Geoarcheological study of the early Acheulian site at "Lanoira"
Résumé
In the middle Cher river valley (Centre-Val de Loire Region, France) fieldworks and researches allowed a geological, geochronological and paleoenvironnemental framework for the fluvial system and associated prehistoric sites. At Brinay ( Cher department), the sandy alluvia of the Les Fougeres Formation that overlap the Acheulian Site of la Noira was dated par ESR Method of 665 perpendicular to 55 ka. On this site, archaeological studies and excavations shown that hominins had prospected amounts of various weathered raw materials downsloping from the interfluve (Sub-Unit a1 / Unit a). Their strategy of supply seems to have consisted in several series of selections for gathering millstone slabs, while eliminating those which were previously alterated or frozen. These slabs were broken and the fragments were used for knapping flakes or shaping handaxes. During excavations, because of their freshness, evidence of primary position of these artifacts was observed. So, hominins were partially presents near by the river owing to reach raw materials. These in demand millstones are lacustrine silicifications that were uncovered during incision phase of the Cher river then sloped down in debris flows. These phenomena were resulting from climatic cyclicity and correspond to a transition phase at the beginning of a glacial stage and before pleniglacial stage (MIS 16) while the uncovered areas of Unit a and substratum were cryoturbated. In some valleys of the Middle Loire river Basin, others prehistoric assemblages were founded on the top of incision floors uncovered during different climatic cycles of the Early or Middle Pleistocene. Hominins activities on the alluvial plain food during the transition phase at the beginning of a glacial phase would be recurred cycle after cycle, but would be intermittent.