Diagenetic Fabrics of Aragonite, Calcite and Native Sulfur in the Miocene Evaporite Cycle on the Red Sea Coast, Egypt PDF

Keywords

fabrics, celestite, cements

Abstract

The fabrics and presence of celestite in the carbonate cements in the reefal limestone of Gebel El Rusas Formation and the sabkha sequences of the Abu Dabbab Formation (Middle Miocene) suggest deposition in a hypersaline vadose regime. The recorded carbonate cements are represented by paleo flowstone crusts; spheroidal and hemispheroidal structures and giant paleo aragonite ray- crystals deposited in fenestrae and as crusts within the Miocene sediments. The carbonate cements occur in the form of polycrystalline calcite pseudo spar and fibrous calcite resulting formed as paramorphic replacements of aragonite in a Mg poor fresh water vadose regime. Traces of native sulfur occur together with secondary gypsum and calcite in the suricial layer of the Abu Dabbab evaporites. The sulfur is formed in a localised microenvironment in the fresh water vadose regime and is a response to bacterial activity on sulfate deposits.