Postmiogypsinella intermedia Sirel and Gedik 2011 from the upper Oligocene of Central Iran (Qom Formation): Paleogeography and paleoenvironmental implications

Abstract

Postmiogypsinella intermedia Sirel and Gedik, 2011 is reported for the first time from the shallow-marine limestones of the upper Chattian Qom Formation, Central Iran. This miogypsinid species has so far only been recorded from the upper Oligocene of Malatya (type locality) and Sivas (Central Anatolia) in eastern Turkey and from the upper Oligocene of the Prebetic Domain, SE Spain. The new record from Central Iran, paleobiogeographically located at the Eurasian margin of the Tethyan Seaway between the Western and Eastern Tethys realms, indicates that the paleogeographic distribution of this species has to be extended eastwards as far as Central Iran. This observation is not unexpected, since miogypsinid foraminifers with eccentric embryonic–nepionic apparatus (e.g., Miogypsinella, Miogypsinoides, Miogypsina) are usually widely distributed. The accompanying larger benthic foraminifera, including Miogypsinoides complanatus (Schlumberger), Miogypsinoides formosensis Yabe and Hanzawa, Spiroclypeus margaritatus (Schlumberger), Operculina complanata (Defrance), and Risananeiza pustulosa Boukhary et al., indicate the late Chattian age (corresponding to SBZ 23 Biozone). Postmiogypsinella intermedia is indicative of a shallow-marine middle ramp environment with oligotrophic conditions and inhabited the relatively deeper part of the photic zone.