Jean N. R. Clemente, Haifeng Fan, Chadlin M. Ostrander, Hongjie Zhang, Hanjie Wen, Erik A. Sperling, Sune G. Nielsen
{"title":"铊同位素表明全球深海在寒武纪第三次后生动物辐射期间没有接近现代氧合","authors":"Jean N. R. Clemente, Haifeng Fan, Chadlin M. Ostrander, Hongjie Zhang, Hanjie Wen, Erik A. Sperling, Sune G. Nielsen","doi":"10.1111/gbi.70028","DOIUrl":null,"url":null,"abstract":"<div>\n \n <p>The geologically rapid appearance of most extant animal groups in the Cambrian fossil record is often linked to enhanced ocean oxygenation. However, conflicting reconstructions of the Cambrian redox landscape make it difficult to determine the extent of ocean oxygenation during this significant biotic event, particularly regarding the redox state of the global deep ocean. In this study, we present authigenic thallium isotope compositions (ε<sup>205</sup>Tl<sub>auth</sub>) for two shale sequences from South China (Qingjiang and Weng'an) that span the Cambrian Stage 2–3 boundary to the appearance of the Qingjiang biota, approximately 521–518 million years ago (Ma), a timeframe that chronicles a particularly rapid interval of metazoan diversification and radiation in the broader Cambrian explosion. If this event occurred amid modern-like extents of global ocean oxygenation, we would expect a significant increase in the global extent of seafloor Mn-oxide burial to drive lower ε<sup>205</sup>Tl<sub>auth</sub> values near the modern open-ocean composition of −6‱. Instead, we observe broadly stable ε<sup>205</sup>Tl<sub>auth</sub> values of around −3 to −4‱ in both studied sections. The lack of any significant Tl isotope shifts in our dataset argues against a short-term global ocean oxygenation event and suggests the global deep ocean was not characterized by modern extents of oxygenation 521–518 Ma. We reinterpret contemporaneous near-modern Mo and U isotope compositions to signal a relatively minor increase in marine oxygenation, likely limited to the continental shelves. However, ε<sup>205</sup>Tl<sub>auth</sub> lower than the average isotopic composition of approximately −2‱ in Ediacaran shales suggests a shift to comparatively better-oxygenated conditions sometime between ~555 Ma and 521 Ma. If diversification at this time was linked to increased ocean oxygen levels, these changes were likely more dominant in the relatively shallow-water settings of continental shelves most densely populated by Cambrian animals and were incapable of dramatically altering seawater Tl isotope mass balance through seafloor Mn-oxide burial.</p>\n </div>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"23 4","pages":""},"PeriodicalIF":3.4000,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Thallium Isotopes Suggest the Global Deep Ocean Did Not Approach Modern Oxygenation During Cambrian Age 3 Metazoan Radiation\",\"authors\":\"Jean N. R. Clemente, Haifeng Fan, Chadlin M. Ostrander, Hongjie Zhang, Hanjie Wen, Erik A. Sperling, Sune G. Nielsen\",\"doi\":\"10.1111/gbi.70028\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div>\\n \\n <p>The geologically rapid appearance of most extant animal groups in the Cambrian fossil record is often linked to enhanced ocean oxygenation. However, conflicting reconstructions of the Cambrian redox landscape make it difficult to determine the extent of ocean oxygenation during this significant biotic event, particularly regarding the redox state of the global deep ocean. In this study, we present authigenic thallium isotope compositions (ε<sup>205</sup>Tl<sub>auth</sub>) for two shale sequences from South China (Qingjiang and Weng'an) that span the Cambrian Stage 2–3 boundary to the appearance of the Qingjiang biota, approximately 521–518 million years ago (Ma), a timeframe that chronicles a particularly rapid interval of metazoan diversification and radiation in the broader Cambrian explosion. If this event occurred amid modern-like extents of global ocean oxygenation, we would expect a significant increase in the global extent of seafloor Mn-oxide burial to drive lower ε<sup>205</sup>Tl<sub>auth</sub> values near the modern open-ocean composition of −6‱. Instead, we observe broadly stable ε<sup>205</sup>Tl<sub>auth</sub> values of around −3 to −4‱ in both studied sections. The lack of any significant Tl isotope shifts in our dataset argues against a short-term global ocean oxygenation event and suggests the global deep ocean was not characterized by modern extents of oxygenation 521–518 Ma. We reinterpret contemporaneous near-modern Mo and U isotope compositions to signal a relatively minor increase in marine oxygenation, likely limited to the continental shelves. However, ε<sup>205</sup>Tl<sub>auth</sub> lower than the average isotopic composition of approximately −2‱ in Ediacaran shales suggests a shift to comparatively better-oxygenated conditions sometime between ~555 Ma and 521 Ma. If diversification at this time was linked to increased ocean oxygen levels, these changes were likely more dominant in the relatively shallow-water settings of continental shelves most densely populated by Cambrian animals and were incapable of dramatically altering seawater Tl isotope mass balance through seafloor Mn-oxide burial.