Reducing time-scale uncertainty for the Devonian by integrating astrochronology and Bayesian statistics

Dealing with uncertainties is inherent to the scienti? c process.
In the process of building geologic time scales, the reported uncer-
tainties are at least as important as the estimates of the numerical
ages. Currently all time scales for the Devonian are based on conven-
tional age-depth models, constructed by linear or cubic interpolation
between different dated positions. Unfortunately, such models tend to
produce overoptimistic con? dence intervals. In this study we apply
Bayesian statistics to the Devonian time scale to better incorporate
stratigraphic and radioisotopic uncertainty. This approach yields a
Devonian time scale characterized by increasing uncertainty with
growing stratigraphic distance from a radioisotopically dated sample.
This feature is absent from The Geologic Time Scale 2012; therefore,
that time scale is overoptimistic. We further constrain the obtained
time scale by incorporating astrochronological duration estimates for
the Givetian and Frasnian stages. The combination of radioisotopic
dating and astrochronology results in a reduction of the uncertainty
on the numerical age of the stage boundaries concerned by several
million years. For example, we estimate the age of the Frasnian-
Famennian boundary at 373.9 ± 1.4 Ma.