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

2014; Geological Society of America; Volume: 126; Issue: 3-4 Linguagem: Inglês

10.1130/b30911.1

1943-2674

Patrick Lajeunesse,

Geological formations and processes

Research Article| March 01, 2014 Buried preglacial fluvial gorges and valleys preserved through Quaternary glaciations beneath the eastern Laurentide Ice Sheet Patrick Lajeunesse Patrick Lajeunesse † Centre d'Études Nordiques and Département de Géographie, Université Laval, Québec, Québec G1V 0A6, Canada †E-mail: patrick.lajeunesse@ggr.ulaval.ca. Search for other works by this author on: GSW Google Scholar Author and Article Information Patrick Lajeunesse † Centre d'Études Nordiques and Département de Géographie, Université Laval, Québec, Québec G1V 0A6, Canada †E-mail: patrick.lajeunesse@ggr.ulaval.ca. Publisher: Geological Society of America Received: 29 Apr 2013 Revision Received: 14 Nov 2013 Accepted: 11 Dec 2013 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2014 Geological Society of America GSA Bulletin (2014) 126 (3-4): 447–458. https://doi.org/10.1130/B30911.1 Article history Received: 29 Apr 2013 Revision Received: 14 Nov 2013 Accepted: 11 Dec 2013 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Patrick Lajeunesse; Buried preglacial fluvial gorges and valleys preserved through Quaternary glaciations beneath the eastern Laurentide Ice Sheet. GSA Bulletin 2014;; 126 (3-4): 447–458. doi: https://doi.org/10.1130/B30911.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The geomorphology, geometry, and sedimentary infill 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 hydro-electric 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 Compilation of these previously published and unpublished data provided an exceptional opportunity to examine the morphology and spatial distribution of buried bedrock gorges and the mechanical processes responsible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, flutes, and scallops on the well-polished 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-profile of these gorges, their well-polished slopes, and the type of bedforms observed within them are typical features of fluvial 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 infill. 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 fluvial system eroded during a lower base level. This paleofluvial system is interpreted to be linked to fluvially cut channels observed on the seafloor of the Estuary and Gulf of St. Lawrence. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.