Re: CND dating technique (ping: Eric S.)

On Mon, 10 Sep 2007 23:18:14 -0600, "Tedd Jacobs"
<t...jacobs@xxxxxxxxxxxxxxxxxxx> wrote:

durring the 1990's new techniques for dating began to appear based on the
production of isotopes in rocks at the earths surface. collectively, these
techniques are refered to as Cosmogenic Nuclide Dating. it was proposed in
1955 that cosmic rays would interact with atoms in minerals at the surface
of the earth. durring the 1980's accelorator mass spectrometry (AMS)
measurement of cosmogenically produced 14^C became possible. using simular
techniques it was possible to to measure small ammounts of of radioactive
isotopes (10^Be, 26^Al, and 36^Cl) produced in rocks. additionally, stable
cosmogenic isotopes (3^He, 21^Ne) could be measured by mass spectrometry.
the importance of these techniques is that they are able to provide dirrect
information on the exposure history of both rocks and sediment. this
provides two types of applications: i. the exposure age of a rock surface
can be measured directly because the number of atoms will be proportionate
to time (with due account of both production rate and radioactive decay),
and; ii. when rock surfaces are exposed or removed by processes it is
possible to use two isotopes with differing lifetimes to obtain information
on changes that have occured durring time.


ref.

cockburn, h.a.p., and m.a. summerfield (2004). geomorphological applications
of cosmogenic isotope analysis. in Preogress in Physical Geography, 28,
pp.1-42.

Encyclopedia of Quaternary Science (2007). S.A. Elias (ed.), Elsevier,
Amsterdam, Netherlands.
http://www.elsevier.com/wps/find/bookdescription.cws_home/712276/description#description
<or> http://tinyurl.com/2jowu3

gosse, j.c. and f.m. phillips (2001). terrestrial in situ cosmogenic
nuclides: theory and applications. in Quaternary Science Reviews, 20,
pp.1475-1560.

niedermann, s. (2002). cosmic-ray-produced noble gases in terrestrial rocks:
dating tools for surface processes. in Reviews in Mineralology and
Geochemistry, 47, pp.731-784.

zreda, m.g. and f.m. phillips (2000). cosmogenic nuclide buildup in
surfacial materials. in Quaternary Geochronology: Methods and Applications
(ed. j.s. noller, j.m. sowers, and w.r. lettis). pp.61-76. american
geophysical union, washington, DC.


Thanks Tedd. Are you able to come up with any names of people
knowledgable in this field?

Second, how well do you think these techniques will work for the sides
of holes that have spent most of their life filled with dirt and
water? Probably the best surface to test would be the rounded off edge
of the hole at the surface. It's likely not to have been sheltered too
much.

Does anyone have any thoughts?



Eric Stevens
.

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