A casual visitor to Stonehenge might be forgiven for not paying too much attention to the monument’s ‘bluestones’, the smaller uprights that form a horseshoe, and another incomplete circle, at the monument’s heart. Standing less than 3m tall, they are dwarfed by the more striking ‘sarsens’, the massive dressed and lintel-crowned sandstone monoliths that Stonehenge is famous for – but these unassuming stones have a fascinating story to tell about the site’s origins.
Around 43 bluestones survive today, but empty sockets for other bluestones hint at there once being many more, perhaps as many as 80. Nor might their present layout be their original formation: Richard Atkinson, whose excavations in the 1950s revealed so much about Stonehenge – including the presence of Bronze Age rock art etched into some of the stones (CA 273) – suggested the bluestones may have previously occupied the ‘Q’ and ‘R holes’, a series of depressions that form a circle or arc between the five sarsen trilithons and outer circle, and were only later moved to their present arrangement. But while the Q and R holes have been recently dated to c.2500 BC, it is thought that the bluestones may have arrived on Salisbury Plain even earlier.
Tantalising clues come from the Aubrey Holes, a set of 56 pits that surround Stonehenge in a large circle. William Hawley’s records of his investigations of these features in the 1920s reveal that he had little doubt that they ‘once held upright stones’, and indeed, when we excavated one of the pits during the Stonehenge Riverside Project in 2008 (CA 270), we were able to confirm that it had contained a standing stone. Might the Aubrey Holes, which date from c.2900 BC, represent the original setting of the bluestones at this earliest phase of Stonehenge, when the site began life as a cremation cemetery encircled by a ditch and bank?
While the bluestones’ layout has puzzled archaeologists since Hawley’s time, moreover, their purpose has proven equally enigmatic. Some of the stones have tenons, mortises, tongues, and grooves – were they originally intended to fit together? Might they in fact have been reused from an earlier monument? And if so, where did the stones originally stand? The answers, it is becoming increasingly clear, lie in Wales.
Although a Pembrokeshire origin for the bluestones was first proposed almost a century ago, only recently have geologists Richard Bevins and Rob Ixer definitively pinned down three areas on and around the Preseli hills where they were quarried (see p.23). To-date, in a joint undertaking with fellow project directors Josh Pollard, Colin Richards, Duncan Schlee, and Kate Welham, we have excavated two of these, at Craig Rhos-y-Felin (where the rhyolites come from) and Carn Goedog (spotted dolerite, the material that most of the bluestones are formed of).
The latter site might be one of Preseli’s less impressive dolerite outcrops, easily overshadowed by Carn Meini, where archaeologists and geologists alike have traditionally sought the Stonehenge bluestones – but it is Carn Goedog that has proven to be the major source, with 12 bluestones and numerous debitage chippings recovered from the Stonehenge landscape linked chemically to this spot and its immediate environs, while Carn Meini, despite archaeological remains clearly pointing to its use as a quarry during the Early Bronze Age, has not yet produced a single match with Stonehenge. The evidence from Carn Goedog, however, is illuminating.
We began our excavations at Carn Goedog in 2014, digging three test trenches along its southern edge where tall, thin, natural pillars in the rock face – perfect raw material for standing stones – were accessible through the surrounding scree. Much of this surface had been subjected to early modern quarrying, we quickly found, as evidenced by drill holes in the shattered rock, and the discovery of a late 18th-century coin – but one area seems to have escaped this later disturbance, and it is here that we found traces of much earlier stone extraction. In this spot we could see where whole pillars had been removed from the rock face, a technique completely different to that used by the post-medieval quarrymen, who tended to break up the rock into blocks. It was evidence for prehistoric activity on a remarkable scale.
Rock of ages
At Carn Goedog, there were several recesses in the rock face where we could clearly see that multiple pillars had been extracted, and one in particular caught our attention, where four or five pillars had already been harvested from this spot, and four more were still in situ, ready to be removed. Beneath these was a 5m by 8m platform of large, split slabs, set in a layer of soil and small stones that had been laid down deliberately on top of the natural subsoil.
Close by we found a small ditch some 2m wide at the top and narrowing to a V-shaped base. This may have simply been a boundary marker delimiting the space, or could have been dug for drainage, or as a handy place to dump loose rubble – but at some point it took on a more specific function. The stones that filled it were serving as supports for a pair of large slabs, set a metre apart on their sides, with their flat tops running parallel to the line of the ditch. Might these have been used as trestles, stone props that held a bluestone pillar at the point when it was perhaps being transferred onto a wooden sledge for transportation?
From here, it is easy to imagine how the pillars might have been removed. On top of the outcrop, behind the recesses, we identified a level area that would have provided a secure foothold from which teams could have attached ropes to the piece of rock being dislodged. Other workers standing on the platform below the base of the pillar could have pulled on ropes from below, while, with the team at the top paying out their rope and taking the strain, the pillar could have been gradually lowered from its vertical position to come to rest on the platform, and from there it could be moved with levers and pivots onto the trestles, and thence onto a wooden cradle or sledge. A 4m-wide ramp of redeposited soil, which we identified nearby, forms a likely exit from the site.
