Median grain size in ODP Sites 184-1143 and 184-1144@en

Monsoon climate is an important component of the global climatic system. A comprehensive understanding of its variability over glacial-interglacial time scales as well as of its effects on the continent and in the ocean is required to decipher links between climate, continental weathering and productivity. A detailed multiproxy study, including bulk and clay mineralogy, grain-size analysis, phosphorus geochemistry (SEDEX extraction), organic matter characterization, and nitrogen stable isotopes, was carried out on samples from ODP Sites 1143 and 1144 (Leg 184, South China Sea), covering the past 140 000 years. We tentatively reconstruct the complex sedimentation and climatic history of the region during the last glacial-interglacial cycle, when sea-level variations, linked to the growth and melting of ice caps, interact with monsoon variability. During interglacial periods of high sea level, summer monsoon was strong, and humid and warm climate characterized the adjacent continent and islands. Clay minerals bear signals of chemical weathering during these intervals. High calcite and reactive phosphorus mass accumulation rates (MARs) indicate high productivity, especially in the southern region of the basin. During glacial intervals, strong winter monsoon provided enhanced detrital input from the continent, as indicated by high detrital MAR. Glacial low sea level resulted in erosion of sediments from the exposed Sunda shelf to the south, and clay mineral variations indicate that warm and humid conditions still prevailed in the southern tropical areas. Enhanced supply of nutrients from the continent, both by river and eolian input, maintained high primary productivity. Reduced circulation during these periods possibly induced active remobilization of nutrients, such as phosphorus, from the sediments. Intense and short cold periods recorded during glacial and interglacial stages correlate with loess records in China and marine climatic records in the North Atlantic, confirming a teleconnection between low- and high-latitude climate variability.季风气候是全球气候系统的重要组成部分。要解析气候、大陆风化与生产力之间的关联，需全面理解其在冰期-间冰期时间尺度上的变化特征，以及其对大陆与海洋的影响。研究团队对取自南海第184航次大洋钻探计划（Ocean Drilling Program, ODP）1143与1144站位、覆盖过去14万年的沉积物样品开展了详细的多代用指标研究，分析内容涵盖全岩与黏土矿物学、粒度分析、磷地球化学（SEDEX萃取法）、有机质表征以及氮稳定同位素分析。本研究尝试重建末次冰期-间冰期旋回期间该区域复杂的沉积与气候演化历史——在此期间，与冰盖生长消融相关的海平面变化与季风扰动相互作用。在海平面较高的间冰期，夏季风强盛，毗邻的大陆与岛屿呈现暖湿气候特征；此时期的黏土矿物记录了化学风化信号。高方解石与活性磷质量堆积速率（Mass Accumulation Rate, MAR）指示研究区尤其是盆地南部区域具有较高的生物生产力。在冰期阶段，强劲的冬季风带来了更多的大陆碎屑输入，这一点可由较高的碎屑物质MAR得到佐证。冰期海平面下降导致南部裸露的巽他陆架发生沉积物侵蚀，黏土矿物组成变化则表明，此时南部热带区域仍以暖湿气候为主。通过河流与风成输入的大陆营养盐供给增强，维持了较高的初级生产力。此时期环流减弱，可能引发沉积物中磷等营养盐的活跃再活化。冰期与间冰期阶段记录的短暂强冷事件，与中国黄土记录以及北大西洋海洋气候记录具有良好的对应关系，证实了低纬度与高纬度气候扰动之间存在遥相关。