Late Cretaceous to Eocene calcareous nannofossil distribution near Gubbio, Italy

Using a modified sample preparation technique, we have been able to establish a detailed lower Campanian to upper Eocene nannofossil stratigraphy in the Bottaccione and Contessa Highway sections near Gubbio. Appearance and extinction levels of virtually all the commonly used calcareous nannofossil zonal markers have been recognized and can now be closely correlated with the planktonic foraminifera zonation and the magnetic reversal stratigraphy previously established in these sections. Comparisons with the nannofossil calibrations of the oceanic magnetic anomaly sequence in Deep Sea Drilling Project (DSDP) sites suggest that magmetic Subchrons C17N and C25N are missing in the Bottaccione section. The observed variability of the relative stratigraphic position of most plankton events is confirmed to less than one magnetic subchron. Absolute abundance, paleobiogeographic restriction, and differential preservation render some of the traditionally used biostratigraphic events less reliable than others.