The radiocarbon chronology and temporality of the megalithic cemetery of Los Millares (Almería, Spain)

People usually study the chronologies of archaeological sites and geological sequences using many different kinds of evidence, taking into account calibrated radiocarbon dates, other dating methods and stratigraphic information. Many individual case studies demonstrate the value of using statistical methods to combine these different types of information. I have developed a computer program, OxCal, running under Windows 3.1 (for IBM PCs), that will perform both 14C calibration and calculate what extra information can be gained from stratigraphic evidence. The program can perform automatic wiggle matches and calculate probability distributions for samples in sequences and phases. The program is written in C++ and uses Bayesian statistics and Gibbs sampling for the calculations. The program is very easy to use, both for simple calibration and complex site analysis, and will produce graphical output from virtually any printer. Show more

This paper highlights some of the main developments to the radiocarbon calibration program, OxCal. In addition to many cosmetic changes, the latest version of OxCal uses some different algorithms for the treatment of multiple phases. The theoretical framework behind these is discussed and some model calculations demonstrated. Significant changes have also been made to the sampling algorithms used which improve the convergence of the Bayesian analysis. The convergence itself is also reported in a more comprehensive way so that problems can be traced to specific parts of the model. The use of convergence data, and other techniques for testing the implications of particular models, are described. Show more

The detailed radiocarbon agevs.calibrated (cal) age studies of tree rings reported in this Calibration Issue provide a unique data set for precise14C age calibration of materials formed in isotopic equilibrium with atmospheric CO2. The situation is more complex for organisms formed in other reservoirs, such as lakes and oceans. Here the initial specific14C activity may differ from that of the contemporaneous atmosphere. The measured remaining14C activity of samples formed in such reservoirs not only reflects14C decay (related to sample age) but also the reservoir14C activity. As the measured sample14C activity figures into the calculation of a conventional14C age (Stuiver & Polach 1977), apparent14C age differences occur when contemporaneously grown samples of different reservoirs are dated. Show more