Sedimentology and Petrographic Analyses of the Upper Cretaceous and Lower Eocene Carbonate Deposits in the Mateur-Beja Area (NW of Tunisia): The Repercussions of Tectonic Style on Sedimentation

Abstract

The northwestern Tunisian Mateur-Beja area comprises a thick succession of carbonate rocks belonging to the Late Cretaceous (Abiod Formation) and Early Eocene (BouDabbous Formation and its lateral equivalent) times. Sedimentological and petrographic analyses carried out on these Formations with regard to their palaeogeographic reconstructions. Three sections from the upper Cretaceous deposits and twenty sections from the lower Eocene successions were selected and correlated for this study. The upper Cretaceous Abiod Formation is dominated by foraminiferal biomicrite deposited in upper slope to basin environments, usually influenced by gravity-driven currents. The lower Eocene carbonate successions are characterized by various and diverse facies associations deposited in inner platform to basinal environments. Both carbonate Formations are characterized by lateral variations in thickness and facies, although they were deposited under varying environmental circumstances. Close inspections show that changes in thickness and facies were mainly controlled by sea-floor topography and deposition rates. The conspicuous change in sea-floor topography is well expressed during drastic changes in tectonic style associated with active subsidence, while deposition rates significantly decrease in areas marked by active marine erosional currents. The upper Cretaceous and the lower Eocene carbonate deposits provide useful data about the relationships between tectonic and sedimentation.