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Monday, 16 April 2012

The Stonehenge Sandstone Mystery (1)

 Two images from the Heddle Collection -- acknowledgements to Glasgow University and the Open University, on whose web pages these are published.  They are both thin sections taken from an Altar Stone sample, interpreted as "arkosic sandstone containing rounded and angular clasts of quartz, plagioclase feldspar and iron oxides".  The upper image is under plane polarised light, and the lower one (coloured) is under crossed polars -- the orange and blue colours of some crystals might be anomalous or confusing, because of the thickness of the cut section of rock.

The Stonehenge Sandstone Mystery (1) -- The Altar Stone


Since my previous posts about the Heddle Collection of Stonehenge slides at the Hunterian Museum in Glasgow, I can report that there is no skulduggery going on!  Dr John Faithfull has been in touch, and he tells me that  the "missing" slides to which I referred are not missing at all, but are in the possession of the Open University and / or the National Museum of Wales,  where geologists are presumably examining them carefully as we speak.

He also referred me to this Open University site, where more information may be found:

http://www.open.ac.uk/earth-research/tindle/AGT/AGT_Home_2010/Stonehenge-HeddleMenu.html

Leaving the matter of the strange "Altar Stone" sample that appears to be made of igneous rather than sedimentary material, let's home in on the sandstone samples. We are lucky to have a keynote paper to guide us here -- "A detailed re-examination of the petrography of the Altar Stone and other non-sarsen sandstones from Stonehenge as a guide to their provenance," by R.A. Ixer and P. Turner, published in Wiltshire Archaeological and Natural History Magazine, 99 (2006), pp 1-9. The authors describe the Altar Stone as "a purplish-green micaceous sandstone" which appears to have originated on the ORS Senni Beds of South Wales. (They argue very convincingly that the place of origin was NOT the Cosheston Beds on the shores of Milford Haven, as assumed by archaeologists for many years.) Here is a part of their description of the rock examined (from a slide held in Salisbury Museum): " Microscopically the rock is a very fine- to fine-grained, well-sorted sandstone with a mean grain size of 0.13mm and a maximum grain size of approximately 0.32mm. The clastic grains are angular to subrounded and the modal group is subangular..............The rock has a homogeneous fabric but bedding is observed by thin, less than 0.5mm wide, opaque mineral-dominated, heavy mineral laminae.......There is very little detrital, interstitial material. Authigenic kaolinite is locally present but the main matrix is a pervasive carbonate cement........" There is much more detail in the paper.


Here is one of the slides examined by the authors:


Compare this with the monochrome slide at the top of this post.  Here is another of their slides:


Compare this with the coloured slide above.  It's not easy to draw conclusions, because I do not have a note of the magnifications involved in all of these slides, or of other factors that might make the samples look more different than they really are!  I need some geological advice here........... since when I was in Oxford I was the world's worst mineralogy student.  But I have done a little trick and have put the coloured Heddle slide together with the Ixer / Turner slide, and this is what we come up with:
The larger image is the one from the Heddle collection, and the smaller one (reduced in dimensions so that the grain sizes are more or less the same) is the Ixer / Turner slide.

Could these samples have come from the same fallen monolith (namely the Altar Stone numbered as stonehenge 80)?  To me, they look different, but what I do not know is the range of variation in grain sizes, mineral types and structures that we might expect in a large boulder weighing about 6 tonnes.

If there are any geologists out there, your comments will be very welcome...... 


36 comments:

Anonymous said...

I do not wish to say too much about the sandstones of Stonehenge. The I and T paper says much of what I think.
The Heddle thin sections are a puzzle.
I have not seen them in the flesh and photomicrographs, as here, are very limited in what they can do. As I have said in print elsewhere when discussing suspect bluestones that like St Thomas I need proof –that of my own eyes and experience before pronouncing-.
The IPG Altar Stone – (it is normally housed in Taunton not Salisbury,) described by Pete Turner and Rob Ixer, - has a carbonate cement. It is impossible for me to say whether the Heddle one does-the pics are not good enough –the problem being the material rather than the photographer.
It is a pity that the two Heddle ‘altar Stone’ sections are compromised by the one being an obvious volcanic.
If there were any helpful correspondence that would help
The truth is very simple the Altar stone should be freshly sampled and polished thin sections made so the total petrography can be described. The fun would then start trying to find a match in the field.
At present I think the Heddle altar stone is a distraction-it obviously needs describing alongside the IPG section if they are similar well and good if not then ………………….

