Temporal and spatial variations of high-resolution strontium, carbon, and oxygen isotopic chemostratigraphy at the end-Permian crisis boundary in South China

Abstract

Variable degrees of strontium, carbon, and oxygen isotopic perturbations related to the end-Permian mass extinction (EPME) were recorded from the Latest Permian (i.e., the Lopingian stage prior to the extinction event) to the Earliest Triassic recovery (i.e., the Induan stage), while the underlying causes for their temporal and spatial variations and marine paleoenvironmental indications were poorly understood. In this study, integrated high-resolution 87Sr/86Sr, δ13C, and δ18O proxies are presented across the Wuchiapingian/Changhsingian and Permian/Triassic boundaries within the stratigraphic framework calibrated with high-resolution conodont biostratigraphy and high-precision geochronology in three South China sections, i.e., the Liangfengya, the Meishan, and the Shangsi sections. High-resolution strontium isotopes revealed that the water-mass segregation and accelerated precipitation rate of strontium probably resulted in local heterogeneity and provincial features of 87Sr/86Sr values at short-time interval less than 1 Myr. This provincialism of 87Sr/86Sr values can serve high-resolution chemostratigraphy. Integrated δ13C and 87Sr/86Sr isotopes from the studied sections at the Wuchiapingian/Changhsingian boundary (WCB) revealed that spatial heterogeneity with respect to drift magnitudes and peak values of δ13C negative excursion was not associated with oceanic stratification or high terrestrial input, while the releasing of 13C-depleted CO2 by deep-marine volcanism could be a plausible cause. Moreover, integrated δ18O and 87Sr/86Sr isotopes indicated that the “cooling event” occurring at the WCB was a provincial event, which was influenced by water depth and marine volcanism. The integrated high-resolution 87Sr/86Sr, δ13C, and δ18O proxies confirmed that the oceanic stratification was an ultimate cause for shallow-to-deep-water δ13C gradient at the Permian/Triassic boundary (PTB), but having no link to paleoproductivity increase. The positive excursion of 87Sr/86Sr postdated negative shift of δ13C by ∼ 40 Kyr across the PTB from the studied intervals. This temporal chemostratigraphic variation revealed that terrestrial influx was not a major cause for negative excursion of δ13C. The shallow-to-deep-water 87Sr/86Sr gradient was observed across the PTB in the studied sections, which was probably caused by water segregation resulting from oceanic stratification and distances from high- or low-radiogenic strontium sources supplied by terrestrial input or marine volcanism.