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TitleTide-supported gravity flows on the upper delta front, Fraser River delta, Canada
AuthorAyranci, K; Lintern, D G; Hill, P R; Dashtgard, S
SourceMarine Geology vol. 326-328, 2012 p. 166-170,
Alt SeriesEarth Sciences Sector, Contribution Series 20120230
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
AreaFraser River; Fraser River Delta
Lat/Long WENS-123.5000 -123.0000 49.2500 49.0000
Subjectsmarine geology; tides; tidal currents; tidal deltas; tidal deposits; tidal environments; turbidites; flow structures; flow mechanisms; flow regimes; gravity sliding; gravity
Illustrationslocation maps; graphs; plots
ProgramMarine Geohazards, Public Safety Geoscience
AbstractThree anomalous events (AEs) were recorded off the Fraser River, Canada during the freshet of 2008, and are ascribed to quasi-continuous gravity flows. These flows transport warm, low-salinity Fraser River waters to the upper delta front of the Fraser delta to at least 50 m water depth. All flows occurred during the freshet and spring ebbing tide, and were characterized by deposition of fine-grained sand and silt beds with likely high-water contents. These sediments were susceptible to resuspension by the subsequent flood-tide current, producing very high near bed suspended sediment concentrations (SSC) with enough excess density to generate hyper-concentrated flows. Our observations show that these episodic events result from the combination of high river discharge, high SSC, and strong tides, and therefore, are likely to occur on the delta fronts of other large tide-dominated and tide-influenced rivers. In shallow-water basins (< 50 m water depth), these tide-supported gravity flows can affect sediment deposition on both the delta front and prodelta.