Contribution to the biostratigraphy of the Middle-Upper Eocene rock units at North Eastern Desert; an integrated micropaleontological approach

Foraminifera and calcareous nannofossils have been integrated to improve the biostratigraphy of the Middle-Upper Eocene rocks at North Eastern Desert. Biostratigraphic analysis has enabled the identification of three planktic biozones, Globigerinatheka kugleri/Morozovella aragonensis (E9), Morozovelloides crassatus (E13) and Turorotalia cerroazulensis pomeroli/T. cerr. cerroazulensis. Meanwhile, the occurrence of calcareous nannofossils Reticulofenestra dictyoda, Pontosphaera multipora and Reticulofenestra umbilica within Morozovelloides crassatus Zone (E13) were attributed to Discoaster saipanensis Zone (NP17). Furthermore the quantitative analysis of small benthic foraminifera suggests four benthic assemblages (abundance zones) which correlated with their equivalents in the study area and neighboring areas. Therefore, a Middle Lutetian age (∼45.8 Ma) is proposed for Observatory Formation which dated back to the Bartonian. While, the Qurn Formation is assigned to late Bartonian-early Priabonian age with paraconformity (∼3.6 Ma) between the Observatory and Qurn formations as the result of tectonic instability at the late of Lutetian age. All of the recorded planktic species discontinue at the upper Eocene Maadi Formation of Priabonian age where the environment turned more shallowing inconsistent with planktic habitat. The Lutetian/Bartonian and Bartonian/Priabonian stage bounderies have been also discussed.