The recently discovered open-air site of Les Bossates (Ormesson, northern France) has a rich archaeological sequence, including a late Mousterian assemblage which has been TL dated to around 47,000 years ago. As reported elsewhere, this assemblage is characterised by discoidal flaking and a large number (77) of red and yellow iron oxide-rich rocks. These fragments show traces of powder production through the presence of abrasion, striation and scraping marks. A new study, published in Nuclear Instruments and Methods in Physics Research B, now investigates the geological source of these elements.
These elements are commonly described as ‘ochre’ although the more correct term is iron oxide-rich or ferruginous rocks. Several geological sources in the area containing these ferruginous rocks were sampled and assessed through PIXE analyses of the major and trace elements. These methods allowed comparing the geochemical fingerprint of 11 archaeological and 18 geological samples.
A chemical match was found between the archaeological samples and the ferruginous concretions from the Sparnacian deposits, which are situated around 5km from the site, on the other bank of the Loing river. Conversely, the Stampian concretions, which are present at the site itself and in its immediate surroundings, were not selected. The Sparnacian deposits seemed to have been favoured, potentially because of their higher iron oxide content, fewer quartz and harder haematite. The authors argue therefore that the collection of this raw material was not opportunistic and the preferred concretions nearly exclusively made of iron oxides (haematite) and hydroxides (goethite).
The question of why and how these ferruginous rocks were used is not tackled in this paper, but will hopefully form part of further studies of this exciting site, which is currently still being excavated as well. So stay tuned!
Full reference: F. Mathis et al. 2014. PIXE identification of the provenance of ferruginous rocks used by Neanderthals, Nucl. Instr. Meth. B, http://dx.doi.org/10.1016/j.nimb.2013.11.028