THE BOOK
Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click
HERE

Thursday, 27 August 2020

Carnalw cultural landscape



This map, compiled by Dyfed Archaeology and published in 2010, shows the results of the detailed survey of Carnalw and the surrounding area.  The rock outcrops are in black and the prehistoric features (and some that might be medieval) in grey.  This is a truly extraordinary assemblage of features, including stone walls, huts, circular and rectangular enclosures or fields, stone clearance cairns and trackways.   The bulk of the features are assumed to be date from the  Late Bronze Age / Early Iron Age -- ie approx the same age as the features on top of nearby Foel Drygarn.



The prominent tor of Carnalw, showing the triangular defended platform on the western flank of the ridge, the "chevaux de frise" defensive system to the SW of it, and the angled entrance corridor.  on he eastern flank of the tor there are a large number of apparently ice-moulded features.



Foel Drygarn in high definition


Another high-definition image from the new satellite imagery published on Bing Maps.  This is the Foel Drygarn summit, showing the crags and the quarries, the three assumed Bronze Age carns or burial cairns, the defensive embankments probably dating from the Iron Age, and the pitted landscape where the huts of the village were located.

Waun Mawn excavation sites


There is brand-new imagery with fantastic definition available via Bing Maps -- it uses imagery from the OS and Tom Tom, much of it dating from 2020.  Here is a piece of the N Pembs imagery, showing the standing stone and recumbent stones taken by Prof MPP and his jolly gang to indicate the location of a "proto-Stonehenge" standing stone circle at Waun Mawn.

The digs at this site were in 2017 and 2018 -- there was no digging last year, and I imagine there will be nothing this year either.

The moorland is gradually recovering from the assault, but we can see clearly where the trenches were opened up, mostly on the western part of this site and fixed quite deliberately on the supposed circumference of the supposed stone circle.  As I have mentioned before, the evidence for a stone circle here is very scanty indeed, and the diggers have done nothing to establish whether the "Neolithic activity" here was any greater than the activity across the rest of this landscape -- replete as it is with prehistoric traces.  And the idea that any of this has anything at all to do with Stonehenge is of course completely preposterous.

The old archaeological records for this area (from the 1800s and early 1900s) suggest that at one time there were traces of a number of stone circles, none of which seems to have been completed.   

Morainic ridges at Gelli-fawr and Gernos-fawr?

I have been looking again at the satellite imagery of the Preseli foothills, and am intrigued by a series of alignments showing up in the vicinity of Gelli-fawr and Gernos-fawr.  I have remarked on these before, in a number of posts.  The features -- seen in very subtle changes of tone in grassy fields -- have a surface relief maybe no greater than a metre, but there is a consistent pattern, and I need to check it out.

I'm keeping an open mind here -- the features may be structural, showing bedrock outcrops beneath a thin superficial layer.  Intriguing, nonetheless.  On the illustrations below I show the undoctored versions and the annotated versions, so that you can see what I am up to......





It's conceivable that these features are ice-marginal channel remnants, cut by meltwater flowing along a lowering ice edge, but they look a bit too irregular for that, and if they really are ridges then they must be marginal or terminal moraines created on an ice front.

Interestingly enough, these features do not show up very well on the phenomenal new satellite imagery (dated 2020) from Bing Maps -- maybe the above images are courtesy a low sun and diffuse light......


Tuesday, 25 August 2020

Cana Independent Chapel -- facade with spots


I've been to have another look at Cana Independent Chapel in Felindre Farchog, one of the few that are known to have spotted dolerite blocks incorporated into the facade.  It's a Grade 2 listed building which no longer has a congregation -- it was sold into private hands about four years ago.  It's beginning to look a bit sad....

I wanted to see just how many blocks of spotted dolerite there are in the front face of the chapel.  There are certainly plenty of them, but most are crudely dressed, and the chapel is not particularly well built.  The foundations are dodgy, the stonework is roughly hewn, and the pointing is of poor quality.   Dyfed Elis-Gruffydd refers to the stones as "hammer dressed".  All sorts of stones are incorporated into the facade, and it was clearly not a priority of the congregation, when the chapel was rebuilt in 1857, to face the building exclusively with "posh stone" -- included are assorted other dolerites, some rhyolite, some shales and slates, and even some local sandstones.  I reckon that maybe 10% of the stones are spotted dolerites.  The facade is nothing like as sophisticated as that of Bethel Chapel in Mynachlog-ddu.

So where did the spotted dolerites come from?  I doubt that they were "quarried" exclusively from Carn Goedog -- I think it much more likely that they were picked up from many different sources on the northern flank of the Preseli uplands.



