This is accomplished using wood specimens found preserved, for example, in historic buildings, or on the forest floor, or in peat bogs.
You may find it useful for the clear definitions, and for excellent links on a variety of topic.
SYNONYMS OR RELATED TERMS: coring CATEGORY: artifact DEFINITION: A black or gray zone in the interior cross-section of a vessel wall, usually associated with incomplete removal of carbonaceous matter from the clay during relatively low-temperature firing; not to be confused with black coring at high temperatures, which results from trapped gases and may lead to bloating SYNONYMS OR RELATED TERMS: nucleus CATEGORY: lithics DEFINITION: A piece of stone used as a blank from which flakes or blades were removed by prehistoric toolmakers.
Usually it was the by-product of toolmaking, but it may also have been shaped and modified to serve as an implement in its own right. The core is undisturbed and the sediment contacts, soil boundaries, and structures are intact and can be described accurately.
Thanks to nuclear physics, mass spectrometers have been fine-tuned to separate a rare isotope from an abundant neighboring mass, and accelerator mass spectrometry was born.
A method has finally been developed to detect carbon 14 in a given sample and ignore the more abundant isotopes that swamp the carbon 14 signal.