The Great Earth Oxidation Event lasted 200 million years; to understand

Although we’ve become accustomed to oxygen as a natural part of our lives (after all, we breathe this diatonic gas about 20,000 times a day), this precious element wasn’t always part of Earth’s atmosphere. In fact, its formation took place approximately 2.5 billion years ago. This is when a substance called free oxygen (O2) begins to accumulate significantly.

This phenomenon In this event, which scientists call the Great Oxidation Event (by its English abbreviation), nothing emerges as a result.According to the latest research led by biologist Chadlin Ostrander, a professor at the University of Utah in the US.

The process that led to the emergence of complex life on Earth may have taken up to 200 million years, the authors say. However, the biologist thinks that the appearance of O2 occurs irregularly and intermittently. as the atmosphere and ocean become oxygenated and deoxygenated together, the study says.

What was the geochemical evidence for an oxygen-free atmosphere?

Because science is unaware of what was happening in the oceans, where the first terrestrial life forms likely emerged, the team focused on studying marine shales called the Transvaal Supergroup, according to Ostrander. A series of ancient rocks in southern Africa formed between 2.5 billion and 2.1 billion years ago.

By analyzing constant ratios of thallium metal isotopes and other redox-sensitive elements (loss and gain of electrons), they identified significant oscillations in sea O2 levels.

If an anoxic atmosphere (without oxygen) is proven, One of the “lethal” pieces of evidence is the presence of signature sulfur isotopes in ancient sedimentary rocks.. In the absence of oxygen, sulfur combines with iron to form deposits of pyrite (FeS2), known as “fool’s gold.”

What is the conclusion of the study of the Great Oxidation Event?

O2 produced by cyanobacteria in the second half of Earth’s existence Researchers say that it reached the oceans before the GOE, but quickly disappeared by reacting with the released minerals and volcanic gases. But, Traces of rare sulfur isotopes fade and reappear, indicating multiple rises and falls in the gas.

Meanwhile, the team examining thallium on the seabed detected an increase in the ratio of the lightest isotope (203TI) to the heaviest isotope (205Tl). Its formation is consistent with the presence of manganese oxide, indicating the accumulation of O2 in water.

These enrichments were also found in samples without traces of the rare sulfur isotope, which is a sign of the presence of oxygen. In other words, when the atmosphere is oxygenated, the ocean is also oxygenated. And vice versa.

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