Inter-relationship of Makran-Oman Mountains belts of convergence

Abstract

Abstract Mid Permian rifting and crustal separation along the northern margin of Arabia led to initiation of the Neo-Tethys ocean and deposition of sediments typified by the Hawasina. Subsequently, the Neo-Tethyan oceanic crust was consumed in a late Cretaceous subduction zone, generally easterly dipping in the Oman sector, and its sedimentary cover built up an accretion wedge (Hawasina; Coloured Melange) until the late Campanian, when the buoyant crust of the Arabian continental margin seemingly choked the subduction process. Continuing convergence caused increased activity on, or the creation of, another subduction trench running between and extending south and east of the Central Iran-Lut and Sanandaj-Sirjan microcontinents (the proto-Makran trench). The resulting crustal relaxation on the earlier subduction site permitted uplift of the half-buried Oman continental margin; the overlying Hawasina and former hanging wall of Semail ophiolite then spread gravitationally further onto the Arabian shelf. The Makran accretion wedge of Mesozoic Coloured Melange-type rocks and a thick pile of Maastrichtian to Eocene flysch underlies an ophiolitic hanging wall. Post-Eocene collisions between Arabia, Eurasia and intervening microcontinents resulted in: movement of the Naiband Fault in Iran and associated change in trend of the main subduction trench from NW-SE to E-W; thrusting of the Kahnu-Daragar and Alpine-type ophiolite over the SE Sanandaj-Sirjan Zone and rotation of part of its basement; westward thrusting of Musandam, and was associated with the Oligocene uplift of the Oman Mountains. The Zagros plicate folds began their main development in the Pliocene. Continent-continent collision has not occurred between Oman and the Makran.