<< Previous Chapter: Overview


Chapter 2: Determining Age: ESR, Radiocarbon and TL

Page: 1   2

The best materials for radiocarbon are charcoal samples, usually wood charcoal from fireplaces. Charcoal in a hearth Radiocarbon dating is based on the fact that plants absorb carbon from the atmosphere, and, in the case of animals, this carbon is obtained from the plants they eat. Some carbon is nonradioactive (carbon-12 or 12C), while other carbon is radioactive (carbon-14 or 14C). The ratio of 14C to 12C in a living animal or plant will be very similar to the ratio present in the earth's atmosphere. When a plant or animal dies, carbon absorption stops, and the 14C present in the plant or animal begins to decay at a known rate. By measuring the amount of remaining 14C in a sample such as wood charcoal, the 14C to 12C ratio of that sample can be calculated and a date determined. The 14C to 12C ratio in the earth's atmosphere, however, hasn't remained constant through time. Scientists have been able to correct or calibrate these fluctuations in the ratio back to a bit more than 12,000 years ago, so that our dates in this time range are relatively accurate. For radiocarbon dates between about 12,000 and 45,000 years ago, there is a small amount of unknown offset, with some samples likely dating slightly older or slightly younger than their true age. At Pech IV, we collect charcoal samples whenever we can, even from layers of the site that are much older than the range of time that can be dated using the radiocarbon method. We do this because we expect that improvements to the radiocarbon technique may occur so that the range of time it dates is extended much farther back into the past. When this happens, the samples from these older occupations can then be used by future researchers to obtain additional dates.


1   2 ... Next Page >>

Next Chapter: The Total Station >>