Sr–Nd isotopes indicating the provenance of siliciclastic sediments and paleoenvironmental changes in the middle Okinawa Trough during the last deglaciation

Abstract

Sediment provenance and transport, together with the forcing mechanism behind provenance changes in the middle Okinawa Trough over the past 16 kyr, were reconstructed using records of elemental and Sr–Nd isotopic compositions within the chronological framework of accelerator mass spectrometry radiocarbon dating. Results clearly revealed four notable phases of change in the sediment provenance those are closely related to sea-level fluctuations, the development of the Kuroshio Current (KC), magnitude of tidal bottom stress, and climatic variability of the East Asian monsoon. The sediments of Unit 1 (16–13.8 kyr BP) originated primarily from Changjiang, with a small degree originating from paleo-Huanghe as a result of low-stand sea-level deposition. The sediments of Unit 2 (13.8–11.6 kyr BP) originated from Taiwan the strengthening of because of the KC and the gradual landward retreat of the river mouth; the contribution of Changjiang sediments was reduced. The dominant provenance of Unit 3 (11.6–8.3 kyr BP) changed to seafloor erosion or resuspension and Taiwan sediments with an admixture of Changjiang-derived sediments. After that period, currents, especially the intense KC-dominated deposition, led to dominant sediment supplies from Taiwan during the enhanced KC interval of 8.3–5.4 kyr BP. A prominent decrease in Taiwan-derived particle supply at 5.4–2.8 kyr BP resulted from the suppression of the KC related to the Pulleniatina minimum event. This study suggests that Sr–Nd isotope compositions are useful proxies for understanding the linkage between river sediment source-to-sink processes and paleoenvironmental changes in East Asian marginal regions.