GEOSCAN Search Results: Fastlink


TitleEvidence of late glacial paleoseismicity from submarine landslide deposits within Lac Dasserat, northwestern Quebec, Canada
AuthorBrooks, G R
SourceQuaternary Research (New York) vol. 86, issue 2, 2016 p. 184-199,
Alt SeriesEarth Sciences Sector, Contribution Series 20150417
Mediapaper; on-line; digital
RelatedThis publication is related to Brooks, G R; (2016). A varve record of Lake Ojibway glaciolacustrine deposits from Lac Dasserat, northwestern Quebec, Canada, Geological Survey of Canada, Open File 8089
File formatpdf
AreaLac Dasserat; Rouyn-Noranda
Lat/Long WENS -79.4167 -79.3333 48.2500 48.1667
Subjectschronostratigraphy; submarine features; landslide deposits; varves; deglaciation; cores; glacial lake Obijway; paleoearthquakes; seismo-stratigraphy; intracratonic
Illustrationslocation maps; seismic profiles; diagrams; core logs; plots; tables
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractAn integrated seismo- and chronostratigraphic investigation at Lac Dasserat, northwestern Quebec, identified 74 separate failures within eight event horizons. Horizons E and B, and H and G have strong or moderately-strong multi-landslide signatures, respectively, composed of 11-23 failures, while horizons F, D, C, and A have minor landslide signatures consisting of a single or pair of deposit(s). Cores collected at six sites recovered glacial Lake Ojibway varve deposits that are interbedded with the event horizons. The correlation of the varves to the regional Timiskaming varve series allowed varve ages or ranges of varve ages to be determined for the event horizons. Horizons H, G, E, and B are interpreted to be evidence of paleoearthquakes with differing levels of interpretative confidence, based on the relative strength of the multi-landslide signatures, the correlation to other disturbed deposits of similar age in the region, and the lack or possibility of alternative aseismic mechanisms. The four interpreted paleoearthquakes occurred between 9770 ± 200 and 8470 ± 200 cal yr BP, when glacial Lake Ojibway was impounded behind the Laurentide Ice Sheet during deglaciation. They probably represent an elevated period of seismicity at deglaciation that was driven by crustal unloading.
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.