Megalith quarries for Stonehenge bluestones

Geologists have long known that 42 of Stonehenge’s smaller stones, known as ‘bluestones’, came from the Preseli hills in Pembrokeshire, west Wales. Now a new study published in Antiquity pinpoints the exact locations of two of these quarries and reveals when and how the stones were quarried. The discovery has been made by a team of archaeologists and geologists from UCL, Bournemouth University, University of Southampton, University of the Highlands and Islands and National Museum of Wales, who have been investigating the sites for eight years.

According to Mike Parker Pearson who led the team:

• “What’s really exciting about these discoveries is that they take us a step closer to unlocking Stonehenge’s greatest mystery – why its stones came from so far away. Every other Neolithic monument in Europe was built of megaliths brought from no more than 10 miles away. We’re now looking to find out just what was so special about the Preseli hills 5,000 years ago, and whether there were any important stone circles here, built before the bluestones were moved to Stonehenge.”

The largest quarry, the dominant source of Stonehenge’s spotted dolerite, was found on the outcrop of Carn Goedog, on the north slope of the Preseli hills almost 180 miles away from the monument. In the valley below Carn Goedog, another outcrop at Craig Rhos-y-felin was identified by Richard Bevins (National Museum of Wales) and fellow geologist Rob Ixer (UCL Institute of Archaeology) as the source of one of the types of rhyolite – another type of igneous rock – found at Stonehenge.

According to the new study, the bluestone outcrops are formed of natural, vertical pillars. These could be eased off the rock face by opening up the vertical joints between each pillar. Unlike stone quarries in ancient Egypt, where obelisks were carved out of the solid rock, the Welsh quarries were easier to exploit. Neolithic quarry workers needed only to insert wedges into the ready-made joints between pillars, then lower each pillar to the foot of the outcrop. Although most of their equipment is likely to have consisted of perishable ropes and wooden wedges, mallets and levers, they left behind other tools such as hammer stones and stone wedges. Archaeological excavations at the foot of both outcrops uncovered the remains of man-made stone and earth platforms, with each platform’s outer edge terminating in a vertical drop of about a metre.

An important aim of the project team was to date megalith-quarrying at the two outcrops. In the soft sediment of a hollowed-out track leading from the loading bay at Craig Rhos-y-felin, and on the artificial platform at Carn Goedog, the team recovered pieces of charcoal dating to around 3000 BC. The team now thinks that Stonehenge was initially a circle of rough, unworked bluestone pillars set in pits known as the Aubrey Holes, near Stonehenge, and that the sarsens (sandstone blocks) were added some 500 years later.

The new discoveries also cast doubt on a popular theory that the bluestones were transported by sea to Stonehenge.

The research was funded by the British Academy, the Natural Environment Research Council (NERC), the National Geographic Society, the Society of Antiquaries, the Royal Archaeological Institute and the Cambrian Archaeological Association.

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• Antiquity article
• UCL News

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