New Info from Ancient Rocks Upends Popular Theory

Around two billion years ago, Earth's atmosphere filled with oxygen for the first time, a chemical shift that would eventually enable complex life. Geologists found unusual carbon signatures in ancient drill cores from Russia and Gabon, and many interpreted these as evidence of a global environmental upheaval. A Caltech-led study now challenges that interpretation. The researchers studied gases trapped inside two-billion-year-old rocks from Russia's Zaonega Formation and found that the anomalous carbon signature can be explained by local geology—specifically, magma intruding through seafloor sediments, heating organic-rich layers and triggering microbial activity. The effect was confined to a basin a few hundred square kilometers across, not a planet-wide event. Since the Russian site is considered a reference point for this supposed global event, the findings raise important questions about whether the change was truly worldwide. The team plans to study similar rock samples from Gabon to see if the same local processes can account for the signatures there.

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