Hydrology, morphology and sedimentology of the Campos continental margin, offshore Brazil

Slope sand deposits have accumulated from at least the Neogene to the Present on the southeastern Brazilian continental margin (Campos Basin area). This region shows sand accumulations concentrated on the upper portion and on the base of the continental slope with a middle to lower slope bypass zone. A synthesis of preliminary results, supported by recent cores, high-resolution geophysical surveys, geotechnical investigations and environmental research, is presented and permits a preliminary analysis of the sedimentological mechanisms operational in this area. These point toward a temporal and spatial multiscale set of phenomena responsible for sand deposits. At any sea-level stand these deposits are dependent on: (1) a suitable sediment source; (2) offshelf transport mechanisms; (3) a morphostructural and hydrodynamic context responsible for the deposition of these sands in the upper portion of continental slopes. The proposed scenario of depositional processes concerns: (1) a set of hydrological processes such as surface currents and counter-currents, waves, tides and eddies with sufficient energy to form submarine sand dune fields at the outer shelf; (2) the offshelf export of this sediment under a combined action of spillover, internal waves, eddies 'seafloor polishing effect' and gravity processes (turbidity currents); and (3) the slope sand deposits and their distribution controlled by the action of contour currents, mass movements and the morphological context, such as canyons, gullies or scarps. (C) 1998 Elsevier Science B.V. All rights reserved.