Quantitative Middle Eocene benthic foraminiferal biofacies from west-central Sinai, Egypt: Implications to paleobathymetry and sequence stratigraphy

Abstract

Abstract The basinal depositional architecture, paleobathymetry and paleoproductivity assessment of west central Sinai (Egypt) lacks robust sequence stratigraphic framework inferred in conjunction with changes in benthic foraminiferal biofacies. Sinai is an economically important region for hydrocarbon exploration, hence understanding its depositional architecture is fundamental. For this, the planktic foraminifera biostratigraphy is done first to date the strata exposed at Wadi Nukhul, and then, the quantitative benthic foraminiferal biofacies are evaluated to infer changes in paleobathymetry and paleoproductivity. Five Eocene planktic biozones identified (E7b to E11), spanning 48.6 to 40.4 Ma are identified along with five 3rd order depositional sequences bounded by four sequence boundaries. Quantitative (Rotated factor analysis) benthic foraminiferal analysis revealed seven benthic foraminifera biofacies (A to F) suggesting a meso- to eutrophic, outer neritic, moderate to low oxygenated bottom waters, dominated largely by benthic foraminifera taxa, Bulimina, Uvigerina, Bolivina and Lenticulina. Exception to this trend is the presence of biofacies B (Discorbis ciperensis-Lenticulina cuvillieri) at the top of the Thebes Formation that reflects well‑oxygenated bottom waters straddling the middle to outer neritic depth boundary. The inferred relative sea level gradually decreases throughout the studied section (from bottom to top) and is consistent with a gradual global decline. Of interest is the possible identification of the Middle Eocene Climatic Optimum (~40.5–40 Ma), a global warming event that in the present study, encompasses the Uvigerina mediterranea-Spiroloculina esnaensis biofacies (Biofacies A) suggesting the presence of mesotrophic but moderately well‑oxygenated bottom waters at outer neritic depths. The base of the Thebes Formation is marked by the presence of an Oxygen Minimum Zone.