Environmental footprints of the early Maastrichtian cooling – The record of benthic foraminifera from northern Germany

Abstract

The upper Campanian–lower Maastrichtian interval from the white chalk of the Kronsmoor section (northern Germany) has been a target of various studies on benthic foraminifera and benthic macroinvertebrates. The results of these studies are in part contradictory, as foraminifera suggest decreasing fertility throughout the early Maastrichtian, whereas macroinvertebrates imply increasing food supply.In order to elucidate this discrepancy, we re-studied benthic foraminiferal assemblages from Kronsmoor. This section provides a continuous upper Campanian–lower Maastrichtian succession with well-preserved foraminifera. Benthic assemblages are highly diverse and abundant. Common foraminifer species include Bolivina incrassata, Cibicidoides voltzianus, Gyroidinoides umbilicatus, Osangularia cordieriana, Sitella laevis and Stensioeina pommerana. Only a few variations in diversity or in morphogroup composition have been observed throughout the studied interval. Some individual taxa (e.g., B. incrassata, Cibicidoides spp.), show a trend of decreasing abundances, whereas others (Cibicides beaumontianus, G. umbilicatus) increase. The relatively stable composition of benthic morphogroups suggests that there were no severe palaeoenvironmental disruptions in the western Chalk Sea such as excess eutrophication or oxygen depletion. Modest palaeoecological shifts are indicated by the variation patterns of individual taxa such as G. umbilicus (increasing organic influx), C. beaumontianus (bottom water circulation) and Bolivinoides spp. (cooling).