This study was carried out in the south-western part of Niger. The study area corresponds to the Niamey region, which straddles the south-eastern edge of the West African Craton and the south-western terminus of the Iullemmeden Basin. The general objective of this work is to determine the context in which the Ct3 deposits were emplaced in the Tondibia, «Rhodesia» and Kongou sectors. Specifically, the aim is to provide a petrographic description of the Ct3 deposits and to characterise the deformation that affected these deposits. The methodology used is based on the macroscopic and microscopic petrographic description of the samples taken and on structural measurements. Three sedimentological sections were taken from the three outcrops selected (Tondibia, Rhodesia and Kongou). The petrographic study of the Continental Terminal 3 (Ct3) deposits identified several facies whose sedimentological characteristics and number varied according to the sectors studied. The facies identified include: kaolinitic sandstones; ferruginous oolitic sandstones; sandstone clays; conglomeratic sandstones; clays intercalated with ferruginous oolitic sandstones; and iron oxide nodule conglomerates. Microscopic observations made it possible to identify several forms of oolitic concretions, namely: type α oolites (Oα), type γ oolites (Oγ), proto-oolites (PO), oolites of type γ (Oγ), oolites of type γ (Oγ), oolites of type γ (Oγ) and oolites of type γ (Oγ). proto-oliths (PO) and composite ooliths (OC). Tectonic analysis has revealed a NW-SE and NE-SW compressive phase of Oligo-Miocene age that affected the deposits of Terminal Continental 3 (Ct3).

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.