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Abstract

Plate-tectonic movements made the Cretaceous a time of major change in the area of the modern Oman and Zagros Mountains. Neo-Tethys 1 had been created in the Late Permian by the calving of a microcontinent (Anatolia, Sanandaj–Sirjan/Central Iran) along the NE margin of Arabia. In the Late Triassic, a second spreading axis, Neo-Tethys 2 (more readily recognizable in Iran than in Oman) replaced that of Neo-Tethys 1 by the separation of the Central Iran and Sanandaj–Sirjan–Kawr microcontinents.

Neo-Tethys 1 had a passive continental margin during the Triassic and Jurassic as the Afro–Arabian portion of Gondwana moved westward away from the actively spreading oceanic ridge of Neo-Tethys 2. Shallow-marine sediments along the continental margin were the source of carbonate turbidity currents that flowed basinward to the abyssal plain of Neo-Tethys 1 until the early Late Cretaceous, whereas the floor of Neo-Tethys 2 seems to have been starved of coarse sediment in its Oman sector.

Early in the Cretaceous, the South American and Afro–Arabian portions of Gondwana began to separate to create the South Atlantic Ocean. South America continued to move to the west, but Afro-Arabia reversed its sense of motion. The ensuing buildup of horizontal compressional stresses led to an eastward-dipping subduction zone within the Oman sector of Neo-Tethys 2, leading to obduction of the Late Permian to mid-Cretaceous Hawasina Series (deposited in Neo-Tethys 1) and the Semail Nappe, which was generated by back-arc spreading. North of the Dibba Line, subduction also took place within Neo-Tethys 1.

The latest Cretaceous was a time of tectonic adjustment and shallow-marine carbonate sedimentation across the area of the present Oman Mountains and southern Zagros, but the effects of late Maastrichtian subduction in Neo-Tethys 2 are visible in the Inner Makran. Evidence of subduction beneath the northern half of the Gulf of Oman suggests that this process has been more or less continuous over the Makran area until today. Uplift of the Oman Mountains began in the Mio–Pliocene, about the same time as the Zagros Mountains began to form.

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