Lesson plan
Δ18O
In geochemistry, paleoclimatology and paleoceanography δ 18 O or delta-O-18 is a measure of the deviation in ratio of stable isotopes oxygen-18 ( 18 O) and oxygen-16 ( 16 O). It is commonly used as a measure of the temperature of precipitation, as a measure of groundwater/mineral interactions, and as an indicator of processes that show isotopic fractionation, like methanogenesis. In paleosciences, 18 O: 16 O data from corals, foraminifera and ice cores are used as a proxy for temperature. It is defined as the deviation in "per mil" (‰, parts per thousand) between a sample and a standard: : \delta \ce{^{18}O} = \left( \frac{\left( \frac\ce{^{18}O}\ce{^{16}O} \right)_\mathrm{sample}}{\left( \frac\ce{^{18}O}\ce{^{16}O} \right)_\mathrm{standard}} - 1 \right) \times 1000 ‰ where the standard has a known isotopic composition, such as Vienna Standard Mean Ocean Water (VSMOW). The fractionation can arise from kinetic, equilibrium, or mass-independent fractionation.
Article summary
In geochemistry, paleoclimatology and paleoceanography δ 18 O or delta-O-18 is a measure of the deviation in ratio of stable isotopes oxygen-18 ( 18 O) and oxygen-16 ( 16 O). It is commonly used as a measure of the temperature of precipitation, as a measure of groundwater/mineral interactions, and as an indicator of processes that show isotopic fractionation, like methanogenesis. In paleosciences, 18 O: 16 O data from corals, foraminifera and ice cores are used as a proxy for temperature. It is defined as the deviation in "per mil" (‰, parts per thousand) between a sample and a standard: : \delta \ce{^{18}O} = \left( \frac{\left( \frac\ce{^{18}O}\ce{^{16}O} \right)_\mathrm{sample}}{\left( \frac\ce{^{18}O}\ce{^{16}O} \right)_\mathrm{standard}} - 1 \right) \times 1000 ‰ where the standard has a known isotopic composition, such as Vienna Standard Mean Ocean Water (VSMOW). The fractionation can arise from kinetic, equilibrium, or mass-independent fractionation.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.