Le Quaternaire Du Sud-Est Du Bouclier Canadien [Chapitre 3: Le Quaternaire Du Bouclier Canadien]

Vincent, J S

doi:10.4095/127972

Cited by 6 publications

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“…The magnitude (between 175 and >350 m) of the base level lowering responsible for the incision of inner gorges and V-shaped valleys precludes a glacio-isostatic and glacioeustatic origin because (1) no eustatic sea level fall of this magnitude has been recorded during the Quaternary glacial and interglacial episodes (Miller et al, 2005), and especially not since the last deglaciation (Dyke and Peltier, 2000;Peltier, 2004); (2) the region was completely covered by the Laurentide Ice Sheet when glacio-eustasy reached its lowest level of -125 m during glaciation (Peltier, 2004); (3) when the margin of the Laurentide Ice Sheet retreated, the St. Lawrence Estuary and Gulf and James Bay coastlines were glacio-isostatically depressed by >130 m and >250 m, respectively, and submerged by a marine transgression (i.e., postglacial sea) (Vincent, 1989;Dyke and Peltier, 2000), a situation that also prevailed during previous interglacials.…”

Section: Preserved Preglacial Fluvial Gorges and Valleysmentioning

confidence: 99%

Buried preglacial fluvial gorges and valleys preserved through Quaternary glaciations beneath the eastern Laurentide Ice Sheet

Lajeunesse¹

2014

Geological Society of America Bulletin

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The geomorphology, geometry, and sedimentary infi ll of buried gorges and V-shaped valleys observed at the base of major river valleys in the formerly glaciated southeastern Canadian Shield region have been revealed from excavation and drilling data acquired during the construction of hydroelectric dams and seismic data collected on lakes and offshore. Compilation of these previously published and unpublished data provided an exceptional opportunity to examine the morphology and spatial distribution of buried bedrock gorges and the mechanical processes responsible for their erosion. In some valleys, detailed observations of deep gorges have been allowed by their exhumation over large areas. Archive photographs show deep and large potholes, natural pillars, furrows, fl utes, and scallops on the wellpolished bedrock walls of the gorges. They also reveal that gorges and valleys have a sharp-ending V shape and very narrow base and are superimposed by a U-shaped valley, forming a buried valley-within-valley topography. The narrow and deep cross-profi le of these gorges, their well-polished slopes, and the type of bedforms observed within them are typical features of fl uvial bedrock channels. Drilling operations at many sites have also provided data on bedrock topography of these gorges within valleys and on the nature of their sedimentary infi ll. The different lines of evidence presented in this paper indicate that gorges and V-shaped valleys of the region were not eroded by the Laurentide Ice Sheet during Quaternary glaciations but are relics of a preserved preglacial fl uvial system eroded during a lower base level. This paleofl uvial system is interpreted to be linked to fl uvially cut channels observed on the seafl oor of the Estuary and Gulf of St. Lawrence.

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Section: Preserved Preglacial Fluvial Gorges and Valleysmentioning

confidence: 99%

Buried preglacial fluvial gorges and valleys preserved through Quaternary glaciations beneath the eastern Laurentide Ice Sheet

Lajeunesse¹

2014

Geological Society of America Bulletin

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Landscape diversity and forest edge density regulate stream water quality in agricultural catchments

Clément

Ruiz

Rodríguez

et al. 2017

Ecological Indicators

112

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Erratiques de dolomie au Cap Colombier, sur la haute Côte-Nord du Saint-Laurent estuarien

Dionne¹

2002

gpq

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À environ 150 km au NE de Tadoussac, le cap Colombier apparaît comme le site le plus oriental connu de la dispersion des erratiques de dolomie sur la rive nord de l'estuaire maritime du Saint-Laurent. Une cinquantaine de cailloux de dolomie de diverses catégories ont, en effet, été observés sur le bas estran argileux du havre du Colombier. La taille des cailloux va de 7 à 320 cm (axe-a). Si le plus gros bloc pèse environ 20 tonnes, les autres sont beaucoup plus petits : les dix plus gros pesant entre 33 et 345 kg. Il y a environ 12 % de cailloux de dolomie cristalline de couleur rose et 20 % des cailloux sont striés. Un bloc de dolomie partiellement bréchique contenait des structures stromatolitiques. La source la plus vraisemblable demeure le bassin sédimentaire de Mistassini situé à environ 500 km au NO, ce qui implique, dans un premier temps, un transport glaciaire par un courant de glace à partir d'un dôme localisé au NO du lac Mistassini, puis, dans un deuxième temps, une mise en place par des icebergs dans la Mer de Goldthwait probablement issus de la langue glaciaire canalisée dans le Saguenay.

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Le Quaternaire Du Sud-Est Du Bouclier Canadien [Chapitre 3: Le Quaternaire Du Bouclier Canadien]

Cited by 6 publications

References 0 publications

Buried preglacial fluvial gorges and valleys preserved through Quaternary glaciations beneath the eastern Laurentide Ice Sheet

Buried preglacial fluvial gorges and valleys preserved through Quaternary glaciations beneath the eastern Laurentide Ice Sheet

Landscape diversity and forest edge density regulate stream water quality in agricultural catchments

Erratiques de dolomie au Cap Colombier, sur la haute Côte-Nord du Saint-Laurent estuarien

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