3 ms·

I wonder how carbon dating works in this case. My understanding is that the dating method depends on the organism interacting with the carbon in the atmosphere

by avian 8y ago

I wonder how carbon dating works in this case. My understanding is that the dating method depends on the organism interacting with the carbon in the atmosphere during its lifetime (where carbon-14 is produced by cosmic rays). The interaction stops after organism dies, after which the level of carbon-14 in its body starts to decay. But here the whole ecosystem was supposedly isolated from the atmosphere for at least 10k years. Wouldn't all organisms, both alive and dead, just have the same (decaying) level of carbon-14 after isolation happened? EDIT: expanded for clarity.

JackFr 8y ago
I think you have it backwards -- carbon works by some organic material not interacting with the atmosphere. Atmospheric CO2 has a relatively constant proportion of carbon-14. Once it stops interacting with the atmosphere it begins to decay and have a different proportion than atmospheric carbon.
- deleted 8y ago
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- thaumasiotes 8y ago
  I don't understand this response. The model of the GP comment appears to be that: - The atmosphere has a certain level of carbon-14, and living things stay at the atmospheric level by virtue of the various processes by which they interact with the atmosphere. - When they stop living, they also stop exchanging carbon with the atmosphere, and their carbon-14 levels change due to radioactive decay over time. - But here, an environment was sealed off from the atmosphere while some organisms remained alive inside it. If we perform radiocarbon dating on such an organism, will we get the date at which the organism died (and stopped exchanging carbon with anything) or the date at which the environment was sealed (and everything stopped exchanging carbon with the atmosphere)? Your comment isn't responsive to this question. To answer it, we'd need to know why the atmosphere itself has constant levels of carbon-14 instead of decaying like everything else, and whether the sealed environment would have behaved more like the atmosphere or like something else.
  - yesenadam 8y ago
    >To answer it, we'd need to know why ... This page is good: https://en.wikipedia.org/wiki/Radiocarbon_dating https://en.wikipedia.org/wiki/Radiocarbon_dating

by avian 8y ago

JackFr 8y ago

I think you have it backwards -- carbon works by some organic material not interacting with the atmosphere. Atmospheric CO2 has a relatively constant proportion of carbon-14. Once it stops interacting with the atmosphere it begins to decay and have a different proportion than atmospheric carbon.

deleted 8y ago
[deleted]
thaumasiotes 8y ago
I don't understand this response. The model of the GP comment appears to be that: - The atmosphere has a certain level of carbon-14, and living things stay at the atmospheric level by virtue of the various processes by which they interact with the atmosphere. - When they stop living, they also stop exchanging carbon with the atmosphere, and their carbon-14 levels change due to radioactive decay over time. - But here, an environment was sealed off from the atmosphere while some organisms remained alive inside it. If we perform radiocarbon dating on such an organism, will we get the date at which the organism died (and stopped exchanging carbon with anything) or the date at which the environment was sealed (and everything stopped exchanging carbon with the atmosphere)? Your comment isn't responsive to this question. To answer it, we'd need to know why the atmosphere itself has constant levels of carbon-14 instead of decaying like everything else, and whether the sealed environment would have behaved more like the atmosphere or like something else.
- yesenadam 8y ago
  >To answer it, we'd need to know why ... This page is good: https://en.wikipedia.org/wiki/Radiocarbon_dating https://en.wikipedia.org/wiki/Radiocarbon_dating