No evidence of multiple impact scenario across the Cretaceous/Paleogene boundary based on planktic foraminiferal biochronology

Abstract

ABSTRACT Large bolide impacts seem to have strongly affected biological evolution, causing detrimental effects on the biosphere. The best-known case is the Chicxulub impact (Yucatan Peninsula, Mexico), the most probable trigger of the Cretaceous/Paleogene boundary (KPB) mass extinction. Nevertheless, after four decades of intensive research, a consensus on the causal relationship between the impact and the mass extinction has not yet been reached. Most of the scientific community has established multiple, strong arguments for the Chicxulub impact as the most likely and principal cause of the KPB mass extinction. However, a variety of hypotheses link the mass extinction mainly to the volcanism of the Deccan Traps and one or more bolide impact events within a relatively short time through the KPB: one impact in the late Maastrichtian (66.3 Ma), corresponding to the Chicxulub impact, a larger one at the KPB (66 Ma), and a final one in the early Danian (65.9 Ma). Here, we report on the controversies relating to the correlation of the Chicxulub impact event with the mass extinction, with a focus on the stratigraphy and biostratigraphy of sections in Mexico, Cuba, and Haiti, which include ejecta-rich clastic deposits linked to the Chicxulub impact. High-resolution biostratigraphy and quantitative data with planktic foraminifera reveal that these deposits are synchronous with the ejecta-rich airfall layer and the KPB mass extinction horizon of the El Kef, Tunisia, stratotype. Our results provide no support for a multiple impact scenario but confirm that the Chicxulub impact event is indeed the KPB impact event. Furthermore, we have not found any biostratigraphic evidence to support an additional Danian impact event near the Gulf of Mexico region.