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TitreSeabed disturbance and bedform distribution and mobility on the storm-dominated Sable Island Bank, Scotian Shelf
AuteurLi, M Z; King, E L; Prescott, R H
SourceInternational Association of Sedimentologists, Special Publication vol. 44, 2012 p. 197-228
Séries alt.Secteur des sciences de la Terre, Contribution externe 20070505
Documentpublication en série
ProvinceRégion extracotière de l'est
Lat/Long OENS -61.5000 -60.0000 44.5000 43.5000
Sujetstopographie du fond océanique; topographie du fond océanique; bathymétrie; configurations lit; déplacement de la configuration lit; transport des sediments; transport sous-marin; caractéristiques sous-marines; géologie marine; géophysique
Illustrationslocation maps; profiles; plots; sonograms
ProgrammeLes géosciences à l'appui de la gestion des océans, Aléas géologiques et contraintes à la mise en valeur des ressources extracôtières
Résumé(disponible en anglais seulement)
Regional bathymetry maps, sidescan sonar and multibeam bathymetric surveys, sediment samples, and predictions of seabed disturbance are integrated to characterize the distribution, metrics, and mobility of bedforms on the storm-dominated Sable Island Bank, Scotian Shelf. Sand ridges cover most of Sable Island Bank with a trend of decreasing size from west to east and from offshore to onshore. Shoreface sand ridges and sand waves are active on a yearly basis on the bank top. Portions of sand ridges can migrate up to 40m annually both to the east and west, but the mode migration is near zero. The nearshore and inner bank is exposed to high waves and strong storm-induced currents and is characterized by shoreface ridges with superimposed sand waves, megaripples, and large wave ripples. All bedforms are active in this setting. The midand outer-bank experiences intermediate to moderately low energy, and is characterized by moribund offshore ridges with superimposed intermittently active sand waves and active megaripples. The occurrence of large wave ripples is decreased, while periodically active sand ribbons and specks (circular shell beds) become more abundant. The bank edge and upper slope are subject to very low energy and are generally devoid of bedforms with the exception of occasional ribbons. Numerical model predictions demonstrate that hydrodynamic forcing and sediment mobilization are strongly controlled by waves and wave-current interaction during winter storms. Tidal currents alone can cause sediment mobilization at least once a year over 36% of the bank area while wave action affects 71%. The combined action of waves and tides affects 93% of the bank. Based on the relationship between seabed disturbance magnitude and bedform distribution and mobility, seven new bedform zones with unique bedform association, energy level, and mobility characteristics are proposed.