Sedimentary characteristics and controls of the carbonate rocks during the deposition of the first and second members of the Shahejie Formation in the Bohai sea area

The lacustrine carbonate rocks occurred on a wide range of scales in the Bohai sea area during the deposition of the first and second members of the Shahejie Formation, and may be grouped into four sedimentary facies types, including the carbonate platform, carbonate ramp, subaqueous uplift and mixed siliciclastic-carbonate facies types. The shallow lacustrine organic bank and terrigenous clastic beach reservoirs are best developed in the horizons between the lake level and wave base. During the deposition of the first and second members of the Shahejie Formation, the Bohai sea area was then in the warm humid subtropical climates and enclosed saline and brackish environments. The palaeogeomorphological features and terrigenous supply capacity are believed to be the main controlling factors for the development and distribution of the carbonate rocks in the Bohai sea area.