Infrared stimulated luminescence dating of 19^th century fluvial deposits from the upper Rhine River

Abstract

Knowledge of the age of fluvial deposits is an important aspect in the understanding of river dynamics, which is pre-requisite for sustainable river management and restoration back to more natural conditions and processes. Presented here is a case study on using feldspar Infrared Stimulated Luminescence (IRSL) to date low-energy fluvial sediments that formed after correction of the Upper Rhine River in the first half of the 19th century. A rigorous testing programme is carried out to characterise the IRSL properties of the samples, including thermal transfer, dose recovery and fading. All samples reveal complex distributions of equivalent dose, implying the presence of differential bleach-ing in the samples. It is shown that multi-grain aliquots overestimate the known-age by up-to 200 years, i.e. apparent IRSL ages are twice as old as the true age of the sediment. The use of single grains results in ages that are in excellent agreement with the expected age, therefore the age overestimation in multi-grain aliquot measurements is likely explained by signal averaging effects. While the application of single grains appears mandatory for dating young low-energy fluvial deposits, the small absolute offset associated with the multi-grain approach might be acceptable when dating sediments of such type that are older than a few 1000 years.

Long-term river trajectories to enhance restoration efficiency and sustainability on the Upper Rhine: an interdisciplinary study (Rohrschollen Island, France)

“…According to the location of pit 1 (Fig. 4-a, median bar on 1828 map) and the depositional history deduced from historical maps, the resetting of the IRSL signal in basal sediments of pit 1 resulted from this major lateral migration (Preusser et al, 2016). In accordance with the IRSL dates, 10 deposition of fine grained sediments in the lower part of pit 1 took place between 1778 and 1806 ( Fig.…”

“…According to our chronology, pit 1 -SU 2 was already deposited at this time (Preusser et al, 2016). This SU is composed of silt deposited during low energy conditions (tag 6; Fig.…”

“…This is explained by partial resetting of the IRSL signal prior to deposition and masking effects when measuring several 25 grains at the same time. Presented here are the results previously published by Preusser et al (2016) from pit 1 together with additional samples taken from pit 2 (Table S1). For the new data, we again observed significant older ages when measuring several grains at the same time for most of the samples.…”

“…The maximum age of the investigated sediments in pit 1 is therefore 238-210 years (i.e. 1777-1805; Preusser et al, 2016). The 1828 map in figure 4-a shows that pit 2 is located in the 1828 main channel and accumulation of fine sediments must have commenced after this time.…”

“…The detailed 20 procedures and methodological aspects are discussed in Preusser et al (2016). In summary, IRSL (stimulated at 50°C) of sandsized feldspar grains was measured applying both small aliquot (ca.…”