Response of Terrigenous Sediment Input to Sea Level Change and East Asian Monsoon Evolution Since 30kyr in the Southwestern Taiwan Basin

The compositions of grain size, clay minerals, and geochemical elements in core sediments (TS4) from the southwestern Taiwan Basin (South China Sea) were investigated to assess the response of terrigenous sediment input to sea level change and the East Asian monsoon evolution since 30 kyr. The chronology was discussed based on foraminiferal AMS¹⁴C dates. Our results indicated that rivers in Taiwan have been the major sediment contributors since 30 kyr, followed by the Pearl River; and Luzon Island contribute little sediments to the southwestern Taiwan Basin. In this study, we reconstructed the variations in terrigenous sediment input by using the proxies such as Al ₂O₃ (%), F1 score, and TiO₂/CaO. The F1 score can be used to indicate the flux of terrigenous sediments. The contribution of Taiwanese rivers and the Pearl River were evaluated by using the value of (illite + chlorite)/kaolinite. The variations of Al₂O₃ (%), F1 score, and TiO₂/CaO values along the core were clearly correlated to the evolution of the East Asian summer monsoon since 30 kyr. Based on these records, we recognized three evolutionary stages of terrigenous sediment input in the southwestern Taiwan Basin. During stage Ⅰ (29–24 kyr), the input of terrigenous sediments continued to increase. During stage Ⅱ (24–11.5 kyr), the sediment input decreased at first and then increased, with the lowest value during the last glacial period (21–17kyr). Terrigenous sediment input during stage Ⅲ (11.5 kyr -) showed the decreasing first and then increasing trends, generally higher than those in the first and second stages. The variations of terrigenous sediment input in the study area corresponded well with the evolution of the East Asian summer monsoon since 30kyr. Increased terrigenous sediment input during 4–1.8 kyr was suggested to be caused by the enhanced ENSO activity. Sea level change does not alter the overall trend of terrigenous sediment input, but does change the relative contributions of rivers in Taiwan and the Pearl River.