Volcanics characteristics and LA-ICP-MS zircon U-Pb ages of clay rocks along Dongpan section of Guangxi

There exist Permian Dalong Formation and Lower Triassic Luolou Formation along Dongpan section crossing PTB. Dalong Formation contains Ophiceras sp., and Luolou Formation contains Ophiceras tingi Tien, suggesting that they are continuous. The evidence from paleontology indicates the PTB lies between 12-3 and 13-1A. There exists several claystone layers near the Permian-Triassic boundary, and the layers have obvious volcanic debris and tuffite structure. Geochemical data also show that claystones have volcanogenic features. U-Th-Pb zircon isotope data show a weighted mean 206Pb/238U age of 254.7Ma±3.7Ma, which represents the crystallization age of the protolith of the clays, roughly identical with the zircon U-Pb age 253.4Ma±0.2Ma of the bottom boundary of the Changhsingian period. It is also shown that strong volcanic eruptions occurred in this area.