Statistical Problems in Calibrating Radiocarbon-Dates

The transformation of radiocarbon years to calendar years (cal AD/BC) is not straightforward because of past variations in atmospheric 14C content (de Vries 1958; Suess 1970). A calibration curve, y = f(x), transforms each dendrochronologically dated calendar age (x) to a 14C date (y). By inverting this relationship, one can determine the calibrated calendar age of a given sample. In some time intervals, the calibration curve is problematic in that f(x) is not uniquely invertible (Fig. 1); even an exact measurement of y cannot be converted to a single calendar age (see examples in van der Plicht & Mook (1987)).