A series of 178 radiocarbon dates, of late glacial and postglacial age, from raised marine terraces on the Hudson Strait, Hudson Bay, and Ungava Bay coasts, permit a new synthesis of deglaciation history, postglacial emergence, and glacio-isostatic recovery of the Ungava Peninsula. Marine limits show three local highs, related to centres of ice loading: east of Hudson Bay; southwest of Ungava Bay, and in western Hudson Strait. Eastward extension of the latter to Cap de Nouvelle-France is attributed to early deglaciation. Emergence curves are presented from sites in (1) Hudson Strait ice-free prior to 9 ka; (2) Hudson Strait; (3) Hudson Bay; and (4) Ungava Bay liberated by Ungava ice between 8 and 6 ka. A sigmoidal pattern for the first group, with slow initial emergence, contrasts markedly with a pattern of rapid deceleration of emergence for the other groups. These differences are attributed to variations in rates of ice sheet unloading, immediately after coastal deglaciation. A stable onshore ice margin kept the northeastern tip of Ungava isostatically depressed, from initial deglaciation until 7 ka, whereas other mainland coasts were only liberated by retreat of the ice margin during a final phase of rapid thinning of the continental ice sheet. Isobases on emergence since 6.5, 5, and 2 ka, derived from marine and glacial lake shoreline data, indicate maximum ice loading centres in eastern Hudson Bay and in central Quebec–Labrador, with an extension northwards towards Ungava Bay. An uplift rate of 14 mm/year since 2 ka for Inukjuak on the Hudson Bay coast is compatible with very high tide gauge values. A downward gradient of 6.5 ka isobases in a northeasterly direction from southeastern Ungava towards present sea level on southern Resolution Island at the mouth of Hudson Strait suggests that Ungava Bay, despite late occupation by glacial ice, was probably not a major loading centre.

Studies of the lithological composition and carbonate contents in the till, the glacial striations and the glacial geomorphology allowed the identification of two distinct ice flows at the northeast end of the Ungava Peninsula and in the area of the Hudson Strait. A general northeastward ice flow, from the Ungava Plateau, has marked the overall region. It joined to an eastward ice stream occupying the Hudson Strait that left traces on Charles Island. This ice stream evacuated the Foxe Basin and the Hudson Bay and overlapped to a limited extend the head of the Ungava Peninsula at Cape Nouvelle-France. The thinness of the till associated with the Ungava flow, the presence of perched blocks among which some are pedestal, and the lack of tapered forms suggest the presence of a ice with low content of debris and cold base in some areas. Subsequently to the westward glacial recession from the Hudson Strait, a readvance of the Ungava glacier with northeast-north direction intersected the earlier eastward movement and calved in the strait at the North of Charles Island. New 14C dating by accelerator mass spectrometry on marine mollusks permitted to locate the deglaciation of the plateau margin, between Deception Bay and Cape Nouvelle-France, prior to 8.5 ka BP. Many older dates suggest the possibility of a very early opening of the Hudson Strait, as early as 10.5–11 ka BP. The early deglaciation in some areas could explain the very high levels of the marine limit of the transgression observed at Cape Nouvelle-France. Furthermore, many ages are intersecting the interval of 8.4–8.9 ka BP, making suspicious the chronology of the glacial readvance of Noble Inlet across the Hudson Strait to the east.

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