Petrological characteristics and sedimentary environment in the southern Guizhou during the Late Carboniferous

The sedimentary environment changed frequently from carbonate terraces to basin in the Late Carboniferous in the south part of Guizhou. There were two lithologic combinations at the same time, namely the Nandan Formation (black limestones and siliceous shale limestones) and the Weining Formation (light gray limestones and dolomites). However, the sedimentary environment boundary and transitional characteristics between the two formations are not clear yet. The changes and transition characteristics of sedimentary facies in the southern Guizhou were analyzed based on previous research and the analysis of three typical wells, and combined with sedimentary sequence characteristics and rock combination characteristics. It was found that in the Late Carboniferous, the southern part of Guizhou experienced a retreat from basin facies to carbonate terraces facies, and there was a certain intersection and transition between various facies. A retreat process took place in the south-west direction. The appearance of the Weining Formation in the south indicated the shallowing of seawater and the closure of a rift trough.