Lower Palaeozoic sandstone at Stonehenge

I found this illustration in one of Rob Ixer's publications.  It's rather pixellated, but it shows an erratic fragment (size not known) of a buff-coloured Lower Palaeozoic sandstone found at or near Stonehenge.  The geologists seem pretty certain that it is from the Lower Palaeozoic, which means that it's probably Ordovician or Cambrian,  or could be Silurian (there are some Silurian sandstones in Pembrokeshire, in the central part of the county and on Skomer Island).  At the moment the money seems to be on NW Pembrokeshire as a source, and we await with interest the next Ixer / Bevins geological paper which might shed light on the provenance of this fragment and some other related fragments from Stonehenge.

Rhosyfelin and "spot provenancing"

 This is the "exact spot" from which a Stonehenge rhyolite bluestone orthostat is supposed 

to have been taken.......

Is it possible for geologists to provenance rock fragments found in one place to a locality a great distance away, with an accuracy of "a few square metres"?

As readers of this blog will know, Prof MPP claims to know exactly where at least one Stonehenge bluestone has come from, and he has pointed the spot out to many visitors to the Rhosyfelin dig site.  OK, you might say, he's just repeating what the geologists have told him.....

But hang on a minute.  If you read the papers by Ixer and Bevins rather carefully they are for the most part rather circumspect, and they are very cautious about making claims that might be difficult to sustain under close scrutiny.  So who's responsible for the hype here?  This is important, because the story of this "precise provenancing"  has been picked up by the media and by all sorts of august institutions like the Pembs Coast National Park and the Dyfed Archaeological Trust -- so the truth does become rather important.  So what are the facts?

Well, we have (according to a mysterious source) about 40-60 thin sections of rock samples from the Rhosyfelin - Pont Saeson area, and we can probably assume that there are an approx equal number of thin sections from the "foliated rhyolite" debitage in the Stonehenge area.  So do the matches match the hype?  Here we have a problem, because very few of these "Jovian fabric" slides have been published.  No problem with that, since no researchers ever publish ALL their data, and as Myris has reminded us, they try to publish slides that are "typical" or "representative" of the group as a whole.

The slides I have been able to find are reproduced below, with full acknowledgement to Richard Bevins and Rob Ixer and their colleagues.

 Rhosyfelin Location 8, near the tip of the rocky spur

 

 Point PS8 from Pont Saeson

 

 Point PS10 from Pont Saeson

 

OU18, from the Avenue at Stonehenge

 

Jovian fabric from Stonehenge samples -- sample STH08-738

 

Jovian texture -- sample from near the Heel Stone at Stonehenge

The top thin section -- actually representing the rocks at the tip of the spur at Rhosyfelin -- is the crucial one here, and what we need is something from Stonehenge that matches it almost exactly. 

The sample from the Heel Stone fragment is not all that good a match, because the black blobs look rather like tadpoles on that one  (excuse the scientific language.......).  The closest match is that of Sample STH08-738, but even that is not all that close, because the black blobs are less frequent and there is a sort of melted or fluidized look to the slide which is absent in the one from Rhosyfelin.  And the larger phenocrysts (right word?) are more prominent and texturally distinct at Rhosyfelin than they are in the Stonehenge sample.

Could the Heel Stone sample have come from another part of the Rhosyfelin crags, or is it matched to something further away?   Could OU18 have come from Pont Saeson PS10?  They do look rather similar.......

What we don't know at present is the extent of lateral variation in texture along a foliation plane, or the extent to which samples taken from the rock face at Rhosyfelin are representative of those rocks a metre or two "behind" the rock face, or higher up or lower down.  Maybe that info will be forthcoming in a future paper?

