Mesozoic atmospheric CO2 concentrations from dinosaur tooth enamel
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Ben Creisler
Aug 4, 2025, 3:32:28 PM8/4/25
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Ben Creisler
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.
Abstract
Air-breathing vertebrates incorporate a fraction of isotopically anomalous air O2 in their body water. The 17O isotope anomaly of air O2 (expressed as Δ’17Oair) is related to atmospheric CO2 concentrations (pCO2) and gross primary production (GPP). Tooth enamel records the Δ’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 atmospheric pCO2 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 Jurassic pCO2 = 1,200 ± 150 ppmv and Late Cretaceous pCO2 = 750 ± 200 ppmv. These estimates are in good agreement with other pCO2 proxy data for the same time intervals. When utilizing a pCO2 inferred from other proxies, tooth enamel Δ’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.
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News:
A new paper:
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Dingsu Feng, Thomas Tütke, Eva Maria Griebeler, Daniel Herwartz, and Andreas Pack (2025)
Mesozoic atmospheric CO2 concentrations reconstructed from dinosaur tooth enamel
Proceedings of the National Academy of Sciences 122(33): e2504324122
doi: https://doi.org/10.1073/pnas.2504324122
https://www.pnas.org/doi/10.1073/pnas.2504324122
Significance
Dingsu Feng, Thomas Tütke, Eva Maria Griebeler, Daniel Herwartz, and Andreas Pack (2025)
Mesozoic atmospheric CO2 concentrations reconstructed from dinosaur tooth enamel
Proceedings of the National Academy of Sciences 122(33): e2504324122
doi: https://doi.org/10.1073/pnas.2504324122
https://www.pnas.org/doi/10.1073/pnas.2504324122
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.
Abstract
Air-breathing vertebrates incorporate a fraction of isotopically anomalous air O2 in their body water. The 17O isotope anomaly of air O2 (expressed as Δ’17Oair) is related to atmospheric CO2 concentrations (pCO2) and gross primary production (GPP). Tooth enamel records the Δ’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 atmospheric pCO2 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 Jurassic pCO2 = 1,200 ± 150 ppmv and Late Cretaceous pCO2 = 750 ± 200 ppmv. These estimates are in good agreement with other pCO2 proxy data for the same time intervals. When utilizing a pCO2 inferred from other proxies, tooth enamel Δ’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.
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News:
Prehistoric Air Has Been Reconstructed From Dinosaur Teeth in an Amazing First
Ben Creisler
Aug 9, 2025, 4:09:16 PM8/9/25
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A free pdf is now available:
Free pdf:
Dingsu Feng, Thomas Tütke, Eva Maria Griebeler, Daniel Herwartz, and Andreas Pack (2025)
Mesozoic atmospheric CO2 concentrations reconstructed from dinosaur tooth enamel
Proceedings of the National Academy of Sciences 122(33): e2504324122
doi: https://doi.org/10.1073/pnas.2504324122
https://www.pnas.org/doi/10.1073/pnas.2504324122
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