Age Correlations and an Old Earth: Part II.

From:
Principles of Isotope Geology
Gunter Faure
1977, John Wiley & Sons, Inc.I suspect there is a more recent edition out, but the above is the one I have.From Chapter 20 - Carbon, p. 379:

quote:

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Carbon (Z=6) has two stable isotopes: ¹²C=98.89 percent and ¹³C=1.11 percent. In addition, radioactive ¹⁴C occurs in nature due to its formation in the upper atmosphere by an (n,p) reaction on stable ¹⁴N.

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and

quote:

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The isotopes of carbon are fractionated by a variety of natural processes, including photosynthesis and isotope exchange reactions among carbon compounds. Photosynthesis leads to enrichment of ¹²C in biologically synthesized organic compounds. On the other hand, isotope exchange reactions between CO₂ gas and aqueous carbonate species tent to enrich carbonates in¹³C. As a result, the isotopic abundance of ¹³C in terrestrial carbon varies by about 10 percent.

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Of course, the book goes on into a greater detail discussion of this.I didn't dig around, to find out what influence on Carbon dating these fractionations have. I am confident it is not a fatal influence.Moose

The chemical processes lightly touched on in message 121 DO NOT change one isotope of Carbon into another.Quoting myself from 121:

quote:

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On the other hand, isotope exchange reactions between CO₂ gas and aqueous carbonate species tend to enrich carbonates in¹³C.

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What this is saying, as I understand it, is that when C0₃ disolved in water comes in contact with atmospheric CO₂, there is an exchange of C between the two phases. In this exchange, the ¹²C tends to slightly preferentially go into the atmospheric CO₂, and the ¹³C tends to slightly preferentially go into the disolved carbonate (CO₃). This would cause in any precipitated CO₃ (I presume as CaCO₃) to be higher in ¹³C.I don't know how this process might effect ¹⁴C in the sediments. It would seem that it would also be slightly enriched. BUT the Carbon dating is NOT being done on the carbonate (per someone upthread), but rather on organic carbon from plant debris.Mooseps: Doing all these sub and superscripts sure is a pain.