How, though, were such mighty pieces of stone removed from the rock face in the first place? There is no evidence that the pillars had been shaped in situ, or that they had been extracted using fire – but such methods would not have been necessary. Already suitably thin, the millions of years-old pillars only required loosening by opening up existing fissures, perhaps by using pick-shaped stones to chip holes into which wooden wedges could be inserted, and then the workers would have only needed to wait for rain – as plentiful in that part of the world then as it is today – to swell the wood and split the rock apart.
If such wedges were used, no trace of them have been found – wood does not survive and nor do bone or antler in this acidic soil – but we have recovered wedge holes and pick-shaped flakes of dolerite that would have been well-suited to forming the wedge holes, as well as edged tools made from mudstone.
Our research suggests that activity at Carn Goedog was extensive and enduring – for a recent radiocarbon dating of a piece of charcoal from the site reveals that Mesolithic hunter-gatherers visited this spot in c.7190-6840 BC, while people were also lighting small fires in the lee of the outcrop as late as AD 260-420. The stone platform, however, belongs to the middle Neolithic period. Three radiocarbon dates from charcoal samples place it in c.3350-3040 BC, some 400 years before the bluestones were first erected in the Aubrey Holes.
As for the stone pillars themselves, these are harder to date, particularly as tried and tested methods such as cosmogenic analysis of exposed surfaces is not effective for dolerite. Stratigraphy holds useful clues, however. Soils that have built up around the quarried pillars, and in the recess from which they were removed, hold vital information: in one such deposit, radiocarbon analysis of charcoal found at the bottom of the 0.9m-deep heap suggests that the soil began to accumulate in the early Bronze Age, probably around 2130-1900 BC.
Just two miles to the north, in the Brynberian valley, lies our other excavation site, Craig Rhos-y-Felin. Richard and Robert’s geological detective work has traced some 1,200 chips of distinctive rhyolite debitage from Stonehenge to this impressive outcrop, and, when we visited in 2010, we quickly realised it was another perfect location for a monolith quarry.
This site has yielded further tantalising clues to how the bluestones were extracted and transported. Immediately next to the geologically identified source that Robert and Richard have pinpointed, in a recess that would have once housed a pillar some 2.5m long and 0.4m wide, we found a small standing stone that had been placed in a pit and surrounded by packing stones. Might this have been a fulcrum, used to help move the detached monolith?
Close by, a hearth and occupation surface, from which flint and stone tools, as well as burnt hazelnut shells radiocarbon dated to c.3620-3360 BC and c.3500-3120 BC, suggested another link with the middle Neolithic period. This was not the only episode of prehistoric quarrying at Carn Rhos-y-Felin, however – on a manmade platform that had been built up using basket-sized loads of soil and stones, we found a large, prone monolith. Most likely quarried in the Early Bronze Age, as indicated by charcoal from the platform dating between 4330-4050 and 2140-2030 BC, this pillar had clearly been deliberately removed from the adjacent rock face, but never collected from the quarry. Closer inspection of its surface reveals why the stone may have been abandoned: it is fatally damaged, with a dramatic split shearing a large splinter from its underside.
Had the quarrying process been more successful, the stone would most likely have been removed via a second platform identified close by, which had been built against the bank of a relict stream channel, supported with a drystone wall and bonded with clay. This was connected to a distinctive hollow way where soil stains suggest that timbers may have been laid as rails. Here too are clues that might help solve a long-standing debate about how the stones were moved: the channel is only 2m wide, too narrow for the wooden rollers that have often been suggested as a likely means by which the heavy stones might have been shifted, but it could easily have accommodated a sledge.
We are still awaiting radiocarbon dates for the stone revetment and hollow way, so it is not yet clear whether they belong to the Bronze Age or Neolithic phase of quarrying. Either way, they provide a rare insight into actual methods of prehistoric monolith-moving, opening a vivid window on the distant past.
Seeking Stonehenge’s ancestor
What happened next? The bluestones ultimately ended up at Stonehenge, but it seems unlikely that it would have taken 400 years for them to get there – what then happened in the intervening centuries? Perhaps they were originally used in a Welsh monument built close to the quarries – we suspect that their initial journey was probably a short one. Aerial photography, geophysical survey, and trial excavations have proven invaluable in our search for a likely site, and several candidates have already come to light on a plateau between the two quarries. Our next season’s work in 2016 will focus on exploring these – and it is for this reason that pinpointing the exact location of the quarries has been so important, as we believe that the builders of the first bluestone monument are unlikely to have dragged its stones far from their source.
If there was a Welsh bluestone monument, however, why were its stones later moved to Salisbury Plain? Something that may represent a garbled account of a monument being brought from the west is recorded in Geoffrey of Monmouth’s 12th-century History of the Kings of Britain, in which he describes Merlin moving stones to Stonehenge from a circle known as the ‘dance of the giants’, but more concrete clues come from the archaeological record.
Recent strontium isotope analysis of the teeth of a man who had been buried under a long barrow at Winterbourne Stoke, a mile and a half from Stonehenge, in c.3500 BC, has yielded chemical clues to suggest that, like others who came after him and were buried in the Stonehenge area, this man grew up not on the Wessex chalk, but on geology far more akin to western Britain. If people as well as stones were moving from Wales to Salisbury Plain, perhaps the bluestones arrived at Stonehenge as part of a larger migration, standing as a tangible and everlasting testimony to the prehistoric pioneers’ ancestral roots far to the west.
All images: Aerial-Cam, www.aerial-cam.co.uk, unless otherwise stated.
CHECK OUT PART TWO: The search for the bluestone quarries