Investigation of quartz ESR residual signals in the last glacial and early Holocene fluvial deposits from the Lower Rhine

Abstract. In this study, we examined the residual doses of the quartz electron spin resonance (ESR) signals from eight young fluvial sediments with known luminescence ages from the lower Rhine terraces. The single aliquot regenerative (SAR) protocol was applied to obtain the residual doses for both the Aluminium (Al) and Titanium (Ti) impurity centres. We show that all of the fluvial samples carry a significant amount of residual dose with a mean value of 1350 ± 120 Gy for the Al centre, 610 ± 60 Gy for the lithium-compensated Ti centre (Ti-Li), 170 ± 20 Gy for the hydrogen-compensated Ti centre (Ti-H), and 470 ± 50 Gy for the signal originated from both the Ti-Li and Ti-H centres (termed Ti-mix). To test the accuracy of the ESR SAR protocol, a dose recovery test was conducted and this confirmed the validity of the Ti-Li and Ti-mix signal results. The Al centre shows a dose recovery ratio of 1.74 ± 0.16, probably due to a sensitivity change by the thermal treatment in the SAR procedure, whereas the Ti-H signal shows a ratio of 0.56 ± 0.17. The results of this study suggest that fluvial sediments carry a significant residual dose, and therefore the subtraction of residual dose using a modern analogue is highly recommended to obtain reliable ESR ages.