Cenomanian—Turonian ostracods from Gebel Nezzazat, southwestern Sinai, Egypt, with observations on ∂13C values and the Cenomanian/Turonian boundary

Abstract. 96 surface samples from the Cenomanian—Turonian succession of Gebel Nezzazat, southwestern Sinai, Egypt were examined for ostracods. 45 species and varieties have been recognised with one new species ?Pterygocythere bisulcata sp.nov. and four left in open nomenclature. Most species have been recorded in rocks of the same age in the Middle East and North Africa, and some from West Africa, Europe and South America suggesting biogeographic relationships between these regions. Three local ostracod zonal assemblages are established, two in the Cenomanian and one in the Turonian. The ostracods and associated foraminifera and megafossils, suggest a shallow marine environment, sometimes with restricted marine water and in part brackish. The Oceanic Anoxic Event of the Late Cenomanian is recognised on the evidence of ∂13C values; ostracod diversity has a negative relationship to ∂13C values.