Neodymium isotope composition of late Cretaceous fish teeth and debris

Nd isotopes of fossil fish teeth and debris represent one of the few water mass tracers that can be used to reconstruct deep ocean circulation. We present Nd isotopic data interpreted as bottom water values for 290 samples from three Ocean Drilling Program sites on Demerara Rise (Sites 1258, 1260, and 1261) along with 102 analyses from four other North Atlantic sites (Cape Verde, Goban Spur, Bermuda Rise and Blake Nose) that provide additional geographic and bathymetric control.

Our results confirm the presence of a water mass with low e-Nd values (-14 to -17) that are believed to be influenced by continental material during local water mass formation at low latitudes. This Demerara Bottom Water (DBW) is the primary water mass in the region from the Cenomanian to Coniacian and from the late Campanian through early Maastrichtian following a hiatus of ~ 10 my. A positive 8 e-Nd unit excursion occurs during Ocean Anoxic Event 2 (OAE2) that cannot be explained by changes in weathering inputs, diagenesis or magmatic sources of Nd; instead, it appears to represent an influx of bottom waters sourced from the Tethys or North Atlantic.