The present paper deals with a geochemical investigation (TOC, Rock–Eval pyrolysis, and GC–MS) carried out on two potential mid-Cretaceous (Albian lower Fahdene and Cenomanian–Turonian Bahloul) source rocks and natural oil seeps collected from outcrops and mine boreholes located around the three extrusive salt structures of Ech-Cheid, Fej Lahdoum, and Boukhil, belonging to the Triassic domes zone of northern Tunisia. Rock–Eval pyrolysis results indicate the presence of moderate to good and moderate to excellent quantities of organic matter (OM) of oil–gas type II/III (means TOC: 0.90 wt.%, HI: 180 mg HC/g TOC, and PP: 2.00 mg HC/g rock) and oil-prone type II (means TOC: 3.5 wt.%, HI: 458 mg HC/g TOC, and PP: 20 mg HC/g rock) kerogens for the Fahdene and the Bahloul Formations (Fms), respectively. The thermal maturity of the OM preserved in these source rocks varies between late diagenesis and the late oil window depending mainly on the basin architecture marked by the presence of paleohighs (Triassic salt domes and horsts), grabens, half-grabens, and tilted blocks that controlled the varying degrees of subsidence. Gas chromatography-mass spectrometry (GC–MS) analysis of source rock extracts (Bitumen) and oil seeps and correlations with hierarchical cluster analysis (HCA) using biomarkers parameters (Diasteranes C27βαS/C27ααS and Hopanes C29H/C30H ratios) suggest that the collected oil seep samples were sourced by the Fahdene and the Bahloul Fms. The spatio-temporal oil seeps distribution and associated tectonics indicate that several faults of NW–SE, N-S, E-W, and NE-SW trendings have facilitated oil migration from these source rocks to favorable reservoirs of middle-Turonian Bireno, Coniacian Douleb, and Campanian–Maastrichtian Abiod carbonates as well as a Miocene Oum Dhouil sandstone. These mid-Cretaceous source rocks and associated reservoirs, as well as overlaying argillaceous seals and traps (Flanks of diapirs, uplifted paleohighs, and anticlines), as essential elements, in addition to oil migration pathways and accumulation processes attest to the presence of active conventional petroleum systems in northern Tunisia. This could help guide petroleum exploration activities around subsurface diapir structures analogous.
