New biostratigraphic observations of planktonic foraminifera and ammonites on the Aptian–Albian intrashelf succession, Zagros Basin, SW Iran

Abstract

A detailed planktonic foraminiferal biostratigraphic framework, associated with supporting ammonite data, is presented for Aptian–Albian intrashelf sedimentary succession (Kazhdumi Formation) at the Tang-e-Maghar section, Zagros Basin, SW Iran. Most of the identified planktonic foraminiferal species are reported for the first time from this region, and the fauna permits five biozones to be newly proposed from the upper Aptian Globigerinelloides aptiensis Zone to the middle Albian Ticinella primula Zone. Notably, we recognize a narrow interval of faunal turnover in the Microhedbergella miniglobularis Zone, the base of which is delimited by the highest occurrences of Aptian-representing taxa and the top by the lowest occurrence of the Albian Microhedbergella praeplanispira. The proposed Aptian/Albian boundary should lie within this interval accordingly. In addition, we report on 12 ammonite levels that can be used to constrain the Aptian–Albian Substages. The proposed planktonic foraminiferal biozonation of the studied section will be an important step toward better understanding of the nature of the biotic and global changes across the Aptian/Albian boundary on the Arabian Plate in the paleotropical southern Neo-Tethys.