Knowledge Resource Center for Ecological Environment in Arid Area
| 伊犁尼勒克黄土记录的末次冰期以来的古气候变化 | |
| 其他题名 | Paleoclimatic changes recorded in Nilke loess-paleosol sequences |
| 李新新 | |
| 出版年 | 2014 |
| 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 | 中亚地处中国黄土高原和欧洲两大黄土区之间，是世界上黄土的主要分布区之一，位于中亚东北部常年受西风环流控制的伊犁地区，由于其特殊的向西敞开的喇叭形地形及西风作用在盆地内沉积了大量的黄土，这些黄土真实地记录了中亚干旱区气候变化、沙漠演化、大气环流变化信息。中亚地区也是北大西洋气候区和东亚季风区的纽带，对其沉积记录、演变历史的研究可反映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的机制，这对全球气候变化机制研究有特殊意义。因此对西风区伊犁黄土的研究有助于我们认识西风干旱区黄土演化序列与东部季风区以及北大西洋地区的气候变化的关系。 本文对地处伊犁东部尼勒克县喀什河谷的一厚20.5m的黄土剖面开展了年代学、粒度、磁化率、碳酸盐、有机质、地球化学元素等指标的测试分析，并与格陵兰冰芯以及中国东部季风区的石笋氧同位素进行了对比，初步得出以下结论： 1. 粗颗粒石英光释光(OSL)和AMS14C测年结果表明在剖面上部6m，年代随着深度的增加而变老。根据OSL的年代结果外推尼勒克黄土古土壤剖面的底部年龄为52ka，为末次冰期以来的堆积。 2. 粒度分析表明尼勒克黄土剖面以粉砂为主，整体平均粒径为48.22μm，平均粒径在弱古土壤层中呈现低值，黄土层呈现高值，说明古土壤颗粒较黄土层细，黄土堆积时期风力较大。底部20m以下粒度分选性较差，粒度变化较剧烈，推测底部黄土沉积时期受到强烈的扰动作用。XRF元素分析、磁化率、碳酸盐、有机质等分析结果表明，CaO、MgO、Al2O3、K2O和Fe2O3的含量、<4μm粒径颗粒高含量均对应于弱古土壤层，而低值对应于黄土层，说明伊犁西风区古土壤堆积时期相对于黄土堆积时期气候环境较为温暖湿润。红度a*和黄度b*值与剖面黄土-古土壤的变化具有较好的对应关系。烧失量与有机质的实验研究表明伊犁地区黄土沉积物中<4μm粘粒对550℃高温烧失量贡献较大，550℃高温烧失量变化可以反映土壤中有机质和束缚水的含量变化，而950℃的高温烧失量与黄土-古土壤中碳酸盐的变化正相关，高的950℃高温烧失值反映冷干的气候环境，低的950℃高温烧失值反映比较湿润的气候环境。 3. 通过各项指标对比建立尼勒克剖面黄土-古土壤古气候序列 0-1.44m为全新世沉积(<10ka)，对应于深海氧同位素第1阶段。顶部0-0.6m为现代土壤层，沉积时期气候相对温暖湿润；0.6-1.44m为黄土堆积层，气候相对上部寒冷，但总体为温暖湿润气候。 1.44-11.2m为末次盛冰期堆积（10-24ka），对应深海氧同位素第2阶段，对比磁化率、<4μm、<10μm、>63μm、碳酸盐、有机质、常量化学元素、化学风化蚀变指数等指标将该段分为三段：1.44-5m（10-18.26ka）为寒冷湿润的黄土堆积层；5-7m（18.26-18.67ka）气候相对温暖湿润的弱古土壤层；7-11.2m(18.67-24ka)气候出现突变的盛冰期。 11.2-20.5m仍属于末次冰期堆积，对应深海氧同位素第3阶段，分为较为干冷的黄土沉积时期（11.2-15.7m, 24-39ka）；气候逐渐转湿的弱古土壤堆积期（15.7-18m，39-45.74ka）；气候波动剧烈的寒冷干旱时期（18-20.5m，45.74-52.65ka）。 4. 尼勒克黄土堆积序列对比格陵兰冰芯及中国东部季风区东部石笋记录发现，在西风环流控制的伊犁地区较好的记录了北大西洋冰伐事件，尼勒克剖面记录的末次冰期以来的粒度变粗事件既反映了伊犁地区气候的不稳定性，也说明伊犁黄土记录了具有全球意义的变冷事件以及冷暖波动旋回。伊犁尼勒克黄土粒度变化与东部季风区石笋氧同位素变化具有较好的相似性，指示西风区气候干冷时期与东亚夏季风消弱时期对应，说明西风区气候变化与东亚季风区气候变化具有一定的同步性。 |
| 英文摘要 | The Ili region is located in the northeast of central Asia arid zone, which is between the Chinese loess plateau and Europe loess area, it's one of the main distribution area of loess in the world. Owing to the special terrain structure, the Ili basin is open to the west., which is advantageous to the westerly winds entering, and provides favorable terrain and dynamic conditions for the loess deposition. The loess of the Ili basin truthfully recorded the climatic change of Central Asia arid zone, the evolution of the desert, the changes in atmospheric circulation and the climatic variation. What’s more, the study area is located in the band of the north Atlantic climate zone and the east Asian monsoon area. So it can be used to reflect the relationship of climate change between the north Atlantic region and east Asia monsoon and the climate interaction mechanism, which has a special meaning for the research of global climate change. So the study of the Ili loess can help us to know the relationship between the loess evolution sequence of the westerly arid zone and the climate of east monsoon area, as well as the relationship between the north Atlantic area of climate change. Nilke profile is 20.5m thick, which is located in the east of Nilke county of Kashi river. We carried out high resolution chronology, particle size, magnetic susceptibility, carbonate and organic matter analysis. Furthermore we compared with the oxygen isotope of the Greenland ice cores and the stalagmite of Dongge cave and Hulu cave. We draw the following conclusions. 