Fun but a side aisle not the main concourse.

Of course this being a science/myth blog perhaps if they are different they belong to the ‘two’ altar stones.
MoA

Anonymous said...

Don't for get the Slaughter Stone while your resampling as it would have come from the same area!!

Annie O.

Anonymous said...

Annie, my dear, stick to knitting... unless your comment be a wind-up.
Whilst the Altar stone is very probably a Welsh Devonian cornstone (a calcrete)the Slaughter Stone is a Wessex Tertiary sarsen-a silcrete.
So the ONLY way they could have come from the same area (Bizarre idea. You are not our banned Greek Friend still celebrating Easter?, are you?if yes Christos Anesti!)is if Brian is correct and the glaciers dumped the cornstone in Wessex.
Myris.

BRIAN JOHN said...

Myris -- no sexist comments please. Annie has my permission to kick you with her bovver boots if she wants. We all make mistakes...

Anonymous said...

Myris,

Why would your self-banned Greek Friend remotely care if the two stones came from the same area or not? Either way it's one and the same! Unless if one of these came from the South.

I trust on science (and not myth) to settle such questions of provenance. And I'm amused with new 'made up stories' to explain the 'facts on the ground'.

Your self-banned Greek Friend –
Alithos Anesti!

Anonymous said...

Myris

Just responding to a remark made by Brian last month to Rob Langdon: "I agree that there is even more interest in the "other sandstones" at Stonehenge -- and I hope there will be news of those shortly, when Rob and Richard and their colleagues have done their work."

As for the patronising remarks it clearly shows that you are an 'ageing' twat!

Annie O.

BRIAN JOHN said...

Language please, all you good people. No more abuse or swearing if you please -- I'll just spam any further use of Ango-Saxon words which I find offensive.

Anonymous said...

Annie I am sorry. You are not who I thought you were (namely Mr P winding me up).
I only patronise friends who will respond in kind(others obviously do not count)so this was an error on my part.
Like sin and the sinner it is ignorance rather than its author that should be eternally detested.
But as it was such an odd thing for anyone to say, so below the common stndard of knowledge on this board that I entered into the joke (as even dear old Atkinson correctly identified the sarsens).
Annie listen though Knitting is the new petrography and old age (always defined as 20 years older than you are)better than death- possibly.
Archaeomyris of Alexandria.

Anonymous said...

Eeeh, so esoteric, but it's a reight good read on 'ere, aint it?? Thank goodness I used to journo for T'Guardian.


Michael Parkinson

chris johnson said...

These pictures are rather beautiful. I hope the academics can emerge from their sniper silos long enough to venture an interesting opinion or even an hypothesis. It should not be too difficult while Brian permits these anonymous posts.

"The fun starts by finding a match in the field" - well, maybe for some. For me the fun starts by learning more about why these particular stones were chosen for inclusion in the monuments. I suppose Brian would argue that they were just any old stone of approximately the right size that happened to be lying about in the vicinity. He might even be right.

A layman like myself might learn more by understanding what might be special about these stones - wherever they were collected. Was it the physical beauty in an unweathered and even polished state? Is it an electro-magnetic property or acoustics? Even if there is nothing special then we learn something too.

All this talk about Greeks bothers me. The one Greek who bothered me with his specious sophistry is no longer with us, thankfully. The other Greek references I do not get, even after following this blog for several months. Perhaps I am too stupid.

Anonymous said...

Chris,

Good to know even in my absence you feel my presence!

What you find beautiful in these slides of these stones is what you see under the microscope! Are you suggesting (like Robert would like to suggest) prehistoric people could see deeply into stones?

