The Ottawa Islands are in the northeastern part of Hudson Bay. Evidence from crossing striations suggests that the earliest recorded glacial movement was toward the northeast. With deglaciation of Hudson Strait and central Hudson Bay the ice movement shifted progressively in an anti-clockwise direction, with the final movement being toward the west–southwest. The islands were deglaciated between 7610 and 7250 radiocarbon years ago. The marine limit is 158 m above sea level. Deltaic deposits below the marine limit are grouped into sets that correlate with glacial advances in Labrador–Ungava and Baffin Island, and with palynological results from Keewatin, suggesting that they reflect climatically induced processes rather than a balance in eustatic–isostatic movements. Radiocarbon dates on marine molluscs enable postglacial uplift and emergence curves to be drawn, which agree closely with predicted curves. Rates of uplift were about 0.06 m yr−1 at 6500 yr B.P., whereas the present rate is about 0.008 m yr−1. The deglaciation of Hudson Bay was marked by the splitting of the ice sheet along the submarine deep that trends southward between Mansel and Coats islands toward the southwest coast of the bay.

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