ND isotope evolution in sedimentary mn/fe oxides: Tracing the variations of west pacific oceanographic exchange during the last 27KA

The Nd isotopic ratios of ancient seawater deduced from sedimentary Fe-Mn hydroxides can be used to trace variations of terrestrial input or ocean circulation with a centennial time-scale resolution in high sedimentation rate regions. The Pacific Ocean plays an essential role in global ocean circulation and climate due to its volume and role as a potential carbon reservoir but received little attention compared with the Atlantic. Here we present the Nd isotope compositions in the Fe-Mn hydroxides from two marine cores in west Pacific during the past 27 Ka. These cores, MD972143 and MD012403 were collected from the Benham Rise in the western Philippine Sea and southern Okinawa Trough, respectively. For core MD012403, εNd values range between -10.2 to -7.8 and the range of εNd values of MD972143 are -3.0 to -1.8. They show similar down core variations in εNd, both display about 5 ε units of variation during the past 27 Ka. The similarity of the Nd isotopic variation in MD012403 and MD972143 reveals basin-wide ocean circulation change during the Last Glacial Maximum_and the last deglaciation. The negative Nd isotope excursions shown in both cores suggested intensify of Antarctic Intermediate Water or increasing terrestrial input from continental shelf in the period of last glacial-interglacial transition. The lowest εNd values were detected at approximately 12 to 14 Ka after the LGM, which could be resulted from a high terrestrial input with less radiogenic Nd.