CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Gagne, H.; Lajeunesse, P.; St-Onge, G.; and Bolduc, A.
Date : 2007.
Title : Morphosedimentology of submarine canyons and fans in the Les Escoumins area, lower St. Lawrence estuary (Québec).
Publication : CMOS, CGU, AMS Congress 2007. "Air, Ocean, Earth and Ice on the Rock". May 28 - June 1, 2007. St. John's Congress Centre, Newfoundland and Labrador, Canada.
Issue :
Page(s) : G09-1B2 .8.
Abstract
Multibeam sonar data, acoustic subbottom profiles and two boxcores were used to reconstruct the formation of submarine canyons and fans near Les Escoumins, in the lower St. Lawrence Estuary. The multibeam data were used to generate a high-resolution Digital Terrain Model that shows the presence of a large number of canyons and fans along the northern slopes of the Laurentian Channel. This paper focuses on two of the larger canyons and their associate submarine fans. The chirp profiles recorded on the fans show high amplitude reflectors located at the sediment/water interface and near surface, indicating the occurrence of layers of coarse material. Box cores 76BC (44cm) and 77BC (26cm) were sampled in 2006 onboard the R/V Coriolis II. These cores were run through a Multi Sensor Core Logger (MSCL) for the determination of density, porosity and magnetic susceptibility, as well as through a CAT-Scan for the identification of sedimentary structures and the extraction of CT numbers. Color reflectance measurements were also performed on the split cores using a hand-held spectrophotometer, whereas grain size analyses were realized with a Coulter Counter laser sizer at 1 cm intervals. The grain size data reveal poorly sorted sandy to muddy sands with the possible occurrence of several turbidites. 210Pb measurements are currently underway and should help determine recent sedimentation rates and the modern activity of these canyons and fans. Finally, the combination of the geophysical and sedimentological data suggests that the canyons and fans may have been constructed by the sediment delivery to the bottom of the Laurentian Channel from the eroding coastline and the nearby river deltas of the Les Escoumins and the Portneuf rivers, where sandy sediments were transported by the east-west longshore drift, trapped head of the canyons during their transit and then transported downslope by turbidity currents.
Bibliography of Canadian Geomorphology