Abstract
Calcareous nannofossil and planktonic foraminiferal biostratigraphy and bioevents in the Zewe section situated in the Kurdistan Region, NE Iraq, have been described in detail. High-resolution standardization of Coniacian/Santonian calcareous nannofossil and planktonic foraminiferal biostratigraphic datums categorized the reviewed succession into two nannofossil (CC15 and CC16) zones which are utterly equivalent to two planktonic foraminiferal (Dicarinella concavataandD. asymetrica) zones. The Coniacian/Santonian stage boundary was fixed based on the FOs of the premium reliable calcareous nannofossil and planktonic foraminiferal assemblages. The successive bioevents, in stratigraphic order, characterizing the Coniacian/Santonian stage boundary in the conspicuous inspected section are as follows: the FOs ofLithastrinus grillii(Upper Coniacian);Lucianorhabdus cayeuxii(Uppermost Coniacian); andMicula concava(Lowermost Santonian). Other nannofossil assemblages in Zone CC16 are the FOs ofRadiolithus planus,Quadrum giganteum, andEprolithus floralis. The planktonic foraminiferal bioevents are as follows: the FO ofDicarinella asymetrica(Upper Coniacian), followed upward by the FO of very rareSigali carpatica(Uppermost Coniacian) and commonGlobotruncana linneianaat the base of the Santonian stage.