Oxygen and carbon isotope records of Upper Cretaceous foraminifera from Poland: vital and microhabitat effects

The observed differences between δ13C values of infaunal and epifaunal foraminiferal taxa are related to the presence of δ13CDIC (DIC - dissolved inorganic carbon) gradient in the sediment column, which was much higher in the Chełm section. Although planktic foraminifera studied are characterized by different lifestyles, this feature is not mirrored in their oxygen and carbon isotope compositions. This is probably due to effects of vital isotope fractionation and minor thermal and carbon isotope gradients in a part of the water column inhabited by these organisms. The thermal gradient between near surface and bottom waters is calculated to be ca. 4.0 °C, and ca. 7.5 °C for the Early Campanian and the Late Maastrichtian seas of East European Platform, respectively, based on the comparison of δ18O values of selected planktic and benthic foraminifera.