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Re: first message



At 10:42 AM 8/8/00 -0400, TONY wrote:
Hi everybody,

I visited the some website last week
(www.discovery.com/area/specials/goni/dispatche/day4.html) hosted by an
expedition heading towards the Gobi desert seeking fossils.
In one article titled "How fossils go from bone to stone", the following
part struck me:
"A fine fossil is a freak of nature. The dead animal first must avoid
scavengers, floods and other scattering forces. Then it must be buried
in something that's neither too soggy nor completely dry, in a climate
that won't subject it to swelling/shrinking cycles that will splinter
it. AND IT HAS TO STAY THERE FOR A TIME PERIOD WE'LL JUST CALL "AGES",
SINCE FOSSILIZATION TIME CAN VARY WILDLY. (THE CITIZENS OF POMPEII WERE
ROCK-SOLID IN UNDER 2000 YEARS; YET SOME 65 MILLION-YEAR-OLD-DINOSAUR
BONES ARE STILL NOT COMPLETELY STONE.)"

Such a huge difference in timing to achieve the same phenomenon looks
impossible to me. Are we that sure these fossils are actually 65
million  years old ? How accurate is the dating process ?

They are securely dated. The error bars are on the order of +/- 0.5 million.

The statement is also correct. Indeed it is an understatement, some Late Cretaceous bones are still almost entirely original material.

Part of the difference is that the Pompei situation was very special. Hot volcanic ash with large amount of volatile gases has a different effect on organic material than burial in anoxic fine sand or mud. Indeed, the difference is immediately obvious when you note that the Pompei burials preserved soft tissue to some degree.

Is it absolute
or does it involve some stable environmental conditions (such as the
carbone rate in the atmosphere or the cycles of the sun...whatever could
generate a big mistake in any dating process if ignored)?

It is based on radioactive decay. The only significant source of error is in the measurement of the quantities of the various isotopes - and nowadays that is very accurate.


Has any
parameter been forgotten for simplification purposes ?
Mainly the difference in preservation conditions.

--------------
May the peace of God be with you.         sarima@ix.netcom.com