沣河西安段现代河流沉积特征及其沉积环境变化解译  

Study on sedimentary facies characteristics and sedimentary environment change of modern sedimentary body in Xi􀆳an section of Fenghe River

作　　者：张寰萌 郭岭[1,2] 方泽鑫 杨永祯 Zhang Huanmeng;Guo Ling;Fang Zexin;Yang Yongzhen(Department of Geology,Northwest University,Xi'an 710069;State Key Laboratory of Continental Dynamics,Northwest University,Xi'an 710069)

机构地区：[1]西北大学地质学系,西安710069 [2]西北大学大陆动力学国家重点实验室,西安710069

出　　处：《地质科学》2023年第3期1045-1062,共18页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:42130206,41302076)资助。

摘　　要：本文对沣河西安段现代河流沉积体的岩石类型、沉积相类型、沉积模式及气候变化进行了综合研究,并对该地区现代河流体系的Google卫星影像、实地勘察、样品采集以及地球化学元素含量及其比值进行分析。结果表明,西安沣河现代沉积体岩性主要为土黄色泥岩、灰白色砂岩及泥质粉砂岩和少量的浅灰色细砾岩系;识别出3种亚相,即河道充填亚相、河道边缘亚相、泛滥盆地亚相;4种微相,即河床滞留沉积、点沙坝、河口扇和泛滥平原;在垂向上发育有3套不同的沉积层序:下部层序具有反韵律特征,中部和上部表现为明显的正韵律沉积,指示了水动力先增大再逐渐减弱的过程;通过分析沉积物中Co、Cr、Cu、Ni、Rb、Sr、V、Zn和Zr等微量元素含量的变化,以及锶铜法(Sr/Cu)、钒镍法(V/(V+Ni))、钒铬法(V/Cr)、镍钴法(Ni/Co)和锶钡法(Sr/Ba),确定沉积时期的环境主体为干旱气候,伴有季节性降雨,水体呈弱氧化-氧化性的淡水环境。This paper makes a comprehensive study on the rock types,sedimentary facies types,sedimentary models and climate changes of the modern river sediments in the Xi􀆳an section of the Fenghe River.Through Google satellite images,field surveys,sample collection and geochemical element content and ratio analysis of the modern river systems in this area.The results show that the lithology of the modern river sediments in Xi􀆳an is mainly yellowish mudstone grayish white sandstone and argillaceous siltstone and a small amount of light gray fine conglomerate series;three subfacies were identified,namely,channel filling subfacies,channel margin subfacies and flood basin subfacies;four microfacies,i.e.riverbed retained sediments,point bar,estuarine fan and flood plain,and develop three sets of different sedimentary sequences in the vertical direction:the lower sequence has anti rhythmic characteristics,and the middle and upper parts show obvious positive rhythmic sediments,indicating the process of hydrodynamic first increasing and then gradually decreasing.By analyzing the changes of the contents of trace elements such as Co,Cr,Cu,Ni,Rb,Sr,V,Zn and Zr in sediments,as well as Sr/Cu,V/(V+Ni),V/Cr,Ni/Co and Sr/Ba,it is determined that the main environment during the deposition period is arid climate,accompanied by seasonal rainfall,and the water body is a weak oxidation‑oxidation freshwater environment.

关 键 词：现代沉积 沣河 沉积相 沉积层序 沉积环境 

分 类 号：P512.2[天文地球—地质学] TE122.2[石油与天然气工程—油气勘探]