Bluestones and bell curves

by Edward Pegler on 25 March, 2010

How didn’t the Preseli bluestones get to Stonehenge? Ask your maths teacher.

I run the risk of posting on an often repeated topic, but here’s my opinion for what it’s worth.

The late Neolithic temple (or whatever) of Stonehenge, on Salisbury Plain, England, is constructed from two types of stones. These are the large ‘sarsens’ and the smaller ‘bluestones’.

The sarsens are large slabs of a kind of rock called silcrete. Silcrete forms at the bottom of a sandy soil profile under semi-arid conditions in landscapes where there is little erosion. Silcrete once covered much of southern England. Now it is limited to small pockets in North Wiltshire, such as Fyfield Down and Lockeridge Dene. Whilst a bit of a schlepp, Neolithic oxen and people probably could have dragged silcrete blocks the twenty miles from these locations to Stonehenge. Whether they did… ?

Bluestones are a series of varied rocks which have their origins, for the most part, in the Pembrokeshire peninsula of South Wales. They are largely igneous rocks (similar to lava) which have experienced a small amount of metamorphism due to their deep burial in the Earth before they were brought back to the surface by erosion in the last few million years.

How to move the stones

There have been untold words written about how these South Welsh igneous rocks got to Salisbury Plain. Two sensible methods have been put forward, each with variants.

The People Method: people quarried or collected the bluestones in Pembrokeshire, then brought them to Salisbury Plain by boat across the sea and pulled them the last part of the journey.

The Ice Sheet Method: the bluestones were broken off by an ice sheet (a kind of very large glacier) in a cold period around 400,000 years ago. As the ice sheet grew it spread to Salisbury Plain, or at least quite near. When the ice sheet melted it left the bluestones behind as what are known as glacial erratics.

For and Against

The arguments for the People Method are that the bluestones are similar in size and many are similar in composition. Most appear to have come from the Preseli Mountains and there is little evidence for other Welsh rocks on Salisbury plain.

The arguments for the Ice Sheet Method are that the stones are, in fact, quite diverse and even include a stone from far to the east. If there were an ice sheet, modelling suggests that it would be travelling in about the right direction to end up at Salisbury Plain. Finally, and most importantly, it’s an absolute bastard to carry a stone as big as a bluestone across the sea by boat, let alone drag it the last bit of the way to Salisbury Plain.

Now from a pure sense argument I’m very much inclined to support the Ice Sheet Method. It involves a simple natural process. It doesn’t ask people to do something that they haven’t done at almost any other stone circle, which is use non-local stone. It doesn’t demand the impossible or our poor feeble ancestors in their hide covered boats. Whilst the romantic in me loves the epic effort involved, the engineer wipes oily stains from his hands and says “Naa, not a chance, mate.”

But… something is niggling. It’s a small thing, but I can’t help thinking about it.

Neolithic Statistics

Glaciers and ice sheets are renowned for their lack of selectivity when it comes to stone collecting. Due to their bigness and force they can pick up any size of rock, from grain to boulder, on their frozen undersides. And they do. Also, because ice sheets and glaciers behave like one solid (well sort of solid) mass they can carry the small and the large with equal ease.

But when the ice sheet finally melts it dumps everything, from grain to boulder, in the same place. Unlike many other geological processes, ice sheets are astoundingly untidy. However, this jumble of rubble will tend fit tidily in one thing though – the statistical bell curve of size distribution by weight.

To explain: An ice sheet could pick up a really large boulder but it wouldn’t pick up many because their aren’t that many around. But with smaller rock chunks the ice sheet picks up more of them because there are more of them. So the ice sheet will be picking up thousands of tiny pebbles at the same time as it picks up one large boulder. So you get a graph of number of stones vs stone size like the one on the right.

On the other hand those millions of tiny pebbles, when you weigh them, don’t weigh that much. Medium sized stones are heavier but the largest boulders are much heavier still. So with that you get a graph of the weight of each stone versus its size, as shown again on the right.

You can combine this information by calculating the total weights of all the sizes of stones collected. This involves multiplying the number of stones of each size by the average weight of each stone of any size. What you get is the bell curve graph of the weight of all the stones in one size fraction vs stone size like that shown here.

