The structural evolution of the Diale-Dalerna basin, Kedougou-Kenieba Inlier, eastern Senegal

The Diale-Dalema group is located in the eastern part of the Kedougou-Kenieba Inlier (KKI) and is essentially composed of Paleoproterozoic rock formations. Lithostructural studies in this area, hassuggested, often controversial, deformational regimes and geodynamic evolution models. In this study, we suggest the existence of an initial tangential D-1 deformation and transpressional D-2 deformational phases. D-1 is characterized by an initial metamorphic schistosity denoted as S-1 and by F-1 folds with the main shortening stress direction generally oriented in NW-SE direction. D-2 in the study area is divided into two stages. The first stage designated as D-2a is coaxial and compressive in nature. It is characterized by a N-S to NNE-SSW trending metamorphic schistosity termed 5(2a). The D-2a phase evolves gradually to a transcurrent phase connoted as D-2b and characterized by a NNE-SSW S-2b metamorphic schistosity which is axial planar to the F-2b folds with subvertical fold axes. During the D-2 phase, the main shortening stress direction rotates gradually in a clockwise motion from an E-W to a NW-SE direction within a continuum of deformation. The third deformation phase D-3 in the Diale-Dalerna basin, is also divided into two stages, thus D-3a and D-3b. D-3a is transcurrent and transtensive in nature and is characterized by NE-SW sinistral shear corridors with local extensional jogs. During this deformation stage, the maximum shortening stress (sigma(1)) direction acts in a N-S direction and rotate to a NE-SW direction, thereby creating a N-S transcurrent dextral shear corridors. D-3b component of the D-3 deformation is compressive in nature with a weak sinistral shear component. The D-4 corresponds to a N-S extensional phase which is characterized by E-W directed normal faults. D-4 in the study area denotes the final stage of the evolution of the Eburnean orogeny in the KM. (C) 2017 Published by Elsevier Ltd.