The middle pleistocene site of la Noira at Brinay (Cher): morphosedimentary context, geochronology, archaeological datas
Le site pléistocène moyen de la Noira à Brinay (Cher, région Centre, France) : contexte morphosédimentaire, géochronologie et données archéologiques
Résumé
Upstream of Vierzon city, the fossil fluvial system of the Cher River is composed of seven sandy alluvial formations, which include four stepped sheets deposited on the western slope of the valley and three formations stacked in the fault trough where the river is currently flowing. According to the available geochronological data (ESR on optically bleached quartz), these formations were deposited between 1 Ma and 60 ka. The Acheulian site of la Noira (Brinay, Cher) is located on the western slope, at the bottom of one of the terraces, "Les Fougeres Formation". At la Noira, the lowest Unit a, close to the valley side, is covered by the alluvial les Fougeres Formation and could correspond to the beginning of a glacial stage. Hominins collected there lacustrine millstone slabs embedded in soliflucted coarse deposits lying on the substrate (Unit a). The slab fragments they broke were shaped into handaxes or knapped to produce large flakes. Subsequently, Unit a and the associated workshops were overlain by colluvium, then partly cryoturbated before being overlapped by the thick fluvial sands of the les Fougeres Formation. This 6 m-thick formation at la Noira, is composed by a succession of three sand units (Units b, c, d) with unconformities covered by slope deposits or underlined by cryoturbation features and ice wedge pseudomorphs. According to ESR dates (mean weighted age: 665 +/- 55 ka), deposition took place during the beginning of MIS 16.