昆仑山北坡黄土记录的末次冰消期以来塔里木盆地环境变化历史
发布时间：2018-11-20 05:47
【摘要】：昆仑山北坡黄土是塔克拉玛干沙漠的同源异相沉积,连续完整得记录了塔里木盆地内气候演化的历史。研究昆仑山黄土记录的气候信息,不仅能够重建塔里木盆地内更长尺度以来的环境变化历史,还有助于我们进一步理解盆地内环流的演化和干旱化的驱动机制；盆地内的绿洲发展也同样受制于气候的变化,恢复塔里木盆地内过去的古环境记录,能够为绿洲的可持续发展提供建议。本文通过对昆仑山北坡的普鲁黄土进行详细的环境磁学、粒度以及化学元素的分析,尝试对黄土记录的气候信息加以解释。普鲁剖面黄土的环境磁学与磁性矿物的微观形态分析表明成壤作用微弱,磁性矿物以原生为主,主要反映了源区粉尘的磁学特征；粒度分析指示普鲁剖面黄土颗粒较粗,是塔克拉玛干沙漠的近源沉积；地球化学元素分析表明黄土沉积后元素的淋溶作用很弱,主要反映了源区粉尘的化学性质。不同的气候代用指标均一致的反映出,昆仑山北坡黄土在沉积之后再次改造作用微弱,主要反映了源区,即塔里木盆地内物质的理化特征,因此利用普鲁剖面黄土记录能够重建塔里木盆地内的古环境变化。本文通过普鲁剖面光释光年代结果和粒度年代模型建立普鲁剖面17500a BP年以来的年代框架,并结合环境磁学、粒度和地球化学元素等古气候代用指标,初步讨论了昆仑山北坡黄土记录的塔里木盆地17500a BP以来的古环境变化历史。根据粒度年代模型,普鲁黄土剖面29m以上应为末次消期以来沉积,CaCO3含量与粒度组分含量变化均指示了在17000a BP之前塔里木盆地内是明显的干旱期,而17000-14000a BP之间出现明显的湿润阶段,即塔里木盆地在全新世之前的一段湿润时期,具体的气候事件分析仍需要年代支持；在14000-9600a BP之间,即末次冰消期末期和全新世早期,普鲁剖面中粒度明显变粗,细砂组分含量增加,CaCO3%值均明显下降,指示了塔里木盆地内的干旱化特征；9600-650aBP之间,即中早全新世以来,粗粉砂组分含量持续增加,并且中值粒径变细,CaCO3含量也持续增加,指示了塔里木盆地内环境在这一段时间内,湿润程度逐渐增强,并且在晚全新世达到最湿润。但值得注意的是在一段时间内,粒度组分与CaCO3含量的波动更加明显,表明存在一定的干旱化间隙,如普鲁剖面中5700aBP、4200 a BP、2700 a BP等处指示湿润程度的参数值显著降低；在顶部650aBP以来,指示湿润程度的CaCO3含量与粗粉砂组分含量均显著降低,中值粒径也快速变粗,指示了快速的干旱化。由于这一段距离现代较近,除了气候变化的影响因素外,人类活动的影响也不容忽视。
[Abstract]:Loess on the northern slope of Kunlun Mountains is a homologous and heterogeneous deposit in the Taklimakan Desert. The history of climate evolution in the Tarim Basin has been recorded continuously and completely. The study of climatic information recorded by loess in Kunlun Mountains can not only reconstruct the history of environmental changes in Tarim Basin on a longer scale, but also help us to further understand the evolution of circulation and the driving mechanism of drought in the basin. The development of oasis in the basin is also restricted by climate change. The restoration of the paleoenvironmental records in the Tarim basin can provide suggestions for the sustainable development of the oasis. Based on the detailed analysis of environmental magnetism, particle size and chemical elements of Pulu loess on the northern slope of Kunlun Mountains, this paper attempts to interpret the climatic information recorded by loess. The analysis of environmental magnetism and micromorphology of magnetic minerals in Pulu section shows that the earth forming action is weak, and the magnetic minerals are mainly primary, which mainly reflect the magnetic characteristics of dust in the source area. The grain size analysis indicates that the loess grain in Prou section is coarse, which is the near source deposit of Taklimakan Desert, and the geochemical element analysis shows that the leaching effect of elements after loess deposition is very weak, which mainly reflects the chemical properties of dust in the source area. The different climatic proxy indexes all reflect that the loess in the northern slope of Kunlun Mountain has a weak remaking effect after sedimentation, which mainly reflects the physical and chemical characteristics of the source region, that is, the Tarim Basin. Therefore, the paleoenvironmental changes in the Tarim Basin can be reconstructed by using the loess records of the Pulu section. In this paper, based on the results of photoluminescence dating and particle size dating model of Prou profile, the chronological framework of Prou profile since 17500a BP is established, and the paleoclimate substitution indexes, such as environmental magnetism, granularity and geochemical elements, are combined. The paleoenvironmental change history of Tarim Basin recorded on the northern slope of Kunlun Mountains since 17500a BP is discussed. According to the grain size age model, the Pro-Loess profile should be deposited since the last extinction period, and the changes of CaCO3 content and granularity component content indicate that there is an obvious drought period in the Tarim Basin before 17000a BP. However, between 17000-14000a BP, there is an obvious wetting stage, that is, the period before Holocene in Tarim Basin. The analysis of specific climatic events still needs age support. Between 14000-9600a BP, that is, the last ice elimination period and the early Holocene, the grain size in the Prou section is obviously coarser, the content of fine sand components is increased, and the CaCO3% value is obviously decreased, indicating the characteristics of drought in the Tarim Basin. Between 9600-650aBP, i.e. since the Middle Holocene, the content of coarse silt components increased continuously, the median particle size became thinner, and the content of CaCO3 increased, indicating that the wetness of the environment in Tarim Basin increased gradually during this period of time. And reached the wetter of the late Holocene. But it is worth noting that within a period of time, the fluctuation of particle size components and CaCO3 content is more obvious, which indicates that there is a certain drought gap, such as 5700aBPU 4200a BP,2700 a BP in Prou profile and so on. Since the top 650aBP, the contents of CaCO3 and coarse silt components, indicating the degree of wetness, have been significantly reduced, and the median particle size has also been rapidly coarser, indicating the rapid drought. Because this period is close to modern times, besides the influence factors of climate change, the influence of human activities can not be ignored.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532
