ABSTRACT

Architecture and facies distributions of fine-grained fluvial sediments dispersed by oceanic processes are strongly influenced by the magnitude and type of hydrodynamic processes acting on the sediment supply, and by the timing of maximum sediment supply with respect to temporal/seasonal variability in wave-current energy. Rapid and widespread dispersal of fluvial sediment across continental shelves can occur when seasonal maxima of sediment discharge from a fluvial source and wave-current energy are coincident. Resulting fluvialmarine deposits bear little resemblance to classical deltaic facies models. Recent studies of wave-current dispersal of fluvial sediments have established that a newly recognized class of gravity-driven flows, suspended by wave-current turbulence, can occur on continental shelves with gradients <0.7°, and are probably more widespread than previously thought. Because such flows can carry much more sediment mass than can buoyant plumes of suspended sediment, and can move at velocities on the order of cm s^-1, such benthic sediment flows on shelves could represent a significant and previously underestimated transport mechanism for fine sediment across continental shelves.