Repeated occurrences of marine anoxia under high atmospheric O2 and icehouse conditions

• 成果类型: Article
• 署名作者: Chen, Jitao; Li, Shihan; Zhang, Shuang; Isson, Terry; Dahl, Tais W.; Planavsky, Noah J.; Zhang, Feifei; Wang, Xiang-dong; Shen, Shu-zhong; Montanez, Isabel P.
• 署名单位: Chinese Academy of Sciences; Chinese Academy of Sciences; University of Chinese Academy of Sciences, CAS; Texas A&M University System; Texas A&M University College Station; University of Waikato; University of Copenhagen; Yale University; Nanjing University; Nanjing University; University of California System; University of California Davis; University of California System; University of California Davis
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-13559
• DOI: 10.1073/pnas.2420505122
• 发表日期: 2025-07-01
• 关键词: large igneous province; isotopic compositions; ocean anoxia; uranium; oxygen; EVOLUTION; climate; carbon; MODEL; plants

摘要

The Late Paleozoic Ice Age (similar to 340 to 260 Ma) occurred under peak atmospheric O-2 (1.2 to 1.7 PIAL, pre-industrial atmospheric levels) for Earth history and CO2 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 CO2-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 (delta U-238(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 delta U-238(carb) coincident with negative C isotopic excursions and rises in paleo-CO2, all superimposed on a longer-term rise in delta U-238(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 account for the long-term O-2 increase, seafloor oxygenation, and overall low CO2, episodic pulses of C emissions had the potential to drive recurring short-term periods of marine anoxia (with 4 to 12% of seafloor anoxia) despite up to 1.7 times higher atmospheric O-2 than present day.