Precise 14C ages of the Vedde and Saksunarvatn ashes and the Younger Dryas boundaries from western Norway and their comparison with the Greenland Ice Core (GICC05) chronology

Abstract

ABSTRACTThe Greenland ice cores with the GICC05 chronology represent a standard for late Quaternary climate events and their ages, whereas many other palaeoclimatic archives are dependent on 14C dates. It is therefore critical to know if the ice‐core and the calibrated 14C chronologies are identical, and if not to quantify the offset between them. We present Bayesian age–depth modelling of 118 accelerator mass spectrometry 14C dates from Kråkenes Lake, calibrated using INTCAL09, that provide high precision ages of 12 066 ± 42 and 10 210 ± 35 cal a BP for the Vedde and Saksunarvatn ashes, respectively. The lower and upper Younger Dryas boundaries have ages of 12 710 ± 52 and 11 546 ± 59 cal a BP, respectively. The four dated levels coincide with correlative levels in GICC05 within the dating uncertainties, but are all consistently younger at Kråkenes. The ages of the tephra chronostratigraphic markers suggest a mean offset of ∼70 years to older ages in the GICC05 compared with the INTCAL09 time scale. Responses to small climate changes ∼30 years before the Younger Dryas boundaries at Kråkenes are suggested to correspond to the defined Greenland Stadial 1 boundaries. This suggested difference in timing (30 years) and time scale offset (70 years) mean that the Greenland Stadial 1 boundaries appear ∼100 years older than the Younger Dryas boundaries.