Ice sheets lose

“So what?” I hear you say. Well it’s simple. If you plot the distribution of all the bluestones or related stones on Salisbury plain it would have one big spike. This represents the large, and relatively similar in size, bluestones of Stonehenge. There may also be a couple of small spikes for those smaller stones found in local burial sites. Importantly, it doesn’t look like the ice sheet dump distribution.

So perhaps someone cleared the rest of the bluestones away. There are two clear arguments against this.

If the bluestones were the biggest stones deposited by the ice sheet (A on the bell curve) then there should be absolutely thousands of smaller bluestones lying around. Their aren’t. Even if farmers had subsequently collected the medium size stones for use in walls and houses (and there’s no evidence of this) there would still be masses of pebbles lying around. Their aren’t.

Alternatively, if the bluestones were the “average” stone size (B on the bell curve), then there should be much larger stones lying around. There aren’t. Perhaps the Stonehenge builders chopped these larger stones into bits. Maybe. Whatever, even in this cas you’d still find a large number of pebbles lying around. You don’t.

Notably, the Neolithic long barrows of Salisbury Plain, which are older than Stonehenge, do not include one single one of these theoretical, very large bluestone boulders in their construction. For that matter they include only one recorded “Welsh” stone, the small boulder of Boles Barrow. Indeed, for that matter, they don’t include any sarsens either (these lines modified slightly 17th April 2010, due to a comment which suggested they needed clarification).

In North Wiltshire and the Coltswolds, similar long barrows always used local stone in their construction if it was available. It seems odd that the builders of Salisbury Plain perversely chose not to use the handy bluestones of Salisbury Plain. But that’s probably because they weren’t there yet.

People win… at least partly

Reluctant as I am to say it, it’s time to give up on the idea of a glacier reaching Salisbury Plain carrying its bluestone bounty. People must have been involved in getting the stones to Salisbury Plain. I have no idea how they did it but just fact that they did makes the people of Neolithic Britain pretty smart (and unbelievably determined), in my opinion.

But whether an ice sheet carried carried the stones part of the way from Pembrokeshire, maybe to the Somerset plain… hmm. That’s another argument that I’ll leave alone for the moment.

References

Atkinson, R.J.C. 1956 Stonehenge, Pelican, pp221

Burl, A. 2006 A brief history of Stonehenge, Robinson, pp368

John, B. 2008 The Bluestone Enigma – Stonehenge, Preseli and the Ice Age, Greencroft, pp160

Acknowledgements

{ 23 comments… read them below or add one }

Brian John June 10, 2010 at 4:27 pm

Ned

Email me please. I have a PDF for you.

Cheers

Brian

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Brian John June 10, 2010 at 10:47 am

Interesting discussion, folks! In case anybody is interested, I have recently put a lot of new material onto my blog………
All the best

Brian

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Edward Pegler June 10, 2010 at 3:37 pm

Indeed I encourage anybody to go and have a look at Brian’s highly informative site on this topic. He’s compiling much data on early glaciations in the south west.

Ned

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eirasys May 21, 2010 at 1:45 am

Read and tell me your opinion

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Edward Pegler May 21, 2010 at 9:10 pm

Dear João

I am flattered that you think my opinion is worth having. What an amazing piece of work to take in! My initial reaction is instantly one of disbelief but I will have a look with an open mind. Bear in mind that it looks like you’re the better engineer.

Ned

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João May 23, 2010 at 10:00 am

Thanks, your opinion is in fact quite important. Blogs like this are very useful to look at problems we want to solve from different perspectives. Sometimes I also disbelif it! I’ve recently added information about ‘local’ water level, google earth is usefull to visualize the idea. What can make people move large stones? Could be cultural ideals (like pyramids) or a true need if life was in risk. The first one seems unlikely. There are too many stone circles whithout building quality, people did’t invest much effort in finish quality, except for stonehenge. So it surely wasn’t something cultural, build to preserve, but rather a tool, with a specific purpose. The purpose would be saving lifes and society goods while water took their lands.

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Edward Pegler May 24, 2010 at 3:18 pm

I think you’re idea is fascinating and incredibly inventive. Certainly, the people involved would have needed extremely strong materials, at the same time rigid enough not to bend but also not brittle enough to break. I presume you’re thinking of wood. Have you done calculations on exactly what thickness of wood could produce a rigid, flattened hoop of the right scale capable of supporting the varying forces of gravity, the oxen and the load itself on the various bits of the hoop?

