Summary
The isotopic composition of O in seawater is a fundamental property of Earth's oceans, key to paleoclimate reconstructions and to our understanding of the origin of water on Earth, the water-rock reactions that govern seawater chemistry, and the conditions under which life emerged. Despite more than five decades of research, the geologic history of seawater 18O/16O remains a topic of intense debate. Without exception, well-preserved 18O/16O records from marine precipitates reflect both the minerals' formation temperature, and the isotopic composition of seawater. This duality has prevented unique interpretation of a long-term secular trend, in which 18O/16O in sedimentary rocks (e.g., carbonates, cherts) has increased by ~15 ‰ since the Archean. Here I outline an inter-disciplinary research program to address this fundamental problem, which integrates new geochemical observations, laboratory experiments, and numerical models.
We will generate geologic records of 18O/16O in two previously untapped repositories: iron oxides and iron-bearing authigenic clays. Several characteristics of both, and preliminary results, suggest that these repositories hold the potential to settle the long-standing debate about seawater 18O/16O. We will determine the temperature dependence of mineral-water O isotope fractionation in laboratory experiments and observations of natural systems. We will experimentally test the resistance of these minerals to O isotope exchange under geologically-relevant conditions, with the aim of evaluating the potential for late-stage isotopic resetting. Finally, we will develop models of the marine O isotope cycle, which account for the processes that govern seawater 18O/16O over long timescales, and which will be used to provide a quantitative understanding of the new records. With these new insights, we will explore implications for the geologic history of seawater chemistry, atmospheric composition, climate and biology.
We will generate geologic records of 18O/16O in two previously untapped repositories: iron oxides and iron-bearing authigenic clays. Several characteristics of both, and preliminary results, suggest that these repositories hold the potential to settle the long-standing debate about seawater 18O/16O. We will determine the temperature dependence of mineral-water O isotope fractionation in laboratory experiments and observations of natural systems. We will experimentally test the resistance of these minerals to O isotope exchange under geologically-relevant conditions, with the aim of evaluating the potential for late-stage isotopic resetting. Finally, we will develop models of the marine O isotope cycle, which account for the processes that govern seawater 18O/16O over long timescales, and which will be used to provide a quantitative understanding of the new records. With these new insights, we will explore implications for the geologic history of seawater chemistry, atmospheric composition, climate and biology.
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| Web resources: | https://cordis.europa.eu/project/id/755053 |
| Start date: | 01-09-2018 |
| End date: | 31-08-2023 |
| Total budget - Public funding: | 1 490 596,00 Euro - 1 490 596,00 Euro |
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Original description
The isotopic composition of O in seawater is a fundamental property of Earth's oceans, key to paleoclimate reconstructions and to our understanding of the origin of water on Earth, the water-rock reactions that govern seawater chemistry, and the conditions under which life emerged. Despite more than five decades of research, the geologic history of seawater 18O/16O remains a topic of intense debate. Without exception, well-preserved 18O/16O records from marine precipitates reflect both the minerals' formation temperature, and the isotopic composition of seawater. This duality has prevented unique interpretation of a long-term secular trend, in which 18O/16O in sedimentary rocks (e.g., carbonates, cherts) has increased by ~15 ‰ since the Archean. Here I outline an inter-disciplinary research program to address this fundamental problem, which integrates new geochemical observations, laboratory experiments, and numerical models.We will generate geologic records of 18O/16O in two previously untapped repositories: iron oxides and iron-bearing authigenic clays. Several characteristics of both, and preliminary results, suggest that these repositories hold the potential to settle the long-standing debate about seawater 18O/16O. We will determine the temperature dependence of mineral-water O isotope fractionation in laboratory experiments and observations of natural systems. We will experimentally test the resistance of these minerals to O isotope exchange under geologically-relevant conditions, with the aim of evaluating the potential for late-stage isotopic resetting. Finally, we will develop models of the marine O isotope cycle, which account for the processes that govern seawater 18O/16O over long timescales, and which will be used to provide a quantitative understanding of the new records. With these new insights, we will explore implications for the geologic history of seawater chemistry, atmospheric composition, climate and biology.
Status
CLOSEDCall topic
ERC-2017-STGUpdate Date
27-04-2024
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