Revision in the paleontology and distribution of the larger benthic foraminifera in the Oligocene-Miocene deposits of the Zagros Basin, southwest Iran

The present research is a revision in the distribution and description of the larger benthic foraminifera from the Oligocene-Miocene Asmari Formation in the Zagros Basin in southwest Iran. From the shallow marine carbonates of the Asmari Formation, 21 genera and 41 species of larger benthic foraminifera have been identified of which 22 species have been described in recent research. The described genera belong to 11 families. The recognised foraminifera includes Nummulites, Operculina, Heterostegina, Spiroclypeus, Nephrolepidina, Eulepidina, Neorotalia, Amphistegina, Victoriella, Carpenteria, Planorbulinella, Miniacina, Planorbulinoides, Austrotrillina, Archaias, Praearchaias, Praerhapydionina, Peneroplis, Spirolina, Miogypsinoides, Meandropsin and Borelis. On the basis of the distribution of the larger benthic foraminifera, five assemblage biozones have been recorded in the Asmari Formation in the study area. The foraminifers' assemblages indicate to Oligocene (Rupelian and Chattian stages) and lower Miocene (Aquitanian and Burdigalian stages) times. There is a similarity of the Mediterranean and Indo-West Pacific fauna with the Asmari Formation fauna in the Rupelian-Chattian times. On the basis of the dissimilarity distribution of larger benthic foraminifera, there was no connection seaway between the shallow marine limestone of the Asmari Formation and Indo-West Pacific region in the Aquitanian and Burdigalian times.