LASER ARGON DATING AND GEOLOGICAL PROVENANCING OF A STONE AXE FROM THE STONEHENGE ENVIRONS*

The recently-developed laser microprobe ⁴⁰argon-³⁹ argon technique has been used to give a geological date for a rhyolitic tuff stone axe fragment from the Stonehenge environs. The method requires only milligramme-sized samples and gives dates of sufficient accuracy to aid in provenancing artefacts to sources, as well as information on the heating history of samples. The axe sample is of Lower Carboniferous date (341 ± 5 Ma) and this limits possible sources to outcrops within the Scottish Midland Valley and small altered exposures in Dartmoor. X-ray fluorescence analysis of the axe suggests the Scottish Midland Valley as the more likely source. The laser argon analysis also shows that the implement had not been heated in antiquity. Laser argon-argon dating can, therefore, be a useful tool in artefact study.