New U–Pb zircon ages from rhyolite samples of the Fishguard Volcanic Group, SW Wales, confirm a Middle Ordovician (Darriwilian) age for the group. One of the samples is from Craig Rhos-y-felin, which has recently been identified on petrological and geochemical grounds as the source of much of the debitage (struck flakes) at Stonehenge. Analysis of a Stonehenge rhyolite fragment yields an age comparable with that of the Craig Rhos-y-felin sample. Another Stonehenge fragment, thought to come from orthostat (standing stone) 48 and on petrographical grounds to be derived from the Fishguard Volcanic Group (but not Craig Rhos-y-felin), yields an age also consistent with a Fishguard Volcanic Group source.

Supplementary material: Details of analytical methods and a table of data are available at https://doi.org/10.6084/m9.figshare.c.3518175.

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