| Ice sheets are an integral part of the Earth's climate system, but the chronology and dynamics of Pleistocene ice sheets is in most places only loosely constrained. In the Eastern Canadian Arctic, for example, the history of the northeastern Laurentide Ice Sheet (LIS) during the Last Glacial Maximum (LGM) is only known in selected regions, but is extrapolated to broader areas. More than 160 cosmogenic exposure ages from the Clyde Region, northeastern Baffin Island, reveal that the northeastern LIS was more extensive and dynamic than previously depicted. Tors on weathered uplands surrounding Clyde Inlet are covered with perched erratics that have cosmogenic exposure ages of 20--10 ka, indicating that the uplands were glaciated by cold-based, non-erosive ice during the LGM. In contrast, warm-based, erosive ice probably occupied Clyde Inlet throughout the LGM, indicating strong gradients in basal thermal regimes and the operation of an ice stream in Clyde Inlet. In the most distal sectors of the Clyde Foreland, where cold-based ice hardly modified the landscape, erratics yield a multi-modal exposure age distribution that may indicate numerous advances and retreats of cold-based ice across the foreland throughout Marine Isotope Stages 3 and 2. Ice retreated from the Clyde Foreland ∼13 ka, from the mouth of Clyde Inlet ∼12--10 ka, and had reached the fiord head by ∼8.3 ka. Upland tors surrounding outer Clyde Inlet have single-nuclide apparent exposure ages >60 ka. However, paired 26Al and 10Be concentration data reveal that they are at least several hundred thousand years old, indicating that while the uplands have been covered by ice off and on throughout the Quaternary, they have only been slightly modified.; These new data depict an extensive LIS in the Clyde Region during the LGM, possibly terminating at the continental shelf break beyond Clyde Inlet. Strong gradients in basal thermal regimes suggest highly variable patterns in glacier thickness, velocity, and erosion, an overall pattern indicative of ice stream activity. A northeastern LIS this dynamic and extensive would have been closely linked with fluctuating ocean circulation and sea level. |
