| 阿尔金新近纪红黏土粒度特征及古气候记录 |
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| 引用本文： | 黄丹青,杨利荣,李建星,岳乐平,潘峰,徐永,张余波.阿尔金新近纪红黏土粒度特征及古气候记录[J].沉积学报,2019,37(2):309-319. |
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| 作者姓名： | 黄丹青 杨利荣 李建星 岳乐平 潘峰 徐永 张余波 |
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| 作者单位： | 西北大学大陆动力学国家重点实验室,西北大学地质系,西安 710069;西北大学大陆动力学国家重点实验室,西北大学地质系,西安 710069;中国地质调查局西安地质调查中心,西安 710054;中国地质调查局西安地质调查中心,西安,710054 |
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| 基金项目： | 国家自然科学基金项目（40802039，201180025，41372020，41372036） |
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| 摘 要： | 为反演阿尔金新近纪红黏土记录的古气候、古环境信息,在已有的磁性地层学约束基础之上对剖面的粒度指标进行了系统的分析,并利用粒度端元模型(EMM)进行分解。结果表明,可分为三个粒度端元:端元1(众数粒径5.2μm)众数粒径集中分布于2～6μm,与北太平洋西风带粒度分布和中国黄土细粒组分的粒度分布相似;端元2(众数粒径20μm)呈负偏态非对称分布,众数粒径在32～16μm之间,为低空西风所搬运短距离做跃移运动的粉尘物质;端元3为双主峰分布,众数粒径57μm和2.5μm,代表着尘暴事件中风动力近源变化强度,反映混合沉积特征。其中在10.8～10.3 Ma、8～6 Ma、5.2～4.3 Ma、3.6～2.8 Ma端元1粒度含量呈减小趋势,端元2粒度百分含量呈逐渐增加趋势,中值粒径增大。13～2.6 Ma阿尔金红黏土记录显示内陆干旱化加剧事件经历了10.8～10.3 Ma、8～6 Ma、5.2～4.3 Ma、3.6～2.8 Ma四个阶段,结合前人对该剖面及邻区其他地质环境记录研究表明,亚洲内陆干旱化可能的起始时间为11 Ma左右,西风环流在本区占主导地位。全球变冷是内陆干旱化加剧的主导要素,青藏高原的阶段性隆升起着推动作用。
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| 关 键 词： | 阿尔金 红黏土 粒度 新近纪 端元模型 西风 |
| 收稿时间： | 2018-03-02 |
Grain Size Characteristics and Paleoclimate Records of the Neogene Red Clay in Altun,Western China |
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| HUANG DanQing,YANG LiRong,LI JianXing,YUE LePing,PAN Feng,XU Yong,ZHANG YuBo.Grain Size Characteristics and Paleoclimate Records of the Neogene Red Clay in Altun,Western China[J].Acta Sedimentologica Sinica,2019,37(2):309-319. |
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| Authors: | HUANG DanQing YANG LiRong LI JianXing YUE LePing PAN Feng XU Yong ZHANG YuBo |
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| Institution: | 1.State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China;2.Xi'an Center of Geological Survey, China Geological Survey, Xi'an 710054, China |
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| Abstract: | The Loess Plateau with eolian accumulation is the most widespread and most continuous area in western China. Based on the loess-paleosol sequence and research of the underlying red clay, a series of advances have been made in determining the inland aridity, the evolution of the paleo-monsoon, and its constraints on the uplift of the plateau. The eolian deposits found in the western part of China also provide indispensable data for inland aridity research. Based on previous field investigations, this paper takes the Neogene red clay in the Altun Mountain area on the northeastern margin of Qinghai-Tibet Plateau as the research focus, and based on the magnetic stratigraphy, substitution indices of paleoclimatology, such as magnetic susceptibility, particle size, etc, are used to reconstruct the palaeoclimate evolution process of the Altun area and explore its indicative significance for the aridity of the Asian interior. In this paper, grain size analysis is carried out on the basis of the existing magnetic stratigraphic constraints and the paleo-climatic environment information for the inversion of the Altun Neogene red clay records. The sediment grain size End Member Model (EMM) was decomposed. It can be divided into three End Members:EM1 (mode particle size 5.2 μm) has a concentration size distribution in 2-6 μm, grain size distribution in the westerlies of the North Pacific Ocean, and grain size distribution of Chinese loess. EM2 (Mode Size 20 μm) shows a negative skewed asymmetric distribution, and the Mode Size is between 32-16 μm. It is the dust material, which is moved by the low-level westerly over short distances. The distribution of EM3 is a double main peak, and the particle sizes are 57 μm and 2.5 μm, representing the intensity of near-source variation of wind-stroke dynamics during the duststorm event reflecting the mixed depositional characteristics. During 10.8-10.3 Ma, 8-6 Ma, 5.2-4.3 Ma, and 3.6-2.8 Ma, the particle content of End-Member 1 gradually decreased while the granularity percent content of End-Member 2 shows a gradually increasing trend and medium particle size. The Altun red clay records show that the intensity of the inland drought has gone through four stages:10.8-10.3 Ma, 8-6 Ma, 5.2-4.3 Ma, and 3.6-2.8 Ma. Combined with previous studies of other geological records for the profile and related geological records of the adjacent areas, the onset time of inland drought may be 11 Ma. The westerly wind is dominant in this area, global cooling is the leading factor of the intensification of inland drought, and the stage uplift of the Tibei-Plateau is promoted. |
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| Keywords: | Altun red clay grain size Neogene End Member Model westerly |
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