Testing Alternative Models of Laurentide Icesheet Dynamics Using Cosmogenic Nuclide Exposure Dating, Cumberland Sound Area, Southern Baffin Island, Arctic Canada

Investigator: P. Thompson Davis pdavis@bentley.edu  (Principal Investigator current)

Abstract

ABSTRACT OPP-9807066 Davis Steig

This is a collaborative study is by scientists at Bentley College and Universities of Vermont and Colorado on the Wisconsinan glacial history of Cumberland Sound on southern Baffin Island to gain a better understanding of the Laurentide ice sheet.  Scientific understanding of the Climatic and glacial history of the Cumberland Sound is currently undergoing a major revision but significant geochronological uncertainties still remain.  Cosmogenic nuclide exposure ages for 139 samples from moraines and bedrock surfaces sampled along the Pangnirtung Pass and Fjord suggest that the glacier advanced from the interior of Cumberland Peninsula between 25-10 million years ago (ka) and then rapidly retreated 10-7 ka to near present-day ice margins.  These date appear to be in conflict with pre-late Wisconsinan radiocarbon ages from basal lake sediments.  Preliminary cosmogenic nuclide data for a limited number of samples suggest similar timing for glaciation of the outer part of Cumberland Sound, but appear to conflict with younger radiocarbon results from marine sediment cores.  Additional previously collected cosmogenic nuclide samples will be processed and analyzed to further investigate these discrepancies, with the goal of improving the chronology of glaciation in the Cumberland Sound region.  Discordant 26 Al/10Be exposure ages from upland areas surrounding the Pangnirtung Fjord, indicate these areas have a long and complex burial and exposure history, with the likely presence of cold-based ice on the uplands while warm-based ice filled the Pangnirtung Fjord and Cumberland Sound during the late Wisconsinan.  Analyses of these additional samples will more precisely determine the vertical extent of the late Wisconsinan in the Pangnirtung Fjord area and test whether similar glaciological conditions existed further to the southeast.