Knowledge Resource Center for Ecological Environment in Arid Area
| 柴达木盆地93ka以来古气候、古湖泊以及东亚冬季风的演化过程 | |
| 其他题名 | Palaeoenvironmental and palaeo-lake evolution, aeolian component record in lacustrine sediments and its atmospheric circulation significance since 93 ka, in Qarhan area, Qaidam Basin |
| 安福元 | |
| 出版年 | 2012 |
| 学位类型 | 博士 |
| 导师 | 马海州 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 位于青藏高原东北缘干旱区域内的柴达木盆地，地处西风带，东亚季风和印度季风的交汇区，对气候的变化非常敏感。位于盆地中东部的察尔汗地区作为柴达木盆地的沉积中心，沉积了巨厚而又连续的盐类沉积和湖相碎屑物质，而这些沉积物质详细记录了末次间冰期以来的气候系统及其湖泊演化过程，是开展区域环境对全球气候变化响应的理想载体。柴达木盆地西部广阔而风蚀的老湖相地层为察尔汗古湖提供了丰富的风成组份，是研究该地区大气环流变化过程的重要材料。本研究依托柴达木盆地察尔汗盐湖沉积中心ISL1A孔（37°3′50″N，94°43′41″E，孔深102.13m），选用钻孔岩芯中的盐类沉积物、富含有机质、碳酸盐的湖相沉积物，分别应用14C和U系测年技术获得ISL1A孔15个绝对年龄，建立了察尔汗地区晚更新世中早期（93 ka）以来的年代序列。本研究通过盐类矿物、碎屑矿物、地球化学、色度、粒度和有机物等指标综合分析，重建了察尔汗地区末次间冰期晚期以来的古气候和湖泊演化过程；通过常量元素对比、石英颗粒表面特征和粒度方法确定并分离了ISL1A孔湖相序列中的湖成和风成组份，其中风成组份记录了93ka以来柴达木盆地东亚冬季风和尘暴天气的变化过程。 \n通过上述多种指标和方法综合分析了ISL1A孔岩芯，其记录的93ka以来的气候变化、湖泊演化以及东亚冬季风演变过程如下：MIS5b（92.8～83.1ka）阶段气候稍干，降雨量减少，湖泊水位稍低，东亚冬季风稍微增强；MIS5a（83.1～71.0ka）阶段气候湿润，湖泊淡化，水位较高，东亚冬季风和尘暴天气记录明显减少；MIS4（71.0～64.0ka）阶段气候有所干化，湖泊相对咸化，水位降低，东亚季风稍微增强；MIS3c（64.0～47.1ka）阶段气候湿润，湖泊最淡化，水位达到最高，东亚冬季风大幅减弱；MIS3b（47.2～34.3 ka）阶段气候干旱，湖泊急剧咸化，进入第一期成盐期，石盐开始沉积，同时东亚冬季风和尘暴过程变强盛；MIS3a（34.3～22.2ka）阶段气候又变为湿润，湖泊由盐湖大幅淡化至碳酸盐型湖泊，水位变高，东亚冬季风和尘暴天气亦明显减弱；MIS2（22.2～14.1ka）阶段气候急剧变干，湖泊又进入第二期大规模成盐期，石盐大量析出，彻底进入盐湖阶段，东亚冬季风和尘暴天气大幅增大，幅度为全序列最大；MIS1（14.1～9.0ka）阶段气候开始好转，降雨量有所增加，盐湖稍微淡化，而冬季风和尘暴明显减弱。整个ISL1A孔记录的气候变化过程既与全球气候变化过程保持一致性，又有明显的区域特征。通过分析发现，ISL1A孔记录了60000aB.P.、50000aB.P.、39000aB.P.、30500aB.P.、24000aB.P.和l6000aB.P. 六次Heinrich快速冷事件，表明末次冰期以来柴达木盆地气候存在波动和振荡。而这些H事件可能与北半球冰量和东亚冬季风有关。 \n通过指标分析发现，部分指标的环境意义需要进一步研究明确。在干旱地区的封闭湖泊中，微咸水环境和盐湖条件下，其指标的环境意义更加复杂甚至截然不同。同时，湖相沉积中的大量风成组份对部分环境指标的解译造成干扰，使其与常规的湖相沉积环境指标的涵义相比出现差异甚至相反的情况，因此，对盐湖环境下的环境指标的指示意义解译需要深入研究和特殊对待。 \n通过ISL1A孔样品的地球化学常量元素对比、石英颗粒表面特征、粒度频率曲线特征和参数证明该孔湖相样品中存在大量风成沉积。通过粒度分布曲线对比可将ISL1A孔样品分为<2μm、2~10μm、10~70μm和70~650μm组份。其中2~10μm部分以湖成组份为主；10~70μm和70~650μm部分以风成组份为主；小于2μm的组份可能与湖泊的生物化学成因有关。上述各组份与气候变化密切相关，且各自代表的环境意义也不同：小于2μm和2~10μm部分反映了湖泊水量变化和淡化-咸化程度；10~70μm部分可能在一定程度上反映了东亚冬季风的强度；70~650μm部分反映了尘暴天气的程度。环境指标的对比分析很好地验证了ISL1A孔样品粒度各个组份划分的准确性。柴达木西部广阔的老湖相地层可能是察尔汗湖相地层风成组份的主要物源区。研究表明，柴达木盆地湖相物质为其东缘地区乃至黄土高原提供了物源物质。 \n柴达木盆地气候的干湿变化和湖泊的淡化咸化过程与东亚季风和印度季风的变化密切相关。其中东亚夏季风和印度季风的强盛造成了察尔汗流域内降雨量的增加，导致湖泊的扩张与淡化；而东亚冬季风的强盛造成了该地区的阶段干旱化，湖泊进入成盐期，风沙活动强盛。从整体上来说，北半球的太阳辐射量的变化驱动了柴达木盆地的气候变化过程，然而ISL1A孔的记录显示，该地区的气候变化对太阳辐射变化的响应存在滞后情况。 |
| 英文摘要 | TheQarhan Playa of Qaidam Basin is located at the northeastern Qinghai-Tibetan Plateau （QTP）, which is a triple junction of influences from the Asian monsoon, the westerlies, and the Southwest Indian monsoon and this makes it sensitive to past climatic variability. As the lake depo-centra since Quaternary in the Qaidam basin, it deposited quite thick lacustrine sediment and evaporites deposition in Qarhan Playa, which faithfully recorded the change of