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 Borelis 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.