The Neogene Split From Africa: The Arabian South and Southwest Margins
The Arabian south and southwest passive margins evolved during the Neogene as a result of Eocene-Oligocene extension, rifting and breakup of Afro-Arabia. Separation of Arabia away from Africa followed as a consequence of sea-floor spreading in the Gulf of Aden. This spreading propagated to the Red Sea and rotated Arabia in a counter-clockwise direction, simultaneously moving it northward along the Levant Fracture (Dead Sea transform), which became the new northwest Arabian plate margin.
The Gulf of Aden opened initially, it appears, because of the westward propagation of the spreading Indian Ocean Carlsberg Ridge. This propagation was accompanied by an increasing component of compression developing along the Owen Fracture Zone (OFZ) transform in response to a sharp change in spreading direction during the earlier Eocene (Moseley and Abbots, 1979). The Sheba Ridge of the Gulf of Aden only developed when sea-floor spreading became established in the Miocene, and it constitutes a dextrally offset extension of the Carlsberg Ridge on the west side of the OFZ. By contrast, as yet the Red Sea has no central ridge but has only an axial trough principally in the southern and central portion, which is a current site of high heat flow (Figures 1 and 24).
Researchers have proposed a number of models for the evolution of the Gulf of Aden and the Red Sea. To date, these researchers dispute such points as whether, once sea-floor spreading commenced, it was episodic or continuous; whether the crust under the Red Sea is oceanic across much of
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Arabian Plate Hydrocarbon Geology and Potential—A Plate Tectonic Approach
Reported proven hydrocarbon reserves of the Arabian plate region at the start of 1991 totaled 663.2 billion barrels (B bbl) of oil and 1,325.4 trillion cubic feet (tcf) of gas (66.4% and 31.5% of the world's oil and gas reserves, respectively). More than 98% of these are concentrated in the northeast margin region between northwest Iraq and Central Oman and lie in reservoirs ranging in age from late Paleozoic to early Neogene. Additional reserves, however, increasingly are being established along the other Arabian plate margins and in intra-plate basins. Occurrence of reserves, age and distribution of the sediments that generated or preserved them, and the formation of the mainly large structural (and other) traps are linked intimately to differing histories of plate margin evolution. The proper understanding of these histories could lead to additional reserves being established. The Arabian plate margins evolved at different times, the first being the northeast passive margin. This permitted the almost uninterrupted accumulation of thick sediments over a vast area including areally extensive organic-rich source rock deposits as well as good reservoir and seal units. The north/northeast margin(s) became a col-lisional boundary and a new Levant margin became a transform boundary in the Neogene.
Consolidation of the Afro-Arabian craton in the latest Proterozoic and Early Cambrian created a prominent north-south basement “grain” and a northwest-southeast (Najd) shear fracture system. Rejuvenations (affecting structures/sediment patterns) occurred in later periods and have controlled major hydrocarbon occurrences.
From latest Proterozoic to late Paleozoic time, the present north/northeast Arabian plate margin region, Anatolia, central Iran and the Afghan and Indian plates formed part of the long and very wide northern passive margin of Gondwana. This region was intermittently covered by shallow epeiric seas and bordering lowland.