Plain Language Summary
Eastern Arabia was thrusted by the well-known Semail Ophiolite and related deep-sea sedimentary rocks during the Late Cretaceous. Convergence was directed towards the SSW. Ongoing ~N/S shortening between Arabia and Eurasia resulted in respective deformation within the Oman Mountains. However, field evidence indicates that ~E/W-shortening affected the Oman Mountains, too. Detailed and comprehensive field survey, literature review, satellite image interpretation, map interpretation, GPlates reconstruction and absolute U-Pb dating of carbonates documents that E/W-shortening was significant in the Oman Mountains. E/W-shortening of 100-135 km was related to the counter-clockwise rotation of India with respect to Arabia at 32.5 to 20 Ma. In response to this shortening, a NW-striking sinistral shear zone with wrench-fault assemblage formed in the eastern Oman Mountains (i.e., N/S-compressive structures, E/W-extensional structures, WNW-striking sinistral Riedel faults, and SW-striking dextral anti-Riedel faults). This shear zone is the Hajar Shear Zone, which spans an area of 250 km by 50 km. Presumably NW-striking deeply rooted pre-existing faults facilitate shearing along the Hajar Shear Zone. E/W-shortening also affected the northern Oman Mountains and is responsible for deformation at the Hagab Thrust in Musandam and the Jabal Hafit Anticline at the Oman/UAE border.