An expansive global oxygenation of Earth's surface environments 1.4 billion years ago

The notion of biogeochemical stasis during the Mesoproterozoic era (1.6 to 1.0 billion years ago, Ga) has been increasingly challenged by evidence of transient episodes of increased oxygen (O₂) levels in localized basins. However, the extent of oxygenation during this period - whether local or global - remains a topic of debate. Here, we present evidence of elevated global seawater molybdenum (Mo) isotope values, surpassing the typical Mesoproterozoic baseline, based on manganese (Mn)- and iron (Fe)-rich chemical sedimentary rocks in the ~1.45 Ga Tieling Formation, North China. Mass balance modeling indicates that as much as 80% of the global seafloor was oxygenated. Combined with prior evidence for elevated O₂ levels, our findings suggest a more expanded and prolonged global oxygenation event centered around ~1.4 Ga than previously recognized.