The Hammamet, Gabes and Chotts basins (Tunisia): a review of the subsidence history

We modeled the subsidence of three Mesozoic basins in Tunisia by using well data, seismic lines and field data. The results are presented here with an attempt to relate the succession of events deduced from the subsidence evolution analysis to the geodynamic evolution of the northern African margin. The Mesozoic and Cenozoic geological history of Tunisia has been broken down into two major periods separated by a transition period. The first period from Trias to Aptian was characterized by a constant subsidence of variable intensity spread over most of Tunisia, and over all the studied basins. This period was dominated by extension accompanying the Tethyan rifting during Trias-Lias. The transition period during the upper Cretaceous was characterized by extension and by the weak effects of far-seated compressional events. It is coeval with the first appearance of salt mobilization. The last period, in Tertiary, marked the appearance of the major collisional events, mostly during Neogene. During this last period, basins were characterized by very different behaviour, depending on their location: East or West of the North-South axis and close or not to the Tellian nappes. Among the three basins we studied, we paid special attention to the southernmost Gabes basin located south of the present eastern margin of Tunisia. The first-order evolution of its subsidence is similar to that we infer for most of the Tunisian basins. We emphasize the role of the structuration of the Gabes basin in the partition of the subsidence through time. (C) 2002 Elsevier Science B.V. All rights reserved.