The BM exhibition -- more dodgy statements

 

Thanks to Tim Daw and Tony Hinchliffe for flagging this up.  The famous "Boles Barrow Bluestone" found at Boles Barrow near Heytesbury, as illustrated and described in the current BM exhibition.  I suppose we are stuck with all the foreign rocks at Stonehenge being described as "bluestones" -- although it leads most people to the belief that there is only one rock type with this name, rather than the 30 or so "foreign" lithologies that are found there. 

Is it dressed?  That is a matter of debate --  in most of the literature it is referred to as "undressed" or in its natural state, albeit damaged, and a part of what must have been a much larger boulder.

Precise provenance unknown?  Well, it is disputed, but the consensus nowadays seems to be that it did indeed come from Boles Barrow, and that it was put there well before the stone monument at Stonehenge was conceived and built.  "It is very likely that it was part of the first monument at Stonehenge"  ??  I beg to differ.  

I have done many posts on the Boles Barrow stone.  Use the search box to find them........

The BM exhibition and the Stonehenge orthodoxy

One would have thought that a serious exhibition organized by -- among others -- the British Museum would have separated out the facts and the speculations.  But no -- speculations are presented as if they are facts over and again.  For example:

Mike Pitts on the BM blog site, going on about quarries, overland transport by tribal groups, and a "lost circle" built and then dismantled.  The orthodox narrative rules, and higher authority dictates that nobody should deviate from it by a single inch.  It's more than a little pathetic, as well as being completely dishonest :

Stonehenge is very unusual in the ancient world for the distances over which its materials were transported to the site, especially those megaliths we know as bluestones. Most of these, made from different types of igneous rock, were quarried in south west Wales – I estimate their journey at 220 miles.

.....we think the original bluestone structure was a large circle of 56 stones, raised five centuries before anything else. People could, if they’d wanted to (who knows?), have brought one stone to Wiltshire every year for 56 years – raising one could have been done entirely independently of any others.
 

https://blog.britishmuseum.org/how-was-stonehenge-built/?

Then a friend of mine posted this page, which I assume has come from the exhibition handbook or catalogue:

 

"Chemical analysis suggests that several lived and died in West Wales before their remains were interred within the monument...."

"Recent excavations at Craig Rhos-y-felin in SW Wales, one of the sources of the bluestones have advanced understanding of Stonehenge and the people who made it........"

That is all complete poppycock. I think I know the evidence pretty well, and those statements are false,  based upon fantasies and wishful thinking.  

It would be nice if the BM were to show a somewhat greater regard for science and hard evidence instead of simply wallowing in the mythology happily invented by Parker Pearson, Pitts and others.

Education, education, education...........

A couple of days ago I went up to Swansea University to give a talk on the bluestones to the local U3A group.  A  good audience, a lot of interest, and some really intelligent questions and discussion afterwards.

It was a particular pleasure to see in the audience Mike Bristow, my geography teacher when I was a kid in Haverfordwest Grammar School, 1951-59.  He's 92 now, and still going strong.  He's been living near Swansea for quite a few years. I owe him a huge amount -- it was he who introduced me to geomorphology and gave me my love of the landscape, and who taught me to question everything.  Scepticism is different from cynicism -- as I try to demonstrate on this blog.  Mike also taught me to trust in my own judgment, so long as it is based on a sound understanding of the nature of the evidence available.  Thank you Mike, for all that you gave to me and a whole generation of geography pupils long ago, in those days of innocence.......

Altar Stone confusion

A couple of nice photos from Myfanwy of Maenclochog, or whatever her name is today.   The top photo is of the surface of the Altar Stone at Stonehenge, and the bottom one which looks a bit similar but not all that similar) might come from the other Mill Bay, near Dale at the mouth of Milford Haven.  There are ORS rocks there, but they are not equivalent stratigraphically to the Senni Beds or the Cosheston Formation.  Since nobody now seems at all certain where the Altar Stone has come from, this  just adds to the confusion.

The new Altar Stone paper should not have been published

The Mill Bay area on the south shore of Milford Haven -- originally deemed to be the likely source area for the Altar Stone.  Now back in the frame?

