Stonehenge’s Sarsen Stones: Unraveling a Geochemical Mystery

The origins of Stonehenge’s massive sarsen stones, giant silcrete blocks forming its outer circle and central trilithons, have been debated for centuries. Recent advances in geochemical analysis have provided new insights into their provenance, but they have also sparked a scientific controversy. This article explores the debate between key studies—Nash et al. (2020), Ciborowski et al (2024), Hancock et al. (2024), and Nash and Ciborowski (2025)—and incorporates new evidence from Harding et al. (2025) on the Cuckoo and Tor Stones, offering a comprehensive analysis of the methods, findings, and implications for Stonehenge’s construction.

A fuller version of this post - is at 10.13140/RG.2.2.28682.17606  https://www.researchgate.net/publication/392093378_The_Origins_of_Stonehenge's_Sarsen_Stones_A_Comprehensive_Review_of_Provenancing_Studies

The Quest for Provenance

Since the 16th century, scholars have speculated that the sarsens, weighing up to 25 tons, originated from the Marlborough Downs, approximately 25 km north of Stonehenge. Early analyses relied on visual inspection, but modern geochemical techniques, such as X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS), enable precise “fingerprinting” of stones by their chemical composition, allowing researchers to match them to specific source areas.

The 2020 Study by Nash et al.: Pinpointing West Woods

In 2020, a landmark study by Nash et al., published in Science Advances (Origins of the sarsen megaliths), provided a significant breakthrough. The study was expanded in Nash et al. (2021) Petrological and geochemical characterisation of the sarsen stones at Stonehenge .The researchers analyzed a core from Stone 58, part of the central trilithon horseshoe, extracted during 1958 conservation work and repatriated in 2018.

Methods

Nash et al. used ICP-MS to analyze 21 immobile trace elements, such as zirconium (Zr), which are resistant to weathering and provide a reliable geochemical signature. They employed portable XRF (pXRF) to analyze the surface chemistry of 52 sarsen stones at Stonehenge, finding that 50 shared a consistent profile. To account for variable silica content in sarsens, which can dilute other elements, they used Zr-normalized ratios, a standard geochemical practice. These results were compared with samples from 20 potential source areas across southern England, including the Marlborough Downs, Kent, Dorset, and Oxfordshire.

Findings

The study concluded that 50 of the 52 sarsens at Stonehenge matched the geochemical signature of West Woods, a forested area on the Marlborough Downs, approximately 25 km north of Stonehenge. Only two stones (Stones 26 and 160) showed a different chemical profile, suggesting a possible distinct origin. 

Significance

This study was hailed as a major advance, resolving a centuries-old debate by identifying West Woods as the primary source for Stonehenge’s sarsen megaliths. It suggested a focused procurement strategy and aligned with the geological context of the Marlborough Downs, known for its extensive sarsen boulder scatters.

The 2024 Study by Ciborowski et al.: A More Complex Picture

In 2024, Ciborowski et al. published a study in Journal of Archaeological Science: Reports (Local and exotic sources), expanding the single-source narrative. Unlike Nash et al., who focused on large megaliths, Ciborowski et al. examined sarsen debitage—smaller fragments likely resulting from stone dressing or other activities.

Methods

The researchers analyzed 1,028 sarsen fragments using pXRF, a non-destructive technique measuring surface chemistry. Recognizing weathering effects, they selected 54 representative fragments for further analysis using ICP-MS and inductively coupled plasma atomic emission spectroscopy (ICP-AES), focusing on absolute element concentrations rather than normalized ratios. These results were compared with known sarsen outcrops.

