Evidence for multimillion-year diachroneity of the paleomagnetically defined Santonian-Campanian stage boundary between its European stratotypes and Pacific Ocean basin localities

Abstract The recent and revolutionary decision by the International Union of Geological Sciences to formally define the Santonian-Campanian (Cretaceous) stage boundary at the paleomagnetic polarity change between magnetochron C34n (the “Cretaceous Long Normal”) and the reversed polarity of C33r dated 83.6 Ma now allows high-resolution dating of this boundary to regions both geographically far from the European stage stratotypes, but more importantly, to regions that share few or none of the biostratigraphically important species that help define these stages in their stratotype regions. However, as demonstrated here, a significant error in the identification of the biostratigraphic zone, whose base most nearly coincides with the C34n-C33r boundary for much of the Indopacific Faunal Realm, has created a multimillion-year error in correlation to the stratotype section in Italy. Secondly, it is shown here that there appears to be a misidentification of magnetochron C33r (and thus its boundaries) in the currently accepted, Campanian stage chronostratigraphy for the Northwest Pacific region (Japan and Sakhalin) of the Indopacific Faunal Realm, which further causes diachroneity. Thirdly, here for the first time, the Santonian-Campanian boundary in Antarctica can be based on magnetostratigraphy integrated to cosmopolitan (Indopacific) ammonite and inoceramid species, taxa also found in the Northeast and Northwest Pacific region, thus allowing first-order correlation. The concluding part of this paper contains a proposal for two new auxiliary stage boundary stratotypes (one for the Northeast Pacific and another on James Ross Island, Antarctica) and a proposal for defining a three-substage Campanian based entirely on magnetostratigraphy integrated to high-resolution mollusk and microfossil biostratigraphy.