Upper eocene calcareous nannofossil biostratigraphy: A new preliminary priabonian record from northern Saudi Arabia

Abstract

The current research work represents the first calcareous nannofossil biostratigraphic record of the upper Eocene Rashrashiyah Formation in northern Saudi Arabia. The Rashrashiyah Formation is an Eocene carbonate sedimentary unit, exposed adjacent to the Jordanian border, and yielded rich and diverse nannofossil assemblages. The Rashrashiyah Formation overlies the Paleogene rocks of the Umm Wu’al Formation and is unconformably topped by the Neogene (Miocene) Sirhan Formation. Our nannofossil biostratigraphic data recognized 44 species belonging to 21 genera. These taxa indicate a Priabonian age based on the presence of Chiasmolithus oamaruensis, and the recognition of bioevents in concordance with the global Priabonian zonations. Three comparable major zones and zonal boundaries (CP14b/CP15, NP18, and CNE17) were recognized in the study section indicative of a late Eocene age. The Base common (Bc) of Reticulofenestra erbae was detected at the same level as the top of Chiasmolithus grandis, supporting the bioevent reliability in the Tethys realm. A single and more isolated occurrence of Isthmolithus recurvus was observed within Zones CP15 and NP18 at the maximum increase abundance of R. erbae. Our calcareous nannofossil biostratigraphy from the Rashrashiyah Formation has coincided with the assignment for units 2 and 3 of the Wadi Esh-Shallalah Formation in Qa’ Faydat ad Dahikiya in the eastern desert Jordan.