Age-depth model
The age-depth model for Y99 was constructed using the StalAge algorithm. StalAge is a available for the statistical software package R (Scholz and Hoffmann, 2011). One benefit of Stalage is that it can be applied to datasets which include outliers, age inversions, hiatuses and large changes in growth rate. StalAge acts in a three-step process, which allows major and minor outliers and age inversions to be detected, and the uncertainty of potential outliers is increased using an iterative procedure. An age model and with 95%-confidence limits are calculated by a Monte-Carlo simulation, which fits an ensemble of straight lines to the age data (Scholz and Hoffmann, 2011). One age reversal (Y99-E-3) was detected both visually and by the algorithm; the reason for this age inversion is unknown. An expansion of the uncertainty did not resolve this age inversion and was thus discarded from our age-depth model. Overall, the Y99 GI-I age-depth model is based on five230Th measurements, spanning 127.811 ± 0.626 ka BP to 121.739 ± 0.561 ka BP.