Calcareous nannofossil bioevents at the Paleocene/Eocene boundary in Kharga Oasis, Western Desert of Egypt

Abstract

Two upper Palaeocene – lower Eocene stratigraphic sequences at the Kharga Oasis (Umm El Ghanayim and Naqb Assiut sections) were studied biostratigraphically on the basis of their calcareous nannofossil content. The investigated interval includes the upper part of the Tarawan Formation, the Tarawan Chalk, and the Esna formations. A total number of sixty-seven different taxa have been identified. The lowest occurrence (LO) of Discoaster araneus was used to place the base of the NP9b Subzone (base of Eocene) at the Gabal Umm El Ghanayim section. The lowest occurrences (LOs) of Rhomboaster bitrifida, Discoaster araneus and D. anartios are used to define the NP9a/NP9b subzonal boundary at the Gabal Naqb Assiut section. In this section,the P/E boundary is marked by a minor lithologic hiatus as indicated by the absence of the basal part of the Dababiya Member.At the studied two sections, a major turnover in calcareous nannofossil assemblages across the P/E transition was documented. The abundance of warm water Ericsonia subpertusa, Fasculithusspp., Coccolithus eopelagicus, Discoaster spp., Rhomboaster bitrifida and Tribrachiatus bramlettei characterize the Palaeocene-Eocene transition and suggest global warming and the Palaeocene – Eocene Thermal Maximum (PETM).

Keywords

• Calcareous nannofossils, Palaeocene/ Eocene boundary, Kharga Oasis, Western Desert, Egypt