南海台西南盆地南部海域TS6孔常量元素地球化学特征及其古环境意义

通过对南海台西南盆地南部海域TS6柱状样沉积物样品常量元素地球化学特征的分析,结合粒度和AMS14C测年分析结果,探讨了研究区末次冰消期以来的沉积环境及气候变化特征。常量元素垂向序列显示元素Mn在沉积物近表层大量自生富集,指示近现代底层水高度富氧,表明研究区水体环境条件十分有利于水成成因的铁锰结核发育;常量元素统计分析表明,Al、Fe、Mg、K、Ti代表了陆源元素组合;陆源常量元素比值Al2O3/TiO2、TFe2O3/TiO2、MgO/TiO2和MgO/Al2O3记录了研究区末次冰消期以来的部分气候波动事件,其中全新世9.8~9.4 kaBP和6.5~5.8 kaBP阶段发生了两次气候变冷事件,指示东亚夏季风强度明显减弱,并且6.5~5.8 kaBP阶段冷事件表现出“双峰”特征。各常量元素比值指示末次冰消期18.5和15.8 kaBP左右可能也出现了气候变冷事件,其中15.8 kaBP出现的冷事件应该对应于H1事件。

Geochemical characteristics and paleoenvironmental significance of the major elements in the sediments of CoreTS6 from the southern part of Southwest Taiwan Basin of the South China Sea

Geochemical characteristics of major elements from the column sample TS6 in the southern part of Southwest Taiwan Basin,together with the grain size and AMS14C dating data are studied for both the changes in depositional environment and climate of the area since the last deglaciation.Vertical distribution of the major elements shows that Mn is autogenous and abundantly enriched near the surface of sediments,suggesting that the modern bottom water is highly oxygen-enriched.The water environmental conditions of the study area,therefore,are very beneficial for the deposition of hydrogenic ferromanganese nodules.Statistical analysis of major elements suggests that the major elements of Al,Fe,Mg,K and Ti represent the terrigenous element association.The ratios of these terrigenous elements,such as Al2O3/TiO2,Fe2O3/TiO2,MgO/TiO2 and MgO/Al2O3,are closely related to climatic fluctuations since the last deglaciation.Two climatic cooling events are observed in the periods of 9.8 kaBP^9.4 kaBP and 6.5 kaBP^5.8 kaBP respectively,indicating that the intensity of East Asian summer monsoon was significantly weakened then.The cooling event happened during the period of 6.5 kaBP^5.8 kaBP showed a pattern of"double peaks".The ratios of major elements further indicate that there may also be some climatic cooling events around 18.5 kaBP and 15.8 kaBP in the last deglaciation,and the cold event at 15.8 kaBP should correspond to the event of Heinrich 1.