The glacial, sea level, and sea ice histories of Melville and Eglinton islands, western Canadian High Arctic: Last Glacial Maximum to present

Recent mapping and surveying of surficial geology and geomorphology on Melville and Eglinton islands, Northwest Territories, Canada, demonstrates more extensive Late Pleistocene glacial limits than previously reported. These include a northwestward extension of the Laurentide Ice Sheet by at least 100 km, and possibly as far as the polar continental shelf edge, across purportedly "ice-free" terrain on Eglinton Island, and a radially outflowing, multi-domed local ice cap on Melville Island, which comprised a part of the lowland sector of the Innuitian Ice Sheet. The largely marine-based Laurentide Ice Sheet decoupled from the Innuitian Ice Sheet ∼13.6 cal yrs BP on southern Eglinton Island and progressed rapidly southeastward through M'Clure Strait to northern Victoria Island, where marine molluscs in deglacial sediments are the same age. Ice cap margins on western Melville Island remained stable and offshore until ∼13.0 cal yrs BP, and until ∼9.5 cal ka BP on eastern Melville Island. This chronology is based on >75 new radiocarbon-dated molluscs collected from ice-contact raised marine sediments surveyed along retreat pathways. Postglacial emergence is also outlined for this region. The forms of the relative sea level curves are diverse and include: Zone I curves showing continuous emergence to present; and transitional Zone I/II curves displaying emergence followed by submergence in the mid- to late-Holocene (still ongoing). Zone I curves are restricted to eastern Melville Island, while Zone I/II transitional curves occur on western Melville Island, and thus the crest of the glacial forebulge is presently located between these two areas, requiring that the zero isobase bisects the island. Of special interest are two localities (southern Melville Island and northern Eglinton Island) where the relative sea level history is described by flat-topped curves. These areas experienced earlier deglaciation by the Laurentide Ice Sheet while remaining in the peripheral depression of the more stable and adjacent Innuitian Ice Sheet. The flat-topped curves appear to record an unusual balance of glacio-isostatic emergence and eustatic sea level rise for up to 2000 years at these sites.