[meteorite-list] Hypervelocity impacts and neutron spallation

Mon Nov 2 21:03:36 EST 2009

On Oct. 30, 2009 and in Hypervelocity impacts and neutron spallation 
( http://six.pairlist.net/pipermail/meteorite-list/2009-October/057772.html ) 
E.P. Grondine wrote: 

"This would all be blue sky, but for those 14C spikes... Chris, 
I think I got the copy of the INTCAL98 chart from one of 
Firestone's papers. Stuiver and Volcker (working with Iceland 
marine data) were cited as the data sources. Firestone did not 
create the INTCAL98 chart. The bumps around 10,900 BCE 
were what set Firestone off on his search to find their source, 
which led him at first to a nearby supernova and finally to impact." 

First a good reference on radiocarbon dating and calibration is: 

Hajdas, I., C. Kull, and T. Kiefer, 2006, 14C-Chronology. 
PAGES News. vol. 14, no. 3. 

http://www.pages-igbp.org/cgi-bin/WebObjects/products.woa/wa/product"id=276 
15 MB version http://www.pages-igbp.org/products/newsletters/NL2006_3high_res.pdf 
4 MB version http://www.pages-igbp.org/products/newsletters/NL2006_3low_res.pdf 

Full references 
http://www.pages-igbp.org/products/newsletters/ref2006_3.html 

In the above publication, there is an article, "Cosmogenic 
isotope 14C: Production and carbon cycle" by K. Hugen, 
that discusses the processes that created the radiocarbon 
spikes. He states that the changes in 14C concentration 
(14C) are "due to changes in either the rate of 14C production 
in the atmosphere (a function of geomagnetic field intensity 
and solar variability), or the distribution of 14C between 
different reservoirs in the global carbon cycle (primarily deep 
ocean ventilation). In the Greenland ice cores there is a strong 
correlation between the production of beryllium 10 and 14C, 
which demonstrates that the radiocarbon spikes are related to 
changes in the geomagnetic field intensity associated with the 
Laschamp and Mono Lake geomagnetic minima." 

Some relevant papers are: 

Hughen, K., S. Lehman, J. Southon, J. Overpeck, O. Marchal, 
C. Herring, and J. Turnbull, 2004, 14C Activity and Global 
Carbon Cycle Changes over the Past 50,000 Years. Science. 
vol. 303, no. 5655, pp. 202-207 DOI: 10.1126/science.1090300 
http://www.sciencemag.org/cgi/content/abstract/303/5655/202 
http://courses.washington.edu/proxies/Hughen-Cariaco_14C_0-50ka_Sci04.pdf 

The abstract, in part, for this paper reads: 

"Reconstructed 14C activities varied substantially during the 
last glacial period, including sharp peaks synchronous with 
the Laschamp and Mono Lake geomagnetic field intensity 
minimal and cosmogenic nuclide peaks in ice cores and marine 
sediments. Simulations with a geochemical box model suggest 
that much of the variability can be explained by geomagnetically 
modulated changes in 14C production rate together with 
plausible changes in deep-ocean ventilation and the global 
carbon cycle during glaciation." 

Hughen, K. A., J. R. Southon, S. J. Lehman, and J. T. 
Overpeck, 2000, Synchronous Radiocarbon and Climate 
Shifts During the Last Deglaciation. Science. vol. 290, 
pp. 1951-1954. 
http://www.whoi.edu/cms/files/llippsett/2007/1/1951_17123.pdf 
https://darchive.mblwhoilibrary.org/browse?value=Hughen%2C+K.&type=author 

It abstract states: 

"Carbon-14 and published beryllium-10 data together 
suggest that concurrent climate and carbon-14 changes 
were predominantly the result of abrupt shifts in deep 
ocean ventilation." 

Chiua, T.-C., R. G. Fairbanks, L. Cao, and R. A. 
Mortlock, 2007, Analysis of the atmospheric 14C record 
spanning the past 50,000 years derived from high- 
precision 230Th/234U/238U, 231Pa/235U and 14C dates 
on fossil corals. Quaternary Science Reviews. vol. 26, 
no. 1-2, pp. 18-36. 
http://dx.doi.org/10.1016/j.quascirev.2006.06.015 
http://radiocarbon.ldeo.columbia.edu/pubs/2007_Chiu.pdf 

Muscheler, R., J. Beer, P. W. Kubik, and H. A. Synal, 
2005, Geomagnetic field intensity during the last 
60,000 years based on 10Be and 36Cl from the Summit 
ice cores and 14C. Quaternary Science Reviews. vol. 24, 
pp. 1849-1860. 
http://dx.doi.org/10.1016/j.quascirev.2005.01.012 

Ice Core Data on Climate and Cosmic Ray Changes by Dr. J. 
Beer, Federal Institute of Environmental Science and Technology, 
EAWAG, CH-8600 Dubendorf, Switzerland. 
http://cdsweb.cern.ch/record/557154/files/p3.pdf 

The caption to Figure 7 of the above paper states: 
"Figure 7: 14C peaks corresponding to periods of
low solar activity and possibly also reduced solar 
irradiance." 

Ramsey, C. B., 2008, Radiocarbon Dating: Revolution' 
in Understanding. Archaeometry. vol. 50, no. 2, 
pp. 249-275. 
http://www.arch.unipi.it/Arias/Materiali_Web/Radiocarbonio/Ramsey_2008_C14%20dating

A number of papers about radiocarbon calibration can 
be found in "Prof. Richard Fairbanks Publications" at; 
http://www.radiocarbon.ldeo.columbia.edu/publications/index.htm

Yours,

Paul H.