Spatial Patterns of Frozen vs. Sliding Basal Conditions of the Northeastern Laurentide Ice Sheet

Cosmogenic exposure (CE) dating and glacial-geologic mapping along northeastern Baffin Island, Arctic Canada, indicate sharp contrasts in Laurentide Ice Sheet (LIS) basal flow dynamics during the last glaciation. Northeastern Baffin Island is characterized by glacially-scoured fiords with inter-fiord landscapes that exhibit advanced bedrock weathering characteristics. CE ages of erratics indicate that both the fiords and inter-fiord regions were covered by the LIS during the last glaciation. However, CE ages of bedrock in both settings indicate that while the fiords held erosive ice, adjacent plateaux were covered by non-erosive and presumably frozen-bedded ice. This contemporaneous juxtaposition of sliding and non-sliding ice suggests that ice streams may have drained the northeastern LIS during the last glaciation. The sharpness of the boundary between eroded and uneroded bedrock, in places <1 km, and the longitudinal elevation gradient of this boundary, which decreases seaward, help to constrain ice sheet geometry. Differentially-weathered landscapes, like those along northeastern Baffin Island, may be good locations to study bed conditions of former "fixed" ice streams. In addition, these ice streams of the past provide possible analogues for the basal flow dynamics of contemporary "fixed" ice streams.