Tunisia's position at the extreme northeast of the African continent, between the Western Mediterranean and Eastern Mediterranean basins, gives it particular interest regarding the geological history of the Earth. From North to South, passing through the folds of the Tunisian Atlas, one notes the transition from the folded and strongly tectonized Alpine morphostructures of the Maghrebides to the simple and slightly deformed morphostructures of the Saharan platform. This structure owes its organization to the tectonic constraints resulting from the continental collision between the European plate and the African plate since the end of the Tertiary era (Fig. 1).
In the Land of Ksours, in Southeast Tunisia, the geological series covering the Tataouine Basin tells another story: that of the opening of the Tethys during the Secondary era (Fig. 2B).
A series of escarpments formed by cliffs separated by wide plains (Fig. 2C) runs along the Jeffara plain in a sub-meridian direction. These escarpments allow one to rise in altitude from the low coastal plains of the Gulf of Gabes to the high plateaus of the Dahar, which dip progressively westward before disappearing under the sand dunes of the Grand Erg Oriental. They also allow one to travel back through the geological time scale through the terrains that form them.
Indeed, the outcrops of the Jeffara and Dahar in Southeast Tunisia constitute a unique window into the geological history of the Saharan platform. The oldest sedimentary records appear on the surface north of the Jeffara plain, at Jebel Tebaga in Medenine. This is the only outcrop of marine Upper Permian in Africa, whose sediments and fossils tell the story of the separation of Pangea (Fig. 2A) into two supercontinents: Gondwana to the South and Eurasia to the North. From the end of the Primary era, the configuration of the Earth underwent a major change with the appearance of a great rift that split Pangea in two, allowing the development of an E-W seaway that would widen during the Secondary era to give rise to a new ocean: the Tethys.
During these oceanic extension movements, Southern Tunisia always occupied a passive margin position on the southern Tethys shore. Formed by a vast plate whose extension and extreme flatness made it an epicontinental domain, the southern shore of the Tethys was under the permanent influence of sea-level fluctuations and climate changes. The spectacular variations in sedimentary facies and the large number of fossil sites bear witness to the richness and diversity of the natural environments and living organisms that occupied the edge of the Saharan platform and their evolution over geological time.
