Did an asteroid impact cause temporary warming during snowball Earth?

1Zhongwu Lan,1Ross N.Mitchell,2Thomas M.Gernon,3Adam R.Nordsvan
Earth and Planetary Science Letters 581, 117407 Link to Article [https://doi.org/10.1016/j.epsl.2022.117407]
1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
2School of Ocean and Earth Science, University of Southampton, Southampton SO22 4JR, UK
3Department of Earth Sciences, University of Hong Kong, Pokfulam, Hong Kong
Copyright Elsevier

The ca. 717 Ma low-latitude Sturtian “snowball Earth” glaciation lasted ∼56 Myr. However, sedimentological evidence for transient, open ocean conditions during the glaciation appears to contradict the concept of a global deep freeze. We demonstrate multiple lines of geologic evidence from five continents for a temporary, localized sea-ice retreat during the middle of the Sturtian glaciation, which coincides with one, perhaps two, asteroid impacts, and arguably more terrestrial impacts as inferred from the lunar impact record. The well-dated Jänisjärvi impact (ca. 687 Ma) is synchronous with repeated volcanic ash falls whose deposition is most parsimoniously interpreted to indicate a partially ice-free ocean. Temporary greenhouse warming caused by the vaporization of sea ice can explain localized glacial retreat within restricted seaways between these continents, where ice flow would have been constricted and sea ice thinnest before impact.


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