Some of the Avebury sarsens -- compared with the sarsens at Stonehenge, rough and ready, and highly variable.
The Stonehenge sarsens -- many are "rectilinear" in shape, more spectacular to look at, with more numerous worked surfaces, and a more sophisticated setting. But some would not be out of place at Avebury.....
Map of sarsen stone occurrences across Southern England, together with related rock outcrops. (Source: Ullyott et al, 2004)
One of the most useful papers on duricrusts, silcretes and sarsens is the one published by Ullyott et al in 2004. I have mentioned it before, several times, on this blog.
DISTRIBUTION, PETROLOGY AND MODE OF DEVELOPMENT OF SILCRETES (SARSENS AND PUDDINGSTONES) ON THE EASTERN SOUTH DOWNS, UK
Earth Surf, Proc. Lanfms 29 (2004) pp 1509-1539
DOI: 10.1002/esp.1136
For example:
https://brian-mountainman.blogspot.com/2019/02/were-some-stonehenge-sarsens.html
This is David Nash's recent explanation from our discussion of a few days ago:
The development of sarsens requires two things: 1. An area of host sands and 2. Silica carried within groundwater to cement these sands. Without both host sands and a silica supply, you don’t get sarsens. If you look at geological maps of the UK (e.g. the excellent BGS ‘Geology of Britain’ viewer at https://mapapps.bgs.ac.uk/geologyofbritain/home.html) you will see that areas with sarsens today are close to or within areas underlain by sandy Paleogene sediments or their weathered remnants. Try the Marlborough area for example or the north of Brighton. To get a large area of really big sarsens, of the number and size present at Stonehenge, you’d need a really big area of sandy Paleogene sediment and these sediments would need to be really thick. Now have a look at the Stonehenge area on the BGS mapper. What do you notice? No Palaeogene sediments. No extensive areas of weathered remnants to suggest that Paleogene sediments were once there but have been eroded. On that basis, I would question whether there were ever extensive areas of big sarsens on Salisbury Plain. Put simply, no host sands = no sarsens. Even if there were sarsens, it would be incredibly convenient if every single one had been removed and used to build Stonehenge and only a few larger stones and scatters of smaller debris left behind.
How was sarsen stone formed?
Sarsen is a silcrete – a form of sandstone that has been solidified, not under pressure, but by the absorption of liquid silica. The source of the silica is not certain, though it may have come from rotting vegetation or marine life. Avebury’s sarsens appear to be a type of silcrete that generally forms in river valleys, the sand absorbing liquid silica from below by capillary action.
Around 40 million years ago, when the sarsens were formed, the Avebury landscape was probably a low-lying tropical wetland very like the Everglades of Florida today. Some sarsen stones have holes, made by the roots of plants and trees growing through the layer of sand before or during its silicification.
Although there are many holes that strongly resemble animal burrows, no animal fossils have been found in sarsen stone. There are, however, clear indications that certain holes were made by coniferous trees.
Rare pieces of petrified wood found in sarsen stone closely resemble the swamp cypress, a species of deciduous conifer common today in the Everglades, which often grows alongside mangrove species, reeds and grasses.
There is a unique fragment of petrified wood in a sarsen stone close to Avebury – a piece of twig some 40mm long by 15mm in diameter. In its cross section, tiny holes can be seen: they are resin pores, indicating that the wood is coniferous. Compare pictures of the fossil with a piece of twig of the same size found beneath one of lacock’s swamp cypresses.
Differences in sarsen stone
Not all sarsen stone is the same: there are striking differences even between adjacent stones set within the Avebury Henge. The two stones of the Avebury Cove, for instance, have quite different types of holes; their texture and shapes are also markedly different. Most tellingly, when examined with a magnifying glass one is pink, the other blue. The colours are produced by different minerals in the sand that the stones are made of, so it is unlikely that both stones could have been taken from the same natural sarsen drift. When all the Avebury stones are examined, it becomes clear that at least six distinct ‘batches’ of sarsen were used in constructing the henge and avenues.
One source could have been already inside the henge; others may have been found in the immediate area around Avebury. Since sarsen was formed on drainage lines there are several likely areas to the north-west, where the ground slopes down to the River Winterbourne and the Oslip.
In identifying the different batches, one important factor is the thickness of the stones. Almost all Avebury stones are tabular or slab-like because they were formed from a layer of sand spread over some original ground surface such as the bottom of an ancient sea or lake. At some later time the sand absorbed liquid silica that eventually hardened it, and the layer broke into smaller pieces. If the ground surface was level, we could reasonably expect the sand layer to be of a broadly consistent thickness, as will the resultant pieces of each batch. Most of the stones used in Avebury’s monuments are between about 0.4 and 0.8m thick; the largest are 1m thick.
We can usually determine which way up a stone was as it formed. The under- side may be sheer and flat, but many undersides have an uneven, rough or jagged appearance – an impression of the surface beneath the stone as it formed, as if cast in a mould. Topsides are generally smoother and more rounded, naturally weathered by wind and rain before they were hardened by silica. Stone 46 is a good example.
Occasional hollows in the ground below the original layer of sand have produced corresponding lumps and bulges on the underside of some stones.
Avebury’s Primary Stones
Was there once a natural drift of unusually large sarsens in the centre of Avebury? Cove Stone II, largest of the pair of Cove stones and weighing an estimated 100 tons, may not have been moved very far, simply because of its vast size. Cove Stone II is made of pink-grey sand with orange patches. Protruding from the fine sand grains are occasional larger pieces of rounded rose quartz. The underside of the stone is jaggedly uneven; its topside is smoother, but without the polished appearance of river formation. It has small holes made by plants but not the much larger rootholes of trees; uniquely, its topside is covered with criss-cross indentations that may have been made by fallen branches resting on the layer of sand before it hardened into sarsen. Most significantly, the slab is 1m thick, the maximum size found in Avebury.
Within the henge are another nine stones of the same thickness that share all of the above attributes except the fallen branch impressions. All are pink and tend to similarly square shapes. This suggests that all ten stones were formed from a common layer of sand a metre thick, which then broke into smaller pieces and formed a sarsen drift, likely in the centre of what is now the Avebury Henge.
