A mass that died around 2.05 billion years ago destroyed more than 80 percent of life and expels all mass extinctions – including the one who killed the dinosaurs.
In contrast to the large animals that became extinct at these other events, the newly recognized death involved small, simple microorganisms.
Researchers found evidence of dying in rocks from Canada, whose isotope ratios retain information about the environment when they were formed.
The death followed an increase in the atmospheric and oceanic oxygen levels of the earth that were accompanied by an increase in the abundance of life.
When the micro-organisms of that time used up their nutrients, however, their numbers had to fall back.
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A mass that died around 2.05 billion years ago wiped out more than 80 percent of life, wiping out all mass extinctions, including those who killed the dinosaurs. Pictured, barite-containing rocks from the Canadian Belcher Islands that date back to about 2 billion years ago
WHAT IS THE GREAT OXIDATION EVENT?
During the Great Oxidation Event, the atmosphere of the earth and the shallow oceans experienced a dramatic increase in the oxygen level.
This was accompanied by an increase in the abundance of the simple microbial life that lived at the time
The episode lasted around 2.4-2.1 billion years ago.
How the event ended was previously unknown.
Now, researchers have shown that the oxygen level decreased along with a massive loss of life.
It is thought that more than 80 percent of life died – a dying event that surpasses all mass extinction.
Geologists Malcolm Hodgskiss of Stanford University in California, Peter Crockford of the Weizmann Institute of Science, Israel and colleagues studied rocks collected from the Belcher Islands, on the southeastern side of the Hudson Bay in Canada.
In particular, the team focused on a sulfate mineral called barite, which can store a record of the oxygen levels in the atmosphere and the level of productivity of life at the time it was formed.
The researchers studied oxygen, sulfur, and barium isotopes in the rock samples and discovered that the Earth's biosphere – the region's # 39; s occupied by life – underwent enormous changes that started about 2.4 billion years ago .
This was the time of the so-called Great Oxidation Event, when a large amount of free oxygen was first released into the atmosphere and the old microbial life multiplied – but it was unclear how this event ended.
The researchers discovered that the number of living organisms had fallen enormously about 2.05 billion years ago – a connection with the fall in oxygen levels.
More than 80 percent of life may have died today, the team believes – making this extinction greater than both the event that killed the dinosaurs about 66 million years ago and the so-called & # 39; Great Dying & # 39; 252 million years ago.
& # 39; The fact that this geochemical signature was preserved was very surprising & # 39 ;, said Mr. Hodgskiss.
& # 39; What was particularly special about these barites is that they clearly had a complex history. & # 39;
The findings offer a rare window in life about two billion years ago, during a period before the complex life of which the fossil record is extremely scarce.
& # 39; This shows that even if the Earth's biology consists entirely of microbes, you can still have a huge event that would otherwise not be recorded in the fossil record, & # 39; said Mr. Hodgskiss.
The discovery of a link between the proliferation of life and the atmospheric oxygen levels of the ancient earth supports a hypothesis regarding the Great Oxygenation event that the & # 39; oxygen overrun & # 39; is called.
This suggests that the weathering of rocks and energy production by old microorganisms releases an enormous amount of oxygen into the Earth's atmosphere.
However, it is believed that these levels decreased later because the oxygen-emitting organism in the oceans used up their nutrients and decreased in number.
This situation is different from the stable atmosphere found on Earth today, where the amount of oxygen that is created and that is essentially used up, is in balance.
The researchers studied oxygen, sulfur and barium isotopes in the rock samples, photographed, and discovered that the Earth's biosphere – the region's # 39; s occupied by life – underwent enormous changes that amounted to around 2.4 billion started years ago
The researchers' isotope data helps to refine estimates of the extent of oxygen exceedance by revealing its impact on life.
& # 39; Some of these oxygen estimates probably require too many microorganisms that live in the ocean in the past, & # 39; said Dr. Crockford.
& # 39; So we can now begin to delve into what the composition of the atmosphere could have been through this biological perspective. & # 39;
& # 39; The size of the biosphere through geological time has always been one of our biggest questions in studying the history of the earth & # 39 ;, said Stanford university geologist Erik Sperling, who was not involved in current research.
& # 39; This new proxy shows how inthe biosphere and levels of oxygen and carbon dioxide in the atmosphere are connected. & # 39;
The full findings of the study were published in the journal Proceedings of the National Academy of Sciences.
Geologists Malcolm Hodgskiss of Stanford University in California, Peter Crockford of the Weizmann Institute of Science, Israel and colleagues studied rocks collected from the Belcher Islands, on the southeastern side of the Hudson Bay in Canada
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