GEOSCAN, résultats de la recherche


TitreU.S. and Canadian scientists collaborate in mapping the Georges Bank seabed
AuteurValentine, P C; Todd, B J
SourceSound Waves FY 2013, no. 143, 2012 p. 9-10
LiensOnline - En ligne (HTML)
LiensOnline (Full volume) - En ligne (volume complet) PDF, 1.6 MB
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120306
Documentpublication en série
Mediaen ligne; numérique
Référence reliéeCette publication est reliée les publications suivantes
ProvinceRégion extracotière de l'est
Lat/Long OENS -67.5000 -65.0000 42.5000 41.0000
Sujetstopographie; plate-forme continentale; topographie du fond océanique; levés au sonar; bathymétrie; canyons sous-marins; dépôts glaciaires; sables; graviers; épandage fluvio glaciaire; moraines; glissements de terrain; transport sous-marin; sedimentation; dunes hydrauliques; rides de plage; transport des sediments; directions du transport de la glace; sédimentologie; géologie marine; géologie des dépôts meubles/géomorphologie
Illustrationscross sections; bathymetric imagery
ProgrammeLa géoscience pour les développements extracôtiers de la côte est, Géoscience en mer
Résumé(disponible en anglais seulement)
Georges Bank is a large (42,000 km2) shallow part of the continental shelf offshore of New England that lies in both U.S. and Canadian waters. The seabed is primarily glacially-derived sand and gravel deposited since the last glacial maximum ~20,000 years ago. A series of maps showing the seabed topography of the Canadian portion of Georges Bank and the Fundian Channel has been compiled by geologists Brian Todd and John Shaw of the Geological Survey of Canada (GSC) and Page Valentine of the U.S. Geological Survey. The Canadian portion of the bank was surveyed over two field seasons using multibeam sonar technology. Valentine has conducted research on the U.S. portion of Georges Bank and has previously collaborated with Todd on studies of the Canadian portion of the bank. Todd has led the Canadian effort to map large parts of their continental margin including the Bay of Fundy, German Bank, Browns Bank, and the Georges Bank region. Their mutual research interests have led Todd and Valentine to collaborate in compiling maps of the Canadian portion of Georges Bank using an approach that combines multibeam sonar data, video and photo imagery, sediment sampling, and subbottom seismic profiling. The map series comprises 9 sheets at a scale of 1:50,000 (1 cm on the map represents 500 m on the seabed) that will be released in early 2013.
In all, 13,000 km2 of seabed were mapped in water depths of 42 to over 1000 m. Multibeam bathymetric data show the topography in great detail at a horizontal resolution of 5 to 10 m and a vertical resolution of 10 to 30 cm. The seabed bears the imprint of the last glaciation when sea level was lower and the Laurentide ice sheet covered all of New England and Atlantic Canada. Glacial ice encroached on the northern and eastern margins of Georges Bank and found an outlet to the Atlantic Ocean through the Fundian Channel which bisects Georges Bank and the Scotian Shelf to the north. Moraines and other glacial features on the seabed show the direction of flowing ice, and numerous iceberg keel marks record the breakup (or calving) of glacial ice where glaciers terminated in the ocean. Old shoreline features document rises of sea level following the melting of the regional ice sheet. On the seaward edge of Georges Bank, landslide features indicate the collapse of sediment deposits which contributed to the formation of submarine canyons. Present day features of deformed seabed on the bank edge identify sediments that are susceptible to future slumping and sliding events. Apart from revealing the morphology of the seabed and the recent glacial and post-glacial processes that formed it, these maps provide a framework for further mapping of the geological substrates and environmental processes that characterize the region, for fishery management, and for baseline studies that precede oil and gas development.