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I've been doing some reading about radiometric dating and I've come across an interesting find. If anybody has any additional information on this, that would be great.

First my question: In regards to Carbon-14, is leaching of radiometric material a concern and does/will it have an effect on the results of object?

Hypothetical

One animal dies near a stream. Half of it is safe on dry ground with little to no moisture, the second half falls into the stream. Time goes by.

We find the animal remains and test them both, what are the results?

Question details

I imagine that time is a factor, so if you want to elaborate on your answer by giving me the different effects during different time periods, that is perfectly acceptable.

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Not sure what exactly you are getting at here.. carbon dating works by comparing the ratio of C12 to C14, and the isotopes will behave practically identically with respect to physical/chemical processes, so this ratio is not going to be affected by moisture. –  user2963 Sep 1 '11 at 13:30
    
I'm not really targeting C14 dating methods. I'm just interested in knowing if C14 can be leached in or out of an object. in this case, bones. –  Jonathon Byrd Sep 1 '11 at 16:41
    
@zephyr, please post this as an answer with supporting evidence that these two objects, one in a stream and one in a non moisture environment, will show the same results when testing the c12-c14 ratios. –  Jonathon Byrd Sep 1 '11 at 16:46
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@Jonathon I think the burden is on you to propose a mechanism by which leaching would deferentially affect the two isotopes. If carbon is removed by leaching, both isotopes should be removed at essentially the same rate. Any error due to fractionation in this case would be much smaller than measurement error. –  David Sep 2 '11 at 2:09
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@Chris: perhaps, but as stated it's a perfectly acceptable question. Good science doesn't have a problem with taking a critical view of your own theories. –  David Z Sep 2 '11 at 22:41
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1 Answer 1

In general the dating works IF any process that happens after death effects carbon12 and carbon 14 equally. We are interested in the ratio of c12/c14 in the sample

Essentially they have the same chemistry so you would expect all chemical and biological processes to treat them the same. There is a slight difference in mass (14/12) which means that as gases they would move slightly differently (this is the effect used to separate isotopes to make nuclear fuel for example). But in general any process that leached out carbon would leach out carbon12 and c14 equally.

A more serious effect for archeaology is that we assume the animal took in standard amounts of c12 and c14 - which since c14 is made constantly in the atmosphere is true if it's getting all it's carbon from the atmosphere (ie plants). But if a lot of the carbon comes from very old stuff it's possible that a lot of the c14 will have decayed and the carbon is much more carbon12 rich and so appears older.

This is a problem for sites where people ate a lot of deep sea fish - the fish fed from the bottom of the sea which contains creatures that ate very old mud and so are C14 poor. This ends up with bodies that are C14 poor and so appear much older than they are.

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Have there been any studies that compare carnivores to plant eaters? I'd be interested in seeing what the comparisons look like. –  Jonathon Byrd Sep 2 '11 at 3:53
    
@jonathon - it doesn't matter, carnivores eat things that recently ate plants. Compared to the 6000yr half life of C14 eating a 2year old deer rather than fresh plants is pretty irrelevant –  Martin Beckett Sep 2 '11 at 4:03
    
@Martin unless the deer and plants were born after ~ 1960, after nuclear weapons testing added a strong label to the atmosphere skeptics.stackexchange.com/questions/5993/… –  David Sep 4 '11 at 5:29
    
@David - yes the calibration gets trickier but you probably wouldn't C14 date an artifact from the 60s –  Martin Beckett Sep 4 '11 at 15:23
    
@Martin I was mostly pointing out that the bomb pulse permits dating with an accuracy on the order of years, which is relevant in studying the global carbon cycle if not artifacts. So it isn't necessarily relevant to this question, and it doesnt depend on radioactive decay, but I wanted to point it out. –  David Sep 5 '11 at 0:55
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