In West Africa, particularly in the Taoudenni, Volta and Beli basins (southeastern border of the Gourma Basin), Neoproterozoic glaciogenic deposits have been assimilated to the Late Cryogenian «Tillites-Carbonates-Silexites» triad. Like those of the Taoudenni, Volta and Beli basins (southeast of the Gourma Basin), the Neoproterozoic formations of the Firgoun region on the southeastern border of the West African Craton exhibit characteristics of the Neoproterozoic triad. This study aims through sedimentological analysis and lithostratigraphic correlations to place the sedimentary sequences of the Firgoun area in their regional context. The Firgoun deposits, resting in fundamental unconformity on the birimian basement of the Niger Liptako, are essentially composed of quartzite sandstones, conglomerates, shales, silexites and more or less metamorphosed dolomitic limestones. The stratigraphic analysis reveals that the Firgoun deposits include 9 lithofacies from the bottom to the top: the lower lithofacies noted Fr1 to Fr3 have been attached to the base formation called «Firgoun Sandstone», and the lithofacies Fr4 to Fr9 related to the «Beli-Garous» formation. The summit lithofacies (Fr6 to Fr8) of this «Beli-Garous» formation, corresponding to a succession of interbedded diamictites associated with carbonate and silexites deposits, have been assimilated to the Neoproterozoic triad.

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.