Sequence Stratigraphy Study on the Cabroniferous Strata in Sichuan,Yunnan,Guizhou and Guangxi

Key words: 
• sequence stratigraphy /
• time-space pattern /
• Carboniferous /
• Sichuan,Yunnan,Guizhou and Guangxi provinces

Abstract: The Carboniferous strata extensively distributes in Sichuan,Yunnan,Guizhou and Guangxi provinces. It has the characteristicse of clear stratigraphic division and correlation, plentiful sediment types and better outcrops. It is suitable to have the sequence stratigraphy research in these areas. This paper has focused on the accurate researches of the exposure sequence str atigraphy of the Carboniferous strata based on the detailed sedimentological stu dy and accurate stratigraphic division and correlation of the Carboniferous stra ta in Sichuan,Yunnan,Guizhou and Guangxi provinces with the aid of the theor y and studying means of the exposure sequence stratigraphy. Sequences are divide d mainly by the characteristics of the key boundary surfaces,regional correla tion,sedimentary facies sequence changes,parasequence stacking patterns,facies a ssemblage and sedimentary geochemistry. It has expounded in detail the outcrop signs of the sequence division and various boundary surfaces. The Carboniferous strata in the study area are divided into 10 third-scale se quences, which are named from sequence 1 to 10, with the upper series of Carboni ferous strata having 5 sequences and the lower series also. In the lower series of Carboniferous strata, Yanguan stage are composed of sequence 1 to 2, and Data ng stage from sequences 3 to 5. In the upper series, Huashiban stage are compos ed of sequence 6 and Dala stage of sequence 7, and Maping stage from sequence 8 to 10. According to the features of the bottom boundary surface, 10 sequences ar e classified into two sorts of sequences, which are type Ⅰ sequence (S1,S3,S6,S9,S10) and type Ⅱ sequence(S2,S4,S5,S7,S8). The bottom boundary surfaces of type Ⅰ sequence all have clear signs including the strong paleokarst,the different thickness eluvial facies,the strata disconti nutity,the immense changes of sedimentary patterns and traits,the regional rev ival of river,the disappearence and abrupt changes of organism evolution and the huge and sudden alternation of carbon,oxygen and strontium isotope values. On t he other hand, the bottom boundary surfaces of type Ⅱ sequence are character iz ed by the transient exposure,the weak erosion and the lithoface texture transfor mation. So it is discerned more difficultly than the bottom boundary surface of type Ⅰ sequence. This paper also has expounded in detail the sedimentary features of the first transgressive surfaces and condensed sections of sequences in the different sedi mentary environments and basins. It has summarized the sedimentary characteristi cs of the different system tracts in the different facies and basins. On the ba sis of these researches, this paper has probed the sequence correlation in the different sedimentary facies and basins from the ways of the sequence number s,boundary surface traits and system tract structures and has founded the time -space pattern diagram of the Carboniferous sequence strata in the study area.