Calibration of the radiocarbon time scale for the Southern Hemisphere; AD 1850-950.

Abstract

We have conducted a series of radiocarbon measurements on decadal samples of dendrochronologically dated wood from both hemispheres, spanning 1000 years (McCormac et al. 1998; Hogg et al. this issue). Using the data presented in Hogg et al., we show that during the period AD 950-1850 the (super 14) C offset between the hemispheres is not constant, but varies periodically ( approximately 130 yr periodicity) with amplitudes varying between 1 and 10 per mil (i.e. 8-80 yr), with a consequent effect on the (super 14) C calibration of material from the Southern Hemisphere. A large increase in the offset occurs between AD 1245 and 1355. In this paper, we present a Southern Hemisphere high-precision calibration data set (SHCa102) that comprises measurements from New Zealand, Chile, and South Africa. This data, and a new value of 41+ or -14 yr for correction of the IntCal98 data for the period outside the range given here, is proposed for use in calibrating Southern Hemisphere (super 14) C dates.