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TitleAssessment of a seismo-neotectonic origin for the New Liskeard-Thornloe scarp, Timiskaming Graben, northeastern Ontario
AuthorBrooks, G RORCID logo; Pugin, A J -M
SourceCanadian Journal of Earth Sciences vol. 57, no. 2, 2019 p. 267-274,
Alt SeriesNatural Resources Canada, Contribution Series 20180406
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf
NTS31M/03; 31M/04; 31M/05; 31M/06; 31M/11; 31M/12; 31M/13; 31M/14
AreaLake Timiskaming
Lat/Long WENS -80.0000 -79.0000 48.0000 47.0000
Subjectstectonics; structural geology; stratigraphy; surficial geology/geomorphology; geophysics; Nature and Environment; Science and Technology; bedrock geology; structural features; faults; grabens; landforms; scarps; tectonic history; glacial history; deglaciation; glacial lakes; water levels; postglacial deposits; landslide deposits; glacial deposits; morphology; bedrock topography; geophysical surveys; seismic surveys; coastal erosion; tectonic setting; stratigraphic analyses; remote sensing; photogrammetric surveys; New Liskeard-Thornloe Scarp; Timiskaming Graben; Timiskaming East Shore Fault; anthropogenic deposits; colluvial and mass-wasting deposits; lacustrine sediments; glaciolacustrine sediments; Digital elevation data; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geoscientific sketch maps; photographs; seismic profiles
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2019 05 13
AbstractTo test an inference that the New Liskeard-Thornloe scarp (NLTS), Timiskaming graben, Ontario, is a deglacial-postglacial seismo-neotectonic fault, this study collected shallow geophysical data along lines 7.2, 0.28 and 0.52 km long, located on three roads crossing the middle portion of the scarp. Data revealed a valley subsurface composed of bedrock (seismic unit a), glaciolacustrine-lacustrine deposits (units b to f), mass movement deposits (units ls 1 to ls 3), wave-worked sediments, mass wasting deposits and/or artificial fill (unit g), and a minor occurrence of roadfill (unit h). The bedrock surface exhibits only minor undulations in the area underlying the scarp, indicating that the scarp morphology is unrelated to the underlying bedrock topography. Parallel reflectors in glaciolacustrine seismic units b and c conformably overlie the minor bedrock undulations and there is an absence of disturbed or offset zones within the reflectors underlying the scarp. This lack of disturbance or offset provides strong evidence that the scarp is not the product of deglacial-postglacial seismo-neotectonic faulting. The erosive truncation of glaciolacustrine seismic units d and e indicate that the scarp is an erosive feature cut into the glaciolacustrine deposits. It likely is a bluff formed by shoreline erosion, as is consistent with a geomorphic setting previously inundated by a large glacial lake and subsequent recessional lake stages. The non-fault origin for the NLTS limits the northern extent of the hypothesized Timiskaming East Shore fault to within the Lake Timiskaming basin and hence constrains estimates of maximum rupture length.
Summary(Plain Language Summary, not published)
It has been inferred by some researchers that the scarp forming the eastern side of Wabi Creek valley, Timiskaming graben, Ontario, is an active fault, which experienced relatively recent fault movement. This study tested that hypothesis by collecting geophysical images of the subsurface underneath the scarp. Our results clearly show that there is no evidence of faulting beneath the scarp and that the scarp likely is an erosional bluff eroded along the shoreline of lake that had previously flooded Wabi Creek valley.

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