We studied the clay rocks around the Permian-Triassic boundary at the Daxiakou (大峡口) Section in Xingshan (兴山), Hubei (湖北) Province, China. All clay rocks are predominated by illitemontmorillonite (I/M) mixed-layer minerals, and high-temperature hexagonal bipyramid (HB) quartz and pyrite are contained in different abundances. Clay microspheres are even found in some beds. The results show that volcanic activity was very frequent in this area or in the neighboring areas during the Permian-Triassic transition though the intensity of eruption and the position of the eruption center might have varied during the period. The frequent volcanic activity should be at least one of the leading events to cause the momentous turnover of biota and the ecosystem during the great Permian-Triassic transition.