Findings

Ciborowski et al. found that while some debitage matched the West Woods signature, many fragments did not. Specifically:

• 22 of the 54 fragments fell into three distinct geochemical “families” not aligning with Stone 58 or its 49 chemical equivalents.
• Specific sources were identified for 15 fragments:
  • 11 from the Marlborough Downs (Monkton Down, Totterdown Wood, and West Woods, 25–33 km north).
  • 3 from Bramdean, Hampshire (51 km southeast).
  • 1 from Stoney Wish, East Sussex (123 km southeast).
• A large flake from Monkton Down suggested a second source within the Marlborough Downs, possibly linked to on-site stone dressing.

Implications

Ciborowski et al. argued that their findings indicate a more complex procurement strategy. While West Woods was likely the primary source for large megaliths, other locations contributed smaller stones or fragments, possibly for tools, repairs, or ceremonial purposes. Distant sources like Bramdean and Stoney Wish suggested trade networks or symbolic choices, similar to the Welsh bluestones.

The Debate Heats Up: Hancock et al. and the 2025 Critique

In 2024, Hancock et al. reanalyzed the geochemical data from Nash et al. (2020) to challenge the single-source hypothesis(Stonehenge revisited), questioning the reliability of Zr-normalization due to Zr’s variable incorporation in sarsens. Using absolute elemental concentrations and inter-element relationships, they argued that multiple sites—primarily Clatford Bottom and Piggledene in Wiltshire, with West Woods as a less likely candidate—could be potential sources. They also speculated that Stone 58 might be a glacial erratic transported by an ice flow from as far as Scandinavia.

The 2025 Critique by Nash and Ciborowski: Defending Methodological Rigor and the Original Findings

In 2025, Nash and Ciborowski responded in Archaeometry (Comment on Stonehenge revisited), critiquing Hancock et al.’s methodology, arguing that Hancock et al.’s reliance on absolute concentrations, including mobile elements like Si and Fe, and single-sample comparisons, overlooked sarsen variability and weathering effects. They reaffirmed West Woods as the primary source, emphasizing the robustness of Zr-normalized immobile trace elements. Nash et al. used multi-sample ranges and statistical measures (e.g., ±3 standard deviations) to account for geochemical variability. Hancock et al.’s single-sample comparisons were deemed inadequate. Hancock et al.’s suggestion of glacial transport was dismissed, as it contradicts geological evidence of sarsen formation through groundwater silicification.

New Evidence from the Cuckoo Stone and Tor Stone

A 2025 study by Harding et al. in Proceedings of the Prehistoric Society (Earliest Movement) provides further insights into sarsen provenance. The researchers analyzed the Cuckoo Stone and Tor Stone, former standing stones on opposite banks of the River Avon near the Stonehenge and Avebury World Heritage Site.

Methods

Using pXRF, Harding et al. analyzed the geochemical composition of these stones, comparing them with Stonehenge sarsens and potential source areas. They integrated archaeological fieldwork and radiocarbon dating from nearby sites and conducted visibility analysis using GIS tools to assess their placement in the landscape.

Findings

The study found that both stones likely originated from West Woods, aligning with Nash et al.’s findings. Radiocarbon dating suggests they were erected around 3000–2900 cal BCE, 400–500 years before Stonehenge’s main sarsen structures (c. 2500 cal BCE). Visibility analysis indicated they were intervisible, possibly forming a “formal portal” to the Stonehenge area, linking them to sites like Woodhenge and Durrington Walls.

Implications

This study strengthens the case for West Woods as the primary source. The early dating suggests sarsen use began earlier than previously thought, reflecting planned landscape development and possibly cultural influences from regions like Orkney.

Discussion: Reconciling the Evidence

The controversy hinges on methodological differences in geochemical provenancing. Nash et al.’s use of Zr-normalized ratios of immobile trace elements accounts for sarsens’ variable silica content, making their conclusions robust for the main megaliths. Harding et al.’s findings further support West Woods as the source for significant stones like the Cuckoo and Tor Stones. Ciborowski et al.’s focus on debitage suggests complexity, as smaller fragments may represent different uses or phases, though their initial pXRF screening was affected by weathering, their whole-rock ICP-MS and ICP-AES analyses provided reliable results for the 54 fragments studied. Hancock et al.'s criticism are rigorously critiqued for methodological limitations, and while the points that there is not a single source for the sarsens and the identification of sources can be further improved are agreed, the original studies appear to have robust conclusions.

