The International Isotope Effect Research Center of the School of Earth Sciences and Engineering, Nanjing University—led by Professors Yongbo Peng, Huiming Bao, and Xiaobin Cao—in collaboration with Professor Chao Li's team from Chengdu University of Technology and several other research institutes, has published a major study in the top journal Nature. By establishing a high-resolution triple oxygen isotope record of sulfate over the past ~2 billion years and combining it with quantitative biogeochemical modeling, the study reveals the stepwise evolutionary history of Earth's transition from an anoxic to an oxygen-rich atmosphere, as well as the mechanisms that controlled it. The findings provide critical geochemical tracers and theoretical foundations for understanding the origin and evolution of life on Earth and the formation of planetary habitability. 

In this study, through systematic sampling, analyses, and data compilation, the team established a record of sulfate triple oxygen isotope evolution spanning nearly 3 billion years. The record shows that atmospheric oxygen underwent three major rises: in the Paleoproterozoic (2.4–2.1 billion years ago), in the Neoproterozoic (~1.0 billion years ago), and in the Paleozoic (~440 million years ago). This indicates a stepwise increase from an anoxic atmosphere to a near-modern oxygen-rich state by about 410 million years ago. Meanwhile, high-resolution Neoproterozoic co-variations among C–S–O isotopes reveal that rising atmospheric oxygen triggered periodic oxidation of dominantly anoxic oceans. By integrating a systematic geochemical model (NEOCARBSULF) with O?–CO? box models, the study found that these pulsed ocean oxidation events, driven by atmospheric oxygen, oxidized organic carbon and reduced sulfur in anoxic waters. This produced large amounts of sulfate and inorganic carbon depleted in ??S, ??O, and ??C, generating co-perturbations in C–S–O isotopes. At the same time, the process consumed large amounts of oxygen through negative feedbacks, suppressing or even reversing further rises in atmospheric oxygen on short timescales. Thus, this study quantitatively reconstructed the evolutionary history of atmospheric oxygen and revealed the coupled co-evolutionary dynamics of atmospheric and ocean redox states. This work, titled "Two-billion-year transitional oxygenation of the Earth's surface", was published in Nature on July 27, 2025 

Research paper: https://www.nature.com/articles/s41586-025-09471-4