1. Through the interpretation of the OSL, radioactive 14C dating, we found that the loess paleosol of Nilke profile was deposited from last glacial period, the bottom age of the profile is 52ka. From the top section down to 6m (<27 ka ), its age is increasing along the depth of the profile. 2. The average particle size of Nilke loess paleosol profile is 48.22μm, and the average particle size in the two weak paleosol layers is low, higher in the loess layers, which indicates that there is a strong wind in the period of the loess accumulation; the sorting of grain size is becoming poor from 20m to the bottom, and it changes dramatically, so we speculate that it was under strong disturbance of the bottom of the loess when it is deposited; the results of XRF、magnetic susceptibility、carbonate and organic matter show that the content of CaO, MgO, Al2O3, K2O, Fe2O3, and <4μm grain size, organic matter and carbonate of the weak paleosol layers is higher than in the loess layers, it reflects that in the Ili wet arid zone it is more warm and wetter in the period of accumulation of weak pale sol than the loess; red degree a* and yellow degree b* is correspondingly well with The loess paleosol cycle of this profile; clay fractions (<4μm) of Nilke loess have some correlative to the variations of LOI at 550℃, which reflects the changes of soil organic matter and bound water. And the LOI at 950℃ has a positive correlation with the soil carbonate of Ili area, which can reflect that high value of LOI at 950℃ represent cold and dry climate while low value reflects warm and wet climate. 3. Through comparing those indexes, we reconstructed loess-paleosol paleoclimatic sequences of Nike profile: 0-1.44m(<10ka), it was deposited from Holocene, corresponding to the Marine sea oxygen isotope stage(MIS) 1. The top of the 0-0.6 m is modern soil layer, the climate was warm and wet when it deposited; 0.6-1.48m is mainly accumulated of loess, it was colder than The top of the 0-0.6 m, but it’s also warm and wet when it deposited. 1.44-11.2m(10-24ka), it was deposited from last glacial maximum, corresponding to MIS 2. Comprehensive analysis of particle size, magnetic susceptibility, carbonate, organic matter, major chemical elements and CIA, we divide this segment loess deposition into three parts, the first part is from 1.44m to 5m (10-18.26ka), corresponding to the loess accumulation period, it’s cold and w |
| 中文关键词 | 伊犁 ; 尼勒克 ; 黄土 ; 末次冰期 ; 古气候 |
| 英文关键词 | Ili Nilke loess last glaciation paleoclimatic |
| 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/2XILL650/287366 |
| 推荐引用方式 GB/T 7714 | 李新新. 伊犁尼勒克黄土记录的末次冰期以来的古气候变化[D]. 中国科学院大学,2014. |
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