The changes in planktonic foraminifera assemblages were studied in two sections composed of clayey limestone, limestone, claystone and marl in the Akveren Formation in the Bartın Province. Pseudoguembelina palpebra, Racemiguembelina fructicosa, Abathomphalus mayaroensis and Pseudoguembelina hariaensis biozones in the Maastrichtian and Parvularugoglobigerina eugubina, Glomobanomalina compressa/Praemurica uncinata, Praemurica uncinata and Morozovella angulata biozones in the Paloecene were

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... ned using planktonic genus and species identified in these sections. Paleoecological interpretations in this study were completed by using the relative abundances of paleoecological species identified in these biozones. The abundance of Rugoglobigerina spp., Heterohelix globulosa, Pseudoguembelina spp., species that tolerated changes in sea water temperature and nutrition, increased in the Maastrichtian. In the uppermost Maastrichtian, high abundance of Racemiguembelina fructicosa, Heterohelix globulosa and Rugoglobigerina spp. show oligotrophic and warmer environmental conditions in this study. The abundance of globotruncanids are unstable due to environmental changes. The new species have smaller sizes and globular chambers emerged in the Paleocene. High abundance of Subbotina triloculinoides and Parasubbotina pseudobulloides show mesotrophic and cooler environmental conditions in the Danian. Morozovellid taxa started to dominate in the Selandian and environmental conditions changed from mesotrophic to oligotrophic.