近200年来东海内陆架沉积层序高频波动模式及其对多尺度气候振荡的响应

发布时间：2018-06-20 02:14

本文选题：东海内陆架 + 高分辨沉积记录　；参考：《中国海洋大学》2014年博士论文

【摘要】：IODP计划（2013~2023）中的第一个科学主题中明确指出：海底的沉积物岩芯提供了过去气候变化的记录，能够在空间和时间尺度上更好理解地球系统演变过程，，地质记录能够帮助我们检验预测未来气候模型的准确性。东海是东亚季风、西太平洋边界流共同影响下的海域，接受来自长江、黄河以及众多中小型河流的大量陆源物质输入，具有很高的沉积速率，使得该处成为开展高分辨沉积记录及其对多尺度气候变化响应研究的重要选区。本研究以东海内陆架闽浙沿岸泥质沉积区为研究对象，开展了沉积学和地球化学的超高分辨沉积记录的综合研究，揭示了泥质沉积记录中存在的高频振荡现象和隐形沉积“年纹”，利用沉积纹层进行精细的年代标定，建立了该区域近200年来的超高分辨沉积记录模式，并与东亚季风、ENSO与PDO指数进行耦合研究，探讨沉积层序中的高频波动对年际、年代际气候振荡的响应机制。该研究结果将为东亚季风影响下的陆架区超高分辨沉积记录研究提供新的途径，并为客观评价东海内陆架海洋环境演变中的自然因素、人类活动的贡献和演变趋势提供科学依据。论文首先探索了超高分辨沉积记录的沉积学指标，即岩芯的X-ray影像灰度指标和Corescanner岩芯元素扫描指标。通过对东海内陆架表层沉积物和四根沉积物岩芯X-ray影像灰度的研究表明：1）沉积物的灰度值是沉积物密度、结构和构造等属性的综合体现,但是受沉积物中的含水量的影响明显，两者呈现出明显的负相关关系，并据此提出了灰度的含水量校正公式。经过校正后的沉积物灰度值与沉积物的粒度、砂+粉砂的百分含量有着良好的一致性，可以近似看作岩芯的粒度替代性指标；依据灰度对东海陆架沉积物进行了分区，能很好地反映了该区的沉积环境。2）对沉积物岩芯进行X-rayCorescanner连续岩芯扫描研究表明：岩芯中沉积物的含水量和干密度均对X-ray岩芯扫描元素分析结果产生影响，即为压实效应，并得到了该区压实效应的校正公式，据此可以对Corescanner结果进行压实效应的校正。评价了针对东海内陆架泥质沉积区X-ray core scanner元素测试能力，将其分成四类，其中I类元素分析结果可信度高、可以直接作为含量对待，II类具有重要的参考价值，III类具有一定参考价值，而IV类无参考价值。对取自东海内陆架的4根岩芯18、C0702、DH6-1、DH7-2，系统地开展了沉积物岩芯的X-ray影像灰度、岩芯Corescanner元素扫描、粒度分析以及放射性同位素测定，建立了东海内陆架近200年来高分辨沉积记录。通过经验模态分解-最大熵谱分析法(EMD-MESA)及功率谱分析等方法对高分辨沉积记录进行了周期性分析，识别了该区域存在的隐形年纹或年代纹；利用沉积纹层定年并经210Pb、137Cs测年验证，建立起了该区域内近200年来高精度的年代标尺，揭示了该研究区内沉积层序三种高频波动模式：(i)年内及年尺度准周期变化；(ii)年际尺度的准周期变化(~2-8年)；(iii)年代际尺度准周期变化。不同位置的沉积岩芯的高频波动模式略有差别。将东海内陆架沉积层序的高频波动模式与东亚季风、ENSO及PDO指数进行耦合研究，结果表明岩芯18存在的年内及年尺度准周期变化是长江输沙量的周期性变化的结果，其余三根岩芯C0702、DH6-1及DH7-2中沉积记录中高频波动的准两年周期与东亚季风的准2年周期变化有着显著的关系；四根岩芯中沉积记录的年际高频波动与ENSO的(2~8年)周期有着良好的响应关系，该周期性波动是由ENSO振荡影响了东亚冬季风的强度、进而改变了该区的海洋沉积动力环境和沉积物搬运沉积过程所产生；该区沉积记录中的年代际的波动与PDO指数变化有着良好的响应关系，分析认为是PDO相位发生转变时引起东亚大陆的表层风发生异常，并导致东亚冬季风强度发生变化，进而影响了该区的沉积动力环境和沉积过程，最终导致了沉积层序中的年代际周期的形成。
[Abstract]:The first scientific theme in the IODP program (2013~2023) clearly points out that the sediment cores from the sea floor provide a record of the past climate change, which can better understand the evolution of the earth's system in space and time, and the geological record can help us test the accuracy of the prediction of future climate models. The sea area under the common influence of the flat ocean boundary flows, receiving a large amount of terrestrial material input from the Yangtze, the Yellow River and many small and medium rivers, has a high deposition rate, making it an important selected area for the study of high resolution sedimentary records and their response to multi-scale climate change. The integrated study of sedimentary and geochemistry of ultrahigh resolution sedimentary records has been carried out. The high frequency oscillations and the "annual lines" of the stealth deposits in the sedimentary records are revealed, and the fine dating of the sedimentary layers is used to establish the ultra high resolution sedimentary record model for the region in the past 200 years. The East Asian monsoon, coupled with the ENSO and PDO index, explores the response mechanism of high frequency fluctuations to interannual and Interdecadal Climatic Oscillations in sedimentary sequences. The results will provide a new way for the study of ultrahigh resolution sedimentary records in the continental shelf area under the influence of East Asian monsoon, and to objectively evaluate the nature of the marine environment evolution in the inland shelf of the East China Sea. Factors provide a scientific basis for the contribution and evolution of human activities.
In this paper, the sedimentological indexes of ultrahigh resolution sedimentary records are first explored, that is, the gray index of X-ray image and the scanning index of Corescanner core elements in the core. Through the study of the X-ray image grayscale of the surface sediments of the East China Sea and the X-ray image of the core of the sediments, 1) the gray value of the sediments is the density, structure and structure of the sediments. There is a clear negative correlation between the water content in the sediment and the obvious negative correlation between the water content in the sediment, and the gray level water