Spotted dolerite erratics at Glan-yr-Afon, near Crosswell



In a howling gale (mercifully no rain) I have been back to look at the assemblage of erratic boulders on the edge of the moorland near Crosswell around grid ref SN119351.  The nearest cottage is Glan-yr-Afon, currently being renovated.  Due south, a couple of hundred metres away, is the house called Glan-yr-Afon-uchaf.  There is an interesting piece of grassy and hummocky common land near here -- used every year for the start and finish of Ras Beca, a very tough fell race which takes runners up onto the top of the Preseli ridge and back again across boggy moorland.........


I have done one previous post about this site:

https://brian-mountainman.blogspot.com/2017/10/the-spotted-dolerite-enigma.html

... and I am seriously intrigued by it. There are so many heavily abraded and faceted boulders here (some disturbed but most in situ) that I'm increasingly convinced that this is a moraine.  There is actually a back slope facing towards Carn Goedog, which is about 2 km away, although the land is generally falling away northwards towards the lower lands of the Brynberian and Nevern valleys.

A little stream runs north towards Pont Saeson, where it joins the Afon Brynberian.   It's incised into the surface of what appears to be a morainic accumulation more than 10m thick. There are a number of exposures of stony till in the vicinity, full of cobbles and larger erratics of dolerite, rhyolite, spotted dolerite and quartz.  There are some other igneous rocks too that appear to be volcanic ashes and gabbros.  As I mentioned in my earlier post, we are right on the edge of the Fishguard Volcanics outcrops here, where ashes and lavas are supposed to predominate.  Igneous intrusive rocks are not supposed to be here -- there are supposedly no intrusive outcrops until we reach Carn Goedog.  But the great majority of the erratic boulders here are made of spotted dolerite.  Where have they come from?  Could they have come from the west, carried by ice from the outcrops around Waun Mawn and the headwaters of Cwm Gwaun?  That is possible, but I'm not aware of any spotted dolerites in that neighbourhood.  The nearest source of spotted dolerites would be Carn Goedog -- but that would involve ice from a Preseli ice cap flowing towards Brynberian and Crosswell.  I have speculated on that in the past, and there is some evidence in support, but more detailed mapping is needed.



Close-ups of two spotted dolerite boulders from the common near Glan-yr-Afon

I'm confused.  But leave it with me.  I'm working on it.........

Glacial landforms and the glacial timescale


With regard to nothing in particular, I came across this very appealing diagram in an article about the glacial landforms and landscapes of Norway.  It's created by Clas H├Ątterstrand, and shows the timescales over which glacial landscapes and landforms are created.  We can argue with the details, but the general principles seem to be sound.  The highest-order landscapes are at the top, and the lowest-order (cracks, striae etc) are at the bottom.  The lowest-order features may be created in less than a week, given the right conditions, but the highest-order features like fjords and outlet glacier troughs take many thousands of years to form, across several glacial episodes.  Somewhere in the middle of the diagram we flip from the features that might have been  created in the Late Devensian Glaciation into features which are inherited and which get extended / refreshed every time a new glacial episode comes along.....

The irresistible allure of garbled nonsense



I came across this article from 2015, and read it, and found it rather interesting, and worth sharing.

https://www.theatlantic.com/education/archive/2015/10/complex-academic-writing

EDUCATION
The Needless Complexity of Academic Writing
A new movement strives for simplicity.

VICTORIA CLAYTON
“The Atlantic”, OCTOBER 26, 2015

Extract:
A disconnect between researchers and their audiences fuels the problem (of needlessly complex writing), according to Deborah S. Bosley, a clear-writing consultant and former University of North Carolina English professor. “Academics, in general, don’t think about the public; they don't think about the average person, and they don't even think about their students when they write,” she says. “Their intended audience is always their peers. That’s who they have to impress to get tenure.” But Bosley, who has a doctorate in rhetoric and writing, says that academic prose is often so riddled with professional jargon and needlessly complex syntax that even someone with a Ph.D. can’t understand a fellow Ph.D.’s work unless he or she comes from the very same discipline.

A nonacademic might think the campaign against opaque writing is a no-brainer; of course, researchers should want to maximize comprehension of their work. Cynics charge, however, that academics play an elitist game with their words: They want to exclude interlopers. Others say that academics have traditionally been forced to write in an opaque style to be taken seriously by the gatekeepers—academic journal editors, for example. The main reason, though, may not be as sinister or calculated. Pinker, a cognitive scientist, says it boils down to “brain training”: the years of deep study required of academics to become specialists in their chosen fields actually work against them being able to unpack their complicated ideas in a coherent, concrete manner suitable for average folks. Translation: Experts find it really hard to be simple and straightforward when writing about their expertise. He calls this the “curse of knowledge” and says academics aren’t aware they’re doing it or properly trained to identify their blindspots—when they know too much and struggle to ascertain what others don’t know. In other words, sometimes it’s simply more intellectually challenging to write clearly. “It’s easy to be complex, it’s harder to be simple,” Bosley said. “It would make academics better researchers and better writers, though, if they had to translate their thinking into plain language.” It would probably also mean more people, including colleagues, would read their work.

