Geology of the Shuwaihat 1:100 000 map sheet, 100-32 (and the Islands of Delma, Zirku, Qarnain and Arzana at 1:50 000), United Arab Emirates

Thomas, R.J.; Ellison, R.A.; Goodenough, K.M.; Farrant, A.R.; Newell, A.J.. 2012 Geology of the Shuwaihat 1:100 000 map sheet, 100-32 (and the Islands of Delma, Zirku, Qarnain and Arzana at 1:50 000), United Arab Emirates. Nottingham, UK, British Geological Survey, 57pp.

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This Sheet Description describes the solid and Quaternary geology of the Shuwaihat area and the salt islands of Delma, Zirku, Arzana and Qarnain (at 1:50 000 scale). The two small islands of Yasat Ali and Yasat Safli were also mapped. The mainland area shown is quite small (115 km2), but is geologically important in that it contains the Type Sections of the Miocene Shuwaihat Formation and the Barakah Member of the Baynunah Formation, on Shuwaihat Island and Jebel Barakah respectively. Some 300 observation points were made throughout the district. The oldest rocks in the area are those of the Neoproterozoic Hormuz Complex, exposed on the four salt islands included on the map. The islands are cored by salt domes with excellent outcrops of the Hormuz breccias. These were mapped at 1:25 000 scale and large clasts >100 m across have been shown on the map as igneous, sedimentary and undifferentiated megaclasts. Two metamorphic rock clasts were recorded and detrital zircons from one of these, a layered marble from Delma, constrained the maximum age of deposition of the original sediments at 590 ± 2 Ma. The island of Zirku is unique in that it contains extensive outcrops of deformed turbiditic rocks, termed the Zirku Formation, which form a semi-continuous carapace over Hormuz breccia. U-Pb dating of detrital zircons of a sandstone unit in the formation determines a depositional maximum age of 560 ± 19 Ma. U-Pb zircon dating of a felsic volcanic igneous clasts from Qarnain yielded a Neoproterozoic (Ediacaran) crystallisation age of 561 ± 16 Ma, suggesting that volcanism was penecontemporaneous with sedimentation. The salt domes are unconformably overlain by Quaternary pale cream-coloured carbonate grainstones and gravels of the Jebal Dhanna Formation, which are deposits unique to the salt domes. The salt domes were injected into Miocene strata which underlie most of the area. Recent movements of the salt diapirs are represented in numerous ‘salt blisters’ seen on many of the islands. The oldest Miocene rocks in the district, marine sedimentary rocks of the Gheweifat Member of the Dam Formation, outcrop on the two small Gulf islands of Yasat Ali and Yasat Safli. Over the rest of the area, the oldest Miocene rocks belong to the Shuwaihat Formation, which consists of highly variable sequence of fluvial, aeolian, terrestrial playa and continental sabkha red-bed siliciclastic sediments, well exposed in a number of sections on Shuwaihat Island, Jebel Barakah and on Delma. The Shuwaihat Formation is unconformably overlain by the Barakah Member of the Baynunah Formation, also well exposed in sections on Shuwaihat Island and Jebel Barakah. It comprises a sequence dominated by fluvial sandstones, with channel lag conglomerates particularly common near the base, where fossilised bone, wood and egg shells are locally abundant. The topmost few metres of strata on Jebel Barakah are made up of greyish green carbonate siltstones of the succeeding Habshan Member.

Item Type: Publication - Book
Programmes: BGS Programmes 2010 > BGS Corporate
ISBN: 9780852727386
Funders/Sponsors: Ministry of Energy United Arab Emirates
Additional Information. Not used in RCUK Gateway to Research.: This item can be purchased by the
NORA Subject Terms: Earth Sciences
Date made live: 02 Aug 2012 15:12

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