Knowledge Resource Center for Ecological Environment in Arid Area
| 内蒙古西部额济纳古湖小狐山剖面有机质与碳酸盐组成及其古环境意义 | |
| 其他题名 | Compositions of the organic matter and carbonate in Xiaohushan section from Ejina Basin, western inner Mongolia, China and their paleoenvironmental significance |
| 杨伦庆 | |
| 出版年 | 2009 |
| 学位类型 | 硕士 |
| 导师 | 张虎才 |
| 学位授予单位 | 中国科学院南京地理与湖泊研究所 |
| 中文摘要 | 独特的地质构造作用、海陆分布格局和大气环流三个因素造就了我国西北地区的自然地理格局和半干旱、干旱，甚至极端干旱的气候环境，这里不但生态环境脆弱，气候环境变化剧烈，并对全球变化和人类活动响应敏感。然而，在西北干旱区进行的大量地质地貌（湖蚀地形地貌和湖岸阶地）、沉积和古生物证据表明，与现今干旱的气候环境相比，西北地区在晚更新世中晚期的气候环境却与现在大不相同，特别是降水量明显高于现代，导致大面积湖泊发育，许多区域湖泊扩张延绵形成大湖区。西北地区环境的快速演变及其原因引起了科学家广泛的关注，成为全球变化研究的热点区域之一。内蒙古自治区西部的额济纳盆地（也称弱水盆地），是我国内陆干旱区代表性的盆地之一。因此对额济纳盆地古环境、古气候变化的研究将有助于加深对西北干旱区对全球变化的响应和影响的理解。深入地研究西北干旱区的气候变化具有十分重要的理论价值。\n 基于此，本论文选取额济纳盆地小狐山剖面为研究对象，通过对该剖面沉积物中TOC、TN、碳酸盐含量、碳酸盐δ13C、δ18O及沉积物粒度等环境指标进行了分别测试，探讨了各指标的古气候环境意义；结合有机质AMS 14C和常规14C及无机碳酸盐常规14C的测试并建立的年代序列，通过综合分析，重建了额济纳古湖晚更新世期间古环境变化的历史。本论文的主要结论和认识如下：\n（1） 额济纳古湖湖泊沉积物中有机质（TOC、TN）含量与湖泊发育和气候环境紧密相关，是气候环境变化的良好指标，沉积物中TOC、TN主要由湖泊内源产生，主要反映湖泊自身初级生产力的变化。碳酸盐含量作为古湖泊沉积中主要物质组分之一，其变化反映了湖泊沉积过程和环境的变化。额济纳古湖小狐山剖面沉积物中以自生碳酸盐（方解石）为主的含量变化受湖区有效湿度和湖泊藻类生产力的综合影响。碳酸盐δ13C反映了流域内植被类型和湖泊自身生物生产力的变化，δ18O指示了湖水温度和湖区有效湿度的变化。在小狐山剖面中总有机质（TOC）、有机氮（TN）含量和<2m粒度组分含量与沉积相严格相关，当TOC，TN和<2m粒度组分含量分别大于0.150%、0.015%和5%时为湖相沉积，反之则为非湖相的风沙堆积。\n（2） 小狐山剖面沉积物饿物理指标和化学指标记录的晚更新世中晚期古湖泊和气候环境演化经历了如下主要过程：? ~ 38.15 14C kaB.P.（1039 ~ 949 cm）湖区气候为冷干环境特征，风沙盛行；38.15 ~ 36.41 14C kaB.P.（949 ~ 903 cm）气候环境逐步改善，降水量增加，地表过程从风沙盛行转化为湖泊开始发育，并形成额济纳盆地最近一次大面积持续高湖面演化状态；36.41 ~ 31.73 14C kaB.P.（903 ~ 780 cm）气候暖湿，有效湿度大，湖泊处于高水位阶段；31.73 ~ 22.79 14C kaB.P.（780 ~ 482 cm）期间，古湖泊水位有所下降，气候有明显的波动，但仍维持在较高的水位上，湖区环境仍为暖湿气候；22.79 ~ 17.3714C kaB.P.（482 ~ 304 cm）气候开始变干变冷，湖区有效湿度在持续减小，湖泊面积萎缩、水位下降，环境恶化；17.37 ~ 14.00 14C kaB.P.（304 ~ 178 cm），湖泊退出研究点，风沙盛行，但其间存在短暂气候事件，造成暂时性流水沉积；14 ~ 4 14C kaB.P.（178 ~ 0 cm）湖泊开始再度扩张、水位有所上升，湖水开始变淡，但在晚期（62~ 0 cm）气候又一次发生转变，有效湿度减小，形成干旱气候环境，湖泊开始萎缩、直至消失。湖区成为戈壁－干盐湖相沉积。\n（3） 通过额济纳古湖小狐山剖面与腾格里沙漠区以及柴达木盆地察尔汗湖贝壳堤剖之间相应时段古湖泊演化记录的对比分析表明，三个不同区域的古湖泊演化十分相似。腾格里沙漠区古湖泊形成于42 ~ 20 kaB.P.，在35 ~ 21 kaB.P.期间，气候温和湿润，形成高湖面，在21 ~ 18.8 kaB.P.这段时期，该区域气后开始恶化，湖泊缩小，到18 kaB.P.前后湖泊退出研究区；察尔汗贝壳堤剖面揭示古湖泊在39.5 ~ 35.2 kaB.P.出现高湖面后，气候发生变化使湖水开始咸化，直到33.2 ~ 27.4 kaB.P.气候好转，湖泊演化到最鼎盛期，之后气候恶化，湖泊退缩，在17.1 kaB.P.湖泊因气候巨变而快速蒸发直至消失；在独立年代学研究结果可以看出，额济纳古湖的存在、演化及消亡与腾格里沙漠区及察尔汗贝壳堤剖面是可以对比的，同时，结合青藏高原在该时段存在众多高湖面的地质证据，表明了大区域古湖泊与气候环境变化的同步性。进一步为末次冰期间冰段我国青藏高原与西北地区为温暖湿润的气候环境并出现大湖期研究提供参考资料。 |
| 英文摘要 | Based on the particular factors of geological structure, sea-land distribution and atmospheric circulation, the environment of western inner Mongolia, China is semi-arid, drought and very eco-weak. In this area, the environment change quickly and are sensitive to the global changes, also human activity. However, a large number of geological features, sedimentary fancies and palaeontological evidence prove that the environment at the mid and late stage of late Pleistocene was different from the present, especially the precipitation was significant higher than the modern. So there were many palaeolakes in the arid area of the northwest China, and even became large lakes. Scientists are interesting in the phenomenon and reasons of the rapid evolution of the environment. The study area about the Global Change Research is becoming the research focus. Ejina Basin which is in the western Inner Mongolia of China, is one of the typical inland arid region. So studying the climate change and paleoenvironment in Ejina Basin is helpful to understanding of the arid region of northwest China's response to the global change. It has a very important theoretical value to do further research of the north-west arid zone of climate change.\n Based on above, the article select the XHS section as the research object, through testing indicators of organic carbon, organic nitrogen, inorganic carbon, the stable oxygen isotope, carbon isotope and grain size in the sediment, the article try to discuss the significance of these indicators. Combining with accurate age sequence, We reconstruction the environment changes history of the palaeolake in Ejina Basin during the late Pleistocene. And the study in this article has the main conclusions are as follows:\n(1) In the sediment of the palaeolake in Ejina Basin, the organic matter content is closely related to the lake development and climate features, and it