REEs and Sr-Nd isotope variations in a 20 ky-sediment core from the middle Okinawa Trough, East China Sea: An in-depth provenance analysis of siliciclastic components

Abstract

We analyzed rare earth elements (REEs) and SrNd isotope compositions of siliciclastic components in a sediment core from the middle Okinawa Trough (OT), to elucidate spatiotemporal variations in the sediment provenance, and their underlying mechanisms for the last 20 ky. Our results show that the trough deposits were characterized by different proportions of Changjiang- and Taiwan-derived (especially, the western rivers) sediments over time, from which we infer dramatic changes in sea-level, intensity of the Kuroshio Current (KC) inflow, and the East Asian monsoon since the last glacial maximum (LGM). In contrast to previous studies, the sea-level lowstand proximity of the paleo-Changjiang to the middle OT, and the contemporaneous enhancement of the East Asian winter monsoon (EAWM) may have played pivotal roles in supplying terrigenous inputs and forming middle OT deposits during the last glacial period, whereas the paleo-Huanghe was of lesser importance. After the early Holocene (especially the late Holocene cold period between ~4.8 and ~2.7 cal ky BP), a remarkable shift in the combined records of REEs and Nd isotopes reveals a causal link between variations in the Taiwan source and the KC inflow, coupled with climate changes in the East China Sea (ECS). This study suggests that SrNd isotope compositions and REEs are useful proxies for understanding the links between river development and paleoenvironmental/paleoclimatic changes in East Asian marginal regions.