content correction formula is put forward accordingly. The corrected sediment grayscale value has good consistency with the grain size of the sediment and the content of sand and silt. It can be considered approximately as the grain size of the core. The subregion of the sediments in the East China Sea shelf is subdivided according to the gray level, which can well reflect the sedimentary environment.2 in the area. The study of X-rayCorescanner continuous core scanning for the sediment core shows that the water content and dry density of the sediments in the core are all influenced by the results of the analysis of the X-ray core scanning elements, that is, the pressure effect is effective. The correction formula for the compaction effect of the area can be obtained. According to this, the compaction effect of Corescanner results can be corrected. The testing ability of the X-ray core scanner element in the muddy sediment area of the East China Sea is evaluated and divided into four categories, in which the analysis results of I elements are highly credible and can be treated directly as content, and II classes have heavy weight. The reference value of the III class has certain reference value, while the IV class has no reference value.
4 cores from the inland shelf of the East China Sea, 18, C0702, DH6-1, DH7-2, have systematically carried out the X-ray image gray level of the sediment core, the core Corescanner element scanning, the particle size analysis and the radioisotope determination. The high resolution sedimentary records of the East China Sea continental shelf for nearly 200 years have been established. The empirical mode decomposition maximum entropy spectrum analysis (EMD-MESA) has been established. With the method of power spectrum analysis, the periodic analysis of high resolution sedimentary records is carried out, and the stealth annual or chronology of the region is identified. By using the sedimentary layer for dating and verifying by 210Pb, 137Cs dating, the high precision chronology ruler in the region for nearly 200 years has been established, and three high-frequency fluctuations in the sedimentary sequence in this study area have been revealed. Model: (I) the annual and annual scale quasi periodic changes; (II) the interannual scale quasi periodic change (~2-8); (III) the interdecadal scale quasi periodic changes. The high-frequency fluctuation patterns of the sedimentary cores at different positions are slightly different.
The high frequency fluctuation model of the sedimentary sequence of the East China Sea continental shelf is coupled with the East Asian monsoon, ENSO and PDO index. The results show that the annual and annual quasi periodic changes of the core 18 are the result of the periodic variation of the sediment transport in the Yangtze River, and the quasi Biennial period of the high frequency fluctuation in the other three core cores C0702, DH6-1 and DH7-2. There is a significant relationship between the quasi 2 year periodic changes in the East Asian monsoon; the interannual high-frequency fluctuation recorded in the four cores has a good response relationship with the ENSO (2~8 year) cycle. The periodic fluctuation affects the East Asian winter monsoon intensity by the ENSO oscillation, and then changes the marine sedimentary dynamic environment and sediment transport deposition in this area. The interdecadal fluctuations in the depositional records of the region have a good response to the changes in the PDO index. It is believed that the change of the surface wind in the East Asian continent is caused by the transition of the PDO phase, which leads to the change in the East Asian winter wind intensity, and then affects the sedimentary dynamic environment and the deposition process in the region, and ultimately leads to the guidance of the sedimentary process. The formation of the interdecadal cycle in the depositional sequence is caused.
【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：P736.2

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