All 14C radiocarbon dates with the ETH lab code were measured for this study as gas samples at the Laboratory for Ion Beam Physics, ETHZ; other codes are for 14C dates measured using the traditional AMS 14C method. All 14C were calibrated using the Marine13 dataset (Reimer, 2013) and a DeltaR of 140 ± 35 years was applied in the age modelling software BACON. Maximum and minimum ages represent the 95% (2Sigma uncertainty) in the age model.** 14C dates that were considered outliers and thus removed from the final age model presented here (see supplementary information for details).