Étude des Processus sédimentologiques liés au dépôt des phosphates du gisement de Kef Essennoun, Bassin de Djebel Onk

Abstract

The Kef Essennoun phosphatic deposit, part of the Djebel Onk Basin, is located 100 km south of the Tebessa city and 20 km from the Algerian-Tunisian border. It shows a tabular structure that dipped to the south. Field observations howed the existence of a cross stratification that plunges towards the northeast. This work aims to investigate the hydrodynamic processes that was controlled the deposition of these phosphates. In this object, grain size analysis was used to study 31 samples taken from the phosphatic layers. The obtained results permitted to classify these phosphates as slightly gravelly sand, while the cumulative curves analysis of grain size showed that the saltation is the ominant mode of transport followed by rolling. These results indicated that these phosphates are reworked phosphates which was formed elsewhere and then transported and deposited in this part of the basin at a shallow depth of water where currents were occurred. The dipping direction of the cross-stratification indicated that the current direction was from the southwest to the ii northeast, which was related to the relative paleoposition of the deposit to the Ain Fouris.shoal.