Some research funders, such as National Institutes of Health and The Wellcome Trust, have mandated in recent years that studies they finance be published in open-access journals, but they’ve given little attention to ensuring those studies include accessible writing.


---------------------------


This strikes a chord, given some of the topics recently discussed on this blog.  For years I have been concerned about the increasing tendency in academia for specialists to effectively develop their own languages, designed to reinforce the exclusivity of their little clubs.  I'm very much aware of it in my own discipline, glacial geomorphology, where researchers are (for obvious reasons) trying to demonstrate that they are highly-trained specialists who deserve respect (and funding) from academia generally and from their universities and research bodies.  So we (I am one of them) have developed a jargon, including many words not understood by anybody else, which we use in our publications -- so we communicate with our peers, and shut everybody else out.  Since our peers are the ones who determine our career paths, that's all OK........ and we may even get a rosy glow when somebody else says to us: "We looked at your paper.  Didn't understand a word of it...."  We live within our tribes, and they provide our reassurance and our security. All the other people out there are outsiders and inferiors. 

Over the years since I started this blog, I have tried to scrutinize and "de-mystify" many articles which have been virtually impenetrable!  Sometimes I have to give up in despair, and papers just disappear without mention.  Sometimes I misunderstand things or am guilty of failing to spot crucial bits of information -- that's the way of the world.  But more often I find myself asking "Why could not these people (multiple authors are the norm, these days) express themselves more clearly?"  My instinct, certainly, is to be deeply suspicious of the intentions and the conclusions of the writers of articles that are complex or convoluted.  It's all too easy for these writers -- who think they can get away with it -- to slip into the territory of invented evidence and falsified results.

More and more often, I perceive that authors dress up their research in such complexity that one has to assume that the intention is to avoid scrutiny when of course they should welcome it.  The average reader sees statistical analysis, complex tables and data sets, graphs and diagrams, and descriptions of experimental results involving highly sophisticated gadgetry and thinks: "Wow!  This is high-powered science!  Brilliant!  When the authors say in their abstract and in their press release that this work represents a fantastic advance, it must be true!"  The trouble is that it might also be garbled nonsense, from beginning to end.  Technology is not the same as science.

As I have frequently complained on this blog, editors and journalists nowadays read press releases and watch promotional videos -- the more spectacular the better -- and hardly ever actually read journal articles.  Academics are fully aware of that.

In recent weeks we have discussed the work of Carl Sagan, Gordon Barclay and Kenny Brophy, and it all comes into sharp focus when we consider this matter of academic writing.  There are many interconnected issues here.  One of them is the "sexing up" or interpretative inflation of evidence, as described in the latest edition of "British Archaeology".  Of course, the more impenetrable a specialist journal is, the greater is the pressure for a "second tier" or glossy "pop" article in a journal like "Current Archaeology" or "British Archaeology" -- where authors have to simplify and summarise their findings for the common man.  Almost always, in these articles, caution is thrown to the winds and academic standards are lowered.  Our old friends, Ixer, Bevins, Parker Pearson, Darvill, Richards, Pollard and many others are old hands at it --  sometimes two, three or four separate articles (all capable of citation) appear, all based on the one piece of research with very minor tweaks.  The principle seems to be that if you repeat a dodgy hypothesis often enough, with enough conviction, if becomes the truth.

I was hunting down this particular issue recently with respect to the "research" at West Angle Bay and Llandre, both selected as type localities for the Penfro Till on the basis of multiple cross-citations of apparently "learned" articles and virtually no published field research.  Some people, who should be ashamed of themselves, just haven't read the literature properly.

What's to be done?  Well, for a start, if you can't understand something, for safety's sake assume that the writer is a charlatan.......






Monday, 24 August 2020

The Stonehenge Myth Machine -- high time for a spanner in the works


A stone juggernaut -- another one is the place called Stonehenge.......

There have been a couple of reminders in recent days of just how dangerous the Stonehenge myth machine has become -- running completely out of control and, as far as I can see, deliberately dressing up falsehoods as truth.  It also flattens and demolishes other things that deserve to stay alive.  It may be wonderful as a public relations exercise, and for the commercial interests of English Heritage, but academic rigour appears to have been abandoned.

