Identification and dating of a key Late Pleistocene stratigraphic unit in the St. Lawrence Estuary and Gulf (Eastern Canada)

St‐Onge, Guillaume; Lajeunesse, Patrick; Duchesne, Mathieu J.; Gagné, Hubert

doi:10.1016/j.quascirev.2008.08.023

Cited by 40 publications

(44 citation statements)

References 21 publications

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“…In the St. Lawrence Estuary, bedrock reaches depths of 800 bsl, which is probably too deep to have been eroded by glacial ice (Duchesne et al, 2010). In this sector, the presence of >150 m of sediments below a sedimentary unit deposited during deglaciation (St-Onge et al, 2008) suggests that the erosion and initial infi lling of this basin took place before the last glaciation. In the Saguenay Fjord (Fig.…”

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 Compilation of these previously published and unpublished data provided an exceptional opportunity to examine the morphology and spatial distribution of buried bedrock gorges and the mechanical processes responsible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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“…14 C ages from material in the upper units indicate a Holocene age. However, since the entire Quaternary sediment package has never been cored, the exact age of the oldest part of the succession is unknown (St-Onge et al, 2008). The Quaternary succession fills an irregularly shaped basin characterized by two large troughs that are interpreted as resulting mainly from repeated (?)…”

Section: Geological Settingmentioning

confidence: 99%

Methane-derived authigenic carbonates from active hydrocarbon seeps of the St. Lawrence Estuary, Canada

Lavoie

Pinet

Duchesne

et al. 2010

Marine and Petroleum Geology

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“…Regional stratigraphic frameworks for the estuary are provided by Syvitski and Praeg (1989), St-Onge et al (2008) and Duchesne et al (2010) who described seismo-stratigraphic units associated with one or several glacial cycle(s). Post-glacial Holocene sediments deposited under modern sea-level and oceanographic conditions form the seafloor except near the mouth of the Saguenay River, where undated preHolocene sediments (seismic unit 1 of Duchesne et al, 2010) have been mapped (Pinet et al, 2011a).…”

Section: Physiographic and Geological Settingsmentioning

confidence: 99%

Geomorphological characteristics and variability of Holocene mass-transport complexes, St. Lawrence River Estuary, Canada

et al. 2015

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Identification and dating of a key Late Pleistocene stratigraphic unit in the St. Lawrence Estuary and Gulf (Eastern Canada)

Cited by 40 publications

References 21 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

Methane-derived authigenic carbonates from active hydrocarbon seeps of the St. Lawrence Estuary, Canada

Geomorphological characteristics and variability of Holocene mass-transport complexes, St. Lawrence River Estuary, Canada

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