中新世以来奄美三角盆地碎屑沉积物粒度特征及其物源和古气候意义

发布时间：2018-04-23 10:04

本文选题：奄美三角盆地 + 中新世　；参考：《中国科学院研究生院(海洋研究所)》2016年硕士论文

【摘要】：亚洲干旱区来源的风尘是西北太平洋深海沉积物的重要组成部分,同时也是研究亚洲大陆古气候的重要载体。西北太平洋深海沉积物中的风尘不仅记录了风尘源区——亚洲大陆的干/湿状况及大气环流强弱,而且在全球气候与环境演变的过程中具有重要作用。奄美三角盆地位于菲律宾海西北部,海底地形较为平坦,缺乏大规模的洋流活动,中新世以来沉积记录连续。同时,奄美三角盆地位于西风带和东亚季风区内,季风影响十分明显,因而奄美三角盆地是研究风尘记录及其所蕴含古气候意义的理想场所。深海沉积物的粒度组成是重要的物源和古气候示踪指标。根据特征粒度频率分布曲线可以识别深海沉积物中风尘组分及其来源,而提取出的风尘组分的粒径大小则可以指示风力强弱。本文对“国际大洋发现计划”(IODP)351航次在菲律宾海西北部奄美三角盆地采集的U1438A孔和U1438B孔中新世以来沉积物中碎屑组分的粒度组成进行了分析,用Weibull函数分离方法对碎屑沉积物粒度频率分布曲线进行不同端元组分的分离,获得了各个端元组分的相对含量,并分析了各端元组分的来源。用主成分分析法(PCA)、粒径-标准偏差法两种方法提取了碎屑组分中对环境敏感的粒级组分,并与古气候代用指标进行对比研究。通过上述研究,探讨了亚洲大陆风尘向奄美三角盆地的输入历史,以及不同敏感粒级组分在构造和轨道尺度对亚洲内陆干/湿状况及其大气环流模式的响应。奄美三角盆地U1438A和U1438B孔碎屑组分粒度分析结果表明,其粒度频率分布曲线总体上呈现四峰态分布特征。U1438A孔约350ka以来沉积物中碎屑组分的平均粒径为13.1μm,粒径变化范围为0.04~160μm。砂、粉砂和黏土的平均含量分别为1.5%、74.7%和23.8%。利用Weibull分布函数对实测数据进行拟合分离出四个独立组分:(1)众数为0.25μm的超细粒组分,粒径变化范围0.04-0.9μm,平均含量为0.96%,代表海洋自生粘土物质;(2)众数约3.5μm的细粒组分,粒径变化范围0.2-32μm,平均含量为29.2%,代表亚洲大陆来源的风尘物质;(3)众数约10μm的粗粒组分,粒径变化范围0.3-90μm,平均含量为54.4%;(4)众数约40μm的超粗粒组分,粒径变化范围3-160μm,平均含量为15.5%。粗粒和超粗粒组分主要来自奄美三角盆地周围的海脊和火山岛弧物质。U1438B孔约25Ma以来沉积物碎屑组分的平均粒径为14.8μm,粒径变化范围在0.04-160μm之间。砂含量平均3.3%,粉砂含量平均72%,粘土含量平均24.7%。用Weibull分布函数对粒度数据进行拟合,结果与U1438A孔类似。(1)众数为0.25μm的超细粒组分,粒径变化范围0.04-0.9μm,平均含量为1.1%,推测来源于海洋自生粘土;(2)粒度众数约3.5μm的细粒组分,粒径变化范围0.2-32μm平均含量为29.5%,主要来自于亚洲大陆风尘;(3)粒度众数约10.3μm的粗粒组分,粒径变化范围0.3-90μm,平均含量为60.3%;(4)粒度众数约32.5μm的超粗粒组分,粒径变化范围3-160μm,平均含量为9.1%。粗粒组分和超粗粒组分主要来自于奄美三角盆地周围海脊和岛弧的火山物质。根据U1438B孔粒度参数1.8-6μm/14-22μm、0.9-3μm/10μm以及细粒组分含量在垂向上的变化,将亚洲大陆风尘向奄美三角盆地的输入变化分为六个阶段:(1)25.8~23Ma,细粒风尘组分含量较高,粗粒组分相对较低。(2)23-17.3Ma,细粒风尘组风呈逐渐增加的趋势,而粗粒火山组分成逐渐减小的趋势。(3)17.3~13.8Ma,细粒风尘组分含量明显增加,而粗粒的火山组分明显降低。(4)13.8~9Ma,细粒风尘组分降低,粗粒火山组分增加。(5)9-2.5Ma,细粒风尘组分明显增加,而粗粒火山组分明显降低。(6)2.5Ma至今,风尘组分与火山组分均出现明显的波动。中新世以来,风尘组分的变化在构造尺度上响应了喜马拉雅-青藏高原的抬升和全球冰量增加所驱动的亚洲大陆干旱化加剧,以及东亚大气环流系统的增强。在轨道时间尺度上,U1438A孔碎屑组分粒度参数1.3~2.2μm/28~40μm、0.9~3μm/10μm表现为冰期高、间冰期低,与北太平洋风尘通量、亚洲大陆黄土堆积速率,以及黄土粒径所指示的冰期干旱和东亚季风/西风环流增强的气候变化一致,表明冰期由于亚洲大陆的干旱和季风/西风的增强,使得奄美三角盆地中细粒亚洲风尘组分的输入相对增加。因此细粒风尘和粗粒火山物质的比值可以作为亚洲大陆干旱化和大气环流增强的示踪指标。这些研究结果表明,奄美三角盆地沉积物的粒度组成可用于重建中新世以来东亚大陆干旱和大气环流演化历史。
[Abstract]:The wind dust derived from the Asian arid region is an important component of the deep-sea sediments in the Northwest Pacific, and is also an important carrier for the study of the paleoclimate of the Asian continent. The wind dust in the deep-sea sediments of the Northwest Pacific not only records the dry / wet conditions of the Asian continent and the strong and weak circulation of the atmosphere in the Asian continent, but also in the global climate and environment. The mamam basin is located in the north of Philippines and is located in the northern West of Haixi. The seabed topography is relatively flat, lack of large-scale ocean current activities and continuous sedimentary records since the Miocene. At the same time, the Mamo triangle basin is located in the west wind zone and East Asian monsoon region, the monsoon influence is very obvious, so the mamm basin is the study of the dust. The grain size composition of the deep sea sediments is an