本文编号：2343955
[Abstract]:Loess on the northern slope of Kunlun Mountains is a homologous and heterogeneous deposit in the Taklimakan Desert. The history of climate evolution in the Tarim Basin has been recorded continuously and completely. The study of climatic information recorded by loess in Kunlun Mountains can not only reconstruct the history of environmental changes in Tarim Basin on a longer scale, but also help us to further understand the evolution of circulation and the driving mechanism of drought in the basin. The development of oasis in the basin is also restricted by climate change. The restoration of the paleoenvironmental records in the Tarim basin can provide suggestions for the sustainable development of the oasis. Based on the detailed analysis of environmental magnetism, particle size and chemical elements of Pulu loess on the northern slope of Kunlun Mountains, this paper attempts to interpret the climatic information recorded by loess. The analysis of environmental magnetism and micromorphology of magnetic minerals in Pulu section shows that the earth forming action is weak, and the magnetic minerals are mainly primary, which mainly reflect the magnetic characteristics of dust in the source area. The grain size analysis indicates that the loess grain in Prou section is coarse, which is the near source deposit of Taklimakan Desert, and the geochemical element analysis shows that the leaching effect of elements after loess deposition is very weak, which mainly reflects the chemical properties of dust in the source area. The different climatic proxy indexes all reflect that the loess in the northern slope of Kunlun Mountain has a weak remaking effect after sedimentation, which mainly reflects the physical and chemical characteristics of the source region, that is, the Tarim Basin. Therefore, the paleoenvironmental changes in the Tarim Basin can be reconstructed by using the loess records of the Pulu section. In this paper, based on the results of photoluminescence dating and particle size dating model of Prou profile, the chronological framework of Prou profile since 17500a BP is established, and the paleoclimate substitution indexes, such as environmental magnetism, granularity and geochemical elements, are combined. The paleoenvironmental change history of Tarim Basin recorded on the northern slope of Kunlun Mountains since 17500a BP is discussed. According to the grain size age model, the Pro-Loess profile should be deposited since the last extinction period, and the changes of CaCO3 content and granularity component content indicate that there is an obvious drought period in the Tarim Basin before 17000a BP. However, between 17000-14000a BP, there is an obvious wetting stage, that is, the period before Holocene in Tarim Basin. The analysis of specific climatic events still needs age support. Between 14000-9600a BP, that is, the last ice elimination period and the early Holocene, the grain size in the Prou section is obviously coarser, the content of fine sand components is increased, and the CaCO3% value is obviously decreased, indicating the characteristics of drought in the Tarim Basin. Between 9600-650aBP, i.e. since the Middle Holocene, the content of coarse silt components increased continuously, the median particle size became thinner, and the content of CaCO3 increased, indicating that the wetness of the environment in Tarim Basin increased gradually during this period of time. And reached the wetter of the late Holocene. But it is worth noting that within a period of time, the fluctuation of particle size components and CaCO3 content is more obvious, which indicates that there is a certain drought gap, such as 5700aBPU 4200a BP,2700 a BP in Prou profile and so on. Since the top 650aBP, the contents of CaCO3 and coarse silt components, indicating the degree of wetness, have been significantly reduced, and the median particle size has also been rapidly coarser, indicating the rapid drought. Because this period is close to modern times, besides the influence factors of climate change, the influence of human activities can not be ignored.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532
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