The Oko Shear Zone, Sudan: Post-Accretionary Deformation in the Arabian-Nubian Shield

The Oko Shear Zone is a late Precambrian, N- to NW-trending, post-accretionary deformational belt in the Red Sea Hills of the Sudan. It left-laterally offsets the c. 800-750 Ma old, NE-trending Nakasib suture by about 10 km. The Shear Zone evolved through three phases of deformations: (1) an early E-W-directed flattening deformation which produced N-trending upright folds; followed by (2) major NW-trending, left-lateral and, minor NE-trending, right-lateral strike-slip faulting; and (3) late E- and W-verging thrusts and buckles associated with a flower structure.
The structural similarities between the Oko Shear Zone and other post-accretionary deformational belts in the Arabian-Nubian Shield suggest an evolutionary sequence for these belts: (1) suturing events were completed by c. 700 Ma ago 'and resulted in the formation of E- to NE-trending ophiolite-decorated sutures; (2) an E-W-directed flattening deformation was superimposed due to collision of the Arabian-Nubian Shield with the Nile craton in the west and the Ar Rayn micro-plate to the east at c. 670-610 Ma ago; this produced discrete zones of N-trending upright folds; (3) the flattening deformation culminated in the initiation of major NW-trending, left-lateral, and minor NE-trending, right-lateral strike-slip faults as conjugate sets at c. 640-560 Ma ago.