Characteristics Of Jurassic Sedimentary Environment In The Dameigou Section Of The North Margin Of Qaidam Basin

Multiple regional and global major geological events have been recorded in Jurassic strata since the Mesozoic era in the North Margin of Qaidam Basin,Paleo-environment of the Jurassic strata has always been a hot focus in the scientific research and resource exploration.The article focuses on the Dameigou section of Jurassic in the North Margin of Qaidam Basin,Combined with previous research results,using the outcrop section measurement,sample collection and indoor sample analysis et el.Given a comprehensive analysis of Sedimentary characteristics and geochemical characteristics of the Dameigou section of Jurassic,Discussed the Characteristics of Sedimentary Environment of the Dameigou section of Jurassic in the North Margin of Qaidam Basin.Based on outcrop profile measurement,Jurassic strata in the area has been divided into the Lower Jurassic Xiaomeigou Formation and the Middle Jurassic Dameigou Formation and the Upper Jurassic Caishiling Formation.Combined with lithologic features and marker bed,at the same time,five sedimentary facies have been identified:fluvial facies,braided delta facies,alluvial fan,lacustrine facies,swamp facies.Sedimentary characteristics of the Dameigou section of Jurassic suggest that the grey-green siltstone and fuchsia mudstone interbedding-based of the third member of the Lower Jurassic Xiaomeigou Formation,showed a hot dry climate,which reflected a brief warming event of the late Lower Jurassic.The red siltstone,grey-green sandstone,fuchsia sandstone,fuchsia mudstone and siltstone,reddish brown siltstone based of the Upper Jurassic Caishiling Formation,which also showed a hot dry climate.Sedimentary characteristics indicated that climate was twice obviously dry and heat of the late Lower Jurassic and the late Middle Jurassic in the Dameigou section of the North Margin of Qaidam Basin.The characteristics of geochemical elements proved the main source rock was intermediate-acid volcanic rock,There was no obvious differentiation of the source components.And sedimentary rock though multiple cycles involved in the source rock this characteristics match with the main component of gravel in the field profile.The sediment from the Dameigou section of Jurassic in the North Margin of Qaidam Basin was developed in the oxygen-richsedimentary environment of fresh water.