palaeoclimate and palaeo-lake during the late last interglacial period. Qarhan playa is surrounded by Gobi and yardang fields in actively folding sedimentary strata. As a huge pitfall, the paleolake trap a mass of aeolian deposits. This study carried out on the basis of 102.13 meters long core ISL1A（37°3′50″N，94°43′41″E）which drilled from the lake deposit center of Qarhan saline lake. The chronology of the core was based on 4 14C dates of organic matter contained lacustrine sediments and 11 U-series dates of evaporitic halite and calcium carbonate contained lacustrine deposits. On the basis of this reliable chronology, the evolutionary history of palaeoenvironment, palaeo-lake and the atmospheric circulation in Qarhan saline lake since 93 ka were reconstructed mainly by mineral, geochemistry, sediments color reflection, microtexture of quartz grains, grain size and organic proxy analysis of core sediments.\nBased on the above mutil-proxies of samples for ISL1A core, we can reconstruct the palaeoclimate, palaeolake and the East Asion winter monsoon （EAWM） evolution of Qaidam Basin since 93 ka: MIS5b （92.8～83.1ka）, the climate was somewhat drouthy, the level of lake surface slightly reduced and the EAWM strengthened a little; MIS5a （83.1～71.0ka）, the climate became rather humid, the level of lake surface rose again and the EAWM reduced; MIS4 （71.0～64.0ka）, the climate became more dry, the lake area was shrunk and the EAWM strengthened; MIS3c （64.0～47.1ka）, the rainfall in the catchment enchanced and palaeoclimate was very humid, the lake became freshwater-lake, meanwhile, the EAWM also showed low intensity obviously; MIS3b （47.2～34.3ka） in this phase the climate became pretty dry, the landform of Qarhan area turned into the arid Gobi and palaeolake became a saline lake, synchronously, the aeolian component appeared in the lacustrine sediments, indicating that the EAWM became rather strong; MIS3a （34.3～22.2ka） the climate turned into humid again, and the lake restored to relatively freshwater lake, level of lake surface also was back to high shoreline, the grain-size indicated that EAWM reduced remarkable; MIS2 （22.2～14.1ka）, the palaeoclimate appeared very degradational, which so dry that the lake went into the second salt period, the EAWM was strengthen sharply at the same time; MIS1 （14.1～9.0ka）, beginning from this phase, the climate restored a comfortable condition, lake was also somewhat desalination and EAWM began reduced. In summary, the palaeocliamte of Qaidam Basin both keeps consistent with glabal palaeoclimate change process and also bears its obvious area feature. By analyzing we found six Heinrich events （60000aB.P.、50000aB.P.、39000aB.P.、30500aB.P.、24000aB.P. and l6000aB.P.）, which suggesting the palaeoclimate of Qaidam Basin existed unstable phenomenon, and it may related to the ice volume of the Northern Hemisphere and EAWM.