Previous models of the early Earth posited that the level of oxygen in the atmosphere was extremely low for the first two billion years of the planet’s history, over 100,000 times lower than the present level. Despite ephemeral increases in oxygen levels 2.7 to 2.6 billion years ago, oxygen remained sparse until the Great Oxidation Event about 2.3 billion years ago, when levels of free oxygen in the atmosphere swelled due to the rise of multicellular cyanobacteria not long before, in geological terms, which boasted more efficient metabolisms than their unicellular precursors.
However, a new study indicates that this picture of Earth’s greatest climatic revolution might be more complicated. The new research, led by Sean Crowe of the University of British Columbia, has revealed that oxygen began to build up in Earth’s atmosphere approximately 3 billion years ago, 700 million years prior to the Great Oxidation Event.
Crowe and colleagues from the University of Copenhagen investigated two geological layers in South Africa, both approximately 3 billion years old. The Nsuze paleosol is the most ancient preserved soil on Earth, and is sandwiched between volcanic rocks and sedimentary rocks that were deposited in the sea and river channels. The other geological unit examined was the Ijzermyn iron formation, The Space Reporter informs.
