Environment

Oldest "oxygen oasis" marks Earth's first breath of fresh air

Oldest "oxygen oasis" marks Ea...
Sediment studies of the Pongola Basin, South Africa, have now found that the area was home to the earliest-known oxygen-producing organisms
Sediment studies of the Pongola Basin, South Africa, have now found that the area was home to the earliest-known oxygen-producing organisms
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Sediment studies of the Pongola Basin, South Africa, have now found that the area was home to the earliest-known oxygen-producing organisms
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Sediment studies of the Pongola Basin, South Africa, have now found that the area was home to the earliest-known oxygen-producing organisms

Carbon dioxide is the current villain in the story of atmospheric gases, but billions of years ago the bad guy was our friend oxygen. Although it's weird to think that we wouldn't be here today were it not for a global catastrophe, the Great Oxygenation Event actually wiped out most life on Earth at the time. This ramped up about 2.5 billion years ago, but now scientists have discovered signs of the oldest known "oxygen oasis" in South Africa, showing that the process started almost half a billion years earlier.

Our current atmosphere contains a healthy oxygen concentration of about 21 percent, but way back before the Great Oxygenation Event, Earth's air only contained about 100,000th of that amount. And that was just the way anaerobic organisms liked it – until cyanobacteria species started appearing and messing everything up. These were among the first photosynthesizing organisms, meaning they absorbed sunlight and emitted oxygen, and as they spread across the Earth over many millions of years they pushed ocean oxygen levels up so high it began escaping into the atmosphere in huge amounts.

This story has been pieced together through studies of ancient sediments. Certain sulfur signatures, which can only form in a low-oxygen environment, begin to vanish from the rock layers after a certain point, indicating increased oxygen in the atmosphere.

Although the process might have hit a tipping point around 2.5 billion years ago, the new study discovered the earliest signals of this large-scale oxygen production. From analysis of 2.97-billion-year old sediments in the Pongola Basin, South Africa, researchers from Universitaet Tübingen found high levels of sulfur isotopes – particularly sulfate – which indicates that the region was home to the earliest known oxygen-producing organisms.

"Sulfate is a form of oxidized sulfur," says Ronny Schönberg, co-author of the study. "A higher concentration of sulfate in the water indicates that sufficient free oxygen must have been present in the shallow sea of the Pongola Basin."

Although this area wouldn't have been the sole cause of the transition to an oxygen-rich atmosphere, the team says that the Pongola Basin is now the earliest known oxygen oasis – an ancient haven in the middle of a choking world.

The research was published in the journal Nature Geoscience.

Source: Universitaet Tübingen via Alpha Galileo

4 comments
Grumpyrelic
Imagine... Its 2 billion years ago and the anaerobic organisms announce global warming caused by those evil oxygen producing Cyano-Bacteria. Its a good thing the CB got locked up in our septic tanks where they can do no harm against oxygen breathers. I wonder if we can put the carbon tax people there too...
Koolski2
Hear, hear Grumpyrelic! What if "climate change" was the buzz word of the day back then.
Tom Swift
So basically life on earth was going pretty good until some polluters came along and totally messed up the environment; with oxygen......which resulted in virtually all life we see. oxygen pollutant or sustainer of life? CO2 pollutant or vital for life, lets ask a plant.
NoelFrothingham
Tom, any substance can be detrimental to life - any form of life - if present in quantities greater than the lifeform can tolerate.