Abstract:

The Early Ordovician at Huanghuachang,Yichang can be classified into four group lithofacies: water current genetic grainstone ; biogenic reef limestone; biochemical genetic stromatolithic limestone;polygenetic micrltic dolostone;marl and shale. These lithofacies consist offive kinds of lithofacies asso(ations: restricted platform,open platform, platform shoal,platform reef, neritic shelf factes associations. They constitute two lithofacies sequences in ascending order:carbonate rock platform lithofacies sequence and subsided platform lithofaciessequence.