Permian-Triassic Boundary Sections from Shallow-Marine Carbonate Platforms of the Nanpanjiang Basin, South China: Implications for Oceanic Conditions Associated with the End-Permian Extinction and Its Aftermath

Permian-Triassic boundary (PTB) sections from isolated carbonate platforms in the Nanpanjiang Basin of south China contain Upper Permian skeletal packstones with di-verse open-marine fossils overlain by a 7–15 m thick bound-ary horizon composed of calcimicrobial framestone con-structed by globular to tufted, calcified cyanobacteria simi-lar to Renalcis. The framestone contains interbeds of lime-grainstone with abundant thin-shelled bivalves and brachiopods. The overlying Lower Triassic strata contain microgastropod lime-packstones followed by a thick succes-sion of thin-bedded lime-mudstones. The PTB event horizon is interpreted to occur at the top of the packstone containing diverse, open-marine fauna and Palaeofusulina and coincident with the abrupt change to calcimicrobial framestone lacking Permian macrofossils.