Repeated occurrences of marine anoxia under high atmospheric O 2 and icehouse conditions

作者：Jitao Chen, Shihan Li, Shuang Zhang, Terry T. Isson, Tais W. Dahl, Noah J. Planavsky, Feifei Zhang, Xiangdong Wang, Shu‐zhong Shen, Isabel P. Montañez · 发表于：Proceedings of the National Academy of Sciences · 年份：2025 · DOI：10.1073/pnas.2420505122 · 被引用次数：7 · 研究领域：Ocean Acidification Effects and Responses、Paleontology and Stratigraphy of Fossils、Marine Biology and Ecology Research

The Late Paleozoic Ice Age (~340 to 260 Ma) occurred under peak atmospheric O 2 (1.2 to 1.7 PIAL, pre-industrial atmospheric levels) for Earth history and CO 2 concentrations comparable to those of the preindustrial to that anticipated for our near future. The evolution of the marine redox landscape under these conditions remains largely unexplored, reflecting that oceanic anoxia has long been considered characteristic of carbon cycle perturbation during greenhouse times. Despite elevated O 2 , a 10 5 -y period of CO 2 -forced oceanic anoxia was recently identified, but whether this short-term interval of widespread oceanic anoxia was anomalous during this paleo-ice age is unexplored. Here, we investigate these issues by building a high-resolution record of carbonate uranium isotopes (δ 238 U carb ) from an open-marine succession in South China that permits us to reconstruct the global marine redox evolution through the deep glacial interval (310 to 290 Ma) of near peak O 2 . Our data reveal repeated, short-term decreases in δ 238 U carb coincident with negative C isotopic excursions and rises in paleo-CO 2 , all superimposed on a longer-term rise in δ 238 U carb . A carbon–phosphorus–uranium biogeochemical model coupled with Bayesian inversion is employed to quantitatively explore the interplay between marine anoxia, carbon cycling, and climate evolution during this paleo-glacial period. Although our results indicate that protracted, enhanced organic carbon burial can accoun...