--John
Re: Pagano, Humphreys, Radiocarbon, & Ordovician
...
check out the data from the Feb. 20, 1998
issue of Science (Vol. 279, pp. 1187-1189) available at
http://www.sciencemag.org/cgi/content/full/279/5354/1187
Here's just a snippet to whet your appetite:
Here we present a high-resolution atmospheric radiocarbon calibration from
annually laminated sediments for the total range of the radiocarbon dating
method [<45,000 cal yr B.P. (10)]. The sediments were taken from Lake
Suigetsu (35”35N, 135”53E) near the coast of the Sea of Japan (11). ...The
seasonal changes in the depositions are preserved in the clay as thin
laminations or varves. The sedimentation or annual varve thickness is
relatively uniform, typically 1.2 mm/year during the Holocene and 0.61
mm/year during the Glacial. The bottom age of the SG core is estimated to be
older than 100,000 years, close to the beginning of the last interglacial
period.
To reconstruct the calendar time scale, we counted varves, based on
gray-scale image analyses of digital pictures, in a 10.43- to 30.45-m-deep
section, producing a 29,100-year-long floating chronology. Because we
estimated the varve chronology of older than ~20,000 yr B.P. (19-m depth of
SG core) by counting in a single core section, the error of the varve
counting increases with depth, and the accumulated error at 40,000 cal yr
B.P. would be less than ~2000 years, assuming no break in the sediment (12).
....
> -----Original Message-----
> From: evolution-owner@udomo2.calvin.edu
> [mailto:evolution-owner@udomo2.calvin.edu]On Behalf Of Karen G. Jensen
> Sent: Tuesday, March 03, 1998 12:19 PM
> To: evolution@calvin.edu
> Subject: Re: New Carbon-Dating fine-tuning
>
>
>
>
> Has anyone found any scientific articles on this lake yet?
>
> It would be good to look at the original data..
>
> K
>
> ---------
>
> Mon, 23 Feb 1998 21:00:48 -0600 John Rylander wrote:
> >I thought some of you might find this interesting. --John
> >
> >http://www.abcnews.com/sections/science/DailyNews/carbon0220.html
> >
> >By Kenneth Chang
> >ABCNEWS.com
> >Feb. 23 ÷ Each spring, tiny plants bloom in Lake Suigetsu, a small body
of
> >water in Japan. When these one-cell algae die, they drift down, shrouding
> >the lake floor with a thin, white layer..
> > The rest of the year, dark clay sediments settle on the bottom. The
> >alternating layers of dark and light count the years like tree rings..
> >
> >.....
> >
> > Cores taken from Suigetsuās lake bottom avoid that problem. Counting
> >the thin white layers of dead algae, each less than a millimeter thick,
gave
> >the researchers the year, which could then be compared to the date
obtained
> >by carbon dating, back to 43,000 B.C..
>
>
>
>
>
>