Strike-slip-Salt tectonic interactions in the Central Tunisian Atlas: Inversion of a transtensional horsetail splay into a transpressional zone in the Mezzouna–Maknassy area

The Mezzouna–Maknassy salt structures are located along the southern part of the North–South Axis in the Central Tunisian Atlas and form part of a segmented strike-slip deformation zone influenced by Triassic evaporites. Integrated field structural observations, 2D seismic reflection data, gravity anomaly analysis, and paleostress inversion reveal a NW-trending fault system characterized by en echelon fault arrays, horsetail splays, salt-cored folds, and fault fan geometries. Field data document dominant strike-slip kinematics associated with salt-related structures, while seismic profiles show a steep, fault-bounded Triassic diapir extending from depth to surface and associated with thickness variations in Jurassic and Cretaceous units. Gravity-derived structural trends delineate N-S and NW–SE discontinuities coincident with mapped faults and salt-related uplifts, indicating basement control on the deformation corridor. Paleostress results document a polyphase evolution involving an Early Cretaceous transtensional regime, marked by strike-slip deformation and local extension within the horsetail splay, followed by a Cenozoic transpressional regime associated with structural reactivation. Within this evolution, the Mezzouna–Maknassy salt structures initially developed during the Early Cretaceous as a transtensional horsetail splay, that mechanically links to the southern part of the sinistral North–South Axis. Fault segmentation and localized dilation promoted reactive mobilization of Triassic evaporites, leading to the development of salt walls, salt-cored folds, and localized depocenters. During subsequent Cenozoic compression, this inherited framework was reactivated and reorganized into a dextral NW-trending strike-slip corridor, where pre-existing left-stepping fault geometries controlled restraining structures and salt extrusion. The Mezzouna–Maknassy structures therefore provide a relatively rare example of salt-influenced deformation developed within a transtensional horsetail splay in an intraplate strike-slip setting.