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

This paper constitutes a fundamental revision of the author's earlier resea rch and resolves a long-standing debate concerning the late Quaternary hist ory of the Canadian High Arctic, supporting its inundation by glaciers duri ng the Last Glacial Maximum (LGM). A transect along east Ellesmere Island d emonstrates that ice advanced northward and southward along the axis of Nar es Strait during the late Wisconsinan, debouching from a central saddle in Kane Basin. The configuration of Ellesmere Island and Greenland ice is base d on moraines, meltwater channels and erratics. The youngest AMS C-14 date obtained on shelly till suggests ice buildup after 19 ka BP whereas many ot her dates are younger than 30 ka BP. Furthermore, the lowest (youngest) det ectable amino acid ratios on shells from till postdate the Robeson aminozon e ( > 70 ka BP) and are separated from Holocene ratios by a narrow gap whol ly 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 paleoge ographic maps based on geomorphic evidence and radiocarbon dates on shells associated with marine limit. Deglaciation at the north end of the strait o ccurred 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 Baff in Bay. The prominent ice margins within the fiords of eastern Ellesmere Is land, previously considered to mark the last ice limit, record regional sta bilization of land-based ice after breakup of preceding marine-based margin s. 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 Green land and Ellesmere Island ice during the LGM promoted thickening of the eas tern Ellesmere Island ice divide, causing enhanced westward Bow across the island to Eureka Sound. Sizeable postglacial emergence (80-120 m) on easter n Ellesmere Island is associated with the retreat of thick ice ( greater th an or equal to 1 km) from the strait. Greater emergence in Eureka Sound, wh ich extends southward into the central arctic islands, confirms the previou sly proposed axis of the Innuitian Ice Sheet. Further clarification of the extent, geometry, and retreat of the Innuitian Ice Sheet will provide new o pportunities for glaciological and geophysical modelling, and help to ident ify late Quaternary sediment sources for the Arctic Ocean and Baffin Bay. ( C) 1999 Elsevier Science Ltd. All rights reserved.