Not my area of expertise either but off the top of my head Argon, let alone Argon-40, is a rare gas while Potassium (K, not Kr as I wrote in my previous post) is pretty common in rocks. At some point the amount of Potassium decayed into Argon-40 will be orders of magnitude larger than the atmospheric levels of Argon-40, so for any rock that has high Argon-40 concentrations most of that would be radiogenic, enough that the original concentration of Argon-40 from the atmosphere wouldn't cause more than a small error.
Not my area of expertise, but a question immediately comes to mind. How would you distinguish radiogenic Argon-40 from atmospheric Argon-40? I'm talking physically or chemically, not from a post de facto assumption that because of some other method also used the sample must be old enough for the Argon-40 to have been produced in place, therefore it must be radiogenic in origin.
Fossil Dating Fail
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Posted 28 November 2012 - 06:23 PM
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