“They only had to insert wooden wedges into the cracks between the pillars and then let the Welsh rain do the rest by swelling the wood to ease each pillar off the rock face” said Dr Josh Pollard (University of Southampton).“The quarry-workers then lowered the thin pillars onto platforms of earth and stone, a sort of ‘loading bay’ from where the huge stones could be dragged away along trackways leading out of each quarry.” Professor Colin Richards (University of Manchester), an expert in Neolithic quarries, said: “The two outcrops are really impressive – they may well have had special significance for prehistoric people.When we saw them for the first time, we knew immediately that we had found the source.” Radiocarbon-dating of burnt hazelnuts and charcoal from the quarry-workers’ camp fires reveals that there were several occurrences of megalith-quarrying at these outcrops.Stonehenge was built during the Neolithic period, between 4,000 to 5,000 years ago.Geologists have known since the 1920s that the bluestones were brought to Stonehenge from somewhere in the Preseli Hills, but only now has there been collaboration with archaeologists to locate and excavate the actual quarries from which they came.Director of the project, Professor Mike Parker Pearson (UCL Institute of Archaeology), said: “This has been a wonderful opportunity for geologists and archaeologists to work together.
The team of scientists includes researchers from UCL, University of Manchester, Bournemouth University, University of Southampton, University of Leicester, Amgueddfa Cymru – National Museum Wales, and Dyfed Archaeological Trust.
The very large standing stones at Stonehenge are of ‘sarsen’, a local sandstone, but the smaller ones, known as ‘bluestones’, come from the Preseli hills in the Pembrokeshire Coast National Park.
The geologists have been able to lead us to the actual outcrops where Stonehenge’s stones were extracted.” The Stonehenge bluestones are of volcanic and igneous rocks, the most common of which are called dolerite and rhyolite.
Dr Richard Bevins (Amgueddfa Cymru – National Museum Wales) and Dr Rob Ixer (UCL and University of Leicester) have identified the outcrop of Carn Goedog as the main source of Stonehenge’s ‘spotted dolerite’ bluestones and the outcrop of Craig Rhos-y-felin as a source for one of the ‘rhyolite’ bluestones.
The research published today details excavations at Craig Rhos-y-felin specifically.The special formation of the rock, which forms natural pillars at these outcrops, allowed the prehistoric quarry-workers to detach each megalith (standing stone) with a minimum of effort.