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Vila Nova de Foz, Portugal

Thomsen K.J.,Technical University of Denmark | Murray A.S.,University of Aarhus | Buylaert J.P.,Technical University of Denmark | Buylaert J.P.,University of Aarhus | And 3 more authors.
Quaternary Geochronology | Year: 2016

We present quartz single-grain dose distributions for four well-bleached and unmixed sediment samples with independent age control (22-48 ka), from the archaeologically important Bordes-Fitte rockshelter at Roches d'Abilly, France. This site has previously been dated using 14C AMS dating and standard multi-grain OSL dating using both quartz and feldspar. The effect of rejection criteria usually employed in single-grain dating on dose and over-dispersion is tested using both laboratory irradiated samples and natural samples. It is shown that had these samples been analysed in the absence of other age control, standard modelling decisions based on the shape of single-grain dose distributions would have led to significant misinterpretation of results and a corresponding >40% underestimation in age. If we instead ignore this standard decision process and apply weighted average and mixing models then the most likely results deviate from the expected ages by >10%. Finally, we show that by careful consideration of the luminescence characteristics of individual grains, we are able to obtain good agreement with the independent age control by applying alternative rejection criteria but this is at the cost of reducing the accepted grain population by more than an order of magnitude, with the corresponding inevitable decrease in precision. © 2015 Elsevier B.V.. Source

Aubry T.,Coa Parque | Barbosa A.F.,Coa Parque | Luis L.,Coa Parque | Santos A.T.,Coa Parque | Silvestre M.,Coa Parque
Quaternary International | Year: 2015

Differing from most of European Upper Palaeolithic record, the Côa Valley lithic assemblages reveal an intensive use of a large variety of quartz and quartzite available locally. New surveys of the lower Côa Valley quartz veins were carried out in order to establish potential areas of raw material exploitation by hunter-gatherers through the identification of the raw material sources present in the archaeological record. Upper Palaeolithic lithic assemblages are produced on local quartz varieties, regional fine-grained quartz veins and flint and silcrete from long distance sources. The proportion of raw material and their choice for different tool types reveal some variation through the Upper Palaeolithic sequence, but present the same diversity and large geographical range of supply. Middle Palaeolithic assemblages from the same region are essentially based on local lithic material, showing a more restricted exploitation area and revealing different technology and procurement strategies, possibly evidence of changes in mobility and social networks. © 2015 Elsevier Ltd and INQUA. Source

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