Paleogene
    and Neogene are important coal forming periods around the world. The Paleogene
    coal accumulation basins in the eastern coastal provinces of China are parts of
    the global Tertiary coal accumulated zone beyond the Pacific Rim. For an
    example, in Qiongdongnan Basin, and Xihu Sag of East China Sea the thickness of
    coal-bearing deposition is more than one kilometer, which is incomparable for
    the Paleogene continental coal basins. The research shows that the coal
    accumulation basins in sea areas mainly consist of many sags. As a result of
    the deep burial depth, the degree of coal metamorphism is relatively high, so
    the coal-bearing strata become good hydrocarbon source rocks.