The ten huge ‘Primary Stones’ are distributed around the henge, five of them used as entrance stones. Perhaps the missing entrance stones were also Primary Stones?
The Obelisk, once at the centre of the Southern Inner Ring, was described by Stukeley as a round pillar 6.4m long. Its diameter (thickness) though, was a claimed 2.7m – almost three times the thickness of any other stones in Avebury. The great size of the Obelisk suggests that it, too, may not have been moved far from where it was formed. Perhaps the Obelisk was also a Primary Stone from the same central source, but formed in a hollow in the original ground surface?
There may once have been more Primary Stones. If all were formed naturally, near what is now the centre of the henge, the drift of gigantic stones may be one reason why Avebury was initially regarded as a special place. Maybe the Primary Stones, lying in their natural state, were regarded to hold some special power – perhaps they embodied spirits? This may later have prompted the construction of the shallow Primary Earthwork – an initial bank and ditch encircling and containing the stones.
At some later date the earthwork was enlarged to massive proportions. Possibly after this, the standing stones were erected. If there was indeed a supply of large Primary Stones on site, they appear to have been used up in marking the four entrances of the henge and the centres of the two inner rings. Even twice the number of Primary Stones that survive today would not be enough to complete the entire monument, so more stones would be needed, brought into the henge from other sarsen drifts – they also may not have been far away.
Imported henge stones
Inside the Avebury Henge there is a definite pattern of distribution: related stones from different ‘batches’ of sarsen are set together in groups. This is unlikely to be for aesthetic reasons based solely on the stones’ colours. Perhaps they are grouped because they were brought into the henge from different outside sources, and moved the least possible distance?
Set close together in the north-west quadrant are six orange stones. Seven blue-coloured stones are set in a contiguous row in the south-west quadrant; two more are set near to them in the Southern Inner Circle. All are water- smoothed, unlike the five blue stones in the north-east quadrant.
There are twelve more pink stones. All are too thin to be considered as Primary Stones except possibly the large stone 77 near the eastern entrance; fallen and partially buried, there is no way to confirm its thickness. Nine of the twelve, unlike the Primary Stones, have been smoothed by running water in their formation; seven of them are set close together in the south-west quadrant.
The only Henge stones with eddy holes are grouped at the south of the henge, which suggests that they were likely imported from the same source as the stones of the West Kennet Avenue.
Z-feature of the Avebury henge
Near the centre of the Southern Inner Ring is a row of six stones that are no more than 1.5m high, far smaller than any others in Avebury. They were discovered buried by Keiller, who named them the Z-feature. All have the rounded appearance of water formation. The northernmost two stones are somewhat rougher than the rest and are made of pink sand; both have small eddy holes of different types. The other four stones are completely unlike any others in the henge or the Avenue. Highly polished by water, they are a metallic chocolate brown colour, more resembling iron than stone.
The brown colour is a thin coating known as rock varnish – a deposit of clay, iron and manganese only a micron or so thick, bonded to rock surfaces by the action of bacteria. Wind-blown in desert regions, it can take many thousands of years to accumulate. However, in splash zones close to running water it may form rapidly. Four Z-stones are coated with rock varnish on almost all sides, so a watery origin seems certain. They may have been turned repeatedly by a river as the varnish accumulated.
There must once have been a good supply of rock-varnished stones, as hundreds of broken pieces can be seen built into walls in and around Avebury. The broken stones demonstrate just how thin the layer of rock varnish is, and that beneath the dark varnish is ordinary light-coloured sarsen stone.
Rock-varnished stones near the Avebury Henge may all have been too small for use in monuments – their rounded appearance suggests that they were river boulders, smoothed to a fine polish by years of battering and rolling. The fact that so many were used in Avebury’s buildings suggests a plentiful source nearby.
A likely location would, again, be the North Kennet Valley. Small rock-varnished boulders are still found there, especially as field clearances in the hedge-lines near Falkner’s Circle. Perhaps the four rock-varnished Z-stones were selected because they were unusually large?
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Postscript 20 Aug 2020: In Mike Parker Pearson's 2012 book, he recalls Richard Atkinson's conviction that Avebury was used as a "marshalling" area for large sarsens collected further north and needed for creating at least one spectacular stone setting. He proposed that the stones were previously erected at Avebury in at least one stone circle that was later dismantled and removed for later use at Stonehenge. Nobody has ever found these "missing" stone circles. MPP also mentions Stukeley's 1723 drawing (p 298) of eleven large rectilinear sarsens lying on the ground in a cluster at Clatford -- and he is attracted by the idea that this was another marshalling yard or a location where large sarsens were partially shaped or dressed before being hauled off along one route or another to Stonehenge. MPP assumes that these stones were not in their natural positions but were brought in from one or more quarries in the vicinity. This is all very fanciful, both on the part of Atkinson and MPP -- and we can see where the idea of proto-Stonehenge (erected, dismantled and removed for future use) has come from. It also explains the idea that if there was one sarsen proto-Stonehenge, then there should have also been a bluestone proto-Stonehenge somewhere in Pembrokeshire -- with Waun Mawn fitting the bill rather nicely!!! Ah, the seductive appeal of the fanciful narrative......
David Field and Trevor Pearson
STONEHENGE WORLD HERITAGE SITE LANDSCAPE PROJECT
STONEHENGE, AMESBURY, WILTSHIRE
ARCHAEOLOGICAL SURVEY REPORT
EH Research Department Report Series
NGR: SU 12244219
Hoare wavered and considered on one hand that the Marlborough Downs was a potential source but also that the origin of the sarsens at Stonehenge could be local, ‘the plains adjoining Stonehenge might very probably have furnished stones suffciently large’ (Hoare 1812, 149, 152). The Rev E Duke (1846, 170) questioned the assumption that the sarsens had been brought from the Marlborough Downs and noted that none are now to be found of that size there. Instead, he suggested that the boulders were ‘quarried from a continuous stratum’ and indeed such seams are thought to exist around Avebury (Barker 1985, 21). Petrie noted that there were few or no sarsens of the required size to be found elsewhere, that is on the Marlborough Downs, and considered whether the very position of Stonehenge was determined by the presence of a quantity of sarsens that had derived from denuded beds formerly lying over the chalk and on balance thought that they had been collected from the immediate vicinity.
