Active methanogenesis during the melting of Marinoan snowball Earth

Guangliang Wu,Haoxiang Pei,Xianguo Lang,Tianzheng Huang,Bing Shen,Haoran Ma,Decan Tan,Zhouqiao Zhao,Jian-Ming Zhu,Meng Ning

doi:10.1038/s41467-021-21114-6

Abstract

Geological evidence indicates that the deglaciation of Marinoan snowball Earth ice age (~635 Myr ago) was associated with intense continental weathering, recovery of primary productivity, transient marine euxinia, and potentially extensive CH4 emission. It is proposed that the deglacial CH4 emissions may have provided positive feedbacks for ice melting and global warming. However, the origin of CH4 remains unclear. Here we report Ni isotopes (δ60Ni) and Yttrium-rare earth element (YREE) compositions of syndepositional pyrites from the upper most Nantuo Formation (equivalent deposits of the Marinoan glaciation), South China. The Nantuo pyrite displays anti-correlations between Ni concentration and δ60Ni, and between Ni concentration and Sm/Yb ratio, suggesting mixing between Ni in seawater and Ni from methanogens. Our study indicates active methanogenesis during the termination of Marinoan snowball Earth. This suggests that methanogenesis was fueled by methyl sulfides produced in sulfidic seawater during the deglacial recovery of marine primary productivity.

Highlights

Geological evidence indicates that the deglaciation of Marinoan snowball Earth ice age (~635 Myr ago) was associated with intense continental weathering, recovery of primary productivity, transient marine euxinia, and potentially extensive CH4 emission
High primary productivity and marine euxinia are evidenced by the abundant deposition of syndepositional pyrite in the topmost of Nantuo Formation throughout the Yangtze Block, South China
Sulfur isotopic modeling suggests that high δ34Spy values and high pyrite content result from active microbial sulfate reduction (MSR) in seawater, generating an episode of oceanic euxinia prior to cap carbonate precipitation[7]

Summary

Introduction

Geological evidence indicates that the deglaciation of Marinoan snowball Earth ice age (~635 Myr ago) was associated with intense continental weathering, recovery of primary productivity, transient marine euxinia, and potentially extensive CH4 emission. The CO2 accumulation generated a supergreenhouse condition that resulted in the rapid meltdown of ice on the Earth’s surface[8] Such a high atmospheric CO2 level would trigger intense continental weathering, resulting in the global precipitation of cap carbonate[9]. Sulfur isotopic modeling suggests that high δ34Spy values and high pyrite content result from active MSR in seawater, generating an episode of oceanic euxinia prior to cap carbonate precipitation[7]. Another event that might occur during deglaciation is massive CH4 emission. Geological evidence of deglacial CH4 emission includes sporadic occurrences of extremely low (

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Conclusion