In order to evaluate Oceanic Anoxic Event 2 (OAE2) in Cenomanian-Turonian boundary and its effects on benthic foraminifera, a stratigraphic section (Taherabad) in the east of Kopet-Dagh basin was studied to document the pattern of changes in benthic foraminiferal communities. TOC concentration at the studied succession was increased near to 1% in the two intervals of R. cushmani and W. archaeocretacea biozones. The δ13C curve show the typical features of the globally documented Cenomanian–Turonian positive excursion, including three main build-ups. The positive shifts have resulted from burial of isotopically depleted organic carbon and occur just after high TOC intervals. Organic matter-rich intervals are characterized by lower δ18O values that indicate deposition under a warm condition with limited oxygen contents and enhanced primary productivity. These intervals are associated with a low abundance and low diversity of benthic assemblages that strongly dominated by shallow and deep infaunal agglutinated foraminifera. Characteristics taxa in this intervals are Lagenammina, Saccammina, Reophax and Tritaxia. A few opportunistic calcareous foraminifera include Gavelinella dakotensis and Lenticulina spp. are also present. By contrast, the assemblages found below and above warm intervals are more diverse and contain high abundance of calcareous benthic foraminifera. Common taxa in these parts are praebuliminids, lenticulinids, gavelinellids and Valvulineria parva. The significant abundance of praebuliminids and co-existence of infaunal and epifaunal morphogroups indicate a relatively high primary productivity (mesotrophic condition) during the improved ventilation of sea-floor.

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