Sedimentological study of the Messinian series of Jebel Aoud Sma

Two geological sections were surveyed at Djebel Aoud Sma which occupies the north-eastern termination of the Ouled Ali Mountains in the southern edge of the Bas Cheif basin.Three formations were identified. The Grey Marls Formation attributed to the Messinian constitutes the base of the series. The diatomites of Jebel Aoud Sma have been lithologically subdivided into two members. The ichnological results allowed to place them at the top of the first diatomite member of the Lower Cheif basin.The overlying limestones were also subdivided into pre-reef and reef units. They were the site of periodic detrital inputs which reached their maximum in the reef unit. The Halimeda-rich beds; a facies that could constitute an index level known in all the Messinian carbonate platforms of the western Mediterranean was also highlighted. The microfaciological study allowed the interpretation of the depositional environment of the two carbonate units.Also the geochemical results allowed the study of the major element composition of all facies encountered in the grey marls diatomites and limestones.