Earth's great oxidation event

From the University of California – Riverside

Oxygen’s ups and downs in the early atmosphere and ocean

UC Riverside-led research team finds evidence for a dramatic rise in early oxygen about 2.3 billion years ago followed, more surprisingly, by an equally impressive fall

This is a carbonate rock in Zimbabwe used to trace sulfate levels in the Earth’s early oceans. Click to enlarge.

RIVERSIDE, Calif. — Most researchers imagine the initial oxygenation of the ocean and atmosphere to have been something like a staircase, but with steps only going up. The first step, so the story goes, occurred around 2.4 billion years ago, and this, the so-called Great Oxidation Event, has obvious implications for the origins and evolution of the first forms of eukaryotic life. The second big step in this assumed irreversible rise occurred almost two billion years later, coinciding with the first appearances and earliest diversification of animals.

Now a team led by geochemists at the University of California, Riverside challenges the simple notion of an up-only trend for early oxygen and provides the first compelling direct evidence for a major drop in oxygen after the first rise.

“Our group is among a subset of scientists who imagine that oxygen, once it began to accumulate in the ocean-atmosphere system, may have ultimately risen to very high levels about 2.3-2.2 billion years ago, perhaps even to concentrations close to what we see today,” said Timothy Lyons, a professor of biogeochemistry and the principal investigator of the project. “But unlike the posited irreversible rise favored by many, our new data point convincingly to an equally impressive, and still not well understood, fall in oxygen about 200 million years later.”

According to Lyons, this drop in oxygen may have ushered in more than a billion years that were marked by a return to low-oxygen concentrations at Earth’s surface, including the likelihood of an oxygen-free deep ocean.

“It is this condition that may have set the environmental stage and ultimately the clock for the advance of eukaryotic organisms and eventually animals,” he said.

Study results appear online this week in the Proceedings of the National Academy of Sciences.

“The time window between 2.3 and 2.1 billion years ago is famous for the largest and longest-lived positive carbon isotope excursion in Earth history,” said Noah Planavsky, a recent Ph.D. graduate from UC Riverside, current postdoctoral fellow at Caltech, and first author of the research paper.

He explained that carbon isotopes are fractionated during photosynthesis. When organic matter is buried, oxygen is released and rises in the biosphere. The burial of organic matter is tracked by the positive or heavy isotopic composition of carbon in the ocean.

“Some workers have attributed the carbon isotope excursion to something other than organic burial and associated release of oxygen,” Planavsky said. “We studied the sulfur isotope composition of the same rocks used for the carbon isotope analyses — from Canada, South Africa, the U.S., and Zimbabwe — and demonstrated convincingly that the organic burial model is the best answer.”

The researchers’ sulfur data point to high sulfate concentrations in the ocean, which, like today, is a classic fingerprint of high oxygen levels in the ocean and atmosphere. Sulfate, the second most abundant negatively charged ion in the ocean today, remains high when the mineral pyrite oxidizes easily on the continents and is buried in relatively small amounts in the oxygen-rich ocean.

“What is equally impressive is that the rise in oxygen was followed by a dramatic fall in sulfate and therefore oxygen,” Lyons said. “Why the rise and fall occurred and how that impacted the billion years or more of ocean chemistry that followed and the life within that ocean are hot topics of research.”

The research team is thrilled to have found strong chemical evidence for oxygen variability on the early Earth.

“The idea that oxygen levels at Earth’s surface went up and down must be vital in any effort to understand the links between environmental and biological evolution on broad, geologic time scales,” Planavsky said.


He and Lyons were joined in the study by Andrey Bekker at the University of Manitoba, Axel Hofmann at the University of Johannesburg and Jeremy Owens at UCR.

The NASA Exobiology Program supported this research. A National Science Foundation (NSF) Graduate Research Fellowship and a postdoctoral fellowship from the NSF Division of Earth Sciences covered Planavsky’s salary.

The University of California, Riverside ( is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California’s diverse culture, UCR’s enrollment has exceeded 20,500 students. The campus will open a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion. A broadcast studio with fiber cable to the AT&T Hollywood hub is available for live or taped interviews. UCR also has ISDN for radio interviews. To learn more, call (951) UCR-NEWS.