Gowland similarly considered them brought from ‘within a radius of not many miles’ and ‘probably at no great distance from the spot where the structure stands’ (Gowland 1902, 75, 115) rather than from a distant locality, while the geologist Prof J W Judd (1901, 115-6) thought likewise and that they had moved ‘only a few hundred yards’. H H Thomas (1923, 242) considered that they may have come from ‘the site of Stonehenge itself ’. It was a good point made by Johnson (2008, 121) that the Heel Stone is too awkward and bulky a shape to move on rollers and it, at least, is unlikely to have travelled far. Equally the much smaller undressed Station Stones may be quite local. It is after all possible to find larger stones on Salisbury Plain without having to travel to the Marlborough Downs for them. If these points are accepted it becomes easier to acknowledge that the sarsen group as a whole may not have been the product of a heroic journey.
The diffculty in working sarsen is well-known (Fig 14) and while weathered sarsen lying on the surface has an exceedingly tough crust, Isobel Geddes crucially pointed out that in contrast
buried sarsen is soft and can be easily worked (Geddes 2000: also Bowen & Smith 1977, 189). This was something also noted by Cunnington: ‘when frst dug out of the ground they are soft like freestone just quarried….if broken you may crumble the inside pieces between your fngers like Lump Sugar’ (Cunnington MSS Book 4, 34). Geddes also pointed out that the only place where sarsen boulders large enough for Stonehenge monoliths have been found in recent times is below the surface in swallow holes where they have been protected from weathering (Bowen & Smith 1977, 189 refer to this also). It is worth noting that there are at least two such holes, potentially more, in the Stonehenge landscape.
In an Email exchange with Edward Pegler, David Field wrote:
.....There are quite a few smaller sarsens around on Salisbury Plain and some were indeed incorporated into long barrows. Knook Barrow had a cairn of sarsen, Arn Hill long barrow had a standing stone, Corton long barrow had a ‘massive boulder’. Cunnington said that sarsens can be found all over the downs beneath the turf and that farmers plough them up in the area north of Stonehenge (Larkhill west of barracks) from time to time. There is a long barrow there (Figheledean 31-see attached) with three in the ditch and another six in a line where they were disturbed when the military built a rifle range. Quite a few around Bulford, aside from the Cuckoo stone (attached), Togstone and the one in the river, there is one from a round barrow that had a burial beneath an ‘immense sarsen’ and a number of others noted on early maps. One of the King Barrows formerly had a sarsen circle or kerb around it. Today the Imber to Chittern valley has many small boulders and cobbles on the slopes and in the stream and presumably many more were once visible when the area was cultivated.
As you rightly say, none of these are large in trilithon terms, but then neither are any of those on the Marlborough Downs where they rarely exceed a couple of metres – three at the most. The big ones there seem to have been reserved for the Cove and blocking stones at West Kennet. The survival of many on the Marlborough Downs can be put down to lack of agriculture (it’s a degree colder there than Salisbury Plain) for they get in the way of ploughs and soon get cleared and broken up or buried. You can trace the clearance process at Overton/Fyfield from undisturbed sarsens on the summits, to the clearance to field edges to create ‘Celtic’ Fields in the Bronze Age on the upper slopes, to the development of lyncheted fields that cover the sarsens around the edge in the Roman and medieval periods on the lower slopes. If the same processes took place on Salisbury Plain where there was widespread agriculture in Roman, medieval and post-medieval times there will be many other sarsens buried beneath the field lynchets. So where did the big ones come from?”
There is much to argue about!! Suffice to say that there is academic disagreement on whether there ever were sufficient large sarsen stones on Salisbury Plain, in the vicinity of Stonehenge, for local stones to have made up the greater part, if not all, of the monument. But there still are sufficient sarsens in the landscape for tests on three stones to have been done, and I am still disappointed that the research team decided not to do so. After all, both Avebury and Stonehenge lie well away from the nearest Palaeogene outcrop; if Avebury had a good scatter of sarsens in the Neolithic period, why not assume something similar for Stonehenge? The Avebury sarsen scatter seems to fly in the face of David's comment which I have inserted at the head of this post. And if, as now seems very likely, the Avebury stones were used more or less where they were found (ie without any elaborate stone quarrying or gathering expeditions to distant locations), why not assume that the same principle would have applied at Stonehenge too?
I have already mentioned to David that the idea that "since the Neolithic tribes collected bluestones from Pembrokeshire, they must have had no problem in collecting sarsens as well from distant locations" involves circular reasoning: since they were clever enough to do THIS, they were probably clever enough to do THAT too. And vice versa..... The idea of the long-distance haulage of the bluestones is a myth, unsupported by any evidence.
I also part company with David when says of the Stonehenge neighbourhood: "Even if there were sarsens, it would be incredibly convenient if every single one had been removed and used to build Stonehenge and only a few larger stones and scatters of smaller debris left behind." That's another assertion or assumption -- namely that Stonehenge WAS completed, with c 82 stones tidily in place. With all due respect, that has never been proved either. It is in my view much more likely that Stonehenge was started by a group of people with grand aspirations but with limited manpower and limited technical resources, in a location where stones (sarsens and bluestones) were relatively plentiful. They grouped the stones and used them in different parts of the monument, frequently changing their settings and design plans. Sadly, they never had enough stones, and had to rove over a greater and greater area in their hunt for boulders and monoliths. Eventually they just ran out of energy, and ran out of stones. So the monument was never completed, and was eventually abandoned.
That is, to my mind, a much more reasonable hypothesis and a much more compelling narrative. It may or may not be true, but I think it accords rather more closely with the evidence on the ground.
