According to the latest research, we learn from ScienceDaily:
Earth’s oxygen levels rose and fell more than once hundreds of millions of years before the planetwide success of the Great Oxidation Event about 2.4 billion years ago, new research from the University of Washington shows.
The evidence comes from a new study that indicates a second and much earlier “whiff” of oxygen in Earth’s distant past — in the atmosphere and on the surface of a large stretch of ocean — showing that the oxygenation of the Earth was a complex process of repeated trying and failing over a vast stretch of time.
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Now, a team led by Koehler has confirmed a second such appearance of oxygen in Earth’s past, this time roughly 150 million years earlier — or about 2.66 billion years ago — and lasting for less than 50 million years. For this work they used two different proxies for oxygen — nitrogen isotopes and the element selenium — substances that, each in its way, also tell of the presence of oxygen. Paper. (paywall) – Matthew C. Koehler, Roger Buick, Michael A. Kipp, Eva E. Stüeken, Jonathan Zaloumis. Transient surface ocean oxygenation recorded in the ∼2.66-Ga Jeerinah Formation, Australia. Proceedings of the National Academy of Sciences, 2018; 201720820 DOI: 10.1073/pnas.1720820115 More.
Oxygen on the early Earth: More potential plot twists than a long-running soap…
But if this find holds up, it could link up with detection of life forms very early in the planet’s history.
See also: Photosynthesis pushed back even further. Time to revisit the “Boring Billion” claim
Researchers: Extreme fluctuations in oxygen levels, not gradual rise, sparked Cambrian explosion Explanations of the dramatic Cambrian explosion of life forms (540 million years ago) are a cottage industry, with arguments about oxygen a staple of the discussion. At times, it feels like trying to understand World War II without allowing for the possibility that any intention underlay any of the events. Maybe that’s why the issues can’t be resolved.
Maverick theory: Cambrian animals remade the environment by generating oxygen
Did a low oxygen level delay complex life on Earth?
There was only a small oxygen jump
Animals didn’t “arise” from oxygenation, they created it, researchers say
Theory on how animals evolved challenged: Some need almost no oxygen
New study: Oxygenic photosynthesis goes back three billion years
Enough O2 long before animals?
Life exploded after slow O2 rise?