Ostracode and microfacies study of the Eocene sequence in the northwestern part of the Eastern Desert, Egypt

Abstract

The Eocene exposures in the area between Rod El-Hammara and Wadi El Sheikh, northwestern part of the Eastern Desert, are divisible from base to top into the Observatory, Qurn, Wadi Garawi and Wadi Hof Formations. The sequence ranges in age from Lutetian to Priabonian and is correlatable with the rock units carrying the same names in the Greater Cairo area. from these formations twenty five ostracode species have been identified, among them Bradleya? boukharyi is believed to be new. It was possible to recognize the following ostracode zones: Ruggeria (K.) glabella Assemblage Zone, Costa humboldtin Assemblage Zone (Biarritzian) and Urommullerina said Assemblage Zone (Priabonian). The studied Eocene carbonate rocks belong to the following microfacies types: grainstone-packstone, wackestone with whole shells, bioclastic wackestone, coquina packstone and grainstone with pellets. The sedimentary environment of the Observatory Formation ranges from foreslope to shelf lagoon, the Qurn and Wadi Garawi Formations from shelf lagoon to restricted platform while the Wadi Hof Formation is of a winnowed platform edge sands environment with very often high terrigenous influx. The whole Eocene sequence in the studyb area reflects remarkable shallower conditions both temporally and eastward.