Reminder Number One.

Thanks to Tony and Dave for bringing this to my attention.  In the latest issue of British Archaeology Gordon Barclay and Kenneth Brophy have been given some space to back up their recent highly influential article on the development of the Late Neolithic "Mythos" of Stonehenge and the Salisbury Plain area being not just a modern "iconic place" but also a place where Neolithic civilisation in the British Isles reached its high point.  The two authors are terribly polite -- and I can understand why -- so they are reluctant to name names;  but it's pretty clear that they have the British archaeological establishment in their sights, and that they are not best pleased by the Stonehenge obsession of Mike Parker Pearson, Tim Darvill, and many other senior academics who have made their careers on the basis that all roads (literally and metaphorically) lead to that ruinous collection of old stones on the chalk downs.

Gordon J. Barclay & Kenneth Brophy (2020): ‘A veritable chauvinism of prehistory’: nationalist prehistories and the ‘British’ late Neolithic mythos, Archaeological Journal,
DOI: 10.1080/00665983.2020.1769399

https://brian-mountainman.blogspot.com/2020/07/bluestones-and-interpretative-inflation.html
https://brian-mountainman.blogspot.com/2020/06/the-origins-of-british-neolithic-mythos.html
https://brian-mountainman.blogspot.com/2020/06/the-politicisation-of-neolithic.html

In their new article, on p 48-49 of British Archaeology for Sept/Oct 2020, the two authors don't mince their words, although they steer clear of mentioning names, and there are no citations of specific articles.  But they complain about the powerful bias of British prehistory, with the greater part of the British Isles treated as "the periphery" and therefore inferior or subservient to the "core" at Stonehenge and Durrington.  They accuse senior archaeologists and the archaeology establishment of ramping up the glorification of the Stonehenge area around ten years ago while marginalising "distant places" as being inferior or underdeveloped.   They also have a dig at "assumptive research" which uses supposedly scientific methods to support, and not to test, the central hypothesis of "Wessex superiority".   They make no bones about it -- they are clearly not impressed by the wild claims of those who have used new technologies to link teeth and bones from far-flung places (or maybe just a few miles away) to Stonehenge and its appendages.  They also have a go at interpretative inflation -- something I have covered several times on this blog.  The blurb at the head of the article refers to "the way in which universities judge academic success" and to the distortion of public understanding of the past.  Yes, the authors do refer to that,  and talk about the sexing up of research because that is what the Research Excellence Framework demands.  And yes, they do the meeting of targets as being nowadays more important than research integrity.  That's a pretty serious charge, which I have made many times on this blog. But this is not the main point of the article, whatever the editorial take on it may be.  The main point is that when people like Mike Parker Pearson and his research team pretend that people came from all corners of Britain "to build Stonehenge" and to "unify Britain", they are talking nonsense.  Yes, they really do use that word........  They complain about endless funding being appropriated to the perpetration and development of the myth, to the detriment of serious research elsewhere, and they make the eminently sound point that when vast sums of money are invested in looking for amazing things on pre-selected places, we should not be too surprised when apparently "amazing things" are found -- even if they do not actually exist.  They could have mentioned the hunt for those imaginary bluestone quarries in Pembrokeshire, or the hunt for proto-Stonehenge, or the hunt for the great Stonehenge sarsen quarry.............

All in all, it's a hard-hitting summary of what is contained in their longer article, and we await with interest the reaction of the establishment.....


Reminder Number Two.

Again, thanks Tony for the alert!  A podcast in the series called "You're dead to me" on BBC Sounds:  https://www.bbc.co.uk/sounds/play/p07qrwq7. It's a very jolly radio chat  involving Susan Greaney (who is rapidly becoming "the voice of Stonehenge" -- well, I suppose it is her job, after all),  Greg Jenner and Richard Herring.  OK, it was entertainment and comedy, so there were a lot of smart one-liners and a lot of giggling -- but there was un underlying serious purpose to the show -- namely to popularise history and prehistory and to allow "the truth" about Stonehenge to emerge from a freewheeling jovial chat between three articulate and intelligent people.  That's where the trouble began, because Susan was there as "the expert" who was presumed to know the truth.  But what we got was one small myth after another, and in a broader sense a very crude portrayal of Stonehenge as the "centre of things" -- towards which things (people, animals, raw materials) migrated from the farthest-flung parts of the British Isles.  This is exactly the narrative that Barclay and Brophy are protesting rather loudly about.  Not surprisingly, Susan appears not to have heard of them or their article ...... but if she was aware the criticism of the "Mythos" she carefully avoided any mention of it.

