Structural Architecture and Evolution of the Southern Atlas Fold and Thrust Belt of Tunisia as Revealed by Field Data, Seismic Reflection Profiles and Cross Section Balancing

Mohamed Gharbi, Nicolas Espurt, Olivier Bellier, and Amara Masrouhi

The structural architecture of the southern Atlas fold-and-thrust belt of Tunisia was investigated using new detailed geologic mapping and cross section balancing, complemented by exploration wells and seismic reflection data. The construction of a regional balanced cross section and seismic reflection data show that the thrust system is characterized by a mixed thick- and thin-skinned tectonic style. The thin-skinned thrusts propagated above the Triassic evaporitic series. The thick-skinned thrusts superimposed on pre-existing structures inherited from the southern Tethyan margin. Field and seismic reflection data show that these inherited structures correspond to E- to NNW-trending normal faults active during the Triassic-Jurassic and Aptian-Albian rift periods. This normal faulting is associated with complex horst and graben systems. During the Cenozoic compression, these faults have been inverted and favored the development E-trending thrust systems such as the Chemsi and Orbata thrusts and NWtrending lateral ramps. Structural inversion started during the late Campanian-Paleocene period and can be correlated with the onset of the convergence between Africa and Eurasia. A second event of shortening occurred in the Serravalian Tortonian and is still active.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013