Chemostratigraphy and pyrite morphology across the Wuchiapingian-Changhsingian boundary in the Middle Yangtze Platform, South China

Separated mass extinction occurred at the beginning and the ending of the Late Permian, called end-Guadalupian and end-Permian mass extinctions, respectively. Palaeoenvironmental changes in the middle of the Late Permian could give more insights into the environmental causes for the Permian extinctions. In this contribution, we analysed carbonate carbon isotope and carbonate-associated-sulphate sulphur isotope compositions to constrain the carbon and sulphur cycles across the Wuchiapingian-Changhsingian boundary (WCB) at Yanglinqiao in Zigui in the Middle Yangtze Platform. Pyrite morphology and pyrite framboids size distribution were used to analyse redox conditions variations across the WCB. Our results show that an episodic euxinia event occurred across the WCB. This anoxic/euxinic event across the WCB was a global event, and was mainly caused by the upwelling during the cooling event. Both inorganic- and organic-carbon isotopic compositions show covariance of a negative shift across the WCB at Yanglinqiao and other places in South China. This carbon-isotopic negative excursion across the WCB was a regional carbon cycle perturbation and may be linked to the light-carbon input from the upwelling water mass. Although the seawater delta S-34 across the WCB recorded a negative excursion in two locations in South China, it reflects the riverine input of S-32-enriched sulphate and represent a regional signal. These environmental anomalies such as oceanic anoxia/euxinia, global carbon cycle perturbation, cooling, end of the Emeishan large igneous province movement across the WCB may have delayed the recovery from the end-Guadalupian mass extinction.

Automated summary

This study focused on the Yanglinqiao area in central China, where an episodic euxinia event occurred in the mid to late Late Permian. The carbon and sulfur cycles were significantly affected during this period, potentially influencing environmental conditions and biotic turnover. These environmental anomalies may have delayed the recovery from the late Guadalupian mass extinction.