| Titre | The influence of turbidity currents and contour currents on the distribution of deep-water sediment waves offshore eastern Canada |
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| Auteur | Normandeau, A ;
Campbell, D C; Cartigny, M J B |
| Source | Sedimentology 2018 p. 1-22, https://doi.org/10.1111/sed.12557 |
| Image |  |
| Année | 2018 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20170327 |
| Éditeur | Wiley |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1111/sed.12557 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Région extracotière de l'est; Nouvelle-Écosse |
| SNRC | 10 |
| Lat/Long OENS | -58.7500 -56.2500 43.2500 41.5000 |
| Sujets | marges 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 |
| Illustrations | cartes de localisation; cartes géolscientiques généralisées; tableaux; profils sismiques; profils bathymétriques; images géophysiques; coupes lithologiques; graphiques; profils géophysiques;
modèles schématiques; représentations schématiques |
| Programme | Délimitation du plateau continental du Canada en vertu de la Convention des Nations Unies sur le droit de la mer (UNCLOS) |
| Diffusé | 2018 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. |
| Sommaire | (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 ID | 306432 |
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