Data Sheet 1_Holocene dispersal of Chinese river-derived clays to the Korean coast linked to Kuroshio branch variability in the Yellow and East China Seas.docx

High-resolution Holocene variations in sediment provenance were quantitatively reconstructed using clay mineral, elemental, and strontium (Sr)–neodymium (Nd) isotopic data from a ~32-m-long sediment core recovered from a semi-enclosed bay on the southern Korean coast. These multiproxy records consistently reveal a prominent signal of Chinese-derived sediment input, which gradually weakens over time. Based on the clay mineral mixing model and the Al-Mg regression model, these Chinese clays contributed an average of ~70% of the clay-sized sediment during the middle Holocene (~6.3 to 2 ka), challenging the prevailing view that coastal sedimentation in this region was primarily dominated by Korean rivers, particularly the Seomjin River. The Chinese river-derived clays in the Korean coastal deposit are predominantly composed of <8 μm particles, implying long-distance transport across the Yellow and/or East China Sea shelves. Their contributions show stepwise changes around ~6.3 ka, ~5 ka, ~4.3–3 ka, and ~2 ka, correlating with variability in Kuroshio branch currents (Tsushima Warm Current, Yellow Sea Warm Current, and Jeju Warm Current) in the Yellow and East China Seas. Their influence likely initiated around ~6.3 ka and weakened markedly at ~2 ka coupled with slowdown or stabilization in sea-level rise, coincident with a shift from the marine- to freshwater-dominated conditions recorded by geochemical proxies and microfossil assemblages. Increased Huanghe clay input around ~5 ka suggests an enhanced influence of the Jeju Warm Current. Our study of coastal deposits in Korea provides quantitative insights into the long-distance dispersal of Chinese clays and new source-to-sink connections within the East Asian marginal seas.