Planktonic foraminiferal and calcareous nannofossil biostratigraphy and magnetostratigraphy of the uppermost Campanian and Maastrichtian at Zumaia, northern Spain

► Campanian/Maastrichtian boundary (C/M) lies in Chron C31r at Zumaia. ► C/M boundary approximated by base P. palpebra, top B. parca subsp. constricta. ► C31r/C31n, bases L. quadratus, R. fructicosa may define l/u Maastrichtian boundary.