GEOSCAN, résultats de la recherche


TitreTurbidite deposition and the development of canyons through time on an intermittently glaciated continental margin: the Bonanza Canyon system, offshore eastern Canada
AuteurLi, G; Piper, D J W; Campbell, D C; Mosher, D
SourceMarine and Petroleum Geology vol. 29, 2012 p. 90-103,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100503
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; numérique; en ligne
ProvinceRégion extracotière de l'est
Lat/Long OENS-52.0000 -45.0000 50.0000 47.0000
Sujetsmilieu sédimentaire; canyons sous-marins; turbidite; courants de turbidite; chenaux; transport des sediments; transport sous-marin; topographie du fond océanique; topographie du fond océanique; géologie marine; sédimentologie
Illustrationslocation maps; profiles; tables; stratigraphic correlations; photographs
ProgrammeLa géoscience pour les développements extracôtiers de la côte est, Géoscience en mer
Résumé(disponible en anglais seulement)
Bonanza Canyon is a complex canyon system on the slope from the intermittently glaciated Grand Bank on the south side of Orphan Basin. A 3D seismic reflection volume, 2D high-resolution seismic reflection profiles and ten piston cores were acquired to study the evolution of this canyon system in relation to glacial processes on the continental shelf and the effects of different types of turbidity currents on the development of deep water channels. Mapped reflector surfaces from the 3D seismic volume show that the Bonanza Canyons developed in a depression created by a large submarine slide of middle Pleistocene age, coincident with the onset of glacigenic debris flows entering western Orphan Basin. Two 3e5 km wide, flat-floored channels were cut into the resulting mass-transport deposit and resemble catastrophic glacial meltwater channels elsewhere on the margin. Both channels subsequently aggraded. The eastern channel A became narrower but maintained a sandy channel floor. The western channel, B, heads at a spur on the continental slope and appears to have been rather passively draped by muds and minor sands that have built 1500-m wave length sediment waves.
Muddy turbidites recorded by piston cores in the channel and on the inter-channel ridges are restricted to marine isotope stage (MIS) 2 and were deposited from thick, sheet-like, and sluggish turbidity current derived from western Orphan Basin that resulted in aggradation of the channels and inter-channel ridges. Sandy turbidites in channels and on inner levees were deposited throughout MIS 2 e3 and were restricted to the channels, locally causing erosion. Some coincide with Heinrich events. Channels with well-developed distributaries on the upper slope more readily trap the sediments on Grand Bank to form sandy turbidity currents. Channel B dominated by muddy turbidity currents has wide and relatively smooth floor whereas channel A dominated by sandy turbidity currents has a sharp geometry.