贵州威宁草海地区早更新世晚期湖相地层ESR定年及环境意义

发布时间：2018-03-20 03:20

本文选题：草海　切入点：早更新世　出处：《华东师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：人类出现在第四纪并且在这一时期快速发展,因此进行第四纪研究具有十分重要的意义。一般来说,在较小的时间尺度下研究环境演变,就需要更准确、分辨率更高的测年手段。不同测年方法存在不同的优点和局限性,而电子自旋共振测年法以其测年范围广几乎涵盖整个第四纪而被广泛应用。草海盆地是典型的构造岩溶盆地,地处云贵高原东部。其沉积物来源于周围山体,加上没有远源河流,记录着盆地的演化。因此,它是研究云贵高原东缘第四纪演化的一个不可多得的场所。本研究以贵州威宁草海地区湖相地层的陈选屯剖面为研究对象,进行电子自旋共振定年确定沉积年代,结合青藏高原隆升史以及分析色度、粒度、磁性参数和地球化学元素等环境代用指标含量和纵向分布特征,对草海的古环境特征和演化进行初步推测和还原。研究主要得出以下结论：(1)草海湖相沉积地层的ESR测年结果显示为距今1.16-1.871Ma,与之前的古地磁测定结果相比更为准确。测年结果对应时代为早更新世的青藏运动C幕,此时草海仍受西南季风影响,推测为温暖湿润气候。(2)草海湖相沉积地层的色度结果表明,L*(亮度值)较高,a*(红度值)和b*(黄度值)较低。据此可以推测,草海当时的是一个温度较低,气候温暖湿润,以还原作用为主的一个深湖环境。(3)草海湖相地层粒度结果显示,其粒度分布相对集中,以粒径较小的粘土和细粉砂为主,剖面整体分选较差。故指示古环境为河流或湖泊,且应处于较为湿润的高水位时期。(4)草海湖相地层磁性结果表明,剖面的频率磁化率和剩磁均指示其暖湿的古环境。然而,磁化率指示其干冷的古环境。研究表明,物质的磁化率不一定能完整地反映它在真实环境中的全部磁学特性,存在环境信息丢失的状况。本研究不考虑磁化率的指示结果。因此,磁性参数指示是暖湿古环境,与色度及粒度一致。(5)草海湖相地层的元素地球化学特征选取B、Sr、Mg/Al、Sr/Ba、Sr/Cu、B/Ga进行多指标古环境分析。结果均显示其形成时为气候温湿的深湖沉积环境。(6)ESR测年结果显示的气候特征与环境代用指标指示的气候特征基本吻合,说明ESR定年较为准确具有一定的科学参考价值。
[Abstract]:Humans appeared in the Quaternary and developed rapidly during this period, so Quaternary research is of great significance. Generally speaking, it is more accurate to study the evolution of the environment at a relatively small time scale. Different dating methods have different advantages and limitations, while electron spin resonance dating method is widely used because of its wide range of dating covering the entire Quaternary. The Caohai Basin is a typical tectonic karst basin. It is located in the eastern part of the Yungui Plateau. Its sediment originates from the surrounding mountains and there are no distant rivers, which records the evolution of the basin. It is a rare place to study the Quaternary evolution of the eastern margin of the Yunnan-Guizhou Plateau. In this study, the Chen Xiantun section of the lacustrine strata in the Huining Caohai area, Guizhou Province, was used as an object of study to determine the sedimentary age by means of electron spin resonance dating. In combination with the uplift history of the Qinghai-Tibet Plateau and the analysis of the contents and longitudinal distribution characteristics of environmental substitution indexes such as chroma, granularity, magnetic parameters and geochemical elements, In this paper, the paleoenvironmental characteristics and evolution of the Caohai are preliminarily inferred and reduced. The main conclusions are as follows: 1: 1) the ESR dating of the Caohai lacustrine sedimentary strata is 1.16-1.871 Ma, which is more accurate than the previous paleomagnetic measurements. The dating results correspond to the early Pleistocene Qinghai-Tibet movement, At this time, Caohai is still affected by the southwest monsoon, which is supposed to be a warm and humid climate. 2) the chrominance of Caohai lacustrine sedimentary strata shows that the luminance values are higher in the Caohai Lake than the red ones (redness values) and bong (yellowness values). It can be inferred that, At that time, Caohai was a deep lacustrine environment with low temperature, warm and humid climate and a deep lake environment dominated by reduction. The results showed that the granularity distribution of Caohai lacustrine facies was relatively concentrated, mainly of clay and fine silt with smaller particle size. The magnetic properties of Caohai Lake facies show that the frequency susceptibility and remanence of the section indicate its warm and wet paleoenvironment. Magnetic susceptibility indicates its dry and cold paleoenvironment. Studies have shown that the magnetic susceptibility of matter does not necessarily reflect all of its magnetic properties in real environments. There is a loss of environmental information. This study does not consider the indication of magnetic susceptibility. Therefore, the magnetic parameter indication is warm and wet paleoenvironment. Element geochemistry characteristics of Caohai lacustrine facies are analyzed by multiparameter paleoenvironment analysis using BPS-SrSr-Mg-Al / Al / Sr-ba-r-SrCu-B / Ga. The results show that the formation time of Caohai lacustrine facies is a climate special characteristic of ESR dating results of deep lake sedimentary environment with warm and wet climate. The climatic characteristics indicated by the indicator of environmental substitution are basically consistent with each other. It shows that ESR dating is more accurate and has certain scientific reference value.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.631

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