末次冰消期以来青海湖地区风成沉积记录的环境演变

发布时间：2018-05-15 04:43

本文选题：青海湖 + 环境演变　；参考：《青海师范大学》2015年硕士论文

【摘要】：青藏高原是“全球气候变化的驱动机和放大器”,是“全球变化与地球系统科学统一研究的最佳天然实验室”。位于青藏高原东北部的青海湖地区,地处东南季风、印度季风和西风带的交互地带,同时也是西部干旱区、东部季风区、青藏高寒区三大区域的交汇地带,对气候变化异常敏感,是研究第四纪古气候环境演变的理想地区。长期以来,青藏高原第四纪研究工作多集中于青藏高原湖泊沉积物,然而由于高原湖泊古环境研究的复杂性,从而导致对过去环境演变的理解可能存在不确定性。因此,利用其他环境信息载体进行古环境古气候重建,进而与湖泊沉积物进行相互补充和验证,从而准确重建高原晚第四纪以来的环境变化。广泛分布于青藏高原的风成沉积是第四纪研究的重点研究对象。本文在青海湖南岸和西岸选取JXG-1、JXG-2和SNH三个黄土-古土壤剖面,在地层学、年代学(光释光测年、热释光测年和14C测年)的基础上,结合粒度、磁化率、色度、地球化学元素等多种环境代用指标,分析探究了末次冰消期以来青海湖地区风成沉积记录的环境演变,重点研究了2μm组分、63 μm组分、红度、磁化率、元素等环境代用指标。三个剖面较为一致地记录了青海湖区自末次冰消期以来经历3次较为显著的气候变化：末次冰消期～12 ka,青海湖区环境总体干冷,剖面主要沉积风成砂和砂质黄土,沉积速率快；12-5 ka左右,青海湖区气候呈暖湿状态,剖面主要发育古土壤,沉积速率最小；5-2 ka,亮度、有机质、磁化率、元素均呈先递减后增加趋势,总体上由暖湿向凉干过渡,气候变动大；2 ka～今,气候向干旱化方向发展。通过不同的古环境感应体之间的对比发现,本文三个剖面的红度、黄度值与相距仅50 km左右的湖泊钻孔QH 2000的变化趋势相似。产生上述情况的原因可能是暖湿期风力弱、植被盖度高、尘暴强度低,红色围岩母质(二长花岗岩)输入相对较少,从而导致古土壤中红度值较低；干冷期风力强、植被盖度低、尘暴频繁,红色物质输入量较多,从而引起黄土中红度较高。
[Abstract]:The Qinghai-Tibet Plateau is the "driving and amplifier of global climate change" and "the best natural laboratory for the scientific research of global change and earth system". The Qinghai Lake region, located in the northeast of the Qinghai-Xizang Plateau, is located at the intersection of the southeast monsoon, the Indian monsoon and the westerly belt, as well as the western arid region, the eastern monsoon region, and the Qinghai-Tibet high and cold region. It is an ideal area to study the evolution of Quaternary paleoclimate environment. For a long time, the Quaternary study of Qinghai-Xizang Plateau has focused on lake sediments of Qinghai-Xizang Plateau. However, due to the complexity of paleoenvironmental research on plateau lakes, the understanding of past environmental evolution may be uncertain. Therefore, paleo-paleoclimate reconstruction is carried out by using other environmental information carriers, and then the paleoclimate is complemented and verified with lake sediments, so as to accurately reconstruct the environmental changes in the plateau since the late Quaternary. The aeolian deposits widely distributed in the Qinghai-Xizang Plateau are the focus of Quaternary study. In this paper, three loess paleosol profiles, JXG-1, JXG-2 and SNH, are selected on the south coast and west coast of Qinghai Lake. On the basis of stratigraphy, chronology (photoluminescence dating, thermoluminescence dating and 14C dating), granularity, magnetization, chromaticity are combined. The environmental evolution of eolian deposition records in Qinghai Lake area since the last ice extinction period was analyzed and explored, with emphasis on the environmental substitution indexes of 63 渭 m component of 2 渭 m component, redness, magnetic susceptibility, element and so on. The three sections consistently recorded three significant climatic changes in Qinghai Lake area since the last ice extinction period: the last ice extinction period was 12 ka, the environment in Qinghai Lake region was generally dry and cold, and the profile was mainly composed of sedimentary eolian sand and sandy loess. The deposition rate is about 12-5 ka. The climate of Qinghai Lake region is warm and wet, and paleosols are mainly developed in Qinghai Lake area. The deposition rate is the minimum of 5-2 ka. brightness, organic matter, magnetic susceptibility and elements decrease first and then increase, and generally transition from warm and wet to cool and dry. The climate change is 2 ka ~ now, the climate develops to the direction of drought. By comparing different paleoenvironmental inductors, it is found that the red degree and yellow value of the three sections are similar to the variation trend of QH 2000 in the lake borehole about 50 km apart. The reasons for the above may be weak wind force in warm and wet period, high vegetation coverage, low dust storm intensity, relatively low input of red surrounding rock parent material (bifeldite), resulting in lower value of red degree in paleosol, and strong wind power in dry and cold period. The vegetation coverage is low, dust storm is frequent, and red matter input is more, which results in higher red degree in loess.
【学位授予单位】：青海师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532

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