GEOSCAN, résultats de la recherche


TitreMulti-faceted investigation of sediment and bedform mobility on Sable Island Bank, Scotian Shelf
AuteurLi, M Z; King, E L
SourceGAC-MAC-CSPG-CSSS Halifax 2005, building bridges - across science, through time, around the world: abstracts/AGC-AMC-SCGP-SCSS Halifax 2005, Jeter des ponts entre les disciplines scientifiques, les époques, et unifier le monde : recueil des résumés; AGC-AMC-SCGP-SCSS Reunion conjoint, Receuil des Résumés vol. 30, 2005 p. 113
Séries alt.Secteur des sciences de la Terre, Contribution externe 2004359
RéunionGAC/MAC/CSPG/CSSS Joint Annual Meeting; Halifax; CA; mai 15-18, 2005
Documentpublication en série
ProvinceRégion extracotière; Nouvelle-Écosse
Lat/Long OENS -63.0000 -59.0000 44.0000 42.0000
Sujetsconfigurations lit; transport des sediments; sédiments marins; dispersion des sédiments; propriétés du sédiment; bathymétrie; sables marins; dunes hydrauliques
ProgrammeLes géosciences à l'appui de la gestion des océans
Résumé(disponible en anglais seulement)
The distribution and migration of bedforms directly affect the cost and safety of offshore seabed installations. Sediment type and mobility are also important controlling factors of benthos diversity and habitat distribution in marine environments. Thus the understanding of
sediment and bedform mobility forms an important part of the geoscience knowledge for oceans management. A multi-faceted
investigation, using sampling/coring, repetitive survey, seabed instrumentation measurement and modelling techniques, was conducted
to assess the sediment and bedform distribution and mobility on the Sable Island Bank (SIB), Scotian Shelf. Digital compilation of Canadian Hydrographic Services bathymetry data significantly updated the distribution and characteristics of sand ridges on SIB. Analysis of multibeam data from selected sites has shown that the majority of sand ridges on this bank are nearly symmetrical and their scale steadily decreases from west to east and from offshore to nearshore. As a result of the mobility of smaller superposed bedforms, sand ridges migrate at very low rates but to opposite directions over short periods of time to result in effectively no net migration in longer time spans. Besides the large-scale sand ridges and sand waves, mid-sized bedforms such as megaripples, ribbons, and large-wave ripples widely occur in various depths on the bank and are superposed on the sand ridges as well. Targeted sampling and compilation of existing and recent geophysical surveys provided new insights into their distribution, metrics and sediment composition. In contrast to the quasi-stable sand ridges, initial assessment of serial surveys and in situ measurement data suggest that these mid-sized bedforms can be reactivated more frequently, possibly with each typical winter storm, even at relatively deep outer-bank water depths. Seabed instrumentation packages were deployed over fine sand on the southeastern bank and over coarse sand in a sand ridge trough on the
western bank to monitor the nearbed dynamics, sediment transport potential, and the development and mobility of small- to mid-sized
bedforms at these sites. Bedforms ranging from current ripples, through wave ripples to large-wave ripples were observed under moderate tidal currents and storm conditions. Bedload transport as well sand suspension occurred in both deployments, even over the coarse sand at the western bank site. These in situ data were also used in assessing the mobility of mid-sized bedforms that exist in the vicinity of the deployment sites.