PP51C-2295
Preliminary Cosmogenic Surface Exposure Ages on Laurentide Ice-sheet Retreat and Opening of the Eastern Lake Agassiz Outlets
Friday, 18 December 2015
Poster Hall (Moscone South)
David Leydet1, Anders E Carlson2, Gaylen Sinclair3, James T Teller4, Andrew J. Breckenridge5, Marc W Caffee6 and Aaron M Barth2, (1)Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States, (2)Oregon State University, Corvallis, OR, United States, (3)COAS, Corvallis, OR, United States, (4)University of Manitoba, Winnipeg, MB, Canada, (5)University of Wisconsin-Superior, Superior, WI, United States, (6)Purdue University, Department of Physics and Astronomy, West Lafayette, IN, United States
Abstract:
The chronology for the eastern outlets of glacial Lake Agassiz holds important consequences for the cause of Younger Dryas cold event during the last deglaciation. Eastward routing of Lake Agassiz runoff was originally hypothesized to have triggered the Younger Dryas. However, currently the chronology of the eastern outlets is only constrained by minimum-limiting radiocarbon ages that could suggest the eastern outlets were still ice covered at the start of the Younger Dryas at ~12.9 ka BP, requiring a different forcing of this abrupt climate event. Nevertheless, the oldest radiocarbon ages are still consistent with an ice-free eastern outlet at the start of the Younger Dryas. Here we will present preliminary 10-Be cosmogenic surface exposure ages from the North Lake, Flat Rock Lake, glacial Lake Kaministiquia, and Lake Nipigon outlets located near Thunder Bay, Ontario. These ages will date the timing of the deglaciation of the Laurentide ice sheet in the eastern outlet region of glacial Lake Agassiz. This will provide an important constraint for the hypothesized freshwater forcing of the cause of Younger Dryas cold event.
