JAES:Oman Exotic limestones in the UAE-Oman border area with implications for Middle-Upper Permian Neo-Tethyan rifting

发布时间:2019-06-24 放大 缩小

The Neo-Tethyan Semail Ophiolite in the UAE-Oman region was obducted onto the Arabian continental margin at the end of the Cretaceous. Beneath the ophiolite are thrust-stacked deep-water Mesozoic and older sediments and volcanics that include marine basalts and associated limestones of Middle-Late Permian and Late Triassic age. These limestones are referred to as the Oman ‘Exotic’ limestones. The Middle-Upper Permian exotics are the rarer exotic type. They were reef build-ups on platforms that sank to ocean depths during rifting, and were later engulfed by intrusive basalts. An area to the east of Al-Ain city, UAE, exposes blocks of richly fossiliferous limestone exotic blocks within Upper Triassic marine basalts. The studied exotics host foraminifera, including Dunbarula mathieui, Verbeekina sp., Tetrataxis sp., Geinitzina sp., Pachyphloia sp., Colaniella leei, and calcareous algae (Mizzia velebitana), rugose corals and abundant crinoids, consistent with a Murghabian-Dzulfian (Middle-Late Permian) age. The exotics lack ooids, show grainstone/packstone lithofacies, are only slightly affected by dolomitization. These features are interpreted in a paleogeographic model, involving an isolated carbonate platform comparable to the Jabal Qamar Formation in the Dibba Zone that subsided during Neo-Tethys rifting in the Late Permian Lopingian (Dzulfian-Dorashamian).