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TitreChanges in submarine channel morphology and slope sedimentation patterns from repeat multibeam surveys in the Fraser River delta, western Canada
AuteurHill, P R
SourceInternational Association of Sedimentologists, Special Publication vol. 44, 2012 p. 47-70,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20070460
ÉditeurJohn Wiley & Sons, Ltd
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS-123.4000 -123.3167 49.1167 49.0667
Sujetsbathymétrie; levés géophysiques; caractéristiques sous-marines; cônes sous-marins; chenaux; courants de turbidite; courants de fond; sédiments de fond; formation de pentes; stabilité des pentes; sedimentation; géologie marine; géophysique
Illustrationslocation maps; tables; profiles
ProgrammeLes géosciences à l'appui de la gestion des océans
Diffusé2013 01 03
Résumé(disponible en anglais seulement)
The Strait of Georgia is a forearc basin located between the subducting Juan de Fuca plate and the volcanic arc of the Coast Mountains. The predominant source of sediment to the basin is the Fraser River, which has formed a large Holocene delta. Multibeam surveys of the main distributary channel mouth and delta slope confirm the presence of a submarine channel - fan system consisting of two main tributary networks with steep headwalls on the upper slope, a single main channel reach, partially constricted by a bedrock or till ridge, channel levees and a base-of-slope fan. At the base of slope, the main submarine channel dies out and erosional flute forms are observed. The fan consists of a broad area of high backscatter intensity and smaller ephemeral channels. Repeat multibeam surveys show that the upper slope is characterized by high rates of sediment accumulation and small-scale slope failure on an inter-annual time scale. Erosional features include headwall flow failures and retrogressive intra-channel erosion. Repeat surveys also indicate that sediment accumulates within the upper reaches of the tributary slope channels in the form of retrogradationally-stacked depositional wedges. These are interpreted to be formed by short-lived turbidity currents originating from density underflows created when dredge waste impacts the seafloor. The retrogradational stacking is thought to be a response to a feedback process whereby each wedge, deposited at the critical gradient for ignition, reduces the gradient for the next flow. The non-channelled portion of the delta slope adjacent to the distributary channel is characterized by sediment waves which repeat surveys show to be migrating up-slope. It is suggested that this is evidence for unconfined turbidity currents.