Re: extinction

[Dann Pigdon <dannj@alphalink.com.au>]

"Jaime A. Headden" wrote:
> 
> Dewey McLean (dmclean@vt.edu) wrote:
> 
> <Impactors claim that the Chicxulub impact occurred 65 million years ago.
> The initial phase of Deccan Traps volcanism occurred somewhat _earlier_
> than K-T boundary time.>
> 
>   This argument of dating was one of the reasons why I commented upon
> accuracy of dating...

Indeed. How can we say with certainty that the Deccan Traps started
spewing forth around a million years before the Chicxulub impact (that's
one figure I've seen), when surely any radiometric dates of both will
have standard deviations in the order of at least a million years (I
would expect)? Do the dates for both events actually overlap with two
standard deviations (or possibly put them even further apart)? Or are
non-radiometric dating methods employed to compare the two events
(biostratigraphy, etc)?

I've seen one date for Chicxulub of 64.98 +/- 0.05 MYA. Is it possible
to have such a small standard deviation (just 50,000 years) on a date of
this age? I've seen Thermoluminescence dates that, with two std dev,
range from between yesterday and 120,000 years ago!

-- 
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Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
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