So now not only do we know the intentionality of people who left no records behind, but also what they saw in the stones.

Kostas

Phil Morgan said...

Hello Myris,
If you thought it was I, (Mr. P.)winding you up, then I regret to inform you that you were mistaken, for we have had sufficient meetings and correspondence for you to teach even me, the difference between Welsh Devonian and Wessex Tertiary.

Hello Chris,
Having consulted my mother-in-law, who has been around since the Neolithic period, the latest theory is that the original bluestone circle, consisting of 55 stones of various pedigree, were set in a circle of 27m diameter on Foeldrygarn; with Foeldrygarn being the centre of power, and the residence of the Chief of Wales.

The stones came from both Carn Meini and Pont Saeson, with Pont Saeson being the dwelling place of the working people and their families.

The guiding principle was that individuals, or family groups, were allowed to donate stones to the circle at the rate of one stone per person. The higher the status of the person, the better the quality of the stone, whether it be in durability, appearence or both. Magical/healing powers played no part in the gift, it was purely prestige.

The Chief of Wales, whose name was Idris, controlled the territory from Pembrokeshire to the River Severn. (Correct - it wasn't called Pembrokeshire in those days). He decided to give the whole Foeldrygarn stone circle to his counterpart who controlled the Wessex area. The stones were transferred in a single exercise, with the people, or families, who originally donated the stones being responsible for the transport of their particular gifts. The settings of the stones in the original circle were respected when re-erected at Stonehenge.

A thourough search beneath the perimeter of the centre cairn at Foeldrygarn will expose the stone-holes of the original circle.

One of the rules that helped maintain peace and order in the land was as follows.
If a stone/s was removed from the ground in one area, and then gifted and placed in the ground in another area, a reciprocal gift of stone had to be made to maintain the 'natural balance' of the land.
One stone out replaced by one stone in.

To repay such a prestigious gift the Chief of the Wessex area gave a long term, (perhaps 20 years), supply of flint to the Chief of Wales, thus restoring the natural balance of the land.

That's all for now, more of this gripping tale if Brian allows?

Cheers,

Phil

BRIAN JOHN said...

Phil -- sounds like an interesting mother-in-law you have there? Since she has, as you say, been around since the Neolithic, might she have studied under HH Thomas?

Phil M. said...

Brian,
Close, but no coconut, for it is said that not only H H Thomas, but also Cunnington and Stukeley studied under her.

Rather than 'interesting' I would describe my mother-in-law as frightening.

Phil

chris johnson said...

Hi Phil,
thanks for making me grin broadly late on a Friday evening after a busy week. I do love a good story.

BRIAN JOHN said...

You are not alone, Chris, in loving a good story. That is why our dearly beloved professors have got away with all this story-telling for so long.......

Anonymous said...

Phil

Long ago, in the mists of time, I worked for 3 Chiefs in Wales; 2 of the 3 each thought they possessed gifts in spatial planning. Coincidence with Idris?

Many leaders are said to be autocratic/ borderline psychotic. Gets the job done, mind.

Phil M. said...

Dear Anon,
That's an interesting thought.
Coincidence = Idris was expert in spatial planning but I shall consult my mother-in-law for confirmation.

Without leadership most enterprises/communities collapse into a shambles, fortunately for the ancient people, Idris, and his counterpart in England, were able to direct operations through respect, as opposed to management by fear or financial reward which resulted in harmony and peaceful competition; unlike the present where many of our leaders suffer from the well known problem of having "a head full of bubbles".

In Neolithic times this complaint was treated by immersing the sufferer in stagnant bog water and forcing the poor person to completely exhale.
An accurate count was kept of the resulting bubbles, and when the magic number of 42,(which I am reliably informed is the answer to the secret of the Universe), was reached, the patient was removed from beneath the bog.
If the patient failed to reach 42 he was re-immersed. However, the person keeping count sometimes cheated just to prolong the discomfort. It was from this work that the present day name for the snake originated, for he was known as a 'Puff Adder'.

Phil

chris johnson said...

The main problem in this debate is that people do not pay attention to detail.

