Relict Basal Ice from the Laurentide Ice Sheet Near Lac de Gras, Slave Geological Province, N.W.T., Canada



Stephan Gruber –



S. Gruber – Carleton University, Ottawa, ON, Canada
R. Subedi – Carleton University, Ottawa, ON, Canada
S.V. Kokelj – Northwest Territories Geological Survey, Yellowknife, NT, Canada


A 2015 drilling campaign of the Slave Province Surficial Materials and Permafrost Study near Lac de Gras has recovered permafrost core interpreted to contain preserved basal ice of the Laurentide Ice Sheet. Previous samples of basal ice from ice sheets originate from coring beneath modern ice divides, modern margins of Arctic icecaps that have preserved basal ice-sheet ice, or from studies near the margins of former ice sheets. The present study may be the first evidence of basal ice a few hundred kilometers from ice divides. In this intermediate zone, rates of erosion beneath an ice sheet increase and the thermal regime at the base varies. Our finding is relevant because it highlights the mosaic character of a landscape that contains terrain types with non-negligible ground-ice content, poised for climate-driven thaw and landscape change. The occurrence and mosaic character of preserved ice can be reconciled with glaciological theory and observations from mineral prospecting using the theory on the genesis of dispersal plumes in till developed by Hooke et al. (2013). The existence of preserved basal ice opens novel basic-research opportunities alongside exploration, mining and infrastructure development in the area.

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