Basin evolution and deposition during the Early Paleogene in Tunisia

Abstract: The marine Paleocene and Ypresian deposits of Tunisia, within the E1 Haria For-mation and the Metlaoui Group, have been intensively studied because of the commercial interest in phosphates and hydrocarbons. This paper presents the latest updates of isochron, lithofacies and palaeogeographical m ps, and interprets he patterns identified in light of syn-sedimentary structure. This reveals a close association between structure, basin geometry and subsidence. Facies di tribution during the Early Paleogene is thought to be structurally con-trolled along basement lineaments. These major fault systems were reactivated several times during the Mesozoic and Tertiary, with t e last movements occurring as Neogene and post-Villafranchian events. The structural control of facies is most evident during the Ypresian, particularly along the 'North-South Axis ' (Nosa) a sub-meridian orogenic segment of Cen-tral Tunisia. In this area the Ypresian deposits exhibit a preferred alignment with the Nosa exerting a notable influence on basin geometries and rates of local subsidence. In addition to two large islands indicated in the onshore area of Tunisia, a number of 'bald ' highs are iden-tified in the offshore, representing original submarine highs. The general pattern across Tuni-sia throughout the period is of a number of small tectonically controlled basins. The distribution of phosphorites, organic-rich shales and evaporites can be particularly linked to the development of restricted basins during the period. Previous studies on the Early Paleogene of Tuni