Lithostratigraphy and facies development of the Neogene-Quaternary succession in the Marsa Alam area, Red Sea coastal plain, Egypt

The Neogene-Quaternary sedimentary succession in the Marsa Alam area, Red Sea coastal plain, Egypt has been studied. Lithostratigraphically the rock units are classified into the Um Mahara, Abu Dabbab and Samh Formations of Middle to Upper Miocene age, the Gabir and Shagra Formations of Pliocene age, the Plio-Pleistocene Samadai Formation, and the Quaternary raised beaches, coral reef marine terraces, beach rocks, tidal flat and alluvial deposits. The detected elastic lithofacies include petromictic conglomerates, sandstones, siltstones and shales. The sandstone microfacies are calcareous quartz arenite, lithic arenite, subarkose, arkose and greywacke. The non-elastic lithofacies are evaporites including gypsum and anhydrite, and limestones. The limestone microfacies are mudstone, grainstone (oosparite, oo-biosparite, foraminiferal biosparite, coquinal biosparite and algal biosparite), boundstone (bindstone and framestone), and rudstone (biosparrudite). The changes in lithology and microfacies suggest changes in the depositional environments from continental terrestrial, fluvial, to open, shallow marine intertidal, supratidal and lagoonal conditions, associated with climatic changes from hot-dry to warm-wet. The variability in distribution and deposition of these rock units appear related to the rifting of the northern Red Sea and/or sea level changes.