Radwany Formation: A new formation name for the Early-Middle Eocene carbonate sediments of the offshore October oil field, Gulf of Suez: Contribution to the Eocene sediments in Egypt

Abstract

The Eocene sediments plays critical role in the evolution and development of the petroleum system in the Gulf of Suez region, where it is representing a self-source rock or self-reservoir or combination in some areas within the basin. Microfacies analysis and paleontological studies have not been conducted on these Eocene sediments in the area of the October oil field, which is mandatory for the formation characteristics assessment. Therefore, sidewall core and ditch-cuttings samples that was obtained from October Eocene carbonate sediments so far ascribed to the Thebes formation was studied in terms of sedimentology, paleontology and depositional environment. A total of 64 thin sections were analyzed petrographically, and three microfacies types recognized. Both Calcareous nanoplankton and Foraminifers were examined. The study of the Eocene carbonate facies in the October field revealed that the succession is composed of pelagic foraminiferal limestone of varied color, containing abundant planktonic foraminifers and minor traces of chert. Three microfacies are distinguished including wackestone of smaller planktonic foraminifera (50%), wackestone-packstone of planktonic foraminifera (40%) and packstone of planktonic foraminifera (10%). Nannoplankton and foraminifers indicate that the studied succession is of early Eocene to middle Eocene age. Microfacies and fossil assemblage of the studied section indicate a pelagic environment and deposition in deep basin at water depths of a few hundred meters. Finally, the current results were compared with data from previous publications on Eocene sediments in the region. It is revealed that the studied succession provides new data and contribution for the evolution of carbonate platform in the Ypresian-Lutetian age, and differs from the typical Thebes Formation and other Eocene Formations concerning facies, lithology, fossil content, age and depositional environment. Therefore, we suggest to abandon the term Thebes Formation for this Eocene carbonate succession in the October field, and a new lithostratigraphic unit, named Radwany Formation, is formally introduced.