Mesozoic atmospheric CO2 concentrations reconstructed from dinosaur tooth enamel

• 成果类型: Article
• 署名作者: Feng, Dingsu; Tuetken, Thomas; Griebeler, Eva Maria; Herwartz, Daniel; Pack, Andreas
• 署名单位: University of Gottingen; Ruhr University Bochum; Johannes Gutenberg University of Mainz; Johannes Gutenberg University of Mainz
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12189
• DOI: 10.1073/pnas.2504324122
• 发表日期: 2025-08-04
• 关键词: oxygen-isotope fractionation; biogenic apatites; cenozoic co2; carbonate; phosphate; climate; volcanism; record; rocks; water

摘要

Air-breathing vertebrates incorporate a fraction of isotopically anomalous air O2 in their body water. The 17O isotope anomaly of air O2 (expressed as 0'17Oair) is related to atmospheric CO2 concentrations (pCO2) and gross primary production (GPP). Tooth enamel records the 0'17O of body water and can thus preserve such paleo-pCO2 or paleo-GPP information over geological time periods. Here, we demonstrate the potential of respective reconstructions of atmosphericpCO2 or GPP from the triple oxygen isotope composition of fossil dinosaur tooth enamel. The data from unaltered enamel samples, along with an assumed modern GPPt/GPP0 ratio of 1 for the Mesozoic, suggest a mean Late JurassicpCO2 = 1,200 +/- 150 ppmv and Late Cretaceous pCO2 = 750 +/- 200 ppmv. These estimates are in good agreement with otherpCO2 proxy data for the same time intervals. When utilizing apCO2 inferred from other proxies, tooth enamel 0'17OPO4 may also serve as a proxy for GPP. Using published pCO2 data, we reconstructed GPPt/GPP0 ratios with 1.20 +/- 0.17 for the Late Jurassic and 2.24 +/- 0.96 for the Late Cretaceous, which would imply a 20 to 120% higher GPP in the Mesozoic than today. Overall, triple oxygen isotope analysis of fossil teeth of terrestrial amniotes can provide insights into past atmospheric greenhouse gas content and global primary productivity. Significance Paleoclimate is closely linked to atmospheric pCO2. Quantifying ancient CO2 levels, however, is challenging. Air-breathing vertebrates respire air O2 and incorporate its isotope signature via body water into their hard tissues. Fossil tooth enamel can thus serve as a robust time capsule for ancient air O2 isotope compositions. Air O2 has an 17O-anomaly that increases with increasing atmospheric pCO2 and decreases with increasing gross primary productivity (GPP). Therefore, paleo-pCO2 or paleo-GPP, respectively, can be determined by oxygen isotope measurements of fossil tooth enamel. Here, we reconstruct Mesozoic paleo-pCO2 levels from the triple oxygen isotope composition of dinosaur teeth and obtain paleo-pCO2 levels 2.5 to 4 times higher than preindustrial values. In addition, changes in the 17O-anomaly could also point to substantial fluctuations in GPP of the biosphere.