HR: 09:45h
AN: OS31A-08    [PDF]
TI: The Betsiamites-Outardes (Quebec) Submarine Mass Movements and Their Potential for Tsunami Generation
AU: * Locat, J
EM: locat@ggl.ulaval.ca
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Boisvert, L
EM: luc.boisvert@ggl.ulaval.ca
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Godin, A
EM: andre_godin@uqar.qc.ca
AF: Universit‚ du Qu‚bec … Rimouski, Centre Interdisciplinaire de D‚veloppement en Cartographie des Oc‚ans 310 all‚e des Ursulines, Rimouski, QC G5L 3A1 Canada
AU: Jeong, S W
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Levesque, C
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Levesque, M
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Locat, A
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Locat, P
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Parent, G
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Robicaud, G
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AU: Sanfa‡on, R
AF: Fisheries and Oceans Canada, Canadian Hydraugraphic Services Institut Maurice Lamontagne, Rimouski, QC G5H 3Z4 Canada
AU: Voyer, E
AF: Laval University, Department of Geology and Geological Engineering, Qu‚bec, QC G1K 7P4 Canada
AB: The Betsiamites Outardes area has been the locus of a team effort to investigate the connection between submarine features indicative of large mass movements and the presence of a coastal slide scar involving about 800 millions cubic metres of raised marine deposits along the North Shore of the St. Lawrence River, about 300 km east of Qu‚bec city.. Although the signature of the coastal slide is quite clear, the underwater morphology, revealed by a multibeam survey, indicated the presence of a complex system of flow features imbricated into a channel landform most likely related to the relic Betsiamites River submarine channel system. Holocene deposits related to the high-stand delta have also been eroded leaving, in places, significant escarpment of nearly 100m. In addition there are clear bedrock related features forming the major boundary between the shelf, less than 100m deep, and the deeper part in the middle of the St. Lawrence Estuary at a depth of about 400m. Just in front of the sub-aerial slide, lies, in the central and deep part of the St. Lawrence, a very extensive feature with a more or less regular elevation of about 10m above the surrounding sea floor and covering an area of about 130 square kilometers. The initial interpretation was to consider it as the distal depositional part of the sub-aerial slide sediments. A recent detailed high resolution seismic survey indicated otherwise and rather revealed that much of it could have been pushed up, or deformed, by underlying gas pressure of an origin still to be determined, but which could be related to the surrounding bedrock structure. On the other hand, the seismic survey on the shelf confirmed the presence of extensive debris flow deposits with various signatures including compression ridges and other evidences of rapid mass movements. At the time of writing, it is not clear what is the origin of the slide and the triggering mechanism and if it could have originate from the shelf and propagate onto the coastal zone. The dating of the sub-aerial slide has been linked to the 1663 earthquake but this still awaits confirmation. Actual morphological information and the seismic survey indicate that the slide was very large and that it developed into a rapid mass movements with a high potential for generating a tsunami wave. This wave should have easily crossed the St. Lawrence Estuary and leave typical inundation deposits in the marshes boarding the south shore, near Rimouski.
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 3045 Seafloor morphology and bottom photography
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting