Biostratigraphy and paleoenvironment of the larger benthic foraminifera in wells sections of the Asmari Formation from the Rag-e-Safid oil field, Zagros Basin, southwest Iran

Based on the stratigraphical distribution of the larger benthic foraminifera in the subsurface sedimentary successions of the Asmari Formation (Oligocene – Miocene) from the Rag-e-Safid oil field four assemblage zones have been recognized. Assemblage zone I suggests a Rupelian age and includes Nummulites fichteli, Nummulites vascus, Eulepidina, Nephrolepidina, Austrotrillina paucialveolata, Heterostegina assilinoides, Praerhapydionina delicate, Pseudolituonella reicheli; Assemblage zone II represents a Chattian age and is introduced by association of Archaias, Austrotrillina, Amphistegina, Miogypsinoides complanatus; Assemblage zone III suggests an Aquitanian age and consists of Miogypsinoides deharti, Miogypsina sp. and peneropelidae; Assemblage zone IV refers to Burdigalian age and is recognized by the first appearance of Boreli s melo and Borelis curdica. The paleoecology and biofacies of the larger benthic foraminifera suggest four depositional settings included open marine; ooids shoals; lagoon and tidal flat. These sedimentary settings correspond to the inner and middle parts of a carbonate ramp.