Making the calibration

    To correct for these variations, we must calibrate the raw "radiocarbon age" against material of known age. The first calibration curve were based on tree rings of known age, this had now been extended to corals (independently dated by U-Th) and annually-laminated sediments [Stuiver et al. 1998]. Some portions of the calibration curve are smooth; in these regions, we can obtain a "calibrated age", with an error similar to the measurement error for the "raw" age. At other points, fluctuations or "wiggles" in the curve can result in points where a line of constant radiocarbon age intersects the calibration curve in several places. In this case we may need to include several discrete age intervals, and this can result in a larger range of possible calibrated age than would be expected from the errors in the measured radiocarbon content alone. In these cases, the smallest possible error in the original measurement is advantageous, but this may not reduce the range of the calibrated age by much.