Continuous reflection profiles from the european continental margin in the Bay of Biscay

Abstract

Recordings made with an airgun seismic profiler have revealed a marked difference in the structure of the continental margin on the two sides of the Bay of Biscay. Off western France the outer part of the continental shelf and the continental slope are underlain by stratified sediments reaching thicknesses of at least 1.5 kilometers. Unconformities related to periods when sedimentation extended the continental slope southwestward can be recognized within the succession. On many parts of the slope the original depositional character has been modified by canyon erosion and slumping. The continental shelf off northern Spain appears to be much more complex structurally than that off France with no evidence of the presence of thick unconsolidated or semiconsolidated sediments. There is also no indication of sediments of any appreciable thickness on the northern Spanish continental slope. The steepness of the latter suggests that it is controlled by a series of major faults. The dissimilarity of these two parts of the European continental margin may be attributable to a difference in the amount of sediment transported to the two areas during Tertiary and late Mesozoic times.