The evolution and control of detrital sediment provenance in the middle and northern Okinawa Trough since the last deglaciation: Evidence from Sr and Nd isotopes

摘要

The Okinawa Trough (OT) is a large sink of sediments supplied by the East Asian continent. Identifying the provenance of the OT sediments is key to reconstructing the temporal and spatial variations of the terrigenous supply to this area and is important for understanding the impact of paleoclimatic and paleoceanographic variability on the sediment supply to this marginal sea over the late Quaternary. In this contribution, we show that radiogenic strontium (Sr) and neodymium (Nd) isotopes allow to efficiently distinguish Yellow and Yangtze/Taiwan River detrital sediments, and can be used to reconstruct distinct changes in the provenance of the detrital fraction of marine sediments from the middle and northern OT since the last deglaciation. The Sr and Nd isotope signatures are compared to those of the potential sediment sources, namely the Yellow and Yangtze Rivers, the Taiwan orogen, and volcanic material from the OT and nearby islands, and the relative contributions of these sources are reconstructed. The Sr and Nd isotope compositions of the detrital fraction in the two sediment cores recovered from the middle and northern OT show that the sediments mainly originated from the Yangtze River between 18 and 10.5 ka, which was caused by low sea level and a widely developed channel system on the continental shelf. During the period between 10.5 and 7.0 ka, the rising sea level resulted in elevated Yangtze and Yellow Rivers sediment input into the OT. Simultaneously, large-scale volcanic activity also contributed significant amounts of material to the OT. During the last 7.0 ka, besides important contributions from the Yellow River, the intensification of the Kuroshio Current resulted in increased delivery of sediment from Taiwan to the OT.