A piece of wood was fossilized in the Hawkesbury Sandstone, Australia,
which most geologists date to the middle Triassic, about 225 to 230
million years ago. The wood was dated by Geochron (a commercial dating
laboratory) using the carbon-14 method. Geochron determined its age to be
only 33,720 +/- 430 years before present. Contamination by recent
microbes or fungi cannot explain the discrepant age.
It is doubtful that the sample was even wood. Snelling was not even
sure what the sample was. Nor could the staff at Geochron tell what
the sample was (Walker 2000). It may not even have retained any of
its original carbon. Using carbon dating was pointless from the
start since it would inevitably give meaningless results.
The sample was porous, making it likely that it would have absorbed
organic carbon from the groundwater. It was probably this
contaminating carbon that produced the date. Another possibility is
that some 14C was created in situ by natural radioactivity
in the surrounding rocks (Hunt 2002).
Furthermore, 33,720 years is still significantly older than the age
which many creationists, Snelling included, ascribe to the earth, and
there are no plausible sources of error to make the age younger than
33,000 years.
Links:
Meert, Joe, 2003. Andrew Snelling and the iron concretion?
http://gondwanaresearch.com/hp/crefaqs.htm#who
(Includes a letter from GeoChron labs saying that the "wood" looked like
an iron concretion)