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Despite the well-reconstructed paleoceanography of the late Quaternary deposits in the East (Japan) Sea (ES), provenances of terrigenous sediments and a comprehensive interpretation of their variations since the Last Glacial Maximum remain unclear, especially in regard to the mainland China- and Taiwan-derived matter. Grain size, conservative trace elements, rare earth elements (REEs), Nd isotope, and clay mineralogy of core sediments from the Ulleung Basin of the ES were investigated for better understanding of detrital sediment provenance and transport process and then their forcing mechanisms over the last 21 kyr. Geochemical–mineralogical multi-indices in this study showed notable three-phase changes in sediment provenance, which can be closely related to sea-level fluctuation, development of the Tsushima Warm Current as well as intermittent influence from the East Asian summer monsoon climate evolution. During Unit 1 (21.1–8.4 kyr BP) when the Tsushima Warm Current was absent in the ES, the paleo-Changjiang and the paleo-Huanghe mouth might be situated close to the study area and thus mainland China could have played major role in the southwestern Ulleung Basin sedimentation. In particular, the formation of rhythmic dark-colored alternation in Unit 1 is possibly attributable to the pulse of paleo-Huanghe discharge associated with centurial- to millennial-scale variability in the East Asian summer monsoon. In Unit 2 (8.4–7.2 kyr BP), these river mouths gradually retreated to their present positions with global sea-level rise, leading to decreasing terrigenous sediment supply from mainland China to the study area. Since 7.2 kyr BP (Unit 3), sedimentation in the Ulleung Basin should still be mainly derived from mainland China. Meanwhile, increasing chlorite/kaolinite ratio but decreasing ε Nd value revealed that terrigenous matter from Taiwan might have been limitedly transported northward to the study area by the fully evolved Tsushima Warm Current. A prominent decline in chlorite/kaolinite ratio, together with contrast change on ε Nd value, centered at around 2.9 kyr BP (3.3–2.4 kyr BP) may have been caused by the Tsushima Warm Current suppression, possibly related to the Pulleniatina minimum event popularly found in the study area and nearby seas. [ABSTRACT FROM AUTHOR]

Abstract: A millennial-scale paleoceanographic record of the Ulleung Basin in the southern part of the East (Japan) Sea (ES) for the last 20,000years was reconstructed based on variations in the element compositions of core sediment. Most of the elements showed relatively wide content ranges throughout the core, largely because of different sediment types, their grain size spectra, biological components, and geochemical conditions (i.e., redox conditions). In particular, biogenic components (Ca, Sr, Ba, and CaCO3) and some minor elements (Cu, Mn, Mo, U, Cd, Zn, and V) revealed three distinct intervals of major paleoceanographic changes. Interval 1 (∼18–9.3kyr BP) is characterized by a rhythmic alternation of dark- and light-colored sediment bands. Distinctive differences in the abundance of organic carbon, carbonate, and redox-elements between the dark- and light-colored-sediment layers are probably attributable to especially those associated with bottom-water redox variations combined with the enhanced primary productivity and water stratification in the Ulleung Basin. These alternations perhaps reflect fluctuations in paleo-discharge from Chinese and/or Korean rivers during the last deglaciation. From a global perspective, the repetition of dark sapropelic sediment layers suggests a possible teleconnection between oceanographic change and development of the East Asian summer monsoon and consequent fluctuations in fluvial discharge from Korean and Chinese rivers to the East Sea basin. In Interval 2 (9.3–6.5kyr BP), a remarkable increase in the concentrations of organic carbon and redox elements is probably linked to the intrusion of the warm/saline Tsushima Current to the basin, which would have enhanced ventilation and upwelling of nutrient-rich sub-surface waters. In parallel, a pronounced decrease in carbonate content indicates extensive carbonate dissolution due to the consumption of large amounts of free pore-water oxygen in surface sediments that would have accompanied by the decomposition of organic matter. In Interval 3 (6.5kyr BP–Present), most geochemical parameters are relatively constant, suggesting little changes in paleoenvironments; these observations indicate that modern oceanographic conditions were established in the East Sea at about 6.5kyr BP. In particular, a prominent decline in carbonate contents centered at around 3–4kyr BP appears to have been caused by a decrease in primary productivity in association with a suppression of the warm Kuroshio Current, rather than by geochemical processes. [Copyright &y& Elsevier]