ABSTRACT
The Red Sea and Arabian (Persian) Gulf have quite contrasting geological environments; the former is an active spreading zone in the early stages of forming an ocean basin, while the latter lies over a stable Phanerozoic sedimentary platform that collides with the Zagros Fold and Thrust Belt to the east in Iran. The Red Sea formed by the splitting apart of the Arabian-Nubian shield that started with continental rifting in the Oligocene (about 30 Ma) and opening up of the northern part of the Red Sea at 20 Ma in the Miocene. At present, the central spreading axis is opening at an average rate of about 1.6 cm/year, varying from 0.7 cm/year in the north and up to 2.4 cm/year at the southern end due to the rotation of the Arabian plate (Reilinger et al. 2015). This variation is indicated by the width of the Red Sea between the topographic shoulders of the Precambrian basement, which are about 200 km apart in the north at latitude 27°N and 350 km apart in the south at latitude 17°N. Although it is generally accepted that true oceanic seafloor spreading is now occurring in the southern Red Sea since about 5 Ma, there is much continuing debate as to whether extension in the north is still by stretching and thinning of the continental crust, with only incipient oceanic spreading, or whether the seafloor is in fact at least partially underlain by oceanic crust.