So -- back to the sarsens and the recent paper by Nash et al. The wording in the paper is quite cautious -- the authors say it is "most likely" that the sarsens -- or most of them -- came from West Woods. I can live with that wording, or something close to it. But to say that "we now know where the sarsens came from" (as Tim Darvill has done) is the sort of statement that would never get a PhD candidate through a doctorate viva, and it should not be acceptable on social media either. The very best we can say is that "Most of the sarsens at Stonehenge are closely matched geochemically, and of the sites examined by the researchers, the sarsens at West Woods provide the best match in the field." That isn't nit-picking -- it's a matter of scientific accuracy.
Partly this is a matter of sampling density. Only six sites have been sampled thus far in the "predicted sarsen collecting area" -- and there has to be much uncertainty about the accuracy of the recent provenancing work since many other sites are still to be investigated.
There is not much more that can be done at the moment, but as noted above, David Nash promises that there will be further research on Salisbury Plain if funding can be found, and we await with interest the forthcoming results.
https://brian-mountainman.blogspot.com/2019/02/were-some-stonehenge-sarsens.html
This is David Nash's recent explanation from our discussion of a few days ago:
The development of sarsens requires two things: 1. An area of host sands and 2. Silica carried within groundwater to cement these sands. Without both host sands and a silica supply, you don’t get sarsens. If you look at geological maps of the UK (e.g. the excellent BGS ‘Geology of Britain’ viewer at https://mapapps.bgs.ac.uk/geologyofbritain/home.html) you will see that areas with sarsens today are close to or within areas underlain by sandy Paleogene sediments or their weathered remnants. Try the Marlborough area for example or the north of Brighton. To get a large area of really big sarsens, of the number and size present at Stonehenge, you’d need a really big area of sandy Paleogene sediment and these sediments would need to be really thick. Now have a look at the Stonehenge area on the BGS mapper. What do you notice? No Palaeogene sediments. No extensive areas of weathered remnants to suggest that Paleogene sediments were once there but have been eroded. On that basis, I would question whether there were ever extensive areas of big sarsens on Salisbury Plain. Put simply, no host sands = no sarsens. Even if there were sarsens, it would be incredibly convenient if every single one had been removed and used to build Stonehenge and only a few larger stones and scatters of smaller debris left behind.
That's a nice concise summary, and it's good to have it on the record. There are several interesting points in there, to which I will return. David says that he has an extended article on Salisbury Plain in preparation; we look forward to seeing that in print.
First, let's take a look at Avebury, which is in the minds of many a much more impressive monument than Stonehenge. At least 200 substantial sarsens have been used there in a number of stone settings. On the Avebury sarsens, we can't do better than referring to Steve Marshall's excellent book (go out and buy it!) which is not only a good read but which has superb illustrations of every single sarsen stone on the extensive site, highlighting variations in stone dimensions, shapes, colours, textures and internal characteristics.
First, let's take a look at Avebury, which is in the minds of many a much more impressive monument than Stonehenge. At least 200 substantial sarsens have been used there in a number of stone settings. On the Avebury sarsens, we can't do better than referring to Steve Marshall's excellent book (go out and buy it!) which is not only a good read but which has superb illustrations of every single sarsen stone on the extensive site, highlighting variations in stone dimensions, shapes, colours, textures and internal characteristics.
AVEBURY
Reference: Steve Marshall: Exploring Avebury — the essential guide (2016)
Description of every single stone:
http://www.exploringavebury.com/geology
My review and summary of the book:
https://brian-mountainman.blogspot.com/2016/07/exploring-avebury-essential-guide-by.html
Description of every single stone:
http://www.exploringavebury.com/geology
My review and summary of the book:
https://brian-mountainman.blogspot.com/2016/07/exploring-avebury-essential-guide-by.html
----------------------------------------
Quote:
How was sarsen stone formed?
Sarsen is a silcrete – a form of sandstone that has been solidified, not under pressure, but by the absorption of liquid silica. The source of the silica is not certain, though it may have come from rotting vegetation or marine life. Avebury’s sarsens appear to be a type of silcrete that generally forms in river valleys, the sand absorbing liquid silica from below by capillary action.
Around 40 million years ago, when the sarsens were formed, the Avebury landscape was probably a low-lying tropical wetland very like the Everglades of Florida today. Some sarsen stones have holes, made by the roots of plants and trees growing through the layer of sand before or during its silicification.
Although there are many holes that strongly resemble animal burrows, no animal fossils have been found in sarsen stone. There are, however, clear indications that certain holes were made by coniferous trees.
Rare pieces of petrified wood found in sarsen stone closely resemble the swamp cypress, a species of deciduous conifer common today in the Everglades, which often grows alongside mangrove species, reeds and grasses.
There is a unique fragment of petrified wood in a sarsen stone close to Avebury – a piece of twig some 40mm long by 15mm in diameter. In its cross section, tiny holes can be seen: they are resin pores, indicating that the wood is coniferous. Compare pictures of the fossil with a piece of twig of the same size found beneath one of lacock’s swamp cypresses.
Differences in sarsen stone
Not all sarsen stone is the same: there are striking differences even between adjacent stones set within the Avebury Henge. The two stones of the Avebury Cove, for instance, have quite different types of holes; their texture and shapes are also markedly different. Most tellingly, when examined with a magnifying glass one is pink, the other blue. The colours are produced by different minerals in the sand that the stones are made of, so it is unlikely that both stones could have been taken from the same natural sarsen drift. When all the Avebury stones are examined, it becomes clear that at least six distinct ‘batches’ of sarsen were used in constructing the henge and avenues.
One source could have been already inside the henge; others may have been found in the immediate area around Avebury. Since sarsen was formed on drainage lines there are several likely areas to the north-west, where the ground slopes down to the River Winterbourne and the Oslip.
In identifying the different batches, one important factor is the thickness of the stones. Almost all Avebury stones are tabular or slab-like because they were formed from a layer of sand spread over some original ground surface such as the bottom of an ancient sea or lake. At some later time the sand absorbed liquid silica that eventually hardened it, and the layer broke into smaller pieces. If the ground surface was level, we could reasonably expect the sand layer to be of a broadly consistent thickness, as will the resultant pieces of each batch. Most of the stones used in Avebury’s monuments are between about 0.4 and 0.8m thick; the largest are 1m thick.
