Abstract

The last ice limit on Hall Land, northwest Greenland, is marked by the Newman and Petermann moraines, which were deposited 40–60 km beyond the present ice margins in Newman Bay and Petermann Fiord, respectively. These moraines flank the eastern and western coasts of Hall Land but do not extend into its intervening central plain. As a result of glacioisostatic depression at this time, a full glacial sea transgressed the entire central plain via a narrow estuary located between the Newman Moraine and the northern plateau of Hall Land. The limit of this full glacial sea is isostatically tilted from 116 m asl on the adjacent coast of Ellesmere Island to 150 m asl on the southwest extremity of the central plain, where it reaches its apex. Pervasive marine silts cover the central plain and laterally thicken towards the Newman and Petermann moraines. Because of the height of the full glacial sea, these moraines were deposited in a submarine environment and mark the grounded margins of ice shelves floating in Hall Basin and Newman Bay.Twenty-seven samples of marine pelecypods from the proximal and distal sides of these moraines were 14C dated. Distal to the moraines the limit of the full glacial sea is dated by in situ shells that range from 8200 to > 33 000 BP. During this interval relative sea level remained stable and the ice load was apparently in isostatic equilibrium. Initial emergence (unloading) throughout the full glacial sea (~8200 BP) coincides with the initial penetration of the sea inside the Newman Moraine dated at 7965 BP and inside the Petermann Moraine at 8280 and 8295 BP.This research concludes that (1) there was no Nares Strait ice ridge during the last glaciation, (2) ice retreat of only 40–60 km can cause 140–150 m of emergence, and (3) the deglaciation of northwest Greenland began at 8000 and not 10 000 BP. This research confirms that the relative sea-level curves from the adjacent coast of Ellesmere Island were isostatically dominated by the Greenland Ice Sheet.

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