important source of material and paleoclimate tracers. According to the frequency distribution curve of the characteristic grain size, the composition and source of the wind dust in the deep sea sediments can be identified, and the size of the extracted wind dust can indicate the strength of the wind. The granularity composition of the debris components in the sediments of the U1438A and U1438B pores in the northern Philippines delta basin, Philippines, was analyzed by the 351 voyage of oceanic discovery program. The separation of different end components of the grain frequency distribution curve of debris sediments was obtained by the Weibull function separation method. The relative content of the end tuples and the sources of each end tuple are analyzed. Two methods are extracted by the principal component analysis (PCA) and the particle size standard deviation method to extract the environmental sensitive grain grade components in the debris components, and compare with the paleoclimate substitute index. The input history, and the response of different sensitive grain fractions to the Asian inland dry / wet conditions and their atmospheric circulation patterns at the tectonic and orbital scales. The results of the grain size analysis of the U1438A and U1438B detritus in the amore delta basin show that the distribution of the grain size frequency distribution curve presents the four peak distribution characteristics of the.U1438A pore since 350kA. The average particle size of the debris is 13.1 mu m, the size of the particle size is 0.04~160 mu m. sand, the average content of the silt and clay is 1.5%, 74.7% and 23.8%. are fitted and separated by the Weibull distribution function to fit and separate the measured data. (1) the ultra-fine grain components of 0.25 mu m, the particle size variation range 0.04-0.9 mu m, the average content 0.96%, representing the marine authigenic clay substance; (2) the fine-grained components of about 3.5 mu m, the particle size variation range 0.2-32 mu m, the average content of 29.2%, representing the Asiatic origin of the dust; (3) the coarse-grained components of the 10 mu m, 0.3-90 mu m, the average content of 54.4%; (4) the size variation range of about 40 mu m. 3-160 mu m, the average content of 15.5%. coarse grain and super coarse grain component mainly comes from the ridge of the near amore triangle basin and the volcanic island arc material.U1438B pore, the average particle size of the debris component is 14.8 mu m since 25Ma. The grain size varies between 0.04-160 and M. The average sand content is 3.3%, the content of silt is 72%, and the average clay content 24.7%. uses W. The eibull distribution function fitted the granularity data, and the result was similar to that of the U1438A hole. (1) the ultra fine grain components of 0.25 mu m, the size of the particle size was 0.04-0.9 mu m, the average content was 1.1%, and it was deduced from the marine authigenic clay; (2) the fine grain component of the particle size of 3.5 mu m, and the average content of 0.2-32 