典型岩溶高原边缘夷平面沉积特征及古气候环境——以湘西洛塔及贾坝剖面为例  

Sedimentary and palaeoclimatic characteristics of planation surface at the edge of typical karst plateau:A case study of Luota and Jiaba sctions in Xiangxi

作　　者：吴亮君[1,2,3] 王璞珺 张晶[2,3] 辛存林[4] 容悦冰 陈伟海[2,3] 张远海 黄超[5] WU Liangjun;WANG Pujun;ZHANG Jing;XIN Cunlin;RONG Yuebing;CHEN Weihai;ZHANG Yuanhai;HUANG Chao(College of Earth Sciences,Jilin University,Changchun,Jilin 130061,China;Institute of Karst Geology,CAGS/Key Laboratory of Karst Dynamics,MNR&GZAR/International Research Center on Karst under the Auspices of UNESCO,Guilin,Guangxi 541004,China;Pingguo Guangxi,Karst Ecosystem,National Observation and Research Station,Pingguo,Guangxi 531406,China;College of Geography and Environmental Science,Northwest Normal University,Lanzhou,Gansu 730070,China;Survey and Monitoring Institute of Hydrogeology and Environmental Geology of Hunan Province,Changsha,Hunan 410003,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]中国地质科学院岩溶地质研究所/自然资源部,广西岩溶动力学重点实验室/联合国教科文组织国际岩溶研究中心,广西桂林541004 [3]广西平果喀斯特生态系统国家野外科学观测研究站,广西平果531406 [4]西北师范大学地理与环境科学学院,甘肃兰州730070 [5]湖南省水文地质环境地质调查监测所,湖南长沙410003

出　　处：《中国岩溶》2024年第2期239-271,共33页Carsologica Sinica

基　　金：国家自然科学基金(42001011);中国地质科学院基本科研业务费专项经费(JKYQN202365、2020015);广西自然科学基金(2022GXNSFBA035592);广西重大科技创新基地建设项目(2018-242-Z01);湖南湘西世界地质公园申报项目联合资助。

摘　　要：文章对云贵高原边缘洛塔期(洛塔剖面)和召市期(贾坝剖面)夷平面风化壳进行粒度、磁化率、孢粉等方面的研究,探索其沉积特征及古气候响应。结果显示:洛塔剖面和贾坝剖面风化壳都以黏土和不等粒砂为主,但洛塔剖面岩性和粒度变化比较明显,为杂色黏土质粉砂和粉砂质黏土互层,夹一层砂砾石;贾坝剖面岩性和粒度相对稳定,主要为粉砂黏土。洛塔剖面Mz、Md、SC/D值以及磁化率值整体较高,但变化幅度小且快,贾坝剖面Mz、Md、SC/D值以及磁化率值相对波动较大,由此推断两条剖面所揭示的沉积环境都整体湿润,但贾坝剖面显示出小的干燥波动,即洛塔期夷平面风化壳沉积时期气候为温暖湿润型,召市期夷平面风化壳沉积时期气候为温凉干燥型,这与孢粉中大量水龙骨属(Polypodium)、松属(Pinus)指代的气候意义相同。对比孢粉组合及前人资料,推测洛塔剖面风化壳可能为新近纪早期开始形成,该夷平面可能形成于中新世,而贾坝剖面可能形成于第四纪早期,该夷平面可能形成于更新世。The palaeoenvironment has an important influence on the formation and evolution of karst geomorphology,and the planation surface at the edge of the karst plateau is one of the important recorders.The Yunnan-Guizhou Plateau is an important karst plateau in China,on the southeast edge of which is located Xiangxi in Hunan Province-a deep cut platform and gorge development area.Xiangxi is also a combination zone of low mountains and middle mountains at the edge of the Yunnan-Guizhou Plateau,in which the high plain transits to the alluvial plain,with rich records of planation surfaces.These planation surfaces are characterized by rapid altitude changes,different weathering crust materials and different types of bedrock lithology.However,the weathering crust properties and palaeoclimate characteristics of these planation surfaces are still unclear.Therefore,we choose two weathering crusts representing the elevation of 1,400 m and 600-700 m of planation surfaces in Luota Period(Luota section)and Zhaoshi Period(Jiaba section)as study objects.In this study,conducting the inversion of palaeoclimate indicated by weathering crusts of planation surfaces through grain size,magnetic susceptibility and sporopollen analyses,we hope to provide more evidence for the development characteristics of planation surfaces and palaeoclimate evolution on the edge of the Yunnan-Guizhou Plateau.Results show that the weathering crust of Luota section is 5.0 m thick and can be divided into 5 layers.The lithology is mainly composed of humus,gravel layer,silt,clay,etc.The content of silt with sizes ranging from 5 to 50μm is the highest,accounting for 57.6%;the average content of clay is 41.9%;the sand content is the lowest,at 0.56%,all of which are fine sand.The weathering crust in Jiaba section is 3.5 m thick and can be divided into two layers.The lithology is mainly composed of humus,silty,clay and a small amount of gravel.The content of silt with sizes ranging from 5 to 50μm is also the highest,accounting for 54%;the average content of clay

关 键 词：湘西世界地质公园 夷平面 古气候 粒度 磁化率 孢粉 

分 类 号：P512.2[天文地球—地质学] P532