THE PALEOENVIRONMENTAL SIGNIFICANCE OF THE CHARACTER OF THE ELEMENT GEOCHEMISTRY IN THE SOUTHWESTERN SOUTH CHINA SEA SINCE LATE PLEISTOCENE
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摘要: 对南海西南部近湄公河三角洲中陆坡上的MD01-2392站样品进行的地球化学分析表明,该站的沉积物主要为湄公河带来的陆源碎屑,并且其物源四十万年来没有发生明显变化。分别用元素TiO2、CaO估算出沉积物中陆源碎屑的含量及CaCO3的含量,结果显示CaCO3在间冰期时高,而在冰期时低,表现出"大西洋旋回"的特征。陆源碎屑含量与CaCO3含量相反,显示出南海CaCO3旋回属于稀释旋回。元素的Ti标准化值表明,该站沉积物源区在冰期时化学风化弱,而在间冰期时相对较强,说明间冰期时物源区存在相对温暖湿润的气候环境。Abstract: Analysis of the geochemistry and granularity has been performed on samples from core MD01-2392 at middle slope near the Mekong delta, southern South China Sea (SCS). The result indicates that the Mekong River was the main source of the MD01-2392 sediment and the source area did not change much in the past 400 ka. Variations in Ti and CaO concentrations were used to track the change of terrestrial and the biogenic carbonate contents respectively. It indicated that the content of CaCO3 follows the "Atlantic cyclicities" of low values during glacials and high values during interglacials. In contrast, the content of terrigenous sediment shows an opposite glacial-interglacial variation pattern. The results indicate that the CaCO3 cycle at this SCS locality was strongly influenced by terrigenous dilution. Ti-normalized ratios and the behavior of the elements during chemical weathering reflect stronger chemical weathering in interglacials than in glacials. This indicates that warm and wet climate occurs in the source area. The Ti-normalized ratios of the REE are influence by the percentage of the terrestrial materials.
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