u m of the particle size range was 29.5%, mainly from sub The continental aeolian dust; (3) the coarse-grained components of the particle size of 10.3 mu m, the size of the particle size variation range 0.3-90 m, the average content of 60.3%; (4) the grain size of the ultra coarse grains of about 32.5 mu m, the size of the particle size variation range 3-160 Mu m, the average content of the coarse-grained components and the super coarse-grained components is mainly derived from the volcanic materials of the ridge and island arc around the amore delta basin. According to the variation of the size of the U1438B pore size 1.8-6 m/14-22 mu, 0.9-3, m/10, m and the content of fine particles in the vertical, the input changes of the Asian continental dust to the amolrant delta basin are divided into six stages: (1) 25.8~23Ma, the content of the fine particulate air dust is higher, the phase pair of the coarse grain group is lower. (2) 23-17.3Ma, and the fine wind dust group gradually increases. Trend, and the coarse-grained volcano group gradually decreased. (3) 17.3~13.8Ma, the content of fine particles increased obviously, and the volcanic component of coarse grain decreased obviously. (4) 13.8~9Ma, the fine particle dust composition decreased, the coarse-grained volcanic component increased. (5) 9-2.5Ma, the fine grain dust composition increased obviously, and the coarse grain volcanic component obviously decreased. (6) 2.5Ma so far, wind The changes of dust components and volcanic components have obvious fluctuations. Since the Miocene, the changes of the wind dust composition have responded to the uplifting of the Himalaya Qinghai Tibet Plateau and the increase of the global ice in the Asian continent, as well as the enhancement of the atmospheric circulation system in East Asia. On the orbital time scale, the U1438A pore fragments are divided into particles. The degree parameter 1.3~2.2 mu m/28~40 mu m and 0.9~3 mu m/10 mu m are high in ice age and low in interglacial period. It is consistent with the North Pacific wind dust flux, the loess accumulation rate in the Asian continent, the glacial drought indicated by the loess grain size and the East Asian monsoon / westerly circulation enhanced climate change, indicating that the ice period is due to the drought in the Asian continent and the increase of the monsoon / westerly wind in the Asian continent, The input of fine-grained Asiatic dust components in the triangulation basin is increased relatively, so the ratio of fine and coarse-grained volcanic materials can be used as a tracer indicator for the aridity of the Asian continent and the enhancement of atmospheric circulation. These results show that the grain size composition of the sediments in the amore delta basin can be used for the reconstruction of East Asia since the Miocene. The history of land drought and the evolution of atmospheric circulation.

【学位授予单位】：中国科学院研究生院(海洋研究所)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P532;P534.621

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