Phytoplankton response to palaeoenvironmental changes across the Campanian–Maastrichtian (Upper Cretaceous) boundary interval of the Middle Vistula River section, central Poland

Abstract

Palynological and palynofacies analyses were applied in order to characterise the palaeoenvironmental conditions that existed during the formation of the upper Campanian–lowermost Maastrichtian epicontinental succession of the Middle Vistula River section (central Poland). The abundant and diverse phytoplankton assemblages, dominated by dinoflagellate cysts (dinocysts) indicative of inner- to outer-neritic settings, varied distinctly throughout the succession. A high-resolution analysis of dinocyst palaeoecological groups revealed a distinct trend, interpreted in terms of the dinoflagellate response to relative sea-level fluctuations. A comparison with the short-term global sea-level curve suggests that the recorded sea-level changes were of eustatic origin. The palaeoenvironmental preferences of Circulodinium distinctum, Spongodinium delitiense, Callaiosphaeridium spp. and some ceratiacean dinocysts (Odontochitina and Xenascus) are discussed. The importance of Tanyosphaeridium xanthiopyxides and of the Cretaceous species of the acritarch genus Palaeostomocystis (P. foveolata, P. reticulata) as potential proxies for cooler-water conditions is highlighted. Circulodinium distinctum and Odontochitina dilatata likely preferred warmer waters. The trend in the palynofacies pattern (short-term cyclicity manifested as significant influxes of translucent phytoclasts) was found not to correspond to the dinocyst-inferred sea-level changes. Instead, variation in the terrestrially-sourced (probably from nearby Kukernitz Island) organic-matter supply was possibly caused by changes in river runoff.