CGRG Bibliography of Canadian Geomorphology
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Author : Breckenridge, A.; Johnson, T.C.; and Beske-Diehl, S
Date : 2003.
Title : Lake Agassiz influx through Lake Superior Between 10.6 to 9.0 CAL KA (9.4 to 8.0 14C KA).
Publication : Joint Annual Meeting of the Canadian Quaternary Association and the Canadian Geomorphology Research Group. Halifax, Nova Scotia, June 8-12, 2003.
Issue :
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Abstract
Glaciolacustrine varves accumulated in Lake Superior following the retreat of the Laurentide Ice Sheet (LIS) from the basin. LIS retreat eventually opened eastern Lake Agassiz outlets so that the varves reflect the combined impacts of sediment-laden meltwater and Lake Agassiz discharge. Multiple varve chronologies suggest eastern Lake Agassiz outlets opened no earlier than 10.6 cal ka (9.4 14C ka) and perhaps as late as 10.4 cal ka (9.2 14C ka). Lake Agassiz and LIS meltwater flowed through Lake Superior until 9.2 cal ka (8.2 14C ka), thereafter most of the flow was abruptly diverted eastward into Lake Ojibway. By 9.0 cal ka (8.0 14C ka), all Agassiz and LIS meltwater circumvented Lake Superior. A pilot study of trace metal concentrations suggests that there were multiple episodes of increased Lake Agassiz influx between 9.25 and 9.4 cal ka (8.2-8.4 14C ka), which were followed by a 40-yr period of extreme sediment discharge into Superior. These results are consistent with oxygen isotope records from Lakes Michigan and Huron, but it remains unclear why Agassiz influx would have increased between 9.25 and 9.4 cal ka and if there is a direct connection between Lake Agassiz draw-down and the catastrophic release of stored LIS meltwater. Future work will reconstruct an annually resolvable record of Lake Agassiz flood events via trace metals measurements for the length of the varve record.
Bibliography of Canadian Geomorphology