The paleoanthropological site of Atapuerca Gran Dolina (N Spain): a perfect playground for ESR dating

Abstract

Atapuerca Gran Dolina (N Spain) is an iconic paleoanthropological locality hosting the oldest human species identified so far in Western Europe, Homo antecessor, dated to ~0.8-0.9 Ma. This cave site is made of a 25-m-thick sedimentary infill comprising 12 lithostratigraphic units, in which several archeo-paleontological levels have been identified, documenting human occupations from ~0.9 to ~0.3 Ma. Since systematic archeological excavations started at the site in the early 1980s, one of the main challenges has been to provide reliable chronological constraints to the sedimentary infill and associated fossil material. While the most standardized and accurate numerical dating methods typically employed in Quaternary Geochronology (e.g., Ar-Ar, C-14 or U-series) can simply not be used here given the geological context or the chronology of the site, other methods, perhaps less popular within the scientific community, have to be employed instead for this purpose. In this context, Electron Spin Resonance (ESR) dating appears to have one of the greatest potential, as it can not only be applied to a wide range of materials (e.g. phosphates, silicates or carbonates), but can also potentially cover the last 2 Ma. The most recent ESR dating attempts at Gran Dolina include: (i) the first direct dating of a human tooth belonging to Homo antecessor, following the same minimally-destructive procedure employed for H. naledi or for the H. sapiens from Misliya cave; (ii) Multiple Centre ESR dating of optically bleached quartz grains extracted from the >1 Ma old lowermost stratigraphic units, based on the systematic measurement of both Al and Ti ESR signals; (iii) ESR dose evaluation of geological apatite samples collected from various units and resulting from post-depositional processes; (iv) ESR dosimetry of carbonates from Early Pleistocene speleothems, which were found earlier to be unsuitable for U-Pb dating. By presenting the context, potential and limitations of these diverse dating applications carried out at Atapuerca Gran Dolina, this communication aims at providing an overview of some of the recent methodological advances in ESR dating. The accuracy of the dating results is assessed by cross-comparison with the existing independent age control based on magnetostratigraphy and luminescence dating.