Giant depressions on Atlantic continental margins: Relationship with diapirs

Abstract

Several giant circular-elliptical depressions have been analyzed in the continental margins off North Iberian (NICM) and West Africa (WACM) by means of multibeam bathymetric data and seismic reflection profiles. Their long axes vary between 2 and 4.7 km, the width axis between 2 and 3.5 km and their reliefs between 40 and 370 m. Depressions are slightly elliptical with eccentricity index between 0.73 and 0.9. They are partially filled by sediments producing different V and U bathymetric crosssections. The Burato Ergap depression in the NICM and the Twin Pools depressions in the WACM occur overlying diapirs. Burato Ergap depression is originated as a collapse structure related to underlying diapiric mobility. Twin Pools depressions seem to represent seafloor reworking by the action of deep sea bottom currents interacting with and adjacent diapiric ridge on the seafloor