Marine oxygen production and open water supported an active nitrogen cycle during the Marinoan Snowball Earth
Date
2017
Authors
Johnson, Benjamin W.
Poulton, Simon W.
Goldblatt, Colin
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Publisher
Nature Communications
Abstract
The Neoproterozoic Earth was punctuated by two low-latitude Snowball Earth glaciations. Models permit oceans with either total ice cover or substantial areas of open water. Total ice cover would make an anoxic ocean likely, and would be a formidable barrier to biologic survival. However, there are no direct data constraining either the redox state of the ocean or marine biological productivity during the glacials. Here we present iron-speciation, redox-sensitive trace element, and nitrogen isotope data from a Neoproterozoic (Marinoan) glacial episode. Iron-speciation indicates deeper waters were anoxic and Fe-rich, while trace element concentrations indicate surface waters were in contact with an oxygenated atmosphere. Furthermore, synglacial sedimentary nitrogen is isotopically heavier than the modern atmosphere, requiring a biologic cycle with nitrogen fixation, nitrification and denitrification. Our results indicate significant regions of open marine water and active biologic productivity throughout one of the harshest glaciations in Earth history.
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Citation
Johnson, B. W.; Poulton, S. W.; & Goldblatt, C. (2017). Marine oxygen production and open water supported an active nitrogen cycle during the Marinoan Snowball Earth. Nature Communications, 8(1316). DOI: 10.1038/s41467-017-01453-z