Towards increasing the spatial resolution of luminescence chronologies – Portable luminescence reader measurements and standardized growth curves applied to a beach-ridge plain (Phra Thong, Thailand)

Abstract

Abstract Since optically stimulated luminescence (OSL) dating is time-consuming and cost-intensive, the quantity of ages available for individual study sites is usually restricted significantly. In particular the interpretation of complex depositional systems with temporally and spatially diverse sedimentation histories may suffer from the effects of a poor spatial resolution or an ineffective distribution of chronological data. In these cases, time and cost efficient approaches that provide reasonable dating accuracy are required to substitute or complement full luminescence dating. In this study, we evaluate the potential (i) of luminescence profiling using a portable luminescence reader, and (ii) of standardized growth curves applied to quartz extracts and bulk samples in a standard luminescence reader for functioning as age proxies. Since both proxies save time for processing and/or measurements, they would be applicable to larger datasets in future studies and, by this, may allow to improve the spatial resolution and sampling strategy of OSL dating in coastal settings. Both approaches are applied to a set of approximately 50 samples from the sandy beach-ridge plain of Phra Thong Island, Thailand, for which age control is given by regular quartz luminescence dating from previous studies. Results show that although standardized growth curves are also associated with shortcomings in dating accuracy, and luminescence profiling in general does not equal full luminescence dating, both approaches are capable of reproducing some of the main chronostratigraphic features of the island. This includes the differentiation between the Holocene and Last Interglacial parts of the ridge plain, as well as the identification of the general east-west progradation of the Holocene ridges. On the other hand, several pronounced hiatuses of 1500–2000 years within the Holocene sediment succession, were not identified at all or with a poor precision. More robust absolute age estimates can only be achieved by considering the highly variable dosimetry, which is the main contributing factor to bulk luminescence signals apart from deposition age on Phra Thong Island. Thus, for the beach ridges on Phra Thong portable reader signals as a proxy for palaeodoses combined with sample-specific dose rates seem to be the best compromise between rapid data acquisition and adequate dating accuracy. In future studies, this will allow for processing significantly larger numbers of samples compared to regular luminescence dating while keeping dating accuracy at a level that should be adequate for many research questions, which in the end could enable an increased spatial resolution of chronological information.