Cretaceous-Palaeogene sedimentation patterns and structural evolution of the Tunisian shelf, offshore the Pelagian Islands (Central Mediterranean)

The Late Jurassic-Palaeogene structural evolution of the eastern Tunisian p latform exerted a significant control on the depositional architecture of t he 4.5-km-thick carbonate-mart succession, that was deposited on this Afric an plate margin, throughout this period. Widespread Jurassic platform carbonates (Nara Fm.) underwent extension and subsidence throughout the Early Cretaceous. This extension resulted in the formation of a system of NW-SE-trending normal faults, coupled with minor a ntithetic structures, flanking half grabens up to 20 km wide. These subsidi ng basins hosted the deposition of shallow-water carbonates interfingered w ith marls and fine-grained siliciclastics. This succession, which is up to 2.5 km thick, is interpreted to have been deposited during a syn-rift episo de which continued until the mid-Aptian. Overlying basinal marls and carbonates seal the NW-SE syn-rift extensional faults, thus marking a post-rift stage that extends up to the Eocene, Post- rift sedimentation ends in the Middle-Upper Eocene with the deposition of p latform carbonates relating to the Halk el Menzel Formation, which lies unc onformably above different stratigraphic levels of the underlying basinal c arbonates. This is capped by an erosional surface of regional extent. From the latest Cretaceous onwards, compressional activity occurred on this part of the Pelagian Block partially reactivating Lower Cretaceous extensi onal structures. Thrusting and folding generated uplift and associated eros ion, leading to the development of local unconformities and hiatuses at dif ferent levels in the stratigraphic column. This compressional event marks t he onset of convergence between the African and European plates and thus th e transition from a passive margin to a foreland in this area. The structural history of this part of the African plate margin displays si milar evolutionary trends to other Tethyan passive margins which were estab lished during the Jurassic and Early Cretaceous times when extensional even ts split pre-existing carbonate platforms. (C) 1999 Elsevier Science B.V. A ll rights reserved.