Paleoecology of calcareous nannofossils from Paleogene formations of the Magura Unit in the Western Carpathians

摘要

The main objective of this paper is to reveal how the calcareous nannofossils react to environmental changes at changed paleoecological conditions, which occurred during the Eocene/OIigocene transitional period. The calcareous nannofossils were identified and statistically evaluated in the time span from the Late Eocene to Early Oligocene. The research results have demonstrated that the species Coccolithus pelagicus (Wallich) Schiller, Coccolithus eopelagicus (Bramlette et Riedel) Bramlette et Sullivan, Reticulofenestra umbilica (Levin) Martini et Ritzkowski and Dictyococcites bisectus (Hay, Mohler et Wade) Bukry et Percival enlarged their body dimensions as a response to changed paleoecological conditions. The reason for this effect was not just the cooling trend during the Late Eocene to Early Oligocene, but also eutrophication of the environment, supply of continental material, volcanic activity, as well as the presence of half-separated basin. Based on evaluated biostratigraphic data, the relationships between the cold-water and warm-water species, as well as species present in the moderate tempered water, were statistically processed.