Radiocarbon simulation fails to support the temporal synchroneity requirement of the Younger Dryas impact hypothesis

Fine-scale temporal processes, such as the synchronous deposition of organic materials, can be challenging to identify using 14C datasets. While some events, such as volcanic eruptions, leave clear evidence for synchronous deposition, synchroneity is more difficult to establish for other types of events. This has been a source of controversy regarding 14C dates associated with a hypothesized extraterrestrial impact at the Younger Dryas Boundary (YDB). To address this controversy, we first aggregate 14C measurements from Northern Hemisphere YDB sites. We also aggregate 14C measurements associated with a known synchronous event, the Laacher See volcanic eruption. We then use a Monte Carlo simulation to evaluate the magnitude of variability expected in a 14C dataset associated with a synchronous event. The simulation accounts for measurement error, calibration uncertainty, “old wood” effects, and laboratory measurement biases. The Laacher See 14C dataset is consistent with expectations of synchroneity generated by the simulation. However, the YDB 14C dataset is inconsistent with the simulated expectations for synchroneity. These results suggest that a central requirement of the Younger Dryas Impact Hypothesis, synchronous global deposition of a YDB layer, is extremely unlikely, calling into question the Younger Dryas Impact Hypothesis more generally.