Knowledge Resource Center for Ecological Environment in Arid Area
| 柴达木盆地43~8 Ma河湖相沉积的碳酸盐、蒸发盐矿物记录与古环境研究 | |
| 其他题名 | Carbonate and Evaporite mineral records during 43-8 Ma from the lacustrine sediments at Dahonggou, North Qaidam Basin, and implications for paleoenvironment |
| 顾宁 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 杨石岭 ; 姜文英 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 摘 要目前，许多指标都记录了新生代亚洲气候环境演变的事件，但不同指标反映的事件起止时间和机制存在很大分歧，因此建立时间跨度长、连续性好的区域新生代气候记录仍是当前研究的重点。柴达木盆地位于青藏高原东北部，新生代时期记录了气候环境演化和青藏高原隆升的信息，是研究新生代亚洲气候变化的理想区域。本研究从矿物指标入手，首先通过对现代湖泊表层沉积物矿物组成、湖泊水化学和气候条件的调查，获取碳酸盐-蒸发盐矿物序列沉淀和湖泊水化学、气候参数的定量关系，然后将这一发现运用到柴达木盆地新生代沉积的矿物组合分析中，以重建柴达木盆地43~8 Ma期间古气候演化历史。对我国北方夏季风边缘带86个现代湖泊表层沉积物的调查显示，方解石、白云石和蒸发盐（石盐、石膏和芒硝）是干旱、半干旱和半湿润地区湖泊的主要自生矿物。自东向西，随着降水量的逐渐减少，湖水Mg/Ca比、pH值、电导率和离子浓度逐渐增大；方解石最先沉淀，其次是白云石，最后是蒸发盐矿物（石膏、石盐），方解石、白云石和蒸发盐沉淀的东部界限和干燥度、年均降水量等值线的分布一致。通过自生矿物空间分布、湖泊水化学和气候参数的比较，我们进一步发现，湖泊的水化学主要受控于干燥度，而研究区的干燥度主要与降水量有关。据此，得到我国北方夏季风边缘带湖泊中控制方解石、白云石和蒸发盐矿物沉淀的干燥度指数阈值分别为3、4和5，降雨量阈值分别为600 mm、400 mm和350 mm。柴达木盆地大红沟地区的沉积相、矿物和孢粉记录共同揭示了该地区43.5~8.5 Ma期间气候环境演化历史，共分为三个阶段：（1）43.5~21 Ma间气候干湿交替，主要证据是：湖泊环境和荒漠环境交替出现，指示干燥度指数>5的石盐和指示干燥度指数>3的方解石交替出现，相对喜湿的阔叶树花粉和喜干的藜科花粉交替出现。推测这一时期柴达木盆地受副热带高压带和古亚洲季风交替控制，在副热带高压带控制下气候干旱，古季风加强时段气候相对湿润。（2）21~13 Ma期间气候湿润，主要证据是：指示静水环境的湖泊纹层出现，石盐出现频率减少，方解石出现频率增加，相对喜湿的温带阔叶树花粉和蕨类水龙骨孢子增加。这一时期柴达木盆地受中新世全球气候变暖的影响，变得温暖湿润。（3）13~8.5 Ma期间气候干旱，主要依据是：沉积物以冲积扇相沉积为主，表明周围山体抬升，湖泊萎缩，大红沟地区变为山前冲积平原；风成砂沉积再次发育且出现大量石盐；喜干的藜科植物花粉增加。推测该时期青藏高原北部加速抬升，一方面使得东亚冬季风增强，另一方面则阻挡了从南部运移过来的水汽，造成柴达木地区气候变干。 |
| 英文摘要 | AbstractCenozoic climate and environment events in Asia have been recorded by various proxies yet the timing and mechanisms of these events remains controversial. Regional continuous climate records which cover a long time span are still in urgent demand for a better understanding of the Cenozoic climate change. The Qaidam Basin, located in the northeastern Tibetan Plateau, is an ideal region to study the Cenozoic climate changes for it recorded both the environment change and tectonic uplift history of the Tibetan Plateau. In this work, we first investigated mineral assemblages of surface sediments and lake water chemistry from 86 modern lakes in northern China, and then established the quantitative relationships between mineral formation, lake water chemistry, and climate. Finally these findings were applied to the mineral analysis of a Cenozoic sedimentary record from the Qaidam Basin to reconstruct the climate history during 43~8 Ma. The mineralogical analyses of the surface sediments of 86 modern inland lakes in the East Asian monsoon region demonstrate that calcite, dolomite, and evaporite minerals (gypsum and halite) are the main authigenic minerals in lakes in arid, semiarid, and sub-humid environments. From east to west, lake water Mg/Ca ratio, pH, conductivity, and ionic concentration increase with decreasing annual precipitation; calcite appears first in the surface sediments, followed by dolomite, and finally by evaporite minerals such as gypsum and halite. The eastern boundaries of the distribution of calcite, dolomite, and evaporite minerals are consistent with the distribution of isohyets of aridity and annual rainfall. Comparison of mineral distribution, water chemistry and climate factors demonstrates that the lake water chemistry is mainly controlled by aridity, which is causally related to the annual precipitation. Therefore, the aridity indexes of 3, 4, and 5 are the thresholds for the formation of calcite, dolomite, and evaporite minerals in these lakes, with corresponding annual rainfall of 600 mm, 400 mm, and 350 mm, respectively. The chronological data, lithology, mineral assemblages and pollen records for the Dahonggou section indicate that three main environmental stages occurred in the Qaidam Basin during 43.5~8 Ma. (1) During 43.5~21 Ma, the climate underwent alternations of wet and dry periods as is indicated by the alternations of lacustrine and aeolian deposits, halite (which is indicative of aridity index of >5) and calcite (which is indicative of aridity index of >3), broadleaf tree pollen (which prefer wet climate condition) and xerophytic Chenopodiaceae pollen in the sediment. We interpret the climate change of this stage as being alternatively influenced by Subtropical High under which the regional climate is dry and Eocene Asian monsoon which brings moisture to the Qaidam Basin from the south. (2) During 43.5~21 Ma, the climate became more humid and stable as is indicated by the occurrences of laminated lacustrine mudstone, the decreased and increased incidence of halite and calcite, the increase in temperate broadleaf tree pollen and Polypodiaceae spores which prefer wet climate condition. We speculate the warm and humid climate of this stage was a regional response to the middle Miocene global warming. (3) During 13~8.5 Ma, dry climate prevailed. The lithoface changes from lacustrine facies to alluvial fan deposits which indicate the uplift of surrounding mountains and the depositional environment changing to a piedmont alluvial plain. The aeolian deposits appear again with large amount of halite. The percentage of Xerophytic Chenopodiaceae pollen increased. We speculate that the uplift of Tibetan plateau strengthened the winter monsoon and blocked the moisture transported from the south, which led to the aridification of the Qaidam Basin. |
| 中文关键词 | 新生代 ; 气候 ; 碳酸盐 ; 蒸发盐 ; 半定量 ; 沉积相 ; 孢粉 ; 柴达木盆地 |
| 英文关键词 | Cenozoic climate carbonate evaporite sedimentary facies pollen Qaidam Basin |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地质与地球物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287670 |
| 推荐引用方式 GB/T 7714 | 顾宁. 柴达木盆地43~8 Ma河湖相沉积的碳酸盐、蒸发盐矿物记录与古环境研究[D]. 中国科学院大学,2016. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [顾宁]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [顾宁]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [顾宁]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