So on the evidence currently before us, M'Lud, I suggest that the case is not proven.  I do not see anything in the Stonehenge samples to convince me of an identical match.  Neither do we know how big a variation there is in the Stonehenge material.  Could the samples all have come from one or two stones that have been broken up, or could they have come from a much wider range of material in the Stonehenge landscape and transported by ice from the Rhosyfelin - Pont Saeson neighbourhood? Now there may well be other samples hidden away that we have not yet been shown.  But I suspect that if there had been "better" Stonehenge samples, we would have seen them by now.  On the principle of "Show, don't tell" may we have a look at any other thin sections that might help to convince us that there really is a match to "within a few square metres" between something at Stonehenge and something at Rhosyfelin?

 

Rhosyfelin - some geological questions

Jovian texture shown in thin section from a sample from site 8 near the tip of the Rhosyfelin spur (photo: Ixer and Bevins)

 Prof Mike Parker Pearson pointing to the exact site from which a rhyolite orthostat was taken away and transported to Stonehenge (photo: The Duke).  According to the photographer, "Even evidence of cutouts for wedges to be driven in to split the stone away from the face are visible. Awesome site."  So there we are then.

 In recent weeks I have visited Rhosyfelin in the company of more than a dozen glacial geomorphologists and have had some rather interesting discussions.  Most of them have raised one question which is worth sharing:  "What is the actual evidence which enables the geologists to claim that they have provenanced much of the rhyolite debitage found at Stonehenge to the very place where Prof MPP is standing in the above photo?"  That question relates in particular to the fact that there is not a particularly dense cover of sampling points across the landscape, and that great tracts of the Stonehenge landscape debitage haven't been sampled either.   Some of the visitors have read the literature, and they are intrigued by the sheer bravado of statements like these: 

"The overwhelming majority of the Stonehenge rhyolitic ‘debitage’, namely that belonging to Groups A-C, can be sourced from the Pont Saeson area and perhaps entirely from Craig Rhos-y-felin, but from more than one site on the crags."

"This is the first time that any lithics from Stonehenge have been unequivocally assigned to an area of a few square metres, namely to within a very small single outcrop or couple of outcrops; it may not be the last."

CRAIG RHOS-Y-FELIN, PONT SAESON IS THE DOMINANT SOURCE OF THE STONEHENGE RHYOLITIC ‘DEBITAGE’
Rob Ixer and Richard Bevins, Archaeology in Wales 50, pp 21-31

"The ‘rhyolite with fabric’ (almost all is Craig Rhos-y-felin rhyolitic tuff) and the ‘volcanics with sub-planar texture’ debitage are universally distributed within the Stonehenge Landscape." (from "Chips off the old block" by Ixer and Bevins)

".......... matching the distinctive ‘rhyolite with fabric’ debitage (first seen in Stone’s stones) from Stonehenge to very detailed sampling along the Welsh outcrop showed that rocks from the extreme north- east of Craig Rhos-y-felin (‘site 9’) were identical to Stonehenge rhyolites showing the 'Jovian’ texture. This suggests an almost impossible provenance of ten squares metres. The archaeologists were told where to dig. In September 2011, Professor Mike Parker-
Pearson of Sheffield University and his team cleared the vegetation from the northern end
of Craig Rhos-y-felin and excavated. They found, just a few metres from site 9, a large
proto-orthostat, a large joint block set for its journey to Salisbury Plain......." (As pointed out before, that should be "site 8".....)


Rob Ixer, Digging into Stonehenge’s past.  Mineral Planning, issue 143 / October 2012, p 13

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

As I have indicated before on this blog, I too have some doubts about the  confidence with which the geologists can cite the Rhosyfelin crag as "the dominant source" for rhyolite fragments found in the Stonehenge area.  So some more questions:

1.  Of the 1200 or so rhyolite fragments found in the Stonehenge landscape and looked at by the geologists, how many have been used for thin section analysis?

2.  What assurance do we have that the thin sections published are actually typical of the whole assemblage?

3.  How much of the Stonehenge landscape has been excavated (5% at most?), and how much of the Stonehenge monument itself has been excavated (50% at most?).

