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.

This study concerns the south-central part of the Iullemmeden intracratonic basin. The main objectives of the study were sedimentological analysis of the various facies and preliminary description of the nodules bearing phosphate mineralization in the Agougaran sector (Kao area, northern Ader Doutchi). The phosphate-bearing rocks are phospharudites. These occur as nodules of variable size and morphology. The phosphate nodules are hidden in the marl limestones or in attapulgite schists of the Barmou Member. Attapulgite schists contain the highest concentrations of nodules bearing phosphate mineralization. In the mineralized levels, nodules are either scattered or organized in layers or beds. The faunal association of the Barmou Member, which encases in the mineralized nodules, is made up of nautiluses, bivalves, sea urchins, gastropods, foraminifera and ostracods. This faunal association testifies to the emplacement of phosphate mineralization-bearing deposits in a confined marine environment.

The present study concerns the south-centre of the Nigerien part of the Iullemmeden intracratonic Basin. A multidisciplinary approach involving sedimentological analysis of facies and determination of fossils has been implemented for the characterization and determination of the Maastrichtian to Paleogene paleoenvironments in the Garadaoua and Garadoumé areas. The stratigraphic series of the study area includes, from the bottom to top, the Formations of: Farin Doutchi, In Wagar, Garadaoua and Ader Doutchi (Ct1 or Ar). The Maastrichtian Formations of Farin Doutchi and In Wagar, as well as the Paleocene Formation of Garadaoua are fossiliferous. Indeed, the base of the Farin Doutchi Formation contains bivalves, foraminifera and sea urchins, while, In Wagar contains remains of vertebrates and casts of gastropods. In the Garadaoua Formation, presence of the benthic foraminifer Ranikothalia bermudezi species made it possible to assign to it an Upper Paleocene age. Moreover, the presence in the Garadaoua Formation of the sea urchin Linthia sudanensis species implies, during this periode, the pre-existence of an epicontinental sea in the Iullemmeden basin. Besides, in the Ader Doutchi Formation, the demonstration of α and γ oolites, as well as proto-oolites, testifies an agitated environment with at least two oolithization phases.