Field mapping and remote sensing investigations reveal two new major fault sets cutting through Tertiary rocks, Quaternary terraces and a several-hundred-year-old irrigation canal system in the Hajar Mountains of northern Oman. They extend for tens of kilometres, forming fracture intensification zones several hundred metres wide. WNW- to NW-oriented faults run parallel to the mountain fronts in the plains adjoining the central Hajar range then obliquely crosscut the mountains in the north. Motion along these faults explains how Quaternary marine terraces became elevated 190 m above sea level. A second fault set strikes north to NNE. The associated juvenile topography suggests that they also accommodate recent uplift, subsidiary to the WNW-striking faults, with minor strike-slip and differential movement between various segments of the Hajar Mountains. Both fault systems, and the amount of Quaternary uplift (between 100 and 500 m), are similar to those in other active and ancient forebulge environments. Using the fracture patterns observed, it is proposed here that the Hajar range lies on the active forebulge of a collision zone between the NE margins of the Arabian plate, the Zagros fold belt and the Makran accretionary prism, which resulted in the recent uplift.

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