Nummulitids from Lower Eocene section at Darb Gaga, Baris Oasis, Western Desert, Egypt: New calibration of Eocene larger foraminiferal biostratigraphic zonation

Four large foraminiferal species have been newly recorded from the Darb Gaga area. The Darb Gaga area is represented by the Upper Paleocene-Lower Eocene succession, which is composed of the Esna Formation (Fm.) at the base followed upward by the lowermost part of the Thebes Fm. The present work concentrates on Abu Had Member (Mb.), the upper part of the Esna Fm., and the Thebes Fm. A new genus (Solimanina) is introduced for the first time in Egypt. Two species (Solimanina canaliferus and Solimanina conf. subgranulosa) belong to this genus. These species are recorded from the Abu Had Mb. Moreover, Nummulites pernotus and Nummulites partschi have been documented from the Thebes Fm. Morphometric, biometric, taxonomic and systematic study of the large benthonic foraminifera (LBF) in integration with field, litho- and bio-stratigraphical studies of the study area have been done. The recorded LBF species assigned the Abu Had Mb. and the lowermost part of the Thebes to be Early Eocene in age (Ypresian), within SBZ10 (the beginning of Late Ypresian). The shift from the outer shelf environment prevailed during the deposition of the Darb Gaga Mb. to the inner shelf environment of the Abu Had Mb. and the lowermost part of the Thebes Fm. may be due to sea-level changes and/or tectonism that occurred in Early Eocene (Ypresian) age.