One concern, as shown by your very fine video, is that many of the stones in Stonehenge were not dug with sufficient foundations to stop them being pushed over by these same forces, even allowing for the addition of a bracing mortice and tenon capstone around the ring. This would need more reinforcement.

I also would not overextend your theory to try to take in all other mysteries of the region or, indeed, other regions. There are plenty of buildings in history built to extraordinary designs for entirely cultural reasons. Just look at the layout of many Hindu temples in India, built to specifications that have no functional purpose.

However, the major question is why people would have built such a ‘crane’? Cranes are generally used for building or for bulk cargo transport these days. Stonehenge itself is such a building, but it could not have been built using itself (although I acknowledge that you argue for earlier versions of the same kind of device on the site). Once Stonehenge was built there doesn’t seem to have been more building of this kind here. Bulk cargo transport is unlikely, due to complete the lack of evidence for its existence at the time.

An additional point, related to the last, is that Stonehenge was not surrounded by water or next to rivers when it was built during the third millennium. If anything, environmental evidence shows that third millennium Britain was experiencing a dry phase where water table levels were similar to or lower than they are today. Where settlements are found they are in the present day river valleys, tens of metres below the elevation of Stonehenge.

Overall what I like about your idea is that it is realistic, in the sense that the material capabilities may well have existed in Britain at the time. What I don’t like, although I’m not saying you’re wrong, is that I can see no need for it. To me the building of Stonehenge is no different from many other impressive monuments built for people with huge egos. I wish I believed that its purpose was more than that.

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João May 25, 2010 at 11:33 am

I agree, someway inventive, like many others, its just a theory. Most of the information was collected on internet. The structure resistence can only be obtained by trial and error while building one in wood. It is subjected to high tangencial forces, rather than axial forces, so no need for big timber thickness. About overextend the theory, it can not be applied to all circles we see, must be studied one by one, no globalization in that time! The water is one of the last updates to the site, I see no proves of that water level anywhere in the net at 3000BC maybe before of that.. or no water at all, no idea, but when you try it on google earth there are some common features like position of the circles and orientation to each others that match terrain elevations. Click the kmz file a analize it in several other places. The need for such cranes would be the transport of something I don’t know! But the fact is that the stones are there, what was the need to move and erect those very big stones?, whithout functional purpose? Only cultural? Too much effort for stonehenge and so little for a lot of small stone circles all over europe. Hope someone else solves all those mysteries..

John May 16, 2010 at 9:11 pm

Hello Constantinos, Ned,

If we accept the argument that the “Stonehenge Layer” is derived from a glacial deposition then how would we explain the latest posting on Brian John’s (The Bluestone Enigma) blog:

“Rob Ixer has kindly confirmed that after studying around 7,000 fragments from the Stonehenge neighbourhood, he can say with some certainty that some of the bluestone monoliths are of rock types that are NOT represented in the “Stonehenge layer” or in the litter of fragments in the soil horizons; and that some frequently occurring non-dolerite rock fragments (ie rhyolites, ashes and sandstones) found in the “litter” are not represented in the 43 known bluestone monoliths / stumps known in the stone monument.”

An anonymous (Ixer?) commentor adds: “I have recognised no altar stone material in the Stonehenge layer -even if I have mis-identified some of the rare non-Lower Palaeozoic sst and they ARE altar stone then their numbers are very very small. …… most of the Stonehenge layer comprises sarsens and preselite plus the other types of bluestones it is these that are mis-matched.
BUT THERE ARE ONLY 4 VOLCANIC ORTHOSTATS WITH PROPER PETROGRAPHY BASED ON VERY SMALL SAMPLES, COMPARED WITH 1000S OF VOLCANIC DEBITAGE.”

We must accept that these comments are very fresh and must await a fuller, scientific report, however, the early indications from these comments is that if the Stonehenge Layer IS a glacial assemblage and the 4 volcanic stones do not feature prominently in it then they must have been introduced by another agent – i.e. not ice.

Source: http://brian-mountainman.blogspot.com/2010/05/bluestone-fragments-plot-thickens.html

Regards,
John

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Edward Pegler May 18, 2010 at 7:44 pm

Dear John and everyone.

Thanks for your very interesting info. As for any conclusions, I’ll wait and see. It’s an interesting idea that the ‘Stonehenge layer’ is ice derived. Unless I had more info I’d be reluctant to agree though.

