【摘要】：昆侖山北坡黃土是塔克拉瑪干沙漠的同源異相沉積,連續(xù)完整得記錄了塔里木盆地內(nèi)氣候演化的歷史。研究昆侖山黃土記錄的氣候信息,不僅能夠重建塔里木盆地內(nèi)更長(zhǎng)尺度以來(lái)的環(huán)境變化歷史,還有助于我們進(jìn)一步理解盆地內(nèi)環(huán)流的演化和干旱化的驅(qū)動(dòng)機(jī)制；盆地內(nèi)的綠洲發(fā)展也同樣受制于氣候的變化,恢復(fù)塔里木盆地內(nèi)過(guò)去的古環(huán)境記錄,能夠?yàn)榫G洲的可持續(xù)發(fā)展提供建議。本文通過(guò)對(duì)昆侖山北坡的普魯黃土進(jìn)行詳細(xì)的環(huán)境磁學(xué)、粒度以及化學(xué)元素的分析,嘗試對(duì)黃土記錄的氣候信息加以解釋。普魯剖面黃土的環(huán)境磁學(xué)與磁性礦物的微觀形態(tài)分析表明成壤作用微弱,磁性礦物以原生為主,主要反映了源區(qū)粉塵的磁學(xué)特征；粒度分析指示普魯剖面黃土顆粒較粗,是塔克拉瑪干沙漠的近源沉積；地球化學(xué)元素分析表明黃土沉積后元素的淋溶作用很弱,主要反映了源區(qū)粉塵的化學(xué)性質(zhì)。不同的氣候代用指標(biāo)均一致的反映出,昆侖山北坡黃土在沉積之后再次改造作用微弱,主要反映了源區(qū),即塔里木盆地內(nèi)物質(zhì)的理化特征,因此利用普魯剖面黃土記錄能夠重建塔里木盆地內(nèi)的古環(huán)境變化。本文通過(guò)普魯剖面光釋光年代結(jié)果和粒度年代模型建立普魯剖面17500a BP年以來(lái)的年代框架,并結(jié)合環(huán)境磁學(xué)、粒度和地球化學(xué)元素等古氣候代用指標(biāo),初步討論了昆侖山北坡黃土記錄的塔里木盆地17500a BP以來(lái)的古環(huán)境變化歷史。根據(jù)粒度年代模型,普魯黃土剖面29m以上應(yīng)為末次消期以來(lái)沉積,CaCO3含量與粒度組分含量變化均指示了在17000a BP之前塔里木盆地內(nèi)是明顯的干旱期,而17000-14000a BP之間出現(xiàn)明顯的濕潤(rùn)階段,即塔里木盆地在全新世之前的一段濕潤(rùn)時(shí)期,具體的氣候事件分析仍需要年代支持；在14000-9600a BP之間,即末次冰消期末期和全新世早期,普魯剖面中粒度明顯變粗,細(xì)砂組分含量增加,CaCO3%值均明顯下降,指示了塔里木盆地內(nèi)的干旱化特征；9600-650aBP之間,即中早全新世以來(lái),粗粉砂組分含量持續(xù)增加,并且中值粒徑變細(xì),CaCO3含量也持續(xù)增加,指示了塔里木盆地內(nèi)環(huán)境在這一段時(shí)間內(nèi),濕潤(rùn)程度逐漸增強(qiáng),并且在晚全新世達(dá)到最濕潤(rùn)。但值得注意的是在一段時(shí)間內(nèi),粒度組分與CaCO3含量的波動(dòng)更加明顯,表明存在一定的干旱化間隙,如普魯剖面中5700aBP、4200 a BP、2700 a BP等處指示濕潤(rùn)程度的參數(shù)值顯著降低；在頂部650aBP以來(lái),指示濕潤(rùn)程度的CaCO3含量與粗粉砂組分含量均顯著降低,中值粒徑也快速變粗,指示了快速的干旱化。由于這一段距離現(xiàn)代較近,除了氣候變化的影響因素外,人類(lèi)活動(dòng)的影響也不容忽視。
[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.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P532

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本文編號(hào)：2343955