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TitleThe chronology of prehistoric earth flows within Breckenridge Valley, Quebec: A contribution to assessing hazards in the Ottawa Valley
AuthorBrooks, G RORCID logo; Medioli, B E; Aylsworth, J M; Lawrence, D E; Hunter, J A M
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 36, 2011 p. 27-28
Alt SeriesEarth Sciences Sector, Contribution Series 20100389
MeetingJoint Annual Meeting of the Geological Association of Canada, the Mineralogical Association of Canada, the Society of Economic Geologists and the Society for Geology Applied to Mineral Deposits; Ottawa, ON; CA; May 25-27, 2011
Mediapaper; CD-ROM
ProvinceQuebec; Ontario
AreaOttawa Valley; Breckenridge Valley; Gatineau; Aylmer
Lat/Long WENS -76.0000 -75.5000 45.5000 45.2500
Subjectssurficial geology/geomorphology; engineering geology; rivers; glacial deposits; slope failures; slope stability; terrain sensitivity; Champlain Sea
ProgramPublic Safety Geoscience Eastern Canada Geohazards Assessment Project
Released2011 01 01
AbstractBreckenridge Creek is a small tributary of the Ottawa River that drains about 66 km2 and is located approximately 14 km northwest of Aylmer, Gatineau, Quebec. Twenty-six prehistoric earth flow scars are clustered along the creek and its tributaries within an area of about 11 km2. This portion of the stream network is incised up to 30 m within a quasi-flat plain composed of fine-grained Champlain Sea sediments. The scars are up to 252 000 m2 in surface area, exhibit retrogression distances of up to 920 m, and are the product of either spreading or flowing. The local Champlain Sea sediments are 'quick' with local sensitivities reported to be in excess of 100. Geophysical data reveal that the landslide scars are situated over top of a buried bedrock valley filled with up to 90 m of soft sediment. The ages of the failures were determined using organic materials collected from spoil exposed in the scarps of modern failures and slumps, as well as along stream courses. At scars where spoil was not exposed or exposure(s) were barren of buried organic materials, wetlands situated between micro-ridges on the scar surfaces, and assumed to have formed on the post-earth flow topography, were cored to obtain minimum age(s) for these failures. Datable materials were collected from 11 of the 18 scars investigated. Radiocarbon analyses reveal that the ages of the failures span the past about 7000 yr BP (7800-7900 cal BP). Spoil from one event, aged about 1100 yr BP (1000-1100 cal BP), flowed down Breckenridge Creek valley, probably reaching the Ottawa River. The ages of the Breckenridge earth flows are compared to those of landslides and disturbed terrain associated with paleoseismic events in the Bourget-Lefaivre area, about 60 km east of Ottawa.

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