Oligocene age of the Gebel Qatrani Formation, Fayum, Egypt

Abstract

Sea level sequence stratigraphy is especially valuable for correlating marine stages on passively subsiding continental margins. The continental Gebel Qatrani Formation in Egypt is separated from the underlying marine Qasr el-Sagha Formation by a major unconformity with a minimum of 76 m of section missing due to erosion and/or non-deposition. This unconformity is constrained by Priabonian planktonic foraminifera in the Gehannam Formation to be younger than early late Eocene and it is constrained by radiometric ages and a great thickness of Gebel Qatrani Formation to be older than late Oligocene. The only "type-1" sequence boundary within these age constraints that involved a low enough sea stand to explain the unconformity was at the Priabonian-Rupelian (Eocene-Oligocene) boundary, which means that the Gebel Qatrani Formation is entirely Oligocene in age. This corroborates earlier age assignments based on invertebrate and vertebrate faunal succession and it is consistent with new paleomagnetic evidence. The Gebel Qatrani Formation has yielded the earliest primates of anthropoid grade and the evolutionary emergence of higher primates may be related to profound environmental change during the Eocene-Oligocene transition.