[ad_1]
A mass died about 2.05 billion years ago wiped out over 80% of lives and dwarf all mass extinctions – including the one that killed the dinosaurs.
Unlike the large animals that disappeared during these other events, however, the newly recognized disappearance involved tiny, simple microorganisms.
Researchers have found evidence of death in Canadian rocks, whose reports of isotopes preserve information about the environment at the time of their formation.
The disappearance that followed the increase in atmospheric and oceanic oxygen levels on Earth is accompanied by an increase in the abundance of life.
As the microorganisms of the day used their nutrients, their numbers were forced to go down.
Scroll for the video
A mass that perished about 2.05 billion years ago has wiped out over 80% of life – eclipsing all mass extinctions, including the one that killed the dinosaurs. Photographic rocks bearing baryta from the Belcher Islands in Canada, dating back about 2 billion years
Geologists Malcolm Hodgskiss of Stanford University in California, Peter Crockford of the Weizmann Institute of Science in Israel, and their colleagues studied rocks collected in the Belcher Islands, southeastern Bay of California. Hudson in Canada.
The team is particularly focused on a mineral sulphate called barite, which can record the oxygen levels present in the atmosphere and the extent of life productivity at the moment. of his training.
By studying the isotopes of oxygen, sulfur and barium in the rock samples, the researchers discovered that the Earth's biosphere – the regions of the planet occupied by life – had undergone vast changes there are about 2.4 billion years old.
It was the time of the so-called "Great Oxidation Event," in which a large amount of free oxygen was released into the atmosphere for the first time and where the old microbial life multiplied – but we did not know how this event ended.
The researchers found that about 2.05 billion years ago, the number of living organisms has dropped significantly, which could be related to the decrease in oxygen level.
The team think that over 80% of life may have already lost their lives, making this extinction greater than the event that killed the dinosaurs about 66 million years ago and the so-called "Great dies" 252 million years ago. .
"The fact that this geochemical signature was preserved was very surprising," said Hodgskiss.
"What was particularly unusual about these barites, is that they clearly had a complex history."
The discoveries offer a rare window on life about two billion years ago, at a time before the complex life from which the fossil record is extremely rare.
"This shows that even when the biology on Earth is entirely composed of microbes, you can still have what could be considered a huge lethal event that otherwise does not appear in the fossil record," Hodgskiss said.
The discovery of an association between the proliferation of life and the atmospheric oxygen levels of the ancient Earth supports a hypothesis concerning the event of the Great Oxygenation, dubbed the "Oxygen Overtaking." ".
This suggests that rock erosion and energy production by ancient microorganisms release a colossal amount of oxygen into the Earth 's atmosphere.
However, it is thought that these levels then decreased, as the oxygen-emitting organism in the oceans depleted its nutrient stores and decreased in number.
This situation is different from the stable atmosphere that reigns on Earth today, where the amount of oxygen created and consumed essentially balances.
By studying the isotopes of oxygen, sulfur and barium in rock samples, the researchers discovered that the Earth's biosphere – the regions of the planet occupied by life – had undergone extensive changes about 2 years ago. , 4 billion years old.
Isotope data from the researchers will help refine estimates of the size of oxygen exceedance by revealing its impact on life.
"Some of these estimates of oxygen probably require too many microorganisms living in the ocean in Earth 's past," said Dr. Crockford.
"So we can now begin to clarify what the composition of the atmosphere could have been from this biological perspective."
"The size of the biosphere through geological time has always been one of our biggest questions in the study of the Earth's history," said the geologist. Stanford University, Erik Sperling, who did not participate in this study.
& # 39; This new proxy shows how inThe biosphere is related to levels of oxygen and carbon dioxide in the atmosphere.
The complete results 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 in Israel, and their colleagues studied rocks collected in the Belcher Islands, southeastern Bay of California. Hudson in Canada.
[ad_2]
Source link