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

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