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TitleMicrofossils suggest separate triggers for mass transport deposits in two lakes within the Western Quebec Seismic Zone, southwest Quebec, Canada
AuthorAlderson, A; Brooks, G RORCID logo; McCarthy, F M G; Boyce, J I; Hoggar, J; Esmaeilzadeh, A
SourceGSA 2020 Connects Online; Geological Society of America, Abstracts With Programs vol. 52, no. 6, 165-10, 2020 p. 1, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210418
PublisherGeological Society of America
MeetingGeological Society of America Annual Meeting 2020; October 25-28, 2020
Mediadigital; on-line
File formathtml; pdf
AreaLac de l'Argille; McArthur Lake
Lat/Long WENS -80.0000 -73.0000 48.0000 44.0000
Subjectssurficial geology/geomorphology; paleontology; stratigraphy; geophysics; geochemistry; Science and Technology; Nature and Environment; lake sediments; landslide deposits; micropaleontology; microfossils; palynology; palynomorphs; pollen; landslides; mass wasting; seismicity; seismic risk; earthquakes; earthquake risk; stratigraphic analyses; geophysical surveys; acoustic surveys; lake sediment cores; x-ray fluorescence analyses; depositional history; Western Quebec Seismic Zone; Champlain Sea Deposits; testate amoebae; Plankton; Picea; Pinus resinosa; Phanerozoic; Cenozoic; Quaternary
ProgramPublic Safety Geoscience Nuclear Waste Management Organization
Released2020 10 01
AbstractReconstructing regional earthquake history is important for assessing earthquake hazards, especially in intraplate regions with short historic records and infrequent, but potentially high-magnitude earthquakes. A useful method of identifying paleoseismic events is through the identification of multiple mass transport deposits (MTDs) at a common stratigraphic level in a lake basin. Where such signatures are present in separate lake basins, and it can be established that they are the same age, a paleoearthquake may be the best explanation for a coeval trigger. Sub-bottom acoustic profiling revealed multiple stratigraphic levels of MTDs within early postglacial Champlain Sea deposits preserved within the basins of Lac de l'Argille and McArthur Lake, located about 25 km apart, in southwest Quebec. The sediment cores recovered at the sites overlying the two stratigraphically youngest MTDs in each lake were CT scanned, underwent ITRAX XRF analysis, and subsampled for microfossils and pollen. Microfossils (palynomorphs and testate amoebae) from the MTDs show re-sedimentation of nearshore planktonic taxa and into the deep basins of both lakes, and confirm the mass transport origin of the deposits. The pollen record leading into the MTD in McArthur Lake is rich in Picea and Pinus resinosa, indicating deposition between 11-13 ky BP, while the equivalent record overlying the Lac de l'Argille MTD is rich in Pinus strobus pollen, placing deposition between 8-10 ky BP. These two mass transport events thus are of distinctly different ages and cannot be attributed to a coeval trigger. This study demonstrates the importance of dating MTDs from relatively close lake basins, and not inferring a coeval trigger based on similar stratigraphic locations in sub-bottom profile records.
Summary(Plain Language Summary, not published)
The abstract summaries the investigation of two nearby lakes to see if a set of ancient underwater landslides in each lake is the same age. Turns out they are of difference ages, and thus are not the evidence of a common triggering like a significant earthquake.

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