Knowledge Resource Center for Ecological Environment in Arid Area
| 新疆伊犁黄土沉积与末次冰期以来的环境变化 | |
| 其他题名 | The loess deposition in the Ili area of Xinjiang and climate change since the Last Glacial Period |
| 李传想 | |
| 出版年 | 2012 |
| 学位类型 | 硕士 |
| 导师 | 宋友桂 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 伊犁地区地处中亚东北部，即位于研究程度很高的中国黄土高原和欧洲两大黄土区之间的关键部位，又处于近地面西风环流的尾闾地带，是连接我国季风区和北大西洋环流的纽带。在西风环流作用之下，粉尘被携带到伊犁盆地山前地带堆积，数米到近百米的黄土堆积于盆地内河流阶地和山麓地带，真实地记录了亚洲内陆干旱区气候变化和沙漠变迁、西风环流演化及其北大西洋地区与东亚季风区气候变化的关系和气候相互作用机制的信息。因此，伊犁黄土对研究包括中国西北干旱区在内的亚洲内陆干旱化过程、西风和季风之间的关系及其全球变化的驱动机制研究具有重要的理论和实际意义。\n本文以前人对伊犁黄土的研究资料为基础，结合野外考察资料对处于西风区的伊犁黄土的分布、年代和粉尘来源进行了分析总结。通过对伊犁昭苏剖面黄土进行系统的矿物学、磁化率、粒度和地球化学元素等指标测量和分析，并与盆地东部和黄土高原黄土及其格棱兰冰心等记录进行了初步对比研究，旨在查明伊犁黄土矿物组成；探讨磁化率增强机制的差异性；分析伊犁黄土的成因、物质来源和空间堆积差异及其黄土和古土壤形成环境的差异性；重建末次冰期以来中亚地区的气候变化；揭示伊犁黄土常量元素的分布规律及其堆积后经历的化学风化特征。本文获得以下一些新的认识：\n（1）伊犁黄土矿物组成与黄土高原黄土-古土壤较为一致，均以石英、长石类和碳酸盐矿物为主，但不同的是，重矿物中角闪石含量前者高于后者，帘石类含量相反，不透明矿物相差无几。黄土和古土壤碳酸盐淋滤作用较弱，石英表面形态较为干洁，均表明伊犁黄土形成于较干冷气候条件下。\n（2）伊犁昭苏黄土细粒组分对磁化率的贡献非常有限，粗颗粒组分对磁化率贡献较大，说明磁性载体主要存于粗颗粒组分中。伊犁黄土磁化率成因机制既具有阿拉斯加风速论模式的特点又叠加了黄土高原成壤作用的模式，即使在同一剖面的不同时段两种模式对磁化率增强的贡献也不同，伊犁黄土磁化率增强机制存在着时空差异性。\n（3）粒度分布特征表明伊犁黄土主要为风成成因，其形成可能是近源物质与远源粉尘沉积作用叠加的结果，不同地区黄土在堆积过程所受到动力条件可能存在明显的差异；伊犁黄土中粘土组分可能主要来自中亚荒漠和伊犁河中、下游地区，西风带来的粉尘对伊犁盆地不同地区黄土的贡献率不同。\n（4）伊犁古土壤层中＞30 mm、＞40 mm和＞63 mm等粗粒径组分含量较黄土层稍高，尤其是砂粒组分更为显著，表明伊犁古土壤形成时期，西风环流较强，导致古土壤层中存在大量粗颗粒的近源堆积物，气候存在突变性，是一个环境变化不稳定的时期，而黄土堆积时，西风较弱，气候变化相对稳定。\n（5）伊犁昭苏剖面粒径＞63 mm组分含量变化能与格陵兰冰芯进行良好对比，记录了Heinrich事件和Younger Dryas冷事件及D-O旋回等具有全球意义的气候波动事件，揭示中亚地区末次冰期以来的气候变化具有全球特征。\n（6）伊犁昭苏剖面黄土和古土壤主要元素含量具有较好的一致性，暗示沉积后两者所经历的风化作用相差不大。CIA指数、Na/K比值及A-CN-K图解均显示伊犁黄土和古土壤均经历了低等强度的化学风化作用，弱于黄土高原黄土及古土壤，黄土和古土壤风化分异作用不明显，末次冰期以来伊犁黄土和古土壤均形成于较为干冷的气候环境条件下。 |
| 英文摘要 | TheIli area lies in the Northeast of Asia, not only locates in the key part between the well-studied European loess sequences to the west and the extensive Chinese Loess Plateau (CLP) to the east, but also in the marginal area of the near ground westerly circulation, is a bond to link the Monsoon Region in China and the North Atlantic Ocean Circulation. Under the effect of the westerly circulation, dust was carried to the piedmonts of the Ili Basin and deposited, several to nearly a hundred meters thickness loess sediments are exposed along the river terraces and piedmonts of Tianshan Mountains, authentically record the information of climate change and the vicissitude of desert in the arid region of Asia inland, westerly circulation evolution, the climate interaction mechanism, relationship of climate change between the North Atlantic region and East Asia Monsoon Region. The loess in Ili region has important theoretical and practical implications for the studies on the drying process of Asian inland including China's northwestern arid region, relationship between westerly and monsoon, driving mechanism of the global change.\nIn this study, based on previous study and information on the Ili loess, combining with the recently investigated data in the field, the author summarized the distribution, age and origin of the Ili loess dominated by the westerlies. Comparison with the loess of the eastern part of the basin and the CLP, the records of Greenland ice core, the author have measured and analyzed systematically the proxies of loess mineralogy, magnetic susceptibility, grain sizes and geochemical elements at the Zhaosu loess section in the Ili to aim at finding out the mineral composition; discuss the differences in the enhancement mechanism of magnetic susceptibility of the Ili loess; analyzed the origin and material sources, the Ili loess differ in spatial accumulation and the formation environment differences of loess and paleosol; reconstruct the climate changes in the Central Asia since the last glacial; reveal the element distribution and chemical weathering characteristics after deposition of the loess in the Ili. We can draw some new findings as follows:\n（1）The mineral composition of loess and paleosol in the Ili Basin is similar to that of the CLP; but the difference is that the content of hornblende of heavy mineral in the former is more than the latter, the epidote group is opposite in both, the opaque minerals between them is nearly consistent. The carbonate leaching effect was weaker in the loess and paleosol, and quartz surface morphology is relatively clean, all indicate that the Ili loess formed in a dry and cold climate conditions.