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    ESR signal intensity of quartz in the fine-silt fraction of riverbed sediments from the Yangtze River: a provenance tracer for suspended particulate matter

    Saito K, Tada R, Zheng H, Irino T, Luo C, He M, Wang K, Suzuki Y

    Yangtze River, Riverbed sediment, Suspended particulate matter, Provenance, Electron spin resonance, Crystallinity index

    An ESR–CI plot of quartz in the fine-silt (4–16µm) fraction of riverbed samples from the major tributaries of the Yangtze

    The Asian summer monsoon exerts a strong influence on the hydrologic cycle in East Asia. Moreover, the distribution of heavy precipitation in the Yangtze River basin, which covers a large area of South China, is sensitive to changes in monsoon intensity. Thus, the paleo-distribution of heavy precipitation in the Yangtze basin is key in reconstructing the paleo-monsoon intensity. In this study, we established proxies for distinguishing sediments from the northwestern and southeastern parts of the Yangtze River basin, with the goal of using them to reconstruct the paleo-distribution of heavy precipitation in the basin based on changes in the provenance of detrital sediments, as determined using sediment records at the river mouth. The proxies included the electron spin resonance (ESR) signal intensity and the crystallinity index (CI) of quartz in modern riverbed sediments along the mainstream and tributaries of the Yangtze River. The data revealed that the fine-silt fraction of the sediments (which represents suspended particulate matter, SPM) from each major tributary can be distinguished on the basis of ESR signal intensity and CI values. The values for each tributary reflect the age and type of bedrock in the tributary basin and show distinct regional variations according to the distribution of geological blocks within the Yangtze basin. In addition, the analyzed ESR signal intensity and CI values of the fine-silt fraction of riverbed sediments below mainstream–tributary junctions agree well with values calculated according to a simple mixing model of SPM discharged from the tributaries and the mainstream.