I have been taking some advice on that strange recent paper by Bevins, Ixer et al, and it looks as if my concerns are shared by others who know far more about sedimentary rocks than I do.

https://brian-mountainman.blogspot.com/2022/05/the-altar-stone-may-not-have-come-from.html

I said that I was not convinced by the evidence presented or by the interpretations of the authors -- and others are prepared to be rather more brutal in their assessment.  This is a comment from an expert on pXRF work who prefers to remain anonymous:

"I have had a quick skim through the paper you attached and my general feeling is that the data are so compromised that I simply wouldn't have used them. Their understanding of XRF is sound, but the issues they have had with low totals and wet vs dry attenuation have forced them to be very selective in which data they accept and which they don't. In principle, it's certainly possible to acquire meaningful data for sandstones (the finer-grained the better), but the detector should be held orthogonal to a very flat dry surface (not laid on a tripod on an irregular wet surface) and the Ba, Sr, Ca etc could well be within clays and feldspars, rather than barytes and calcite. Such XRF is essentially a surface detection technique, so there is also the problem of weathering crusts to consider, not to mention burial within a chalk soil and whatever artefacts have been induced by archaeological processes and modern "witch" ceremonies!"

I also received a long analysis of the paper from Richard Thomas, who has himself been involved in Altar Stone work in the past.  These are some of his points:

1.  The authors make a series of assumptions used to bolster the claim that their methodology and results are valid. For example, although they do mention the "widely publicised concerns over the pXRF technique", they proceed to more or less ignore its documented shortcomings. What (very little) I know about pXRF is that it works best for essentially unweathered, compositionally homogeneous lithologies. It seems to me that there is no honest discussion here about whether pXRF is an appropriate technique for fingerprinting sandstones and determining their provenance. The authors use it and bingo, their results show it works. I would have liked to see them include some (non-ORS) sandstones as "controls" in their analyses. I'm very dubious about the utility of pXRF analysis for sandstone fingerprinting and provenance research.  (I share Richard's concerns about the lack of analyses of controls for comparative purposes. Sadly, that is a shortcoming of many other papers by the same authors.).  

2. Of course, the authors were 'forced' to use pXRF by English Heritage's stubborn refusal to allow a fresh sample (ideally a 1" core) to be taken from the actual Altar Stone -- from below the present ground surface (so it would be invisible to visitors) and then filled with concrete before reburial. Given the shenanigans that take place on every Summer Solstice at Stonehenge, which have included lighting fires on the Altar Stone, EH's attitude demonstrates a double standard to say the least.
 
3. Unless you are dealing with pure quartz arenites, the detailed composition of sandstones (at both large and small scales) is vertically and laterally variable. Source rock composition, the nature/energy levels/duration of the transporting mechanism(s) and subsequent diagenetic effects play key roles of course but, at a smaller scale, the interplay of stratification type (a product of bedform) and texture (i.e., grain size and sorting, combined with hydraulic equivalence) can generate significant local differences in sandstone mineralogy. For instance, heavy minerals can be concentrated at the toes of cross-bed foresets and micas (and other 'lights') in the troughs between ripple or dune crests. Even when conducting multiple analyses, if your analysis spot is only 8mm in diameter, such compositional heterogeneity has to be factored into pXRF sandstone data interpretation.
 
4. Bearing that in mind, I find it remarkable that this article contains NO descriptions of the grain sizes or other macroscopic characteristics of the samples, except (from Thomas, 1923) for the statement that the Altar Stone is a "grey-green micaceous sandstone". That in fact is my description; Thomas (1923) described its colour as "pale sage-green".

5. The conclusion that the Altar Stone and debris fragments are of essentially the same composition (p.6) is based on the values they obtained for "high atomic number elements" -- namely (table 4) Mn, Sr, Zr, Mo, Pb, Th and U, which presumably are in large part a reflection of the samples' heavy mineral assemblage compositions. Do the samples contain heavy mineral laminae? Lacking a macroscopic description of these sandstones we cannot tell  figure 5 is of no help in this regard).
 
6. Are the authors correct in concluding that the rock fragmentss they analysed came from the Altar Stone? I'm sceptical and, at best, think more substantive evidence is required. However, even if they are right, I believe that any definitive study of the Altar Stone's provenance must be based on samples taken from the Altar Stone itself, not small, proxy specimens. In my opinion, any such provenance study has to begin by thoroughly documenting the Altar Stone's macroscopic characteristics followed by detailed thin section analysis. As I've noted before, thin sections can be a wonderful source of information about a sandstone's original compositional and textural characteristics and its subsequent diagenetic history. The authors here are enamoured with high-tech analytical techniques but are in danger of neglecting the fundamental building blocks of any sandstone provenance work. (NB. Way back in 1973 (!) I noted that the visible portion of the Altar Stone was a fine-grained, muscovite-rich, small-scale trough cross-laminated, grey-green sandstone that appears similar to a number of such sandstones found within the Lower ORS sequence of South Wales. Its largest surface is bedding parallel and stratigraphically, the block appears to be lying right way up.)
 
