Late carboniferous dextral wrench-dominated transpression along the North African craton margin (Eastern High-Atlas, Morocco)

The Paleozoic terranes of the Moroccan Eastern High-Atlas crop out mainly in the Tamlelt inlier. Two structural domains are recognized: (i) the Northern Domain, primarily structured by N-S Eovariscan polyphased structures (D1 and D2) overprinted by a E-W D3-deformation allotted to a late Carboniferous phase; (ii) the Central-Southern Domain (CSD) only deformed by D3. This paper focuses on the CSD (100 x 40 km) which shows, on the large-scale, a typical S-C structure simultaneously developed during D3, in a principal ductile-brittle shear zone. Second-order shear zones subparallel to the principal one and limited by Shear bands (SB) are also recognized. The N70-90degrees trending F3-folds and late imbricate structures have a weak general southern vergence. Strain analysis generally shows a planar finite strain ellipsoid and a vertical foliation-horizontal lineation fabric. This fabric and different scales of structures show that D3-deformations were generated by dextral wrench-dominated transpressional tectonics. The CSD displays a large degree of displacement partitioning and efficient slip on the E-W SB. Consequently, we suggest that the D3-structures developed in the late Carboniferous, during an oblique convergence and massive dextral transpression event, as the Moroccan Mesetian domains slid along the North African craton boundary. The oblique convergence may have been related to the indentation model, and the location of the Tamlelt inlier along the northwest African craton. The suggested dextral transpression during the Tamlelt Hercynian evolution of SE Morocco is related to the geodynamic model of a West European and Laurentian promontory indenter. (C) 2003 Elsevier Ltd. All rights reserved.