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

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 similar to 15 and similar to 12 ka. In the unscoured lowlands, the cosmogenic exposure ages have multiple modes ranging between similar to 12 and similar to 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.