陕北靖边丹霞地貌区红色砂岩地球化学沉积特征与古环境研究

陕北靖边波浪谷丹霞地貌区是近年来国内外地学界的新发现和持续关注点。论文通过野外地质调查、粒度分析,岩石地球化学分析等研究,探讨红色砂岩地球化学特征、沉积环境、物源性质等相关问题。研究表明:红色砂岩以中—细砂为主,SiO₂和Al₂O₃含量之和在85%以上,沉积环境为河湖相,为水动力中等,水面较浅的河流入湖三角洲河口区地带,而不具有目前一些学者通过宏观观察提出的该砂岩为沙漠相沉积特征。沉积阶段气温较高,存在暖干与暖湿的多次变化。地球化学分析表明红色砂岩地球化学类型为长石砂岩和亚长石砂岩,物源可能来自于盆地内部隆起或再旋回造山带所提供的富石英质沉积岩。

Geochemical characteristics and paleoenvironment of red sandstone in Danxia Landform area,Jingbian, northern Shaanxi

The Danxia landform area of Jingbian wave valley is a discovery and continuous focus in recent years.Based on the field geological survey,grain size analysis and rock geochemical analysis,this paper discusses the geochemical characteristics,sedimentary environment and provenance properties of red sandstone.The results show that: the red sandstone is mainly composed of medium fine sand,and the total content of SiO2 and Al2O3 is more than 85%.The sedimentary environment is fluvial and lacustrine facies.It is a delta estuary area with medium hydrodynamic force and shallow water surface.It does not have the sedimentary characteristics of desert facies proposed by some scholars through macroscopic observation.During the deposition stage,the temperature was higher,and there were multiple changes of warm dry and warm wet.Geochemical analysis shows that the red sandstones are mainly feldspar sandstones and sub feldspar sandstones.The provenance of the red sandstones may come from the quartz rich sedimentary rocks provided by the uplift or the recycle orogenic belt in the basin.