Structure of the Gulf of Lions (Northwestern Mediterranean Sea): A Review

After a brief review of previous work, mainly related to the results of the deep penetration (ECORS) seismic lines, we present a picture of the Gulf of Lions tectonic framework based on a dense grid of seismic in­ dustrial lines. This region is divided into two zones: a northeastern one where narrow grabens are oriented NE-SW and a southwestern area where large and deep depressions are limited by faults and horsts which trend N-S. The onshore geology indicates that the second zone has been formed during the Late Eocene epoch in relati­ on to the western European graben system, whereas the NE-SW horsts and grabens are Oligocene in age and are connected to the opening of the northwestern Mediterranean basin. Beneath the Tertiary several deep reflections may represent a southward extension of Mesozoic rocks of the southeast basin and some Eocene thrusts. The thrusting surfaces have been reactivated during the sub­ sequent Oligocene rifting. The structure of the Gulf of Li­ ons is replaced in a general geodynamic framework.