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Chapter 5: Establishing Chronology

Another focus of the research at Pech IV is establishing a chronology for the occupations at the site. To accomplish this, we collect several types of dating samples because each dating technique requires different materials. We also gather information about their spatial location in the site by recording their position using the total station.

We think that the latest set of Neandertal occupations at Pech IV, which yielded the Mousterian of Acheulian Tradition stone tools, has the potential to fall within the range of time that can be dated using the radiocarbon dating technique. Radiocarbon is based on using organic materials such as charcoal, but it extends only about 45,000 years into the past. (Read more about Radiocarbon dating)

For periods of time earlier than 45,000 years ago, including the Neandertal occupations in the lower deposits at Pech IV, there are two other dating techniques that can be used. The first of these is thermoluminescence (TL), which was originally developed as a way to date pottery. (Read more about TL dating) Of course, pottery does not occur in the Neandertal sites of the Paleolithic, but fortunately, TL can also be used to date burnt stone tools. The other isotopic or radioactive dating method is electron spin resonance (ESR), which is most often used to date animal teeth. (Read more about ESR dating)

These absolute dating techniques produce dates with a statistical uncertainty called a standard deviation. This means that radiocarbon, TL, and ESR do not yield calendar dates, but a range of time for any given dated sample. For example, a date might look like this: 25,000±500 b.p. The true age is interpreted as having a 67% chance of falling within one standard deviation of 25,000 b.p. (b.p. stands for before present), in other words, between 25,500 and 24,500 b.p. The odds increase to 96% if two standard deviations are used, for instance, 26,000 to 24,000 b.p. in the example we are using.


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