Title: Two-billion-year transitional oxygenation of the Earth’s surface
Author: Haiyang Wang, Chao Li*, Yongbo Peng*, Junpeng Zhang, Meng Cheng, Xiaobin Cao, Wenkun Qie, Zihu Zhang, Matthew S. Dodd, Mingcai Hou, Malcolm Wallace, Ashleigh v.S. Hood, Timothy W. Lyons, Huiming Bao
Journal: Nature
Date of Publication: SEP 18 2025
Volume: 645
Issue: 8081
DOI: 10.1038/s41586-025-09471-4
Abstract：Earth’s surface underwent stepwise oxygenation before persistently reaching modern levels late in its history, but the details of this transition remain unclear. Here we present a high-resolution 2.5-Gyr record of mass-independent oxygen isotopes in sedimentary sulfate (Δ′17Osulfate), a proxy linked to the atmospheric partial pressure of O2 (pO2) . This record, together with existing sedimentary Δ33S data, demonstrates a 2-Gyr transition characterized by generally low, fuctuating pO2 between an O2-free state before 2.4 billion years ago (Ga) and a modern pO2 state after 0.41 Ga, with relatively elevated levels after 1.0 Ga. Our data also show coupled declines in Δ′17Osulfateand sulfate-δ34S during major negative carbonate-δ13C excursions in the Neoproterozoic. Quantitative biogeochemical modelling indicates that these isotopic couplings refect the increasing pO2, which may have driven episodic ocean oxygenation through an increased atmospheric O2 infux. This process intensifed the oxidation of marine organics and reduced-sulfur species, while triggering temporary pO2 drawdowns as negative feedback. These fndings support a dynamic, lengthy co-oxygenation history for the atmosphere and oceans—marked by long-term positive coupling and short-term negative feedbacks—ofering a coherent explanation for the anomalous Neoproterozoic carbon cycles and the protracted, episodic rise of complex life.
Key Words: ATMOSPHERIC OXYGEN; ISOTOPE EVIDENCE; OXIDATION; SULFATE; O-2; RECORD; RISE; CONSTRAINTS; CARBONATE; EVOLUTION
