藏南邛多江盆地末次冰期以来的气候记录

发布时间：2018-10-26 20:28

【摘要】：古气候学由于对现代气候环境变化具有独特的研究参考价值,在近年来成为当代地质科学中的热点话题。在众多保存气候信息的沉积载体中,湖泊沉积物因其具有分布范围广、受局限条件相对较少、沉积连续稳定、分辨率高以及易提取等特点,在气候和环境变化研究中具有其独特的一面,并且在青藏高原古气候研究中广泛运用。通过研究高原湖泊沉积物中的气候代用指标,对于研究青藏高原气候变化,特别是高原的形成对于亚洲季风系统的影响,以及认识引起气候变化的控制因素和动力机制具有重要研究价值。因此,本文通过提取邛多江盆地湖相沉积物中的粒度、TOC含量、TOC/TN比值和δ13Corg等代用指标,在AMS14C年代学框架基础之上,分析研究区的古气候演变史,并通过与全球其他区域诸如季风区石笋氧同位素记录、北大西洋海表温度、太阳辐射量变化等对比,对驱动气候变化的动力机制进行初步探讨,并得出如下结论:1、利用AMS14C测年,获得邛多江盆地湖相沉积物剖面顶部年龄为30.3 k a BP,底部年龄约为40.2 ka BP。2、通过对各代用指标的分析,将邛多江盆地40~30 ka BP古气候变化特征分为如下几个阶段:气候暖湿期(40.2~38.5 ka BP)、气候温干期(38.5~35.4 k a BP)、气候过渡期(35.4~32.4 ka BP)、气候动荡期(32.4~31.7 ka BP)和气候转干期(31.7~30.3 ka BP)。通过代用指标分析,我们发现40~30 ka期间邛多江盆地可能存在有几次明显的气候事件,诸如39.3 ka短暂干旱事件、35 ka降水增强事件等。3、通过对邛多江盆地湖相沉积物剖面中有机碳同位素变化特征分析,除温度和降水量两个影响因素外,大气中CO2浓度可能也是导致该剖面有机碳同位素变化的原因之一。4、结合邛多江盆地沉积物有机碳同位素变化特征,发现其与全球其他区域具有明显的响应关系,并且在频谱分析中识别出1552 a、1187 a、961 a和602a,这一系列周期良好地对应了D/O旋回中1.5 ka和1 ka的周期,而602 a、538 a以及492 a对应的可能是1000 a的半谐周期。5、在与主要受到东亚季风控制的南京葫芦洞石笋氧同位素变化曲线对比时发现,二者存在比较不协同的气候变化关系,初步认为是因为两个区域是受到了不同的季风控制导致了这种差异。对比各区域气候记录后,发现盆地气候控制主要是受到西南季风的影响,而与东亚季风存在弱相关性,这在与桂林响水洞石笋氧同位素研究中具有良好的对比性。此外,通过与北大西洋深海沉积物气候记录所反映的气候事件对比,发现具有良好的对应性,说明可能是受到温盐环流的因素驱动。然而,考虑到高原的特殊地理位置和大地地貌、构造等因素,认为温盐环流和高原自身是影响邛多江盆地湖相沉积物气候参数变化的两个重要因素。6、结合40~30 ka BP以来的30°N和30°S的太阳辐射量变化,初步认为是由于受到太阳辐射量改变从而引起的气候与环境的改变,并且认为在32 ka BP左右由于南北纬太阳辐射量的差异变化,可能是导致邛多江盆地出现气候急剧动荡的主要原因之一。
[Abstract]:As a reference value to the change of modern climate environment, paleoclimatology has become a hot topic in contemporary geological science in recent years. in the deposit carrier for storing the climate information, the lake sediments have the characteristics of wide distribution range, relatively few limited conditions, continuous and stable deposition, high resolution and easy extraction and the like, and have a unique side in the research of climate and environment change, And it is widely used in the study of paleoclimate in the Qinghai-Tibet Plateau. By studying the climate substitute index in plateau lake sediments, it is of great value to study the effect of climate change on the Qinghai-Tibet Plateau, especially the formation of plateau on the Asian monsoon system, as well as the control factors and dynamic mechanisms that cause climate change. Therefore, the paleoclimate evolution history of the study area is analyzed by extracting the particle size, TOC content, TOC/ TN ratio and AMS13Corg in the lake facies sediment of the Songhuangjiang Basin, and the paleoclimate history of the study area is analyzed and recorded by the oxygen isotope in other regions of the world, such as the monsoon region. Based on the comparison of the temperature of the North Atlantic Ocean and the change of solar radiation, the dynamic mechanism of driving the climate change is discussed preliminarily, and the following conclusions are obtained: 1. By using AMS14C dating, the top age of the lake facies sediment section of the Longyangjiang basin is 30. 3k a BP, and the bottom is about 40. 2ka BP. 2. According to the analysis of each substitute index, the paleoclimatic change of 40 ~ 30ka BP in the basin is divided into the following stages: climate warm-wet stage (40. 2 ~ 38. 5 ka BP), climate warm dry stage (38. 5 ~ 35. 4k a BP), climate transition period (35. 4 ~ 32. 4 ka BP). Climatic fluctuation period (32. 4 ~ 31. 7 ka BP) and dry climate (31. 7 ~ 30. 3 ka BP). Through alternative index analysis, we find that there may be several obvious climatic events, such as 39. 3ka short drought events, 35 ka precipitation enhancement events, etc. during the period of 40 ~ 30ka. in addition to that two influence factors of temperature and precipitation, the CO2 concentration in the atmosphere may also be one of the cause of the change of organic carbon isotope in the section. and 1552a, 1187a, 961a, and 602a are identified in the spectral analysis, this series of cycles well corresponds to the period of 1. 5 ka and 1 ka in the d/ o cycle, while 602a, 538a and 492a correspond to a half-harmonic period of 1000a. 5, It is found that the two regions are affected by different monsoon controls because the two regions are affected by different monsoon controls. After comparing the regional climate records, it is found that the climate control of the basin is mainly influenced by the southwest monsoon, but there is a weak correlation with the East Asian monsoon. In addition, by contrast to climate events reflected in the North Atlantic deep-sea sediment climate record, it has been found that a good correspondence may be driven by factors that are subject to warm-salt circulation. However, considering the special geographical position and geomorphology and structure of plateau, it is considered that the temperature and salt circulation and plateau itself are two important factors that affect the change of climate parameters in the lake facies sediments of the Yangtze River basin, and the solar radiation changes of 30 掳 N and 30 掳 S since 40 ~ 30 ka BP are combined. It is considered that the change of climate and environment caused by the change of the amount of solar radiation is one of the main causes of the abrupt climate change in the Erdojiang basin due to the difference in the amount of solar radiation in the north-south latitude about 32ka BP.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P532

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