Late Wisconsinan deglaciation and proglacial lakes development in the Charlevoix region, southeastern Québec, Canada

Abstract

The Charlevoix region, in southeastern Québec, is characterized by a dramatic landscape formed by the junction of the Laurentian Highlands, the Charlevoix Astrobleme and the St Lawrence Estuary. At the Last Glacial Maximum (LGM), the region was completely covered by the Laurentide Ice Sheet (LIS). The complex topography of the region was the stage of many of the major deglacial events of southern Quebec (e.g. Goldthwait Sea Invasion, St Lawrence Ice‐Stream, Saint‐Narcisse Episode). We present a detailed reconstruction of the pattern of retreat of the LIS in the Charlevoix region based on the interpretation of ice‐marginal features (e.g. moraines, fans) and glaciolacustrine landforms and deposits, two extensive field campaigns, and the interpretation of high‐resolution 3D digital aerial photographs and LiDAR data. Our results indicate five moraine complexes in the region: the Rochette, the Brûlée, the Sainte‐Anne, the Saint‐Narcisse and the Mars‐Batiscan complexes. Deltas, fans, fine‐grained sediments, littoral deposits, drainage breaches and deposits were used to identify 91 palaeo‐proglacial lakes. The identification of these lakes and their relation to moraine complexes enabled the reconstruction of six stages of lake development during the Charlevoix deglaciation. The development of proglacial lakes occurred in all types of terrain (highlands, lowlands, transitory levels above marine limit). We conclude that local topography had a decisive effect on promoting both moraine deposition and lake development. We suggest that similar topographical regions (hilly‐mountainous) that were affected by major ice‐margin stabilizations during glacial retreat should have experience small lakes dominating valleys and topographical lows.

Ice-stream flow switching by up-ice propagation of instabilities along glacial marginal troughs

“…Glacial lineations are highly elongated (apparent elongation ratio 1 : 10) parallel ridges formed in glacigenic sediments (Clark, 1993). Most glacial lineations are observed in Scott and Hecla & Griper Trough at depths between 218 and 840 m, where they have lengths ranging from 156 to 8664 m with a mean of ∼ 1026 m (Fig.…”

“…In some cases, ridges have a rougher texture that may imply a bedrock character or very thin sediment cover. MSGLs are indicators of fast ice flow, suggesting paleo-ice-stream activity (Clark, 1993;Stokes and Clark, 2002a). Accordingly, they also indicate ice flow orientation.…”

Submarine geomorphology of the northeastern Baffin Island fiords and cross-shelf troughs

“…Crag-and-tails have been widely used in paleoglaciological reconstructions as indicators of ice-flow orientation (e.g. Brouard & Lajeunesse, 2019a;De Angelis & Kleman, 2007;Jansson, Stroeven, & Kleman, 2003;Hogan et al, 2010;Brouard, Lajeunesse, Cousineau, Govare, & Locat, 2016). In association with MSGL, drumlins and grooves, crag-and-tails generally indicates relatively fast ice-flow conditions, i.e.…”