About 2.5 billion years ago, free oxygen began to accumulate in Earth’s atmosphere. Researchers analyzed marine shales from South Africa’s Transvaal Supergroup, using thallium (Tl) isotope ratios to track ocean oxygen levels.
The study shows O2 levels fluctuated in the atmosphere and oceans, with evidence suggesting multiple rises and falls in O2. This dynamic process was crucial for Earth’s eventual oxygenation.
Breathing in oxygen today is something we take for granted, but the process of oxygen building up on Earth was anything but simple. A recent study has uncovered that it took almost 200 million years for our planet to accumulate significant amounts of oxygen during a period known as the Great Oxidation Event (GOE).
Around 2.5 billion years ago, the Earth’s atmosphere started to see the presence of free oxygen. To understand this ancient transformation, scientists studied marine shales found in the Transvaal Supergroup in South Africa. They focused on the ratios of thallium (Tl) isotopes in these rocks, which provided clues about the levels of oxygen in the oceans at that time.
The findings reveal that the levels of oxygen in both the atmosphere and the oceans were not steady but fluctuated significantly. There were periods when oxygen levels rose, followed by times when they fell. This back-and-forth process was critical in eventually leading to the stable oxygen-rich atmosphere we depend on today.
The study highlights how the accumulation of oxygen was a dynamic and complex journey. It wasn’t a straightforward increase but rather a series of steps forward and backward over millions of years.
This intricate process was essential in setting the stage for the development of life as we know it. Understanding these early fluctuations in oxygen levels gives us valuable insights into the history of our planet and the conditions that made life possible.
