> Audrey Wrote:
BETA ANALYTIC LABORATORY
> > One of the basic assumptions in carbon-14
> > is that the sample being analyzed has undergone
> > only radioactive decay and has remained
> > by any other process over the years since it
> > ceased interaction with the biosphere.
> > This assumption, however, is rarely true. The
> > archaeological artifacts and geological
> > sent to labs for radiocarbon dating are usually
> > found embedded or buried with other materials
> > may have affected their radiocarbon content.
> > carbon-containing material that affects the
> > 14 content of any given sample is therefore a
> > contaminant.
> > The occurrence of contamination can be natural
> > artificial. Natural contamination pertains to
> > introduction of contaminants to the sample by
> > surrounding material. For example, bone samples
> > can be contaminated by the presence of
> > or organic acids in the soil (like humic or
> > acids) where the bones were found. Another
> > of a natural contaminant is plant root
> > on wood, charcoal, or soil.
> > Artificial contamination refers to the
> > introduction of contaminants by man during the
> > collection, field conservation, or packaging of
> > the samples. Labeling of bone samples with
> > glue is an example of artificial contamination.
> > Other contaminants that may be introduced
> > sample collection and packaging are biocides,
> > conservation chemicals like polyvinyl acetate
> > polyethylene glycol, cigarette ash, and labels
> > wrappers that are made of paper.
> Yeah, that didn't come out right as I was only
> thinking after pretreatment, sorry. Ironically, it
> still does not change the point as it applies even
> more so to samples contaminated in the field. So
> as it pertains to field collection this would mean
> that all 400+ samples between 2 studies taken
> 11yrs apart were contaminated the same way with
> the same basic amounts of modern carbon to make
> them all fall within the same contaminated date
> range that just so happens to be c 4,000-2,000BC
> which according to your chart below would require
> 50% modern contamination or more for every single
> sample to make 18,000BC into 3,000BC.
> > It must be plausible because they have charts
> > it.
> What is implausible Audrey is for this to
> happen amongst 400+ samples from 2 different
> studies taken 11yrs apart. For a sample to be
> 18,000BC or more to get it to c. 3,000BC its
> modern contamination would need to be 50%. You
> also quote the pretreatment part where they
> specifically examine each sample to remove such
> contaminants to avoid this very contamination. If
> all these samples were collected with fingers,
> stowed away in shirt pockets, and the whole sample
> used as it was found there would be an argument to
> be made, but obviously this is not how it is done.
> It is the job and the expertise of the lab to
> ferret out and test the most pristine section of
> the sample. You guys are harping on this as if it
> were only one sample and one test but it was over
> 400 over 2 different collections and they all say
> the same thing.
Hi, Lee. I have a quick question. What direct experience with radio carbon dating do you have?
Edited 1 time(s). Last edit at 14-Jul-16 12:46 by OCaptain.