Salt-influenced upper-crustal segmentation of the Tellian–Dorsal transition in the El Kef region (northwestern Tunisia) revealed by gravity derived structural analysis

The El Kef region of northwestern Tunisia is located within the transition between the Tellian domain and the Tunisian Dorsal, an area influenced by Mesozoic rifting, Triassic evaporites, and later Alpine compression. This study investigates the shallow structural segmentation of this salt-influenced transition zone using an integrated gravity-based approach that combines Bouguer and residual anomaly mapping, gravity profiles, structural filtering, three-dimensional Euler deconvolution, and 2.5D forward modelling. The Bouguer anomaly field is dominated by a first-order north–south gravity gradient, interpreted as the expression of a broad and laterally segmented transition rather than a sharp tectonic boundary. Superimposed residual anomalies with wavelengths of about 5–12 km reveal marked lateral density contrasts associated with fault-bounded domains, Cenozoic basins, and Triassic evaporitic bodies Structural lineaments extracted from total horizontal gradient and tilt-angle maps define a dense fault network mainly oriented NE–SW and NW–SE, with subordinate N S trends. Euler deconvolution indicates that the main gravity sources are concentrated at shallow depths, approximately 0.5–3 km, consistent with upper-crustal fault zones and evaporite-related discontinuities. The 2.5D gravity modelling further supports a segmented shallow subsurface architecture characterized by fault-bounded geometries and pronounced lateral variations in density and thickness between Triassic evaporites, Cretaceous syn -rift units, and Neogene–Quaternary basin fills. The models indicate that salt structures may extend beyond their surface expression in some areas or remain entirely buried, suggesting the presence of in-depth salt bodies whose later collapse could have controlled the development of Neogene–Quaternary grabens. Overall, the results indicate that the El Kef transition zone is controlled by the multiphase deformation affecting the area from Mesozoic extensional stages. This study shows that gravity-derived structural attributes provide reliable constraints on shallow segmentation in salt-influenced orogenic transition zones and contribute to a better understanding of the Tellian–Dorsal boundary in northwestern Tunisia.