 

So to her little falsehoods.  There were so many that I gave up on making detailed notes, but these come to mind:

1.  She referred to the"newly discovered bluestone quarries" in Pembrokeshire.  Mythology, not fact.

2.  In talking about the Darvill - Wainwright theory about Stonehenge as a healing centre, she said that bluestones are associated with healing in the folk traditions of Pembrokeshire.  Mythology, not fact.  Darvill and Wainwright invented that -- there is no foundation for it at all.

3.  She said that the only obstacle to the human transport of the bluestones from Pembrokeshire to Stonehenge was a shortage of manpower.  She must know that that is nonsense.  There were immense Neolithic technical and geographical / environmental difficulties that render the human transport of 80 or so bluestones vanishingly unlikely.  She also said that the Millenium Stone project failed because of the shortage of volunteers to drag the stone.  I was there. She is wrong. Even with modern ropes and low-friction netting and with the occasional help of cranes and tractors, and with abundant manpower, it was a nightmare to move the stone on asphalt toad surfaces; it would have been well-nigh impossible if we had tried to move the stone cross-country through fields and woodland.

4.  She said that in her view Stonehenge was completed as an "immaculate monument" -- there is just not enough evidence to support that assertion.  More and more experts seem to be moving to an acceptance that the monument was not finished.

5.  She said that "most geologists" have declared that the glacial transport of the bluestones could not have happened.  Which "most geologists" has she talked to?  They must be a different batch of geologists from the ones I talk to.  In any case, geological opinions are pretty irrelevant here -- most geologists have never even thought about Stonehenge or heard of the bluestone controversy.  Of much greater validity are the opinions of geomorphologists and glaciologists.  In other words, people like me.

6.  She said that it is now accepted that the glaciers of Britain did not move as far south as Stonehenge.  That is still a matter of debate.  The key question is not how far south the glaciers extended, but how far EAST.  She may, like other archaeologists, have a problem with the idea that glaciers can move in any direction, and that as far as the Bristol Channel is concerned, the ice came from the west and flowed eastwards.

7.  She said that the new research techniques (isotope measurements, DNA studies etc)  into bones, teeth etc have established the movement of animals and people from far away to Stonehenge and Durrington Walls, implying that they were drawn from the periphery towards the centre.  As Barclay and Brophy have pointed out, this is a travesty, involving many misreadings of the data and huge interpretative inflation --  with no attempt even to explore the possibility that any one of a multitude of Neolithic and Bronze Age sites in these islands had a similar -- and maybe even greater -- traffic of animals and people from far and wide.

There was more -- but I got a bit fed up after a while.  What I did find concerning was Susan's tendency of pontificate or talk down to her audience, as if to say "Listen to me.  I'm the expert, and what I tell you is the truth -- the other wacky theories flying around are all good fun, but are best ignored by serious people who want the facts."

This new broadcast follows hard on the heels of this:
https://brian-mountainman.blogspot.com/2020/07/the-mythification-of-absolutely.html

In conclusion, I am with Barclay and Brophy all the way on this -- and it would be rather useful if the wheels were to come off the Stonehenge juggernaut and if we could have some respect for the facts and a more nuanced interpretation of what went on in the British Isles 5,000 years ago.








Sunday, 23 August 2020

Fieldwork is the thing......



Thanks to brother-in-law Ken for these pics, taken the other day when we had a good bracing walk up among the high peaks of Preseli.  We did get soaked, of course -- but what do you expect when it's August in west Wales?  Anyway, every time I go up there I discover something new.......

Friday, 21 August 2020

Glacier porn -- NASA / Ice Bridge images



This is somewhere in Antarctica.  Classic extending flow in a glacier flowing at a steady pace, probably over a slightly convex slope.  The ice is under tension, and the pattern of regular crevasses is perpendicular to the direction of flow.




This one is from Alaska, I think.  A glacier with two halves -- the right hand ice stream is active, with relatively clean ice.  But the left hand segment is filled with debris and is decaying rapidly. There is a vast area of dead-ice wastage, and from the wavy pattern in the ice it appears that this segment has been subject to surging behaviour.



There are two big ice discharge routes here, on either side of this spectacular ridge.  There is at least one classic "arete" and the end product, after more glaciation, would be the horns or tinds that we see in many areas of long-continued glaciation.  This photo is, I think, from west Greenland.