7. There is still a discussion about the petrographic description of the Altar Stone given by H.H. Thomas in his classic 1923 paper;  was it really based upon a thin section taken from the Altar Stone itself? Not everybody accepts that, but I prefer to give my namesake the benefit of the doubt.

8. Since they found barite in an Altar Stone proxy sample (FN 196) using SEM-EDS (see Bevins et al., 2020; and figure 5 of this new article), the authors seem to have become obsessed with its importance in unravelling the provenance of the Altar Stone. Perhaps they're right, but I'm a bit dubious about that since, with a maximum modal content of 0.8% BaSO4, it is still just a trace mineral. I think other, more obvious characteristics will prove to be of greater value. For their pXRF data presented in table 5, the authors assume all Ba to occur as barite but (as they grudgingly acknowledge in the table caption) it seems far more likely to me that the Ba is actually present within K-feldspars, micas and clay minerals (e.g., illite).

9. To be frank, I found the "Altar Stone and ORS comparisons" section to be laughable. I don't think anyone with a reasonable level of knowledge of the ORS sections of South Wales and the Welsh Borderlands and familiarity with the Altar Stone, would expect it to be derived from any formation other than the Senni Formation or its lithostratigraphic equivalents. Provenance studies should be about comparing like with like. It would be shocking if the Altar Stone (proxies) and samples from the other ORS formations listed in table 1 did not exhibit major compositional differences. Based upon just 3 samples from the Mill Bay Formation, Bevins et al. (2020) ruled out the Cosheston Subgroup as a source for the Altar Stone. Without further study however, I believe this conclusion to be premature since the Burton Cliff and Llanstadwell Formations both contain some thick, grey-green sandstone units. Again, I may be proven wrong, but I fully expect the source of the Altar Stone to turn out to be a Lower ORS Senni Formation-related sandstone unit from South Wales.

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

So there we have it.  It does not look as if the specialists in pXRF work or the specialists in ORS / Devonian rocks are going to be very impressed by this paper, and it probably should not have been published.  We still cannot take it that the fragments analysed by the authors actually did come from the Altar Stone; and we cannot take the main conclusions of this paper as reliable.

The origin of the Altar Stone is as mysterious as ever -- notwithstanding the contents of this new paper, it still appears probable that it came from somewhere in the ORS Welsh sequence, with the balance of possibilities tending towards the Senni Formation.  But who knows?  Maybe it did, after all, come from the shores of Milford Haven?   Now that would be fun, wouldn't it?

https://brian-mountainman.blogspot.com/2020/07/the-mill-bay-samples.html

The message from all of this?  The provenancing of the Stonehenge bluestones is not very easy at the best of times, and a lot of the work over the past 20 years by Bevins, Ixer and others (which should have been strictly geological) has been spoiled by contacts with the archaeologists that have been far too close for comfort.  There has been an ongoing quest for spectacular results and banner headlines linked to quarries and "lost circles".  Over and again, the quality of the science has been compromised.  As I have said repeatedly on this blog, there have been too many assumptions and distortions, and too many ruling hypotheses........

Those Stonehenge landscape pits -- and yet another ruling hypothesis

The 415 large pits investigated, using various techniques.  Many more smaller pits are not shown on this map.

I have been reading this article about pits and hollows rather more thoroughly.  It's not an easy read, since the authors use highly convoluted language when much simpler language would have done the job perfectly well...........  This is the reference:

Journal of Archaeological Science
Available online 9 May 2022, 105557
De Smedt et al
"Novel insights into prehistoric land use at Stonehenge by combining electromagnetic and invasive methods with a semi-automated interpretation scheme."

https://doi.org/10.1016/j.jas.2022.105557

Anyway, I have come to the view that the article is completely devalued because the authors have looked at hundreds of pits and hollows across the landscape, using electromagnetic surveys, boreholes and excavations and have recognized that some of them are probably tree throws, solution hollows or shallow "quarrying pits" used for the extraction of clay or building rubble or maybe even flint nodules.  They were heavily focussed on trying to decide which of the pits (especially the larger and circular ones) might have been "anthropogenic" and which might be explained by social factors, with concentrations or clustering in settled or "special" areas.  But the whole research project, as far as I can see, is based upon the assumption that all of the monoliths at Stonehenge were imported from far away.  They do not even mention the possibility that some -- let alone all -- of the sarsens and bluestones might have been collected up in the very area they were examining.  It may well be that more than a hundred pits and hollows across this landscape are the very places from which sarsens and bluestones were extracted for use in the Stonehenge stone settings.  That, as an hypothesis, should have been mentioned and it should have been examined.

