Calcareous nannofossils of the Paleocene–Eocene transition in four sections from Egypt

Abstract

A detailed analysis of calcareous nannofossil assemblages was carried out across the Paleocene-Eocene transition in four outcrops in Egypt (the Gebel Matulla, Markha, El-Quss Abu Said, and Gebel Duwi sections) that span the Discoaster multiradiatus (NP9) to Discoaster binodosus (NP11) zones. The Paleocene-Eocene (P/E) boundary is placed in the lower part of the Esna Shale Formation based on the LOs of the Calcareous Nannofossil Excursion Taxa (CNET or RD) that define the base of NP9b. The studied sections are considered complete and document the Paleocene-Eocene Thermal Maximum (PETM). The occurrences of long-armed and asymmetrical discoasters (e.g., D. araneus, D. anartios) and rhomboasters (e.g., R. intermedia, R. bitrifidia, and R. spineus) are characteristic of the PETM interval. A sharp decrease in the diversification of Fasciculithus is noted at the onset of PETM. The abundance of Zygrhablithus bijugatus increases and corresponds with the dramatic decline in the oligotrophic Fasciculithus above the Paleocene/Eocene boundary and appears to be a significant global event. The Discoaster, Fasciculithus, and Rhomboaster species reflect relatively warm and, probably, oligotrophic surface waters. A minor hiatus in most of the studied sections near the upper part of Zone NP10 has been recorded in many parts of the world and reflects a global sea level drop.