemisphere, the extent of glacial ice sheets during the Late Wisconsinan were a product of changes in wind patterns, their intensity, and centres of precipitation. These conditions were major variables in determining the location of ice sheet centres, advance or retreat of glaciers, and the direction of ice flow. Examination of spatial patterns of glacial landforms, glacial erosion (e.g., striae), and the dispersal of distinct erratics, support an interpretation of three major phases of ice growth at inland and coastal areas along both the Atlantic and Pacific coasts of Canada. These phases of ice-growth were accompanied by reversals in ice flow direction resulting from seaward to landward to seaward shifts in the major centres of ice accumulation. In west-central British Columbia, Alpine locations in coastal areas, and inland from the Pacific Ocean, experienced an early flow phase (1) during which ice collected at high elevations and grew radially outward from Alpine centres, flowed into and along valleys and coalesced into large ice sheets. This initial phase was followed by a maximum flow phase (2) representing the development of a major ice dome 250 km inland from the coast and reversals in flow directions. During the retreat phase (3) ice sheets thinned and were again confined to topographic valleys. Evidence of this last phase is well preserved by striae and landforms which obscure evidence of earlier flows that occurred in different directions. In the Maritime Provinces of eastern Canada, areas along the Atlantic coast also experienced early ice-growth (1) and radial flow from subalpine centres. These initial flow events were localized and controlled by topographic relief. With the exception of rare occurrences of dispersed erratics and striae in directions different to the maximum phase, evidence for this event has been largely erased by later ice events. In southern New Brunswick and in Nova Scotia, a dominant flow event occurred when ice flowed across the region, eastward and southward from areas in Maine, U.S.A. (phase 2; maximum phase), from locations approximately 200 km further inland. During the last phase of glacial activity (3) ice flow directions were controlled by topography as regional ice masses retreated and radial flow from subalpine centres returned as the last ice flow event in coastal areas. It is likely that the three phases of shifting coastal ice centres were simultaneous occurrences in response to worldwide changes in atmospheric and oceanic circulation patterns.
Bibliography of Canadian Geomorphology