4.  How many rhyolite sites in the Pont Saeson -- Rhosyfelin -- Brynberian area have now been sampled, and how many of those have been used for the preparation of thin sections?

5.  Are there not other localities in the Pont Saeson area which have provided thin sections with "Jovian fabric" which are virtually identical with the one from locality 8 on the crag itself?

6.  Is there any evidence that suggests that all or most of the rhyolite debitage at Stonehenge comes from one or two destroyed orthostats?

7.  Have you considered the possibility that the "rhyolite with fabric" fragments found in some parts of the Stonehenge landscape (I use those words advisedly) have come from parts of the crags in the Rhosyfelin - Pont Saeson area that no longer exist, having been entrained by overriding glacier ice?

8.  How much variation is there in the fabric of the rhyolites across the 50 m or so of the exposed rock face?

9.  How much variation is there in the fabric as you go deeper into the cliff face and examine some of the the foliated rhyolites exposed side-on where cliff face sections have sheared away? 

10.  Have you sampled the "proto-orthostat", and can you identify exactly where on the crag it has come from?

None of this detracts from the very smart provenancing work that has been done.  It's just that several of us share concerns about some of the statements made and conclusions drawn.........  Apologies if some of these questions are already answered in some of the papers published!  Can't keep track of everything -- but repeat answers will be appreciated.

To find further discussions on this issue,  just put "Jovian fabric" into the search box.

A hundred standing stones at Durrington?

 

 Computer generated images of what the stones might have looked like before they were shoved over and buried. At present, there is no reason to think that they were anything other than standing sarsens -- and nothing to do with bluestones.  But one never knows......

“Everything previously written about the Stonehenge landscape and the ancient monuments within it will need to be re-written.......”   Now how many times have we heard that before?  Vince Gaffney and his team have gone into overdrive with their latest research announcement -- but this is interesting.  The revelations about 100 standing stones (and maybe a lot more) having once stood at Durrington Walls adds another component to another complex story on Salisbury Plain.  Further info awaited.  But for now, the media are full of it -- it will probably be all over the BBC News today.
---------------------

Stonehenge researchers 'may have found largest prehistoric site'

http://www.bbc.co.uk/news/uk-england-wiltshire-34156673

The find has been dubbed a "superhenge" because the site is five times the area of Stonehenge, as Victoria Gill reports

Standing stones found buried near Stonehenge could be the "largest" intact prehistoric monument ever built in Britain, archaeologists believe.

Using ground-penetrating radar, some 100 stones were found at the Durrington Walls "superhenge", a later bank built close to Stonehenge.

The Stonehenge Living Landscapes team has been researching the ancient monument site in a five-year project.

Finding the stones was "fantastically lucky", researchers said.

The stones may have originally measured up to 4.5m (14ft) in height and had been pushed over the edge of Durrington Walls.

The site, which is thought to have been built about 4,500 years ago, is about 1.8 miles (3km) from Stonehenge, Wiltshire.

The stones were found on the edge of the Durrington Walls "henge", or bank, an area which had not yet been studied by researchers.

Lead researcher, Vince Gaffney said the stones were "lost to archaeology" but found thanks to modern technology.

National Trust archaeologist Dr Nick Snashall said: "In the field that lies to the south we know there's a standing stone which is now the only standing stone, now fallen, that you can go up to and touch in the whole of the Stonehenge landscape," he said.

"It's called the Cuckoo Stone.

"If there are stones beneath the bank... they're probably looking at stones of pretty much the same size as the Cuckoo Stone."

Dr Snashall added there was a "sense" of one area set aside for the living and another for the dead at Durrington Walls - and that had changed over time.

The findings are being announced later on the first day of the British Science Festival being held at the University of Bradford.

================

Huge ritual monument found hidden near Stonehenge

http://www.telegraph.co.uk/news/earth/environment/archaeology/11844357/Huge-ritual-monument-found-hidden-near-Stonehenge.html

The super-henge of Durrington Walls has been hiding a secret for thousands of years. A huge row of megalithic stones buried beneath.

