末次冰消期以来柴达木盆地东部风成沉积记录的气候变化

发布时间：2018-05-05 15:11

本文选题：柴达木盆地 + 风成沉积　；参考：《中国科学院研究生院(地球环境研究所)》2015年硕士论文

【摘要】：柴达木盆地位于青藏高原东北部,为祁连山、阿尔金山和昆仑山所环绕,盆地西北部紧邻极端干旱的塔里木盆地,东南部位于西风环流和东亚季风的结合处。盆地的东南部、西南缘和中部的三湖地区风成沉积和风蚀地貌十分发育,这些风成沉积记录了柴达木盆地风沙活动历史与气候演化信息。研究柴达木盆地风成沉积有助于研究西北内陆风沙活动与西风、季风环流系统及全球气候变化的关系和驱动机制。本文以前人在柴达木盆地东部风成沉积剖面的研究资料为基础,对盆地东南部都兰县的香日德(XRD)和夏日哈(XRH)风成沉积剖面开展详细的年代学、粒度、色度、地球化学等气候代用指标的分析,并与古里雅冰芯、西风区湖泊等记录进行对比,初步得出以下结论:(1)光释光(OSL)和加速器质谱仪(AMS)14C测年结果表明,XRD剖面形成于6.25~1.33 ka,XRH剖面形成于14.13~5.83 ka,构成末次冰消期以来的时间序列。(2)粒度分析表明XRD剖面平均粒径值为32.48μm,砂质古土壤和砂质黄土的分选要优于风成砂;XRH剖面平均值194.80μm,风成砂分选优于砂质古土壤。两个剖面的物源均表现出近源和远源叠加形成,为典型风成沉积。其中63μm粗颗粒组分含量可以与古里雅冰芯和西风区湖泊进行对比,揭示盆地东部末次冰消期以来的气候演化与全球气候记录具有一致性。(3)地球化学数据显示XRD剖面处于低等化学风化和中等化学风化之间,部分砂质古土壤的CIA值高于洛川古土壤平均值;XRH剖面处于低等化学风化阶段,砂质古土壤的CIA平均值低于洛川黄土平均值。(4)柴达木盆地风成沉积记录显示盆地东部14.13~10.62 ka期间,湿度较大,风沙活动较弱;10.62~7.16 ka阶段,湿度和温度均降低,风砂活动强烈;7.16~5.83 ka期间,快速增温增湿,成壤作用加强,风沙活动迅速减弱;5.83~1.33ka阶段,处于较高温度和湿度的适宜期,风成砂固定成壤。“4.2 ka”事件在柴达木盆地东部风成沉积记录中表现突出,4.16~3.8 ka阶段地层中石英微形态主要呈擦痕和“V”形坑,指示这次突变事件为洪泛事件,并非风沙强烈活动事件,这对于理解晚全新世气候不稳定性和古人类文化兴衰具有重要意义。(5)柴达木盆地东部风成沉积记录的气候变化不同于石笋和太阳辐射强度曲线的变化趋势,与古里雅冰芯氧同位素、博斯腾湖的有效湿度以及克鲁克湖的孢粉记录变化趋势相一致。气候变化呈现出早全新世干旱,中晚全新世湿润的特点,揭示盆地东部末次冰消期以来气候变化模式更符合“西风模式”,而非季风区气候变化特征。
[Abstract]:The Qaidam Basin is located in the northeast of the Qinghai-Xizang Plateau, surrounded by the Qilian Mountains, the Aljin Mountain and the Kunlun Mountains. The northwestern part of the basin is adjacent to the extremely arid Tarim Basin, and the southeast is located at the junction of the westerly circulation and the East Asian monsoon. The aeolian deposits and wind-eroded landforms are well developed in the southeastern part of the basin, the southwest margin and the three lakes in the central part of the basin. These aeolian deposits record the historical and climatic evolution information of the aeolian sand activity in the Qaidam Basin. The study of eolian deposition in Qaidam Basin is helpful to study the relationship and driving mechanism between the eolian sand activity in northwest China and the westerly monsoon circulation system and global climate change. Based on previous studies on the eolian sedimentary profiles in the eastern Qaidam Basin, detailed chronology, granularity, chromaticity of the XRD and XRH) sections of Dulan County, southeastern Qaidam Basin, have been carried out in this paper. Analysis of climate proxy indicators such as geochemistry, and comparison with the records of the Guliya ice core and lakes in the westerly region, The preliminary conclusions are as follows: (1) OSL) and AMS / 14C dating results show that the XRD profile was formed in 6.25 ~ 1.33 ka- XRH section at 14.135.83 ka. the particle size analysis shows that the average particle size of XRD profile is the same as that of the time series since the last ice depletion period. The value is 32.48 渭 m. The separation of sandy paleosol and sandy loess is better than the average value of XRH profile of aeolian sand (194.80 渭 m), and that of aeolian sand is better than that of sandy paleosol. The provenance of the two sections is characterized by near-source and far-source stacking, which is a typical aeolian deposit. The contents of 63 渭 m coarse particles can be compared with those of the Guliya ice core and the lakes in the westerly region. It is revealed that the climatic evolution in the eastern part of the basin is consistent with the global climate record. The geochemical data show that the XRD profile is between low chemical weathering and moderate chemical weathering. The CIA value of some sandy paleosols is higher than the average value of Luochuan paleosol. The CIA average of sandy paleosol is lower than that of Luochuan loess. During the period of higher humidity and weaker wind sand activity, both humidity and temperature decreased. During the period of 7.165.83 ka, the rapid warming and humidification, the strengthening of earth-forming process, the rapid weakening of wind-sand activity at 5.83 ~ 1.33ka, and the suitable period of higher temperature and humidity were observed. The "4.2 ka" event in the aeolian sedimentary records of the eastern Qaidam Basin shows that the quartz micromorphology in the strata of stage 4.16 ~ 3.8 ka is mainly grazed and "V" shaped, indicating that this sudden event is a flood event. It is not a violent event of wind and sand, This is of great significance for understanding the climatic instability of the late Holocene and the rise and fall of paleo-human culture.) the climatic changes recorded in the east-Qaidam basin are different from those of stalagmite and solar radiation intensity curves. It is consistent with the oxygen isotopes of Guliya ice core, the available humidity of Bosten Lake and the change trend of pollen records of Lake Kruke. The climate change shows the characteristics of early Holocene drought and middle and late Holocene wetness, which reveals that the climate change model in the eastern part of the basin is more in line with the "westerly model" than in the monsoon region.
【学位授予单位】：中国科学院研究生院(地球环境研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532;P534.63

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