Jeffara Fault System: Multi‐Geophysical Characterisation and Petroleum System Impact in Southern Tunisia

Abstract

ABSTRACT The passive margin in South‐East Tunisia has preserved key tectonic events related to the opening and closing of the Neotethys oceans, as well as its position south of the Africa–Eurasia collision zone during the Alpine Orogeny. This region provides valuable insights into the evolution of the central Mediterranean basin and the passive margins of Tethys. The configuration of numerous Mesozoic–Cenozoic basins was influenced by the collision between Western Gondwana and Laurasia, characterised by a major right‐lateral shear zone with significant strike‐slip movement. By the end of the Triassic, rifting had spread across Gondwana, affecting both the eastern margin of Africa and the southern Arabian Plate. Although previously considered a basement fault, detailed structural and geophysical analysis reveals that the Jeffara Fault exhibits a complex geometry and kinematic evolution. The fault plane, oriented NW‐SE, displays a listric arc geometry with dip angles decreasing from about 75° in the north to less than 40° in the south, accompanied by three major synthetic faults that facilitated an eastward basin collapse of more than 10–15 km. Field and subsurface data show that the spacing of ridge alignments relative to the main fault trace increases progressively southward from 20 km to more than 140 km, forming a diverging arc that marks successive erosion surfaces. The Jeffara fault system was initiated during the Early to Middle Triassic, when initial rifting triggered the collapse of Triassic and older sequences. Jurassic extension further reduced the fault surface dip, producing rollover geometries and a first network of synthetic and antithetic faults. During the Early Cretaceous, a second generation of synthetic faults intensified subsidence and controlled the development of localised sedimentary gaps, particularly in the eastern compartment. In contrast, the Miocene is marked by thermal subsidence of approximately 150–200 m, with no evidence of syn‐sedimentary tectonic activity, consistent with models of lithospheric cooling. By the Plio–Quaternary, the Jeffara Fault was sealed, marking the cessation of detachment activity. This long‐term tectonic evolution exerted a first‐order control on petroleum system distribution. In the western Ghadames Basin, a pre‐Triassic petroleum system dominates, whereas in the eastern Jeffara Basin, post‐Triassic systems prevail, with Mesozoic and Cenozoic reservoirs structurally compartmentalised by fault‐controlled traps. The integration of structural geometry, kinematic evolution and quantitative estimates of fault displacement, erosion and subsidence provides new insights into hydrocarbon migration pathways and trapping mechanisms. This refined structural interpretation provides better insights into the petroleum system distribution and the mechanisms of hydrocarbon migration and trapping, offering a novel understanding of exploration potentials in this strategic region of southeastern Tunisia.