Foraminiferal biostratigraphy and paleoenvironment of the middle and Upper Eocene succession at Cairo - Helwan area, north Eastern Desert, Egypt

The foraminiferal content of the Middle and Upper Eocene rocks in the area to the east of Cairo-Helwan road studied in details in the present work. A rich benthic foraminiferal assemblages were identified and systematically classified, where 178 species and subspecies, belonging to 79 genera, 47 families and 22 superfamilies were recorded from seven selected surface sections. The studied succession is lithologically described and subdivided into three rock units, which are from the base: Observatory Formation, Qurn Formation (Middle Eocene) and Maadi Formation (Upper Eocene). The vertical distribution of the identified foraminiferal species participated in subdivision the studied sequence into seven local small benthic biozones which are: Elphidium cherifi, Quinqueloculina seminula, Nonionella africana, Brizalina cookei, Nonion scaphum zones (Middle Eocene), Bolivina carinata and Halkyardia minima zones (Upper Eocene). These biozones were described, discussed and correlated with their equivalent in different localities in Egypt. The identified planktonic species are few and scattered through the succession, and so not taken into consideration in the biostratigraphic classification. The statistical analysis of the identified benthic foraminiferal assemblages, besides the lithologic characters are used in interpreting the paleoecology and environmental conditions that were prevailed during the deposition of the studied rock units, where a warm, hypo-to hypersaline inner to middle shelf environment with high to moderate oxygen conditions and water depth fluctuated between 30 and 100 m are the most characteristic paleoecological conditions for the studied succession.