Biostratigraphy and Systematic Paleontology of the Oligocene Larger Benthic Foraminifera from Fars Province, Zaros Basin, SW Iran

Abstract

In this study, biostratigraphy and systematic description of the larger benthic foraminifera are investigated in Oligocene Asmari Formation cropping out over an area around Fars Province, Zagros Basin, southwest Iran. Shallow marine sediments of the Asmari Formation yielded numerous taxa of larger benthic foraminifera. Three assemblage zones were recognised according to taxa distribution. These indicate the Rupelian to Chattian age and include: Nummulites vascus–Nummulites fichteli, Lepidocyclina–Operculina–Ditrupa, Archaias asmaricus/hensoni–Miogypsinoides complanatus. Nummulites vascus–Nummulites fichteli is the common biozone in Fars Province in the Rupelian Stage. In the Chattian Stage, Archaias asmaricus/hensoni–Miogypsinoides complanatus assemblage zone is recognisable throughout Zagros Basin. Systematic description is presented here for the main biozone separator taxa in the Oligocene of the Indo-Pacific and Tethyan basins, as Nummulites, Operculina, Eulepidina, Nephrolepidina, Archaias and Peneroplis. Some other associated taxa such as Heterostegina, Amphistegina, Neorotalia, Peneroplis, Praearchaias and Sivasina are also described. Broad regional comparisons of the Oligocene of the Zagros fauna, Western Tethyan and Indo-west Pacific confirm the marine connection across the Middle East, in the Rupelian time. This connection is commenced to be narrowed, as is evidenced by the faunal changes and Nummulites spp. extinction during the Chattian Stage.