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Humans, not glacial transport, brought bluestones to Stonehenge, new research indicates

Aberystwyth University-led research has shared new findings clarifying that the enigmatic "Newall boulder" from Stonehenge was transported by Neolithic people, not by glacial transport, from Craig Rhos-y-Felin in Wales.

Stonehenge's enduring mystery extends beyond the iconic standing stones that draw visitors from around the globe. Less celebrated, yet central to archaeological debate, are the smaller, blue-hued megaliths, known as bluestones, sourced from distant outcrops in Wales, over 200 kilometers away.

Many archaeologists have attributed their arrival on Salisbury Plain to deliberate human transport. Others have proposed that glacial ice carried them during a prehistoric advance.

Limited physical evidence for either hypothesis has driven continued attention to the so-called "Newall boulder." Most bluestone materials at Stonehenge are either standing or buried monoliths. Newall boulder is a discrete, hand-sized fragment with a known excavation history, a thorough sampling record, and a plausible argument for being a previously undisturbed glacial deposit, perhaps missed by the monolith builders.

Both sides of the debate have treated Newall as a test case for resolving whether glacial or human transport brought the stones to Salisbury Plain.

In the study, "The enigmatic 'Newall boulder' excavated at Stonehenge in 1924: New data and correcting the record," in Journal of Archaeological Science: Reports, researchers conducted new mineralogical, petrographic, and geochemical analyses to determine the stone's origin and transport history.

Measuring 22 × 15 × 10 cm, the Newall boulder was recovered during Lt-Col Hawley's 1924 excavation. It was removed from the site by R.S. Newall, who kept 18 stones. The boulder was sampled by the Institute of Geological Sciences in the 1970s and by the Open University in the 1980s, with thin sections archived in the British Geological Survey and Amgueddfa Cymru, Museum Wales.

Petrographic evidence revealed that the boulder matches Rhyolite Group C from Craig Rhos-y-Felin some 200 kilometers away. Geochemical analysis reinforced these correlations.

Morphological comparisons showed the Newall boulder's bullet-shaped profile matches the tops of in situ rhyolite pillars at Craig Rhos-y-Felin and mirrors the size and shape of Stonehenge's buried stump 32d. No glacial striations were observed. Surface abrasion was attributed to weathering and post-breakage burial, not glacial transport.

Field investigations across Salisbury Plain have found no glacial deposits, no erratics (any rock or boulder that has been deposited by a glacier), and no other signs of glacial movement, either at surface or within river gravels. No glacial erratics of any kind have been found on Salisbury Plain, including within 4 km of the monument where all of the bluestones are found.

Angular fragments near the monument show edge damage consistent with deliberate shaping, not subglacial erosion.

Researchers conclude that the Newall boulder is a piece of Craig Rhos-y-Felin rhyolite, most likely broken from a monolith such as Stone 32d. All mineralogical, geochemical, and field data support human transport to Stonehenge by Neolithic people with no evidence to support glacial movement of the stone.

In discrediting the glacial hypothesis for the presence of the Newall boulder, the research bolsters the case for all of the bluestones on the plain to be the result of ancient human efforts.