The J. Boudinar is located at the junction between several of the main structural trends of Tunisia : the atlasic lineament (NE-SH), the N-S axis and the NW-SE Kasserine and Mezzouna faults . A stratigraphical and structural study of this area has been performed with detailed mapping (1 : 20 000). STRATIGRAPHY - SEDIMENTOLOGY the detailed stratigraphic analysis of several sections results in the characterisation of the thickness variation in aIl the Formations since Jurassic. Aleg Formation is dated of uppermost Turonian age and Abiod Formation of Campanian to early Maastrichtian age. 7 regressives megasequences are defined by means of boundary discontinuities. The 3 main discontinuities are of early to middle Albian age, uppermost Turonian age and Maastrichtian to middle Eocene age. They result of different processes as : emersions, submersions of exonded shelves and erosion under shallow marine conditions. They are accompanied by an induration under aerial or shallow water environment. STRUCTURAL HISTORY : It results of the application of different successive stresses fields on a previously structured basement. A succession of alternate extensions and compressions is characterised, always accompanied by halokinesis. 5 tectonic regimes have been recognized : 1 - A N-S extension during early Cretaceous. 4 strikes of fractures of different scales are mobilised (N 65-85; N 100-110; N 130-140; N 165-170). Particularly, the atlasic lineament results in a N 65-85 oriented kilometric graben. 2 - A NE-SN extension characterizes the late Albian to Turonian period and results in N 120-140;N 45-50 and N-S oriented subsident areas and tilted blocks. 3 - Since Senonian to late Eocene times, halokinesis becomes a predominant phenomenon . NE-SW and N-S salt anticlines and salt diapirs represent the consequence of the atlasic compression. 4 - A multidirectional extension regime characterizes the middle mIocene. N 60 and N 140 faults are mobilised . 5 - Since late Miocene to present day, the area is submitted to the NW-SE oriented atlasic compression. It results in a compressive anticline with an evaporitic core and a syncline overprinted to the previously collapsed area. The left lateral strike-slip motion along the N-S lineament results in the bending of the J. Boudinar fold. Finally, a right lateral motion is suggested in order to explain the clock-wise rotation of the median segment of the fold. In summary, the J. Boudinar results of a positive structural inversion in correspondence with the atlasic lineament. SUBSIDENCE: Curves of cumulative thiekness allow us to charaeterize several crisis in the evolution of subsidence. They are in good agreement with general evolution of Tunisia, which is itself related to the African, Thetyan-Atlantic and Mediterranean paleogeographie evolutions.
