The end-Permian mass extinction is considered to be the worst extinction event in Earth's history, with up to 81% of marine species wiped out in a very short period of time (61±48,000 years). Unraveling the mechanisms of extinction at the end of the Permian is crucial for understanding the relationship between environmental change and biological evolution. Previous studies have studied the short-term redox history of the late Permian paleooceans through geochemical index (e.g., biomarker compounds, iron components) and isotopes (e.g., uranium isotopes, etc.). In view of the scientific problems of the redox state and evolution of the late Permian paleoocean, postdoctoral fellow Zhang Min and academician Pan Yongxin of the Earth and Planetary Magnetic Field and Habitability Research Team of the Key Laboratory of the Institute of Earth and Planetary Physics of the Institute of Geology and Geophysics of the Chinese Academy of Sciences, together with Academician Shen Shuzhong of Nanjing University, researcher Deng Chenglong, associate researcher Qin Huafeng and postdoctoral fellow Hou Yifei of the State Key Laboratory of Lithospheric Evolution, as well as associate professor of Ocean University of China, carried out the "golden nail" of Zhejiang Coal Mountain in detail The environmental magnetic study of the profile has obtained new results on the evolution of the redox state of the paleooceanic at the end of the Permian.
图1 浙江煤山剖面环境磁学结果。 （a）磁化率（χ）；（b）非磁滞剩磁（ARM）；（c）饱和磁化强度（Ms）；（d）剩磁矫顽力（Hcr）；（e）非磁滞剩磁与饱和等温剩磁比值（ARM/SIRM1T）；（f）S-ratio0.3T；（g）铈异常（ΩCe）；（h）河流与地幔锶通量比值（FR/FM）
The results show that the changes in the magnetic indexes of the Changxing Formation and the Yinkeng Formation in the coal mountain profile can be divided into four sections (I.-IV.) from bottom to top (Fig. 1). In stage I., the magnetic minerals are dominated by magnetite and hematite, and in stage II.-IV., the magnetic minerals are dominated by magnetite, indicating that the paleomarine shallow marine environment changed from an oxidized state to an oxygen-poor hypoxic state, which occurred at about 252.8 Ma. Combined with the results of previous studies, such as thallium isotopes (Fig. 2a), global carbon isotopes (Fig. 2d), and biodiversity changes (Fig. 2c), it is shown that the perturbation of the end-Permian paleooceanic redox state occurred earlier than the extinction event. In addition, in stage II., the ratio of non-hysteresis remanence to saturated isothermal remanence (ARM/SIRM1T) showed a gradual decreasing trend (Fig. 1e), indicating a gradual increase in the size of magnetite particles. In stage III., the magnetic susceptibility (Fig. 1a), non-hysteresis remanence (Fig. 1b), and saturation magnetization (Fig. 1c) all showed the characteristics of first increasing and then decreasing, indicating that the magnetite content first increased and then decreased. Electron microscopy analysis showed that the magnetic minerals in the coal hill profile mainly came from terrigenous detrital input, and the terrigenous weathering index (Fig. 1h) showed similar characteristics to the changes in particle size and content of magnetic minerals, reflecting the change of continental weathering intensity.
Fig.2 Comparison of environmental, geological and biological events at the end of the Permian
In order to understand the driving mechanism of the evolution of the redox state of the paleooceans and the changes in the intensity of continental weathering at the end of the Permian, the research team comprehensively compared environmental, geological and biological events at the end of the Permian, and concluded that mantle plume and volcanic activity may have triggered the deoxygenation of the paleooceans. Large-scale volcanic eruptions and their resulting environmental effects exacerbated paleooceanic hypoxia and continental weathering (Figure 3). With the gradual weakening of volcanic activity, the paleooceanic redox state and terrestrial chemical weathering intensity gradually recovered. The results of this study provide key evidence that the global paleomarine hypoxia at the end of the Permian may be one of the main environmental factors directly responsible for the mass extinction of marine life.
研究成果发表于国际知名地学期刊CEE（章敏*，秦华峰，侯祎斐，何况，邓成龙，沈树忠，潘永信. Shifts in magnetic mineral assemblages support ocean deoxygenation before the end-Permian mass extinction[J]. Communications Earth & Environment, 2024, 5(1): 218. DOI: 10.1038/s43247-024-01394-8）。 研究受国家自然学科基金（41621004，42293280，92155203）资助。
Editor: Fu Shixu (East China Normal University)
Proofreading: Wan Peng