Dr. Andrew Breckenridge
Friday, March 8th 2013, 3:30 PM, Weeks Hall – Room AB20
The intrabasin sediment record of the terminal phase of glacial Lake Agassiz-Ojibway
Much has been inferred regarding the drainage of glacial Lake Agassiz-Ojibway triggering the 8200 cal yr BP abrupt and global climatic cooling event, but the sediment record from the lake has contributed little information to understanding the timing and nature of drainage. Sediment cores from small lakes in Quebec and Ontario cover a portion of the former Lake Agassiz-Ojibway basin and provide a framework for understanding the terminal phase of this enormous glacial lake. The Lake Agassiz-Ojibway sediments are typically varved (annual couplets), and can be tied to a 2100 year record of ice margin retreat. The terminal sediments document a re-advance of the ice margin, a formerly unrecognized low stand, and a curious set of unusually thick varves that precede final drainage. Directly dating the terminal sediments has been challenging because this series of events created a complex sedimentary record.