Re-evaluation and correlation of the Oligocene foraminiferal biozones in the eastern Zagros Basin, SW Iran

Abstract

ABSTRACT This study reconsiders the previous biostratigraphic settings for the Asmari Formation in the eastern Zagros Basin (Fars Basin). The results imply that the Rupelian is identified by the total range zone of the Nummulites species (N. vascus, N. fichteli, N. intermedius). The occurrence of Archaias kirkukensis, A. hensoni, and A. asmaricus before the disappearance of Nummulites species in the current study and even the co-occurrence of the A. hensoni with the mentioned species prevents the use of recently proposed regional stratigraphical framework. The lower part of the Asmari Formation remains without certain age until the occurrence of larger benthic foraminifera throughout the Asmari platform. The coeval biozones for the Chattian Stage are Biozone 59, Biozone 2(b), Archaias asmaricus-A. hensoni-Miogypsinoides complanatus Assemblage Zone, and a part of Assemblage Zone 7 as named by the previous studies. In this study species like Archaias, Austrotrillina, Borelis and Peneroplis are not useful for discriminating the Rupelian and Chattian stages.