The Ocean Chemistry Changes Associated With Two Mass Extinction Events In Permian

Two catastrophic mass extinction events took place in Permian, with the first crisis at Mid-Late Permian boundary termed end-Guadalupian mass extinction, and the second crisis at Permian-Triassic boundary termed end-Permian mass extinction. Numerous hypotheses have been proposed to explain these two mass extinction events. Among them, ocean chemistry changes linked to mass extinction events has been widely accepted. However, ocean chemistry changes in space and time and its relationship with mass extinction have not been resolved. Multiple sulfur isotopes especially the small deviations for △33S, can effectively constrain the ocean chemistry changes and provide the new insight into the role of environment in biological evolution. The thesis uses multiple sulfur isotopes to explore ocean chemistry changes in space and time and their relationship with two mass extinction events in Permian.In the study of using multiple sulfur isotopes to explore the oceanic chemistry changes during end-Guadalupian mass extinction, we observed a sulfur signal with negative △33S from end-Guadalupian successions both in South China and USA. According to the principles of sulfur biogeochemical cycles and S-isotopic fractionations, negative △33S can be produced by mixing pyrites produced from different settings during shoaling of sulfidic waters. Based on detailed biostratigraphy, our multiple sulfur isotopic data with negative △33S from end-Guadalupian successions in South China and USA coincided temporally with mass extinction, and therefore we suggest that shoaling of sulfidic waters may have play an important role in the end-Guadalupian mass extinction in global scales.In the study of using multiple sulfur isotopes methods to explore global ocean chemistry changes during end-Permian mass extinction, negative △33S values have been observed prior to, during, and after the end-Permian mass extinction from sections in Canada and Japan. Based on principles of sulfur biogeochemical cycles and S-isotopic fractionations, widespread shoaling of sulfidic waters may have played a critical role in end-Permian mass extinction and subsequent delayed recovery.