MIOCENE EVAPORITES OF THE RED-SEA RIFT, YEMEN-REPUBLIC - SEDIMENTOLOGY OF THE SALIF HALITE

Miocene evaporites are spectacularly exposed along the Red Sea coastal plain of Yemen, especially in the region of Salif. Over one thousand metres of bedded halite containing regular millimetre-thick laminae of anhydrite were precipitated below wave base (which need not have been very deep) in a relatively quiet and protected basin, virtually cut-off from the open sea of the Mediterranean and Indian Ocean. A metre-thick unit of laminated and rippled anhydrite within the halite is the result of a major decrease in salinity within the basin. Gypsum overlying the halite is bedded and laminated, but does contain vague vertical structures suggestive of an original selenitic mineralogy. This sulphate was probably precipitated as bottom-growth gypsum and decanted crystals. More open circulation in the basin was established in the Early Pliocene when carbonate muds and siliciclastics were deposited. These Miocene evaporites were precipitated during the continental rifting and opening of the Red Sea-Gulf of Aden when half-graben structures were formed and fed by occasional influxes of marine water. Subsequent sedimentation and tectonic deformation led to major halokinesis, the development of diapirs and exposure of the halite along the coastal plain.