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Barite, BIFs and bugs: Evidence for the evolution of the Earth's earliest hydrosphere

Created 17/10/2025

Updated 17/10/2025

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The presence of relatively abundant bedded sulfate deposits before 3.2 Ga and after 1.8 Ga, the peak in iron formation abundance between 3.2 Ga and 1.8 Ga, and the aqueous geochemistry of sulfur and iron together suggest that the redox state, and the abundances of sulfur and iron in the hydrosphere varied widely during the Archean and Proterozoic. We propose a layered hydrosphere prior to 3.2 Ga in which sulfate produced by atmospheric photolytic reactions was enriched in an upper layer, whereas the underlying layer was reduced and sulfur-poor. Between 3.2 Ga and 2.4 Ga, sulfate reduction removed sulfate from the upper layer, producing broadly uniform, reduced, sulfur-poor and iron-rich oceans. As a result of increasing atmospheric oxygenation around 2.4 Ga, the flux of sulfate into the hydrosphere by oxidative weathering was greatly enhanced, producing layered oceans, with sulfate-enriched, iron-poor surface waters and reduced, sulfur-poor and iron-rich bottom waters. The rate at which this process proceeded varied between basins depending on the size and local environment of the basin. By 1.8 Ga, the hydrosphere was, relatively sulfate-rich and iron-poor throughout. Variations in sulfur and iron abundances suggest that the redox state of the oceans was buffered by iron before 2.4 Ga and by sulfur after 1.8 Ga.

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Title Barite, BIFs and bugs: Evidence for the evolution of the Earth's earliest hydrosphere
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/81a6088e-15f6-497f-bf90-37e74705d9c5
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 22/04/2018
Geospatial Coverage Australia
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Barite, BIFs and bugs: Evidence for the evolution of the Earth's earliest hydrosphere". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/barite-bifs-and-bugs-evidence-for-the-evolution-of-the-earths-earliest-hydrosphere