So where did the glaciers deposit the stones and where and how might we look for further evidence? Brian has now given a hypothesis but how we might test this. It is a mystery to me.

If the route was overland by human agency, where is a plausible route? In my enquiry I have arrived a few mile south of Crymych as a starting point, but how did they get to Camarthen? I have an idea and I will test this on the ground in the next two weeks, but there are a lot of people a lot smarter than I.

Today I am very curious why there are no pre-historic remains at Nevern Castle despite its apparent alignment. Can anybody throw some opinion my way?

Where is the second altar stone?

Anonymous said...

You learn something new every day, Bluebottle.


Eccles [circa 1956]

chris johnson said...

Yes I do try to learn something every day Eccles. And you?

Not having been listening to "wireless" in 1956 it is of course possible I am not fully cognizant of your wit. Perhaps you have to spell your message out for the benefit of us younger folk.

Meanwhile perhaps you should get your zimmer out of your garage and look for some evidence!

BRIAN JOHN said...

What a hotbed of erudition this site is! Discussion ranging from Eccles and Bluebottle to bog men and ancient chieftains of Wales. I thought that the chucking of people into bogs was an Iron Age phenomenon -- or do those famous bog snorkelling championships go back a lot further in time, into the Neolithic? And as for Idris, that particular chieftain could hardly have had any influence in Pembrokeshire -- that territory was ruled over by the ancient ancestors of Elvis Preseli.

BRIAN JOHN said...

Chris -- what evidence do we look for that might indicate the past presence of a glacier? Very difficult, since the evidence is often very subtle. As we have discussed on this blog many times before -- I recall much discussion with Geo Cur -- sometimes an area is assumed NOT to have been glaciated, until somebody chances upon some incontrovertible but previously undiscovered evidence. Even in wandering across parts of Pembrokeshire, which we know to have been glaciated mire than one, you can wander about across the farmed landscape without seeing any till, any erratics or any traces of fluvioglacial ection. So what are we looking for? Strange stones in buildings, foundations, road cuttings, pits, gardens, walls, hedges, etc -- and maybe some interesting horizons in the regolith between bedrock and ground surface. Pete G and Tim D are doing excellent work in seeking to find "anomalous" boulders and to determine how they got to where they are today.....Happy hunting!

chris johnson said...

Brian, I am hot to trot in pursuit of evidence. When you tell me I will not find it then I might conclude that I am better off watching the Golf Channel on my digital TV.

I prefer believable stories and the more exciting the better - the Golf Channel is not that good.

BRIAN JOHN said...

Oops -- I meant "...to have been glaciated more than once..."

Chris -- I never said you won't find any evidence. If it's there, it's there, and if it should be found, I shall be very chuffed indeed. If it's not there, it may be somewhere else.....

if you are sitting comfortable, let me tell you a story. back in 1962 I found what I thought was one of the best cliff sequences of glacial and periglacial deposits in Wales, not far from Porth-clais. I spent weeks working on it, and based a whole chapter in my thesis on what I had discovered. Years later, I walked the same bit of coast, and found less than half a mile away a much better section which I had totally missed previously, in spite of what I thought was a careful and detailed examination of the clifftops in the area. I thought "How the hell did I miss that?!!" But miss it I did -- maybe because the vegetation was high at the time, or maybe because it was pouring with rain, and I felt miserable as I passed close by..... So there we are. It just goes to show...

Phil Morgan said...

Brian,

Perhaps Pete G and Tim D could include "anomalous" Blue Pennant Sandstone in their search, for there has been over 250 cubic kilometres of that material removed from the South Wales Coalfield and carried south to join the Irish Sea Glacier; the same Irish Sea Glacier that is supposed to have carried the bluestones from the Preseli area.

Unfortunately, no Pennant erratics, of which there should be an abundance, have been found on Salisbury Plain.
Your answer may be that all the sandstone is now beneath the Bristol Channel, which is convenient for your theory; but would not all the bluestones also be on the seabed?
Was it not indicated that the concentration of rhyolite sources at Pont Saeson pointed to human transport.

