New insights on Middle and Upper Eocene paleogeography in central and southeastern Tunisia (Gulf of Gabes)

The present work is a contribution to the study of the Middle and Upper Eocene series in the Gulf of Gabes. It aims to study the spatio-temporal variation of the lithofacies in 26 wells. This work is based on the review of the logging data of these wells. A lithostratigraphic correlation and a structural one are established in order to control the relationship between spatio-temporal variations of thickness and lithofacies and early NW-SE faults activities and the resulting structural framework. The present work confirms the spatial lithofacies distribution according NW-SE belts as already mentioned in previous works. In addition, this work shows the basic role of the contemporaneous structural framework as testified by the abrupt spatial variation of both thickness and lithofacies. The sedimentary substratum was cut into piano-key like structure with open marine shallow-water lithofacies on the uplift structures and deep-water low energy restricted lithofacies within the depression structures. Locally some particular lithofacies occur in relation with the hydrodynamic context of the study area with patch-reef windward position and glauconite and organic matter-rich deposits in leeward position. The vertical variation of lithofacies confirms the role of the early tectonic activities, such as during the deposit of Cherahil A and Cherahil B units, the NW-SE oriented faults were rather active, whereas, during the deposit of the median Siouf/Reineche unit the faults were in quiescence testified by the uniformization of shallow carbonate sedimentation. The Middle and Upper Eocene plat-form consists of an irregular cut plat-form.