Revision of the age of the Qom Formation in the Central Iran Basin, Iran

The Qom Formation in the Central Iran Basin contains not only relatively abundant calcareous nannofossils and a small number of dinoflagellate cysts, but also a number of stratigraphically significant benthonic foraminifers and ostracods. Calcareous nannofossils reported for the first time from this formation include Coccolithus pelagicus, Cyclicargolithus abisectus, C. floridanus, Dictyococcites bisectus, D. scrippsae, Helicosphaera euphratis, Ericsonia fenestratus, Pontosphaera sp., Reticulofenestra dictyoda, R. minuta and Sphenolithus moriformis. Dinoflagellates include Homotryblium plectilum, Hystrichokolpoma rigaudiae, Operculodinium centrocarpum, Palaeocystodinium golzowense, Spiniferites pseudofurcatus and Thalassiphora pelagica. Benthonic foraminifers include Assilina aff. spira, Discocyclina sp., Neodiscocyclina cf. barkeri, Nummulites aff. variolarius, Operculina sp. and Orbitolites sp. Among the ostracods recovered are Alocopocythere dhansariensis, Asymmetricythere samalutensis, Bairdia montiformis, Cytherella jonesiana, Cytheretta virgulata, Cytheridea cf. bundensis, C. cf. scruposa, C. sp., Eopaijenborchella sp., Hermanites cf. grafica, Krithe oryza, K. cf. pernoides, Loxoconcha sp., Paracypris sp., Propontocypris zongbuensis, P. sp. and Xestoleberis sp. This assemblage indicates that the Qom Formation is Eocene in age instead of Middle-Late Oligocene to Early Miocene as previously determined.