Foraminiferal assemblages, biostratigraphy and palaeoenvironmental reconstruction of Pliocene deposits from the Western Sahel Kolea area, Northern Algeria

A complete series of Pliocene sediments crops out in the Kolea area of the western Sahel in northern Algeria and has been previously divided into four informal units. Biostratigraphic analysis of planktic foraminifera allowed the identification of four biozones of the Zanclean-Piacenzian interval including the Globorotalia puncticulata (d’Orbigny), Globorotalia margaritae (d’Orbigny), Goborotalia crassaformis (Galloway) and Goborotalia inflata (d’Orbigny) zone. The combination of quantitative and qualitative data of microfaunal associations, faunal indices (index of oceanity, P/B ratio, species richness and abundances), and compositional analyses of benthic foraminiferal associations indicates a palaeoenvironmental transition from a relatively deep environment during the Zanclean, to a shallower and finally coastal, infralittoral environment in the Piacenzian. The shallowing-upward transition and decrease in water depth are shown to be contemporaneous with the Piacenzian regression.