Cosmogenic exposure dating in arctic glacial landscapes: implications for the glacial history of northeastern Baffin Island, Arctic Canada

Canadian Journal of Earth Sciences - Tập 42 Số 1 - Trang 67-84 - 2005
Jason P. Briner1, Gifford H. Miller1, P. Thompson Davis2, Robert C. Finkel3
1INSTAAR and Dept. of Geological Sciences, University of Colorado, Boulder, CO 80303, USA.
2Department of Natural Sciences, Bentley College, Waltham, MA 02454, USA
3Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA

Tóm tắt

Cosmogenic exposure dating and detailed glacial-terrain mapping from the Clyde Foreland, Baffin Island, Arctic Canada, reveal new information about the extent and dynamics of the northeastern sector of the Laurentide Ice Sheet (LIS) during the last glacial maximum (LGM). The Clyde Foreland is composed of two distinct landscape zones: (1) glacially scoured terrain proximal to the major sources of Laurentide ice that flowed onto the foreland, and (2) ice distal unscoured sectors of the foreland. Both zones are draped with erratics and dissected by meltwater channels, indicating past ice cover. We interpret the two landscape classes in terms of ice sheet erosive ability linked with basal thermal regime: glacially scoured terrain was occupied by erosive warm-based ice, and unscoured terrain was last occupied by non-erosive cold-based ice. Cosmogenic exposure ages from >100 erratics from the two landscape types have different age distributions. Cosmogenic exposure ages from the glacially scoured areas suggest ice cover during the LGM, followed by deglaciation between ~15 and ~12 ka. In the unscoured lowlands, the cosmogenic exposure ages have multiple modes ranging between ~12 and ~50 ka, suggesting multiple periods of cold-based ice cover during the last glacial cycle. In landscapes covered by cold-based ice, large numbers of cosmogenic exposure ages are required for elucidating glacial histories.

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Thông tin xuất bản

Canadian Journal of Earth Sciences

Tập 42 Số 1

67-84

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