Abstract The late early Campanian to late late Campanian sediments deposited in the Kopet Dag basin in northeast Iran record paleoenvironmental events. They are represented by chalk limestones and grey to green shales. These sediments contained characteristic nannofossils, which appear to have been driven largely by variations in productivity possibly tied to changes in sources of surface waters. Because alcareous nannofossils are ideal proxies for deciphering productivity, in order to better understand the factors that controlled sedimentation, ten samples were analysed for calcareous nannofossils and Zn, Cu, Cd, Pb and CaCO3 composition from the boundary between Abderaz Formation and Abtalkh Formation in Hammam Qaleh section of the Kopet Dagh Basin (NE Iran). In the present study, the relationship between Zn, Cu, Cd, Pb and CaCO3, distribution of nannofossils and paleoproductivity changes are investigated in this region. Distinctive patterns in nannofossil assemblage’s abundances within the boundary are also recognized, reflecting changes from mesotrophic to more oligotrophic conditions which are probably controlled by climate. The Zn, Cu, Cd and Pb elements are directly related to productivity of nannofossils and from the Abderaz Formation to Abtalkh Formation show increase. These results correlate with changes of the abundance of the productivity index nannofossils (Watznaueria barnesae ). The nannofossil abundance and chemical analyses suggest the higher productivity level for the Abtalkh Formation relative to Abderaz Formation.

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