NASA adds new images to its "Ice Bridge" pages all the time.  This is a recent selection from Antarctica, Greenland and Alaska

https://www.nasa.gov/mission_pages/icebridge/image-gallery/index.html

Ice-margin and lake -- Humboldt Gletscher, Greenland


A great Operation Ice Bridge photo of the ice edge of the Humboldt Glacier in Greenland, with the ice-free area of Washington Land on the left.  The ice edge of the Irish Sea Glacier in Pembrokeshire might not have looked very different -- with occasional temporary ice-margin lakes.  Note that here the ice is relatively clean, with no prominent ice edge moraines....

From a report in the Guardian about the catastrophic rate of ice melt on the Greenland Ice Sheet

Thursday, 20 August 2020

Penfro Till Formation -- nice name, pity about the evidence.....


It's strange that extremely dodgy material can find its way into official records and then be accepted as "established fact" even if there is no evidence in support of it.  A salutary lesson for all of us.......

I have found another reference to the "Penfro Till Formation" in this august publication.  

GEOLOGICAL SOCIETY, LONDON, ENGINEERING GEOLOGY SPECIAL PUBLICATIONS
Engineering Geology and Geomorphology of Glaciated and Periglaciated Terrains: Engineering Group Working Party Report by J. S. Griffiths and C. J. Martin
The Geological Society of London
Volume 28
DOI: https://doi.org/10.1144/EGSP28
Publication date:
January 01, 2017

https://pubs.geoscienceworld.org/books/book/2101/Engineering-Geology-and-Geomorphology-of-Glaciated

The official BGS citation or record is still unchanged, in spite of me complaining a few years ago that the two cited "partial type sections" at Llandre and West Angle Bay are effectively useless, never having been properly described.  At West Angle, there was a fundamental misunderstanding of the coastal exposure by Dixon and then DQ Bowen, and it appears that nobody can be bothered to correct the records.

This is a key post on this blog, in which I examine the evidence for the "pre-raised beach till deposit" at West Angle, and find it to be seriously defective:

https://brian-mountainman.blogspot.com/2017/03/the-west-angle-enigma-3-two-tills-or-one.html

See also:

https://brian-mountainman.blogspot.com/2017/02/penfro-till-formation.html

https://brian-mountainman.blogspot.com/2017/02/llandre-gravel-quarry-where-is-penfro.html

https://brian-mountainman.blogspot.com/2019/01/uk-quaternary-domains.html

https://brian-mountainman.blogspot.com/2019/01/the-curse-of-lithostratigraphy.html

https://brian-mountainman.blogspot.com/2019/01/penfro-formation-lexicon-correction.html

https://brian-mountainman.blogspot.com/2019/10/preseli-glacial-deposits.html

I am used to having a go at English Heritage and the archaeologocal establishment on this blog -- but it appears that the BGS and the geology establishment are not much better at either communicating or getting rid of myths dressed up as facts......




Wednesday, 19 August 2020

The interglacial - glacial sequence at West Angle Bay


I have been looking again at some of my research material relating to West Angle Bay, and regret that I never did publish a full research monograph back in the 1970's!  Because I didn't, a good deal of material on this location was published by others who had not had the chance to examine the sequence properly -- so speculation took the place of accurate observations and measurements.  Such is the way of the world.......

Anyway, the site is in danger of disappearing because of ongoing coastal erosion, and this is seriously bad news since West Angle has to be the most important interglacial site in Wales, as well as telling us a lot about the extent of Late Devensian Irish Sea Glaciation.

My blog entries on West Angle contain most of the key information, and my analyses of past research work which has appeared in print.  The most important records appear in the three blog posts under the title of "The West Angle Enigma" (1) (2) and (3):

https://brian-mountainman.blogspot.com/2017/02/the-west-angle-enigma.html
https://brian-mountainman.blogspot.com/2017/03/the-west-angle-enigma-2-silt-and-clay.html
https://brian-mountainman.blogspot.com/2017/03/the-west-angle-enigma-3-two-tills-or-one.html

See also:

https://brian-mountainman.blogspot.com/2020/08/the-west-angle-sediment-sequence-moreys.html

https://brian-mountainman.blogspot.com/2017/03/west-angle-gallery.html

https://brian-mountainman.blogspot.com/2017/03/west-angle-bay-classic-coastal-section.html

For the record, I have re-scanned one of the key diagrams which was very faded and discoloured, and assembled the other measured sections into one place, so here they are:



The outer (northern) end of the drift cliff at West Angle. Here, overriding ice has removed the bulk of the interglacial sediments, and the bulk of the sediments exposed in the cliff face are related to the Devensian glaciation. The raised beach is at considerable depth, or is absent. The best exposures of Irish Sea till occur around point B.


The middle part of the surveyed section. At E we can see the slip face / slump face / erosional contact, to the left (north) of which the bulk of interglacial sediments have been cut out. At D the bulk of materials exposed are glacially related. Between F and H the bulk of the exposed sediments are fine-grained interglacial silts and clays overlying the raised beach.



