MESOZOIC PALEOSTRESS EVOLUTION IN THE SAHARAN PLATFORM (SOUTHERN TUNISIA)

A detailed analysis of brittle deformations in the Saharian platform o f southern Tunisia is based on studies of fault-slip data sets and joi nt sets. It allows reconstruction of the Mesozoic paleostress evolutio n. During the Permo-Triassic, N-S extensions occurred with high late P ermian subsidence rates. During the Norian, strike-slip movements reac tivated former normal faults. During the Jurassic and the Cretaceous a succession of extensional events was characterized by : (1) a N-S ext ension which dominated from late Triassic to early Aptian. We relate t his extension to the Africa-Eurasia divergence; (2) a ENE-WSW extensio n during the Cenomanian. We relate this extension to the opening of th e African basins ; (3) a NE-SW Senonian extension that continued durin g the Cenozoic in the Jeffara and in the Gabes Gulf, during the furthe r evolution of the northern African margin. The various compressional trends recorded in the platform are attributed to Cenozoic events.