Knowledge Resource Center for Ecological Environment in Arid Area
| 180 ka以来青藏高原北部库木库里盆地沉积记录与环境演变 | |
| 其他题名 | Sedimentary record and paleoenvironment evolution since 180 ka in the Kumkol Basin, Northern Tibetan Plateau |
| 严永耀 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 苗运法 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 青藏高原北部（藏北）独特的地理位置和海拔高度，使其对气候环境的变化十分敏感，是开展古气候环境研究的重要地区。同时，该地区与亚洲内陆干旱区毗邻，富含粉尘沉积，亦是开展风沙活动及驱动机制研究的理想地区。对该区域晚第四纪以来的沉积物进行较高分辨率的指标分析，对认知过去气候变化、风沙活动及其驱动机制具有重要意义，并能为‘一带一路’和内陆地区可持续发展提供重要参考。然而，由于该地区环境恶劣、人迹罕至、交通极为不便，古环境和风沙活动的研究极其有限。本文拟通过对藏北高原库木库里盆地三个天然露头剖面（KM、KM-I和KM-II）进行综合分析，揭示该地区晚第四纪以来的气候变化与风沙活动信息。主要结果和结论有：（1）以KM和KM-I剖面的25个AMS 14C测年结果为参考，辩证分析测年结果可靠性。通过与冰芯和石笋记录进行耦合对比，得到三个剖面主要为180 ka以来沉积的较高分辨率的、较为连续的序列。（2）分析表明，粒度、色度和碳酸盐三种指标呈现出与冰芯和石笋记录耦合的特征。180-140 ka，该区主要为湖相沉积；140-120 ka，气候温暖湿润，湖面扩大；120-40 ka气候寒冷且波动频繁，湖面缩小；40 ka至全新世，气候干冷，湖泊收缩；全新世早中期，气候暖湿，湖面扩大。（3）将粒度中>63 μm粗颗粒含量作为衡量该盆地近源风沙活动（沙丘）指标，结果显示，在较小空间尺度上的不同位置，其含量变化差异显著。KM-II剖面（沉积于138-5 ka）记录的粗砂含量较高且与剖面的岩性记录相一致。结果表明：140-120 ka，风沙活动较弱；120-90 ka，风沙活动增强；90-40 ka，风沙活动的剧烈期和相对减弱期并存；40 ka至全新世表现为持续强烈的风沙活动。全新世早中期，气候暖湿，风沙活动减少。未来，我们将开展光释光等年代学研究，同时开展孢粉等指标分析来获取更高质量的年代控制和古气候环境变化记录，为认知上述科学问题提供进一步证据。 |
| 英文摘要 | The Northern Tibetan Plateau is sensitive to the climate because of its unique geographical position in the middle latitude Asia and altitude over 4000 m a.s.l., which is important for studying the paleoclimate and paleoenvironment change. Furthermore, due to adjacent to the arid Inner Asia the Tibetan Plateau must have experienced the sand and dust deposits especially in its northern margin during the late Quaternary. So, it is also sensitive to investigate the desertification (e.g., sand process) as well as driving forces behind it. The high-resolution proxies can help understand both the climate change and desert (sand land) activities, and provide an important guideline for human sustainable development in this area. However, because of the harsh environment, low content oxygen and almost inaccessible seasonal frozen soil, rare studies have been done.In this thesis, three outcrop profiles (KM, KM-I and KM-II) in the Kumukuli Basin were researched with combining field observation and laboratory experiment results (grain size as well as other proxies). Main results and conclusions are as follow:(1) According to the dating result of 25 AMS 14C samples in the KM and KM-I profiles, we made a dialectical analysis of its reliability with comparing with ice cores and stalagmite records, we gained a 180 thousand years (ka) deposition sequence of three sections.(2) For the paleoclimate and paleoenvironment, over one thousand samples of grain size, color index and carbonate were tested, which are correlated well with the the ice cores collected from the Guliya, Tibetan Plateau and Greenland and stalagmite records across the Asia. The results show that it was lacustrine evironment during 180-140 ka; climate was relatively warm and humid and the lake expanded in 140-120 ka; the climate was cold with frequent fluctuations and the lake dwindled during 120-40 ka; the climate was cold and dry and lake shrinkaged during 40 ka-early Holocene; the climate was warm and wet and lake expand in early and middle period of Holocene.(3) The contents of >63 μm in the quartz were used to measure the sand activities, we found that its content changed significantly in different profiles within the small spatial scales. The records of high content of coarse sand in KM-II profile is consistent with lithologic description. The results show that weak sand activities occurred in 140-120 ka, sand activities increased in 120-90 ka, the fluctuations were very similar to the profile record about sand dunes after 90 ka, severe and relatively less sand activities stage existed in 90-40 ka, continuous strong sand activities existed after 40 ka until to early Holocene, with the climate getting warm and wet, sand activities were controlled in early and middle Holocene.In future, we will continue to test more samples to get detailed chronology and sporopollen to obtain reliable paleoclimate changes, which will provide further evidence to cognitive the above problems. |
| 中文关键词 | 青藏高原 ; 晚第四纪 ; 指标记录 ; 环境演变 ; 风沙活动 |
| 英文关键词 | Tibetan Plateau Late Quaternary proxies paleoenvironment sand activities |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287971 |
| 推荐引用方式 GB/T 7714 | 严永耀. 180 ka以来青藏高原北部库木库里盆地沉积记录与环境演变[D]. 中国科学院大学,2017. |
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