There is very little analysis here of the sediment fills in the examined pits -- this is unfortunate, because I would have liked some detailed information regarding the nature of the sediments that might have been associated with extracted or removed large lumps of stone!

The radiocarbon dates obtained from organic materials in the examined pits were preferentially obtained for the big pits that were assumed to be anthropogenic.  They ranged from the Mesolithic to the late Bronze Age, but no particular pattern or consistent story could be discerned.  The authors note that they obtained hardly any radiocarbon dates for the Neolithic and the early Bronze Age -- which might have coincided with the construction of Stonehenge.  All of the radiocarbon dates have come from the selected features which were assumed to be significant -- so there is a very powerful sampling bias in the results.

An opportunity lost -- once again, because of a flimsy and unsupported belief in the long-distance transport of monoliths from far away, as specified in the EH Stonehenge Bible.  What a pity.......  nice work, but wrong question.

Stone sockets in the Stonehenge landscape?

 

There is some press coverage today of new research by a Belgian / UK  team using geophysical methods to identify sub-surface irregularities including some quite deep pits.  I'm trying to get hold of a copy of the paper, which is behind a paywall.  The authors talk about large pits, smaller pits and "natural features" -- and of course there is some speculation in the media about animal trapping pits in the days before Stonehenge was built. 

What intrigues me is the question "Could there be stone extraction pits and hollows among the thousands of surface irregularities discovered?" -- but the Abstract gives no clues on this.  I'm rather intrigued by semi-automated interpretations and only 66% accuracy, but await further info.

Watch this space.......... 

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

"Novel insights into prehistoric land use at Stonehenge by combining electromagnetic and invasive methods with a semi-automated interpretation scheme."
Philippe De Smedt, Paul Garwood, Henry Chapman, Koen Deforce, Johan De Grave, Daan Hanssens, Dimitri Vandenberghe.
Journal of Archaeological Science
Available online 9 May 2022, 105557

https://www.sciencedirect.com/science/article/abs/pii/S0305440322000152?via%3Dihub

Abstract

Geophysical survey methods have led to high-resolution mapping of subsurface remnants of ancient landscapes at continually expanding spatial scales. Yet, particularly when applied across entire archaeological landscapes, spanning hundreds of hectares, resultant datasets provide little direct information about inhabitation, environments or change over time.

Focusing on a 2.5 km2 area around Stonehenge, we show how geophysical soil survey, when combined with targeted sampling and excavation, can enable reliable empirically-grounded identification of complex activity traces. Particular focus lies on anthropogenic dug pits, identification and interpretation of which are vital in European earlier prehistoric archaeology due to their close connection with inhabitation and ceremonial practices. By integrating frequency domain electromagnetic and invasive datasets, and using a semi-automated interpretation scheme, we identified previously unknown concentrations of large pits (with diameters >2.4 m) among several thousand smaller pits and natural features across the Stonehenge landscape. Excavations of a subset of identified features demonstrate that, in this area, our investigative methodology is 66% accurate for identifying large anthropogenic pits. Our results have significant implications for understanding Stonehenge and its landscape setting, revealing elusive forms of Mesolithic to later Bronze Age land use that - even within the world's most intensively researched archaeological landscape - have gone unrecognized until now.

These findings underscore both the crucial role of archaeological excavation as an essential basis for reliable interpretation of geophysical data, as well as the perils of inductive visual interpretation of features’ morphologies and their spatial configuration in non-invasive survey data.

Unmapped dolerite outcrops

 On the River Clydach, which flows across our land, there are a number of white-water cataracts, and from careful observation I can say that each one coincides with a small dolerite sill.  The quieter stretches in the river coincide with the areas of Ordovician shales.    This is an obvious relationship -- but the interesting thing is that the dolerite sills are not shown on the BGS definitive map, and neither are a number of rhyolite outcrops in the area.  All we see is a single large dyke up to 200m wide.  So the "micro geology" of the area is not very well known, except in areas like Tycanol Wood where mapping was done in detail as part of a doctorate project.   The same is true of most of North Pembrokeshire, including Mynydd Preseli where extensive moorlands make the defining of geological boundaries very difficult.  At one stage I was quite good at geological mapping, but where there are no outcrops at all to work with, one has a problem........

