Evolution of Marine Conditions and Sedimentation during the Permian-Triassic Transition in Chibi of Hubei Province

The Chibi section of Hubei Province was1ocated in the transitiona1 zone between the Yangtze Platform and the northern deep silicious basin during Late Permian and its specia1 paleogeographic settingled to the formation of a unique sedimentary sequence within the PermoTriassic interva1. Base on a comprehensive study of microfacies, fossils and pyrite framboids it is found that the evolution of the sedimentary environment of Chibi section can be divided into6 stages during the Later Permian Changhsingian to early stage of Ear- 1y Triassic Period, which are nearly oxidized deepwater platform margin siliceous sedimentary, normoxic gentle s1ope platform margin sedimentary, volcanic activity intensified and normoxic platform margin gentle s1ope deposition, severe anoxic sedimentary environ- ment, oxygen-depleted sedimentary environment and oxidizing environment of deposition after the mass extinction. The Chibi section was1ocated in the gentle s1ope environment platform margin away from theland withlimited impact fromland-erosion, so nutrients from volcanism may be the main reason to cause marine anoxia aftermath the mass extinction.