We can usually determine which way up a stone was as it formed. The under- side may be sheer and flat, but many undersides have an uneven, rough or jagged appearance – an impression of the surface beneath the stone as it formed, as if cast in a mould. Topsides are generally smoother and more rounded, naturally weathered by wind and rain before they were hardened by silica. Stone 46 is a good example.
Occasional hollows in the ground below the original layer of sand have produced corresponding lumps and bulges on the underside of some stones.
Avebury’s Primary Stones
Was there once a natural drift of unusually large sarsens in the centre of Avebury? Cove Stone II, largest of the pair of Cove stones and weighing an estimated 100 tons, may not have been moved very far, simply because of its vast size. Cove Stone II is made of pink-grey sand with orange patches. Protruding from the fine sand grains are occasional larger pieces of rounded rose quartz. The underside of the stone is jaggedly uneven; its topside is smoother, but without the polished appearance of river formation. It has small holes made by plants but not the much larger rootholes of trees; uniquely, its topside is covered with criss-cross indentations that may have been made by fallen branches resting on the layer of sand before it hardened into sarsen. Most significantly, the slab is 1m thick, the maximum size found in Avebury.
Within the henge are another nine stones of the same thickness that share all of the above attributes except the fallen branch impressions. All are pink and tend to similarly square shapes. This suggests that all ten stones were formed from a common layer of sand a metre thick, which then broke into smaller pieces and formed a sarsen drift, likely in the centre of what is now the Avebury Henge.
The ten huge ‘Primary Stones’ are distributed around the henge, five of them used as entrance stones. Perhaps the missing entrance stones were also Primary Stones?
The Obelisk, once at the centre of the Southern Inner Ring, was described by Stukeley as a round pillar 6.4m long. Its diameter (thickness) though, was a claimed 2.7m – almost three times the thickness of any other stones in Avebury. The great size of the Obelisk suggests that it, too, may not have been moved far from where it was formed. Perhaps the Obelisk was also a Primary Stone from the same central source, but formed in a hollow in the original ground surface?
There may once have been more Primary Stones. If all were formed naturally, near what is now the centre of the henge, the drift of gigantic stones may be one reason why Avebury was initially regarded as a special place. Maybe the Primary Stones, lying in their natural state, were regarded to hold some special power – perhaps they embodied spirits? This may later have prompted the construction of the shallow Primary Earthwork – an initial bank and ditch encircling and containing the stones.
At some later date the earthwork was enlarged to massive proportions. Possibly after this, the standing stones were erected. If there was indeed a supply of large Primary Stones on site, they appear to have been used up in marking the four entrances of the henge and the centres of the two inner rings. Even twice the number of Primary Stones that survive today would not be enough to complete the entire monument, so more stones would be needed, brought into the henge from other sarsen drifts – they also may not have been far away.
Imported henge stones
Inside the Avebury Henge there is a definite pattern of distribution: related stones from different ‘batches’ of sarsen are set together in groups. This is unlikely to be for aesthetic reasons based solely on the stones’ colours. Perhaps they are grouped because they were brought into the henge from different outside sources, and moved the least possible distance?
Set close together in the north-west quadrant are six orange stones. Seven blue-coloured stones are set in a contiguous row in the south-west quadrant; two more are set near to them in the Southern Inner Circle. All are water- smoothed, unlike the five blue stones in the north-east quadrant.
There are twelve more pink stones. All are too thin to be considered as Primary Stones except possibly the large stone 77 near the eastern entrance; fallen and partially buried, there is no way to confirm its thickness. Nine of the twelve, unlike the Primary Stones, have been smoothed by running water in their formation; seven of them are set close together in the south-west quadrant.
The only Henge stones with eddy holes are grouped at the south of the henge, which suggests that they were likely imported from the same source as the stones of the West Kennet Avenue.
Z-feature of the Avebury henge
Near the centre of the Southern Inner Ring is a row of six stones that are no more than 1.5m high, far smaller than any others in Avebury. They were discovered buried by Keiller, who named them the Z-feature. All have the rounded appearance of water formation. The northernmost two stones are somewhat rougher than the rest and are made of pink sand; both have small eddy holes of different types. The other four stones are completely unlike any others in the henge or the Avenue. Highly polished by water, they are a metallic chocolate brown colour, more resembling iron than stone.
The brown colour is a thin coating known as rock varnish – a deposit of clay, iron and manganese only a micron or so thick, bonded to rock surfaces by the action of bacteria. Wind-blown in desert regions, it can take many thousands of years to accumulate. However, in splash zones close to running water it may form rapidly. Four Z-stones are coated with rock varnish on almost all sides, so a watery origin seems certain. They may have been turned repeatedly by a river as the varnish accumulated.
There must once have been a good supply of rock-varnished stones, as hundreds of broken pieces can be seen built into walls in and around Avebury. The broken stones demonstrate just how thin the layer of rock varnish is, and that beneath the dark varnish is ordinary light-coloured sarsen stone.
Rock-varnished stones near the Avebury Henge may all have been too small for use in monuments – their rounded appearance suggests that they were river boulders, smoothed to a fine polish by years of battering and rolling. The fact that so many were used in Avebury’s buildings suggests a plentiful source nearby.
A likely location would, again, be the North Kennet Valley. Small rock-varnished boulders are still found there, especially as field clearances in the hedge-lines near Falkner’s Circle. Perhaps the four rock-varnished Z-stones were selected because they were unusually large?