\n（2）The contribution of fine components in the Ili Zhaosu loess to the loess magnetic susceptibility is very limited, suggesting that the magnetic carriers in the study area exist mainly in the coarse components. The mechanism of susceptibility formation in the Ili loess can be interpreted as either Alaska wind model or pedogenesis model of the CLP. However, the two models have different contributions to the loess magnetic susceptibility in different regions of the Ili Basin, and even have different contributions to the enhancement of magnetic susceptibility in different periods of the same section, i.e., the enhancement mechanism of magnetic susceptibility in the Ili loess has spatial-temporal differences.\n（3）The characteristics of grain size distribution indicate the Ili loess is of aeolian origin, its formation may be the result of the superposition effect of the close source material and far dust deposition, the dynamic conditions in process of the deposition of loess in different regions in the Ili Basin may have significant differences. The grain size analysis show that the clay component in loess in the Ili Basin may be transported from Central Asia desert and the middle and lower reaches of Ili River, but the dust brought by the westerlies have different contributions to the loess in the different regions of the Ili Basin.\n（4）The content of coarse grain sizes ＞30 mm, ＞40 mm and ＞63 mm in the paleosol layer in Ili region is higher than that of the loess layer, especially in the sand component, which suggests that a lot of coarse component accumulation from near sources in the paleosol layer resulted from the enhanced the westerly circulation during the period of the Ili paleosol formation, there has existed the mutation of the climate and environmental change was instable in this period. While loess deposited, the westerly wind was weaker, the climate change was relatively stable.\n（5）The content of grain size ＞63 µm in the Ili loess can be well compared with the records of Greenland ice core that the climate fluctuations of the global significance such as Heinrich events and the Younger Dryas cold event as well as D-O cycles, reveals the Central Asian's climate changes with the global features since the last glaciation.\n（6）The content of major elements in the loess and paleosol at the Zhaosu section in the Ili region have a good consistency, which implies that both of them experienced almost the same chemical weathering intensity after deposition. CIA index, Na/K ratio and A-CN-K diagrams all demonstrate that the Ili loess and paleosol experienced low chemical weathering intensity which was weaker than that in the CLP, and that no obvious chemical weathering differentiation between loess and paleosol, the Ili loess and paleosol formed under a relatively dry and cold climate conditions since the last glaciation. |
| 中文关键词 | 伊犁盆地 ; 黄土沉积特征 ; 古环境意义 ; 末次冰期以来 |
| 英文关键词 | Ili Basin loess deposition features paleoenvironmental significance since the last glacial period |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地球环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287061 |
| 推荐引用方式 GB/T 7714 | 李传想. 新疆伊犁黄土沉积与末次冰期以来的环境变化[D]. 中国科学院大学,2012. |
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