One obvious point is that if, say, the remaining bluestones represent only part of the original collection then other stones of rhyolitic, tuff or sandstone composition could have been there once but are now gone, only their chips telling of their former presence. Likewise, not all of the bluestones might have been worked, so may not be represented in the layer. All this is speculative, however, and much depends on the shapes of the fragments in the layer, whether they show signs of working and, indeed but unlikely, whether some can be fitted together.

But perhaps the most important point is that the ‘Stonehenge layer’ is known to postdate the earthwork around Stonehenge, which has been dated to around the end of the 4th millennium BC. As the relevant ice sheet (the Anglian/Elsterian) is supposed to date to about 400,000 ago and even the most recent glaciation is from at least 12,000 years ago, this is not a glacial deposit.

Watch a space somewhere (e.g. Brian John’s) for considerably better info.

love Ned

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Constantinos Ragazas May 13, 2010 at 4:36 pm

Dear Ned,

Thank you for your reply. I will consider your comments carefully, as I always do. But just one point to clarify my position. You say that I believe,” earth and stone circles and alignments are the result of glacial moraine distributions”. I need to clarify this. The stone alignments were not deposited in such positions by glaciers, as is the case with moraines. Rather, these were formed by local people (perhaps very early Paleolithic people) by pushing these huge stones on the ice surface over the ice edge (perhaps as a game). Thus, what we now see as these stone alignments are the receding edge of the ice sheet locally in that area. The stone alignments are the ‘written record’ by Paleolithic man that records these geological events. This totally explains their alignment and configuration. That’s why they are all near parallel and near evenly spaced and why they are all running in the same general direction throughout that area. Something that no other theory can explain.

As far as glaciation reaching that part of Europe. Are you saying that Europe was never covered with ice? I am not making any claims as to when these stone alignments were made, just that ice played such a role in making them. Since there is really no skill or social organization needed to push existing stones over an ice edge, these could even have been made by monkeys! So unless you are claiming that Brittany was never covered by ice, my explanation stands.

You write,

“Why deny that people just two or three thousand years before (at the same time as the Pyramids) could make structures of similar scale? “

There are many reasons why I find this not credible. I will briefly list a few.

1)The builders of pyramids may have stopped building pyramids but they kept on building nonetheless. They have left behind much evidence of their civilization and existence (including written records). None exists for the builders of these stone alignments, except these stone alignments.
2)The builders of the pyramids had a very specific purpose for these. There is no conceivable purpose for these stone alignments. If they were to serve as some religious function, that would require social organization, artifacts and symbols that would be needed to sustain such fervent religious beliefs from one generation to the next. No such evident exists.
3)The builders of the pyramids lived in an area that was rich and prosperous. Their geographical conditions enabled them to sustain life while giving them leisure time to pursue and build pyramids (and other structures). The living conditions for the Neolithic Europeans were very severe. All their resources and time was spend in just sustaining life from season to season. It’s not conceivable that they would divert their meager energies and resources to pursue such very difficult and demanding tasks of moving very heavy stones over uneven terrain for dubious purpose.
4)How the pyramids were build and how the heavy stones were transported is still an unsolved mystery. You can’t use one unsolved mystery to solve another.

Finally, it will be very helpful to me if you could answer my question regarding the Stonehenge Layer. How is this layer different from other parts of the surrounding area? If this concentration of stone fragments is distinct from the plain surrounding it, then my theory that an ice sheet covered Salisbury Plain during the building of Stonehenge would explain the Stonehenge Layer. It will also explain the lack of typical stone size distribution associated with glacial moraines etc. Certainly such deposits will not happen when the land is covered with ice and when the ice melts in place. The surface runoff water would carry such stone debris to rivers and pools (eg Stonehenge) and deposit these there in greater concentration; leaving all the surrounding countryside free of these when the ‘local ice’ fully melts ‘in place’ and without ‘ice flow’.

PS. In the interest of a common search for truth and diverse views on Stonehenge could you include a link to my paper in your blog site? “The un-Henging of Stonehenge”

http://knol.google.com/k/constantinos-ragazas/the-un-henging-of-stonehenge/ql47o1qdr604/16#

Best,

Constantinos Ragazas

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Edward Pegler May 14, 2010 at 10:43 am

Dear Constantinos

Yes, I am saying that in the last 500 million years that much of Europe (from southernmost England downward, including Cornwall and Brittany, but not the Alps) has been free of glacial ice. The last glaciation to cover Europe in ice happened before life had crawled out of the oceans.

