DIAGENESIS OF PLEISTOCENE REEF-ASSOCIATED SEDIMENTS FROM THE RED-SEA COASTAL-PLAIN, EGYPT

Pleistocene reef-associated sediments from the Red Sea coastal plain of Egypt consist of carbonate to mixed carbonate-siliciclastic sediments. The recognized facies are calcareous sandstone, skeletal rudstone, grainstone, wackestone and micritic crusts. Evidence from cement fabrics (aragonite, high-Mg calcite and gypsum) suggests that cementation mainly occurred in the intertidal zone under marine vadose conditions. However, the interaction of these sediments with meteoric waters resulted in the modification and stabilization of the metastable carbonates, the replacement of detrital feldspars by carbonates and the silicification of carbonates.