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TitleStorm-induced turbidity currents triggered in the absence of shelf sediment supply
AuthorNormandeau, AORCID logo; Bourgault, D; Neumeier, U; Lajeunesse, P; St-Onge, G; Gostiaux, L; Chavanne, C
SourceISC2018 - 20th International Sedimentological Congress, abstract volume; 2018 p. 1
Alt SeriesNatural Resources Canada, Contribution Series 20180228
MeetingISC2018 - 20th International Sedimentological Congress; Québec, QC; CA; August 13-17, 2018
DocumentWeb site
Mediapaper; digital
File formatpdf
ProvinceQuebec; Eastern offshore region
NTS22G/03; 22G/04; 22G/05; 22G/06
AreaPointe-des-Monts; St. Lawrence River
Lat/Long WENS -67.6500 -67.0667 49.3000 49.0333
Subjectsmarine geology; surficial geology/geomorphology; sedimentology; geophysics; marine environments; turbidity currents; storms; continental shelf; submarine canyons; geophysical surveys; acoustic surveys, marine; side-scan sonar; bathymetry; sedimentary structures; bedforms; cyclic processes; sediment dispersal; dispersal patterns; temperature
ProgramPublic Safety Geoscience Marine Geohazards
Released2018 08 01
AbstractThe monitoring of turbidity currents allows a better understanding of their behaviour and timing in relation to triggering events. The triggers of turbidity currents often remain hypothetical since very few studies have directly observed them. These triggers are nearly always inferred, even when monitoring is present. In this study, the Pointe-des-Monts submarine shelf canyons were monitored using Acoustic Doppler Current Profilers (ADCPs) and repeated high-resolution swath bathymetry mapping. Repeated mapping revealed that crescent-shaped bedforms, interpreted as cyclic steps, migrated upslope during the last 10 years, despite the absence of sediment on the shelf or river inflow in the region. During the winter of 2017, an intense turbidity current, with velocities reaching 2 m s-1, was recorded and appears to be responsible for the migration of cyclic steps. This turbidity current was coincident with one of the greatest storm of the year that generated 3.8 m waves along the coastline of the region. The turbidity current temperature in combination with repeated seafloor mapping suggest that it was triggered at depths of > 100 m and that it is not attributed to a canyon-wall failure. Three other turbidity currents, albeit weaker, were also triggered during storms during the winter of 2016-2017. These results demonstrate that storms can possibly trigger turbidity currents at deeper water depths than the shelf, although the exact process by which sediments are put in suspension remains enigmatic.
Summary(Plain Language Summary, not published)
Turbidity currents were recorded in the Pointe-des-Monts canyons using current profilers and were shown to be triggered during major storms affecting eastern Canada.

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