The succession of ice-flow patterns in north-central Qu! ebec-Labrador, Canada

Qu! ebec-Labrador, Canada, is one of the postulated dispersal centres of the Late Wisconsinan Laurentide Ice Sheet, and also contains an unusually complex and rich glacial geological record. A reliable reconstruction of glaciation history represented by this record would improve our comprehension of the dynamics of the eastern sector of the Laurentide Ice Sheet, such as the evolution of the basal thermal regime and the timing of enhanced ice flow into Ungava Bay. We mapped glacial landforms over a 200,000 km area using aerial photographs, and conducted a detailed field-based survey of the central part of the area to establish the relative age of crosscutting glacial-geological features. The position of the last ice remnant was south of Ungava Bay, well north of what has commonly been perceived as the location for this dispersal centre. Southward (radial) flow from a northward migrating and predominantly cold-based dispersal centre was the last glacial event in north-central Qu! ebec-Labrador. A widespread occurrence of older ice flow traces towards the southwest was detected. In some areas, large drumlins, formed during this ice-flow event, occur in alignment with landforms formed during the last deglaciation. This older southwestward flow is, however, overprinted by, and therefore predates, traces of northward convergent flow into Ungava Bay (Ungava Bay flow), traces of a northeastward flow event, and in some areas, traces of the deglacial flow event. Flutes and glacial striae indicating ice flow towards northeast are superimposed on the Ungava Bay flow. The northeastward ice-flow system has been recognised across the mapped area, and because of its direction and regional significance, we infer formation approximately during the Last Glacial Maximum. # 2002 Elsevier Science Ltd. All rights reserved.