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October 23, 2012 1:16 pm

This is true the early atmosphere varied over time, it should come as no surprise. If one considers the vast Precambrian banded sedimentary, oxide iron ore deposits. The chemical composition of the atmosphere and water must have been widely variable. Hum, is this another case of the more things change the more they stay the same?

October 23, 2012 1:48 pm

Snowball Earth? A good smack from a big rock from outer space? The sun belched and killed everything off?
Something obviously happened – and it was so long ago it was caught up in some subsequent catastrophe.

October 23, 2012 3:22 pm

Hmm. I was under the impression that the banded iron ores, which vary between layers of hematite and magnetite (Fe2O3 and Fe3O4) and siderite (Fe CaCO3) were evidence of significant oscillations be oxidizing and reducing conditions in the early atmosphere, which I not Dennis Nikols mentions as well.

October 23, 2012 3:30 pm

If the moon was still active as a molten ball of cooling rock, where did all the outsourcing of gases go? is it possible that the Earth pulled in massive amounts of material from the early Moon to produce these chemical changes? they are talking about a window between 2.3 and 2.1 billion years ago and there is evidence that the Moon was last volcanically active 100 million years ago. I think it’s reasonable to think the moon had more activity 2.3 to 2.1 billion years ago, hypothetically, there was possibly a stream of material arriving on earth from the moon at one point and mixing with the atmosphere. Just a thought.

October 23, 2012 5:00 pm

My guess is that the oxygen originated in the earth’s fission georeactor core.

October 23, 2012 5:22 pm

Apparently the great oxidation event is mostly interpretation of limited data, as it turns out there isn’t an abundance of rocks formed during this period, at least that we know of. Maybe the whole period is full of stop starts due to competing processes, and there was no steady increase over a very long time.

James at 48
October 23, 2012 6:06 pm

The other long standing truism has been that the carbon cycle cannot ever sputter and essentially suffer a short sharp death. Of course after the subsequent die off of photosynthetic plants and all organisms dependent on them, the fungi would arrive, liberating lots of carbon and jump starting the great engine again.

October 23, 2012 6:18 pm

To be specific (prove me wrong) 2.1 billion years ago I think it was a Tuesday around 7:30 am, the sun began to rise above the horizon.

October 23, 2012 8:10 pm

I think I just had a brain cramp, if the wikipedia said:

Additionally the free oxygen reacted with the atmospheric methane, a greenhouse gas, triggering the Huronian glaciation, possibly the longest snowball Earth episode ever.

About the GOE, but if the oxygen oxydized the CH4, and thereby reducing the greenhouse gas CH4 and caused the longest snowball; shouldn’t the additional CO2 have warmed things up then, just like they are claiming is happening now?

October 23, 2012 8:11 pm

October 23, 2012 8:12 pm

Is there any proxy or paleo data for atmospheric pressure? I’ve seen the hypothesis that impacts/cosmic events might have blown some of Earth’s atmosphere into space etc, but all I find about prehistoric iatmospheric pressure are assumptions.

Bill Illis
October 24, 2012 5:11 am

Earth temps over the last 2.5 billion years from dC13. Each -5 dC13 here is about -15C. The first big Snowball Earth is evident enough although it was probably two separate events.
Oxygen chemistry is interesting. All the Oxygen around today has been on Earth since the beginning. It has just got recycled into different molecular arrangements over time. And Oxygen readily combines with other elements, and it strongly favors some over the others.
What was the early Earth Oxygen chemistry like before photosynthetic algae came along? We don’t really know where the Oxygen was. It hadn’t reacted completely with Iron and Methane until that time so it had to be in another fairly stable molecule. CO2? Where was it? This might answer the Faint Young Sun paradox. I haven’t heard this talked about before.

John Marshall
October 24, 2012 7:07 am

This event ties in with the Banded Iron Formations (1.8-2.2Ba) which changed ocean chemistry by removing soluble iron thus pushing ocean water towards that we know today, which have been fairly constant for at least 500Ma through varying atmospheric CO2 levels with very little change in ocean pH.
No new science but interesting nonetheless

October 24, 2012 10:19 am

Yes, and the reason the heavy isotope 13C is incorporated in the organic material causing the positive excursion is there wasn’t enough 12C, which the critters would have preffered, to go around.
13C is a proxy for biological competition for Carbon, and for temperature only indirectly to the extent temperature affects this competition.

