Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of lions, western mediterranean

Abstract

The young Messinian salt basin offshore the Gulf of Lions comprises a shallow decollement layer (maximum of 3.6 km deep) that allows the seismic imaging of the subsalt relief and the correlation between the shape of subsalt relief and gravity-driven structures. The subsalt relief reveals a variable morphology below the salt layer, characterized by both convex and concave shapes, indicating the occurrence of radial gravitational gliding at the scale of the entire Gulf of Lions. Radial gravitational gliding is equally illustrated by the distribution of the Messinian salt layer. The salt isopach map shows overthickened salt mass overlying subsalt relief of concave shape, pointing to a pattern of convergent gliding, and areas of salt thinning (over convex shape of subsalt relief) indicating divergent gliding. Radial gravitational gliding is also reflected by salt-related structures. Families of normal transverse faults striking parallel to the regional dip direction attest the control exerted by components of strike-parallel extension over areas of convex shape of subsalt relief, whereas widespread buckle folds overlying concave shape of subsalt relief indicate the occurrence of a convergent pattern of salt migration and associated translational gliding. The Gulf of Lions provides then an interesting geological setting to focus on gravity tectonics as well as a model to correlate mapped salt-related structures with those predicted by analogue models.