Lithofacies palaeogeography of Carboniferous Xiaodushanian-Permian Zisongian Stage in Yingen-Ejin basin and its adjacent areas

Based on field geological research and laboratory study using a combination of methods, collected sedimentary petrologic characteristics, palaeontologic marker and sedimentary structures in the field investigation, in combination with results of geochemical analysis, the authors summarized sedimentary facies signs in the study area. The Carboniferous-Permian Amushan Formation(Ganquan Formation)in the study area was divided into six kinds of sedimentary facies, namely braided river delta, alluvial fan, offshore, carbonate platform facies, shallow continental shelf and marine volcanic facies, which were further divided into thirteen kinds of sedimentary subfacies, in which shallow continental shelf and offshore is the main area of the deposition, followed by carbonate platform facies, whereas braided river delta and alluvial fan are distributed only near the Dunhuang-Alxa-Langshan ancient land and Mazongshan-Guaizihu uplift zone, and marine volcanic rocks mainly occur at the center of the rift valley.