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Outcrop, Mine and Borehole Studies |
1 Department of Geology, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
2 Department of Geology, Sana’a University, Sana’a, Republic of Yemen
The Al Salif and Jabal al Milh salt diapirs of Miocene age cut through a 4–5 km thick overburden of Miocene to Recent sedimentary rocks in the southern Red Sea. The Al Salif diapir is part of a north-south oriented diapiric wall which has caused updoming of the overburden and active extensional faulting. The halite is folded into tight to isoclinal subvertical folds, with largescale rafts of interbedded gypsum-anhydrite boudinaged on the fold limbs. There is no evidence for large-scale overburden stoping or injection of salt into overlying faults and fractures, and the upward movement of the salt dome is probably caused by the overburden being forced aside and sliding off the dome. The upper surface of the salt is an undulating smooth surface which was exposed at the sea-floor during the Quaternary. Coral reefs with 14C ages of 3700 a have been raised up to an elevation of 17 m above present-day sea-level, giving a surface uplift rate of 4.6 mm a–1. At the Jabal Al Milh diapir, recumbent folding and thrusting are the main deformation features observed in the siltstones and gypsum layers of the overburden. The overburden has been rotated to the vertical at least 200 m from the diapir walls. The folding and thrusting is interpreted to be caused by overflow of salt in a namakier. This study shows that overburden sediments above the Al Salif diapir extended to allow sediments to slide from the salt dome crest by listric faulting, whereas sediments underlying the Jabal al Milh salt glacier were sheared and shortened in the horizontal direction.
