A new study published in the journal Communications Earth & Environment provides evidence that the bluestones and Altar Stone of Stonehenge were not transported to Salisbury Plain by glacial action.
The research used mineral fingerprinting techniques to analyze sand from local rivers, concluding that the geological material in the area is local in origin rather than derived from glacial deposits.
Research Methodology
Researchers collected sand from rivers surrounding Stonehenge to test the glacial transport theory, which proposed that ice sheets carried stones from Wales and Scotland as "glacial erratics." The study utilized U-Pb dating to analyze over 700 microscopic zircon and apatite grains. This technique measures the decay of radioactive uranium into lead to determine the age of each mineral grain.
Because different regions in Britain have distinct rock ages, a mineral's age can indicate its geological source.
If glaciers had transported the stones, they would have left behind microscopic mineral grains from the source regions, which should be detectable in the river sands of Salisbury Plain.
Key Findings
The analysis found that the mineral ages did not match the bluestone sources in Wales or the Altar Stone's source in Scotland.
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Zircon Grains: The majority of zircon crystals found in the river sands ranged between 1.7 and 1.1 billion years old. These ages align with those found in the Thanet Formation, a loose sand blanket that once covered much of southern England. This indicates the zircon is local, derived from ancient sedimentary rocks, rather than from recent glacial deposits.
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Apatite Grains: All apatite grains were approximately 60 million years old. This age does not correspond to any potential source rocks in Britain. The age is attributed to heating and chemical changes caused by distant mountain-building in the European Alps, which reset the apatite's uranium-lead clock. Like the zircon, the apatite was determined to be local to Salisbury Plain.
Conclusion
The absence of a mineral fingerprint matching the bluestone and Altar Stone source regions indicates that glacial material did not reach the Salisbury Plain area.
The findings suggest that the monument's stones were deliberately selected and transported by humans, rather than arriving through natural ice movement.