The Paleocene climate in west central Sinai (Egypt): insights from the calcareous nannofossils.

To reconstruct the paleoclimate in North Africa during the Paleocene, the calcareous nannofossils were quantitatively analyzed at higher resolution from the stratigraphic succession of Gebel Nezzazat (west central Sinai, Egypt). The studied interval extends from NP4 to NP8. Zone NP4 can be subdivided into four subzones from base to top: NTp7B, NTp8A, NTp8B, and NTp8C. The base of the Selandian age is located at the base of NTp8B (Second Radiation of Fasciculithus). The Selandian/Thanetian boundary (S/T) is tentatively placed at the base of Zone NP7/8. The identified nannofossil zones were compared with that of the Tethyan region for the Danian/Selandian boundary. The calcareous nannofossil assemblages were used as indicators for medium-term climatic fluctuations. The pre-Danian (LDE) is dominated by the cool-water Zeugrhabdotus sigmoides and Neochiastozygus modestus, while the post-Danian interval is dominated by Coccolithus pelagicus and Ericsonia subpertusa. Before the onset of the Selandian-Thanetian boundary, a marked shift in the nannofossil species was observed, where Fasciculithus increased significantly, while marker Danian-Selandian genera (e.g., Lithoptychius Neochiastozygus, Chiasmolithus, and Cruciplacolithus) decreased dramatically. Non-Metric Multidimensional Scaling (nMDS) and permutational analysis of variance (PERMANOVA) in addition to the Temperature and Nutrient indices (TI and NI) indicated a marked difference between the warm eutrophic nannofossil assemblages at the Danian/Selandian (D/S) and the Selandian/Thanetian (S/T) transitions and the eutrophic cold-water assemblages during the background sedimentation. A sharp increase in sea surface temperature and decrease in nutrients was observed at D/S and represents the Latest Danian Event (LDE), while the second warming event was started prior to the Selandian and may represent the Early Late Paleocene Event "ELPE." The sea-level lowstand may have limited water circulation, where surface water fertility decreased significantly. Consequently, nannofossil diversity decreased. The rapid recovery after the LDE was attributed to the radiation of warm-water taxa. [ABSTRACT FROM AUTHOR]