Ladinian-Carnian Transgression and the Evolution of Yangtze Carbonate Platform in Southwestern Guizhou

There existed a large sea-level transgression at the southwest corner of Yangtze Block in southwestern Guizhou Province in late Middle Triassic (Ladinian-Carnian). The Yangtze carbonate platform, composed of shallow-water carbonates from the Late Proterozoic to the end of the Middle Triassic (about from 850 Ma to 236 Ma), was drowned by sea water during this transgression. Sedimentary facies were composed of deep-sea deposits (Zhuganpo Formation) such as nodular muddy limestone with pellets containing Neogondolella Polunathifornis and condensed section (Wayao Formation) with black shale and thin bedded (several cm) lime mudstone. Terrigenous clastic sediments including turbidite of Laishike Formation covered the Yangtze carbonate platform. The Yangtze Block, with a long evolutionary history of 630 my since Late Proterozoic, stopped growing. It is proposed that the drowning of the Yangtze carbonate platform was caused by the Ladinian-Carnian transgression in southwestern Guizhou Province, which was synchronous with the global sea-level changes.