Calcareous nannofossil biostratigraphy of the Eocene succession in West Central Sinai, Egypt

Abstract

This work aims to put an end to the controversies about the occurrences of the upper Eocene in west-central Sinai by using the calcareous nannofossils. The Eocene calcareous nannofossil zones NP15 to NP18 were identified in Wadi Thal, west-central Sinai. Although the late Eocene Isthmolithus recurvus is recorded here for the first time, the base of NP19-20 zones is not delineated because the first occurrence of this taxon is considered a diachronous bioevent. The Zone NP18 is unconformably overlain by the lower marine Miocene NN2 Zone. Many calcareous nannofossil bioevents such as the last occurrence of Chiasmolithus grandis, the acme beginning of Cribrocentrum erbae, and the last occurrence of Neococcolithes dubius are used to approximate the Priabonian in west-central Sinai. It is recorded in the Tanka and Tayiba formations and probably in the uppermost part of the Thal Formation. Sea shallowness during the late Eocene due to uplifting in west-central Sinai might be responsible for the absence of many microfauna characterizing this stage/age. This suggestion is supported by the increased abundance of the nearshore nannofossil indicators, Lanternithus minutus, Zygrhablithus bijugatus and the shallow water Micrantholithus and Braarudosphaera from the upper part of Thal Formation through the overlain Tanka and Tayiba formations.