As for the magnificence of the Egyptian civilisation I do not deny it and it was undoubtedly vastly more sophisticated in many ways to that of northern Europe. However, what you don’t see in northern Europe are the remains of any possible buildings, boats and carvings made out of wood. All of these have now rotted away in the damp maritime climate. Due to natural processes of landscape erosion there is literally no evidence for them. Egyptians, being short of wood, frequently used stone. Additionally, Egypt, being dry, preserves much of its ancient wood.

The concentration in a surface layer of broken and chipped fragments around Stonehenge is, logically, thought to be debitage (bits chipped off) during the shaping of the Stonehenge sarsens and bluestones. Much of it occurs on the high ground around Stonehenge, not in the valleys. Evidence for the shaping of the stones is easy to find, examples being the mortice and tenon joints in both sarsens and bluestones.

I hope the link in your post will suffice. I cannot provide another link in the blogroll as I don’t think that you have evidence to make your case.

regards Ned

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Constantinos Ragazas May 14, 2010 at 3:58 pm

Dear Ned,

Thank you for your response. I do appreciate your consideration of my article. I am sorry to hear that you don’t think it rises to the level of a blogroll link in your site. But that’s your prerogative and judgment and I respect that.

In the interest of accuracy, however, I should make a correction to an important point that you raised as evidence in opposition to my theory. In regards to the stone alignments you said,

“There are many alignments (such as the Dorset Cursus, Offa’s Dyke, the Antonine Wall) which run against glacial flow directions.”

This is as it should be! If according to my theory these stone alignments trace the ice edge, this direction would certainly be against and perpendicular to the ‘glacial flow direction’. This evidence supports my theory, not contradict it.

As for the last glaciation of Europe, are you saying that for the last 500 million years there existed no ice sheets in Southern UK and in Brittany? That there were no local ice sheets, like with stagnant enclosed bodies of water in low lying areas? What about the ‘glaciation stripes’ and permafrost evidence discovered at Stonehenge? You may be right when you say that glaciation covered Europe 500 million years ago and even earlier, but could still be wrong that there were no local ice cover in Salisbury Plain more recently. That there were no ‘ice men’ but only ‘stone men’ in Europe.

As for the Stonehenge Layer, you write,

“The concentration in a surface layer of broken and chipped fragments around Stonehenge is, logically, thought to be debitage (bits chipped off) during the shaping of the Stonehenge sarsens and bluestones.”

From the Atkinson photos it is clear that this ‘debitage’ is varied from chipped to rounded pebbles and is uniformly mixed into the top soil throughout that layer. If these stone fragments are the result of work done on the huge stones, wont you expect this ‘debitage’ to be concentrated around these sarsen and bluestones and not scattered uniformly throughout the Stonehenge area? And shouldn’t there be a distinct layer of such chipped stones rather than the existing uniformly mixed gravel and pebbles with top soil?

I know you have a different view on this Ned, but intellectual integrity and commitment to truth compels me to make these points.

Constantinos

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Constantinos Ragazas May 10, 2010 at 8:03 pm

Dear Edward,

Thank you for your blog. I value this public space to post thoughts about Stonehenge. My name is Constantinos Ragazas. I am a retired math teacher with a lifetime interest on Stonehenge and other archeological enigmas, including the head stones of Easter Island and the Giza pyramids. I have written an article, “The un-Henging of Stonehenge”, offering a different explanation to the many puzzling enigmas of Stonehenge. It is related to Brian John’s idea of glacier transport, but goes further to explain how ice may account for the construction of Stonehenge.

I have a couple of questions:

How is the composition of The Stonehenge Layer of small chipped rock, gravel and pebbles, uniformly mixed into the top soil, differ from the composition of the top soil in other parts of Salisbury Plain? And if there is a distinct difference that identifies the Stonehenge Layer, what explains this formation?

Also, what current theory accounts for the many stone alignments throughout Brittany and southern UK?

The article can be found at the following URL:
http://knol.google.com/k/constantinos-ragazas/the-un-henging-of-stonehenge/ql47o1qdr604/16#

Regards,

Constantinos

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Edward Pegler May 10, 2010 at 8:15 pm

Dear Constantinos

Good to hear from you. I shall get back to you properly when I’ve had a look at your pdf. On first glance I’m inclined to disagree (as you’d probably guessed) but it’s not fair to be too hasty. Expect a second reply sometime soon.

