Integrated geophysical and geological analysis of the salt-related structures within the Jeffara basin, Southeastern Tunisia

As part of the North African passive margin, the southern offshore Tunisia represents one of the main salt provinces in the area encompassing a variety of Triassic salt structures, e.g., salt ridges and diapirs. In this study, calibrated 2D seismic sections and gravity data have been used together to better understand the structural framework of this relatively undocumented area. Differential structuring of blocks delimited by deep-seated NW-SE-trending salt-intruded faults have been revealed. These Tethyan normal and strike-slip faults, resulting from the various Mesozoic rifting stages between the European and African plates, have controlled the distribution and depositional environment of the sedimentary sediments from Mesozoic to Cenozoic. With the aim to better characterize and understand the structural framework of the study area, different gravity maps and filtering have been used including (1) complete Bouguer anomaly map, (2) its corresponding residual anomaly map, (3) multiscale decomposition of the Bouguer anomaly using upward continuation technique, (4) horizontal gravity gradient (HGG) map, and (5) theta angle (TA) map. The complete Bouguer gravity anomaly map reveals the presence of high amplitudes located in the eastern part of the basin. The gravity gradient decreases gradually, towards the NW, marking an important gravity low suggesting a significant subsidence. The HGG and TA maps display NW-SE-trending gravimetric trends, caused by the density contrast outlining generally the salt ridges. The lateral and vertical distribution of these salt bodies with depth has been further assessed using multiple pseudo-depth anomaly maps based on the decomposition of the Bouguer gravity. The obtained results exhibit Jeffara fault system trends and successive evolutionary stages of Triassic salt rising such as salt pillow, rollers, diaper, and salt walls that could represent important structures for hydrocarbon exploration in the area.