Abstract

The Laurentide ice sheet in eastern Canada disintegrated step by step, as evidenced by several morainic complexes. Although commonly interpreted as reflecting climatic events, it seems probable that the disintegration simply related to changes in the dynamics of the ice margin, without climatic control. From the example of the Late Glacial Sakami moraine in Quebec, formed during the drainage of Lake Ojibway into the Tyrrell Sea, the concept of a “re-equilibration moraine,” already briefly proposed, is developed. The construction of such a moraine implies a stabilization of the ice front when the glacier margin, previously floating or calving in a lacustrine or marine basin, is suddenly grounded because of topographic blocking or abrupt drop of water level due to drainage. The glacial retreat then pauses until the equilibrium profile of the ice is restored, and a morainic accumulation can form during the halt.

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