The following table summarizes the key studies:

Study	Focus	Methods	Key Findings
Nash et al. (2020)	Large sarsen megaliths (52 stones)	ICP-MS, pXRF, Zr-normalized ratios of immobile trace elements	50/52 stones from West Woods
Ciborowski et al. (2024)	Sarsen debitage (1,028 fragments)	pXRF, ICP-MS, ICP-AES, absolute element concentrations	Multiple sources, including Monkton Down, Bramdean, Stoney Wish
Nash and Ciborowski (2025)	Critique of Hancock et al.	Review of geochemical methods	Defends West Woods as primary source
Harding et al. (2025)	Cuckoo and Tor Stones	pXRF, archaeological dating, visibility analysis	West Woods source, early use (3000–2900 BCE)

Implications for Stonehenge’s Construction

The evidence strongly supports West Woods as the primary source for Stonehenge’s large sarsen megaliths and other significant stones, suggesting a focused sourcing effort. Transporting 25-ton stones over 25 km would have required significant organization. Ciborowski et al.’s findings on debitage suggest smaller fragments from other sources, possibly for tools. Harding et al.’s early dating of the Cuckoo and Tor Stones reveals a longer history of sarsen use, predating the main monument and suggesting a planned Neolithic landscape.

Conclusion

The debate over Stonehenge’s sarsen stones reflects the complexities of geochemical provenancing. Nash et al. (2020) and Harding et al. (2025) provide compelling evidence for West Woods as the primary source, supported by robust methods. Ciborowski et al. (2024) add nuance by suggesting multiple sources for smaller fragments.

Key Citations

• Nash, D. J., et al. (2020). Origins of the sarsen megaliths at Stonehenge. Science Advances, 6(31), eabc0133. https://doi.org/10.1126/sciadv.abc0133
• Nash, D. J., et al. (2021). Petrological and geochemical characterisation of the sarsen stones at Stonehenge. PLoS ONE, 16, e0254760. https://doi.org/10.1371/journal.pone.0254760
• Ciborowski, T. J. R., et al. (2024). Local and exotic sources of sarsen debitage at Stonehenge revealed by geochemical provenancing. Journal of Archaeological Science: Reports, 53, 104406. https://doi.org/10.1016/j.jasrep.2024.104406
• Hancock, R. G. V., et al. (2024). Stonehenge revisited: A geochemical approach to interpreting the geographical source of sarsen stone #58. Archaeometry. https://doi.org/10.1111/arcm.12999
• Nash, D. J., & Ciborowski, T. J. R. (2025). Comment on “Stonehenge revisited: A geochemical approach to interpreting the geographical source of sarsen stone #58”. Archaeometry, 67(1), 1–14. https://doi.org/10.1111/arcm.13105
• Harding, P., et al. (2025). Earliest movement of sarsen into the Stonehenge landscape: New insights from geochemical and visibility analysis of the Cuckoo Stone and Tor Stone. Proceedings of the Prehistoric Society, 90, 229–251. https://doi.org/10.1017/ppr.2024.13

Further Reading

• BBC News. (2020). Stonehenge: Sarsen stones origin mystery solved. Link
• Ullyott, J. S., & Nash, D. J. (2016). The sarsen stones of Stonehenge. Proceedings of the Geologists’ Association, 127(3), 363–369. https://doi.org/10.1016/j.pgeola.2015.07.005
• Archaeology UK. (n.d.). Provenancing the stones. Link
• Sarsen.org. (2020). Stonehenge: How we revealed the original source of the biggest stones. Link
• Bournemouth University. (2020). Conversation article – Stonehenge: How we revealed the original source of the biggest stones. Link