南黄海北部晚更新世以来常量元素记录的化学风化作用

以南黄海北部高沉积速率柱状样DLC70-3孔作为研究对象，对沉积物的黏土矿物和常量元素地球化学组成进行了综合分析。结果显示，DLC70-3孔沉积物中黏土矿物组合以伊利石为主，其次为蒙皂石，绿泥石和高岭石含量较低；绝大部分样品中伊利石与蒙皂石含量的比值<6，表明沉积物主要来源于黄河物质的输送。研究认为DLC70-3孔沉积物的化学风化指标CIA值受到海平面变化和源区气候变化共同控制，其中源区的气候变化为主要控制因素，而海平面变化造成的机械沉积分异作用主要影响27.80~38.00 m（MIS 4）层位沉积物的CIA值。CIA值显示在MIS 5和MIS 3期大陆化学风化作用较强，与内陆黄土高原地区夏季风和化学风化指标的变化趋势一致，尤其是在MIS 3早期（40~60 ka）记录的化学风化作用非常强，反映了黄河流域地区出现强夏季风降雨过程。

Chemical Weathering Recorded by Major Element of Northern South Yellow Sea since Late Pleistocene

The chemical weathering of silicate rocks in continents as an important sink of atmospheric CO₂ is of great significance for global environmental change.The chemical index of alteration (CIA) has been widely used as a proxy for chemical weathering in sediment source area. This study presents combined clay minerals and major elements analyses on bulk sediments from a 71-m-long core with high sedimentation rate from northern South Yellow Sea and containing a Late Pleistocene record. After examining the variations of clay minerals and major elements compositions of the core sediment, we develop clay minerals and geochemical proxies to identify the origins of the DLC70-3 Core sediments,especially to discriminate the Yangze River-derived and Yellow River-derived sediment provenances. Further-more, CIA indices are also applied to decipher the chemical weathering record in sediment source area.Results show that combination of clay minerals is given priority to illite, followed by smectite, with low chlorite and kaolinite. In the vast majority of samples the ratios of illite to smectite is less than 6, indicating that the sediments are mainly transported by the Yellow River.The research suggests that the chemical weathering index (CIA) of the sediment in DLC70-3 Core is controlled together by the sea level change and the climate change of the source area, of which the latter one is the major controlling factor. However, the mechanical sedimentary differentiation caused by the sea level change might have affects CIA values at the depth of 27.80~38.00 m corresponding to MIS 4 of coarse grained sediments greatly. CIA values reveal that during MIS 5 and MIS 3 the continental chemical weathering is relatively strong, which is consistent with the trend of summer monsoon and chemical weathering index of the inland Loess Plateau area, especially in the early stage of the MIS 3 (40~60 ka), the record of chemical weathering is very strong, which reflects a strong summer monsoon rainfall process in the Yellow River basin. Although the high resolution paleoenvironmental changes can not be easily reconstructed due to ubiquitous unconformity in the sedimentary strata and weak age controls compared to the deep sea sedimentation, the present study sheds new lights on the understanding of the East Asian palaeomonsoon activity in the Yellow River Basin.