New evidence of adhesive as hafting material on Middle and Upper Palaeolithic artefacts from Gura Cheii-Râşnov Cave (Romania)

Making use of analytical, chemical and mineralogical methods, this paper focuses on the analysis of inclusions in order to address the question of the provenance of prehistoric artefacts excavated in Gura Cheii-Râşnov Cave (Romania). The study represents the first discovery of bitumen on lithic tools belonging to the Upper and Middle Palaeolithic in Europe. The material was identified through several analytical procedures, such as Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray fluorescence (EDXRF), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and X-ray diffraction (XRD). Gas chromatography-mass spectrometry (GC–MS) allows the analysis of bitumen and related compounds: resins and oils, tar and pitch, and waxes. Lipids extracted from the lithic artefacts showed that the main organic constituents were palmitic (C16:0) and stearic (C18:0) acids, together with minor saturated (myristic C14:0, pentadecanoic C15:0, palmitic C16:0, iso-C16:0 C17:0) and unsaturated (palmitoleic C16:1 and oleic C18:1) fatty acids. The use of GC–MS also allows identifying C15+ alkanes (such as C23H48 – tricosane, C24H50 – tetracosane, C25H52 – pentacosane). All these hydrocarbons confirm that the black substance is highly weathered bitumen, the source of which remains unknown. The composition of this black substance suggests that the organic traces are remnants of a hafting material used by Palaeolithic people to glue handles onto their tools