Sedimentary environment of Carboniferous-Permian Amushan Formation in Wulanaobao area of Urad Rear Banner,Inner Mongolia

Based on field section survey of Wulanaobao area in Inner Mongolia and an analysis of such sedimentary features as lithologic composition,stratigraphy,paleontology,sedimentary structure and petrology,the authors divided the section into three segments.The lower segment is braided river delta facies transformed into littoral facies,the middle segment is carbonate platform facies,and the upper segment is littoral and neritic facies.These sedimentary features suggest that in the Carboniferous-Permian Amushan period this area was located at the edge of the basin and experienced transformation from continental facies to marine facies,belonging to an onlap deposition process.In addition,the research on sedimentary facies and the determination of marginal facies prove that in the Carboniferous-Permian period Ejin Banner and its adjacent areas constituted a rift basin from the angle of sedimentology.The results of the research provide some evidence for the study of basin evolution and sedimentary facies.