Introduction to the carbonate microfacies of the Farasan Islands, southern Red Sea

Microfacies analysis of the Farasan Islands sediments was carried out to unravel the depositional environment and evolution of the area. Thin section petrographic studies were carried out to expand on the field identifications, to study the composition and to classify the Farasan Islands rock units. Sedimentological characteristics and depositional settings were also established. Several fossil assemblages have been identified, including Forams, Algae, Corals, Mollusks, Ostrocods, and Ooids. The most common diagenesis processes observed were dissolution and replacement by gypsum and anhydrite. The carbonates of Farasan Islands show normal shallow marine processes. Shale and anhydrite sequences were deposited most likely in subtidal to open marine environments. Progressive shallowing of the depositional environment is illustrated by the evolution of sedimentary facies in the Farasan Islands from low energy subtidal to open marine and finally to high energy at the top of the sequence. Field observation of palaeoshorelines may reflect the control of sea-level changes on reef formations during the Plio-Pleistocene time in the Red Sea.