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TitreThe influence of turbidity currents and contour currents on the distribution of deep-water sediment waves offshore eastern Canada
AuteurNormandeau, A; Campbell, D C; Cartigny, M J B
SourceSedimentology 2018 p. 1-22, https://doi.org/10.1111/sed.12557
Année2018
Séries alt.Ressources naturelles Canada, Contribution externe 20170327
ÉditeurWiley
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1111/sed.12557
Mediapapier; en ligne; numérique
Formatspdf; html
ProvinceRégion extracotière de l'est; Nouvelle-Écosse
SNRC10
Lat/Long OENS -58.7500 -56.2500 43.2500 41.5000
Sujetsmarges continentales; talus continental; sédiments marins; dépôts de glissement de terrain; glissements; courants de turbidite; courants; contourites; régions extracôtières; configurations lit; antidunes; milieu sédimentaire; cycles sédimentaires; modèles sédimentaires; bathymétrie; interprétations géophysiques; levés acoustiques marins; sonar latéral; interpretations sismiques; morphologie; distribution des sédiments; regimes d'écoulement; vitesses de fluage; érosion; sedimentation; caractéristiques sous-marines; canyons sous-marins; chenaux; carottes de sédiment marin; carottages par piston; datation radiométrique; datation au radiocarbone; géologie marine; géologie des dépôts meubles/géomorphologie; sédimentologie; géophysique; stratigraphie; géochronologie; Phanérozoïque; Cénozoïque; Quaternaire
Illustrationslocation maps; geoscientific sketch maps; tables; seismic profiles; bathymetric profiles; geophysical images; lithologic sections; plots; geophysical profiles; schematic models; schematic representations
ProgrammePreparation of a submission for an extended continental shelf in the Atlantic and Arctic Oceans under UNCLOS, Délimitation du plateau continental du Canada en vertu de la Convention des Nations Unies sur le droit de la mer (UNCLOS)
Diffusé2018 11 01
Résumé(disponible en anglais seulement)
Sediment waves are commonly observed on the sea floor and often vary in morphology and geometry according to factors such as seabed slope, density and discharge of turbidity currents, and the presence of persistent contour currents. This paper documents the morphology, internal geometry and distribution of deep-water (4000 to 5000 m) bedforms observed on the sea floor offshore eastern Canada using high-resolution multibeam bathymetry data and seismic stratigraphy. The bedforms have wavelengths of >1 km but fundamentally vary in terms of morphology and internal stratigraphy, and are distinguished into three main types. The first type, characterized by their long-wavelength crescentic shape, is interpreted as net-erosional cyclic steps. These cyclic steps were formed by turbidity currents flowing through canyons and overtopping and breaching levées. The second type, characterized by their linear shape and presence on levées, is interpreted as net-depositional cyclic steps. These upslope migrating bedforms are strongly aggradational, indicating high sediment deposition from turbidity currents. The third type, characterized by their obliqueness to canyons, is observed on an open slope and is interpreted as antidunes. These antidunes were formed by the deflection of the upper dilute, low-density parts of turbidity currents by contour currents. The modelling of the behaviour of these different types of turbidity currents reveals that fast-flowing flows form cyclic steps while their upper parts overspill and are entrained westward by contour currents. The interaction between turbidity currents and contour currents results in flow thickening and reduced sediment concentration, which leads to lower flow velocities. Lower velocities, in turn, allow the formation of antidunes instead of cyclic steps because the densiometric Froude number (Fr') decreases. Therefore, this study shows that both net-erosional and net-depositional cyclic steps are distributed along channels where turbidity currents prevail whereas antidunes form on open slopes, in a mixed turbidite/contourite system. This study provides insights into the influence of turbidity currents versus contour currents on the morphology, geometry and distribution of bedforms in a mixed turbidite-contourite system.
Résumé(Résumé en langage clair et simple, non publié)
La présence de vagues des sables au large de la Nouvelle-Écosse nous a permis de modéliser le comportement des courants de turbidité s'écoulant sur la pente continentales.
GEOSCAN ID306432