青藏高原东北缘循化盆地中中新世—早上新世黏土矿物及其古气候意义  

Clay mineralogy of the Middle Miocene to Early Pliocene sediments in Xunhua basin, northeastern Tibetan Plateau, and its paleoclimatic implications

作　　者：胡飞 殷科[3] 姬凯鹏 刘钊 肖唐付 黄蔚 何翔 骆满生[6] 张克信[7] HU Fei;YIN Ke;JI Kaipeng;LIU Zhao;XIAO Tangfu;HUANG Wei;HE Xiang;LUO Mansheng;ZHANG Kexin(School of Environmental Science and Engineering,Guangzhou University,Guangzhou,Guangdong 510006,China;Guangdong Geologic Survey Institute,Guangzhou,Guangdong 510000,China;Faculty of Earth Sciences,China University of Geosciences,Wuhan,Hubei 430074,China;Hydrogeology and Engineering Geology Institute of Hubei Geological Bureau,Jingzhou,Hubei 434020,China;School of Gemological and Material,Hebei GEO Geosciences,Shijiazhuang,Hebei 430074,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan,Hubei 430074,China;Institute of Geological Survey,China University of Geosciences,Wuhan,Hubei 430074,China)

机构地区：[1]广州大学环境科学与工程学院,广东广州510006 [2]广东省地质调查院,广东广州510000 [3]中国地质大学地球科学学院,湖北武汉430074 [4]湖北省地质局水文地质工程地质大队,湖北荆州434020 [5]河北地质大学宝石与材料学院,河北石家庄050031 [6]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430074 [7]中国地质大学地质调查研究院,湖北武汉430074

出　　处：《地质学报》2024年第4期1291-1309,共19页Acta Geologica Sinica

基　　金：广州市博士后启动基金(编号624021-4);中国地质调查项目(编号DD20190370)联合资助的成果。

摘　　要：青藏高原东北缘古气候可能受控于全球变冷、青藏高原隆升及局地地形变化的影响。为解析气候演化过程及驱动因素,本文以青藏高原东北缘循化盆地西沟剖面作为研究对象,在已有古地磁年龄约束基础上,分析了中中新世—早上新世沉积物中黏土矿物的组成和微观形貌特征。结果表明,西沟剖面沉积物中黏土矿物主要由伊利石、蒙脱石、绿泥石和高岭石组成,其中伊利石含量最高,平均为59.3%;蒙脱石次之,平均为18.2%,绿泥石平均含量为12.3%,高岭石平均含量为10.2%。根据剖面中黏土矿物含量和比值的变化特征,结合循化盆地西沟剖面的沉积速率、孢粉记录、有机质碳同位素和沉积岩地球化学比值,并与深海氧同位素值(δ^(18)O)变化曲线对比,将循化盆地14.6~5.0 Ma气候环境演化划分为3个阶段:14.6~12.7 Ma,气候干冷期,与北半球冰盖扩展引发的全球性降温事件有关;12.7~8.0 Ma,气候相对温暖湿润期,可能与循化盆地周围山体隆升有关,即积石山在~12.7 Ma隆升至临界高度,成为西风带输送水汽的地形屏障,使得循化盆地内的降水增强;8.0~5.0 Ma,气候再次转向干冷期,该阶段气候的干旱化对应于青藏高原在8 Ma左右的快速隆升,高原进一步的隆升阻碍东亚季风西风带的暖湿气流向内陆的输送,从而引起区域干旱化。Global cooling,the uplift of the Tibetan Plateau,and local topography have long been considered the crucial factors influencing paleoclimate change in the northeastern Tibetan Plateau since the Cenozoic era.However,the leading role played by each of these factors remains unknown.In order to gain a better understanding of paleoclimate change and its controlling factors,we conducted a study on the micro-morphology and relative content of clay mineralogy in the sedimentary sequence of the Xunhua basin in the northeastern Tibetan Plateau,spanning from the Middle Miocene to the Early Pliocene.Our results show that the clay minerals deposited in the Xigou section of the Xunhua basin are comprised of illite,smectite,kaolinite,and chlorite.Illite is the dominant clay mineral,followed by smectite,while the kaolinite and chlorite contents are relatively low.Combined with the content variation of herb-bushwood,coniferous forest,and broadleaved forest in the palynological assemblage,as well as the clay minerals,organic carbon isotope,sedimentary rates of sedimentary sequence between Middle Miocene and Early Pliocene in the Xigou section from the Xunhua basin,andδ^(18)O isotope record from the global deep-sea,the paleoclimate evolution in the Xunhua basin can be divided into three stages:Ⅰ-relatively cold and dry period(14.6~12.7 Ma);Ⅱ-relatively warm and humid period(12.7~8.0 Ma);Ⅲ-cold and dry period(8.0~5.0 Ma).Based on regional geological evidences,the climate cooling and drying event that occurred between 14.6 Ma and 12.7 Ma aligns with a global cooling period triggered by the expansion of the Northern Hemisphere Ice Sheet.Our inference of sustained elevated humidity observed in the Xunhua basin at 12.7~8.0 Ma is considered to reflect changes in regional rainfall patterns related to orogenic uplift.The Jishi Mountain range reached a critical threshold elevation at around 12.7 Ma,becoming an orographic barrier to Westerlies-transported moisture and thus enhancing intensified precipitation within the Xunhua basin.Ho

关 键 词：中中新世—早上新世 黏土矿物 循化盆地 干旱化 全球变冷 青藏高原隆升 

分 类 号：P532[天文地球—古生物学与地层学]