October 24, 2012 10:48 am

When organic matter is buried, oxygen is released and rises in the biosphere. This setence is wrong. When organic mattter is buried, it becomes finally oxidised and Oxygen is consumed. Oxygen is released to the atmosphere through photosynthesis.

October 25, 2012 3:59 am

As oxygen started to be produced by the cyanobacteria, for a long time it was mopped up by oceanic Fe2 being precipitated as oxidised Fe3. After that it could build up in the atmosphere.
The link from Bill Illis:
shows that the Huronian ice age just over 2 billion years ago was the mother of them all. Maybe like other glacial epochs e.g. our current one, it was brought on by tectonic continental configuration. Then the dip in O2 could be secondary to this, less photosynthesis in a snowball earth. So reversed causality. Not reduced O2 causing the ice age. Climate scientists currently appear only capable of proposing atmospheric primary causes of anything in climate or geological history, a crushing intellectual straight-jacket.

michael hart
October 25, 2012 4:24 am

Sorry. No sale on the biogeochemistry carbon-isotope proxies.
When someone shows me a convincing description of the expressed proteins and associated biochemistry etc. of the dominant life-forms over two billion years ago [photosynthetic and otherwise], then I might be willing to start giving credence to assertions that observable kinetic and thermodynamic biochemical carbon isotope effects were similar then to what they are today, and potentially, maybe, perhaps, possibly, useful as proxies.
[Some people are rumoured to believe that living organisms change their biochemical nature over time in a process called evolution.]

October 25, 2012 5:28 am

The Great Oxigenation Event assumes oxygen ionized 2.4 billion years ago and thus became capable of bonding with hydrogen and other previously ionozed elements. Oxygen first ionized at it’s highest limit of 871.387 eV (NBS-34, Table 1, Col. VIII) and the decay rate would be 2.75 million years per electron volt. (2.4 / 871.387). When this rate is applied to calcium, the first of all the elements to ionize (5469.738 eV, Col XX) , that event would have occured over 15 billion years ago.
Either the Universe is older than we think or oxygen first ionized much sooner than 2.4 billion years hypothesized.

November 2, 2012 2:38 am

Paul Jackson says:
October 23, 2012 at 8:10 pm
I think I just had a brain cramp, if the wikipedia said:
Additionally the free oxygen reacted with the atmospheric methane, a greenhouse gas, triggering the Huronian glaciation, possibly the longest snowball Earth episode ever.
About the GOE, but if the oxygen oxydized the CH4, and thereby reducing the greenhouse gas CH4 and caused the longest snowball; shouldn’t the additional CO2 have warmed things up then, just like they are claiming is happening now?

I don’t think you have a clear picture of early Earth. Methane is a more powerful greenhouse gas than CO2, by a factor of 20 to 25 times more powerful. Methane reacting with oxygen would reduce the greenhouse effect, even though it makes CO2, if oxygen is available.
The early Earth suffered a collision that formed the moon and was molten until it cooled. That means the early Earth had large amounts of iron on it’s surface or located in the Earth’s crust. Eventually the Earth cools enough for liquid water to form. With rain comes weathering which releases more iron into the oceans. Life eventually appears and creates free oxygen, but life is limited to areas, because large amounts of iron are toxic. Life eventually overcomes the iron and then the oxygen is available to react with the methane.
The sun during the early Earth didn’t have the solar output it has today, but it was warm enough for life to get rid of the iron. Once the oxygen started reacting with the methane and reduced the greenhouse effect, the Earth cooled.
Methane, CO2, oxygen and nitrogen diffuse rather well in the atmosphere and it’s my understanding that lightning is also involved in oxidizing methane. Methane just can’t exist long in our atmosphere with oxygen. I think in our current Earth, methane is given a life expectancy of about 10 years. Water vapor doesn’t diffuse well in the atmosphere, so it stays close to the surface. Water has an affinity for itself and that’s why it gathers together to form clouds.

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