南海北部沉积物记录的早更新世气候变化

发布时间：2018-03-23 05:23

本文选题：南海沉积　切入点：早更新世　出处：《中国科学院研究生院(地球环境研究所)》2015年硕士论文　论文类型：学位论文

【摘要】：南海作为西太平洋最大的边缘海,毗邻西太平洋暖池,又地处典型的东亚季风区,其地理位置优越,不仅记录了全球气候变化,还叠加了显著的区域性规律和特点,是古环境古气候研究的理想场所。通过对南海北部陆坡ODP 1145站沉积物碳酸盐含量、陆源组分的含量及其粒度、磁化率、地球化学元素进行分析,尝试恢复早更新世时期(约2.5-1.5 Ma)南海北部的古气候环境变化,并将ODP1145站沉积物的碳酸盐含量、粒度和磁化率与灵台黄土-古土壤序列中的碳酸盐含量、粒度和磁化率进行对比,以探讨海相和陆相沉积记录的早更新世气候变化的异同,获得了以下几点初步认识:(1)ODP 1145站沉积物碳酸盐含量属于“大西洋型”旋回,陆源组分的含量主要受到了生源物质的稀释,陆源物质的平均粒径受海平面变化、河流输入物质等多种因素控制,磁化率变化可能主要与海洋自身的氧化-还原环境有关。(2)碳酸盐校正后的元素组成和Al标准化的元素比值主成分分析结果表明,ODP 1145站沉积物的元素组成变化主要受控于三个因素:生源物质产率(如Ca、Si),河流输入的陆源物质(如Al、Ti和Zr),海洋自生作用(Mg和Mn)。元素比值变化可用来反映生源和陆源物质的相对含量(Ca/Al)、源区的化学风化(K/Al)、粒度效应(Zr/Al)和海洋环境的氧化/还原转变(Mn/Al)。(3)元素含量和比值变化表明,早更新世生产力于约2 Ma和1.7 Ma呈阶段式降低,陆源物质输入于~2 Ma明显增加,海洋环境在~1.7 Ma以后变幅增大。沉积物的理化指标均在~2.0 Ma和~1.7 Ma发生显著变化,共同指示了早更新世东亚冬(夏)季风的两次阶段性增强(减弱)。频谱分析结果表明,海洋生产力和粒度变化可能主要受高纬地区的“冰盖效应”引起的海平面波动控制,源区的化学风化和海洋环境变化可能受到了高纬冰量和低纬度辐射的共同影响。(4)南海ODP 1145站沉积物与灵台黄土的同一气候指标(碳酸盐、粒度、磁化率)对比结果表明,南海的碳酸盐含量变化指示了早更新世时期东亚夏季风在~2.0 Ma和~1.7 Ma两次减弱,灵台黄土的碳酸盐含量变化趋势不明显。南海沉积物和灵台黄土的磁化率在剖面上的变化幅度整体上均呈逐渐较小的趋势,指示了早更新世时期东亚夏季风逐渐减弱。南海陆源组分和灵台黄土的平均粒径曲线变化,在冰期-间冰期尺度上大体一致,但变化趋势明显不同,说明了南海陆源组分的平均粒径除了受到冬季风影响外,可能还受到其它因素影响。
[Abstract]:As the largest marginal sea in the western Pacific Ocean, the South China Sea is adjacent to the Western Pacific warm Pool and is located in the typical East Asian monsoon region. Its geographical position is superior. It not only records the global climate change, but also superimposes significant regional laws and characteristics. It is an ideal place to study paleoclimate. By analyzing carbonate content, grain size, magnetic susceptibility and geochemical elements of sediment at ODP station 1145 on the northern slope of the South China Sea, This paper attempts to restore the paleoclimate environment changes in the northern part of the South China Sea during the early Pleistocene (about 2.5-1.5 Ma), and compares the carbonate content, granularity and magnetic susceptibility of the sediments in the ODP1145 station with the carbonate content, granularity and magnetic susceptibility in the Loess Paleosol sequence of Lingtai. Based on the discussion of the similarities and differences between the early Pleistocene climate change recorded in marine and continental sedimentary records, the following points have been obtained: the carbonate content in sediment of the 1145 station at 1: 1 ODP belongs to the "Atlantic type" cycle. The content of land-based components is mainly controlled by the dilution of biomass, and the average particle size of land-based materials is controlled by sea level changes, river inputs, and other factors. The variation of magnetic susceptibility may be mainly related to the redox environment of the ocean itself. 2) the element composition after correction and the principal component analysis of Al standardized element ratio indicate that the element composition of sediments at ODP 1145 station is mainly changed. It is controlled by three factors: the yield of biogenic material (such as Caansii), the input of terrestrial material from rivers (such as Alnti and zirconium, the marine authigenic action of mg and MnN). The change of elemental ratio can be used to reflect the relative content of biogenic and terrestrial material and the chemical wind in the source region. The change of element content and ratio of K / Al, grain size effect and redox transition of mn / Al / Al ~ (3) in marine environment shows that, The productivity of early Pleistocene decreased at about 2 Ma and 1.7 Ma, the input of continental material increased obviously at 2 Ma, and the variation of marine environment increased after 1.7 Ma. The physical and chemical indexes of sediments changed significantly at 2.0 Ma and 1.7 Ma, respectively. The results of spectrum analysis show that the variation of ocean productivity and grain size may be mainly controlled by sea level fluctuations caused by the "ice cap effect" in high latitudes. Chemical weathering and marine environmental changes in the source area may be affected by the amount of high latitude ice and radiation from low latitudes.) the comparison of the same climatic index (carbonate, granularity, magnetic susceptibility) between sediment and Lingtai loess at ODP 1145 station in the South China Sea shows that. The carbonate content changes in the South China Sea indicate that the East Asian summer monsoon weakened at 2.0 Ma and 1.7 Ma during the early Pleistocene. The change trend of carbonate content in Lingtai loess is not obvious. The magnetic susceptibility of South China Sea sediment and Lingtai loess are gradually decreasing in the whole profile. The results indicate that the East Asian summer monsoon gradually weakened during the early Pleistocene. The mean particle size curves of the continental components of the South China Sea and Lingtai loess are roughly the same on the scale of glacial to interglacial, but the trend is obviously different. It is suggested that the average particle size of the terrestrial components in the South China Sea is affected by other factors besides the winter monsoon.
【学位授予单位】：中国科学院研究生院(地球环境研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P736.2;P532

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