ICE FLOWS AND LATE DEGLACIATION (CA 11 KA BP QUESTIONABLE) IN THE NORTHEASTERN REGION OF THE UNGAVA PENINSULA (QUEBEC, CANADA)

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 north eastward ice flow, from the Ungava Plateau, has marked the overall reg ion. It joined to an eastward ice stream occupying the Hudson Strait t hat left traces on Charles Island. This ice stream evacuated the Fore Basin and the Hudson Bay and overlapped to a limited extend the head o f the Ungava Peninsula at Cape Nouvelle-France. The thinness of the ti ll associated with the Ungava flow, the presence of perched blocks amo ng 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 are as. Subsequently to the westward glacial recession from the Hudson Str ait, 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 C-14 dating by accelerator mass spect rometry on marine mollusks permitted to locate the deglaciation of the plateau margin, between Deception Bay and Cafe Nouvelle-France, prior to 8.5 ka BP. Many older dates suggest the possibility of a very earl y opening of the Hudson Strait, as early as 10.5-11 ka BP. The early d eglaciation in some areas could explain the very high levels of the ma rine limit of the transgression observed at Cape Nouvelle-France. Furt hermore, many ages are intersecting the interval of 8.4-8.9 ka BP, mak ing suspicious the chronology of the glacial readvance of Noble Inlet across the Hudson Strait to the east.