The Sea

Over the past decade new evidence from field studies has started to change our understanding of shelf sedimentary processes that control the fate of muddy sediment (i.e., particle diameters <64 mm). These processes are highlighted in this paper, with a focus both on the spatial processes that control the transfer of sediment across shelf subenvironments (inner shelf to mid shelf to slope) and on the temporal variability associated with transfer processes and burial of sediment. The studies represent a mosaic of results from several continental shelf settings that have been important for expanding our knowledge of shelf sediment dynamics. Ultimately, they may engender additional physical concepts to be incorporated into shelf sedimentation models. The relevant processes include:

the formation of gravity-driven density flow, or fluid mud, and its role in sediment transport;

across-shelf transport mechanisms, with particular attention to the linkages between different shelf subenvironments, i.e., the role of the inner shelf in creating the mid-shelf deposit, and the role of the mid-shelf deposit on offshelf transport by nepheloid layers (zones within the water column with diffuse clouds of increased sediment concentration) and gravity-driven density flows in canyons;

longer-term (time scales greater than weeks) mechanisms impacting annual and interannual variability of sediment flux, and the sedimentological impact of the relative timing between sediment supply and coastal-ocean energetics.