Abstract

The Mesozoic and Cenozoic outcrops of the central and meridional Atlas of Tunisia have been studied by structural, biostratigraphic, and sedimentologic approaches. We extend these studies to the subsurface, employing seismic and well data addressing structures, sequence stratigraphy, and hydrocarbon potential. The basin structures are related to strike-slip fault systems associated with Triassic evaporites. Mesozoic sedimentary sections in the areas of the Gafsa, Sidi Ali Ben Oun, Sidi Aïch, and Majoura blocks were studied by an integrated seismic sequence stratigraphic and tectonic approach calibrated to wells and surface geologic controls. We identified tectonic corridors where Upper Triassic evaporites intruded younger Mesozoic rocks beginning in the Jurassic. The organization of the tectonic blocks is characterized by the distribution of subsiding basin zones of graben and rim synclines and resistant areas of platforms. Triassic intrusions induced by the strike-slip movements formed salt pillows and domes that accentuate the border elevations between the rim syncline depocenters and the platforms. Mesozoic sequence deposits are distributed along the flanks of the basin-platform borders according to lowstand prograding downlap systems tracts overlapped by aggrading and retrograding onlap and toplap deposits. The time-space distribution of the systems tract deposits indicates the possibility of formation of Triassic, Jurassic, and Cretaceous carbonate and sandstone prograding turbidites, reefs, structural and stratigraphic pinch-outs, and unconformities in the flanks of salt domes and basins. The geometry and distribution of reservoir and seal systems tracts permit the consideration of new Triassic, Jurassic, and Cretaceous combined stratigraphic and structural hydrocarbon traps around the basins and the platforms. This is a new tectonic model of the central Atlas of Tunisia that shows new potential objectives and traps.

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