ABSTRACT: Time perspectives on glacial landscape formation - glacial flow chronology at Lac aux Goilands, northeastern Quebec, Canada.

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Abstract

We used mapping from aerial photographs and field investigations around Lac Aux Goélands (Whitegull Lake), northeastern Québec, to establish a glacial flow chronology that involves three different glacial landform systems. We interpret the youngest of these systems as related to the late Wisconsinan deglaciation. This system has an up-glacier discontinuity that marks a temporal shift from warm-based subglacial conditions to non-erosive cold-based subglacial conditions, whereby older glacial landscapes are preserved in the interior of Québec-Labrador. Furthermore, our results support theories suggesting a northward migrating ice divide to a final position south of Ungava Bay during the final deglaciation. The recognition that a glacial landscape is fragmented and consists of smaller, temporally unrelated units is of considerable significance in understanding ice-sheet dynamics and patterns of subglacial preservation and destruction. This is because a fragmented landscape implies a fragmented formation history, where formation of subglacial landforms occurred in restricted subglacial zones during restricted time periods. Periods of formation must have been separated by periods of preservation and inhibited subglacial reshaping. Based on estimates of the ice margin retreat velocity and the velocity of the warm-based inward migrating zone, we suggest that periods of preservation were orders of magnitude longer than periods of subglacial landform formation.

Bibliography of Canadian Geomorphology