Charcoal-painted images from the French Neolithic Villevenard hypogea: an experimental protocol for radiocarbon dating of conserved and in situ carbon with consolidant contamination

A conserved painting removed from a Neolithic collective grave in Marne, France, provided an opportunity for radiocarbon dating to place Les Ronces Hypogeum 21 (Villevenard) into the chronology of that region. Chemical analysis with direct analysis in real time (DART) mass spectrometry, Fourier transform infrared (FTIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) of samples from the painting revealed the presence of two kinds of wax (beeswax and paraffin or microcrystalline wax) that likely were added during the conservation, a drying oil like linseed oil, as well as markers of pine resin that may arise from turpentine or colophony. A new pretreatment protocol of chloroform followed by pH 8 phosphate buffer was developed, which yielded sufficient material for plasma-chemical oxidation and AMS radiocarbon dating. The radiocarbon dates place the image from Hypogeum 21 at the more recent end of the chronology that spans from the sixth to the third millennia cal BC for the Neolithic in France.