Washington, November 26: An international team says that banded ironstone core samples from the Pilbara rocks in Australia have aided in dating the first appearance of atmospheric oxygen at 2.48 billion years ago.
Prof Mark Barley, who led the team, says their findings, published in the ‘Nature' journal. rested on the reliability of the rock samples they used as evidence.
According to geologists, the Great Oxidation Event, when earth's atmospheric oxygen formed, happened at between 2.48 and 2.32 billion years ago.
“This was evidence for the most primitive form of aerobic respiring life, aerobic respiring bacteria which oxidise pyrite that released acid that dissolved rocks and soils on land, including chromium, that was then carried to the oceans by the flow of water.
“The aerobic respiring chemolitho-autorobic bacteria require coexistence with cyanobacteria producing oxygen to do this,” Prof Barley said.
Prof Barley says that geobiologists are working towards a better database, for more evidence of when the types of bacteria linked to the rise of oxygen were really functioning.
“We got a good group of samples from banded iron formations and analysed the chromium isotopes and other elements because that gives the strongest evidence of oxidation.
“If you have a good deep drill hole that's not close to a big iron ore deposit, you have got the appropriate chemistry record,” he said.
