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.

Multi-channel seismic and well data from Agadem (Termit Basin), a Mesozoic–Cenozoic intra‐continental rift basin located in the West and Central African Rift System (WCARS), has been analyzed. Regional unconformities, including the top of acoustic basement, have been identified from seismic data. The correlation of wells in the Agadem Block, as well as the seismic data interpretation, show that the lateral thickness variations of the layers is linked to the synsedimentary normal activation of the N140° to N150° trending fault system of the Termit Basin. The well logs correlation exhibits a high hydrocarbon potential, in the axial zone of the Agadem Block, which is characterized by a strong subsidence rate. This study shows that the NW-SE-trending graben shaped Termit Basin exhibits a tilted block structuring, controlled by the synsedimentary reactivation of normal faults. Two major periods of structuring characterize the evolution of the Termit Basin: - The first period, which was an extension stage, including the first rifting stage relayed by a thermal subsidence, occurred from early Cretaceous to Upper Cretaceous, during the south Atlantic opening. - During the second period, which prevailed from Paleocene to Oligocene, the Termit basin was also affected by a second rifting event, followed by a thermal tectonic subsidence. The NW-SE trending faults was secondly reactivated during a NE-SW extensional regime.

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.