The Southern Atlas Front in Tunisia and its foreland basin: Structural style and regional-scale deformation

International audienceSurface and subsurface data together with balanced cross-sections are used to emphasize the structural style and regional-scale deformation of the Southern Atlas Front in Tunisia and its foreland basin. This E–trending shaped belt reflects successive tectonic events. Mixed thick- and thin-skinned structural style characterizing this belt is defined by shallow thrusts rooted down into deep E–trending basement thrusts with major decollement level located within Triassic salt. A NW–trending system is also recognized in the front and particularly responsible for the belt's curved shape, which probably acts as transfer areas between the wide-ranging E–trending major structures. The intermediate areas are characterized by salt tectonics probably active during Jurassic and Lower Cretaceous, in response to active synsedimentary normal faults and differential sedimentation loading. The shortening amount varies and decreases from West to East and from North to South: ~7.45% in the West, ~3.3% in west-central part, ~2% in the central area to insignificant (~1.4%) in the east. From north to south, the Northern Chotts Range narrow zone accommodates overall the Cenozoic shortening with ~6.95% and less than 1% in the Chotts region. This variation coincides with the pre-Cenozoic basin's architecture acquired during Mesozoic Tethyan evolution, which generates the main Jurassic E–trending Chotts basin. Inside this basin, distributary sub-basins are formed in relation with NW–trending faults active during the Cretaceous period. The Chotts basin appears, therefore, as Mesozoic rift rollover structure well-preserved in the front of the belt. The compilation of data suggests that the Front of the southeasternmost end of the Atlassic domain is distinguished by the reactivation of inherited fault systems acting during alpine orogeny as major southward thrusts. The foreland shows a structural singularity to be formed by a preserved almost unmodified and well exposed large Mesozoic rollover structure