NOAA/WDS Paleoclimatology - East China Sea (IODP U1428, U1429) Geochemistry Data during the last 400 ka

We examine the paleoceanographic record over the last ~400 kyr derived from major, trace, and rare earth elements in bulk sediment from two sites in the East China Sea drilled during Integrated Ocean Drilling Program Expedition 346. We use multivariate statistical partitioning techniques (Q-mode factor analysis, multiple linear regression) to identify and quantify five crustal source components (Upper Continental Crust (UCC), Luochuan Loess, Xiashu Loess, Southern Japanese Islands, Kyushu Volcanics), and model their mass accumulation rates (MARs). UCC (35-79% of terrigenous contribution) and Luochuan Loess (16-55% contribution) are the most abundant end-members through time, while Xiashu Loess, Southern Japanese Islands, and Kyushu Volcanics (1-22% contribution) are the lowest in abundance when present. Cycles in UCC and Luochuan Loess MARs may indicate continental and loess-like material transported by major rivers into the Okinawa Trough. Increases in sea level and grain size proxy (e.g., SiO2/Al2O3) are coincident with increased flux of Southern Japanese Islands, indicating localized sediment supply from Japan. Increases in total terrigenous MAR precede minimum relative sea levels by several thousand years and may indicate remobilization of continental shelf material. Changes in the relative contribution of these end-members are decoupled from total MAR, indicating compositional changes in the sediment are distinct from accumulation rate changes but may be linked to variations in sea level, riverine and eolian fluxes, and shelf-bypass processes over glacial-interglacials, complicating accurate monsoon reconstructions from fluvial dominated sediment.

本研究针对综合大洋钻探计划（Integrated Ocean Drilling Program）第346航次在东海钻取的两个站位的全岩沉积物（bulk sediment），通过其中的常量元素、微量元素与稀土元素，重建了过去约40万年的古海洋记录。本研究采用多变量统计分区技术（包括Q型因子分析、多元线性回归），识别并定量了5种地壳物源组分：上地壳（Upper Continental Crust, UCC）、洛川黄土、下蜀黄土、日本南部诸岛以及九州火山岩，并对各组分的质量堆积速率（mass accumulation rates, MARs）进行了模拟。纵观时间序列，上地壳（占陆源贡献的35%~79%）与洛川黄土（占16%~55%）是丰度最高的端元组分；而当其他组分出现时，下蜀黄土、日本南部诸岛与九州火山岩的占比仅为1%~22%，为丰度最低的端元。上地壳与洛川黄土的质量堆积速率周期变化，可能指示了大型河流搬运的陆源类黄土物质输入至冲绳海槽。海平面上升与粒度替代指标（如SiO₂/Al₂O₃）的升高，与日本南部诸岛的沉积物通量增加相吻合，表明存在来自日本的局地沉积物供给。总陆源质量堆积速率的升高较相对海平面最低值早数千年，这可能指示了大陆架物质的再搬运。上述端元组分的相对占比变化与总质量堆积速率解耦，表明沉积物的组成变化与堆积速率变化相互独立，但可能与冰期-间冰期旋回中的海平面波动、河流与风尘通量变化以及陆架绕流过程相关，这使得基于以河流作用为主的沉积物开展精准的季风演化重建变得更为复杂。