Benthic foraminiferal assemblages from eight clay-layers within a relatively thick section of the lowermost Paleocene (planktonic foraminifera P0 Zone) at the Geulhemmerberg, SE Netherlands, were examined for changes in abundance and species composition.

Abstract

Benthic foraminiferal assemblages from eight clay-layers within a relatively thick section of the lowermost Paleocene (planktonic foraminifera P0 Zone) at the Geulhemmerberg, SE Netherlands, were examined for changes in abundance and species composition. The lower clay layers (A to D) are characterized by peculiar benthic foraminiferal assemblages with high numbers of small spiral forms which resemble modern epifaunal phytodetritus-feeding communities, that are well adapted to a food-limited environment in which much of the nutrient input is seasonally or erratically pulsed. Another distinct assemblage with high numbers of small, infaunal morphotypes such as Tappanina selmensis, Reussella ex gr. europaea, buliminids and bolivinids characterizes the upper part of the succession (clay layers E and F). This assemblage exhibits striking similarities to modern assemblages in areas with enhanced organic-matter export flux rates resulting in increased food supply for benthic organisms and slightly dysaerobic conditions at the sea floor. The occurrence of these 'high-productivity' benthic foraminiferal assemblages coincides with a marked increase in Thoracosphaera çalcarcous dinoflagellate cysts and may indicate an important phase in the recovery of the marine ecosystem after the collapse of the food web at the Cretaceous/Tertiary boundary.