PALEO-ICE STREAMS REVEALED BY COSMOGENIC EXPOSURE DATING OF DIFFERENTIALLY-WEATHERED LANDSCAPES

Recent results from the northeastern margin of the Laurentide Ice Sheet (LIS) suggest that fiords along northeastern Baffin Island contained ice streams during the Last Glacial Maximum (LGM). Differentially-weathered fiord landscapes across the Arctic have been interpreted differently in terms of glacial history. Highly-weathered inter-fiord uplands have been interpreted by some to indicate that they escaped LGM glaciation, and by others as having been covered during the LGM, but by non-erosive, cold-based ice. Erratics perched on highly-weathered uplands indicate that they have been covered by ice in the past.

We applied cosmogenic exposure dating to differentially-weathered landscapes in the Clyde Region, northeastern Baffin Island. Paired cosmogenic nuclide data (²⁶Al and ¹⁰Be) indicate that tors among weathered upland surfaces surrounding Clyde Inlet are at least 160 to 480 ka (n=5), whereas erratics perched on the tors range from 10 to 40 ka (n=23). The majority of the erratics fall between 10 and 20 ka (n=16), indicating that the uplands were covered by cold-based, non-erosive ice during the LGM. Cold-based ice on the uplands surrounding Clyde Inlet was almost certainly contemporaneous with warm-based glaciation of the fiord, suggesting that an ice stream occupied the fiord during the LGM. Extrapolated to similar settings, these findings imply that the northeastern margin of the LIS, and possibly other Pleistocene ice-sheet margins, may have been dominated by ice streams.