Planktic foraminif era in the Cretaceous/Tertiary boundary clays of the Geulhemmerberg (Netherlands)

Abstract

In the Geulhemmerberg section across the Cretaceous/Tertiary (K/T) boundary, planktic foraminiferal assemblages were found only in the basal Paleocene clay layers. These layers are interpreted to correspond to the planktic foraminiferal P0 Zone because Paleocene planktic foraminifers do not occur yet, whilst Paleocene nannofossil and dinoflagellate assemblages are already present. This is consistent with the K/T boundary clays (P0 Zone) of El Kef in Tunisia and of Agost and Caravaca in Spain, in which Paleocene species are also absent. The planktic assemblages of the clay layers have a low diversity, comparable to P0 planktic assemblages from the Nye Kløv section in Denmark. Heterohelix globulosa (Ehrenberg) dominates the assemblages. Excellent preservation of the planktic foraminifers, and anomalously high planktic foraminifer percentages (P/(P+B) = 53.3%) provide compelling arguments for survivorship of at least five generalist Cretaceous taxa into the basal Paleocene P0 Zone, as shown earlier at Caravaca, El Kef and Nye Kløv. However, due to the lack of planktic faunas in under- and overlying sediments, it is impossible to infer whether the planktic foraminiferal faunas in the P0 Zone clay-Iayers have changed, or are impoverished compared to Upper Maastrichtian faunas