Advance of alpine glaciers during final retreat of the Cordilleran ice sheet in the Finlay River area, northern British Columbia, Canada |
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Authors: | Thomas R Lakeman John J Clague |
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Institution: | a Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6 b Geography Program and Natural Resources and Environmental Studies Institute, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia, Canada V2N 4Z9 |
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Abstract: | Sharp-crested moraines, up to 120 m high and 9 km beyond Little Ice Age glacier limits, record a late Pleistocene advance of alpine glaciers in the Finlay River area in northern British Columbia. The moraines are regional in extent and record climatic deterioration near the end of the last glaciation. Several lateral moraines are crosscut by meltwater channels that record downwasting of trunk valley ice of the northern Cordilleran ice sheet. Other lateral moraines merge with ice-stagnation deposits in trunk valleys. These relationships confirm the interaction of advancing alpine glaciers with the regionally decaying Cordilleran ice sheet and verify a late-glacial age for the moraines. Sediment cores were collected from eight lakes dammed by the moraines. Two tephras occur in basal sediments of five lakes, demonstrating that the moraines are the same age. Plant macrofossils from sediment cores provide a minimum limiting age of 10,550-10,250 cal yr BP (9230 ± 50 14C yr BP) for abandonment of the moraines. The advance that left the moraines may date to the Younger Dryas period. The Finlay moraines demonstrate that the timing and style of regional deglaciation was important in determining the magnitude of late-glacial glacier advances. |
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Keywords: | Cordilleran ice sheet Fraser glaciation Younger Dryas late-glacial British Columbia Finlay River |
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