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Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India

September 2014

Quentin Crowley, Ussher Assistant Professor in Isotope Analysis and the Environment in the School of Natural Sciences at Trinity, is senior author of a paper published in the world's top-ranked Geology journal, Geology.

Working with Ph.D. student Kyle Heron, Professors Joydip Mukhopadhyay and Gautam Ghosh and other colleagues from Presidency University in Kolkata, India, their research found evidence for chemical weathering of rocks leading to soil formation that occurred in the presence of oxygen at least 3.02 billion years ago. Such substantial levels of oxygen could only have been produced by organisms capable of oxygenic photosynthesis. The early Earth was very different to what we see today. Our planet's early atmosphere was rich in methane and carbon dioxide and had only very low levels of oxygen. The widely accepted model for evolution of the atmosphere states that oxygen levels did not appreciably rise until about 2.4 billion years ago. This 'Great Oxidation Event' event enriched the atmosphere and oceans with oxygen, and heralded one of the biggest shifts in evolutionary history. Micro-organisms were certainly present before 3.0 billion years ago but they were not likely capable of producing oxygen by photosynthesis. Up until very recently however, it has been unclear if any oxygenation events occurred prior to the Great Oxidation Event and the argument for an evolutionary capability of photosynthesis has largely been based on the first signs of an oxygen build-up in the atmosphere and oceans.

Professor Crowley concluded: "Our research gives further credence to the notion of early and short-lived atmospheric oxygenation. This particular example is the oldest known example of oxidative weathering from a terrestrial environment, occurring about 600 million years before the Great Oxidation Event that laid the foundations for the evolution of complex life."

Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. 2014. Geology. Joydip Mukhopadhyay, Quentin G. Crowley*, Sampa Ghosh, Gautam Ghosh, Kalyan Chakrabarti, Brundaban Misra, Kyle Heron, Sankar Bose. DOI

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OXYGENATION SYMOPSIUM: Quentin Crowley recently hosted a symposium on this theme, which was funded by the Irish Research Council, with a contribution from the School's research fund.