The Jurassic events and their sedimentary and stratigraphic records on the Southern Tethyan margin in Central Tunisia

The Jurassic sedimentary record of Central Tunisia comprises shallow marine peritidal carbonates, black shales, outer shelf marls and limestones, ironstone, deep marine condensed sections and hard-grounds. The faunas, especially ammonites, allow increasingly precise age estimations and correlations referred to the biochronological standard for Submediterranean Europe. The faunas show a submediterranean character in open marine environments and the South Tethyan situation is attested by abundant Emileia and Oraniceras in lower Dogger as well as the lack of boreal and sub-boreal families all along Jurassic. In fact, the Jurassic of Central Tunisia corresponds to five major transgressive-regressive tectono-eustatic second order cycles, four of which are separated by three sub-marine unconformities associated with important hiatuses. The abrupt facies changes and the frequency of condensed sections and/or hiatuses resulted from the interaction between global sea level fluctuations and local to regional tectonic activities associated with Early Mesozoic Tethyan rifting. Central Tunisia (North-South Axis) corresponded during the Jurassic to an uplifted mega-block acting as a carbonate outer shelf relayed to the north and to the south by subsident basins. Due to the intense activities of deep marine currents, occurring especially during the major rises or falls of sea level, this carbonate outer shelf has acted as a sediment-starved high. This latter has been maintained far from coarse or abundant elastic influences. Sedimentation has been recorded only during aggradational-retrogradational highstand phases.