Orogen-parallel tectonic transport: transpression and strain partitioning in the Mauritanides of NE Senegal

Abstract

AbstractNew structural, metamorphic, finite-strain analysis and kinematic data from the southern part of the Mauritanides in Senegal (Bakel area) have revealed a history reflecting different tectonic regimes. The structural framework is expressed in the form of shear-zone systems comprising rectilinear NE–SW trending thrusts and NE–SW-trending ductile sinistral strike-slip faults associated with north–south- to NE–SW-trending transpression belts. The analysis of ductile fabrics reveals the presence of lineation trajectories that show a change from a tangential deformation towards the marginal zones in the Northern and Southern Domains of the belt to sinistral oblique transpression in the Central Domain. The deformation within the belt is strongly partitioned into shear zones distributed across the belt defining structural domains with accompanying large-scale folds and thrusts. This exemplifies wrench-style tectonics dominated by crustal-scale strike-slip shear zones in the orogen core and temporal and spatial progression outwards to the marginal zones. Thus, the Variscan orogeny in the southern part of the Mauritanides belt in Senegal developed through sinistrally oblique transpressive shearing along the borders of the orogen core leading to the exhumation of ultramafic rocks between large shear zones.