New luminescence ages for the Galería Complex archaeological site: resolving chronological uncertainties on the acheulean record of the Sierra de Atapuerca, northern Spain.

Martina Demuro,Josep M Parés,Alfredo Pérez-González,Juan L Arsuaga,José M Bermúdez De Castro,Eudald Carbonell,Ana I Ortega,Lee J Arnold,Michael D Petraglia

doi:10.1371/journal.pone.0110169

Abstract

The archaeological karstic infill site of Galería Complex, located within the Atapuerca system (Spain), has produced a large faunal and archaeological record (Homo sp. aff. heidelbergensis fossils and Mode II lithic artefacts) belonging to the Middle Pleistocene. Extended-range luminescence dating techniques, namely post-infrared infrared stimulated luminescence (pIR-IR) dating of K-feldspars and thermally transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains, were applied to fossil-bearing sediments at Galería. The luminescence dating results are in good agreement with published chronologies derived using alternative radiometric dating methods (i.e., ESR and U-series dating of bracketing speleothems and combined ESR/U-series dating of herbivore teeth), as well as biochronology and palaeoenvironmental reconstructions inferred from proxy records (e.g., pollen data). For the majority of samples dated, however, the new luminescence ages are significantly (∼50%) younger than previously published polymineral thermoluminescence (TL) chronologies, suggesting that the latter may have overestimated the true burial age of the Galería deposits. The luminescence ages obtained indicate that the top of the basal sterile sands (GIb) at Galería have an age of up to ∼370 thousand years (ka), while the lowermost sub-unit containing Mode II Acheulean lithics (base of unit GIIa) was deposited during MIS 9 (mean age = 313±14 ka; n = 4). The overlying units GIIb-GIV, which contain the richest archaeopalaeontological remains, were deposited during late MIS 8 or early MIS 7 (∼240 ka). Galería Complex may be correlative with other Middle Pleistocene sites from Atapuerca, such as Gran Dolina level TD10 and unit TE19 from Sima del Elefante, but the lowermost archaeological horizons are ∼100 ka younger than the hominin-bearing clay breccias at the Sima de los Huesos site. Our results suggest that both pIR-IR and single-grain TT-OSL dating are suitable for resolving Middle Pleistocene chronologies for the Sierra de Atapuerca karstic infill sequences.

Highlights

The Sierra de Atapuerca archaeological complex, located in northern Spain, has been systematically excavated for the last 30 years and has provided a wealth of information for the Early to Middle Pleistocene palaeoanthropological record of Europe
Examination of the large collection of Mode II lithics and abundant Acheulean large cutting tools, together with use-wear analysis and taphonomic investigations of preserved faunal remains, indicate that Galerıa was visited by humans for the exploitation of carcasses of large herbivores that had fallen down the vertical shaft at the southern end of the cavity [9,10]
thermally transferred optically stimulated luminescence (TT-OSL) and post-infrared IRSL (pIR-IR) signal characteristics Representative TT-OSL decay curves and sensitivity-corrected dose-response curves are shown in Figure 4a-d for two accepted grains from unit GIIIa

Summary

Introduction

The Sierra de Atapuerca archaeological complex, located in northern Spain, has been systematically excavated for the last 30 years and has provided a wealth of information for the Early to Middle Pleistocene palaeoanthropological record of Europe. Key among the Atapuerca palaeoanthropological sites is the mid-late Middle Pleistocene site of Galerıa Complex, which represents one of the karstic infill exposures found along the abandoned railway trench and is located 50 m to the south of Gran Dolina and 100 m to the north of Sima del Elefante (Figure 1). This site contains various archaeo-palaeontological levels that have produced ,12,000 large mammal remains, thousands of small vertebrates, ,1800 lithic tools and two human skeletal fragments tentatively assigned to Homo sp. Examination of the large collection of Mode II lithics and abundant Acheulean large cutting tools (handaxes, cleavers), together with use-wear analysis and taphonomic investigations of preserved faunal remains, indicate that Galerıa was visited by humans for the exploitation of carcasses of large herbivores that had fallen down the vertical shaft at the southern end of the cavity [9,10]

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