Standing on Salisbury Plain like a megalithic cathedral in the centre of a huge prehistoric cemetery the ancient monument of Stonehenge has been a puzzle since Roman times: What is it? Why is it here? Where did the stones come from?
The answers to some of these questions seem unattainable even in our high-tech age and we will probably never know what purpose Stonehenge was meant to serve, yet scientists are homing in on the source of the stones.
Stonehenge sarsens and the smaller bluestones
Almost one hundred years ago the source of the bluestones, the smaller stones at Stonehenge, was first hypothesised by British geologist Herbert Henry Thomas in his seminal paper “The source of the stones of Stonehenge” (1923) as the Mynydd Preseli region of north Pembrokeshire in south west Wales.
The so called “bluestones” of Stonehenge is a collective term (unsatisfactorily) used to describe all the non-sarsen stones used in the construction of Stonehenge on Salisbury Plain in Wiltshire.
Thomas argued that the dolerite stones likely came from Carn Meini and Cerrig Marchogion and the rhyolitic stones from Carn Alw. Thomas’s theory remained unchallenged for over 80 years.
But now, owing to modern scientific advances, this most enigmatic of ancient monuments is starting to reveal its secrets.
The latest issues of the two most popular Archaeology magazines in the country both feature articles on the source of the stones of Stonehenge.
The Science of Stonehenge is the issue title on the cover of the latest edition of Current Archaeology magazine (Issue 366).
It seems the long puzzle of where the Stonehenge bluestones came from is now closing in with scientific advances allowing the scientists to pinpoint the most likely outcrops where they were first quarried with ever-greater accuracy.
An extract from the feature article Provenancing the Stones features on the Current Archaeology website.
Thomas recognised the source of some of the bluestones after he noticed the iconic white/pink spots found in the majority of the Stonehenge dolerites (the material of the most-common bluestone orthostat, and second most-common debitage) was also present in the rocks of Mynydd Preseli area in west Wales.
However, these spots vary macroscopically in size and colour between outcrops on the Preseli hills. Advances in the last ten years by Rob Ixer and Richard Bevins applying new mineralogical, petrographical, and geochemical techniques in the study of the bluestones suggests that the outcrops at Carn Goedog were the origin of most of the spotted bluestone orthostats at Stonehenge.
Further examination of the spots between different dolerites, both at Stonehenge and in the Preseli, can be used to further refine their provenance and identify further potential quarry sites.
A further mystery at Stonehenge is the presence of many thousands of pieces of buried debris (debitage), the so-called “Stonehenge Layer” found in the stone circle and scattered throughout the Stonehenge landscape.
Recent studies of samples of debitage have compared favourably to rhyolitic rocks near Pont Saeson, on the northern slopes of the Mynydd Preseli. Archaeologist Mike Parker Pearson and his team identified a potential Neolithic quarry site at Craig Rhos-y-felin as the likely source of some of rhyolitic rocks at Stonehenge.
However, although this rock-type (now designated Rhyolite Group C) is highly abundant as debitage, it only seems to match one of the buried orthostats at Stonehenge. It seems the most likely explanation of the abundance of this type of debitage is that there were other Rhyolite Group C orthostats, now totally lost, robbed or chipped away by souvenir hunters, with only the debitage as evidence of their former presence.
The cover of the latest issue of British Archaeology magazine (Issue 174 September/October 2020) features a knobbly, unworked sarsen lying in woodland, with the cover story “New: Where Stonehenge came from”.
In an exclusive feature for British Archaeology magazine, the research team claims to have shown that the sarsens, all the large stones at Stonehenge, were brought by the monument’s builders from the Marlborough Downs 20 miles to the north, identifying an area at West Woods, not proposed before, as the likely source.
The larger stones at Stonehenge comprising the huge trilithons of the central horseshoe, the uprights and lintels of the outer circle and outliers such as the heel stone, the slaughter stone and the station stones are known as “sarsens”, weighing typically 20 tonnes and up to 7 metres tall.
The name is said to have derived from the local term “saracen stone” used to identify them as relics of a non-christian age. The hard silcrete rock is found scattered naturally across southern England and also used for the stone settings at Avebury, 2o miles north of Stonehenge. Often ignored, the sarsens may hold as many secrets as the bluestones.
The first monument at Stonehenge was envisaged as a circular earthwork enclosure, constructed around 3,000 BC. An outer ditch was cut and the chalk rubble removed used to form an inner bank (the opposite to a henge bank and ditch), known as a counterscarp. Around the perimeter of this bank was a ring of 56 holes holding timber posts. The monument was used as a cremation cemetery for several hundred years until around 2,500 BC the monument was transformed by the introduction of the massive sarsen stones and the smaller bluestones.
The Stonehenge sequence has been revised recently by Mike Parker Pearson et al, suggesting that the ring of 56 pits, known as the Aubrey Holes, first contained bluestones, not timber posts at all, as the first stone setting at the monument.
The Heel Stone
However, it is possible the first stone setting at Stonehenge was the unworked, knobbly, sarsens known as the Station Stones and the Heel Stone. These stones are completely different in appearance to the finely worked sarsens of the the huge trilithons of the central horseshoe and the uprights and lintels forming the outer circle. It has been suggested that the Heel Stone was raised up from a pit close to its current position. These old sarsens were probably on the site long before the transportation of the sarsens from Marlborough Downs to construct the trilithons. Furthermore, the Station Stones appear to hold a relationship to the Mesolithic post holes found in the car park of the old visitor centre.
from: The Astronomical Significance of Stonehenge, C. A. Newham
The sarsen stones used in these megalithic monuments are said to have originated from Marlborough Downs, but their exact origin remained a mystery. Until now.
Using geochemical data scientists have found that 50 of the 52 sarsens at Stonehenge share a consistent chemistry and therefore there is a high probability that they originated from a common source area.
On comparing the geochemical signature of a core extracted from Stone 58 at Stonehenge 60 years ago with equivalent data for sarsens from across southern Britain, they have identified West Woods, on Marlborough Downs, as the most probable source area for the majority of sarsens at the monument.
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