Facies development and environments of Miocene reefal limestone, Wadi Hagul, Cairo-Suez District, Egypt

The reef limestones, of Langhian (Middle Miocene) age; were formed during regressive-transgressive episodes. They were subdivided into four main depositional facies: 1) fore-reef, made up of bioclastic marry limestone with broken skeletons and debris, 2) reef-core, constructed of a framework exclusively of branched colonies of Porites sp. coated by micrite submarine cements, 3) back-reef, consisted of friable limestone, rich in shell hash with flodded Heterostegina praecostata and, 4) beach and nearshore, made up of fossiliferous cros-bedded pebbly sandstone. The complete leaching and alteration of the original aragonitic scleractinian corals microstructure, and the cements into low Mg-calcite mosaic by fresh water in the subaerial environment, is the main diagenetic process which affected the reef. Micrite is the most important constituent in the reef-core sediments (40 -70 \%) and allover the sequence in general.