Timing and magnitude of carbon cycle changes during the rise of atmospheric oxygen

What is it about?

The rise of atmospheric oxygen during the Great Oxidation Event, which took place around 2.5 to 2.1 billion years ago, set the stage for the evolution of complex animal life. Co-eval marine carbonate rocks preserve a large and long-lived positive carbon isotope excursion, the Lomagundi-Jatuli excursion (LJE), that suggests this transformation was accompanied by a major perturbation to the carbon cycle. However, the timing, magnitude, and global extent of the LJE are uncertain due to the incomplete nature of the sedimentary rock record. Consequently, the excursion's cause and relationship to oxygenation are heavily debated. Here, we use Bayesian statistical modeling to reconstruct the LJE from a global data compilation. Our results suggest the excursion has a lower magnitude, earlier onset, and longer duration than previously thought, strengthening its temporal correlation with both the rise of atmospheric oxygen and planet-wide ‘snowball’ glaciation events.

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Photo by Sue Winston on Unsplash

Photo by Sue Winston on Unsplash

Why is it important?

Our results provide an improved understanding of carbon cycling across the interval when Earth's atmosphere first gained oxygen. Understanding these environmental transitions provides a critical perspective on the development of our planet and the rarity of life in the universe. Looking forward, our results will enable us to quantitatively test different hypotheses for what may have caused these Earth system changes.