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A team of researchers at the University of Brighton in England used a combination of geochemical and statistical approaches to determine where Stonehenge’s sarsen (silcrete) megalith stones came from. Using portable X-ray fluorescence (PXRF) spectrometry to provide a non-invasive initial chemical characterization of all 52 existing sarsen uprights and lintel stones, the team was able to determine the degree of chemical variability present across the monument (1).
The resulting data were analyzed statistically to determine the degree of chemical variability present across the monument. Inductively coupled plasma–mass spectrometry (ICP-MS) and ICP–atomic emission spectrometry (ICP-AES) were used for the analyses of samples from a recently rediscovered core drilled through sarsen Stone 58 at Stonehenge and a representative range of sarsen boulders from across southern Britain. These analyses were used to generate high-resolution chemical signatures for the monument and potential source regions. Comparisons of these signatures allowed the team to identify the most likely source area for the sarsens at Stonehenge.
English Heritage, the charity that cares for Stonehenge, gave the researchers permission to sample a 67-mm long section of the Phillip’s Core, a core fragment from Stone 58 that was previously assumed “lost.” The drill core was returned to the United Kingdom from the United States by Robert Phillips, who was on-site during the drilling operations of a Stonehenge restoration project that took place in 1958.
To assess the chemical variability within British sarsens, the researchers sampled boulders (with landowner permission) in 20 representative areas of sarsen concentration. Stones at each site were selected at random, and three ~100-g samples of sarsen were collected using a geological hammer and chisel. Each of these samples was analyzed by ICP-MS and ICP-AES using the same analytical protocol applied to the Phillips’ Core samples from Stonehenge. To determine the most likely source area for Stone 58 (and most of the Stonehenge sarsens), the team compared the median immobile trace element signature for the Phillips’ Core with the 20 site-specific geochemical signatures.
Based on the data collected by the team, Stone 58 and the majority of the sarsens used to construct Stonehenge were most likely sourced from the vicinity of West Woods, south of Marlborough, in England.
D.J. Nash, T. J.R. Ciborowski, J.S. Ullyott, M.P Pearson, T. Darvill, S. Greaney, G. Maniatis, and K.A. Whitaker, Sci. Adv. 6 (2020).