Integrating age information from different localities for stratigraphic marker beds: application to the Eltville tephra (Western Europe)

Abstract

Stratigraphic marker beds are often used in geosciences for regional and global correlation. For various reasons dating those layers directly proves to be difficult sometimes. In those cases ages from above and below such a horizon represent minimum- and maximum-ages. These are often determined from more than one location and this gives the possibility to combine these ages, test their consistency and finally derive an age in agreement with the findings from most localities. We present a novel approach to integrate the age information from different localities and produce a combined age consistent with both stratigraphy and most of the dating results. Such an approach relies on few assumptions, most importantly the correctness of ages and their reported uncertainty.
The Eltville Tephra derived from an unknown eruption in the Eifel volcanic field is an important maker bed in Rhine-Meuse Area nearby the boundary between the deposition of reworked and primary loess during the LGM (ca. 20 ka). The Eltville Tephra is usually imbedded in loess and dates from directly above and below come almost exclusively from luminescence dating. As different luminescence dating techniques were applied to samples over- and underlying the Eltville Tephra, a systematic bias towards younger or older ages of the sum of these techniques seems unlikely. Therefore all reported ages may be taken into account for a simulation allowing only for ages consistent with stratigraphy, i.e. ages from above the Eltville Tephra being younger than ages below this regional marker bed. However, some datasets are clearly inconsistent with geochronology due to unknown reasons. These can be excluded from statistical experiments to obtain a more precise result.
Here we present the statistical approach to deal with ages from various localities, demonstrate its potential using well understood artificial data, and also apply it to obtain a datum for the Eltville Tephra with a reproducible uncertainty. This has the potential to improve on existing dates for various other stratigraphic marker beds especially in the terrestrial realm, where often dates for (or around) correlative sediments are obtained from various localities.

Resources

Bibliography

Zeeden, C., Zens, J., Krauß, L., Lehmkuhl, F. (2014): Integrating age information from different localities for stratigraphic marker beds: application to the Eltville tephra (Western Europe). Loessfest 2014, Wrocław, Poland