</p>\\n </div>\",\"PeriodicalId\":173,\"journal\":{\"name\":\"Geobiology\",\"volume\":\"23 4\",\"pages\":\"\"},\"PeriodicalIF\":3.4000,\"publicationDate\":\"2025-08-06\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Geobiology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1111/gbi.70028\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"BIOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geobiology","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/gbi.70028","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"BIOLOGY","Score":null,"Total":0}
Thallium Isotopes Suggest the Global Deep Ocean Did Not Approach Modern Oxygenation During Cambrian Age 3 Metazoan Radiation
The geologically rapid appearance of most extant animal groups in the Cambrian fossil record is often linked to enhanced ocean oxygenation. However, conflicting reconstructions of the Cambrian redox landscape make it difficult to determine the extent of ocean oxygenation during this significant biotic event, particularly regarding the redox state of the global deep ocean. In this study, we present authigenic thallium isotope compositions (ε205Tlauth) for two shale sequences from South China (Qingjiang and Weng'an) that span the Cambrian Stage 2–3 boundary to the appearance of the Qingjiang biota, approximately 521–518 million years ago (Ma), a timeframe that chronicles a particularly rapid interval of metazoan diversification and radiation in the broader Cambrian explosion. If this event occurred amid modern-like extents of global ocean oxygenation, we would expect a significant increase in the global extent of seafloor Mn-oxide burial to drive lower ε205Tlauth values near the modern open-ocean composition of −6‱. Instead, we observe broadly stable ε205Tlauth values of around −3 to −4‱ in both studied sections. The lack of any significant Tl isotope shifts in our dataset argues against a short-term global ocean oxygenation event and suggests the global deep ocean was not characterized by modern extents of oxygenation 521–518 Ma. We reinterpret contemporaneous near-modern Mo and U isotope compositions to signal a relatively minor increase in marine oxygenation, likely limited to the continental shelves. However, ε205Tlauth lower than the average isotopic composition of approximately −2‱ in Ediacaran shales suggests a shift to comparatively better-oxygenated conditions sometime between ~555 Ma and 521 Ma. If diversification at this time was linked to increased ocean oxygen levels, these changes were likely more dominant in the relatively shallow-water settings of continental shelves most densely populated by Cambrian animals and were incapable of dramatically altering seawater Tl isotope mass balance through seafloor Mn-oxide burial.
期刊介绍:
The field of geobiology explores the relationship between life and the Earth''s physical and chemical environment. Geobiology, launched in 2003, aims to provide a natural home for geobiological research, allowing the cross-fertilization of critical ideas, and promoting cooperation and advancement in this emerging field. We also aim to provide you with a forum for the rapid publication of your results in an international journal of high standing. We are particularly interested in papers crossing disciplines and containing both geological and biological elements, emphasizing the co-evolutionary interactions between life and its physical environment over geological time.
Geobiology invites submission of high-quality articles in the following areas:
Origins and evolution of life
Co-evolution of the atmosphere, hydrosphere and biosphere
The sedimentary rock record and geobiology of critical intervals
Paleobiology and evolutionary ecology
Biogeochemistry and global elemental cycles
Microbe-mineral interactions
Biomarkers
Molecular ecology and phylogenetics.