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Postscript 20 Aug 2020: In Mike Parker Pearson's 2012 book, he recalls Richard Atkinson's conviction that Avebury was used as a "marshalling" area for large sarsens collected further north and needed for creating at least one spectacular stone setting. He proposed that the stones were previously erected at Avebury in at least one stone circle that was later dismantled and removed for later use at Stonehenge. Nobody has ever found these "missing" stone circles. MPP also mentions Stukeley's 1723 drawing (p 298) of eleven large rectilinear sarsens lying on the ground in a cluster at Clatford -- and he is attracted by the idea that this was another marshalling yard or a location where large sarsens were partially shaped or dressed before being hauled off along one route or another to Stonehenge. MPP assumes that these stones were not in their natural positions but were brought in from one or more quarries in the vicinity. This is all very fanciful, both on the part of Atkinson and MPP -- and we can see where the idea of proto-Stonehenge (erected, dismantled and removed for future use) has come from. It also explains the idea that if there was one sarsen proto-Stonehenge, then there should have also been a bluestone proto-Stonehenge somewhere in Pembrokeshire -- with Waun Mawn fitting the bill rather nicely!!! Ah, the seductive appeal of the fanciful narrative......
The old Stukeley sketch of eleven large sarsens lying around on the ground at Clatford. In situ or imported? That is the question......
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From Steve's descriptions, we can cull several important points:
1. In all probability, the monument was built here because that is where the stones were. Steve does not agree with Prof Richard Atkinson, who thought that the stones were all imported from some "quarrying location" to the north. When Samuel Pepys passed this way after visiting Avebury Circle he noted: “About a mile on it was prodigious to see how full the downes are of great stones and all along the valleys stones of considerable bigness most of them growing certainly out of the ground so.... thick as to cover the ground.... which makes me think the less of the wonder of Stonage for hence they might undoubtedly supply themselves with stones as well as those at Abebery (Avebury).”
It's also interesting that Steve uses West Woods as a model of what the Avebury landscape might have looked like before sarsen clearance: "West Woods, best known for its extraordinary show of spring bluebells, also has a sizeable drift of sarsen stones scattered amongst the trees. This is likely how the Avebury area appeared in the Mesolithic, before its forests were cleared." (p 138)
It's also interesting that Steve uses West Woods as a model of what the Avebury landscape might have looked like before sarsen clearance: "West Woods, best known for its extraordinary show of spring bluebells, also has a sizeable drift of sarsen stones scattered amongst the trees. This is likely how the Avebury area appeared in the Mesolithic, before its forests were cleared." (p 138)
2. There are at least six types of sarsen at Avebury, classified mostly on the basis of colour and texture.
3. The different types of sarsen are found in different groupings, implying a degree of selection and gathering from different areas in the locality. There is some evidence from cropmarks and "dappled marks" of extraction pits close to the southern end of the West Kennet Avenue -- showing the likely sources for at least some of the standing stones.
4. The sarsen stones (large and small) are all that is left of the Palaeogene deposits that once must have existed in the area. (This appears to be confirmed from a look at the BGS Viewer which shows the detailed local geological map.) The nearest Palaeogene deposits (belonging to the Lambeth Group and the Thames Group) are about 12 km from Avebury, to the ESE.
5. There do appear to have been some sarsens that have come from "sarsen beds" over 1m thick -- implying the past presence of thick sandy Palaeogene sediments which have now been eroded away.
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STONEHENGE
There is an endless literature about the nature of the Stonehenge sarsens, and now, following the new work by David Nash and colleagues, we know a great deal more. There are clearly fifty sarsens with a very similar geochemistry, and two others (stones 28 and 160) with distinct and different geochemistries. By and large, the smooth and rather elegant sarsens here look different from those of Avebury, partly because a lot of work has been done on the Stonehenge pillars and lintels -- but they are certainly less rough and "lumpy" that the Avebury stones.
Ullyott et al (2004), concentrating for the most part on the South Downs, referred to three basic sarsen stone types: grey ‘saccharoid’ (or arenaceous) sarsen; (2) brown ‘hard’ (or loamy fine-grained) sarsen; and (3) and a conglomerate type with a larger variety of particle sizes, called puddingstone. Saccharoid sarsens are by far the most abundant across southern England. Quote from p 1535: "Silcretes in higher landscape settings exhibit mainly angular tabular or prismatic shapes whilst those in lower positions are typically more rounded, suggesting surface weathering and erosion during transport of originally more angular tabular blocks derived from a localized higher level silcrete lens (or lenses)." In our recent correspondence David Nash seems to suggest that large tabular monoliths like those at Stonehenge are most likely to occur on interfluves in close proximity to outliers of Palaeogene sediments, while sarsens with more weathered surfaces and more irregular or rounded shapes are more likely to occur in valleys or on lowlands where they may have been moved by periglacial and other processes. (See also the recent paper by Peter Worsley:
https://brian-mountainman.blogspot.com/2020/07/clatford-bottom-and-sarsens.html )
Then there are colour differences -- Steve Hooker has pointed out that while most of the Stonehenge sarsens are grey or blue-grey in colour, some (53, 56 and 154) are purple and some (55a and 55b) are orange. There appear to be other colour clusters too -- 60, 152 and 158 appear to be dark in colour, while 51, 52, 57, 58 and 160 a, b and c are medium grey and 59a, b and c are light grey. David Nash and his team also looked at colour differences. As Steve Marshall has pointed out at Avebury, these colour variations may be due to differential post-formation mineral staining (or to the presence of algae?) which has little to do with the geochemistry of the rock but which may say something about depositional history and emplacement following the destruction of the bulk of the Palaeogene beds.
The new work is very valuable in this respect, since it appears to show that these colour variations do not coincide with great geochemical variations -- but stone 55 (the orange one) looks like an outlier. It would be good to get an expert view on that. Of course the colour variations may indicate locational "clusters" of stones which shared the same precise post-formational history. No doubt this will be examined in future work by David Nash and his team.
OK -- back to the question of whether there ever was an extensive cover of sarsens on Salisbury Plain, close to Stonehenge. David suggests that because there are nowadays no extensive Palaeogene sediments there (not even any small remnants) it is unlikely that there ever were enough big stones worthy of collection by the Neolithic tribes. However, there are plenty of considered opinions to the contrary:
3. The different types of sarsen are found in different groupings, implying a degree of selection and gathering from different areas in the locality. There is some evidence from cropmarks and "dappled marks" of extraction pits close to the southern end of the West Kennet Avenue -- showing the likely sources for at least some of the standing stones.
