Based on new structural, sedimentary, stratigraphic and seismic reflection data from Cretaceous sequences of the Zemlet el Beidha anticline of the northern Chotts range (South Tunisia), this study yields fresh insights into the geodynamic evolution of the South Tethyan margin. The rifting of the margin started in the Triassic-Jurassic and continued during the Aptian-Albian. In this last period N to NE trending extension was associated with WNW and NW trending normal faults, bounding the developing horsts and grabens structures. This tectonic framework is highlighted by strong thickness and facies changes in the Aptian-Albian series associated with slumps and syntectonic conglomerates. During the Coniacian to Santonian times, the study area was characterized by continued subsidence. Consequently, the Coniacian-Santonian series are represented by sedimentary infilling consisting of post-rift marl-rich sequences followed by limestone and marl sequences. 2 Folds geometry and associated faults system and tectonics analysis, confirm the role of the Aptian-Albian rifting inheritance faulting in the structuring and the development of the folds and thrusts belts of the southern Tunisian Atlas during the Cenozoic inversion, in particular in the development of the ENE striking structures such as the Zemlet el Beidha anticline.

Tectonic deformations in the Southern Atlassic Front of Tunisia (SAFT) and the Gulf of Gabes result from the Nubia-Eurasia convergence. This study, based on the inversion of geologically determined fault slip vectors, presents evidences for spatial and temporal changes in the stress state. Fault kinematics analyses reveal a temporal change in states of stress during the late Cenozoic. A paleostress (Miocene-Pliocene) state is characterized by a regional compressional tectonic regime with a mean N134±09°E trending horizontal maximum stress axis (σ 1 ). A modern (Quaternary to present-day) state of stress also corresponds to compressional tectonic regime with a regionally mean N05±10°E trending horizontal σ 1 . The SAFT corresponds to two distinct domains: a far-foreland Atlassic front related to contractional deformation associated with southward propagate thrusting, and eastward, the Gulf of Gabes characterized by normal component NW to WNW trending faults at the crustal margin scale probably related with a transtensional tectonic regime. We propose that the spatial and temporal changes in the stress during the Miocene-Pliocene and Quaternary may result from the geodynamic evolution of the Tunisian Atlas in relation to the rotation of Corsica-Sardinia blocks and the separation of the Sicilian continental lithosphere from the Ionian oceanic lithosphere.These temporal and spatial stress changes along the SAFT and the Gulf of Gabes are probably the engine behind the moderate seismicity, leading at the same time to a reactivation of the inherited major structures created during the evolution of the Southern Tethyan margin.

The Medjez-el-Bab (MEB) box anticline, northern Tunisia, gives new evidence allowing us to precise the tectonic agenda of the North African paleo-margin inversion. On the one hand, the examination of this structure permits us to show that the inversion began approximately by the transition between the Lower and Upper Senonian. On the other hand, it highlights the occurrence of a Middle-to-Late Eocene compressive tectonic phase (the so-called Atlas or Atlasic phase), which is well recorded by reworking material within the Middle Eocene deposits as well as by the angular unconformity of the Late Eocene beds, supporting the hypothesis of compressive Eocene phase (Atlasic phase) generalized all over the Maghreb.

Detailed geological mapping, dating, and gravimetric and seismic data are used to interpret the Lansarine-Baouala salt structure (North Tunisia) as a salt canopy emplaced during the Cretaceous Period. The extensional tectonic regime related to the Cretaceous continental margin offered at least two factors that encouraged buried Triassic salt to extrude onto the sea floor and flow downslope: (i) extension induced normal faults that provided routes to the surface, and led to the formation of submarine slopes along which salt could flow; (ii) this structural setting led to differential sedimentation and consequently differential loading as a mechanism for salt movement. The present 40-km-long Lansarine-Baouala salt structure with its unique mass of allochthonous Triassic salt at surface was fed from at least four stems. The salt structure is recognized as one of the few examples worldwide of a subaerial salt canopy due to the coalescence of submarine sheets of Triassic salt extruded in Cretaceous times.

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Stratigraphical, sedimentological and structural data and a Bouguer gravity map of Medjez-El-Bab (MEB) in Northern Tunisia are used to illustrate a Cretaceous example of salt extrusion on a passive continental margin. Located just south of the Teboursouk thrust front (a preferential décollement surface used by the continuous Tertiary shortening in this area), the MEB structure is a simple N40°E box anticline. Removing the two Tertiary foldings (Eocene and Miocene) leads to the exposure of the original feature of a simple submarine ‘salt glacier’. The Triassic salt rocks appear as an Albian interstratified body between two Cretaceous series with stratigraphic normal polarity, suggesting a bedding parallel extrusion (at the sediment–water interface) of the Triassic salt in Cretaceous times. The formation of such salt extrusions are associated with extensional faulting (probably both in the cover and basement), the presence of a slope and basinwards salt flow. This scenario is similar to the allochthonous salt described in other salt provinces, characterizing passive margins.

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