引用本文:张青青,黄菁华,姚 军,胡斐南,霍 娜,尚应妮,常闻谦,赵世伟.淳化黄土-古土壤序列黏土矿物分布特征及古环境意义[J].土壤学报,2018,55(5):1062-1073.
ZHANG Qingqing,HUANG Jinghua,YAO Jun,HU Feinan,HUO Na,SHANG Yingni,CHANG Wenqian,ZHAO Shiwei.Distribution of Clay Minerals of Chunhua Loess-paleosol Sequence and Its Paleoenvironmental Significance[J].Acta Pedologica Sinica,2018,55(5):1062-1073
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淳化黄土-古土壤序列黏土矿物分布特征及古环境意义
张青青,黄菁华,姚 军,胡斐南,霍 娜,尚应妮,常闻谦,赵世伟
中国科学院教育部水土保持与生态环境研究中心,黄土高原土壤侵蚀与旱地农业国家重点实验室;中国科学院大学,中国科学院教育部水土保持与生态环境研究中心,黄土高原土壤侵蚀与旱地农业国家重点实验室;西北农林科技大学,黄土高原土壤侵蚀与旱地农业国家重点实验室,西北农林科技大学资源环境学院,中国科学院教育部水土保持与生态环境研究中心,黄土高原土壤侵蚀与旱地农业国家重点实验室;西北农林科技大学,黄土高原土壤侵蚀与旱地农业国家重点实验室,西北农林科技大学资源环境学院,西北农林科技大学资源环境学院,西北农林科技大学资源环境学院,中国科学院教育部水土保持与生态环境研究中心,黄土高原土壤侵蚀与旱地农业国家重点实验室;西北农林科技大学,黄土高原土壤侵蚀与旱地农业国家重点实验室
摘要:
黄土-古土壤序列是记录第四纪气候环境变化的良好信息载体之一。以黄土高原南缘陕西省淳化黄土-古土壤序列为研究对象,通过X射线衍射法对黄土-古土壤剖面黏土矿物进行定性与半定量分析,调查不同土层黏土矿物相对含量及伊利石/绿泥石比值(I/C值)的变化规律,并结合伊利石结晶度的变化特征,探讨不同土层黏土矿物特征所对应的气候变化规律,揭示黄土高原南部地区在更新世时期的气候环境演变规律。结果表明:(1)淳化剖面黏土矿物的相对含量、I/C值以及伊利石结晶度IC值在反演古气候方面具有较好的指示性。(2)淳化剖面不同土层的黏土矿物类型基本相同,但其相对含量存在差异。在WL-3~S5阶段,即早更新世至中更新世中期,黏土矿物的组合类型为伊利石-蒙脱石-绿泥石-高岭石-蛭石,其中早更新世至中更新世早期(WL-3~L11阶段),伊利石相对含量相对偏低,气候以温凉为主,而中更新世中期(S10~S5阶段),伊利石相对含量上升,但蒙脱石、绿泥石含量均降低,气候相对温湿;在中更新世晚期(L5~S1阶段),黏土矿物的组合类型改变为伊利石-绿泥石-蛭石-高岭石-蒙脱石,以伊利石和绿泥石为主,气候较为干冷。黏土矿物类型及含量表明淳化地区从早更新世早期到中更新世晚期气候环境总体干冷化,并经历了温凉-温湿-干冷的变化过程。(3)I/C值以及伊利石结晶度IC值从剖面底部到顶部均经历了由小到大再到小的过程,它们与黏土矿物的含量所反映的气候变化规律一致。本研究有助于探索黄土高原南部地区在更新世时期的气候环境变化,为全面了解更新世黄土高原不同地区第四纪气候环境演变提供依据。
关键词:  淳化黄土-古土壤序列  黏土矿物  伊利石结晶度  古气候
DOI:10.11766/trxb201711200459
分类号:
基金项目:国家自然科学基金项目(31500449)、中国科学院西部之光项目(XAB2015B05)和中国科学院黄土高原土壤侵蚀与旱地农业国家重点实验室开放基金项目(A314021402-1515)
Distribution of Clay Minerals of Chunhua Loess-paleosol Sequence and Its Paleoenvironmental Significance
ZHANG Qingqing,HUANG Jinghua,YAO Jun,HU Feinan,HUO Na,SHANG Yingni,CHANG Wenqian and ZHAO Shiwei
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Research Center of Soil and Water Conservation and Ecological Environment, Chinese Academy of Sciences and Ministry of Education;University of Chinese Academy of Sciences,State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Research Center of Soil and Water Conservation and Ecological Environment, Chinese Academy of Sciences and Ministry of Education;State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest Agriculture and Forestry University,College of Resources and Environment, North West Agriculture and Forestry University,State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Research Center of Soil and Water Conservation and Ecological Environment, Chinese Academy of Sciences and Ministry of Education;State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest Agriculture and Forestry University,State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, North West Agriculture and Forestry University,State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, North West Agriculture and Forestry University,State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, North West Agriculture and Forestry University,State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Research Center of Soil and Water Conservation and Ecological Environment, Chinese Academy of Sciences and Ministry of Education;State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest Agriculture and Forestry University
Abstract:
