Chicxulub impact event is Cretaceous/Paleogene boundary in age: New micropaleontological evidence

High-resolution and quantitative planktic foraminiferal biostratigraphy from two SE Mexico stratigraphic sections (Bochil, Guayal) shows that the Chicxulub-related Complex Clastic Unit (CCU) is synchronous with the ejecta-rich airfall layer and the Cretaceous/Paleogene (K/Pg) catastrophic mass extinction horizon in the El Kef (Tunisia) and Caravaca (Spain) sections. The lowermost Danian H. holmdelensis subzone (= Biozone P0) was identified in both sections in a thin dark clay bed just above the CCU, proving that such bed is chronostratigraphically equivalent to the K/Pg boundary clay of the El Kef stratotype. These new micropaleontogical data confirm that the K/Pg impact event and the Chicxulub impact event are the same one. This contradicts the suggestion by others that the Chicxulub impact predated the K/Pg boundary by about 300 ka.