From: Dawsonzhu@aol.com
Date: Fri Oct 03 2003 - 20:04:39 EDT
Allen Roy wrote:
> Rb-Sr dates for the Cardenas basalts (McKee and Noble, 1976, p. 1189) run
> like this. 1.06 +/- 0.07 billion years. (or +/- 70 million years) or 6.6%
> error
> 0.98 +/- 0.06 b.y. (6.7 % error)
> 1.09 +/- 0.08 b.y. (7.3 % error)
> 1.09 +/- 0.10 b.y. (9.2 % error)
> 1.07 +/- 0.04 b.y. (3.7 % error)
> 1.10 +/- 0.05 b.y. (4.5 % error) This is typical of the other Rb-Sr dates
> at Grand Canyon. It is far better than the 50% error you suppose.
>
>
I suppose nothing here, it was simply a question. Nevertheless, as a
student, I worked with radioactive elements and I could find nothing
objectionable about the radioactive dating method (at least conceptually).
However, I would expect error bars that depend strongly on how well one
can actually isolate the radioactive elements, how carefully the samples
were extracted, how much sample was available, and how well the samples
obtained were protected from contamination and environmental factors.
If one can basically count on error bars of 10%,
then surely if they found more the 20% discrepancy, then they must have
provided some kind of explanation. Just saying "it can't be right because
it doesn't fit my particular model of the stratigraphy" is not good science
and not my impression about any geologist I have known. Did they only
use Rb/Sr? If not, what other methods did they use to confirm the dates
they claim?
If this is the only layer out of order with the radioactive dating, for
geology, I wouldn't expect that is a major problem, IF a host of other
methods were used to back up a different conclusion. Geology is like
detective work, and you have to weigh the evidence at some point.
If every single layer yields an irreconcilable value from the radioactive
dating, then I would first tend to inquire of the analysis of the
stratigrapher(s). Only if I could find __no__ reconciliation between
these models would I begin to question the radioactive dating method
itself.
By Grace alone we proceed,
Wayne
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