Équipe Bassin et Géoressources, Laboratoire de géologie, Département de Géologie, Faculté des sciences et techniques, Université Abdou Moumouni, Niamey, Niger
The Niamey area lies on the south-western edge of the Iullemmeden Basin. The Continental terminal 3 (Ct3) formation, the subject of this study, represents the last infilling deposits of this basin. In order to determine the depositional environments of the Ct3 formation in the Niamey area, a methodological approach based on field data analysis followed by laboratory analyses was implemented. The main objective of this study is therefore to improve the knowledge of the sedimentary dynamics of Ct3 deposits in the Niamey area. Specifically, the aim of this study is to determine the Ct3 depositional environments. Sedimentological analysis enabled us to distinguish five (5) facies labelled F1, F2, F3, F4 and F5. These facies consist of alternating clayey sandstones and ferruginous lateritic oolitic sandstones with indurated levels, locally showing sandstones levels with unclear oblique bedding. The presence of casts of Gastropods, Lamellibranchs and Echinoderms indicates that the Ct3 deposits were emplaced in a shallow, lagoonal to lacustrine freshwater basin subject to fluvial inputs.
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