This is supported by the following, permitted, extract from Dr. Steve Burrow's latest book "Shadowland, Wales 3000 - 1500 BC", Oxbow Books and Amgueddfa Cymru - National Museum of Wales, 2011, pages 49 -50.
"More hotly debated than the source of the stones has been the mechanism by which they came to be on Salisbury Plain. At the start of the twentieth century it was generally assumed that they arrived at their present location by the hand of man, but in in 1901 J W Judd suggested it was more likely that they were carried by glaciers which spread south before melting and dropping the stones they had picked up along the way. One key point militates against this view: despite considerable searching, there is no widely accepted evidence for glaciers reaching Salisbury Plain. Certainly glaciers may have carried the stones part of the way - research by Richard Bevins has shown that glacially transported stones from Ramsey Island in Pembrokeshire are known as far east as the Vale of Glamorgan - but no suitable sized blocks of Preseli bluestone have yet ben found eroding from the boulder clays of southeast Wales. While debate continues, at present it seems more likely to the author that the builders of Stonehenge acquired their stones from the Preseli Hills themselves."

Phil M.

Phil M. said...

Chris,
You ask "If the route was overland by human agency, where is a plausible route?".

Recently I mentioned sirley Toulson's book "The Drovers' Roads of Wales II, Pembrokeshire and The South". The following quote is from her earlier book "The Drovers' Roads of Wales", 1977.

"It is not possible to estimate how many cattle were brought into England from the whole of Wales in any given century, but some round figures for particular regions have been recorded. A seventeenth-century writer reported that three thousand head of cattle went annually from Anglesey into England; and by the end of the eighteenth-century that figure had trebled. At that time there were reports of six thousand cattle coming from the Lleyn peninsula; while futher south the cattle journeying through mid-Wales to Hereford were reckoned to number some thirty thousand". The map for the Hereford part of the route starts at Lampeter and travels via Abergwesyn, Builth Wells, Bredwardine and Hereford.

Compared to walking thirty thousand cattle from Wales into England in a year, transporting 80 odd bluestones in 15 months would have been a doddle, but the routes would have been the same.

Cheers,

Phil

chris johnson said...

Thanks Phil for the tip. I got hold of a copy of her book and a delightful read it is too. The speed at which a herd of pigs moves is roughly equivalent to the speed of the A-frame construction.

The more I look into Pembrokeshire in the neolithic the more likely it looks that there would have been trackways.

BRIAN JOHN said...

Phil and Chris -- this is getting absurd. Nice fantasy, all this stuff about the drovers. But what on earth has any of it got to do with the Neolithic? Phil,you say: "Compared to walking thirty thousand cattle from Wales into England in a year, transporting 80 odd bluestones in 15 months would have been a doddle, but the routes would have been the same." Absolute nonsense, if I may say so. Wonderful though the books about the drovers may be, they relate to a particular supply and demand situation, where rural suppliers in West Wales were providing meat on the hoof for the growing urban populations of England. You might as well take railways or roads, or the herring fishery, and claim that they tell us something about bluestone transport.

Chris-- "The speed at which a herd of pigs moves is roughly equivalent to the speed of the A-frame construction." What is that supposed to mean? Sound like a great mystical statement from somebody like Eric Cantona! The speed at which a cuckoo flies is roughly the equivalent of the speed at which I clean my teeth..... big deal.

Of course there were trackways in Pembrokeshire in the Neolithic. The questions are these: where were they, and how widely used were they, and how capable were they of use by large groups of people transporting heavy loads?

BRIAN JOHN said...

Phil -- "there has been over 250 cubic kilometres of that material removed from the South Wales Coalfield and carried south to join the Irish Sea Glacier; the same Irish Sea Glacier that is supposed to have carried the bluestones from the Preseli area." You are all screwed up here -- the fact that we have large valleys running from the South Wales uplands towards the south does NOT mean they were all cut by glaciers. Yes, glaciers used them and deepened and widened them, but you are making wild and unsupportable assumptions here. The landscape evolution history over the last 20 million years was much more complex.

