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, Fasculithus spp., 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). 2.2. Esna Formation The term Esna Shale was first introduced by BEADNELL (1905), to describe the shale succession that overlies the Tarawan Forma tion and underlies the Thebes Formation at Gabal Oweina, Esna Idfu area, Upper Nile Valley. ABDELRAZIK (1972) separated this formation into two members, the El Hanadi Member at the base and the El Shaghab Member at the top. DUPUIS et al. (2003) classified the Esna Formation from the base to the top, into three units (Esna Unit 1, Esna Unit 2 and Esna Unit 3) (Table 1).

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

“…In the Gebel Matulla section D. binodosus first appears in the lowermost part of NP10a. This taxon first occurs at the base of Zone NP10 in some other sections in Egypt as noted by Faris (1993) at the Gurnah section, Nile Valley; Taramsa, west of Qena; El Serai, east of Qena; and at Gebel Duwi, Quseir area. This author used the LO of this species to delineate the NP9/ NP10 zonal boundary at Gebel El Ain and Gebel El Falig in northeast Sinai.…”

Upper Paleocene-lower Eocene calcareous nannofossil stratigraphy at the Misheiti Section, Central Sinai, Egypt

“…In Egypt, it was traditionally placed at the base of Zone NP10 or within Zone NP10 (Bolle et al, 2000). The LOs of Discoaster diastypus, T. bramlettei, and D. binodosus were used by Faris (1993) to trace the base of the Eocene. Later, the base of the Eocene was placed at the GSSP in coincidence with the base of calcareous nannofossil Subzone NP9b (Dupuis et al, 2003).…”