Abstract:

Nd isotope of ocean waters has become an important tracer for continental weathering and oceanic circulation. Dissolved oceanic Nd is controlled by input from continental weathering, while hydrothermal input can be ignored. The Nd isotope composition of seawater is not uniform in the presentday oceans because the oceanic residence time (5001000 a) of Nd is shorter than the mixing time (~1500 a) of the ocean and the relative contributions of Nd from ancient continental versus young volcanogenic materials differ in  various basins. Therefore, the Nd isotope system has been used as a tracer for water exchange and paleoocean circulation. There are four major marine materials which can preserve Nd isotope compositions of paleoocean waters: hydrogenetic ferromanganese crusts, planktonic or benthic foraminifera, fossil fish teeth or bones, authigenic FeMn oxide fraction in marine sediments. Each material has its own advantages and disadvantages. Cenozoic Nd isotopic evolutions of major oceans on timescales of millions have been acquired by analyzing FeMn crusts. High resolution Nd isotopic evolution can be acquired through studying foraminifera, fossil fish debris and FeMn oxides.According to Nd isotopic evolution we may reconstitute the  water exchange to trace open and closure of paleoseaways, which can be used to study the relationship between tectonic activities and climate changes. The combination of  Nd isotope and the proxies for climate change can be used to study the relationship between ocean circulation and climate shifts. Nd isotope of surface water can provide information about continental weathering input.

Key words: Key words: Nd isotope; ocean circulation; weathering; paleoclimate