A new line of stones has been found under Durrington Walls super-henge

By Sarah Knapton, Science Editor

A huge ritual monument which dates from the time of Stonehenge has been discovered hidden under the bank of a nearby stone-age enclosure.

Durrington Walls, a roundish ‘super-henge’ has long puzzled archaeologists because one side is straight while the rest of the structure is curved.

As early as 1810, historian Richard Colt Hoare suggested that its shape had been left ‘much mutilated’ by centuries of agriculture.

But now ground penetrating radar has found that the straight edge is actually aligned over a row of 90 massive standing stones which once stood 15ft high, and formed a c-shaped arena which has not been seen for thousands of years.

The stone line, which curves into a c-shape towards one end, is likely to have marked a ritual procession route, and is thought to date from the same time as the sarsen circle at Stonehenge.

The earliest phase of Durrington Walls with its line of megaliths

Archaeologists believe the stones were pushed over and a bank built on top, but they are still trying to work out exactly why they were built. Nothing exists like it in the world.

“It’s utterly remarkable,” said Professor Vince Gaffney, of the University of Bradford. “It’s just enormous. It is definitely one of the largest stone monuments in Europe and is completely unique. We’ve never seen anything like this in the world.

“We can’t tell what the stones are made of, but they are the same height as the sarsens in the Stonehenge circle, so they may be the same kind.

“It was probably for a ritual of some sort, or it could have marked out an arena. These monuments were very theatrical. This a design to impress and empower.

“Not only does the new evidence demonstrate a completely unexpected phase of monumental architecture at one of the greatest ceremonial sites in prehistoric Europe, the new stone row could well be contemporary with the famous Stonehenge sarsen circle or even earlier.”

The completed super-henge after the stones were toppled over and buried under the right bank

Durrington Walls, which sits in a depression not far from the River Avon, near Amesbury, Wiltshire, is one of the largest known henge monuments, measuring around 1,640 feet in diameter and built around 4,500 years ago in the Neolithic, or new stone age.

It is surrounded by a ditch of up to 54ft wide and a bank of more than three foot high and is built on the same summer solstice alignment as Stonehenge. Some archaeoolgists have suggested that the builders of Stonehenge lived at Durrington. A nearby wooden structure, called Wood Henge was thought to represent the land of the living while Stonehenge represented the realm of the dead.

But the discovery of the stones suggests that Durrington Walls had a far earlier and less domestic history than has previously been supposed.

Durrington Walls is around 1.5 miles from Stonehenge

The Bradford archaeologists have been working alongside an international team of experts as part of the Stonehenge Hidden Landscapes project which has been mapping the entire area around with the latest technology.

“Everything previously written about the Stonehenge landscape and the ancient monuments within it will need to be re-written,” said Paul Garwood, Senior Lecturer in Archaeology at the University of Birmingham and principle prehistorian on the project.

The stones would have been as tall as some of those at Stonehenge

Dr Nick Snashall, National Trust Archaeologist for the Avebury and Stonehenge World Heritage Site, said the new results were providing ‘unexpected twists in the age old tale.’

“These latest results have produced tantalising evidence of what lies beneath the ancient earthworks at Durrington Walls. The presence of what appear to be stones, surrounding the site of one of the largest Neolithic settlements in Europe adds a whole new chapter to the Stonehenge story.”

The research will be presented at the British Science Festival in Bradford this week.

================

http://www.theguardian.com/uk-news/2015/sep/07/stonehenge-archaeology-ritual-arena-neolithic-monument

The World according to Molesworth

 One of Ronald Searle's sublime illustrations for the Molesworth books by Geoffrey Willans

I met somebody a couple of days ago who had just been to the Stonehenge Visitor Centre.  He had two main gripes -- one, that it cost a fortune for he and his family to get anywhere near the old ruin, and two, that there was only one narrative, represented as "the truth" -- involving, of course, the heroic carting about of bluestones by our heroic Neolithic ancestors.

