Time perspectives on glacial landscape formation—glacial flow chronology at Lac aux Goélands, northeastern Québec, Canada

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 icesheet 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.

A glacial geomorphological map of the southernmost ice lobes of Patagonia: the Bahía Inútil – San Sebastián, Magellan, Otway, Skyring and Río Gallegos lobes

“…Glacial lineations form beneath an ice sheet and are aligned with ice flow direction (Clarhäll & Jansson, 2003). They occur frequently throughout the study area, from scattered and subdued flutings (,1 m high) to tightly constrained clusters of classic oval-shaped drumlins tens of metres high (Figure 7).…”

Patterns of Quaternary ice sheet erosion and deposition in Fennoscandia and a theoretical framework for explanation

“…For more realistic polythermal ice sheets (Fig. 4), the spatial arrangement and duration of zones with a thawed bed are important for patterns of erosion and deposition (Clarhäll and Jansson, 2003;Harbor et al, 2006). Without warm-based zones where erosion and sediment entrainment can occur, there will be no material available for deposition in the marginal zone.…”

Reconstructing the confluence zone between Laurentide and Cordilleran ice sheets along the Rocky Mountain Foothills, south‐west Alberta

“…Glacial lineation Includes flutes, drumlins and streamlined bedrock (Clarhäll and Jansson, 2003 Marks the boundary between slow and fast moving ice (Stokes and Clark, 2002).…”