is an effective proxy of the climat changing. The resules show that the organic matters in the sediments was mainly composed of algae and vascular plants formed during the palaeolake evolution, and the indicator is mainly reflecting the palaeolake primary productivity. The carbonate content in the sediments as one of the main material component the palaeolake, it also can reflect the sedimentary characteristics and the environmental evolution process because the content of authigenic carbonate was controlled by the water temperature and biomass. The carbon isotope is main reflecting the vegetation types and their biological productivity of the hydrographic basin. The oxygen isotope indicates the changes of the palaeolake water temperature and humidity effective. In the XHS section, it was found that when the TOC content is higher than 0.15% and that of TN is higher than 0.015%, the sediments are lacustrine deposits, otherwise are eolian (sandy) accumulations, so these indicators have a good correlation with sedimentary facies. \n(2) According to the TOC, CaCO3 contents, δ13C and grain size variations of the sediments, and the lithofacies of the studied section, the climate change and paleolake evolution history of the studied section can be divided into six stages: Before 31.73 14C ka B.P. (> 949 cm), it was a cold and dry. Between 38.15 and 31.73 14C ka B.P. (949 ~ 780 cm), the climate in the study area was warmer and wetter, and the lake level was high. From 31.73 to 22.79 14C ka B.P. (780 ~ 482 cm), the climate was still warm and wet and the paleolake level was high, but with strong fluctuations and decreases of the lake level. The climate was deteriorated and the water level decreased obviously between 22.79 and 17.37 14C ka B.P. (482 ~ 304 cm). From 17.37 to 14.00 14C ka B.P. (304 ~ 178 cm), the effective humidity of the study area reduced strongly and the paleolake retreated beyond the site of the study section, mobile sands were prevailing during the period which implied a cold and dry climate. From 14 to 4 14C ka B.P. (178 ~ 0 cm), the paleolake appeared and the lake level rised again but did not reach the height as before. The environment deteriorated abruptly around 4 14C ka B.P. and since then, the climate changed to cold and dry till the paleolake disappeared.\n(3) On the comparison the regional correlations of the XHS section, Qaidam Basin and Tengger desert, it shows a similar evolution patter because in all areas the palaeolake level started to increase and lake areas started to advance. The paleaolake in Tengger was formed between 42 and 20 kaB.P., with a substantial increase of the temperature and precipitation, especially precipitation, and resulted in high lake level from 35 to 21 kaB.P., then the paleaolake was studying to decrease accompanied by the climate changed to arid and cold. The Shell Bar section revealed the salt lake Qarhan in the Qaidam Basin appeared high lake level between 39.5 and 27.4 kaB.P., except the period of 35.2 to 33.2 kaB.P., then the palaeolake began to salinize, reduce. The palaeolake vaporized rapidly since 27.4 kaB.P., and disappeared in the end. The climate is reconstructed in all areas show that it was warm and humid between 35 and 21ka BP, with a substantial increase of the temperature and precipitation, especially precipitation, and resulted in high lake levels in all areas. The study results from the separated geological evidences prove that paleaolake in such different areas not only posses a similar evolution pattern but also started synchronously, and combine with the evidence of many geological evidences of high lake in Qinghai-Tibet Plateau. In sum up, it evidently imply the climate change resulted from the regional changes which links to global changes, providing new datas to understanding the mechanisms of the climate change. |
| 中文关键词 | 额济纳盆地 ; 小狐山剖面 ; 湖泊沉积物 ; 湖泊演化与环境 |
| 英文关键词 | Ejina Basin The Xiaohushan section lacustrine sediments lake evoluntion and environment change |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院南京地理与湖泊研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286772 |
| 推荐引用方式 GB/T 7714 | 杨伦庆. 内蒙古西部额济纳古湖小狐山剖面有机质与碳酸盐组成及其古环境意义[D]. 中国科学院南京地理与湖泊研究所,2009. |
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