Coralline Red Algae and Microfacies studies as environmental indicators: A case study from the Gharamul formation, Gulf of Suez Region, Egypt

Abstract

The systematic studies and taxonomic investigations carried out on the Early Miocene GharamulFormation exposed in Gebel Abu Shaar El Qabili plateau, western side of the Gulf of Suez region, ledto the recognition of twelve coralline algal species belonging mainly to five genera of three subfamilies(Mastrophoroideae, Lithophylloideae, and Melobesioideae) of Rhodophyta (Corallinaceae). Thegeniculate coralline algae are relatively scarce and represented by a single genus Corallina sp. TheMastophoroids (Neogonilithon and Spongites) and Lithophylloids (Lithophyllum) are more dominantcoralline algal species and dominate the shallower coralline algal assemblages. On the other hand,Melobesioids (Mesophyllum and Lithothamnion) and sporolithales (Sporolithon) are the most abundantcomponents and diverse in the deeper-water assemblages. The Gharamul Formation (Burdigalian)consists of a thick carbonateclastics succession. The lower part consists of a cyclic sequence oflaminated, fossiliferous and argillaceous limestone intercalated with mudstone, and sandstones. It isdocumented that the clastic microfacies have good reservoir quality in the region due to the impacts ofdissolution and fracturing diagenetic processes. The carbonate microfacies are impervious due to theeffects of cementation, and micritization. The dominance of coralline algae and larger benthicforaminifera indicate deposition in the photic zone. Frequent oscillation of lower-energy (foraminiferalwackestones) with higher-energy (grain-supported grainstones, packstones and rudstone) suggest thelikely incidence of cyclones/storms during the depositional time.