Messinian salt deformation offshore Algeria: the role of crustal tectonics and sedimentary load on the observed geometries

The Algerian margin (Western Mediterranean) reactivated in compression 8 My ago due to the convergence between Africa and Eurasia, and is nowadays subjected to a strain regime of several mm/y, resulting in destructive earthquakes as the M 6.8 Boumerdès event in 2003.

The MARADJA I seismic reflection data acquired in 2003 allowed to image in detail the Messinian Salinity Crisis Mobile Unit (mostly halite) and its brittle sedimentary overburden offshore Algiers. Particularly interesting in the area are the salt-related geometries and the presence of crustal tectonic structures -consequence of the compressional setting of this margin- that created an uplifted plateau offshore Algiers (Déverchère et al., 2005; Domzig et al., 2006). The comparison with the MARADJA II (2005) data offshore Béjaia allowed to better distinguish between the regional trends and the local peculiarities.

Together with the general analysis of the structures due to the salt tectonics, as well as the influence of crustal tectonics on salt deformation on the Algerian margin, this study is particularly focused on the geometry, position and triggering processes of a localized minibasins field, which started to form very early –possibly before the end of the Messinian Salinity Crisis- and is still active nowadays. This minibasins field position corresponds to both the external limit of a sedimentary body and the western limit of the previously mentioned uplifted plateau, raising the question of the relative influence of these two contributing factors in the formation of the minibasins. The analogue modelling contribution in this analysis is crucial.