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Types of Chronological Information

The types of information which can be used to make chronological inferences can be divided into two broad categories: the first are the age measurements themselves and the second are the stratigraphic relationships (see Harris) between samples. Our knowledge about the actual age of archaeological artifacts can come from a variety of sources: All of these different types of information can be introduced into an archaeological model built with OxCal.

See also [Program Operation]

Historical Information

Some artifacts such as coins can be directly dated by using information from the historical record. Such information can usually be written in terms of a specific year () perhaps with an error term associated with it (given in this program as one standard deviation).

See also [Program Operation] [Example] [Mathematical Methods]

Radiocarbon Dates

Radiocarbon dates must be calibrated in order to use them in conjunction with other techniques or if any chronological inferences (such as the length of phases) are to be made(see Bowman 1990 or Aitken 1990). These are entered in this program as radiocarbon dates () with an error quoted as one standard deviation (the form used by all radiocarbon laboratories). It is assumed that any laboratory multiplier has already been applied.

See also [Program Operation] [Example] [Mathematical Methods]

Luminescence Dates

The methods of thermo-luminescence (TL) and optically stimulated luminescence (OSL) dating are particularly important beyond the range of radiocarbon or in the many sites where preservation of organic material is poor. Both methods are a measure of accumulated radioactive dose from a site since the samples were subjected to heat (TL) or sunlight (OSL). The raw results can be entered into this program by defining the year of measurement () the site dose rate () and associated error () and then entering the measured doses received by the samples which yield a calendar age (). Alternatively since the laboratories will frequently give the results in the form of calendar ages they can simply be entered in the same way as historical information.

One feature of luminescence dates is that they sometimes have asymmetric errors associated with them these can also be entered by either method.

See also [Program Operation] [Mathematical Methods]

Other Dating Methods

Information from other dating methods such as dendro-chronology or Uranium series can usually be entered in the form of calendar dates () possibly with asymmetric errors.

Other Information

There may also be other forms of information which you wish to include in a study. Many of these it will be possible to write in the form of calendar ages in conjunction with `stratigraphic' information. It is also possible with this program to define your own probability distributions and use them in the analysis ().

Dating Simulation

Because of the variable nature of the radiocarbon calibration curve it is often difficult to predict beforehand how good a set of radiocarbon dates are likely to be in answering a set of archaeological questions. This program incorporates a technique () for generating a radiocarbon date (with random but realistic errors) given the calendar age expected and the error term that the radiocarbon lab is capable of providing. Using this it is possible for the archaeologist to try out different possible dating programs and see how much information he is likely to be able to gain from them.

See also [Program Operation] [Example]