Foraminiferal biostratigraphy and bioevents of the Cenomanian-Turonian succession in southern Sinai, Egypt and relationship to OAE2

Abstract

Abstract: The shallow water Cenomanian–Turonian succession exposed in the southern Sinai was examined to distinguish the biostratigraphic zonations , based on the foraminiferal associations, and to define the significant bioevents that occurred during this interval. This succession is subdivided into two rock units, namely the Raha and Abu Qada formations. According to the lithological characteristics, the Raha Formation is subdivided into the Abu Had and Mellaha Sand members. The foraminiferal association consists of 33 species (23 benthic and 10 planktic). Planktic foraminifera are distributed only in sporadic intervals. Relying on the combination of benthic and planktic foraminifera, four local biozones are established including, Daxia cenomana–Mayncina d'orbignyi, Biplanata peneropliformis-Nezzazata convexa, Thomasinella punica, and Whiteinella archaeocretacea . In this study, the Cenomanian/Turonian boundary is characterized by a sequence of significant bioevents beginning with the extinction of some benthic foraminifera (e.g., Thomasinella spp.), followed by a bloom of the low-oxygen tolerant planktic foraminifera (heterohelicids), a flood of calcispheres and microfilaments, and then the dominance of whiteinellids. These bioevents could be recognized as a key for a global turnover that occurred across the Cenomanian –Turonian boundary associated with Oceanic Anoxic Event 2.