A.M. de Boer1*, E.L. Chamberlain1, J. Wallinga1
1 Wageningen University, Soil Geography and Landscape group & Netherlands Centre for Luminescence dating
Luminescence is a powerful tool for dating the burial age of sediments, and it has potential applications for sediment tracing. The method uses light sensitive signals that accumulates in grains while buried, and a main assumption for dating is that the targeted signal has been reset by light exposure (e.g., during transport) prior to burial. Insufficient signal resetting (i.e., poor bleaching) is undesired for luminescence dating but can be of value for luminescence tracing. As different luminescence signals reset at different rates, comparison of these signals yields information about the duration and mode of transport (Reimann et al., 2015). Within our NWO funded TRAILS project, we develop and validate novel luminescence tracing methods and apply them to trace the dispersion of the nourished sands in the Ameland inlet of the Wadden Sea on a basin- and site-scale. The rationale of our approach is that nourished and native grains can be distinguished by different luminescence signal resetting related to their different source and transport histories.
The principle of native and nourished grain differentiation depends on signal resetting of slow- and fast-to-bleach luminescence signals of feldspar sand grains. Infrared stimulated luminescence (IRSL) and low-temperature post-infrared IRSL (pIRIR) signals are more light-sensitive and bleach more readily than higher temperature post-infrared IRSL (pIRIR) signals. We use a novel luminescence imaging system, which stimulates 100 grains simultaneously and images the resulting luminescence signals with an electron multiplying charge-coupled device (EMCCD) instead of conventional grain-wise stimulation and photon counting with a photomultiplier tube (Kook et al., 2015). EMCCD application has the advantage that it enables repeated measurements without user interference, and it may provide extreme low-level light detection for dimmer signals. The EMCCD camera also enables us to explore the slow-to-bleach thermoluminescence (TL) signals of single-grains.
The EMCCD enables imaging of luminescence from nourished and native Wadden sea sand grains (figure 1), and results indicate that luminescence fingerprints of both populations are indeed different.
Figure 1: EMCCD camera (left), image of sand grains emitting luminescence (middle) and sand grains mounted on a measurement disc (right).
Kook, M., Lapp, T., Murray, A. S., Thomsen, K. J., & Jain, M. (2015). A luminescence imaging system for the routine measurement of single-grain OSL dose distributions. Radiation Measurements, 81, 171-177.
Reimann, T., Notenboom, P. D., De Schipper, M. A., & Wallinga, J. (2015). Testing for sufficient signal resetting during sediment transport using a polymineral multiple-signal luminescence approach. Quaternary Geochronology, 25, 26-36.