Red-silt interbeds in lava flows as archives of volcanism, Asian dust, and climate interactions: Geochemical and mineralogical comparisons with source soils and aeolian deposits

Fine-grained, reddish siliciclastic sediments alternate with basaltic lavas in the Quaternary volcanic field of Jeju Island, Korea. These thin sedimentary interbeds extend laterally, and widespread from coastal regions to the summit, suggesting regional deposition during volcanic quiescence. To address their unresolved origins, we conducted geochemical and mineralogical analyses of these sediments, comparing them with similar deposits from the Korean Peninsula and with potential source materials from Asian deserts. The sediments, designated as Red Silt (RS), exhibit a uniform, silty texture and reddish color. Their mineral composition—primarily quartz, sodic plagioclase, K-feldspar, micas, and illitic clay minerals—differs markedly from the surrounding volcanics. Geochemical fingerprinting using major and rare-earth elements indicate a close affinity between RS and silts of Asian deserts and arid regions, supporting their deposition from far-transported Asian dust. RS underwent post-depositional chemical weathering leading to significant depletion of plagioclase and K-feldspar. The degree of weathering varied across RS sections, reflecting the section-specific paleoclimatic conditions, ranging from cooler, drier to warmer, wetter climates. Compared to aeolian deposits of the Korean Peninsula, Jeju RS experienced milder weathering, likely due to relatively short subaerial exposure before burial. Subsequent heating underneath hot lava flow raised temperatures up to above 950 °C at the sediment top, inducing phyllosilicate decomposition, hematite crystallization, and red coloration. Jeju RS layers archive interactions among volcanism, Asian dust deposition, and climate change during the late Quaternary.