Study on Outcrop Sequence Stratigraphy of the Carboniferous Strata in Anhui and Jiangsu Province,China

The Carboniferous system exposed from Anhui and Jiangsu provinces, has seven lithogenetic units. Based on outcrop sequence stratigraphic analysis with particular attention to the key surfaces or polyphase paleokarsts developed in the interruptions of sedimentation, nine types of lithofacies,twenty types of microfacies and eleven third order sequences in the Carboniferous system are recognized. The lower series of Carboniferous strata have six sequences, and the upper series have five.In the lower series of Carboniferous strata, Yanguan stage are composed of sequence 1 to 2, and Datang stage from sequence 3 to 6.In the upper series,Weining stage are composed of sequence 7 to 8,and Maping stage from sequence 9 to 11.According to the features of the bottom boundary surface, eleven third-order sequences are classified into two sorts of sequence ,which are type Ⅰsequence and type Ⅱ. The bottom boundary surface of type Ⅰsequence all have clear signs including the different thickness eluviums, the strong paleokarst, the strata discontinutity, the immense changes of sedimentary patterns and traits, the huge and sudden alternation of carbon and oxygen isotope values and the disappearence and abrupt changes of organism evolution. The third order sequences of S2, S3, S5, S6, S7 and S11 belong to I type of sedimentary sequence, and S1, S4, S8, S9 and S10 Ⅱ type. The third order sequences are absent at times. The characteristics and genesis of each third order sequences are described and discussed. The third order sequences in various paleogeographic units and sedimentary environment can be correlated. Sea level change rate and amplitude corresponding to these third order sequences are discussed.