| 引用本文: | 方艳秋，王子璇，王艺霖，汪卫国，符超峰，戴霜，胡惠，孔雪.2022.武威黄羊河剖面始新世湖相沉积物粒度端元组分及其沉积机制[J].地球环境学报,13(3):296-307 |
| FANG Yanqiu, WANG Zixuan, WANG Yilin, WANG Weiguo, FU Chaofeng, DAI Shuang, HU Hui, KONG Xue.2022.Grain size end-member components and sedimentary mechanism of Eocene lacustrine sediments in Huangyang River section of Wuwei Basin[J].Journal of Earth Environment,13(3):296-307 |
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| 摘要: |
| 为了解武威地区晚始新世湖相沉积粒度分布特征并提取古气候环境演变信息，本文利用一般化的Weibull 分布函数的参数化端元分析方法（EMMA），结合沉积相、谢帕德三角分类图以及中值粒径、标准偏差等粒度参数，对武威地区黄羊河剖面湖相沉积物粒度数据进行分析。结果表明：黄羊河剖面沉积物主要以细粉沙、极细沙和细沙为主。剖面沉积物各粒级组分垂向含量变化曲线分为三个阶段，沉积相依次对应氧化浅湖亚相 — 滨湖亚相 — 扩张湖亚相。结合各粒级组分含量垂向变化特征，剖面自下至上一定程度上指示气候由湿润转为干旱化的过程。剖面粒度数据反演得到3个端元（EM），其中EM1可能指示风力高空远距离悬移搬运来的黏土以及区域风力搬运的粉沙组分；EM2可能指示地表径流作用下河流水动力搬运入湖的沉积物；EM3 可能代表洪水作用沉积的粗颗粒跃移组分或湖泊经二次扰动再沉积的粗颗粒组分。 |
| 关键词: 湖相沉积 粒度分布 端元分析 沉积机制 黄羊河剖面 |
| DOI：10.7515/JEE222011 |
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| 基金项目:第二次青藏高原综合科学考察研究（2019QZKK0704）；国家自然科学基金项目（41972213） |
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| Grain size end-member components and sedimentary mechanism of Eocene lacustrine sediments in Huangyang River section of Wuwei Basin |
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FANG Yanqiu, WANG Zixuan, WANG Yilin, WANG Weiguo, FU Chaofeng, DAI Shuang, HU Hui, KONG Xue
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1. School of Earth Sciences, Lanzhou University, Lanzhou 730000, China
2. Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China
3. School of Earth Science and Resources, Chang’an University, Xi’an 710054, China
4. Northwest Institute of Nuclear Technology, Xi’an 710024, China
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| Abstract: |
| Background, aim, and scope The Wuwei Basin is located in the eastern Hexi Corridor on the northeastern of the Tibetan Plateau, which is situated at the hinterland of Asia’s inland arid region. The relatively few studies on the paleoclimate in this area have primarily focused on climate change and desert evolution since the Quaternary. Monsoon changes are reconstructed using the Gulang loess sequence to infer chemical weathering intensity, and the Shagou loess has revealed the influence mechanism of western desert evolution. However, studies on paleoclimate changes in the Early Cenozoic as well as reconstructions of the climate in this geologic period in this region are limited. To reconstruct climate change patterns since this period in the Wuwei Basin and decipher the drought process of Asia interior, this contribution employed the grain size distribution characteristics of the Late Eocene lacustrine sediments in the Huangyang River section of the Wuwei Basin and compared it with other aeolian sediments. This paper provides basic data for the interpretation of the drought process in the interior of Asia in the Hexi Corridor and the reconstruction of the paleoenvironment in this area. Materials and methods The grain size distributions of the sediments in the studied succession were measured using a Malvern Mastersizer 2000 laser instrument, the grain size data of the Huangyang River profile was imported using AnalySize software running in Matlab, and grain size components were separated using the parametric end-member analysis method to obtain potential paleoclimate information. Results Results show that the sediments in the Huangyang River section are primarily composed of fine silt sands, very fine sands, and fine sands. Sedimentary facies within this profile vary from bottom to top, and three grain size end-members are present, which represent different origins respectively. Discussion The grain size of EM1 primarily ranges from 1.0—40.0 μm, and the frequency curve of EM1 is similar to the frequency curve of the collected aeolian sediments. The grain size of EM2 ranges from 39.9—200.0 μm, and the frequency curve of EM2 is comparable to the grain size distribution of river sediments. The grain size of EM3 primarily ranges from 100.2—447.7 μm. The frequency curve of EM3 is analogous to that of EM2, but the mode grain size of the former end-member is approximately twice that of EM2. The overall grain size profile can be divided into three stages, based on the sedimentary facies transformations and the vertical variation of each grain size. From stage 1 to stage 2, the oxidized shallow lake subfacies transitions to the lakeside subfacies, and the coarse-grained components increase significantly, indicating a drying climate. From stage 2 to stage 3, the lakeside subfacies transitions to the expansion lake subfacies, the clay and fine silt content decrease significantly, and the sand and very fine sand content increase significantly, indicating a more arid climate. Conclusions Based on the variation in the end-member components, combined with the comparison of the frequency curves of the aeolian and aqueous origins in other areas as well as the division of the sedimentary facies in the study area, EM1 contains a clay component moved by high-altitude wind and a silt component moved by regional wind. EM2 may be related to sediments transportation into the lake by surface runoff. EM3 may represent coarse-grained saltation deposited by flooding or the lake after secondary perturbation. Recommendations and perspectives This study provides basic data for understanding the process of aridification in the Asian interior in the Hexi Corridor as well as changes of the sedimentary environment in the Eocene. |
| Key words: lacustrine deposition grain size distribution end-member analysis sedimentary mechanism Huangyang
River section |