Steve Burrow mentions his colleague Richard Bevins (who looked at the Storrie collection rocks) but he has major problems in holding a consistent line in his discussions. He is the one who says in "The Tomb Builders" that ALL of the megalithic monuments of Wales were built by opportunists and "rock scavengers" who used whatever rocks they could find locally for their megalithic structures.
He has a major problem with Stonehenge, because in breaks every rule in his rule book -- as I have pointed out before on this blog.

Anonymous said...

PMT Brian?

Go have a lie-down dear, I'll go get you a cup of tea and a piece of bluestone rock cake from Preseli... wont be long... sorry the 'A' frames in my way I could be longer than you think!

Annie O.

BRIAN JOHN said...

My level of tolerance is a constant source of amazement to certain impartial observers....

Phil Morgan said...

Brian,

1). Suupply and demand is precisely what occurred with the bluestones; Wessex require them and west Wales supplied them, I see no problem with that.

2). With reference to railways, roads and herring fisheries; railways and roads tend to use wheels, and the jury is still out on whether wheels were available for transporting the bluestones. People and animals walked the drovers' roads just as they did in neolithic times; a far more sensible comparison.
I fail to see what herring fisheries have to do with the debate unless they are 'red' herrings intended to ridicule all valid suggestions.

3). Cleaning teeth = another red herring.

4). I am far from screwed up when looking at the valleys of the South Wales Coalfield.
You agree that glaciers used them, deepened them and widened them, but you cannot tell me to what extent the glaciers enlarged the valleys.
Similarly it could be said that it was the glaciers that cut the south Wales valleys and they were then modified by rivers - an equally valid statement, but it still doesn't account for the vast amount of absent rock.

To prove that my assumptions are both wild and unsupportable requires evidence of Pennant Sandstone erratics on Salisbury plain, evidence which is absent.

5). You say that Steve Burrow is the one who says in 'The Tomb Builders' that "ALL of the megalithic monuments of Wales were built by opportunists and "rock scavengers" who used whatever rocks they could find locally for their megalithic structures."

I will now make an assumption and assume that you possess, and have read, Dr. Burrow's Tomb Builders book.
If that is the case then I must also assume that you are purposely trying to mislead your bloggers by being selective with your quote, for Dr. Burrow goes on to say,

"Indeed, there is only one example of transportation of megaliths in the whole prehistory of Wales, and this occurred several hundred years after the construction of the last megalith tomb. The transportation of the Preseli bluestones from Wales to Wiltshire for the building of Stonehenge was the remarkable exception to the evidence that construction involving megaliths was usually carried out near the source of raw materials."

Far from having a major problem in holding a consistent line in his discussions it shows that he really is unswerving in his dialogue.

This is at least the third occasion that you have mis-quoted that paragraph so in future I shall just reply "PAGE 65" which will save me a great deal of typing.

Phil M.

BRIAN JOHN said...

Phil

1. Supply and demand. Pure speculation. Zero evidence.

2. You have no evidence that the drovers routes were based on Neolithic trackways. The drovers'routes were designed to minimise the impact on farmland, to minimise animal losses due to exposure in the high mountains, and to maintain good control over large numbers of animals. Neolithic inhabitants will have had none of those priorities.

3. Cleaning teeth a red herring? Not so. Just think about the absurdity of the statement I was examining.

4. Pennant sandstone erratics should be on Salisbury plain? The South Wales landscape has had thousands of feet of rock eroded off it, over many millions of years. Where are all of the upper Palaeozoics in North Pembrokeshire? Stripped off. Lost -- not exactly without trace, but deposited in wherever the lowlands were at the time. ask any geologist to explain it for you.

5. I have never misrepresented Steve Burrow. Stonehenge is not in Wales. It is at Stonehenge. It is pure speculation on his part that the Stonehenge bluestones were transported by human beings. it remains true that all of the megalithic monuments in wales are made of local materials.

Phil Morgan said...

Brian,

You are obviously correct for you are Brian.

Phil M.

BRIAN JOHN said...

End of discussion. We were supposed to be talking about sandstone thin sections.......