Ned

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Edward Pegler May 13, 2010 at 10:20 am

Dear Constantinos
Having looked at your work what you say (i.e. that many earth and stone circles and alignments are the result of glacial moraine distributions) seems, to me, unlikely. There is, perhaps, an argument to be made for the glaciation of Salisbury Plain. However, there is no evidence that even the greatest of Quaternary Glaciations (the Elsterian/Anglian http://www.qpg.geog.cam.ac.uk/research/projects/nweurorivers/elsteriananglian.html) ever reached much of Cornwall and Brittany, where many stone alignments also exist. The very ancient soil profiles of these areas show no evidence of glaciation either.
There are many alignments (such as the Dorset Cursus, Offa’s Dyke, the Antonine Wall) which run against glacial flow directions. People must have dug out and constructed all of these things at different times. No-one denies Offa’s Dyke or the Antonine Wall are manmade. Why deny that people just two or three thousand years before (at the same time as the Pyramids) could make structures of similar scale?
It’s a wonderful and rare thing to come up with ideas but most of them will be wrong (most of mine probably are) The only thing I can recommend is that you keep aquiring more data. I believe that what you find will turn out to be much more interesting and satisfying than your current theory.

kind regards
Ned

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Brian John May 5, 2010 at 7:55 pm

Thanks Ned — yes, these are interesting points. There is a lot still to be done on permafrost and periglacial processes on Salisbury Plain — but I’m not sure that solifluction / other processes will have “filtered out” the big monoliths and left them exposed on the upper slopes and interfluves while all the finer material will have moved down into the valleys and hollows. But sure, the idea needs some further thought……

Geoff Kellaway had an interesting idea about the lack of monoliths in the long barrows of Salisbury Plain — he thought that the builders of Stonehenge had “robbed” all of them from these earlier structures because they wanted them for their wacky project. That’s an attractive idea, but presumably the robbing of stones from these barrows will have left traces, and these will have been picked up on by the early archaeologists. I don’t know the local archaeology well enough to know the score on this….

Clay with flints — I know there is a lot of dispute about this. My point was that it is a far from homogenous deposit, and what is described as CWF in one place appears to be rather different from the CWG somewhere else. I still think that SOME of the CWF deposits sound to me like till remnants, and when I looked at some exposures many years ago they looked like the remnants of the “Northern Drift” (also open to interpretation) in the Oxford region.

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Brian John April 18, 2010 at 6:59 am

Good to discuss this, Ned! I think your basis problem is that you have assumes the EVERYTHING IS ERODED, TRANSPORTED AND DUMPED TOGETHER when an area is overridden by glacier ice. That may be so in the grand scheme of things — for example, a gigantic glacial trough is eroded, leading one to conclude that all of the bedrock that was there before is not there any longer, and must therefore have been taken and dumped somewhere else. But actually when you look in detail you see that erosion, entrainment, transport and deposition are all actually very selective, depending on the mechanics involved. So if shearing is involved, you get huge blocks of rock caught up in the glacier, and if abrasion is involved you may get sand, silt and clay fractions carried away, with very little in the way of pebbles and boulders. That is why you get huge variations in the nature of glacial deposits. In some cases a fine-grained till with just a few entrained stones, in some cases “free boulders” or erratics, with virtually no matrix of finer sediments, and in other cases (if there has been flushing by water) virtually all sand and gravel with hardly any silt and clay and (at the other end of the scale) hardly any stones and boulders either. So while all of the rock in a glacial trough may have been removed, it is carried away in different ways, and “redistributed” into different parts of the deposition zone down-glacier. If you then try to make a bell curve of the sediments in any one area, you will end up with bimodal or even multimodal spikes.

I did this sort of work 50 years ago as a research student, and while techniques may have changed between now and then, the principles of sedimentology haven’t! OK?

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Edward Pegler April 25, 2010 at 5:31 pm

Dear Brian

I feel that some kind of extended comment is necessary. As I understand it, your main criticisms of the post are the following: a) that glacial deposits do not need to contain finer grain sizes, due to the processes of glacial meltwater reworking and redistribution of finer grains (mud through to gravel). OK. b) Sorting of glacial deposits can be good and that they can also be bimodal (having two peaks of clast size). Yes, I have no problem with them being bimodal. I don’t believe that the coarser sediment fraction can ever be well sorted though.