【Objective】The loess-paleosol sequence on the Loess Plateau of China has been considered as an important information carrier recording changes in the global environment and climate of the Quaternary peroid. As weathering products of land surface, clay minerals are widely found in Quaternary sediments, and their paleoenviromental significance has also attracted more and more attention. It has been documented that the formation and transformation of clay minerals is closely related to climatic conditions. However, so far, few studies have been reported on characteristics of the clay mineral in loess-paleosol profiles in the southern part of the Loess Plateau. Besides, previous researches about paleoclimate evolution in the south Loess Plateau focused mainly on Holocene, with little attention to climate changes in the Pleistocene. 【Method】 In this paper, a typical loess-paleosol profile of the Loess Plateau was selected in Chunhua County, Shaanxi Province, south of the Loess Plateau as research object. With the aid of the X-ray diffraction method, qualitative and semi-quantitative analyses of the soil samples from different layers of the Chunhua loess-paleosol profile were carried out for analyzing relative contents of clay minerals, illite/chlorite ratio (I/C value) and illite crystallinity (IC value), as well as regularities of their evolutions, and further for relationships of the characteristics of the clay minerals in the profile with changes in paleoclimate and eventually, for regularities of the evolution of the paleoclimate and paleo-environment in the Pleistocene in the south Loess Plateau. 【Result】Results show: (1) The three indices, i.e. relative content of clay minerals, ratio of illite to chlorite (I/C values) and illite crystallinity (IC value) of the Chunhua loess-paleosol profile are good indicators to be used in reversion of paleoclimate changes in the Pleistocene. (2) All the soil layers of the profile had the same clay minerals, but relative contents of the clay minerals varied significantly from layer to layer. During the period from the early Pleistocene to the mid-middle Pleistocene (WL-3~S5), the clay minerals were composed mainly of illite-montmorillonite-chlorite-kaolinite-vermiculite, and this period could be divided into two stages according to the changes in relative contents of the clay minerals. From the early Pleistocene to the early middle Pleistocene (WL-3~L11), the relative content of illite was comparatively low while the relative content of chlorite was quite high, which indicates that a cool temperate climate prevailed in this period. However, in the mid-middle Pleistocene ( S10~S5), the relative content of illite increased, while the relative content of montmorillonite and chlorite decreased, which indicates that the climate was relatively warmer and more humid in this period. In the late middle Pleistocene (L5~S1), the composition of clay minerals turned to be of illite-chlorite-vermiculite-kaolinite-montmorillonite, and the relative contents of illite and chlorite increased, implying a dry-cold climate dominated this period. Therefore, the changes in relative contents of the clay minerals in the Chunhua loess-paleosol profile indicate that from the early Pleistocene to the late middle Pleistocene, the climate generally became dry and cold, and experienced changes from cool temperate to warm wet and to cold dry. (3) The ratio of illite to chlorite (I/C value) and illite crystallinity (IC value) also exhibited phased variations from the bottom to the top of the Chunhua profile, that is increasing first and then decreasing. The distribution of I/C ratio and illite crystallinity indicates that the climate in the Pleistocene underwent an evolution process similar to that of the clay minerals in relative content. 【Conclusion】All the findings in this research are found to be conductive to the exploration of changes in the climate and environment of the south loess-paleosol during the Pleistocene, and may serve a scientific basis for comprehensive exploration of changes in climate and environment of various regions of the Loess Plateau during the Quaternary period of the Pleistocene.
Key words:  Chunhua loess-paleosol sequence  Clay minerals  Illite crystallinity  Paleoclimate