Eocene larger benthic foraminifera (alveolinids, nummulitids, and orthophragmines) from the eastern Alborz region (NE Iran): Taxonomy and biostratigraphy implications

Abstract

Shallow marine Eocene successions are described and illustrated with major focus on the systematics and biostratigraphic interpretation of larger benthic foraminifera in two stratigraphic sections (Mojen & Kalateh) of the Ziarat Formation from the eastern Alborz zone (Iran). Based on the larger benthic foraminifera assemblages, six shallow benthic zones (SBZ8-SBZ10 and SBZ16?-SBZ17-SBZ18b) during the middle Ilerdian-early Cuisian and Late Lutetian?-Bartonian interval are identified for the first time. The Mojen section is mainly composed of Alveolina horizons as index markers, such as Alveolinadecipiens (Schwager), A. tumida (Hottinger), A. ilerdensis (Hottinger), A. sp. cf. A. ilerdensis, A. laxa (Hottinger), A. citrea (Drobne), A. trempina (Hottinger), A. fornasinii (Checchia-Rispoli), A. canavarii (Checchia-Rispoli), A. cf. canavarii and A. aff. cayrazensis, which are consistent with the SBZ8 to SBZ10 interval, whilst the exact age of the top of the interval was not distinctly recognizable. The studied interval of the Kalateh section was assigned to the SBZ16?-SBZ17-SBZ18b with identifications of larger hyaline-lamellar foraminifera represented by Nummulites cf. deshayesi, N. lyelli (D’Archiac & Haime), Orbitoclypeus zitteli (Checchia-Rispoli) and Asterocyclina stellastella (Gümbel).