天山北麓黄土记录的末次间冰期以来气候变化初探

发布时间：2019-03-28 14:17

【摘要】：末次间冰期以来气候变化的研究是当前古气候研究的热点之一。对末次间冰期以来气候变化进行系统研究,找出气候变化在地球演化历史中的规律,有助于我们更好的理解气候系统,同时也有助于我们更加准确的预测未来气候的发展趋势。新疆地区位于中亚干旱区,气候变化复杂,目前对新疆地区末次间冰期以来系统的沉积物记录研究较少,对其干旱化历史和驱动机制仍缺乏足够的了解。本文对天山北麓柏杨河黄土剖面粒度、环境磁学和有机碳含量等参数进行了系统测定,选取合适的参数作为气候代用指标。通过气候代用指标曲线与深海氧同位素曲线的对比获得了可靠的年代控制点,在此基础上恢复和重建了新疆地区末次间冰期以来的气候演变历史,将重建的气候演化历史与西风区其他黄土剖面记录及格陵兰GRIP冰芯记录进行对比,主要得到以下认识:柏杨河黄土粒度较粗,粒级组分以粉砂为主,与黄土高原黄土和新疆其他地区黄土的粒度特征一致。黄土主要为近源粉尘沉积,远源粉尘较少。磁性矿物以亚铁磁性矿物为主,磁性矿物含量远低于黄土高原黄土;原生碎屑磁性矿物含量较多,后期成壤过程形成的次生磁性矿物含量较少;磁性矿物磁晶体粒径较粗。有机碳含量较低,且在整个剖面上变化不大。新疆地区末次间冰期以来的气候变化特征为:1)末次间冰期以前(148.6～130kaBP)风动力较强,气候较为干旱。2)末次间冰期130～120kaBP期间风动力强度较弱,虽然由于蒸发量的快速增加,气候没有明显变湿,但仍有一层古土壤发育;120～96kaBP期间风动力强度增加,气候变干;96～71kaBP期间风动力强度再次减弱,并伴随区域湿润程度的显著增加,暖湿的气候使该时期发育了一个较明显的古土壤层。3)末次冰期71～57kaBP期间风动力强度显著增加,同样是由于蒸发量的影响,气候没有明显变干,还处于较湿润的状态;57～29ka BP是末次冰期气候较为温暖的时期,风动力强度减弱,区域湿润程度增加;29～14kaBP期间气候再次发生剧烈变化,气候向冷干的方向发展。4)14kaBP以来风动力强度逐渐减弱,区域湿润程度逐渐增加。柏杨河剖面末次间冰期以来的气候记录与西风区其他黄土剖面的记录具有很好的对应关系:冰期或者冰阶时,风动力强度较强,气候较为干旱;间冰期或者间冰阶时,风动力强度较弱,气候较为湿润;表明西风区末次间冰期以来的气候变化具有一致性特征。进一步与格陵兰GRIP冰芯记录对比发现,西风区黄土记录与GRIP冰芯记录在轨道尺度和亚轨道尺度上都具有较高的可对比性。末次冰期时在北大西洋地区普遍发生的气候快速波动事件在西风区的黄土记录中同样存在,指示了西风区末次间冰期以来气候变化与北大西洋地区气候变化具有密切的关系。
[Abstract]:The study of climate change since the last interglacial age is one of the hotspots of paleoclimate research. A systematic study of climate change since the last interglacial age to find out the law of climate change in the evolution history of the earth will help us to better understand the climate system and at the same time help us predict the development trend of the climate in the future more accurately. Xinjiang is located in the arid region of Central Asia with complex climate change. At present, there is little research on systematic sediment records since the last interglacial age in Xinjiang, and there is still a lack of sufficient understanding of its arid history and driving mechanism. In this paper, the grain size, environmental magnetism and organic carbon content of the loess section of Baiyang River in the northern foot of Tianshan Mountains have been systematically measured, and appropriate parameters have been selected as climatic substitute indexes. A reliable chronological control point was obtained by comparing the climatic substitution index curve with the deep sea oxygen isotope curve. On this basis, the climatic evolution history since the last interglacial age in Xinjiang was restored and reconstructed. Comparing the reconstructed climatic evolution history with the records of other loess sections in the westerly region and the GRIP ice core records in Greenland, the main results are as follows: the size of the Baiyang River loess is coarse and the size of the loess is mainly composed of silty sand. It is consistent with the grain size characteristics of loess in Loess Plateau and other regions of Xinjiang. Loess is mainly near-source dust deposition, far-source dust is less. The main magnetic minerals are ferromagnetic minerals, the content of magnetic minerals is much lower than that of loess in Loess Plateau, the content of primary clastic magnetic minerals is more, the content of secondary magnetic minerals formed in the later stage of soil formation is less, and the magnetic crystals of magnetic minerals are coarse. The organic carbon content is low, and there is little change in the whole section. The characteristics of climate change since the last interglacial period in Xinjiang are as follows: 1) the wind dynamics before the last interglacial period (148.6~130kaBP) is stronger and the climate is relatively arid. 2) the wind dynamic intensity is weak during the last interglacial period during 130~120kaBP. Although the climate is not obviously wetted due to the rapid increase of evaporation, there is still a layer of paleosol development. During the period of 120~96kaBP, the intensity of wind power increases and the climate dries; The wind dynamic intensity decreased again during 96~71kaBP, accompanied by the significant increase of regional wetness, and the warm and wet climate resulted in the development of an obvious paleosol layer in this period. 3) during the last glacial period, the wind dynamic intensity increased significantly during the 71~57kaBP period. It is also due to the influence of evaporation, the climate is not obviously dry, it is still in a wetter state; 57~29ka BP is a warm period of climate in the last ice age, the intensity of wind power is weakened, and the degree of regional wetness is increased. During the period of 29~14kaBP, the climate changed violently again, and the climate developed to cold-dry direction. 4) since 14kaBP, the intensity of wind power gradually weakened, and the degree of regional wetness gradually increased. The climatic records since the last interglacial age of the Baiyanghe section have a good correspondence with the records of other loess sections in the westerly region: during the ice age or ice stage, the wind dynamic intensity is stronger and the climate is relatively dry; During the interglacial period or interglacial stage, the wind dynamic intensity is weak and the climate is relatively moist, which indicates that the climate change in the westerly area since the last interglacial age is consistent. Compared with the GRIP ice core records in Greenland, it is found that the loess records in the westerly region and the GRIP ice core records are highly comparable in both orbital and suborbital scales. The rapid climatic fluctuation in the North Atlantic during the last glacial age also exists in the loess records in the westerly region, indicating that the climate change in the westerly region has a close relationship with the climate change in the North Atlantic since the last interglacial age.
【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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