Dating of Late Pleistocene sediments along the coast of Brittany (W France) by Optically Stimulated Luminescence, paleoclimate implications and Eemian highstand

Numerous sedimentary deposits are present along the coast of Brittany (W France). It is assumed that these sequences are related to glacioeustatic variations of the Late Pleistocene, but the scarcity of reliable ages prevent accurate chronological constraints to correlate their deposition with a clearly defined paleoclimate context. In this study, the analysis of Optically Stimulated Luminescence (OSL) signals from multi-grain quartz aliquots has been conducted for the calculation of a burial age of 21 sedimentary sequences along this coast. Considering the limitations of fast-OSL signal saturation at high doses, the palaeodose estimation and dose recovery tests were analysed using Bayesian models implemented in the R package BayLum and the results compared with those obtained using frequentist procedures and models such as the central age model (CAM) or the average dose model (ADM). The calculated ages in this work, ranging from the end 350,000 to 160,000 years, define a timeline for the formation of Upper Pleistocene sediments, providing further evidence for morphological changes along the coastline during the last glacial episode. The fossil raised beaches included in this record also provide further insight into the highstands reached during the Eemian transgression (ca. 125,000 years ago), within the penultimate interglacial episode.