Dinoflagellate cyst evidence for the age and palaeoenvironments of the Upper Eocene–Oligocene Dabaa Formation, Qattara Depression, north Western Desert, Egypt

Abstract

ABSTRACTThe palynological investigation of 30 outcrop samples from seven sites in and near the Qattara Depression, north Western Desert, Egypt, has yielded six samples from three sites containing poorly to well-preserved assemblages including dinoflagellate cysts, freshwater algae, acritarchs, pollen and spores. The sites have not been dated previously, but dinoflagellate cyst evidence reveals an early or middle Rupelian (Early Oligocene) age for one sample (overlapping ranges of Tuberculodinium vancampoae and Phthanoperidinium comatum) and early Rupelian or older (occurrence of Lentinia serrata) for another, establishing time equivalence with the Upper Eocene–Oligocene Dabaa Formation. The palynological assemblages reflect fluctuating conditions on the southern margin of the Tethys/Paratethys Ocean, with the frequent co-occurrence of Homotryblium floripes, Pediastrum and Botryococcus reflecting restricted and probably lagoonal marine environments influenced by seasonal river inflow. Despite low global sea levels during the Early Oligocene, marine conditions evidently extended as far south as the southern Qattara Depression. Outcrops in the north Western Desert are typically deeply weathered and barren of palynomorphs, this being the first report of dinoflagellate cysts from surface sections of the Qattara Depression and its surroundings.