GEOSCAN, résultats de la recherche


TitreTurbidite deposition on the glacially influenced, canyon-dominated southwest Grand Banks Slope, Canada
AuteurArmitage, D A; Piper, D J W; McGee, D T; Morris, W R
SourceSedimentology vol. 57, 2010 p. 1387-1408,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20090291
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est
Lat/Long OENS -56.0000 -54.5000 45.0000 44.5000
Sujetssédimentation turbiditique; turbidites; canyons sous-marins; milieux sédimentaires; milieux marins; elements glaciaires; glaciation; géologie des dépôts meubles/géomorphologie
Illustrationslocation maps; profiles; tables
ProgrammeLes géosciences à l'appui de la gestion des océans, Aléas géologiques et contraintes à la mise en valeur des ressources extracôtières
Diffusé2010 09 14
Résumé(disponible en anglais seulement)
The deeply dissected Southwest Grand Banks Slope offshore the Grand Banks of Newfoundland was investigated using multiple data sets in order to determine how canyons and intercanyon ridges developed and what sedimentary processes acted on glacially influenced slopes. The canyons are a product of Quaternary ice-related processes that operated along the margin, such as ice stream outwash and proglacial plume fallout. Three types of canyon are defined based on their dimensions, axial sedimentary processes and the location of the canyon head. There are canyons formed by glacial outwash with aggradational and erosional floors, and canyons formed on the slope by retrogressive failure. The steep, narrow intercanyon ridges that separate the canyons are composite morphological features formed by a complex history of sediment aggradation and degradation. Ridge aggradation occurred as a result of mid to late Quaternary background sedimentation (proglacial plume fallout and hemipelagic settling) and turbidite deposition. Intercanyon ridge degradation was caused mainly by sediment removal due to local slump failures and erosive sediment gravity flows. Leve´e-like deposits are present as little as 15 km from the shelf break. At 30 km from the shelf, turbidity currents spilled over a 400 m high ridge and reconfined in a canyon formed by retrogressive failure, where a thalweg channel was developed. These observations imply that turbidity currents evolved rapidly in this slopeproximal environment and attained flow depths of hundreds of metres over distances of a few tens of kilometres, suggesting turbulent subglacial outwash from tunnel valleys as the principal turbidity current-generating mechanism.