Caltech researchers challenge theory of Earth's ancient oxygenation

New research suggests that a long-standing scientific theory regarding Earth’s atmospheric oxygenation may be based on a misinterpretation of ancient geological data. For decades, scientists believed that specific carbon-isotope signatures found in rocks dating back 2 billion years provided evidence of a global chemical transformation that allowed oxygen to accumulate in the atmosphere.

However, a study led by Caltech researchers indicates that the unusual isotopic signals found in the Zaonega Formation in Karelia, Russia, may actually be the result of localized phenomena rather than a planetwide event. By using in situ extraction to analyze gases trapped in microscopic rock pores, researchers identified significant amounts of methane and propane with light carbon isotope ratios.

This signature is likely caused by local thermal processes, such as magma intruding into sedimentary basins. Such intrusions heat surrounding sediments, triggering the thermal breakdown of organic matter and releasing gases. This finding challenges the assumption that these markers represent a worldwide decline in organic carbon, suggesting instead that the changes were confined to specific sedimentary basins.