Carboniferous to Permian sequence stratigraphic framework of the Yunnan-Guizhou-Guangxi basin and its adjacent areas and global correlation of third-order sea-level change

The Yunnan-Guizhou-Guangxi basin is a passive continental-margin rift basin. After the Caledonian movement,it began to be pulled apart in the Devonian and continued to develop in the whole of the Late Paleozoic. Controlled by the contemporaneous faults,isolated carbonate platforms of varying size developed in the deep-water basin. Thus a special paleogeographic framework of platform-basin-hill-trough formed in the Yunnan-Guizhou-Guangxi basin and its adjacent areas. On the basis of the division into third-order sequences in different paleogeographic settings and their tracing and correlation in space,12 third-order sequences may be distinguished in the Carboniferous and Permian strata in the basin and its adjacent areas. They are equivalent to SQ14 to SQ25 of 25 Late Paleozoic third-order depositional sequences (SQ1 to SQ25,2～5 Ma). On the basis of two kinds of facies-change surface and two kinds of diachronism in stratigraphic records,a Carboniferous to Permian sequence stratigraphic framework may be established in the study region,which reflects the basic features of third-order sequences:ordering of facies sequences in space and synchroneity of environmental changes in time. The Carboniferous and Permian in the study region consist predominantly of a suite of carbonate rocks. In this suite of strata,three coal measures are developed in the land-connected platforms,and two suites of sponge reefs are developed on the margins of the land-connected platforms and in the isolated platforms,which make up sequence stratigraphy in Carboniferous and Permian successions that is greatly different from that in Europe and America.