ABSTRACT: Evolution of Atlasic Basins in Tunisia

Pierre F. Burollet

Below the Atlasic Tunisia and the Pelagian Sea, there is no information about the nature, the age, and the depth of the basement. The Triassic series includes large thicknesses of evaporites. Therefore, the Atlasic Tunisia, including its offshore, is disconnected from the basement and is folded as plis de couverture.

The main structural and tectonic features are north-south discontinuities in the basement, as the north-south axis, from Tunis to Gabes; east-west distension features, corresponding to large steps of the southern margin of the Tethys, underlined by thick Jurassic and Cretaceous deposits; extreme youth of tectonics, sketched during preliminary phases: Late Cretaceous, middle Eocene, Oligocene, and early Miocene (folding actually began with the middle Miocene during the first arrival of the Tellian nappes in the north; however, the most active tectonics occurred at the end of the Miocene and after the Pliocene. New tectonic motions are known during the Pleistocene and even during historic times.); many extrusions of Triassic mixed shale, evaporite, and dolomite; outcrops of mainly insol ble caprocks; and the rare wells, drilled through diapirs, that encountered massive salt below 200-300 m of gypsum.

Recent discoveries and important oil shows have proven the existence of oil and gas in newly identified depocenters and reservoirs. In general, except for some areas around producing fields, Atlasic Tunisia is largely underdrilled.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990