| 引用本文: | 余加川,黄新宇,王富东,景盛文,徐云周,周子健,李俊豪,黄国庆,赵学钦,董发勤,罗尧东.2025.九寨沟火花海钙华坝的沉积演化及其地质环境意义[J].地球环境学报,16(4):444-459 |
| YU Jiachuan,HUANG Xinyu,WANG Fudong,JING Shengwen,XU Yunzhou,ZHOU Zijian,LI Junhao,HUANG Guoqing,ZHAO Xueqin,DONG Faqin,LUO Yaodong.2025.he sedimentary evolution of tufa dam on the Sparkling Lake and its geological environ-mental significance in Jiuzhaigou[J].Journal of Earth Environment,16(4):444-459 |
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| 摘要: |
| 九寨沟景区具有举世罕见的“层湖叠瀑”景观和独特的钙华沉积地貌，钙华体在重建古气候古环境和记录极端地质事件等研究中越来越受到重视。以2017年“8·8”九寨沟地震中揭露的“火花海”坝体决口剖面为研究对象，开展野外剖面测制、岩相学研究与稀土元素分析，结合地球物理探测与钙华年代学等手段，探明火花海坝体的沉积演化序列，厘定坝体沉积建造中蕴藏的地质与环境意义。火花海坝体决口处自底至顶由层状钙华、孔状生物模板钙华和植物碎屑模板钙华三类韵律式交替沉积而成；岩相学研究表明坝体钙华矿物成分主要为方解石；稀土元素地球化学研究表明钙华物质来源为区域碳酸盐岩岩溶地层；年代学研究获得了坝底炭质层AMS 14C年龄，结果为(1220±30) a，表明火花海坝体起源于全新世晚期；地球物理解译表明钙华体最大厚度约20 m。火花海坝体底部炭质夹层的形成可能与钙华沼泽化、季风加强或地震引发的土壤侵蚀等有关，具体还有待进一步研究。同时，火花海韵律式钙华沉
积，特别是旋回式生物碎屑钙华层与致密层状钙华，有望精确记录中全新世以来的季风作用，可为重建我国西南地区古水文气候变化提供关键地质档案。 |
| 关键词: 火花海 钙华湖坝 沉积建造 年代学 环境意义 |
| DOI：10.7515/JEE222076 |
| CSTR：32259.14.JEE222076 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41973053）；中国地震局地质研究所地震动力学国家重点实验室开放基金（LED2019B05）；中国科学院山地灾害与地表过程重点实验室开放基金（19zd3105）；自然资源部?/?广西岩溶动力学重点实验室开放课题（KDL & Guangxi202302） |
| 英文基金项目:National Nature Science Foundation of China (41973053); Open Fund of State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration (LED2019B05); Open Fund of Key Laboratory of Mountain Hazards and Surface Processes of China Academy of Sciences (19zd3105); Open Project of Ministry of Natural Resources/Guangxi Key Laboratory of Karst Dynamics (KDL & Guangxi202302) |
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| he sedimentary evolution of tufa dam on the Sparkling Lake and its geological environ-mental significance in Jiuzhaigou |
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YU Jiachuan, HUANG Xinyu, WANG Fudong*, JING Shengwen, XU Yunzhou, ZHOU Zijian, LI Junhao, HUANG Guoqing, ZHAO Xueqin, DONG Faqin, LUO Yaodong
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Institute of Land and Resources Utilization, School of Environment and Resources, Southwest University of Science and Technology, Mianyang 621010, China
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| Abstract: |
| Background, aim, and scope The Jiuzhaigou scenic spot has a rare landscape of “stacked lakes and waterfalls” and a unique tufa sedimentary landform. The tufa has been paid significant amount of attention in research that aims to reconstruct the paleoclimate and paleoenvironment and recording extreme geological events. Studies of the sedimentary evolution of the tufa dam can not only reveal the climatic and environmental information and geological events contained within it but also contribute to the restoration of post-earthquake landscapes and provide basic data for scientific conservation. Materials and methods The lake dam breach was taken as the research object, and a field profile survey, petrographic research and rare earth element analysis were carried out. These approaches were combined with geophysical explorations and analysis of the tufa chronology. Results The breach of the lake dam is regularly deposited with three types of tufa: layered tufa, porous biological template tufa and plant debris template tufa. Petrographic studies show that calcite is the main mineral component of the dam tufa. Studies of rare earth geochemical show that tufa is derived from regional carbonate karst strata. The AMS 14C age of the carbonaceous layer at the bottom of the dam was obtained by conducting a chronological study, and the result was (1220±30) a. A geophysical interpretation reveals that the maximum thickness of the tufa is about 20 m. Discussion The sediment of the lake dam is analyzed and interpreted from the vertical and horizontal dimensions. In the vertical section, it is formed by the synergistic accumulation of hydrodynamic conditions with biological colonization as the template and gravity water as the main factor. The lateral widening of the dam is mainly related to the many physical conditions and mechanisms that produce positive feedback of the dam locally. The rare earth element analysis shows that the travertine in the dam body and the carbonaceous layer at the bottom both inherit the material of the carbonate strata. Through two kinds of chronological studies, the dam body was re-accumulated and deposited on the basis of the old travertine present in the riverbed since the late Holocene, making the 14C dating result more reliable. Conclusions The lake dam body is formed by alternating depositions of layered tufa, plant debris template tufa, and porous biological template tufa. During the longitudinal deposition of the dam body, plants and biological debris act as templates; the dam body is preferentially deposited on the topographic bulge in the lateral direction and forms positive feedback, thus promoting the widening of the travertine dam body. The lake dam originated in the late Holocene, and the material source is carbonate strata in the karst system; meanwhile, its mineral composition mainly comprises calcite. The dam evolved on the basis of the old tufa in the riverbed. Recommendations and perspectives The formation of a carbonaceous interlayer at the bottom of the lake dam may be related to the swamping of the tufa, the strengthening of monsoons, or the soil erosion caused by earthquakes, etc. The steady tufa deposits in the Sparkling Lake are expected to accurately record monsoon activity since the Middle Holocene, constituting an important geological archive for reconstructing the paleohydro-climatic changes in Southwest China. |
| Key words: Sparkling Lake tufa dam sedimentary framework chronology environmental significance |
