Carboniferous Sequence Framework in Guizhou and Guangxi,Southern China

Carboniferous in Guizhou and Guangxi might be divided into four series, namely Yanguan, Datang, Weining and Maping. The Maping formation, traditionally regarded as the upper Carboniferous lithostratigraphic unit, is now considered to be an intersystem unit from Carboniferous to Permian. Hence, the top part of Carboniferous and the bottom part of Permian (Chuanshan Series) in Guizhou and Guangxi constitute a third order sedimentary sequence. In the study area, Carboniferous System and Permian Chuanshan Series form a second order tectonic sequence that contains 6 third order sequences. The bottom of the second order sequence is a nonconformity surface resulting from the principal episode of Ziyun epeirogeny, and the top surface is also a nonconformity surface caused by the principal episode of Qiangui epeirogeny. Strata of Carboniferous and Chuanshan Series have obviously different sedimentary features. Coal measures and relatively abundant dolomitic strata are developed in the connecting platform, strata of the isolated platform are marked by carbonate rock, strata of the inter platform ditch are mainly composed of dark fine grained sediments, and therefore the third order sequences with different peculiarities of facies succession are formed in different areas. Although time spans and peculiarities of various third order sequences are somewhat different, the processes of relative sea level change represented by these third order sequences remain synchronous on the whole. On the basis of biostratigraphy, the surfaces of third order sequences could be correlated and traced in space, the framework of sequence stratigraphy from Carboniferous to Chuanshan Series of Permian in Guizhou and Guangxi could be constructed in term of two types of facies changing surfaces as well as two kinds of diachronism in stratigraphic records.