4. The sarsen stones (large and small) are all that is left of the Palaeogene deposits that once must have existed in the area. (This appears to be confirmed from a look at the BGS Viewer which shows the detailed local geological map.) The nearest Palaeogene deposits (belonging to the Lambeth Group and the Thames Group) are about 12 km from Avebury, to the ESE.
5. There do appear to have been some sarsens that have come from "sarsen beds" over 1m thick -- implying the past presence of thick sandy Palaeogene sediments which have now been eroded away.
The Avebury Obelisk -- a vast recumbent stone. Was it this stone which determined the location of the Avebury monument? It may have been 2.7m thick, which implies formation in a very thick sand layer which has subsequently disappeared.
The various "sarsen drifts" that might have provided some of the Avebury stones are now much depleted after centuries of exploitation (some of it on an industrial scale); Fyfield Down lies to the east, and Piggledene and Lockeridge Dene lie to the SE.
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STONEHENGE
There is an endless literature about the nature of the Stonehenge sarsens, and now, following the new work by David Nash and colleagues, we know a great deal more. There are clearly fifty sarsens with a very similar geochemistry, and two others (stones 28 and 160) with distinct and different geochemistries. By and large, the smooth and rather elegant sarsens here look different from those of Avebury, partly because a lot of work has been done on the Stonehenge pillars and lintels -- but they are certainly less rough and "lumpy" that the Avebury stones.
Ullyott et al (2004), concentrating for the most part on the South Downs, referred to three basic sarsen stone types: grey ‘saccharoid’ (or arenaceous) sarsen; (2) brown ‘hard’ (or loamy fine-grained) sarsen; and (3) and a conglomerate type with a larger variety of particle sizes, called puddingstone. Saccharoid sarsens are by far the most abundant across southern England. Quote from p 1535: "Silcretes in higher landscape settings exhibit mainly angular tabular or prismatic shapes whilst those in lower positions are typically more rounded, suggesting surface weathering and erosion during transport of originally more angular tabular blocks derived from a localized higher level silcrete lens (or lenses)." In our recent correspondence David Nash seems to suggest that large tabular monoliths like those at Stonehenge are most likely to occur on interfluves in close proximity to outliers of Palaeogene sediments, while sarsens with more weathered surfaces and more irregular or rounded shapes are more likely to occur in valleys or on lowlands where they may have been moved by periglacial and other processes. (See also the recent paper by Peter Worsley:
https://brian-mountainman.blogspot.com/2020/07/clatford-bottom-and-sarsens.html )
Then there are colour differences -- Steve Hooker has pointed out that while most of the Stonehenge sarsens are grey or blue-grey in colour, some (53, 56 and 154) are purple and some (55a and 55b) are orange. There appear to be other colour clusters too -- 60, 152 and 158 appear to be dark in colour, while 51, 52, 57, 58 and 160 a, b and c are medium grey and 59a, b and c are light grey. David Nash and his team also looked at colour differences. As Steve Marshall has pointed out at Avebury, these colour variations may be due to differential post-formation mineral staining (or to the presence of algae?) which has little to do with the geochemistry of the rock but which may say something about depositional history and emplacement following the destruction of the bulk of the Palaeogene beds.
The new work is very valuable in this respect, since it appears to show that these colour variations do not coincide with great geochemical variations -- but stone 55 (the orange one) looks like an outlier. It would be good to get an expert view on that. Of course the colour variations may indicate locational "clusters" of stones which shared the same precise post-formational history. No doubt this will be examined in future work by David Nash and his team.
Stone 55, from the Stones of Stonehenge web site (pic: Simon Banton.) The orange colouring is apparent.
OK -- back to the question of whether there ever was an extensive cover of sarsens on Salisbury Plain, close to Stonehenge. David suggests that because there are nowadays no extensive Palaeogene sediments there (not even any small remnants) it is unlikely that there ever were enough big stones worthy of collection by the Neolithic tribes. However, there are plenty of considered opinions to the contrary:
STONEHENGE WORLD HERITAGE SITE LANDSCAPE PROJECT
STONEHENGE, AMESBURY, WILTSHIRE
ARCHAEOLOGICAL SURVEY REPORT
EH Research Department Report Series
NGR: SU 12244219
Extract:
Hoare wavered and considered on one hand that the Marlborough Downs was a potential source but also that the origin of the sarsens at Stonehenge could be local, ‘the plains adjoining Stonehenge might very probably have furnished stones suffciently large’ (Hoare 1812, 149, 152). The Rev E Duke (1846, 170) questioned the assumption that the sarsens had been brought from the Marlborough Downs and noted that none are now to be found of that size there. Instead, he suggested that the boulders were ‘quarried from a continuous stratum’ and indeed such seams are thought to exist around Avebury (Barker 1985, 21). Petrie noted that there were few or no sarsens of the required size to be found elsewhere, that is on the Marlborough Downs, and considered whether the very position of Stonehenge was determined by the presence of a quantity of sarsens that had derived from denuded beds formerly lying over the chalk and on balance thought that they had been collected from the immediate vicinity.
Gowland similarly considered them brought from ‘within a radius of not many miles’ and ‘probably at no great distance from the spot where the structure stands’ (Gowland 1902, 75, 115) rather than from a distant locality, while the geologist Prof J W Judd (1901, 115-6) thought likewise and that they had moved ‘only a few hundred yards’. H H Thomas (1923, 242) considered that they may have come from ‘the site of Stonehenge itself ’. It was a good point made by Johnson (2008, 121) that the Heel Stone is too awkward and bulky a shape to move on rollers and it, at least, is unlikely to have travelled far. Equally the much smaller undressed Station Stones may be quite local. It is after all possible to find larger stones on Salisbury Plain without having to travel to the Marlborough Downs for them. If these points are accepted it becomes easier to acknowledge that the sarsen group as a whole may not have been the product of a heroic journey.
