CGRG Bibliography of Canadian Geomorphology
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Author : Carlson, A.E.; and Clark, P.
Date : 2003.
Title : Using river geochemistry as a tracer of continental routing during the last deglaciation.
Publication : Joint Annual Meeting of the Canadian Quaternary Association and the Canadian Geomorphology Research Group. Halifax, Nova Scotia, June 8-12, 2003.
Issue :
Page(s) :
Abstract
North American freshwater routing played an important role in causing changes in ocean circulation and abrupt climate change during the last deglaciation. However, paleo-proxies of these events are inconclusive and difficult to interpret. To circumvent the problems associated with multiple controls on a single proxy, we model changes in the geochemistry of the St. Lawrence River and Hudson Strait assuming that bedrock is the dominant control on river geochemistry. Our geochemistry model calculates changes in cations during the last deglaciation based on changes in runoff (ablation + precipitation - evaporation) and reorganization of cryo-hydrologic basins due to changes in Laurentide Ice Sheet (LIS) margins and ice divides. The geochemical signal is put into a simple estuary box model to predict changes in estuary chemistry through time. In the St. Lawrence model, there is a large increase in Sr and Li just prior to the Younger Dryas (YD) followed by an abrupt decrease at the termination of the YD. The increase in Sr is attributed to drainage across Paleozoic carbonates of the Great Lakes Region while the Li increase is likely sourced from the Cretaceous and Tertiary terrestrial rocks of the Western Canadian Plains. Their decrease at the end of the YD may be due to a readvance of the LIS diverting these basins from the St. Lawrence. In Hudson Strait, the Sr signal does not vary greatly because of the close proximity of Paleozoic carbonates. However, Li increases rapidly just prior to the 8.2 ka cold event due to a shift in drainage of the Western Canadian Plains from the St. Lawrence River to Hudson Strait. We hypothesize that such geochemical tracers will be preserved in foraminiferal tests, thus providing a proxy of freshwater routing by the LIS.
Bibliography of Canadian Geomorphology