THE DEPOSITIONAL AND DIAGENETIC EVOLUTION OF THE COASTAL RIDGES OF NORTHWESTERN EGYPT

Since the Lower Pliocene successive generations of coastal ridges, mad e up- of mixed oolitic and biogenic grainstones, formed along the Medi terranean coastline of Egypt, west of Alexandria, and have undergone p rogressive stages of diagenesis. The ridges are complex structures, re sulting from several phases of deposition in which shallow-marine comp onents are partially and progressively reworked as subaerial and aeoli an deposits. Diagenetic alteration resulted from increasing freshening of the pore waters in the ridges. Diagenesis began with marine-phreat ic cementation, followed by freshwater-phreatic cements, aggrading rec rystallization of microcrystalline calcite to microspar, and minor dol omitization (non-marine hypersaline diagenesis). Soil profiles develop ed on the upper surfaces of the oldest dunes.