ENVIRONMENTAL CONDITIONS DURING RECOVERY FROM THE END-PERMIAN EXTINCTION: COMPARATIVE ANALYSIS OF CARBON ISOTOPE DATA FROM CHINA, JAPAN, AND TURKEY

The causes of the end-Permian mass extinction remain unresolved. Numerous scenarios have been proposed to explain the extinctions and delayed Early Triassic recovery, many involving ocean/atmosphere chemistry change. The goal of this study is to obtain high resolution Late Permian through Middle Triassic C and Sr isotope data and to use these data to constrain environments associated with the extinction and biotic recovery.

High-resolution sampling of Panthalassic seamount carbonates in Japan reveals a carbon isotope stratigraphy similar to previous studies from South China and Tethys, with a series of excursions beginning with a negative excursion at the Permian-Triassic boundary and ending with a positive excursion peaking in the earliest Middle Triassic (Anisian). Data from Japan exhibit lesser magnitude excursions and lack a Late Griesbachian excursion observed in South China. The Late Griesbachian excursion in China may reflect local subaerial exposure and dolomitization. Absence of a Late Spathian excursion in one Japanese section resulted from a submarine hiatus as demonstrated by conodont biostratigraphy. Differences in excursion magnitudes between areas can be explained by different stratigraphic completeness or local oceanographic conditions. In both areas, large Early Triassic excursions are followed by stable values through the Middle Triassic.

Strontium isotope ratios (87Sr/86Sr) from South China and Turkey exhibit a dramatic increase from the latest Permian through Early Triassic, from 0.7068 to 0.7082, suggesting an increase of silicate weathering on land. The increase in 87Sr/86Sr is consistent with models of delayed recovery involving high pCO2. Although the carbon isotope excursions can be explained by a variety of proposed extinction models including methane clathrate release, or thermogenic methane release during Siberian traps eruptions, we prefer the later hypothesis because methane clathrate regeneration takes place at time scales too long to account for these changes. Under this hypothesis, episodic Early Triassic carbon release from sedimentary reservoirs during Siberian Traps volcanism drove C isotope excursions, fueled accelerated silicate weathering and an associated rise in 87Sr/86Sr, and delayed biotic recovery through impacts on climate and ocean chemistry.