I have tried to find any sources of the calibrating curve but I always
ends up on a publication server that tells me I have to pay to read the
article.
As you seems to have found it, could you tell me where to find it or
show us the curve and dataset?
The closest thing I found was this quote on
http://scienceweek.com/2005/sc050218-2.htm
"4) Despite these efforts, it remains difficult to calibrate periods
older than 22,000 14C years B.P., because residual concentrations of 14C
in such samples are extremely low (a few percent of the concentration
found in modern samples). In addition, old samples have often been
altered by geochemical processes. In particular, most corals that grew
before the sea-level minimum at 21,000 calendar years B.P. suffered
intense meteoric alteration, precluding their use for 14C calibration.
The only two published reconstructions with satisfactory analytical
precision and low overall data scatter are the Lake Suigetsu record
(4,5) and the Bahamian speleothem (speleothems are cave carbonates such
as stalagmites and flowstones). However, these two records strongly
disagree. Hence, at least one of them provides an inaccurate picture of
the true calibration curve."
Which of the curves do you base your theory on?
How can you trust the dating of the Barringer crater (which seems to be
quite inaccurate) when you think that the dating of the much smaller
Odessa crater is so wrong?
Describe how infra red (long wave heat radiation) could lead to proton
release and how it could be "concentrated in a small enough region".
In which way would protons released create a spike in 10Be?
You have reserved the right of being wrong and I think you are. Whenever
some data doesn't match your theories you try to come up with an
imaginary process that in a magical way will make it fit.
Excuse me for being blunt, but I always try to combat junk science and I
think this is junk science without even an attempt of a proof.
But even I reserve the right of being wrong...
:-)
/Göran
E.P. Grondine wrote:
Hi Rob -
Yes, I have read through all that before, but the spike that gets to me is that huge spike in the INTCAL98 data right around the time of the Barringer impact.
I don't think the neutron release is related to what hits, or what is hit, but rather just the total impact energy. I wonder what the big ones like Chicxulub or Shiva or Zamanshin will show. If part of the impact energy in the form of infra-red is concentrated in a small enough region, then releases could occur.
Take the IR measured from Tunguska for example, then scale massively and
localize to points. Do we hit freeing energies?
Speaking of Beryllium, the protons released at the same time as the neutrons
should be causing spikes in 10Be as well.
In closing, I have been wrong before, and reserve the right to be wrong both
now and in the future.
E.P. Grondine
Man and Impact in the Americas
( a damn fine book, really, despite all its flaws)
"Matson, Robert D." <[email protected]>
Subject: Re: [meteorite-list] Odessa
E.P. wrote:
Take a look at the INTCAL98 14C calibration chart. Major spikes appear
to map to impacts.
"Spikes" in the C14 calibration chart can be caused by a number of
factors (including measurement uncertainty/error). But the main cause of
variability in the production rate of atmospheric C14 is simply variation in
the flux of cosmic rays. Cosmic ray intensity is modulated by both the strength
of the earth's magnetosphere and the sun's solar wind, neither of which is
constant.
"From the other side of the equation, atmospheric C12 is ALSO modulated
by earthly processes (e.g. volcanic eruptions, ocean temperature
changes)which can produce regional anomalies in the samples used to build the
radiocarbon calibration curves.
"There is no evidence that large impacts can cause nuclear reactions that
release neutrons. There isn't sufficient energy or fissionable material,
so I have difficulty coming up with a mechanism which could cause a
large spike in neutrons. I suppose if an impactor had an anomolously
high beryllium content and it happened to hit an earth location with rich
uranium deposits, then you could get a small neutron hiccup. But
siderites are very low in berrylium (< 10 parts per billion), so that's a no-go
on Odessa. Even chondrites typically have only a few hundred parts per billion.
--Rob
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