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Located in the mountain range of the Pyrenees, ~100 km from the current coastline, the archaeological site of Gatzarria -- in and around a karstic cave -- has yielded an important Palaeolithic sequence, spanning from the Middle to the Upper Palaeolitic. The lithic industries identified correspond to several Middle Paleolithic technocomplexes, based either on the Levallois, the Discoid or the Quina technology, and a few Châtelperronian elements have also been identified. Several chronological variants of Aurignacian superpose the Middle Palaeolithic sequence, and the Gravettian completes the Upper Palaeolithic sequence [1]. Whereas both the Aquitaine Basin (SW France) and the Cantabrian region (North of Spain) are very rich in archaeological sites from these periods, the northwestern foothill of the Pyrenees, where Gatzarria is located, is less well known, despite a non-negligible number of sites. Similarities do however exist with the archaeological record of all three areas and raw material sourcing supports long distance movements, of objects and/or people, between them. Obtaining a numerical chronology at Gatzarria cave will thus enable us to describe population dynamics and interactions in a key region of SW Europe, the "Basque crossroads", during several key moments of the Upper Pleistocene. Here we present OSL ages obtained from 34 sediment samples collected for OSL dating and processed in the usual manner using sand-sized (180-250 µm) quartz and feldspar grains. Preliminary multigrain quartz measurements using the single-aliquot regenerative-dose (SAR) protocol show that quartz is fast-component dominated, has satisfactory luminescence characteristics and dose response curves have an average characteristic dose (Dc value) of ~70 Gy. Single-grain quartz measurement show that only about 2% of the grains give detectable luminescence signals and a significant fraction of these are in saturation on the laboratory dose response curve. Only very little K-rich feldspar is present in these samples, but comparison with quartz age will be made where possible. Age modelling will be undertaken using both the commonly applied frequentist approach as well as Bayesian modelling using the specifically designed software tool BayLum [2]. [ABSTRACT FROM AUTHOR]

In this study, we use optically stimulated luminescence (OSL) to establish a robust absolute chronology for the lower part of the stratigraphic record at "Les Roches d'Abilly", an important Palaeolithic site in Central France. There, lithic assemblages recording the Middle-to-Upper Palaeolithic transition and the behaviour of Neanderthal and Anatomically Modern Human populations are preserved. At the Bordes-Fitte rock shelter, part of "Les Roches d'Abilly", the archaeo-stratigraphic record has been sealed and preserved by the collapse of the shelter roof and this site has provided important data on the timing of human occupations and Middle-to-Upper Palaeolithic transition in this region. Here, we first obtain burial ages using standard multi-grain quartz techniques on sand-sized sediment grains and then investigate the information available in blue-stimulated luminescence-depth profiles into the surfaces of four quartz-rich cobbles found in the sedimentary record below the various collapses of the shelter roof. These profiles show qualitative evidence for past daylight exposure and a single burial event, allowing the data to be analysed quantitatively using a multiple-event mathematical model. Based on the results of this modelling, it is concluded that at least part of the cobble surfaces were well-bleached at burial and thus that estimated rock surface burial ages are unlikely to be significantly affected by incomplete bleaching. However, it appears that not all cobble surfaces were well-bleached, demonstrating the importance of only using surface doses derived from those cobble layers that can be shown to have been well-bleached at burial. The rock-surface burial ages of the most recent burial event are consistent with the quartz OSL ages derived from the surrounding sediments, giving burial ages of ∼ 50 ka. The OSL ages are consistent with previously published 14C age control, although a single 14C age (uncalibrated age of 41 , 900 ± 1 , 500 yr BP) of a lower unit may underestimate the OSL ages. This study provides a reliable absolute OSL chronology for the Bordes-Fitte rock shelter constraining the Middle-to-Upper Palaeolithic transition to occur between 44±2 ka and 48±3 ka ago (at the 68% confidence level). [ABSTRACT FROM AUTHOR]