Calibration technique for (super 14) C data clusters; fitting relative chronologies onto absolute time scales.

Abstract

Application of radiocarbon dating to a short chronology is often limited by the wide probability ranges of calibrated dates. These wide ranges are caused by multiple intersections of the (super 14) C age with the tree-ring curve. For a single unrelated (super 14) C date, each intersection presents a probable solution. When several dates on different events are available, identification of the most probable solution for each event is possible if one can obtain some information on the relation between these events. We present here a method for such identifications. To demonstrate the method, we selected a series of (super 14) C dates from mortuary monuments of the Egyptian Old Kingdom. Corrected (super 14) C dates from seven monuments were used. Calibration of these dates produced three absolute ages with single intersections and four ages with 3-5 intersections. These data are compared to a historical chronology, which places the dated events at a younger age. If each intersection is chosen as a potential anchor point of the "correct" chronology, 17 solutions must be tested for the best fit against the historical chronology. The latter is based on the length of the reign of each pharaoh during the studied time span. The spreadsheet has the function of determining the probability of fit for each of the solutions. In a second step the 17 probability values and their offset between the historical and the (super 14) C chronology are graphically analyzed to find the most probable offset. This offset is then applied as a correction to the estimated chronology to obtain an absolute time scale for the dated events.