Coalescent Greenland and Innuitian ice during the Last Glacial Maximum: revising the Quaternary of the Canadian High Arctic

Abstract

This paper constitutes a fundamental revision of the author’s earlier research and resolves a long-standing debate concerning the late Quaternary history of the Canadian High Arctic, supporting its inundation by glaciers during the Last Glacial Maximum (LGM). A transect along east Ellesmere Island demonstrates that ice advanced northward and southward along the axis of Nares Strait during the late Wisconsinan, debouching from a central saddle in Kane Basin. The configuration of Ellesmere Island and Greenland ice is based on moraines, meltwater channels and erratics. The youngest AMS 14C date obtained on shelly till suggests ice buildup after 19 ka BP whereas many other dates are younger than 30 ka BP. Furthermore, the lowest (youngest) detectable amino acid ratios on shells from till postdate the Robeson aminozone (>70 ka BP) and are separated from Holocene ratios by a narrow gap wholly consistent with the occupation of the strait by late Wisconsinan ice. Re-entry of the sea throughout Nares Strait is shown by a series of paleogeographic maps based on geomorphic evidence and radiocarbon dates on shells associated with marine limit. Deglaciation at the north end of the strait occurred by 10.1 ka BP and, at the south end, by 9.0 ka BP. Nares Strait may still have been blocked by ice north of Kane Basin at 8 ka BP, however; by 7.5 ka BP it provided an unobstructed seaway from the Arctic Ocean to Baffin Bay. The prominent ice margins within the fiords of eastern Ellesmere Island, previously considered to mark the last ice limit, record regional stabilization of land-based ice after breakup of preceding marine-based margins. Other implications of this study are: that ice buildup occurred post-30 ka BP (and possibly post-19 ka BP) during an interval widely assumed to be constrained by severe aridity in the high arctic; and that coalescent Greenland and Ellesmere Island ice during the LGM promoted thickening of the eastern Ellesmere Island ice divide, causing enhanced westward flow across the island to Eureka Sound. Sizeable postglacial emergence (80–120 m) on eastern Ellesmere Island is associated with the retreat of thick ice (⩾1 km) from the strait. Greater emergence in Eureka Sound, which extends southward into the central arctic islands, confirms the previously proposed axis of the Innuitian Ice Sheet. Further clarification of the extent, geometry, and retreat of the Innuitian Ice Sheet will provide new opportunities for glaciological and geophysical modelling, and help to identify late Quaternary sediment sources for the Arctic Ocean and Baffin Bay.