Benthic foraminiferal assemblages from Maastrichtian strata, Gansserina gansseri-Abathamphalus mayaroensis Planktonic Foraminiferal Zone, of the AbTalkh Formation at Aitamir section (west of the Kopeh-Dagh basin) were investigated in order to evaluate the palaeoenvironmental changes (organic matter flux and bottom-water oxygenation). Maastrichtian faunal assemblages are well preserved and diversified. Fluctuations in the percentage of infaunal and epifaunal morphogroups as well as simple diversity and heterogeneity index are recorded. The study indicates that an unstable environment with oligotrophic to weakly mesotrophic condition and high oxygenated bottom water condition was prevailed during the depositionof the sediments in the latest Cretaceous.

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