The deep structure of Gorringe Bank (NE Atlantic) and its surrounding area

Abstract

The structure and origin of the disturbed oceanic area southwest of Cape São Vicente (south Portugal) is still a matter of debate. What are the reasons for such a huge relief and for the high positive free-air anomaly? To go further in the understanding of this atypical region, the deep structure has been investigated by means of 3-D gravity modelling, taking into account other geophysical and geological information such as seismic reflection data. The results clearly show that all topographic highs are associated with shallow Moho, and are consequently not isostatically balanced. Gorringe Bank is shown to be strongly asymmetrical and to be associated with a major fracture within the lithosphere. Considering the geodynamical context of this area the mechanical equilibrium could be due to a distribution of vertical stresses; an estimation of the required stresses is given showing no major evidence that this is impossible.