Comments on “Paleoecology and paleobiogeography of Paleocene ostracods in Dineigil area, south western Desert, Egypt.” by Youssef et al., Journal of African Earth Sciences, 131 (2017) 62–70

Abstract

In their recent paper, Youssef et al. (2017) published a quantitative study of Paleocene ostracod distributions in the Southwestern Desert of Egypt and recognized regional ecozones within a paleobiogeographic concept. To understand the significance of this ecozonation, a solid stratigraphic framework is required, though the authors only provided limited information. We demonstrate that fundamental aspects of their data representation and stratigraphic interpretation are incorrect, and thus not warrant utilization of the reported age of the ostracod record. For that reason, we stress that basic geological aspects of correlation between outcrops and creation of composite sections should be described in full detail upon publication. Based on our detailed reconstruction, the composite sequence at Bir Dungul spans calcareous nannoplankton Zones NP5-NP7/8, and mostly Thanetian in age, contrasting the observations of Youssef et al. (2017). The lowermost part of the sequence, suggested to comprise NP4 by Youssef et al. (2017) and thus Danian in age, cannot be dated because of lack of calcareous nannofossils and planktic foraminifera. Accordingly, there is no evidence in this sequence for the Latest Danian Event (as proposed by Youssef, 2014) either, and the potential relationship with the Mid Paleocene Biotic Event should be assessed critically. Consequently, accurate stratigraphic analysis, including biostratigraphy, remains essential to safeguard future paleobiogeographic interpretations along the edges of the Tethyan Ocean.