Biostratigraphy and lithostratigraphy of Late Cretaceous–Early Palaeogene deposits in Tang-e-Abolhayat, Zagros basin (SW Iran)

Abstract

In this study, to consider microbiostratigraphy of Cretaceous and Palaeocene planktic foraminifera, a stratigraphic section of the Gurpi and Pabdeh formations named Tang-e-Abolhayat was selected. On the basis of the identified planktic foraminiferal assemblages, seven biozones and two sub-biozones have been recorded (four biozones from the uppermost part of the Cretaceous, (Gurpi Formation), and three biozones from the lower part of the Lower Palaeocene (Pabdeh Formation). The biostratigraphic correlations based on planktic foraminiferal zonations showed a comparison between the biostratigraphic zones in this study and other equivalents of the commonly used planktic zonal scheme around the Cretaceous–Palaeogene in and outside Iran. Biostratigraphic analysis confirms that the studied section is incomplete across the Cretaceous–Tertiary boundary and a hiatus is suggested by the absence of the Plummerita hantkeninoides, Guembelitria cretacea, Parvularugoglobigerina eugubina Zones and Parasubbotina pseudobulloides Subzone (CFl to Pla zones). These absences could reflect the restriction of the above-mentioned zones to shallower settings, slow sedimentation rates or an interval of erosion or no deposition. There is no obvious evidence of erosion. On the other hand, the Pabdeh Formation overlies Gurpi Formation paraconformably.