The southern part of the surveyed section, extending northwards from the bedrock slope. The bulk of the deposits exposed are interglacial, resting on the raised beach. Around J and K glacially-related materials sit on these deposits at the top of the section.



ThisThe key part of the West Angle sequence, near point (E) on the levelled section -- the erosional contact between the interglacial silt and clay series (to the right) and the dark red Late Devensian till (to the left).  The glacitectonic features need to be studied by a specialist!


A careful plot of the lower part of the sediment sequence at point (H), showing the transition between  the raised beach (near present-day HWM) at the base and the organic-rich interglacial sediments above.  The peat bed has not been exposed at all in recent years, and may never be found again.


A slab or lump of material from the interglacial silt and clay series incorporated into the dark red till in the glacitectonic "contact zone".  There are many detached slabs and fragmented layers in this zone, which explains why past researchers at this site have been very confused about the true sediment sequence.  Unravelling the story is made even more difficult by the frequent slumping on the cliff face and by the fact that every observer sees a different sediment sequence!

Tuesday, 18 August 2020

Much ado about nothing

A graphic from p 37 of the article, purporting to show the modal mineralogy of the Stonehenge volcanic bluestones.  It actually shows the data for selected samples 
from the Stonehenge debitage.

Provenancing the stones
Rob Ixer, Richard Bevins and Duncan Pirrie
Current Archaeology 336, pp 34-41

I suppose that duty compels me to mention this article, but it's one of those that says nothing new.  It is really just a summary, in a glossy format, of work already published but with the addition of some X-ray images and other graphics -- and its justification seems to be that if you repeat fallacies and fantasies often enough, they have a sporting chance of becoming "the truth."  

There is no archaeological input into this paper -- the three authors are all geologists, so it is all the more disappointing that the article is packed with unproven assumptions to the extent that any "good research" contained within it is seriously devalued.

The article  is supposed to be a description of a "second-generation" examination of the Stonehenge bluestones, using "new mineralogical, petrographical, and geochemical techniques" to complement older work based on established technologies including thin-section petrography and geochemistry.  The automated SEM-EDS images for rhyolite and spotted dolerite point the way to more accurate provenancing in the future, but there has been no new sampling here, and until the geologists extend the range of their fieldwork they are never going to convince other specialists that they have actually found the precise locations from which much of the Stonehenge debitage has come.  They still do not know how extensive the outcrops of "Carn Goedog spotted dolerite" and "Rhosyfelin foliated rhyolite" are, and they seem obsessed by the idea that the Stonehenge material has come from two quarries, because that is what Prof Mike Parker Pearson has told them.  So this article has huge built-in bias.  A little more independent scientific thought might not have come amiss.  

The bias is apparent right from the start.  In the blurb at the head of the article the authors ask "Where did the Stonehenge bluestones come from?" and then claim "Scientific advances are allowing us to pinpoint the outcrops that they were quarried from with ever-greater accuracy."  In the caption of the photo at the top of page 35 we read" Excavations at the Craig Rhos-y-felin Neolithic quarry-face lie in the foreground....."  So it goes on.  The assumption of quarrying runs right through the article, and if that assumption is deemed (by people like me who bother to scrutinize things) to be unproven, why should one take at all seriously anything else that is contained in the text?

It gets worse.  The authors say that the Rhyolite Group C debitage "only seems to match one of the buried orthostats (standing stones)."  There is no physical evidence for that, apart from photos of a bluestone stump that looks as if it might be made of "laminated" rhyolite.  They say that the Stonehenge Group C rhyolite debitage has "an established origin at Craig Rhos-y-felin".  That is not so.  An origin at that site is postulated, but not established, since the researchers have no idea how extensive the outcrop is across the landscape.   They say that a Neolithic quarry site was "recognized" at Carn Goedog by Parker Pearson.  The authors fail to mention that this claim is far from proven to a satisfactory scientific level, and is indeed hotly disputed.  I'm mystified by the graphic caption that reads "Modal mineralogy for the Stonehenge Volcanic bluestones" because all of the data appears to come from fragments or debitage, and not from the standing or fallen monoliths themselves.

An illustration from the article, showing an automated SEM-EDS image illustrating 
the fine-grained lensoidal fabric of the foliated rhyolite at Rhosyfelin.  We do 
not know which sampling point the sample was collected from.

