Ocean deoxygenation after the Sturtian Snowball

Area of Science:

• Paleoceanography
• Geochemistry
• Biogeochemical Cycles

Background:

• The end of the Sturtian 'Snowball' glaciation involved significant chemical weathering and carbon cycle shifts.
• Oceanic oxygen level responses to these post-glacial changes remain uncertain.

Purpose of the Study:

• To investigate ocean deoxygenation and redox dynamics after the Sturtian glaciation.
• To reconcile conflicting views on post-glacial ocean conditions.

Main Methods:

• Analysis of a carbonate-based multiproxy dataset from the Taishir Formation, Mongolia.
• Geochemical analysis to determine ocean redox states and nutrient limitations.

Main Results:

• Evidence of ocean deoxygenation followed by predominantly anoxic, nutrient- and sulfate-limited conditions.
• Identification of a recalcitrant dissolved organic carbon pool in the deep ocean.
• Transient oxidation pulses occurred within the persistent anoxic environment.

Conclusions:

• Post-glacial ocean redox dynamics were influenced by specific tectonic and climatic factors.
• Ocean anoxia likely delayed the evolution of obligate aerobes, including animals, until the Ediacaran Period.
• Delayed algal diversification may be linked to post-glacial eutrophication.