The early Paleoproterozoic Great Oxidation Event (GOE) represents the first and most significant oxygenation in Earth history, profoundly changing Earth’s surface systems from anoxic to moderately oxic states, thus paving the way for the origin and evolution of early eukaryotes. However, atmospheric and shallow seawater oxygen levels following the GOE are heavily debated, with persistently high and significantly low oxygen levels being suggested. To address this issue, we conducted detailed sedimentological, mineralogical, and geochemical studies on the carbonate rocks from the ca. 2.0 Ga Daguandong and Huaiyincun formations in North China. The consistently low I/(Ca + Mg) ratios (<0.5 μmol/mol), the absence of negative Ce anomalies (1.23 ± 0.07), and the presence of abundant aragonite crystal fans associated with marine red beds are revealed in these formations, suggesting low oxygen levels in shallow seawater and a substantial decline in oxygen levels shortly after the Lomagundi-Jatuli Event (LJE, ca. 2.06 Ga), a final component of the GOE. The prolonged low levels of atmospheric and shallow marine oxygen since ca. 2.0 Ga may have delayed the evolution of eukaryotes.
Article link: https://doi.org/10.1130/B38354.1
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