Then there is talk of a prospect of "provenancing on a decimetre scale" across the "Rhosyfelin "quarry-face" and one wonders whether the authors are completely out with the fairies, given the heavy criticism already flung at them when they claimed to have done successful provenancing at Rhosyfelin "to within a few square metres" without any convincing supporting evidence and without any perfect matching of samples. This criticism has come not just from me, but from other senior earth science academics.


This is a weird statement (p 38) about Rhosyfelin:  " ........there appears to be a mismatch between the quarry size and the number of orthostats removed from it – the present working surface (albeit formed by a combination of prehistoric and historical stone extraction) appears far too big for the removal of the Rhyolite Group C orthostat believed to be buried within the circle."  It's the first recognition that I can recall from the geologists that there is evidence of modern stone extraction towards the top end of the exposed rock face (probably for the extraction of road-building hardcore) -- but maybe it's a first admission by the geologists that most of the quarrying at Rhosyfelin has been done by the archaeologists under the leadership of Prof MPP!

This is another weird statement on p 38, regarding the Rhyolite Group D debitage at Stonehenge:  ".......it was initially thought not to be a bluestone at all; it was instead considered to be a stray rock that had little to do with Stonehenge."  Since when are there "proper" bluestones and "improper bluestones" at Stonehenge?   I'm not the only one to have noted that there are stones and debris from a very large number of locations (quite possibly 30 or more) at Stonehenge.  If they are not sarsen stones,  and if we have to used the word "bluestone" to describe them, they are foreign and they have somehow or other found their way onto the site.   Or is it now only deemed proper to refer to something as a "bluestone" if it is deemed to have been quarried by our heroic ancestors?  This seems to be the suggestion:  "Rhyolite Group D is an entirely new and separate bluestone, quite different from any other volcanic bluestone, and therefore needs its own orthostat(s) and provenance."  Why does it "need" its own orthostat?  Has it not occurred to these geologists that some -- and possibly quite a lot -- of the debris at Stonehenge might have come from broken up cobbles, pebbles and small boulders rather than from the monoliths included in the Stonehenge numbering system?


A glimpse of the Altar Stone (EH photo).  Never sampled........

When the authors move on from igneous rocks to sedimentaries, the text does not become any more reliable.  The authors make the point that the Altar Stone and the Lower Palaeozoic sandstones are not from the Mynydd Preseli area.  To quote:  "......knowing their provenance has much to tell us. If they were ‘picked up’ along the way – making them ‘a secondary bluestone’ – while transporting the stones from Wales to Salisbury Plain, it informs us about possible bluestone movement routes. Conversely, if they were intentionally collected – ‘a primary bluestone’ – as a ‘cultural signifier’ somewhere far away from the Mynydd Preseli, then that vastly expands the provenance catchment area and potentially the people involved in the construction of the monument."  What is extraordinary about this little extract is that it comes from three geologists -- without any archaeology input -- who appear to be in a complete state of denial about the possibility of stone movement by natural processes including glaciation.  

The authors are good enough to admit that the Altar Stone has not been sampled, but in the text they still presume to know (for example in the graphic on p 39) what its geological characteristics are, and approximately where it has come from.  The discussion of sedimentary sources gets tangled up in yet another piece of assumptive analysis, underpinned by the all-powerful assumptions that there had to be quarries and that the "selected monoliths" had to be shipped, rolled or dragged from Wales to Stonehenge.  Again, there is no mention of ice action and ice movement directions as alternative -- and perfectly credible -- explanations for the gathering, transport and deposition of large stones and smaller debris.  Are these three geologists really completely unaware of the operations of natural processes within the landscape?

On page 41, the authors conclude the article by referring to potential provenancing "hotspots" in eastern Wales, and pretend that all they have to do to solve the remaining mystery of "sandstone sources" is to find two more precise locations for the extraction of suitable monoliths.  Again, there is no mention at all of natural processes even though it is known from modelling and field research that ice from eastern mid-Wales did flow southwards and south-eastwards, in exactly the right directions for the glacial transport of erratics.

I am amazed, and seriously disappointed by the poor quality of this article.  But there are some signs of light.  The geologists seem to have realised that most of the quarrying at Rhosyfelin has been done by Parker Pearson and his team;  they have recognized that the Stonehenge bluestone monoliths and debitage have come from multiple sources, some of which are still unknown; and while the quarrying obsession persists (and may require medical intervention or a miracle vaccine to bring about a good recovery) they have at least said this:  "The idea that a couple of quarries satisfied the needs of the Stonehenge builders is becoming increasingly untenable."

It's a slow process, but the geologists will get there in the end........









Monday, 17 August 2020

Sarsen distribution: Avebury and Stonehenge



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.

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.


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

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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......

----------------------------------------

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)

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.

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.

--------------------------------------

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:

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

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!


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).