Paleoclimate and paleoceanographic evolution during the Permian-Triassic transition (western Hubei area, South China) and their geological implications

Abstract

Severe global climate change is proposed to be the major cause of the Permian-Triassic boundary (PTB) mass extinction, while details about the response process are still in debate. In this study, we present geochemical and pyrite morphological data from an Upper Permian-Lower Triassic shale succession in the Western Hubei Trough, northern South China. The stratigraphic evolutions of paleoclimate, paleoredox condition and paleosalinity are analysed. Our data support that regional tectonics, collision of the South China Craton and the North China Craton, may have played a major role in hydrographic and redox evolution of the Western Hubei Trough, suggesting anoxia may not be a worldwide cause of marine PTB biocrisis. On the other hand, an extensive comparison between marine and terrestrial successions supports that global warming in the Late Permian may have induced enhanced supply of freshwater to the ocean and the flooding of seawater across the boundary between marine and fresh to brackish waters due to sea-level rise, leading to dilution of seawater, while global cooling in the Permian-Triassic transition may have induced reduced supply of freshwater to the ocean, leading to increase of seawater paleosalinity. On the land, both global and regional climate changes may have controlled the freshwater supply to water bodies, leading to fluctuation of watermass paleosalinity. Our data support that anomalous changes of watermass paleosalinity triggered by paleoclimate changes may have played a role in the PTB biocrisis.