PIXE identification of the provenance of ferruginous rocks used by Neanderthals

Les Bossats, near Ormesson, France, is a newly discovered late Mousterian open air site dated to around 47,000 years ago by thermoluminescence. The archaeological level, fossilized by loess, revealed a rich industry based on the discoid mode, associated with numerous fragments of red and yellow iron oxide-rich rocks showing clear traces of powder production (abrasion, striation, scraping), which are exceptional remains for this remote period. Archeological material and geological samples from the close environment were studied by PIXE and by petrographical observations made on thin sections. The geological sources were identified by means of PIXE analyses on two IBA facilities: AGLAE (2 MV tandem) at the C2RMF in Paris and the cyclotron of the IPNAS (University of Liège). We paid particular attention to the comparison of results obtained on both installations by using the same set of geological standards and by a fine evaluation of the limit of detection relative to each trace elements of interest for both experimental set ups. The elemental fingerprint of one geological source of iron-rich concretions corresponds clearly with the archaeological collection. At least, this investigation demonstrates that the colouring materials were minutely selected in the close neighbouring of the site by the Neanderthals.