The geologic settings of Chinese coal deposits

China has abundant coal resources, which are extensively developed in marine-influenced, continental, and transitional environments. The coal-bearing strata in China have complicated geneses and distributions. There were eight major coal-forming periods in China, namely the Terreneuvian, Mississippian, Pennsylvanian-Cisuralian-Guadalupian, Lopingian, Late Triassic, Early-Middle Jurassic, and Early Cretaceous Epochs, as well as the Palaeogene-Neogene Periods. The distributions of the coal-bearing strata formed during these different coal-forming periods displayed obvious regional and regularity characteristics. In accordance with their plate-tectonic settings and coal-bearing characteristics, the coal-bearing basins in China can be divided into six types. The coal-bearing basins that were formed during the Palaeozoic Era were mainly large epicontinental sea basins. During the early Palaeozoic Era, the shallow sea was the most important coal-forming sedimentary environment. In addition, coastal delta and delta-detrital coast systems were the most important coal-forming sedimentary environments in the late Palaeozoic Era. The coal-bearing basins that were formed during the Late Triassic Epoch were mainly offshore basins, and coastal, coast-delta, coastal alluvial, and coastal inter-mountainous plain environments dominated their coal-forming sedimentary environments. Coast-bay and lagoon-estuary systems comprised additional main coal-forming sedimentary environments. The coal-bearing basins that formed during the Early-Middle Jurassic Epochs were large- and medium-sized inland lake basins, in which alluvial-lake delta systems recorded the best coal formation processes, followed by lakeshore sedimentary environments. The coal-bearing basins that formed during the Early Cretaceous Epoch and Palaeogene-Neogene Periods were mainly small-sized continental basin groups. Coal-forming processes mainly occurred in the lake-delta swamp environments during lake siltation stages when the filling evolution of the lake basins occurred. In addition, this study proposed a new coal-forming process that occurs during transgression events. Finally, this study generally summarized the characteristics and evolution theories of coal-forming processes in China and especially focused on the characteristics of the evolution of coal-forming sedimentary environments.