Possible eastward tectonic transport and northward gravitational tectonic collapse in the Arabian-Nubian shield of western Ethiopia

The Neoproterozoic low-grade volcano-sedimentary and medium to high-grade gneissic domains in the Galesa area of western Ethiopia, which represent part of the Arabian-Nubian Shield, are separated by NNE-trending thrusts that are often marked by transposed mafic-ultramafic assemblages. These litho-tectonic domains preserve early Neoproterozoic east-west shortening deformations in the form of east-facing recumbent isoclinal folds and east-verging thrusts with mylonitic fabrics containing down-dip stretching lineations along discrete shear zones within the metavolcano-sedimentary domains. These early structures are re-folded by N-trending, E-verging tight to open upright map-scale folds. The E-W shortening and thrust stacking culminated with the development of the N-trending sinistral strike-slip Baruda shear zone and lithospheric thickening and exhumation, and subsequent development of low-angle normal-slip shearing along the ENE-trending Donbon shear zone interpreted to have developed during orogenic extensional collapse. (C) 2007 Elsevier Ltd. All rights reserved.