Li Menghan, Xu Yilun, Sun Lilin, Chen Jiubin, Zhang Ke, Li Dandan, Farquhar James, Zhang Xiaolin, Sun Ruoyu, Macdonald Francis A, Grasby Stephen E, Fu Yong, Shen Yanan
School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300350, China.
Sci Adv. 2023 Sep 8;9(36):eadh9502. doi: 10.1126/sciadv.adh9502. Epub 2023 Sep 6.
The Cryogenian Sturtian and Marinoan Snowball Earth glaciations bracket a nonglacial interval during which Demosponge and green-algal biomarkers first appear. To understand the relationships between environmental perturbations and early animal evolution, we measured sulfur and mercury isotopes from the Datangpo Formation from South China. Hg enrichment with positive ΔHg excursion suggests enhanced volcanism, potentially due to depressurization of terrestrial magma chambers during deglaciation. A thick stratigraphic interval of negative ΔS indicates that the nonglacial interlude was characterized by low but rising sulfate levels. Model results reveal a mechanism to produce the ΔS anomalies down to -0.284‰ through Rayleigh distillation. We propose that extreme temperatures and anoxia contributed to the apparent delay in green algal production in the aftermath of the Sturtian glaciation and the subsequent reoxygenation of the iron-rich and sulfate-depleted ocean paved the way for evolution of animals.
新元古代的斯图尔特冰期和马林诺冰期的雪球地球冰川作用夹着一个非冰川间隔期，在此期间首次出现了海绵纲生物标志物和绿藻生物标志物。为了理解环境扰动与早期动物进化之间的关系，我们测量了中国南方大唐坡组的硫和汞同位素。汞富集且ΔHg出现正向偏移表明火山活动增强，这可能是由于冰消期陆地岩浆房减压所致。一个厚地层间隔的负ΔS表明，非冰川间歇期的特征是硫酸盐水平较低但在上升。模型结果揭示了一种通过瑞利蒸馏产生低至-0.284‰的ΔS异常的机制。我们认为，极端温度和缺氧导致了斯图尔特冰期之后绿藻产生明显延迟，而随后富含铁且贫硫酸盐的海洋重新充氧为动物进化铺平了道路。
