PAIRED COSMOGENIC ISOTOPE DATA PROVIDE INSIGHTS INTO GLACIAL-LANDSCAPE EVOLUTION ALONG EASTERN BAFFIN ISLAND, ARCTIC CANADA

New cosmogenic isotope measurements from eastern Baffin Island, Arctic Canada, shed light on the evolution of differentially-weathered fiord landscapes. Tors on upland surfaces in the Clyde Region, northeastern Baffin Island, have minimum single-nuclide exposure ages (¹⁰Be, PR=5.1 atoms g^-1 yr^-1) of 63 to 102 ka. The majority of 23 dated erratics that overlie these upland tors fall between 10 and 20 ka, suggesting that the uplands were covered by the Laurentide Ice Sheet (LIS) during the Last Glacial Maximum, but were not eroded. Paired cosmogenic isotope data extend this record of upland burial by non-erosive ice farther into the past. ²⁶Al/¹⁰Be ratio vs. ¹⁰Be concentration data from six tors reveal minimum tor histories beginning 160 to 560 ka, and minimum periods of burial of 60 to 440 ky. Assuming that the uplands were nuclide-saturated at the onset of Quaternary glaciations, these landscapes experienced both the aforementioned period of burial, and either a high subaerial erosion rate (>5 m Ma^-1) or some glacial erosion. The tors from Clyde have a much shorter history than tors on northern Cumberland Peninsula, southeastern Baffin Island. For example, ²⁶Al/¹⁰Be data from three tors on Broughton Island reveal minimum histories beginning 1310-1450 ka, and minimum periods of burial of 580-840 ky. However, tors on southern Cumberland Peninsula near Cumberland Sound, a major pathway for a Laurentide outlet glacier or ice stream, have a similar history to those at Clyde. Two main factors could account for the differences between the two sites, subaerial erosion or glacial erosion. Because the bedrock and climate of the Clyde Region and Cumberland Peninsula are similar, subaerial erosion rates are likely the same. Thus, it appears that uplands of the Clyde Region and those adjacent to Cumberland Sound, which are closer to the dome of the northeastern LIS, have been periodically eroded by the LIS, whereas the uplands of northern Cumberland Peninsula, farther from the dome, have escaped glacial erosion, perhaps through the entire Quaternary Period.