Rates of change and chronological problems during the late-glacial period

Results of high-resolution AMS ¹⁴C dating of terrestrial plant macrofossils from late-glacial and early-Holocene lake deposits in Switzerland show three periods with constant radiocarbon ages. These plateaux of constant age occur at 12700, 10000, and 9500 y BP. A comparison of this radiocarbon chronology with a varve chronology documents discrepancies between the sidereal and the radiocarbon time-scale for the late-glacial period. The age-plateaux and the time-scale discrepancies have a significant impact on the estimation of rates of change during this period: estimates of rates of change can be very misleading if calculated on the basis of radiocarbon ages. This is illustrated by an example of estimated rates of late-glacial and early Holocene palynological change in Switzerland.Contribution to Clima Locarno — Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program