CGRG Bibliography of Canadian Geomorphology
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Author : Armstrong, J.E.
Date : 1981.
Title : Post-Vashon Wisconsin glaciation, Fraser Lowland, British Columbia, Canada
Publication : Geological Survey of Canada, Bulletin
Issue : 322
Page(s) : 34 p.
Abstract
The late Wisconsin Fraser Glaciation in southwestern British Columbia commenced on the mainland between 23,000 and 26,000 radiocarbon years ago and terminated about 11,000 radiocarbon years ago. It reached its climax during the Vashon Stade about 15,000 to 15,500 years ago when it extended south to 47°N. The Vashon ice was more than 1800 m thick in the Fraser Lowland, and the weight of the ice isostatically depressed the area at least 350 m and possibly 400 m or more. Withdrawal of Vashon ice was rapid, and from about 13,000 to 11,000 years BP most of the Fraser Lowland was invaded by the sea. During this interval the eastern part of the Fraser Lowland was occupied by a piedmont glacier or glaciers that at various times retreated, were stationary, or surged forward. The glacier or glaciers terminated in the sea for much of their history, probably in a manner similar to the glaciers of the Yakutat Bay area of Alaska. Throughout the period glaciomarine sediments were formed largely from dropstones and debris deposited into seafloor muds by floating pieces of ice (including bergs). During surges and standstilis drift was deposited in places above sea level and on the seafloor. The deposits laid down during the occupation of the sea comprise the Fort Langley Formation and the Capilano Sediments. Isostatic, eustatic and tectonic adjustments between the withdrawal of Vashon ice and withdrawal of the sea were not uniform for the whole area; however, at least two major submergences separated by unusually rapid emergences are indicated. The final withdrawal of the sea and disappearance of floating ice in the eastern part of the Fraser Lowland coincided with a final surge of piedmont ice. The deposits laid down during this last stade have been called Sumas. This ice apparently began to advance about 11,400 years ago when sea level was at least 50 m higher than at present. The date at which the ice disappeared is indefinite but was probably about 11,000 years ago, at which time the sea no longer occupied the area.
Bibliography of Canadian Geomorphology