Not having been to the new Visitor Centre, I can't comment on the accuracy or otherwise of the comments related to the narrative.  But it brought to mind some words from my "grate hero" Nigel Molesworth -- philosopher, social commentator, goriller of form 3B and destroyer of the English language.

On one of his daydreams (of which there are many), Molesworth transports himself back to the Middle Ages and imagines himself in an academy being taught (as usual) by an ignorant psychopath who should have been doing something else.  Pupil Molesworth puts up for a while with a lesson about the flat earth, and then, being a bright sort of fellow, explains patiently to the teacher, with reasoned evidence, that the earth is actually round.  The response of the teacher is to become furious and to give Molesworth six of the best, as a punishment for "having the temerity to disturb our ignorance....."

And that was the parable for today.

The Rhosyfelin "Revetment"

Ever since publishing Davey's report of last year's MPP talk at Castell Henllys, I have been wondering about what that "revetment" remark was all about:

http://brian-mountainman.blogspot.co.uk/2014/09/rhosyfelin-report-on-mpps-17th.html

Over the past winter, much of the site has been buried beneath that large black plastic sheet, but on going through my photos of last year's dig, I found some that I had overlooked.  Now it all makes sense -- well, sort of......

To quote Davey:

He was excited by what had turned up in the last few days of digging, firstly there was the forecourt at Rhosyfelin, there were slides indicating a shallow bowl containing rock clutter and in and around this he said that there were at least three standing stones, all packed at their respective bases by other smaller stones. The purpose of these standing stone was to act as fulcrum to stones being prised off the cliff face. The evidence being crush marks on the top of these stones.

He said that they had made a very important discovery, underneath that large slab in the foreground, they had found that it was resting on a man made terrace and in this terrace was upturned basket shaped lumps of earth and stone. He was particularly excited by these and the way he talked suggested that they were created in a similar fashion to making sandcastles on the beach.
 
He said that they had found the course of the river in the area of your picture and he said that there is a semi circular line of stones which was obviously man made, he described it as a revetment and went on say that it could once have been a jetty, not for putting these 2 ton stones on rafts to float down the river, it was obviously far too shallow, but to load on to sledges to carried further north.

Let's forget about forecourts, fulcrums and crush marks and put those down as products of a fertile imagination, but what about the "man-made terrace",  the "upturned basket-shaped lumps of earth and stone",  and the "revetment" or "sledge-loading jetty"?


Well the photo reproduced above, with and without my red markings, seems to explain at least some of the Prof's thinking.  The dashed lines show the position of the so-called semi-circular revetment presumed to have been used for the loading of 2 tonne stones (what about 8-tonne stones?) onto rafts or sledges.  I suppose this is what MPP means when he says he has found the old course of the river.  The solid red line shows a "route" marked out with string last year, presumably indicating the route that would have been used for dragging stones from the "quarry" to the loading facility.


Again, this is a quite wonderful archaeological artifice, created by the removal of all the fines and "inconvenient" stones from the "outside" of this magical quayside.  Before excavation, the grey and foxy-red fluvioglacial and alluvial sediments covered these big stones.


So now we have this glorious image of the loading crew sitting by the quayside, listening to the gentle murmuring of the waves, with their raft bobbing about gently in the shallows, as they wait for the next bluestone to be delivered by the quarrymen.........


I suppose this is why the 2015 dig might well concentrate on the valley floor, with a view to showing the world what the quayside and the old river bed might have looked like in the good old days.

Felindre Farchog enclosure

Apologies to Pembs Hist Soc -- I thought they were referring to an enclosure called Castell Mawr.  Probably it is this one, which is actually on the valley floor:

http://www.coflein.gov.uk/en/site/413007/details/FELINDRE+FARCHOG,+ENCLOSURE/

Thanks to Geo for pointing this out.  You can easily find it on Google Earth or "Where's the Path?"

So there will be some digging there in September -- I wonder if Castell Mawr has been abandoned?