A Proposed Area for Study of Accessory Section and Point of Terrestrial Permian Triassic Boundary

After the establishment of the global stratotype section and point (GSSP) of the Permian~Triassic boundary (PTB), the definition of the accessory section and point (ASP) of the terrestrial Permian~Triassic boundary (TPTB) is now on the agenda. However, all good TPTB sections so far known have the following shortcomings: (1) the exact TPTB horizon is difficult to define paleontologically with high resolution, and (2) accurate correlation between marine and terrestrial PTBs is hard to attain. In order to enhance the understanding of the nature of the global life crisis in both the marine and terrestrial environments across the Paleozoic~Mesozoic transition, these shortcomings need to be addressed. In western Guizhou and eastern Yunnan, Southwest China, some fossiliferous PTB sections which include marine, paralic and terrestrial are well~developed, allowing bed~to~bed correlation of the PTB sequences. Fortunately, the marine PTB sequence in this area is almost the same as found at the Meishan Section, where the GSSP of the PTB is located, which may provide a reliable auxiliary marker for high~resolution demarcation of the TPTB. These features found in western Guizhou and eastern Yunnan make this area a good place to study the ASP of the TPTB, so we propose to study the ASP of the TPTB in this area.