PROBLEMS IN THE CALIBRATION OF THE LATE PLEISTOCENE RADIOCARBON TIME SCALE

The purpose of the radiocarbon calibration process is to convert an age estimate based on a measurement of residual radiocarbon content in a sample expressed in terms of a set of conventions (a conventional radiocarbon age) into an calibrated radiocarbon age estimate that expresses solar time equivalents for conventionally-expressed radiocarbon values. For Holocene materials, comparison of paired radiocarbon and dendrochronological data provides the primary basis to document secular variations in the radiocarbon time spectrum. For the late Pleistocene, paired uranium/thorium and radiocarbon values have been used to examine the characteristics of radiocarbon/solar time offsets. In contrast to the consensus concerning the accuracy and precision of the dendrochronological data base documenting the characteristics of the Holocene radiocarbon time scale, there are a several problems and issues that need to be considered when evaluating the accuracy and precision of the data base used to infer late Pleistocene solar time offsets for conventional radiocarbon ages. We will examine some of these problems with particular attention to the evaluation of accuracy and precision of the calibration data for samples deriving from the period bracketing the Holocene/Pleistocene boundary.