Multi-scale Sedimentological and Structural Characterization of Triassic Siliciclastic Systems in the Tim Mersoï Basin, Northern Niger

Abstract

The present study on the Triassic siliciclastic systems of the Tim Mersoï basin aims to characterize the sandstones of this formation from a sedimentological and structural perspective. The study area covered by this work corresponds to the central part of the basin and extends from the Goufat sector (Agadez) to the Dajy-Azélik zone. This area is very interesting because it corresponds to the part where the Téloua formation is most exposed. The methodology used in this study consisted of fieldwork to map this formation, followed by laboratory work combining microscopic analysis (optical, SEM, and microprobe). The mapping showed that the Téloua formation outcrops discontinuously in a generally NS direction. Three recognized lithological units were identified (Téloua1, Téloua2, and Téloua3). Sedimentological analysis carried out through boreholes revealed significant variations in thickness and facies. Macroscopic and microscopic examination made it possible to identify the different petrographic facies of each lithological unit. For the Téloua 1 unit: three (3) facies have been identified. These are Quartzarénite, Arkose, and arkose-lithics. For Téloua 2: two (2) facies have been identified, namely quartzarenite and litharenite. And for Téloua 3: three facies have been identified, corresponding to quartzarenite, litharenite, and analcimolite. From a structural point of view, the Téloua formation has shown the existence of brittle and mixed tectonics. The microstructural analysis carried out showed that the Téloua sandstones exhibit bands of cataclastic and non-cataclastic deformation, with reactivation phenomena that may promote fluid circulation and mineralization trapping.