青海湟水流域二级阶地细粒沉积物矿物组成特征及其沉积古气候  

Mineral composition and sedimentary paleoclimate of secondary terrace sediments in the Xining section of Huangshui River

作　　者：唐书君 赵文强 杨庆坤 贾君[1,2] 马强 陈惠娟 赖海青 Tang Shujun;Zhao Wenqiang;Yang Qingkun;Jia Jun;Ma Qiang;Chen Huijuan;Lai Haiqing(Qinghai 906 Engineering Survey and Design Institute,Xining 810007;Qinghai Engineering Research Center of Geoenvironment Protection and Geohazard Prevention,Xining 810007;Qinghai Bureau of Environmental Geology Exploration,Xining 810008;School of Tourism,Qinghai Minzu University,Xining 810007;School of Earth Sciences,East China University of Technology,Nanchang 330013)

机构地区：[1]青海九零六工程勘察设计院有限责任公司,西宁810007 [2]青海省地质环境保护与灾害防治工程技术研究中心,西宁810007 [3]青海省环境地质勘查局,西宁810008 [4]青海民族大学旅游学院,西宁810007 [5]东华理工大学地球科学学院,南昌330013

出　　处：《地质科学》2025年第1期125-137,共13页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：青海九零六工程勘察设计院有限责任公司科技项目(编号:2023-KJ-07)资助。

摘　　要：湟水流域位于青藏高原东北缘,其二级阶地孢粉组合和热释光年代学显示了晚更新世末次冰期特征,但针对沉积物矿物学方面的研究尚处空白。激光粒度分析指示样品主要为含黏土粗粉砂—极细砂,具有分选性好、极正偏特征,小于63μm的颗粒明显高于现代河流沉积物中悬移物质总体含量,概率累积曲线具有二段式特征,缺少推移总体。扫描电镜下石英颗粒形状多样,表面结构复杂。沉积物X-射线衍射(XRD)成分分析指出碎屑含量占比平均在61.2%左右,主要为石英、斜长石和钾长石;碳酸盐矿物为方解石,含量约18.6%;铁氧化物(针铁矿)含量极低,约1.4%;黏土矿物含量约17.9%。依据沉积物搬运距离与粒径变化关系,推测沉积物应该经历了风成+河流的二次搬运过程。石英及长石比值(Q/F)平均为3.0,代表沉积物成分成熟度较低。黏土矿物(Chl+It)/(Sme+Kln)含量比值平均为7.7,远高于陕西渭河盆地中新统至上新统沉积物(相对暖湿环境),指示了研究区在晚更新世Q_(3)阶段应处于干冷环境。The Huangshui of Qinghai Province is located in the Xining Basin,northeast margin of Qinghai-Tibet Plateau.Mineralogical characteristics of the fine-grained sediments of secondary terrace can be used to explore the material source and paleoclimate of Late Pleistocene.The sediments are mainly containing clay coarse silt and very fine sand,with good sorting and extremely positive bias characteristics.Particles smaller than 63μm are significantly higher in concentration than the overall suspended matter content in modern river sediments.The probability cumulative curve has a two-segment characteristic and lacks an overall transported component.Under scanning electron microscope,quartz grains exhibit diverse shapes and complex surface structures.The proportion of rock debris in the sediment is about 61.2%,of which quartz content is the highest,followed by plagioclase and potassium feldspar.The carbonate mineral is calcite with a content of 18.6%.The clay mineral content is about 17.9%.The content of iron oxide(goethite)is very low.Based on the relationship between the transport distance of sediments and changes in particle size,it is inferred that the sediments have undergone a secondary transport process involving both eolian(wind-deposited)and fluvial(river-deposited)processes.The average quartz to feldspar ratio(Q/F)is 3.0,and the compositional maturity is low.The average content ratio of clay minerals(Chl+It)(/Sme+Kln)is 7.7,which is much higher than that of the Miocene to Pliocene sediments in the Weihe Basin of Shaanxi Province(representing a relatively warm and humid environment).This indicates that the study area should have been in a dry and cold environment during the Late Pleistocene(Q_(3))stage.

关 键 词：沉积环境 物质来源 砂岩 湟水河 青海 

分 类 号：P311.2[天文地球—固体地球物理学]