biostudies-literatureBubphamanee KNASA | NASA Astrobiology Institute (NAI)NSF | NSF Graduate Research Fellowship Program (GRFP)NSF | NSF Graduate Research Fellowship ProgramNASA | NASA Astrobiology Institutee2501342122https://www.ebi.ac.uk/biostudies/studies/S-EPMC12415217biostudies-literatureUnknown122(35)The oxygenation history of Earth's surface environments has had a profound influence on the ecology and evolution of metazoan life. It was traditionally thought that the Neoproterozoic Oxygenation Event enabled the origin of animals in marine environments, followed by their persistence in aerobic marine habitats ever since. However, recent studies of redox proxies (e.g., Fe, Mo, Ce, I) have suggested that low dissolved oxygen levels persisted in the deep ocean until the Late Devonian, when the first heavily wooded ligniophyte forests raised atmospheric O₂ to modern levels. Here, we present a Paleozoic redox proxy record based on selenium enrichments and isotope ratios in fine-grained siliciclastic sediments. Our data reveal transient oxygenation of bottom waters around the EdiacProceedings of the National Academy of Sciences of the United States of AmericaMid-Devonian ocean oxygenation enabled the expansion of animals into deeper-water habitats.PMC12415217DGE-125608280NSSC19K0829MGG-2054892Algeo TJBrocks JJKinsley JStueken EETissot FLHIvany LCBuick RDahl TWBubphamanee KKipp MAMeixnerova JBartholomew AJfalseMid-Devonian ocean oxygenation enabled the expansion of animals into deeper-water habitats.The oxygenation history of Earth's surface environments has had a profound influence on the ecology and evolution of metazoan life. It was traditionally thought that the Neoproterozoic Oxygenation Event enabled the origin of animals in marine environments, followed by their persistence in aerobic marine habitats ever since. However, recent studies of redox proxies (e.g., Fe, Mo, Ce, I) have suggested that low dissolved oxygen levels persisted in the deep ocean until the Late Devonian, when the first heavily wooded ligniophyte forests raised atmospheric O₂ to modern levels. Here, we present a Paleozoic redox proxy record based on selenium enrichments and isotope ratios in fine-grained siliciclastic sediments. Our data reveal transient oxygenation of bottom waters around the Ediac2025-01-01T00:00:00Z2025 Sep2026-07-09T12:20:38.374Z2026-07-09T11:17:32.566ZS-EPMC124152174085413810.1073/pnas.2501342122