26/10/2023

Dr. Mabrouk Bachari

4:00 pm

Late Cretaceous lateral facies and thicknesses changes are common in the southern Tethyan margin, especially during the final rifting stages of the Tethys and its early onset of closure. Particularly, northern Tunisia, being located closure to a plate boundary, represents an important area to investigate the tectono-eustatic controls on sedimentation. The study of the Cenomanian-Turonian transition in the Mellegue basin (north-central Tunisa) shows, in the uppermost part of the Cenomanian Fahdene Formation, a Pre-Bahloul unit overlain by the Cenomanian-Turonian Bahloul black shale. This unit is correlatable with the transgressive fine-grained limestone bed underlying the CTB black shale in Algeria, as well as the fine-grained limestone bed overlying upper Cenomanian shallow-water deposits of southern Tunisia. This interpretation leads to the conclusion that the CTBE coincides with a major transgressive trend over most the North African stable craton. Investigation of field data, high-resolution biostratigraphy, gravity data analysis and lithostratigraphic correlations of strata deposited during the Late Cretaceous allowed us to precisely determine three major unconformities in the Mellegue basin and span the period from Coniacian to Maastrichtian. These unconformities indicating an early tectonic compressional event in the Late Cretaceous, that probably started in Turonian. This inversion could be explained by a Santonian compressional event, that might have started earlier, in the context of the convergence between African and European plates. The study of Turonian-Coniacian carbonate reservoir well outcropping in the Jebel Serj-Bargou area (northern-central Tunisia), using a multidisciplinary approach, has led to establish a detailed layering within these heterogeneous multi-layers reservoir rocks. Some of the selected layers show a relatively high reservoir potential.