However, regardless of whether processes of glacial outwash entrained finer grains or whatever, one of the most important arguments in your favour is that the deposit, being from the Anglian (Elsterian) glaciation, 400,000 years ago, is likely to have been extensively reworked by natural processes.

These are my thoughts:

Due to the nature of chalklands (even at times of permafrost), the sediments moved by processes of erosion will be size fractions less than about fifteen centimetres (at an estimate). This will leave in place anything coarser, including things the size of bluestones.

My point, as made in the post, is that when significant numbers of people did establish themselves in ancient Britain around 4000 BC, one of their early acts was to build mausoleums for their dead, the so called Long Barrows, Chambered Cairns etc. In every place in Britain where large stones were freely available they built their mausoleums out of these large stones. In north Wiltshire local sarsens were used where possible (e.g. Wayland’s Smithy and West Kennet) but where stones were absent they were not used (e.g. Beckhampton).

However, in Salisbury Plain the 56 (approximately) long barrows were built without stone, with one exception (Boles Barrow, which contained ten stones, one of which is thought to be non-local dolerite or ‘bluestone’ and the rest were sarsens). To me and to many others this suggests the general absence of large stones (whether ‘bluestones’ or ‘sarsens’) on the plain at this time. Yet by the time that the stone part of Stonehenge was being built (between 2900 and 2300BC, depending on who you believe) there were now a large number of good quality, similar sized bluestones to pick from in the Stonehenge area. Possibly the earlier long barrow builders ignored these but this seems unlikely to me. It instead suggests that the almost all of these stones came from elsewhere.

Additionally, even though glacial till deposition may have been patchy (as you suggest in your book) some of it will have survived. It is possible, for example, to see the extensive survival of Anglian till deposits in Norfolk.

You argue in your book that the ‘Clay with Flints’, so extensive across much of the Wiltshire chalkland, was that till. However, the process which formed this layer is unlikely to have been glacial. The predominance of local flint (hence the name) in this layer is due to its local formation. Sub-tropical (some say glacial) acidic weathering of the landscape in the late Tertiary dissolved perhaps tens to hundreds of metres of chalk leaving only the insoluble residues, flint, clay and silt. This is why these deposits are confined to the chalk. If they were tills they would also be distributed over other soil types. If it were a locally formed till then it would include fragments of chalk as well.

As stated before, reading your book made the case for ice-transported bluestones almost perfectly, but I will still not believe it until the points above have been met and dealt with. Do that and I’m your fan.

Ned

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Brian John April 16, 2010 at 6:18 pm

Have looked at this with interest, Ned. But I’m sorry to say that you have got it entirely wrong. Your assumptions are fundamentally flawed. Please have a look at my post here:
http://brian-mountainman.blogspot.com/
Best wishes

Brian

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Edward Pegler April 17, 2010 at 5:41 pm

Dear Brian

Thanks for the reply. I’ll look into what you say and get back to you here and on your blog, if that’s alright. As for the boles barrow stone I was not clear in what I said and have clarified this in the post. I am genuinely unbiased on this, and will let you know if I convince myself that I’m wrong. However, I still feel that one stone in a long barrow does not make evidence for a glacier, but perhaps only for contact with Wales dating back to the 4th millennium BC.

Having said all that, personally, I’d much rather believe the glacial story, especially after the amusing account you gave of the recent bluestone journey reconstruction.

regards
Ned

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Michael Bott April 2, 2010 at 12:22 pm

Hello Edward

I am the director/producer of the film ‘Standing with Stones’ and I run a general blog about things megalithic/Neolithic/Bronze Age in order to help promote the film at http://standingstones.tv

The bluestones are, of course, mentioned in the film and there is a short section filmed at the Gors Fawr stone circle in sight of the Preselis. In the film, my presenter presents the theory that the Stonehenge bluestones came from the Preselis as fact – however, I am aware that the debate lingers on.

I was looking on the web for the evidence for and against the human transportation theory and came across your rather compelling essay that, in my view, seems to tip the scales of probability rather a long way in favour of the anthropogenic theory. Could I please have your permission to reproduce your article on the blog? I think it would be a very welcome read for many of my visitors, of which I have over 5,000 every month.

Best wishes

Michael Bott

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Edward Pegler April 3, 2010 at 6:59 pm

Dear Michael

Delighted. If you could include a link back somewhere that would also be much appreciated.

Ned

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