Larger Foraminifera from a Lower Lutetian Ramp In Central Iran: Taxonomy, Biostratigraphy, and Paleobiogeographic Implications

This study investigates an Eocene shallow-water carbonate succession measured at Chah-Talkh in Central Iran. It mainly focuses on larger benthic foraminifera (LBF) coupled with calcareous nannofossil biostratigraphy, including taxa recorded for the first time from the central-eastern Neo-Tethys. The age of the section spans the larger foraminiferal zones SBZ12 to SBZ13, dating the investigated succession as early Lutetian. The age is integrated through calcareous nannofossil biostratigraphy, where we have found markers of the NP14b–NP15b (CNE8–CNE10) zones. Data from Chah-Talkh section support a placement of the SBZ12/13 boundary within the base of the Lutetian. Assilina pomeroli, A. plana, A. placentula, and Nummulites campesinus and orthophragmines (population around the boundary of D. archiaci archiaci and D. a. bartholomei, D. fortisi cf. fortisi) appear in younger strata than previously reported. The sedimentary evolution, reconstructed from microfacies and LBF assemblages, reveals a deepening-upward trend on a low-angle homoclinal ramp, characterized by a cyclical alternation of inner ramp grainstones with middle ramp marls. LBF-based biostratigraphy, coupled with other age proxies such as nannofossils, is demonstrated to be reliable in refining the age model of the Cenozoic shallow marine successions in Central Iran. Moreover, our results provide insights on the application of shallow benthic zones across the Neo-Tethys region and suggest a possible eastward biogeographic dispersal of some nummulitid species.