Tunisian Transtensive Basins in Tethyan Geodynamic Context and Their Post-Tortonian Inversion

Abstract

Generally, the geological and structural context of Tunisia can be described, from the North to the South, in terms of the structural domains illustrated on Fig. 1: 1. The Alpine zone, composed of the Tellian Atlas, characterized by the stacking of allochthonous units (Jauzein et al., 1965; Biely et al., 1974; Rouvier, 1977; Ben Ferjani et al., 2006; Ould Bagga et al., 2006) and a series of imbricate thrust slices, whose front corresponds to the major Teboursouk overthrust (Zargouni, 1975; Perthuisot, 1978). 2. The diapir zone (DZ), represented by the N050-trending Triassic outcrops of northern Tunisia (Perthuisot, 1978). 3. The Atlasic zone includes the Northern Atlas, the central Atlas, the southernmost Atlas and the North-South Axis. The central Atlas and the Northern Atlas are characterized by a bundle of N040-050 anticlinal folds that are cut orthogonally by a graben system. The southernmost Atlas is made up of E-W folds, inflected towards N060 at their terminations and bounded by the major faults of Gafsa and Negrine-Tozeur striking N120-130 (Zargouni, 1985). The North-South Axis comprises a folded and faulted zone delimiting the central Atlas (sensu lato) and the Eastern Atlas. It corresponds to a zone of major heterogeneity giving rise to N-S trending faults (Burollet, 1956; Turki, 1984, 1985, Gourmelen, 1984; Abbes, 2004). 4. The Eastern platform is characterized by a weakly folded thick Neogene succession that extends eastward to the Malta scarp. 5. The Saharan platform is characterized by folded Paleozoic rocks of the African craton, and makes up the foreland of the Atlasic chains (Fig. 1). The present architecture of the Saharan Atlas in Tunisia is defined by two principal models: The first one (Fig. 1) emphasizes a general SW-NE geological structure in successive and parallel bands represented by the tellian zone and the diapirs zone in the North, the central Atlas then the southernmost Atlas with oblique orientation and installed within a NW-SE corridor. These fields are bordered in the East by the “North-South Axis” (Castany, 1951; Burollet, 1956, 1991; Rouvier, 1977; Zargouni, 1984, 1985).