Feasibility study of quartz ESR dating for sediments in northern Switzerland

Fluvial and glaciofluvial sediments in the Northern Alpine Foreland record detailed history of the Quaternary glaciations and climatic changes. These sediments and associated landscapes have been typically classified using the Penck and Brückner’s concept for four terrace levels; the so-called Niederterrasse, Hochterrasse, Tiefere Deckenschotter and Höhere Deckenschotter. Sediments of Niederterrasse and Hochterrasse were dated using quartz and feldspar luminescence dating, however, older sediments (Tiefere and Höhere Deckenschotter) are beyond the upper limit of the method and are difficult to date. In this study we tested the feasibility of quartz electron spin resonance (ESR) dating using the Ti centre for sediments from northern Switzerland.

Eight samples were used in this work; these are two modern river sands from a bank (GRUE1) and a sand bar (GRUE0) of the River Thur at Grüt, fluvial-lacustrine (BER6) and fluvial-fluviglacial (BER3) sediments from Beringen, which have OSL dates of ~25 and ~150 ka, Tiefere Deckenschotter from Hungerbol (HUNE2), and Höhere Deckenschotter from Irchel Hasli (HASE1, HASE2) and from Irchel Steig (STEE2). Quartz ESR dating was conducted using the single aliquot regenerative dose protocol using three aliquots each for the Ti-Li and Ti-H centres. Dose recovery tests were also performed using two young samples (GRUE1 and BER6) by adding ~1000 Gy on top of the natural aliquots. Dose recovery ratios were satisfactory for both samples and for both Ti-Li and Ti-H centres. The apparent ages of samples from Tiefere and Höhere Deckenschotter are in stratigraphic order, ranging from 530 to 890 ka for the Ti-Li centre. However, the residual dose obtained from modern and young samples were significant, with a mean of ~750 Gy for the Ti-Li centre and ~200 Gy for the Ti-H centre. These residual doses are corresponding to ~70 % and ~40 % of the natural equivalent dose of the Deckenschotter samples, which makes the evaluation of actual burial dose very difficult. Ages corrected for the residual dose obtained from modern and young samples result in unreasonably young ages between ~150 and ~320 ka.