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The Decay and Disappearance of the Late Wisconsin Ice Sheet in the Ungava Peninsula, Northern Quebec, Canada
Bernard Lauriol and James T. Gray
Arctic and Alpine Research
Vol. 19, No. 2 (May, 1987), pp. 109-126
Published by: INSTAAR, University of Colorado
Stable URL: http://www.jstor.org/stable/1551245
Page Count: 18
You can always find the topics here!Topics: Ice, Eskers, Bays, Moraines, Glacial lakes, Peninsulas, Ice sheets, Coasts, Seas, Valleys
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The article presents a synthesis of the pattern and chronology of the retreat of the late Wisconsin ice sheet on the Ungava Peninsula. The spatial distribution of landforms of deglaciation is discussed. These include De Geer moraines, eskers, kames, outwash deltas and fans, meltwater gorges, moraine ridges, and ice disintegration features. These data permitted the authors to demarcate the former glacial drainage divide on the peninsula, and to identify major zones of important meltwater activity, on either side of a central zone where subglacial drainage was of little importance. The data also show contrasts between an active, calving ice front on the Hudson Bay coastal fringe, and a stagnating ice margin on the Hudson Strait and Ungava Bay coasts. Radiocarbon dates indicate that deglaciation of the Cap de Nouvelle-France sector of the Hudson Strait coast commenced prior to 10,000 BP, that most of the present Hudson Bay coast was deglaciated at about 8000 BP, and that southern Ungava Bay only became deglaciated after 7000 BP. The ice lingered in the Baie-aux-Feuilles area in southwestern Ungava Bay and in the lower Rivière Kovik basin until about 6500 BP. The interior plateau and the long trenches, occupied by Rivière aux Mélèzes, Rivière aux Feuilles, and Rivière Arnaud, were deglaciated between 7000 and 5000 BP in two major phases. During the first phase, eskers were built at the base of a stagnant ice sheet which still covered almost the entire peninsula. During the second phase, the ice sheet on the Ungava plateau separated into several residual ice caps. At least two important ice-dammed lakes were formed between heights of land and these ice masses. On the Ungava Bay flank of the peninsula, penetration of the postglacial D'Iberville Sea far inland, up the trenches of the major river valleys, between 6500 and 5000 BP accompanied retreat of these ice masses. Final disappearance of ice sheet remnants on the plateau occurred at about 5000 BP.