Biostratigraphy, microfacies analysis and depositional environment of the Bartonian–Priabonian limestones in Shan-Abad anticline (west of Rafsanjan)

The Middle–Late Eocene carbonate deposits have developed in the Shan-Abad anticline as a thin belt among volcanic rocks. The nummulite banks are one of the most interesting deposits in this belt and composed of nummulite accumulations in the form of small, low-relief build-ups. Investigating three outcrops of these deposits were carried out at the eastern flank of Shan-Abad anticline in the present study. A high diversity of larger benthic foraminifera (LBF) and a small number of planktonic foraminifera are recognized, and the sedimentary environment is reconstructed.Based on LBF, three Tethyan foraminiferal biozones (SBZ 17–SBZ 19) spanning the Middle to Late Eocene interval are identified. The textural analysis and faunal assemblages reveal eleven microfacies types. These microfacies types (MFT) are deposited on a carbonate ramp model from tidal to open marine settings. Analysis of the Bartonian–Priabonian deposits based on facies distribution and paleoecology of the biotic components suggest deposition in the inner, middle and proximal outer ramp settings. The inner ramp includes proximal and distal parts. The proximal part of inner ramp is characterized by tidal flat, lagoon, and shoal belts. The distal part of inner ramp includes the nummulite banks. The open marine microfacies were deposited in mid to proximal outer ramp settings.