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TitlePaleoseismic assessment of multi-mass transport deposit signatures preserved within the deposits of glacial Lake Ojibway, northwestern Quebec, Canada
AuthorBrooks, G R
SourceProceedings of the 7th INQUA workshop on Active Tectonics, Paleoseismology and Archaeoseismology; 2016.
Alt SeriesEarth Sciences Sector, Contribution Series 20150436
Meeting7th INQUA workshop on Active Tectonics, Paleoseismology and Archaeoseismology; Crestone, Colorado; US; May 31 to June 4, 2016
Mediapaper; on-line; digital
File formatpdf
AreaLac Dasserat; Rouyn-Noranda
Subjectssedimentology; sediment transport; glaciolacustrine deposits; rhythmites; varves; sedimentation; deposition; Ojibway Lake; mass transport deposits (MTDs)
Illustrationslocation maps
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractEight event horizons were mapped using high-density sub-bottom profiles surveyed at Lac Dasserat, near Rouyn-Noranda, northwestern Quebec. Five of the event horizons (H-D) are intercalated within glaciolacustrine deposits of glacial Lake Ojibway, the other three (C-A) are at the interface of the glaciolacustrine-lacustrine deposits. Event horizons H, G and E exhibit multi-event MTD signatures consisting of 11, 13 and 21 failures, respectively. These three horizons are interpreted to be the products of paleoearthquakes with high, medium and medium levels of probable occurrence, respectively, based on the relative strength of the multi-MTD signatures, the lack of likely alternative aseismic interpretations, and the occurrences of similarly-aged disturbed deposits regionally in northwestern Québec-northeastern Ontario.
Summary(Plain Language Summary, not published)
Mapping at Lac Dasserat, Quebec, revealed that the deposits of a large number of ancient landslides are buried at multiple levels within the lake bed. All of the mapped landslide deposits occur within the glaciolacustrine deposits or at the interface between the glaciolacustrine deposits and overlying lacustrine deposits. This indicates that the landslide deposits are old, and were deposited when or immediately after a large glacial lake (known as glacial Lake Ojibway) occupied the region over 8000 years ago. Most of the landslides occur within one of four distinct levels within the lake bed, which implies that the landslides within each group happened synchronously and by a common trigger. It is interpreted that each group of landslides was triggered by shaking from an ancient earthquake. These earthquakes likely represent a period of elevated seismic activity that was caused by rapid regional crustal uplift which occurred as the Laurentide Ice Sheet retreated from the area.