Abstract

Rare earth elements (REEs) and Nd isotopes are useful tracers for a variety of oceanic processes in both modern and past oceans. This presentation will cover some latest understanding of the marine cycling of REEs and Nd isotopes gained through the international GEOTRACES effort. In particular, I will present results of dissolved REE concentrations along ~12°S in the South Atlantic – the first full-depth zonal section of REEs across a major ocean basin. The section provides new insights into the REE cycling associated with a couple of prominent oceanic features, including oxygen minimum zone and hydrothermal venting. Using combined dense measurements and water mass mixing modeling developed upon the optimal multiparameter analysis, the relative control of water mass mixing and biogeochemical processes on the REE distributions in the South Atlantic has been quantified for the first time. In addition, I will present some new results of applying Nd isotopes to trace changes in ocean circulation during the Cretaceous. The new Nd isotope records reveal a tight coupling between ocean circulation and the global carbon cycle during the Cretaceous, and have important implications to the origin and maintenance of Cretaceous oceanic anoxic events (OAEs).