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

Abstract

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 26 undated sedimentary units belonging to 23 sequences on the southern, western, and northern coasts of this Atlantic region of W Europe. 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 ages calculated in this work, ranging from 350,000 to 16,000 years ago, define a timeline for the formation of these coastal sediments during the Late Pleistocene. More specifically, alluvial and slope deposits formed during the regressive episode of the Upper Pleistocene, providing key data for a better understanding of the morphological changes along the Brittany coast 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 ultimate interglacial episode previous to the present one (Holocene).