Calcareous Nannofossil Stratigraphy across the Paleocene-Eocene Transition at the Gunnah Section, Farafra Oasis, Western Desert, Egypt

Abstract

Calcareous nannofossil, carbonate content, and δ18O and δ13C data were utilized to reveal the nature of the Paleocene-Eocene (P-E) boundary at the Gunnah section, Western Desert, Egypt. The uppermost Tarawan Formation (Fm.), Esna Fm., and the lowermost, Farafra Fm., were included in this study. Lithostratigraphically, the Esna Fm. was subdivided into the Hanadi, Dababiya Quarry, and Mahmiya Members. Three calcareous nannofossil zones (NP7/8, NP9, and NP10) and four subzones (NP9a, NP9b, NP10a, and NP10b) were recognized. The biostratigraphic significances of calcareoust nannofossil bioevents associated with the P-E boundary at the study section were discussed. The base of the Eocene was placed at the base of the Dababiya Quarry Member in coincidence with the base of subzone NP9b, which is coincident with the LOs of Rhomboaster cuspis, R. calcitrapa, R. bitrifidia, Pontosphaera pulchra, and Zygrhablithus bijugatus. However, Discoaster araneus first occurred about 3 m below the base of subzone NP9b. The global decreases of the δ13C and δ18O values and carbonate contents across the P-E boundary were documented in the Gunnah section, which represents one of the most expanded and complete P-E sequences in Egypt.