Three-stage Formation of Cap Carbonates after Marinoan Snowball Glaciation Consistent with Depositional Timescales and Geochemistry
At least two global “Snowball Earth” glaciations occurred during the Neoproterozoic Era (1000-538.8 million years ago). Post-glacial surface environments during this time are recorded in cap carbonates: layers of limestone or dolostone that directly overlie glacial deposits.
Postulated environmental conditions that created the cap carbonates lack consensus largely because single hypotheses fail to explain the cap carbonates’ global mass, depositional timescales, and geochemistry of parent waters.
Here, we present a global geologic carbon cycle model before, during, and after the second glaciation (i.e. the Marinoan) that explains cap carbonate characteristics.
We find a three-stage process for cap carbonate formation: (1) low-temperature seafloor weathering during glaciation generates deep-sea alkalinity; (2) vigorous post-glacial continental weathering supplies alkalinity to a carbonate-saturated freshwater layer, rapidly precipitating cap carbonates; (3) mixing of post-glacial meltwater with deep-sea alkalinity prolongs cap carbonate deposition. We suggest how future geochemical data and modeling refinements could further assess our hypothesis.
Trent B. Thomas, David C. Catling
Comments: Main text is 30 pages double spaced. 8 figures, 1 table. Supplementary Material included at end of file. Published in Nature Communications
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph); Geophysics (physics.geo-ph)
Cite as: arXiv:2408.10179 [astro-ph.EP] (or arXiv:2408.10179v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2408.10179
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Journal reference: Nat Commun 15, 7055 (2024)
Related DOI:
https://doi.org/10.1038/s41467-024-51412-8
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Submission history
From: Trent Thomas
[v1] Mon, 19 Aug 2024 17:39:18 UTC (7,865 KB)
https://arxiv.org/abs/2408.10179
Astrobiology,