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TitleEvidence of early postglacial paleoearthquakes from mass transport deposits buried within glaciolaustrine sediments in northeastern Ontario-western Quebec, Canada
AuthorBrooks, G RORCID logo
SourceGAC®-MAC 2021, London, Canada: Exploring Geosciences Through Time and Space/GAC®-MAC 2021, London, Canada : Explorer les géosciences à travers le temps et l'espace; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 44, 2021 p. 53 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 2.45 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20210480
PublisherGeological Association of Canada
MeetingGAC-MAC 2021: Geological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting 2021; London, ON; CA; November 1-5, 2021
Mediadigital; on-line
File formatpdf
ProvinceOntario; Quebec
NTS31M/06; 31M/07; 31M/08; 31M/09; 31M/10; 31M/11; 31M/15; 31M/16; 31N/05; 31N/12; 31N/13; 32C/04; 32C/05; 32C/12; 32C/13; 32D; 41O/08; 41O/09; 41O/16; 41P/05; 41P/06; 41P/07; 41P/08; 41P/09; 41P/10; 41P/11; 41P/12; 41P/13; 41P/14; 41P/15; 41P/16; 42A; 42B/01; 42B/08; 42B/09; 42B/16
AreaKirkland Lake; Rouyn-Noranda; Dasserat Lake; Dufresnoy Lake; Duparquet Lake; Chassignolle Lake; Malartic Lake
Lat/Long WENS -82.4167 -77.8333 49.0000 47.2500
Subjectssurficial geology/geomorphology; stratigraphy; Nature and Environment; Science and Technology; landslides; mass wasting; landslide deposits; earthquakes; seismicity; glacial history; deglaciation; glacial lakes; isostatic rebound; sedimentation rates; lake sediments; varves; stratigraphic analyses; Glacial Lake Ojibway; glaciolacustrine sediments; Phanerozoic; Cenozoic; Quaternary
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2021 11 01
AbstractEastern Canada is a large region of recently glaciated terrain where evidence of early postglacial, glacially-induced seismic activity should be abundant, but there are no confirmed examples of early postglacial seismogenic faults. Nevertheless, research within the basin of Glacial Lake Ojibway, which persisted between 10.57-8.47 ka cal BP in northeastern Ontario-western Quebec, revealed mass transport deposits (MTDs) buried at differing stratigraphic levels within the glaciolacustrine sediments throughout the region. Detailed mapping of the sub-bottom deposits at Dasserat, Duparquet, and Dufresnoy lakes, located 24 to 38 km apart, near Rouyn-Noranda, Quebec, identified 26 MTD event horizons of which 15 contain three or more MTDs. High-resolution, relative dating control using varves indicates: that the event horizons span a period of about 450 varve years (between 9.4-8.95 ka cal BP); that one set of identically-aged event horizons is common to each lake; and another set is common to two lakes. The 15 event horizons containing three or more MTDs are interpreted to be evidence of 11 paleoearthquakes of Mw5 or larger. The confidence of each interpretation is weighted from low to high, reflecting the relative strength of the MTD signature in each event horizon (moderate (three to five MTDs) or strong (more than six MTDs)), and evidence of common- or similar-aged MTD signatures at two or more distinctly separate locations. The event horizon with the most numerous and widespread MTDs in each lake formed in the identical varve year 1483 (about 9.1 ka cal BP). These occurrences are part of a regional MTD signature present in other lakes and in subaerial exposures that enclose an area of about 14,600 km2 in northeastern Ontario and western Quebec. This signature is best explained by a strong paleoearthquake of about Mw 7.3. The interpreted paleoearthquakes occurred when early postglacial uplift had diminished moderately, but was still high, compared to mid-Holocene and late Holocene rates. This record, thus, is likely representative of a period of elevated, early postglacial seismicity associated with rapid crustal unloading from the waning of the Laurentide Ice Sheet.
Summary(Plain Language Summary, not published)
This abstract summarizes evidence of a period of elevated earthquake activity that occurred at the time of the retreat of the ice sheet from the most recent glaciation. The evidence is based on mapping ancient landslides buried in the bottom of modern lakes. Evidence of such elevated earthquake activity is important for the design of critical infrastructure, such as nuclear waste repositories.

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