Sr-Nd isotopic constraints on terrigenous sediment provenances and Kuroshio Current variability in the Okinawa Trough during the late Quaternary

The Okinawa Trough in the East China Sea continuously receives terrigenous sediments from the surrounding East Asian continent during the late Quaternary, which makes it an ideal site for the studies of land-sea interaction and sediment source-to-sink transport. Geochemical and Sr-Nd isotopic compositions of the detrital sediments in the middle Okinawa Trough allow the provenance discrimination and the reconstruction of paleoenvironmental changes over the last 30 ka. Large variations in Sr-87/Sr-86 ratios and epsilon(Nd) values occur between 14.0 and 7.1 ka, suggesting a significant change in sediment provenances from the dominance of the Changjiang (Yangtze River) and/or continental shelf to that of Taiwan Island. During the last glacial maximum, the continental shelf was largely exposed and the fine-grained sediments from the Changjiang and the shelf with higher Sr-87/Sr-86 ratios and lower epsilon(Nd) values might be transported directly into the middle Okinawa Trough. With the sea level rise during the deglacial period, the strengthening Kuroshio Current increasingly delivered Taiwan-derived fine sediments (lower Sr-87/Sr-86 ratios and higher epsilon(Nd) values) to the middle trough, while the sediment contribution from the East Asian continent became subordinate. This study suggests that the changes in sea level and the Kuroshio Current pathway during the late Quaternary predominantly determined the dispersal and deposition of the terrigenous sediments in the Okinawa Trough, and the Kuroshio Current might have obviously influenced the Okinawa Trough since 14 ka. This study illustrates that the radiogenic isotopic compositions of the fined-grained sediments are sensitive proxies to trace the sediment provenance and to reconstruct oceanic circulations in the west Pacific marginal seas. (c) 2012 Elsevier B.V. All rights reserved.