Université Abdou Moumouni de Niamey, Faculté de Sciences et Techniques, Département de Géologie, Laboratoire de Géologie: Equipe Bassins et Géoressources, BP 10662, Niamey, Niger
The Niamey sandstones belong to a group of Neoproterozoic (Infracambrian) deposits of the Nigerian Liptako, sporadically outcropping along the eastern edge of the West African Craton and following the Niger River valley. They rest in major unconformity on the Paleoproterozoic (Birimian) basement of the Niger Liptako. Previous work on these deposits has been fragmentary, particularly as regards their structure, and the investigations carried out aim to make up for these shortcomings. The aim of this study is to determine the deformations that have affected the Niamey sandstones. To achieve these objectives, an integrative approach based essentially on analyses and measurements of deformation structures in the field and their projections in the Win-Tenseur program, in order to calculate stress tensors (σ1, σ2, σ3), was implemented. Structural analysis has identified an extensive pre-Pan-African D1 phase, trending NNW-SSE to NNE-SSW, concomitant with the opening of the Neoproterozoic Ocean, and two Pan-African compressive episodes, NNW-SSE to NW-SE trending D2a and ENE-WSW trending D2b.
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