OSL signal resetting in young deposits determined with a pulsed photon-stimulated luminescence (PPSL) unit

Abstract

Optical Stimulated Luminescence (OSL) is a technique that can be used for dating geological materials deposited within the last half-million years, including sediments transported by air, water or gravity, as well as rocks heated at high temperatures. Recently, several studies have shown that OSL can also provide information on sediment transport. The pulsed photon-stimulated luminescence (PPSL) unit (also known as a portable OSL reader) developed by the Scottish Universities Environmental Research Centre is an instrument designed to read luminescence signals from bulk (untreated) sediment samples comprising poly-mineral and poly-grain fractions. In this contribution, we evaluate the potential of the PPSL unit to assess the degree of OSL signal resetting in 27 young deposits (<2 ka) transported by different geomorphic agents in volcanic, coastal and fluvial depositional settings located in Mexico. Our results are in agreement with previous findings that used the Riso TL/OSL reader, confirming that sediments transported by debrisflows contain the highest inherited luminesce signals. Infrared stimulation (IRSL) values in volcanic ash, lavas, and sand beach and dune deposits exhibit low scatter. However, with blue stimulation (BLSL) these samples reveal a large degree of scattering, attributed to charge transfer in the case of the coastal deposits and to the low sensitivity of quartz in the case of volcanic material. The luminescence signals of fluvial sediments exhibit a highly scattered distribution in both IRSL and BLSL. We conclude that the use of a PPSL unit is a simple approach to assess the degree of OSL signal resetting in deposits sourced from different geological environments. This research contributes to previous studies that have investigated new applications of the PPSL unit to assist in OSL dating of geological materials.