Discovery of Jurassic ammonite-bearing series in Jebel Bou Hedma (South-Central Tunisian Atlas): Implications for stratigraphic correlations and paleogeographic reconstruction

• This study demonstrated the existence of outcropping Jurassic sequence Southward Jebel Rheouis of Central Tunisia.
• Condensed facies and discontinuities attest that Jebel Bou Hedma area acted during Jurassic-Early Cretaceous, and probably even though later on, as a resistant paleo-high that should extend E–W along Bou Hedma-Ben Kreir area.
• The Toarcian organic-rich facies, considered as a source-rock for the Jurassic petroleum play are absent in the study area.
• The identification of a stratigraphic bed marker made of conglomeratic facies with mixed Kimmeridgian and Tithonian ammonite faunas attests of an important tectonically active setting with subsequent erosion and reworking during Late Jurassic-Earliest Cretaceous times.
• The comparison of these newly discovered Jurassic series to lateral equivalents from the South-Tethyan Margin of the Maghreb, updated North–South and East-West transects through the Jurassic successions of the Central Tunisia and led to place them in their broader geodynamic context.

Recent geological mapping undertaken in the Southern-Central Atlas of Tunisia led to the discovery of Jurassic ammonite-bearing series in the Jebel Bou Hedma E–W anticline structure. These series represent the Southernmost Jurassic rocks ever documented in the outcrops of the Tunisian Atlas. These series which outcrop in a transitional zone between the Southern Tunisian Atlas and the Chott basin offer a valuable benchmark for new stratigraphic correlation with the well-known Jurassic series of the North–South Axis of Central Tunisia and also with the Jurassic subsurface successions transected by petroleum wells in the study area. The preliminary investigations allowed the identification, within the most complete section outcropping in the center of the structure, of numerous useful biochronological and sedimentological markers helping in the establishment of an updated Jurassic stratigraphic framework chart of South-Western Tunisia. Additionally, the Late Jurassic succession documents syn-sedimentary features such as slumping, erosion and reworking of sediments and ammonite faunas that can be considered as strong witnesses of an important geodynamic event around the Jurassic-Cretaceous boundary. These stratigraphic and geodynamic new data make of the Jurassic of Jebel Bou Hedma a key succession for stratigraphic correlation attempt between Atlas Tunisian series and those currently buried in the Chott basin or outcropping in the Saharan platform. Furthermore, the several rich-ammonite identified horizons within the Middle and Upper Jurassic series constitute reliable time lines that can be useful for both paleogeographic and geodynamic reconstructions of this part of the North African Tethyan margin but also in the refinement of the potential migration routes for ammonite populations from the Maghrebian Southern Tethys to Arabia.