Earth’s Oxygen Increased in Gradual Steps Rather Than Big Bursts

An oxygenated Earth is vital for the evolution of complex life.
Credit: NASA
A carbon cycle anomaly discovered in carbonate rocks of the Neoproterozoic Hüttenberg Formation of north-eastern Namibia follows a pattern similar to that found right after the Great Oxygenation Event, hinting at new evidence for how Earth’s atmosphere became fully oxygenated.

By Emily Moskal |

By using the Hüttenberg Formation, which formed between a billion and half a billion years ago, to study the time between Earth’s change from an anoxic environment (i.e. one lacking oxygen) to a more hospitable environment that heralded the animal kingdom, a team of researchers led by Dr. Huan Cui of the NASA Astrobiology Institute at the University of Wisconsin–Madison discovered a sustained, high level of carbon. This influx of carbon, coupled with changes in other elements, indicates how changing levels of oceanic oxygen may have lent a helping hand to early animal evolution.

The study, published in the journal Precambrian Research, paired new oxygen, sulfur, and strontium isotope data, with carbon isotope data published in 2009, obtained from drill core samples from the Hüttenberg Formation. Together, the data provides further evidence that Earth’s oxygen increased in a stepwise fashion, as opposed to being constrained to two major events capping the Proterozoic (a geological epoch that lasted between 2.5 billion and 541 million years ago). The resulting pattern of changing redox reactions (i.e. reactions involving oxygenation and reduction via the exchange of electrons) was named the Hüttenberg Anomaly, after the rock formation in which it was found. [Photos: Ancient Mars Lake Could Have Supported Life]

The University of Maryland’s Dr. Alan J. Kaufman, who is the second author of the study and the lead author of the 2009 carbon isotope study, says that the paired data „suggest that the rise of oxygen was oscillatory through this 50- to 75-million year interval associated with the Hüttenberg Anomaly and the Neoproterozoic Oxidation Event or NOE at the end of the Proterozoic.“

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