The Great Oxidation Event preceded a Paleoproterozoic "snowball Earth"

Area of Science:

• Paleoproterozoic Earth history
• Geochemistry
• Climate science

Background:

• The temporal relationship between the Great Oxidation Event (GOE) and the first "snowball Earth" glaciation is unclear.
• This uncertainty hinders understanding the causality between atmospheric changes and ancient climate shifts.
• Sulfur isotope mass-independent fractionation (S-MIF) and mass-dependent fractionation (S-MDF) transitions are key indicators of the GOE.

Purpose of the Study:

• To precisely determine the timing of the S-MIF/S-MDF transition relative to "snowball Earth" glaciation.
• To assess the causal link between atmospheric oxygenation and ancient climate change.

Main Methods:

• Analysis of quadruple sulfur isotope measurements (δ³⁴S, ∆³³S, and ∆³⁶S) from Paleoproterozoic Seidorechka and Polisarka Sedimentary Formations.
• Integration of geochronological constraints for precise dating.
• Stratigraphic analysis of glacigenic deposits in relation to sulfur isotope signals.

Main Results:

• The S-MIF/S-MDF transition, indicating the GOE, occurred between 2,501.5 ± 1.7 Ma and 2,434 ± 6.6 Ma.
• This timing is consistent across different continents (Fennoscandia, North America, South Africa).
• Glacigenic deposits of the "snowball Earth" event are found above sedimentary layers showing S-MDF signals, confirming the GOE preceded glaciation.

Conclusions:

• The GOE unambiguously preceded the Paleoproterozoic "snowball Earth" glaciation.
• This temporal resolution rules out models where glaciation caused or preceded oxygenic photosynthesis.
• The findings clarify the drivers of Earth's oxygenation and ancient climate dynamics.