An unresolved controversy in paleoceanography is the role of warm, saline bottom water (WSBW), presumably formed at low latitudes in restricted marginal basins, now occurring in deep water circulation. Stable oxygen and carbon isotope data suggest WSBW may have dominated ocean circulation at several times in the past, but stale isotope signatures are not unique water mass tracers. Due to the short oceanic residence time of Nd and the distinct Nd isotope input values to different water masses, this Nd isotopic system may be a conservative tracer of water mass. Fish tooth apatite may provide a deep water record through Nd isotopes. This study should aid in evaluating the timing and mechanism of the rare earth element (REE) uptake in fish tooth apatite by examining samples from two deep sea sites with different lithologic controls on diagenetic alteration. It should also allow us to determine fish tooth composition across the Paleocene/Eocene boundary, a time of proposed WSBS formation. Major changes in the mode of ocean circulation in the past would impact nutrient distributions and redox conditions, as well as the transfer of heat and air/sea exchange of atmospheric gases that directly influence global climate.
