Early Cretaceous Tectonostratigraphic Evolution of the Southern Tunisian Margin Based on Gravity, Seismic and Potential Field Data: New Insights into a Geodynamic Evolution in a Tethyan and Mesogean Rifting Context

Many geophysical and geological data have been used to interpret the tectonic evolution of the south-eastern part of the Tunisian margin and to analyze the dominant structures in the area. The Menzel Habib Plain (MHP) and surroundings, targeted by this study, exhibits thick siliciclastic and carbonate formations attributed to the Early Cretaceous period. Integration of seismic and gravimetric data coupled with analysis of the syndepositional faults affecting these formations prove that the Tunisian margin is dominated, during this period, by N-S to NE-SW extensional directions. The geodynamic evolution of the MHP is mainly due to the irregular normal movement of the N-S faults, which represents the southernmost branch of the N-S Axis (NSA) and of the NW-SE faults, which constitutes the SE segment of the South Atlasic fault corridor (SAFC). In addition, the NE-SW and E-W oriented faults contributed to this evolution. Over extensive periods, this network of faults determines horst and grabens basin geometry or tilted blocks inducing formation of several distinct areas with different subsidence rates. Simultaneously, the normal activity of the major faults promotes the vertical mobilization of the Triassic salt resulting in the individualization of several diapiric bodies, some of which pierced their sedimentary cover. These dynamics reflect echoes of the sinistral drifting of Africa with respect to Europe, integrated in a long Tethyan rifting cycle, and the beginning of opening of the Mesogean Sea, respectively.