Calcareous plankton biostratigraphic fidelity and species richness during the last 10 m.y. of the Cretaceous at Blake Plateau, subtropical North Atlantic

Species distributions of well-preserved and diverse assemblages of planktonic foraminifera and calcareous nannofossils spanning the last 10 m.y. of the Cretaceous (middle Campanian through Maastrichtian) are analyzed from samples taken across a 1400 m depth transect at Blake Nose in the western subtropical North Atlantic (Ocean Drilling Program Sites 1049, 1050 and 1052). Age models constructed by integrating foraminiferal, calcareous nannofossil, and magnetic polarity datum events provide a reliable framework for temporal correlation of the sites. This framework enables comparisons of species richness and abundance among sites and evaluation of the reliability of first and last appearance datums for regional and global correlation. Among the standard primary zonal marker datums, six of nine planktonic foraminifer and six of seven calcareous nannofossil events are considered reliable for constraining the age-depth models. Secondary datum ages calculated for 17 planktonic foraminiferal events suggest correlation offsets among the three sites of