But what if we want an absolute date? What about Carbon-14 dating? Carbon-14 (C-14) is a laboratory method which measures the amount of radioactive decay which has occurred in an organic material. Unfortunately, not only is our pot made of inorganic material, but there was no such material found alongside it in the pithos (it seems that the pithos was abandoned when it became empty, with no thought even to saving the dipper, an ominous scenario). If we had found any fragments of charcoal or wood together with our pot we could supplement C-14 dating with a dedrochronology study, or tree-ring dating-- which is based on assigning specific years based on the specific sequence of annual growth in trees from a given region. Our last hope for an absolute date is to use thermoluminescence dating, the best technique for dating ceramics. With permission from the museum authorities, |
we take a small plug of material from the base of the pot and send it to the lab. The sample is superheated and then the amount of a certain type of luminescence is measured. This "glow" is caused by an accumulation of gamma rays escaping from the material under heating. The more time that has elapsed since the original firing of the ceramic, the greater the gamma ray accumulation and "glow." However, we must be cautious with our absolute date derived from thermoluminescence (TL). The average margin of error is +/- 260 years. This is not of great use for us because, using shape seriation, we have already pinpointed our pot to Troy VI, a period itself hardly longer than 500 years. But the TL date is helpful in validating our other observations. All in all, archaeologists have about a dozen different methods for relative dating and about fourteen methods for absolute dating. |
For different reasons, at any given archaeological site, some methods will be appropriate and others will not. It is one of the most important jobs of the scientists involved to understand and pick the most useful methods. And who knows? The next generation of archaeologists in the field might have access to many newer and better methods. That's not at all surprising if we consider that in the 1930s when Carl Blegen was digging at Troy, about the only absolute method available to him was an Egyptian calendar already over 25 centuries old and fairly imprecise for the early Bronze Age. |
