澳大利亚大堡礁海域近15万年沉积记录及古气候演化

发布时间：2018-01-22 02:15

本文关键词： 大堡礁碳酸盐石英有机质红度　出处：《中国地质大学（北京）》2014年博士论文　论文类型：学位论文

【摘要】：气候变化及其对人类生存环境影响的问题对于人类的生存和发展至关重要。探索古气候变化的动力成因机制，可以预测未来气候变化趋势成。研究末次冰期-间冰期南半球低纬海洋海平面及气候变化的历史，对于揭示第四纪晚期南极冰盖变化及其导致的全球气候环境变化具有重要的指示意义，而相关研究十分有限。因此，本文研究了IODP325航次的沉积岩芯柱矿物学和地球化学特征，并将其与南极Vostok冰芯古气候阶段进行对比。采用了综合分析方法，包括：不平衡铀系（U-Th）定年法、X射线粉晶衍射方法、总碳、总无机碳和总有机碳含量分析、沉积物光谱分析（亮度、红度和黄度）。研究结果表明，澳大利亚大堡礁海域海平面变化对南极冰盖增加或消融变化响应敏感。所研究的沉积岩芯柱覆盖时间长达15万年:在140-116ka BP期间，为末次冰期发生之前的暖期，冰川融化，海平面较高。沉积物红度增加，说明该时期大堡礁海域及沿岸温度较高、降雨量及其导致的入海径流较大，随之入海的石英等矿物也增多，形成较低的碳酸盐/石英含量比值；随着全球气候进入末次冰期，尽管也有冷暖变化，但整体上，大堡礁海域海平面较低。在116-73ka BP期间，沉积物红度较低，陆源输入较少，大堡礁海域海洋古生产力较低，导致沉积物有机质含量较低；在73-58ka BP期间，大堡礁海域沿岸为冷干期，海平面也较低，该时期M0058A沉积岩芯主要由砂构成；在58-30ka BP期间，大堡礁海域降雨转多、气候较为湿润，但碳酸盐/石英含量比值较低，陆源输入物质较多，或导致了较高的海洋古生产力，从而使沉积物具有高的有机碳含量；在30-13ka BP期间，沉积物红度较高，陆源的营养物质较多，导致总有机碳水平较高。但大量的陆源砂质物质输入，，导致了碳酸盐/石英比值较低；13ka BP以来，末次冰期结束，全球进入末次冰期后期，气温逐渐增高，冰川融化，降水增多，海平面增高，陆源营养物质增多，导致沉积红度增高、有机质含量增加。同时海平面增高，大堡礁海域水深增加，水动力水平较低，利于碳酸盐沉淀、不利于石英等陆源物质运移，导致该处的碳酸盐/石英比值增高。上述研究结果为全面评价近15万年以来大堡礁海域气候环境变化提供了数据基础。
[Abstract]:The problem of climate change and its impact on human living environment is very important for human survival and development. The history of the last glacial to interglacial Southern Hemisphere low latitude ocean sea level and climate change can be predicted. It is of great significance to reveal the late Quaternary Antarctic ice sheet changes and the resulting global climate and environmental changes, and the relevant studies are very limited. In this paper, the mineralogical and geochemical characteristics of the sedimentary core column of the IODP325 voyage are studied and compared with the paleoclimate stage of the Vostok ice core in Antarctica. A comprehensive analysis method is used. It includes: unbalanced uranium series U-Thage dating method, X-ray powder diffraction method, total carbon, total inorganic carbon and total organic carbon content analysis, sediment spectrum analysis (brightness, redness and yellowness). The results show that. Sea level changes in the Great Barrier Reef, Australia, are sensitive to changes in the Antarctic ice sheet. The sedimentary core column studied covers a period of 150,000 years: 140-116 ka BP. During the warm period before the last ice age, the glacier melted, the sea level was higher, and the redness of the sediment increased, which indicated that the temperature of the Great Barrier Reef and the coastal area was higher, and the rainfall and the runoff into the sea caused by it were larger. The amount of quartz and other minerals entering the sea also increased, forming a lower carbonate / quartz content ratio. With the global climate entering the last glacial period, although there are also some changes in cold and warm, the sea level in the Great Barrier Reef is lower. During the period of 116-73 ka BP, the red degree of sediment is lower and the input of land source is less. The marine paleoproductivity in the Great Barrier Reef is low, which leads to the low content of organic matter in the sediments. During the period of 73-58ka BP, the coast of the Great Barrier Reef was cold dry and the sea level was lower. During this period, the M0058A sedimentary core was mainly composed of sand. During the period of 58-30ka BP, the Great Barrier Reef area had more rainfall and wetter climate, but the carbonate / quartz content ratio was lower, and there were more terrestrial inputs, which may lead to higher marine paleoproductivity. Thus, the sediment has a high organic carbon content; During the period of 30-13ka BP, the red degree of sediment is higher and the nutrient content of terrestrial source is more, which leads to the higher level of total organic carbon, but a large amount of terrestrial sand material input, which results in lower carbonate / quartz ratio. Since 13ka BP, the end of the last glacial epoch and the end of the last glacial epoch, the temperature gradually increased, the glacier melted, the precipitation increased, the sea level increased, and the nutrition of land source increased, which led to the increase of sedimentation red degree. At the same time, the sea level increases, the water depth in the Great Barrier Reef increases, and the hydrodynamic level is lower, which is conducive to carbonate precipitation and is not conducive to the migration of continental materials such as quartz. These results provide a data basis for the comprehensive evaluation of climate and environmental changes in the Great Barrier Reef area in the past 150,000 years.
【学位授予单位】：中国地质大学（北京）
【学位级别】：博士
【学位授予年份】：2014
【分类号】：P532;P736.21

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