\nIn arid area and closed lake, it is need to deeply research the environmental significance of the proxies, because some proxies show different indicating significance in the freshwater sediments and saline sediments. Sometimes, as the aeolian deposits go into the lacustrine sediments, it will influence the explaination of environmental proxy, even will show opposite significance relative to the conventional proxy-interpretation of lacustrine sediments. Thus, we need to research the significance of proxies carefully in the saline sedimental environment and aeolian component mixed lacustrine environment.\nBased on major-elements analysis, microtextures of quartz grains, and features of grain-size frequency curves and other grain-size parameters, we demonstrate the existence of aeolian component in the lacustrine sequences of ISL1A core. By comparing the grain-size pattern of ISL1A core samples with the typical sediments, we found the 2~10μm fraction is mainly the lacustrine component; the 10~70μm and 70~650μm both are mainly the aeolian component. Grain-size distribution patterns of different evolution phases show the fraction of less then 2μm may relate to the origin of microorganismal chemistry. In order to testify the above conclusion we introduced the multi-proxies records and found the respective component of grain-size all relate to the process of paleoclimate. Moreover, different components indicate the different paleoclimate significances: the fractions of less than 2μm and 2~10μm reflect salinity of paleolake and the runoff intensity of catchment; 10~70μm fraction probably indicates variation the East Asian winter monsoon; 70~650μm fraction indicates the intensity of dust storms of past. Finally, the multi-proxies records well testify our previous conclusion.\nThe climate change pattern during last 93 ka in Qarhan saline lake indicate that solar insolation changes on the ten-thousand-year scale are the likely driving force of the East-Asia monsoon and Indian monsoon, which controlled precipitation in southeastern of Qaidam Basin, and influenced the palaeoclimate and palaeolake evolution of the Qarhan area, and the change of EAWM results in the weathers’ aridification and reinfocement of dust storm. Our study indicates that the changes of palaeoclimate of Qaidam Basin obviously laged the solar insolation changes. |
| 中文关键词 | 柴达木盆地 ; 察尔汗地区 ; 多指标分析 ; 气候与湖泊演化 ; 东亚冬季风 |
| 英文关键词 | Qaidam Basin Qarhan area multi-proxies analysis palaeoclimate and palaeolake evolution East Asion winter monsoon |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 地球化学 |
| 来源机构 | 中国科学院青海盐湖研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287116 |
| 推荐引用方式 GB/T 7714 | 安福元. 柴达木盆地93ka以来古气候、古湖泊以及东亚冬季风的演化过程[D]. 中国科学院大学,2012. |
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