Depositional Markers of Marine Transition Facies and Its Evolution of Member 1 of Shanxi Formation, Tabamiao Area, North Ordos Basin

Key words: 
• Tabamiao area /
• member 1 of Shanxi Formation /
• environmental feature /
• evolution

Abstract: Tabamiao area of Ordos basin from Taiyuan Formation in Upper Carboniferous to Shanxi Formation in Lower Permian underwent a prograding sedimentary evolution process, i.e. from tidal flat to lagoon marinecontinental transition delta. Previous studies drew different conclusions after studying the depositional environmental of member 1 of Shanxi Formation during the evolution. Some think it was the lake delta of the terrestrial facies, others believe that it was the deposition of marinecontinental transition delta,or the lake delta but influenced by the intermittent transgression. This paper, based on previous data, detailed core observation and petrology features, puts forward that member 1 of Shanxi Formation represents marine facies or the marinecontinental transition depositional environment, such as ①high maturity of the component and texture squartz-sandstone, ②micrite siderite stone, ③sea lily, foraminifer mudstone，④bauxite mudstone and ⑤crystal powder dolomite. Those marine facies depositional environmental features prove the depositional process of Tabamiao area member 1 of Shanxi formation is marine facies or marinecontinental transition depositional environment. Authors also discussed the spatialtemporal evolution characteristics of member 1 of Shanxi Formation depositional environment.