Deep-water agglutinated foraminiferal changes and stable isotope profiles across the Cretaceous–Paleogene boundary in the Rotwandgraben section, Eastern Alps (Austria)

The studied interval extends from 2.5 m below to 1 m above the Cretaceous–Paleogene (K–P) boundary and encompasses the uppermost Abathomphalus mayaroensis, PO (subzones: POa — Guembelitria cretacea and POb — Globoconusa conusa), Pα or Parvularugoglobigerina eugubina and lowermost P1 (subzone: P1a or Subbotina pseudobulloides) planktonic foraminiferal zones. glutinated benthic foraminiferal assemblages of the uppermost Abathomphalus mayaroensis Zone are moderately diversified and composed of mixed epifaunal and infaunal morphogroups. In the lower part of the Guembelitria cretacea Subzone benthic foraminifers are extremely rare and represented only by a few epifaunal species; in the upper part of this subzone they are still not abundant but assemblages are again moderately diversified. In the Globoconusa conusa Subzone deep-water agglutinated foraminifers are abundant, highly diversified and represented by mixed epifaunal and infaunal morphogroups. ock stable isotope analysis shows a significant drop of both δ13C and δ18O values at the K–P boundary. ears that a drastic decrease in abundance and diversity of deep-water agglutinated foraminifers as well as a change of the community structure from mixed epifaunal and infaunal to one dominated by epifaunal morphogroups are related to a reduction in marine primary productivity. stantaneous environmental stress and the collapse of primary productivity, are compatible with a large bolide impact.