It is the rare examples from the rock record that provide glimpses of how rocks weathered, professor Crowley added."
London, Sep 5 - In what could help rewrite the evolutionary history books, geologists, including two from Presidency University in Kolkata, have found that oxygen-producing life forms were present on earth some three billion years ago - a full 60 million years earlier than previously thought.
Working with professors Joydip Mukhopadhyay and Gautam Ghosh and other colleagues from the Presidency University in Kolkata, India, geologists from Trinity College Dublin found evidence for chemical weathering of rocks leading to soil formation that occurred in the presence of O2.
Using the naturally occurring uranium-lead isotope decay system, which is used for age determinations on geological time-scales, the authors deduced that these events took place at least 3.02 billion years ago.
The ancient soil (or paleosol) came from the Singhbhum Craton of Odisha, and was named the 'Keonjhar Paleosol' after the nearest local town.
These life forms were responsible for adding oxygen (O2) to our atmosphere, which laid the foundations for more complex life to evolve and proliferate.
This paleosol from India is telling us that there was a short-lived pulse of atmospheric oxygenation and this occurred considerably earlier than previously envisaged, explained Quentin Crowley, an assistant professor in isotope analysis and the environment at Trinity.
The pattern of chemical weathering preserved in the paleosol is compatible with elevated atmospheric O2 levels at that time.
Such substantial levels of oxygen could only have been produced by organisms converting light energy and carbon dioxide to O2 and water.
This process, known as photosynthesis, is used by millions of different plant and bacteria species today.
It is the rare examples from the rock record that provide glimpses of how rocks weathered, professor Crowley added.
The research gives further credence to the notion of early and short-lived atmospheric oxygenation, researchers concluded.