Linking derived debitage to the Stonehenge Altar Stone using portable X-ray fluorescence analysis

Richard Bevins, Nick Pearce, Rob Ixer, Stephen Hillier, Duncan Pirrie, Peter Turner

Allbwn ymchwil: Cyfraniad at gyfnodolynErthygladolygiad gan gymheiriaid

49 Wedi eu Llwytho i Lawr (Pure)


The Altar Stone at Stonehenge is enigmatic in that it differs markedly from the other bluestones. It is a grey-green, micaceous sandstone and has been considered to be derived from the Old Red Sandstone sequences of south Wales. Previous studies, however, have been based on presumed derived fragments (debitage) that have been visually identified as coming from the Altar Stone. Portable XRF analyses were conducted on these fragments (ex situ) as well as on the Altar Stone (in situ). Light elements (Z<37) in the Altar Stone analyses, performed after a night of heavy rain, were affected by surface and pore water that attenuate low energy X-rays, but the dry analyses of debitage fragments produced data for a full suite of elements. High Z elements, including Zr, Nb, Sr, Pb, Th, and U, all occupy the same compositional space in the Altar Stone and debitage fragments, and are statistically indistinguishable, indicating the fragments are derived from the Altar Stone. Barium compares very closely between the debitage and Altar Stone, with differences related to variable baryte distribution in the Altar Stone, limited accessibility of its surface for analysis, and probably to surface weathering. A notable feature of the Altar Stone sandstone is the presence of baryte (up to 0.8 modal%), manifest as relatively high Ba in both the debitage and the Altar Stone. These high Ba contents are in marked contrast with those in a small set of Old Red Sandstone field samples, analysed alongside the Altar Stone and debitage fragments, raising the possibility that the Altar Stone may not have been sourced from the Old Red Sandstone sequences of Wales. This high Ba ‘fingerprint’, related to the presence of baryte, may provide a rapid test using pXRF in the search for the source of the Stonehenge Altar Stone.
Iaith wreiddiolSaesneg
Rhif yr erthygl22
Tudalennau (o-i)688-700
Nifer y tudalennau13
CyfnodolynMineralogical Magazine
Rhif cyhoeddi4
Dyddiad ar-lein cynnar22 Maw 2022
Dynodwyr Gwrthrych Digidol (DOIs)
StatwsE-gyhoeddi cyn argraffu - 22 Maw 2022

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