The Shuram excursion
The largest carbon anomaly in Earth's history
See it on the timeline →In depth
The carbonates show negative δ¹³C values down to about −12 per mil, far outside what the carbon cycle normally permits, and the signal is found on several continents. Proposals include oxidation of a vast reservoir of dissolved organic carbon in the ocean, diagenetic alteration after deposition, and changes in marine sulphate. That we do not know is itself informative: this is among the best-documented and least-understood events in Earth history, and it sits in the middle of the window in which animal life originates.
For children
In rocks from Oman, China and the United States we find the same strange chemical signal from exactly this time. The carbon in the ocean behaved unlike anything before or since. Nobody has managed to explain it properly yet.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org