Christophe Falguères

Early Evidence of Acheulean Settlement in Northwestern Europe - La Noira Site, a 700 000 Year-Old Occupation in the Center of France

The human settlement of Europe during Pleistocene times was sporadic and several stages have been recognized, both from paleaoanthropological and archaeological records. If the first phase of hominin occupation (as early as 1.4 Ma) seems mainly restricted to the southern part of the continent, the second phase, characterized by specific lithic tools (handaxes), is linked to Acheulean settlements and to the emergence of Homo heidelbergensis, the ancestor of Neanderthals. This phase reached northwestern Europe and is documented in numerous sites in Germany, Great Britain and northern France, generally after 600 ka. At la Noira (Brinay, Central France), the Middle Pleistocene alluvial formation of the Cher River covers an archaeological level associated with a slope deposit (diamicton). The lithic assemblage from this level includes Large Cutting Tools (LCTs), flakes and cores, associated with numerous millstone slabs. The lithic series is classified as Acheulean on the basis of both technological and typological analyses. Cryoturbation features indicate that the slope deposits and associated archaeological level were strongly frozen and disturbed after hominin occupation and before fluvial deposition. Eight sediment samples were dated by the electron spin resonance (ESR) method and the weighted average age obtained for the fluvial sands overlying the slope deposits is 665±55 ka. This age is older than previous chronological data placing the first European Acheulean assemblages north of 45th parallel north at around 500 ka and modifies our current vision of the initial peopling of northern Europe. Acheulean settlements are older than previously assumed and the oldest evidences are not only located in southern Europe. La Noira is the oldest evidence of Acheulean presence in north-western Europe and attests to the possibility of pioneering phases of Acheulean settlement which would have taken place on a Mode 1-type substratum as early as 700 ka. The lithic assemblage from la Noira thus provides behavioral and technological data on early Acheulean occupation in Europe and contributes to our understanding of the diffusion of this tradition.

Middle Pleistocene raised beach anomalies in the English Channel: regional and global stratigraphic implications

Abstract Palaeo-shore positions help to evidence long-term eustatic changes and assist in the understanding of tectonic movements at a regional scale. Raised beaches anomalies exist in the Channel region and may result from deformations induced by neotectonic or by glacio-isostasy. The aim of this paper is to re-analyse, within their geodynamic context in the Channel and Dover Strait regions, the stratigraphy and the datings of palaeo-shores of Middle and Upper Pleistocene ages. This sector of Europe is characterised by strong geological contrasts and is controlled by two main geological boundaries: in the north, the Variscan Overthrust (corresponding approximately to the position of the Dover Strait) and, in the south, the Northern Branch of the Southern Brittany shearing zone. These two boundaries border a domain which seems to behave rather homogeneously on a large scale under the control of plate tectonics. Today, shorelines are subsiding north and south of this ‘Channel’ region. Episodic uplift largely controlled the open or closed status of the Dover Strait, especially after the Messinian and Early Quaternary, by reactivating Variscan structures. After 400 ka, global cooling allowed supplementary deformations in the area to be induced by glacio-isostatic rebound and clustered seismic activity during the phase of ice sheet building. Evidence of eight different transgressions dated by ESR from Oxygen Isotopic Stage (OIS) 13 to the end of OIS 5 shows the complexity of the sea-level records in a region unstable for isostatic and neotectonic reasons. Due to glacio-isostatic depression, transgressions are possible in late glacial times as well as during full interglacials. Most platforms were initially cut, during the Late Miocene, and seem to have been re-trimmed several times, especially by shore ice rafting since OIS 9. Regionally, the sea apparently rose to about the same level in O.I. Stages 11, 9 and 7. Glacio-isostatic and glacio-eustatic relative displacements of the sea level together with background tectonic movements have modified coastal positions and have temporarily altered the intensity of tidal currents. The oldest shoreline deposits are preserved only in subsiding areas, controlled by the deep crustal pattern. Neotectonics related to Variscan structure reactivation still dominates glacio-isostatic deformation and basin subsidence. The OIS 7 positive anomaly seems related to a regional relaxation event.

Evaluation de l'incertitude de mesure de la dose annuelle en datation par luminescence (TL, OSL) et par RPE : Une expérience d'intercomparaison à la Grotte XVI, Cénac et Saint-Julien, Dordogne

Dans le but devaluer la representativite des incertitudes sur la determination des differents parametres en datation par thermoluminescence (TL), luminescence stimulee optiquement (OSL) et par resonance paramagnetique electronique (RPE), une operation de comparaison interlaboratoire de mesure de radioactivite naturelle a ete engagee sur le site paleolithique de la Grotte XVI, en Dordogne. Elle a porte, dune part, sur la mesure par dosimetrie TL in situ du debit de dose annuelle y et cosmique et, dautre part, sur la determination au laboratoire des concentrations en K, U et Th dechantillons de calcaire et de sediments silicates. Dans ce dernier cas, la diversite de composition radiochimique des materiaux analyses a permis de tester les methodes de mesure mises en oeuvre (spectrometrie y a bas bruit de fond, spectrometrie demission atomique de plasma, emission de flamme et comptage a) sur une gamme de teneurs comprises entre 0,1 et 1,6 % pour le potassium, entre 0,2 et 4 ppm pour luranium et entre 0,8 et 18 ppm pour le thorium. Les resultats de la dosimetrie TL in situ des differents laboratoires participants sont en excellent recouvrement ; ils montrent quune incertitude instrumentale inferieure a ±5% est couramment accessible par cette voie. Les resultats des analyses en laboratoire sont egalement en bon accord. On a pu montrer ici ladequation de la spectrometrie y a bas bruit de fond a la mesure de la radioactivite naturelle dans le cadre de la datation par luminescence et par RPE, en raison de sa grande precision. La determination de la dose annuelle dirradiation peut etre obtenue avec une incertitude instrumentale inferieure a ±3% en valeur relative.