Biostratigraphy and Paleoenvironmental significance of Paleogene foraminiferal assemblages from Dashte Zari area in High Zagros, west Iran

International audienceThe Paleogene carbonate deposits of Pabdeh and Jahrum formations are widespread in the northwest of the Shahrekord region (Dashte Zari area) in the High Zagros Mountains of Iran and record lateral and upward transition from open marine into shallow water environment within the Zagros foreland basin. The Pabdeh Formation shows a succession of open marine pelagic and hemipelagic limestone, argillaceous limestone, and argillaceous chert. It consists of planktonic wackestone, pellet-planktonic wackestone, mudstone with planktonic foraminifera, and radiolarian siliceous wackestone. The planktonic foraminifera are assigned to the Late Paleocene to Late Eocene, and correspond to subtropical to tropical Zones P4b-E15. Only one planktonic biozone (Zone E12), which corresponds to the high level stand of the Bartonian climate optimum (MECO) was not recognized in likely response to a tectonic event.The Jahrum Formation is represented by bioclast-bearing limestone and calcarenite. It consists of benthic foraminiferal wackestone, benthic foraminiferal-red algal packstone, and bioclast-intraclast packstone deposited in a shallow platform environment. The Jahrum Formation is inter-fingered in the upper part of the Pabdeh Formation and finally overlies it conformably during the Bartonian-Priabonian. Shallowing and offlap relationships record basin shrinking, while repeated interfingering signals moderate tectonic subsidence. Both formations are disconformably covered by the Late Oligocene-Miocene Asmari Formation