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TitleEarly postglacial faulting of glaciolacustrine sediments at Round Lake, Ontario, Canada
AuthorBrooks, G RORCID logo; Pugin, A J -M
Source10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology PATA, Hornitos, Chile, November 2021, short abstracts digital volume; 2020 p. 14 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 17.8 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20190338
Meeting10th INQUA Workshop on Active Tectonics, Paleoseismology and Archaeoseismology; Hornitos; CL; November 2021
Mediaon-line; digital
File formatpdf
AreaRound Lake
Lat/Long WENS -80.0325 -80.0322 48.1722 48.1719
Subjectssurficial geology/geomorphology; stratigraphy; Nature and Environment; Science and Technology; glacial history; deglaciation; glacial lakes; geological history; faulting; depositional history; seismicity; earthquakes; geophysical surveys; acoustic surveys; seismic surveys, lake; seismic profiles; scarps; stratigraphic analyses; landslide deposits; mass wasting; Canadian Shield; Western Quebec Seismic Zone; glaciolacustrine sediments; colluvial and mass-wasting deposits; Phanerozoic; Cenozoic; Quaternary
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2020 12 18
AbstractRound Lake, ~12 km2 and up to 30 m deep, is located in an intracratonic setting on the Canadian Shield, northeastern Ontario, Canada, about 180 km northwest of the Western Quebec Seismic Zone. Within a ~0.5 by 1.8 km area of the lake sub-bottom, acoustic and hammer seismic surveys revealed multiple, low-angled, normal faults that were identified previously as candidates for early postglacial, glacially-induced faulting. As exemplified by three scarps, the faults have apparent throws of about 3 to 6 m and form obvious steps within the glaciolacustrine deposits to the depth of penetration in the acoustic profiles. Unfaulted glaciolacustrine deposits are draped across the faulted sediments, indicating that the faulting occurred in the early postglacial period between 9.8-8.47 ka cal BP, when a large glacial lake inundated the regional landscape. Hammer seismic profiles display signal penetration into the underlying glacial deposits, and reveal that the faulting at many of the scarps is confined to the glaciolacustrine deposits. This characteristic is consistent with the fault surfaces representing the headscarps of shallow mass movements within the glaciolacustrine deposits. Several of the faults are deeper-seated, and may originate below the glaciolacustrine facies, as indicated by i) the apparent extension of the fault planes to the surface of underlying glacial deposits, ii) the identical sub-unit architecture in the head- and footwalls, and iii) the lack of fracturing, back rotation, and disruption to the headwall sub-units, which would be indicative of displacement by a mass movement(s). Lack of penetration of the acoustic or hammer seismic signals to bedrock does not allow determining whether this deeper-seated faulting is associated with bedrock faulting.
Summary(Plain Language Summary, not published)
This abstract summarizes the characteristics of faulted sediments in Round Lake, Ontario, for a conference presentation. The presentation will assess whether the faulted sediments are the product of earthquake shaking, and 2) whether the faulting is the surface expression of an earthquake rupture of the underlying bedrock.

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