【作者】 范喆；

【导师】 杨太保；

【作者基本信息】 兰州大学 ， 自然地理学， 2010， 博士

【摘要】 尕斯库勒湖位于柴达木盆地,柴达木盆地作为高原内部的一个巨型山间盆地,发育了连续、完整、巨厚的第四纪沉积,其处于西风带、东亚季风带和西南季风的交汇处,同时也是世界上最大的非地带性温带干旱区中心。盆地内高分辨率的湖泊沉积物记录是气候和环境演化最敏感的指示器,具有连续性、敏感性和高分辨率的特点。对其研究对于加深亚洲中部干旱区及高原对全球变化的响应及反馈机制的理解,特别是青藏高原东北缘干旱-干寒区的气候变化具有十分重要的意义。论文以柴达木盆地西北缘长222米的尕斯库勒湖泊钻孔为研究对象,根据磁性地层学基础建立的GSK0305钻孔时间标尺,钻孔的底界年龄约为1301kyr,以2cm间隔连续采样,对243个样品34种元素及氧化物含量、9788个样品的磁化率、色度及部分粒度指标进行了测试分析。对22个常、微量及氧化物元素的相关性分析表明主要化学成份与微量元素变化趋势一致,Al2O3、MgO、K2O、SiO2、Fe2O3及Li、V、Cr、Co、Ni、Cu、B、Ga的变化趋势基本一致；SiO2和Na2O的分布基本一致；金属元素中Cu、Zn具有较高的相关系数(0.872),这与其它研究者(Erik,2000)关于这两种元素在湖泊沉积物负相关的结论不一致,这有可能是因为沉积物中Cu的分布主要反映了生物活动,对氧化还原状态的反映为其次,Cu的粘合力在沉积物中会因生物成因碎屑的氧化而减少；微量元素Ba与Ti、Cr相关度较高,相关系数在0.9以上；元素对比值SiO2/Al2O3、Sr/Ba、Rb/Sr指示的环境意义表现相同,在与深海氧同位素LR04的对比中表现了较高的一致性。GSK0305孔的磁化率变化与深海氧同位素曲线一样具有典型锯齿状的特征,其形成机制与Pannonian盆地相似,即冰期—间冰期旋回控制的气候变化导致河流径流量和搬运能力的变化,进入尕斯库勒湖西岸冲积平原的强磁性矿物(碎屑成因)含量的变化,最终引起磁化率值的变化。在元素、元素对分析对比的基础上,为了更加清晰地了解GSK0305钻孔在不同化学分化阶段所指示的环境意义、了解湖泊沉积物所受控的因子,论文引入了主成分分析(PCA)方法。分析得出了3个主要因子F1、F2、F3,代表了全部信息的79.87%,F1 (Ni、Zn、MgO、Y、P、Fe2O3、Co、Nb、Mn、Cu,10个正相关元素/氧化物,以及SiO2一个负相关氧化物)得分45.485%, F2 (Mo、Ba、La,3个正相关元素,Ga、Al2O3、V,3个反消长的元素/氧化物)得分24.915%,F3(Zr和Rb)得分9.472%；进而通过与气候代用指标的对比提出了F1因子反映了气候干湿状况对沉积物化学组分的影响,因子的得分曲线可以在一定程度上近似反映气候干湿变化的历史,对研究区而言亦可近似反映夏季风变化的历史；F3因子反映了冷暖状况对沉积物化学组分的影响,因子的得分曲线近似反映气候冷暖变化的历史,近似反映冬季风变化的历史。更多还原

【Abstract】 Lake Gas Kure is in the Qaidam Basin, which situated at the northeastern Tibetan Plateau, is in the central part of the arid Asia, which is the biggest non-zonal arid area in temperate zone on the earth, and is the conjunction area among the westerly jet, southeastern Asia Monsoon and southwestern Asia Monsoon that influence the climate of China. Therefore, this very sensitive to the regional and global changes. The study on the climate change history in the arid-cold area of the northeastern Tibetan Plateau is of great theoretical and applied importance.On the basis of tie points derived by matching the observed magnetostratigraphy to the geomagnetic polarity timescale (GPTS), an orbitally tuned timescale for core GSK0305 was developed, which assigns an age of 1320 kyr for the base of the core. The GSK0305,222 meters drill of Lake Gas Kure was to 2cm intervals continuous sampling, on 243 samples of 34 kinds of elements and oxides,9,788 samples of the magnetic susceptibility, color and some grain size indicators were tested.22 major and trace element and oxides analysis of correlation showed that the main chemical components and trace elements in the same trend, such as Al2O3, MgO, K2O, SiO2, Fe2O3, and Li, V, Cr, Co, Ni, Cu, B, Ga consistent trends; SiO2 and Na2O are basically the same distribution; metal elements Cu, Zn has a high correlation coefficient (0.872), which other researchers (Erik,2000) taken these two as negative elements in lake sediments, this may be because of the distribution of Cu in sediments mainly reflects the biological activity of the redox state of the reflected Secondly, Cu adhesion in sediments due to the oxidation of biogenic debris is reduced; trace elements Ba and Ti, Cr high correlation, the correlation coefficient above 0.9; elements on the ratio of SiO2/Al2O3, Sr/Ba, Rb/Sr indicates the performance of the environmental significance of the same, with the deep-sea oxygen isotope comparison of the performance of the LR04 higher consistency.In study of GSK0305, magnetic susceptibility and oxygen isotope curves has the same features of a typical jagged, and it has the same mechanism of the Pannonian basin:glacial-interglacial cycles of the control of river runoff due to climate change and changes in transport capacity into Gas Kure Lake west of the alluvial plain strong magnetic minerals (detrital origin) levels, and ultimately lead to magnetic susceptibility values.Principle component analysis (PCA) was used to identify the main factors that control elemental distribution in sediments and to add interpretative strength to the geochemical behavior of selected major and trace elements. Three important factors were identified using factor analysis method, which control chemical composition of sediments, such as catchment erosion, diagenetic modification and endogenic calcium carbonate precipitation. Further research indicates that the factor score curves of catchment erosion and endogenic calcium carbonate precipitation can be used to represent the changes of humidity and temperature respectively, which provides a new effective approach to palaeoclimate reconstruction. On the basis of paleomagnetism and magnetostratigraphy, the evolution history of the regional climate and environment is evaluated. Climate proxies, such as Magnetic Susceptibility, Sediment Color Reflectance parameters, Grain size records were also evaluated, and it is revealed that the basic climate succession in the region of northwestern Qaidam Basin, northern Tibetan Plateau.更多还原