Terrestrial events across the Permian–Triassic boundary along the Yunnan–Guizhou border, SW China

The border area between western Guizhou and eastern Yunnan Provinces in SW China is an ideal place to undertake research considering the terrestrial–ecological system evolution across the Permian–Triassic boundary (PTB). The study of plant and palynomorph fossils, clay minerals, inorganic geochemistry and sedimentary facies in this area enable us to interpret the events occurring at that time. The extinction pattern of the flora interpreted from megafloral and palynomorph data is demonstrated by a sudden decline of species numbers at the PTB after a long-term of gradual changes, followed by a delayed extinction in the basal Triassic. The two boundary claybeds (Beds 66 and 68 in the Chahe Section, beds 47 and 49 in the Zhejue Section) are considered to be volcanogenic. The inorganic geochemical anomalies occurred between Beds 63 and 69, Chahe Section and Beds 45 and 50, Zhejue Section. Sedimentary facies changed from channels of braided rivers, into flood plains of braided rivers, then to shallow lakes, reflecting a gradual transgression by lakes across the area. Our conclusions are that the mass extinction across the PTB in western Guizhou and eastern Yunnan was probably caused by the Siberian basaltic eruption episode and the siliceous volcanism in South China. These lithospheric events represented by volcanisms heralded a series of climatic and environmental events, giving rise to a catastrophe for the biosphere.