EARTH × ATMOSPHERE

The Lomagundi-Jatuli Excursion

~2.44 to 2.02 billion years ago

Proterozoic · Paleoproterozoic · Siderian

The Lomagundi-Jatuli excursion, between 2.44 and 2.02 billion years ago, is the largest shift in carbon isotopes, the light and heavy forms of carbon, in the whole geological record.

The Lomagundi-Jatuli excursion is an interval of four hundred million years during which marine limestone is enriched in heavy carbon. The excursion is the largest shift in carbon isotopes measured in rocks of any age. It began about when oxygen first entered the air. Photosynthesis produces oxygen and organic carbon, the carbon of living matter, in equal measure, and decay consumes them again. Every carbon atom that is buried instead of decaying therefore leaves a molecule of oxygen behind. Burial removes the light carbon preferentially, so the remaining seawater is enriched in the heavy isotope, and limestone formed in that seawater has the same enrichment. The ocean of this interval appears to have buried organic carbon on a scale never repeated.

Why it matters

If the excursion was worldwide, oxygen overshot its equilibrium level, the level at which its sources and its losses balance, during the first oxygenation. It reached concentrations that the planet would not attain again for a billion and a half years.

Dating & uncertaintyDisputed

The Lomagundi-Jatuli excursion is the largest known carbon isotope excursion, and among the most contested. Edmonson and colleagues (2026) used Bayesian statistics to reconstruct the global record, and date the excursion from 2,445 to 2,018 million years ago, with a maximum 2,130 million years ago. Other work finds that the size of the shift depends on water depth, which would make the excursion a set of local excursions rather than a single event. The level that oxygen actually reached depends on which reading is right.

Earth history as one day

11:04:2912 h 56 min before midnight

if Earth’s 4.54 billion years were compressed into a single day