Rare Earth Elements and Nd Isotopes in Hydrothermal Metalliferous Sediments: Pleistocene and Cenozoic Paleoceanography

Rutgers University New Brunswick, New Brunswick NJ

Investigators

Abstract

In this study, the PIs will test and develop a new paleoclimate proxy- Rare Earth Element (REE) abundances of carbonate sediments that contain metalliferous sediment originating from hydrothermal plumes. In combination, the PIs will use Nd isotope values (?Nd) as a proxy to help unravel differences in weathering rates and sources from variations in seawater REE abundances due to other causes. The short residence times of the REE (<1-4 Ka) mean that potentially, these proxies could provide high resolution data. Preliminary data show that metalliferous sediment records bottom water REE patterns and that the REE patterns are virtually identical for the Atlantic and Pacific. The entire REE pattern is reflected in differences in Nd/Er. Preliminary data for a core for the last 135 Ka indicate that Nd/Er and ???O are well correlated, showing good potential for the proxy. Additional preliminary data for a longer period (last 28Ma) show interesting patterns and large changes in ?Nd and Nd/Er for this period, again arguing that these combined proxies have potential to identify changing weathering inputs to the ocean. In order to further evaluate this proxy, the PIs will analyze hydrothermal plume material from additional hydrothermal vents in the northern and southern EPR, carry out lab experiments of REE uptake in vitro, calibrate the Nd/Er proxy using Holocene core tops from SEPR cores, evaluate possible diagenetic effects on the preservation of the proxy signals using cores with known and diverse diagenetic histories, and explore the behavior of both proxies on Ma to 10 Ka time scales for large climatic variations in the Oligocene and Miocene.