Multi-method luminescence dating of late Cenozoic northern Upper Rhine Graben fluvial sediments

Abstract

The Upper Rhine Graben (URG) contains one of the most continuous sequences of unconsolidated Plio-Pleistocene sediments in central Europe. In order to understand the driving factors behind the sedimentation and erosion processes of the river Rhine fluvial system as well as the geological evolution of the rift system during the Quaternary and beyond, numerical dating of the sediments is indispensable. In 2020 and 2021, the Hessian State Agency for Nature Conservation, Environment and Geology (HLNUG) carried out a new continental drilling project near Riedstadt-Erfelden in Hesse, Germany, to obtain further information on the development of the northern part of the URG. Here, we present geochronological information derived from a multi-method luminescence dating approach of samples from the upper section of the core. Preliminary results from optically stimulated luminescence (OSL) of quartz and infrared-radiofluorescence (IR-RF) of K-feldspar are complemented by new measurements using infrared-stimulated luminescence (IRSL), post-infrared-IRSL (pIRIR) and infrared photoluminescence (IRPL). The latter is a relatively novel approach with the usage of a potentially non-fading and non-destructive signal from K-feldspar. For the first time, we apply a multiple elevated temperature (MET)-pIRIR-IRPL single aliquot regenerated dose (SAR) protocol on fluvial samples and present fading rates for the IRSL and IRPL signals derived from the protocol. We find that IRPL ages agree generally well with Middle Pleistocene luminescence ages of previous studies and biostratigraphic data while showing negligible fading and less sensitivity to a varying test dose. OSL ages up to ∼65 ka match phases of aggradation reported in earlier studies. Although IRPL and IR-RF ages are thought to arise from the same dosimetric trap, discrepancies in ages observed from both signals could be due to the required difference in sensitivity correction methods, though we note that as the signals approach saturation, the ages from both methods converge (>200 ka). The pIRIR₂₂₅ and pIRIR₂₉₀ ages generally overestimate OSL and IRPL ages. Fading correction of IRSL₅₀ ages was not successful as they still underestimate quartz ages. Our results indicate an Elsterian-Holsteinian (MIS 12-11) to late Weichselian (MIS 2) age of the Mannheim formation and a Cromerian (MIS 13–21) deposition of the Ludwigshafen formation.