Deglacial volcanism and reoxygenation in the aftermath of the Sturtian Snowball Earth

Menghan Li; Yilun Xu; Lilin Sun; Jiubin Chen; Ke Zhang; Dandan Li; James Farquhar; Xiaolin Zhang; Ruoyu Sun; Francis A Macdonald; Stephen E Grasby; Yong Fu; Yanan Shen

doi:10.1126/sciadv.adh9502

Deglacial volcanism and reoxygenation in the aftermath of the Sturtian Snowball Earth

Sci Adv. 2023 Sep 8;9(36):eadh9502. doi: 10.1126/sciadv.adh9502. Epub 2023 Sep 6.

Authors

Menghan Li¹, Yilun Xu¹, Lilin Sun¹, Jiubin Chen², Ke Zhang², Dandan Li¹, James Farquhar³, Xiaolin Zhang¹, Ruoyu Sun², Francis A Macdonald⁴, Stephen E Grasby⁵, Yong Fu⁶, Yanan Shen¹

Affiliations

¹ School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
² Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300350, China.
³ Department of Geology and ESSIC, University of Maryland, College Park, MD 20742, USA.
⁴ Department of Earth Science, University of California-Santa Barbara, Santa Barbara, CA 93106, USA.
⁵ Geological Survey of Canada, Natural Resources Canada, Calgary, Alberta T2L 2A7, Canada.
⁶ College of Resource and Environmental Engineering, Guizhou University, Guiyang 550012, China.

Abstract

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 Δ¹⁹⁹Hg excursion suggests enhanced volcanism, potentially due to depressurization of terrestrial magma chambers during deglaciation. A thick stratigraphic interval of negative Δ³³S_py indicates that the nonglacial interlude was characterized by low but rising sulfate levels. Model results reveal a mechanism to produce the Δ³³S 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.