Planktonic foraminiferal stability in the Upper Maastrichtian and the catastrophic mass extinction at the Cretaceous-Tertiary (K/T) boundary at Caravaca (Spain).

Abstract

The planktic foraminiferal quantitative and biostratigraphic study across the K/T boundary at the Caravaca section provides proof of the stratigraphical range continuity and the evolutive stability of species in the Upper Maastrichtian. In Caravaca, the planktic foraminiferal extinction pattern is a catastrophic mass extinction since 74% of the species went extinct in coincidence with the K/T boundary and with the evidence of impact. This pattern can be similarly identified in other Tethyan sections and, for this reason, the authors consider that the supposed extinctions suggested by other authors in Caravaca could be caused by the Signor-Lipps effect. In this study, it was found that possibly 17 Cretaceous species survived the K/T event and their relative abundance suddenly drops above the K/ T boundary (ARECS curve). This decrease can be a consequence of the progressive decline in abundance of the Cretaceous species that survived due to biological competition with the new Tertiary species or, simply, the decrease in the relative proportion of reworked specimens. Nevertheless, independently of the fact that some species survived the K/T event, the existence of a gradual extinction pattern in the lowermost part of the Danian does not refute the hypothesis of a catastrophic event in coincidence with the K/T boundary. The K/T planktic foraminiferal catastrophic mass extinction of more than 70% is very compatible with the hypothesis of the impact of a large asteroid and its effects in the short, middle and long term.