Les radiolaires messiniens du Dahra (Bassin du Bas Chélif, Algérie) : systématique et intérêt biostratigraphique

The micropaleontological study of the Upper Miocene diatomites of the Dahra massif at Ouillis and Sidi Lakhdar sections (Lower Chelif Basin, Algeria), allowed for the first time in Algeria, the identification of 36 species and 22 genera of radiolarians dominated by families Actinommidae, Spongodiscidae and Theoperidae. The qualitative and quantitative analyses of the assemblages show significant specific and generic diversification in the first members. Towards the top of the sections, the progressive decrease in diversity and finally, the disappearance of siliceous microfauna are linked to a reoxygenation of the environment. Respect to the biostratigraphy, the radiolarian assemblage identified confirms a Messinian age (Biozone Stichocorys peregrina).