RE: [asa] Kirk on C14 contamination

So after reading Baumgardner's response in
http://www.answersingenesis.org/articles/2007/11/30/feedback-rate-contaminat
ion, I have listed several paragraphs below which are snips from the
original that I see as the main ones having any serious merit toward
affecting Kirk's conclusions. Anyone care to respond to them?

"He invokes the fact that over the years many AMS labs have established that
their procedures routinely introduce tiny amounts of modern carbon (with
today’s level of 14C), typically on the order of 1 µg, into the samples they
process. This level of contamination becomes serious for tiny sample sizes,
say, 1 mg or less, especially if the sample is old. On the other hand, 1 µg
of contamination has negligible consequences when the sample size is on the
order of 100 mg, as was the case for the samples we tested and reported.
Bertsche fails to point out the very basic reality that AMS labs normally
require a large enough sample such that this issue does not affect the
precision of their measurement. For most of the 14C values reported in the
peer-reviewed literature which I list in my chapter in the RATE book
[Vardiman et al., 2005] the investigators had plenty of material available,
and so, small sample size was just not an issue."

"Moreover, Bertsche is simply incorrect when he then claims “the
graphitization process typically add[s] from 0.1 to 0.7 pMC (highly
dependent on sample size and procedure).” This is absurd. He cannot support
such a claim from any peer-reviewed source. "

"In regard to 14C production due to the presence of uranium in crustal
environments, I treat that topic in detail in section 7 of my chapter and
show the maximum plausible 14C production rate, given measured neutron
fluxes in deep mines and measured reaction cross sections, is more than four
orders of magnitude too small to account even for the small measured 14C
levels in diamonds. This same analysis also applies to coal. "

"I emphasized the careful procedures applied in the collection and
preservation of these samples. They were sealed under argon to preclude
contamination from just moments after they were collected. For most of their
lives these samples were sealed in argon in multi-laminate foil bags and
refrigerated at 3 °C."

"Instrument background involves a “14C signal registering in the detector
circuitry when 14C-ion [is] not present.” This item is routinely and
reliably tested by running the system with no sample in the aluminum sample
holder. This test is the basis for the value of the ultimate AMS detection
limit, about 0.0005 pMC, corresponding to about 100,000 14C years. "

Jon Tandy

-----Original Message-----
From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On
Behalf Of Michael Roberts
Sent: Friday, November 30, 2007 2:30 PM
To: asa@calvin.edu; Kirk Bertsche
Subject: [asa] Kirk on C14 contamination

Some may have seen the discussion led by Kirk on C14 on Theology Weband how
Baumgardner responded (or rather didn't). The AIG website now deals with it
http://www.answersingenesis.org/articles/2007/11/30/feedback-rate-contaminat
ion in a way which is very disparaging to Kirk. The comments are
unjustified.

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Received on Fri Nov 30 16:48:39 2007