摘要
青海省湟水流域二级阶地形成于晚更新世,通过对其开展元素地球化学分析,可以有效探讨青藏高原东北缘第四纪末次冰期事件。湟水西宁段二级阶地细粒沉积物主要为岩屑砂,其主量元素含量与兰州更新统Q3黄土相近。样品投点于元素示踪物源三角图中,显示沉积物主要来源于长英质源区、上地壳、花岗岩以及黄土区域,并具有沉积物再循环趋势,说明研究区沉积物可能经历了二次搬运过程:上地壳(长英质源区)→风成沉积(黄土)→河流沉积,源区可能为柴达木沙漠。化学蚀变指数CIA值59~64,成分变异指数ICV值1.43~2.10,预示着湟水二级阶地沉积时期处于寒冷干燥环境,与前人对该地区的孢粉研究结果一致。在大地构造背景图解中,大多数样品落入大陆岛弧及活动大陆边缘物源区域内,说明研究区沉积物物源构造背景复杂,而柴达木地体南缘的东昆仑造山带具有明显的活动陆缘和岛弧属性,晚渐新世以来东昆仑造山带的主要构造隆升事件与亚洲内陆干旱化在关键时间点方面高度契合,因此推断研究区样品的初始源区主要来自于东昆仑造山带。
The secondary terrace of Huangshui watershed in the Qinghai province was formed in the late Pleistocene.Element geochemical analysis of the fine-grained sediments in the upper part of the terrace can effectively explore the last glacial event of the Quaternary in the northeastern margin of the Qinghai-Tibetan Plateau.The sediments are mainly lithic sand,and its major element content is similar to that of Lanzhou Pleistocene Q3 loess.The analysis reveals that the sediments are mainly come from the felsic source area,upper crust,granite and loess areas,and have a trend of sediment recycling,indicating that the sediments in the study area may have experienced a secondary transport process:from the upper crust(felsic source area)to aeolian sediment(loess)to fluvial sediment,and its source area might be the Qaidam Desert.The chemical alteration index CIA value is from 59 to 64,and the composition variation index ICV value is from 1.43 to 2.10,indicating that the secondary terrane of Huangshui River was in a cold and dry environment during the deposition period,which is consistent with the previous sporopollen studies in this area.In the geotectonic background analysis result indicates that the tectonic background of sediment source of this study area is complex,and the East Kunlun orogenic belt on southern margin of the Qaidam Craton has obvious active inlandal margin and island arc attributes.The major tectonic uplifting events in the East Kunlun orogenic belt since the late Oligocene are highly consistent with the key time points of the Asian inland drying evolution.Therefore,we conclude that the initial source area of the sediments should be the East Kunlun orogenic belt.
作者
唐书君
赵文强
杨庆坤
贾君
马强
陈慧娟
TANG Shujun;ZHAO Wenqiang;YANG Qingkun;JIA Jun;MA Qiang;CHEN Huijuan(Qinghai 906 Engineering Survey and Design Institute,Xining 810007;Qinghai Engineering Research Center of Geoenvironment Protection and Geohazard Prevention,Xining 810007;School of Tourism,Qinghai Minzu University,Xining 810007;Qinghai Bureau of Environmental Geology Exploration,Xining 810008;School of Earth Sciences,East China University of Technology,Nanchang 330013,China)
出处
《干旱区资源与环境》
CSSCI
CSCD
北大核心
2024年第10期91-100,共10页
Journal of Arid Land Resources and Environment
基金
青海九零六工程勘察设计院有限责任公司科技项目(2023-KJ-07)
中国地质调查局全国地质遗迹立典调查与评价项目(DD20221771)资助。
关键词
古环境
物源
主微量元素
二级阶地
湟水
paleo environment
provenance
major and trace elements
secondary terrace
Huangshui River