The diffculty in working sarsen is well-known (Fig 14) and while weathered sarsen lying on the surface has an exceedingly tough crust, Isobel Geddes crucially pointed out that in contrast
buried sarsen is soft and can be easily worked (Geddes 2000: also Bowen & Smith 1977, 189). This was something also noted by Cunnington: ‘when frst dug out of the ground they are soft like freestone just quarried….if broken you may crumble the inside pieces between your fngers like Lump Sugar’ (Cunnington MSS Book 4, 34). Geddes also pointed out that the only place where sarsen boulders large enough for Stonehenge monoliths have been found in recent times is below the surface in swallow holes where they have been protected from weathering (Bowen & Smith 1977, 189 refer to this also). It is worth noting that there are at least two such holes, potentially more, in the Stonehenge landscape.
In an Email exchange with Edward Pegler, David Field wrote:
.....There are quite a few smaller sarsens around on Salisbury Plain and some were indeed incorporated into long barrows. Knook Barrow had a cairn of sarsen, Arn Hill long barrow had a standing stone, Corton long barrow had a ‘massive boulder’. Cunnington said that sarsens can be found all over the downs beneath the turf and that farmers plough them up in the area north of Stonehenge (Larkhill west of barracks) from time to time. There is a long barrow there (Figheledean 31-see attached) with three in the ditch and another six in a line where they were disturbed when the military built a rifle range. Quite a few around Bulford, aside from the Cuckoo stone (attached), Togstone and the one in the river, there is one from a round barrow that had a burial beneath an ‘immense sarsen’ and a number of others noted on early maps. One of the King Barrows formerly had a sarsen circle or kerb around it. Today the Imber to Chittern valley has many small boulders and cobbles on the slopes and in the stream and presumably many more were once visible when the area was cultivated.
As you rightly say, none of these are large in trilithon terms, but then neither are any of those on the Marlborough Downs where they rarely exceed a couple of metres – three at the most. The big ones there seem to have been reserved for the Cove and blocking stones at West Kennet. The survival of many on the Marlborough Downs can be put down to lack of agriculture (it’s a degree colder there than Salisbury Plain) for they get in the way of ploughs and soon get cleared and broken up or buried. You can trace the clearance process at Overton/Fyfield from undisturbed sarsens on the summits, to the clearance to field edges to create ‘Celtic’ Fields in the Bronze Age on the upper slopes, to the development of lyncheted fields that cover the sarsens around the edge in the Roman and medieval periods on the lower slopes. If the same processes took place on Salisbury Plain where there was widespread agriculture in Roman, medieval and post-medieval times there will be many other sarsens buried beneath the field lynchets. So where did the big ones come from?”
Courtesy David Field, a sketch commissioned in an attempt to portray the Stonehenge
landscape during "Stonehenge Plase One". There is perhaps an over-enthusiastic
portrayal of the sarsen litter!
portrayal of the sarsen litter!
Another relevant post:
There is much to argue about!! Suffice to say that there is academic disagreement on whether there ever were sufficient large sarsen stones on Salisbury Plain, in the vicinity of Stonehenge, for local stones to have made up the greater part, if not all, of the monument. But there still are sufficient sarsens in the landscape for tests on three stones to have been done, and I am still disappointed that the research team decided not to do so. After all, both Avebury and Stonehenge lie well away from the nearest Palaeogene outcrop; if Avebury had a good scatter of sarsens in the Neolithic period, why not assume something similar for Stonehenge? The Avebury sarsen scatter seems to fly in the face of David's comment which I have inserted at the head of this post. And if, as now seems very likely, the Avebury stones were used more or less where they were found (ie without any elaborate stone quarrying or gathering expeditions to distant locations), why not assume that the same principle would have applied at Stonehenge too?
I have already mentioned to David that the idea that "since the Neolithic tribes collected bluestones from Pembrokeshire, they must have had no problem in collecting sarsens as well from distant locations" involves circular reasoning: since they were clever enough to do THIS, they were probably clever enough to do THAT too. And vice versa..... The idea of the long-distance haulage of the bluestones is a myth, unsupported by any evidence.
I also part company with David when says of the Stonehenge neighbourhood: "Even if there were sarsens, it would be incredibly convenient if every single one had been removed and used to build Stonehenge and only a few larger stones and scatters of smaller debris left behind." That's another assertion or assumption -- namely that Stonehenge WAS completed, with c 82 stones tidily in place. With all due respect, that has never been proved either. It is in my view much more likely that Stonehenge was started by a group of people with grand aspirations but with limited manpower and limited technical resources, in a location where stones (sarsens and bluestones) were relatively plentiful. They grouped the stones and used them in different parts of the monument, frequently changing their settings and design plans. Sadly, they never had enough stones, and had to rove over a greater and greater area in their hunt for boulders and monoliths. Eventually they just ran out of energy, and ran out of stones. So the monument was never completed, and was eventually abandoned.
That is, to my mind, a much more reasonable hypothesis and a much more compelling narrative. It may or may not be true, but I think it accords rather more closely with the evidence on the ground.
So -- back to the sarsens and the recent paper by Nash et al. The wording in the paper is quite cautious -- the authors say it is "most likely" that the sarsens -- or most of them -- came from West Woods. I can live with that wording, or something close to it. But to say that "we now know where the sarsens came from" (as Tim Darvill has done) is the sort of statement that would never get a PhD candidate through a doctorate viva, and it should not be acceptable on social media either. The very best we can say is that "Most of the sarsens at Stonehenge are closely matched geochemically, and of the sites examined by the researchers, the sarsens at West Woods provide the best match in the field." That isn't nit-picking -- it's a matter of scientific accuracy.
Partly this is a matter of sampling density. Only six sites have been sampled thus far in the "predicted sarsen collecting area" -- and there has to be much uncertainty about the accuracy of the recent provenancing work since many other sites are still to be investigated.
There is not much more that can be done at the moment, but as noted above, David Nash promises that there will be further research on Salisbury Plain if funding can be found, and we await with interest the forthcoming results.
West Woods and some of the sarsens on the woodland floor (photo: Steve Marshall).
2 comments:
Haven't yet got round to reading this MEGA Post. There seems to be a general stunned silence. Shall we all gently hummm Simon & Garfunkel's " The Sound of Silence"?
I always take silence as broad approval --- but I don't think I'm saying anything particularly new here........just drawing together some threads.
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