The western part of the Gulf of Cadiz: contour currents and turbidity currents interactions

摘要

Recent multibeam bathymetry and acoustic imagery data provide a new understanding of the morphology of the western part of the Gulf of Cadiz. The gulf is under the influence of a strong current, the Mediterranean Outflow Water (MOW). This current is at the origin of the construction of the giant Contourite Depositional System. Canyons and valleys with erosive flanks are observed. Only the Portimao Canyon is presently connected to the continental shelf. Channels occur on the continental shelf but are presently disconnected from the deeper network of channels and valleys. Slumps are localized in steep slope areas. They are caused by oversteepening and overloading, sometimes probably associated with earthquake activity. Slumps transform sharply into turbidity currents, depositing turbidites on the floor of deep valleys. Interaction of the MOW and gravity currents is suggested by the filling of the incisions located on the drifts below the present seafloor, the shifting of valleys and canyons in the direction of the MOW flow inducing an unusual phenomenon of capture of submarine valleys.