Foraminiferal biostratigraphy across the Eocene–Oligocene transition, in the Zagros Basin, Southern Iran

Abstract

The studied wells were located in the Bandar Abbas, Southeast Persian Gulf, and crosscut mainly from Eocene to Oligocene sequences spanning the Pabdeh, Jahrum, and Asmari formations respectively. The present work aims to characterize the biostratigraphy of the Eocene–Oligocene transition based on planktic and benthic foraminifera. Upper Eocene–Oligocene transition are subdivided into three lithostratigraphic units which are the Pabdeh Formation (Priabonian–Chattian), Jahrum Formation (Priabonian), and Asmari Formation (Rupelian-Chattian). Based on the stratigraphical range of the studied foraminifera, ten biozones have been established:- Morozovella velascoensis Zone (early Eocene) (I), Morozovella edgari Zone (Ypressian) (II(, Morozovella formosa formosa Zone (Ypressian) (III), Hantkenina alabamensis Highest-Occurrence Zone (Priabonian) (IV), Turborotalia cerroazulensis cunialensis Zone (Priabonian) (V), Cassigerinella chiploensis–Pseudohastigerina micra) Zone (Rupelian) (VI), Turborotalia ampliapertura Zone (Rupelian) (VII), Praegloborotalia opima opima Zone (Rupelian) (VIII), Nummulites spp., Discocyclina spp. Zone (Chattian) (IX) and Eulepidina–Nephrolepidina-Nummulites Zone (Chattian) (X). The recognized biozones were correlated with comparatively standards biozones for the Tethyan realm which demonstrates a good comparison between the biostratigraphic zones that recognized in this study with other biozones in different areas.