Plate Motions Around the Red Sea Since the Early Oligocene

Abstract

The Red Sea represents a very young oceanic basin that formed between Nubia and Arabia since chron C3 (~4.6 Ma). The rifting phase started at ~30 Ma (early Oligocene) and can be represented by two kinematic stages, characterized by distinct directions of extension and different duration. Deformation associated with rifting was accommodated through the reactivation of the inherited Proterozoic structures. We show that the first stage was characterized by the northward motion of the Arabian plate with respect to Africa, accompanied by a pattern of deformation that included N–S oriented strike–slip faults and normal faults having E–W strike. During this stage, extension was mainly accommodated by the formation of pull–apart basins. Starting from ~27 Ma (late Oligocene), the extension axes changed dramatically and acquired the modern NE–SW pattern, which was conserved until the early Pliocene in the southern Red Sea and is still active in the northern region. In this time interval, an inherited system of NW–SE structures was reactivated as normal faults accommodating NE–SW extension, while NE–SW Proterozoic structures were reactivated as transfer strike–slip faults. Although no changes in the directions of extension are observed during this interval, two significant tectonic events occurred around 14 Ma and at 1.77 Ma. During the Langhian, two intervening microplates formed between Nubia and Arabia; the Danakil and Sinai microplates, whose motion determined the formation of the Afar Depression and the Gulf of Aqaba, respectively. Finally, starting from the Pleistocene, ongoing collision of Arabia with Eurasia along the Zagros mountains resulted into a dramatic slowdown in the Red Sea opening rates.