OSL dating of the Middle Palaeolithic Hotel California site, Sierra de Atapuerca, north-central Spain

In this study we present optically stimulated luminescence (OSL) dating results obtained at one of the most important open‐air Middle Palaeolithic sites in the Sierra de Atapuerca foothills – Hotel California. We also assess the possibility of obtaining extended‐range OSL chronologies for a nearby M...

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Bibliographic Details
Published inBoreas Vol. 42; no. 2; pp. 285 - 305
Main Authors Arnold, Lee J., Demuro, Martina, Navazo, Marta, Benito-Calvo, Alfonso, Pérez-González, Alfredo
Format Journal Article
LanguageEnglish
Published Aarhus Blackwell Publishing Ltd 01.04.2013
John Wiley & Sons, Inc
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Summary:In this study we present optically stimulated luminescence (OSL) dating results obtained at one of the most important open‐air Middle Palaeolithic sites in the Sierra de Atapuerca foothills – Hotel California. We also assess the possibility of obtaining extended‐range OSL chronologies for a nearby Middle Pleistocene fluvial deposit using several novel methods, namely OSL dating of individual quartz ‘supergrains’, multi‐grain aliquot thermally transferred OSL (TT‐OSL) dating and the first application of a single‐grain TT‐OSL dating procedure. Four single‐grain OSL ages constrain the Middle Palaeolithic occupation of Hotel California to between 71±6 and 48±3 ka. The Hotel California single‐grain equivalent dose (De) distributions are highly overdispersed and contain several dose populations, which are probably attributable to post‐depositional sediment mixing, partial bleaching and intrinsic scatter. The reliability of multi‐grain aliquot OSL dating is compromised by the complex underlying De dispersion affecting these samples, as well as by biasing multi‐grain averaging effects. Extended‐range OSL and TT‐OSL chronologies for the nearby Pico River terrace are consistent with each other and with broad independent age control. These experimental approaches yield a weighted average age of 348±16 ka for terrace TA9 of the Arlanzón River sequence. Our results highlight the benefits of comparing ages obtained using several OSL methodologies to improve the robustness of luminescence chronologies. They also demonstrate the potential that single‐grain OSL techniques offer for establishing improved age constraints on the many other Middle Palaeolithic sites found at Atapuerca and elsewhere across north‐central Spain.
Bibliography:Ministerio de Ciencia e Innovación de España - No. CGL2010-16821
ark:/67375/WNG-Z0WXG37S-3
Marie Curie International Reintegration - No. PIRG08-GA-2010-276810
istex:9C824F497B38A06F88A64DF696C9B0758D7AEAB3
ArticleID:BOR262
Fig. S1. OSL dose-recovery test results for sample HC10-1. A. Recovered-to-given dose ratios vs. PH1 temperature (held for 10 s) for ∼80-grain aliquots. The natural OSL signals of the multi-grain aliquots were optically bleached with two 1000-s blue LED illuminations at ambient temperature, separated by a 10 000-s pause. A known dose of 102 Gy was then administered to each aliquot and the SAR procedure shown in Table S1A was subsequently used to estimate this dose. A fixed PH2 of 160°C for 10 s was applied in the dose-recovery SAR procedure. B. Radial plot showing the recovered-to-given dose ratios obtained for individual quartz grains using a PH1 of 200°C for 10 s and a PH2 of 160°C for 10 s. The single-grain natural OSL signals were bleached using the same procedure as outlined above, and the administered doses were subsequently recovered using the single-grain SAR procedure shown in Table S1B. The grey shaded region on the radial plot is centred on the administered dose for each grain (sample average=96 Gy, although this amount varied from 74 to 107 Gy for individual grains, owing to spatial variations in the dose rate of the beta source). Individual De values that fall within the shaded region are consistent with the administered dose at 2σ.Fig. S2. Representative OSL and TT-OSL decay and dose-response curves for individual quartz grains and multi-grain aliquots of the Hotel California and Pico terrace samples. A. Quartz grain from sample HC10-3 with average OSL signal (Tn=∼200 counts/0.17 s). B. Quartz grain from sample HC10-1 with a relatively bright OSL signal (Tn signal=∼1400 counts/0.17 s). C. OSL decay and dose-response curve for an ∼80-grain aliquot from sample HC10-1. D. Quartz grain from sample PT10-1 with high dose saturation properties. E. ∼80-grain aliquot TT-OSL decay and dose-response curve from PT10-1. F. Single-grain TT-OSL decay and dose-response curve from PT10-1. OSL and TT-OSL decay curves are shown for the natural dose (Ln), the natural test dose (Tn), the 0-Gy regenerative dose (Lx=0 Gy), and a high regenerative-dose point (Lx). The Tn signals shown in parts (E) and (F) were obtained from OSL rather than from TT-OSL stimulations and have been multiplied by a factor of 0.1 so that they can be displayed on the same scale as the TT-OSL results. In the inset plots, the open circles on the y-axis denote the sensitivity-corrected natural OSL or TT-OSL signals, and the sensitivity-corrected regenerated OSL or TT-OSL signals are shown as filled circles.Fig. S3. A. Cumulative light-sum plots and B. absolute OSL signal intensities for single-grain measurements of the Hotel California and Pico terrace samples. Net OSL signals are shown for the 15-Gy natural test dose in the SAR De estimation procedure (Table S1B) and have been ranked from brightest to dimmest to create these plots. Luminescent grains displaying OSL IR depletion ratios (Duller 2003) of less than unity at 2σ were excluded from this analysis to ensure that feldspar contaminants did not adversely influence the cumulative light-sum results.Fig. S4. Radial plots showing multi-grain De data sets obtained for the Hotel California samples. A. HC10-1. B. HC10-4. C. HC10-2. D. HC10-3. The grey shaded region is centred on the weighted mean burial dose, calculated using the CAM.Table S1. Single-aliquot regenerative-dose (SAR) procedures used for De determination in this study. Each of the SAR measurement cycles was repeated for the natural dose, 4-5 different-sized regenerative doses and a 0-Gy regenerative dose (to measure OSL signal recuperation). Both the smallest and largest non-zero regenerative-dose cycles were repeated at the end of the SAR procedure to assess the suitability of the test-dose sensitivity correction. In the case of the single-grain OSL SAR procedure, the smallest regenerative-dose cycle was also repeated a second time with the inclusion of step 5 to check for the presence of feldspar contaminants using the OSL IR depletion ratio of Duller (2003).Table S2. The number and proportion of measured grains that were rejected from the final De estimation after applying the various SAR OSL and TT-OSL quality-assurance criteria outlined in the main text. Tn=natural test-dose signal response; Ln/Tn=sensitivity-corrected natural signal response; Lx/Tx=sensitivity-corrected regenerative-dose signal response.
ISSN:0300-9483
1502-3885
DOI:10.1111/j.1502-3885.2012.00262.x