Aptian-Albian Transition in Central Tunisia： Tectonosedimentary and Paleogeographic Records

The Aptian-Albian series are characterized, in Tunisia, by several variations in subsidence rates and records discrete unconformity between Albian and Aptian in central and southern Tunisia. In central Tunisia Upper Aptian regressions were sustained until the beginning of Albian with a low sea level stand. In this paper, wells data gathered from central Tunisia exposes well expressed Aptian-Albian hiatus associated to several partial sedimentary gaps, erosion surface and unconformities and correlated with the ＂Aptian Crisis＂ highlighted at the Tethyan scale. This latter is coeval with an extensional regime in concurrence with the African rifting responsible for halokinesis movements and magmatism and leaded to the establishment of paleoreliefs as much as tilted blocks and half grabens in central Tunisia. Deposition shows regional hiatus and lateral transition from platform facies to south to, open marine facies to the north. The structural configuration of this domain within normal faulting, horsts and grabens leaded to the establishment of several distinct basins with different subsidence rates. Discordances occur specially around and upward uplifted blocks and emerged land and are especially associated with Aptian reef, karsts and shallow marine facies. They are unconformably overlaid by the transgressive open marine facies of Albian-Cenomanian series acknowledged as source rock in Central Tunisia. In addition, the reefal Aptian facies is considered a potential reservoir rocks in central Tunisia and it is frequently associated to mineralization and Hydrocarbure reservoirs.