That's why I have always had a problem with Richard Bevins and Rob Ixer, who claim to know that certain spotted dolerite monoliths at Stonehenge have come from Carn Goedog and that certain bits of the foliated rhyolite debitage at Stonehenge have come from Craig Rhosyfelin.  Even more staggering, they claim to have identified the source of one fragment sample to "within a few square metres" on the Rhosyfelin rock face.  They have no perfect sample matches, but since they believe that there were bluestone quarries at both Carn Goedog and Rhosyfelin, scientific objectivity has been replaced with a degree of complacency which has attracted a few unmentionable comments from other geologists.  The main thing that worries them is that Ixer and Bevins do not know enough about the local geology to say with any certainty that their spotted dolerite and rhyolite samples at Stonehenge could not have come from anywhere else.

I was reminded of this a few weeks ago when I was hunting for the spotted dolerite source of the boulders scattered about near Glanyrafon, Crosswell.  When I get over this Covid bug, I will go for a walk and have another hunt.  Suffice to say that there are still spotted dolerite sources out there, waiting to be discovered........

Parker Pearson's myth is unravelling...........

I'm rather intrigued by the  fact that since the publication of the new Altar Stone paper on 22 March, there has not been the slightest mention of it in the media.  This means that no press release was issued, and this in turn means that the authors do not particularly want any press scrutiny.  Perhaps we should not be too surprised, because researchers do not like admitting that their earlier research proposals and conclusions have been wrong.  (They should be delighted about it, since that is how science works...... but that's another matter.)  Anyway, having encouraged MPP to go on at great length, in a number of publications, about the "A40 Altar Stone haulage route" they are now quietly having to back off on that one, and admit that they really have no idea where the Altar Stone might have come from. (See press item below, from 2020)

This is another huge setback for Parker Pearson, who has always been far too quick to create elaborate narratives based on no evidence whatsoever..........

This is not turning out to be a good year for MPP.  First, he had to admit that the evidence from three years of digging at Waun Mawn had not provided any satisfactory evidence that there ever was a partial dismantled  "lost stone circle" there, let alone a complete one.  Now he has to admit that the proposed bluestone haulage route via Brecon and Abergavenny also has to go onto the bonfire of the vanities. Whatever next?   I keep on telling him and his cronies that there are no bluestone quarries either, but sadly, at the moment, they are not inclined to accept my impartial advice, sincerely offered.  Give them time.  They will get there in the end, having bamboozled the media and the general public for far too long with their pseudo-science and their fantastical narratives.

I have expressed scepticism about some of the Altar Stone work in the past:

https://brian-mountainman.blogspot.com/2018/12/new-paper-on-altar-stone-or-is-it.html

and indeed, Bevins and Ixer and their colleagues have themselves expressed (some years ago) the view that the presence of barite cement in "Altar Stone samples" might mean that those samples did not come from Wales at all.  

https://brian-mountainman.blogspot.com/2020/07/geological-notes-on-altar-stone-paper.html

Geologist Richard Thomas has also expressed his concerns about the "matching" of sandstone fragments at Stonehenge with the Altar Stone and the assumption that they all came from a common source in Wales.  It will be interesting to see what he makes of the new data.  Previously, the geologists have discussed garnets in sandstone samples as being key to the provenancing work -- and now barite is clearly in the frame.

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

In 2020, a big press release.  This time, silence.......

Stonehenge's huge blocks DID arrive over land as archaeologists debunk theory the Neolithic slabs were rafted from Wales to Salisbury Plain
• Archaeologists may have debunked a theory on how the slabs were transported
• Using chemical analysis they found the stones came from near Abergavenny
• This means it is unlikely that the stones were taken on rafts on the Bristol Avon

 
By DAILY MAIL REPORTER
PUBLISHED: 23:29, 1 July 2020 | UPDATED: 23:29, 1 July 2020 

It is one of the mysteries of the Neolithic Age – how Stonehenge was created.
Now archaeologists may have debunked the theory that giant slabs of stone were rafted from Wales to Salisbury Plain.
Using chemical analysis, they have matched the six-ton sandstone ‘altar stone’ from Stonehenge to rocks near Abergavenny, just a few miles from the English border.
This finding leads them to believe the boulder was carried across land, in a route roughly following the A40 trunk road that connects Wales with London today.
This could debunk the theory that Stonehenge’s bluestones were taken south to Milford Haven and put on rafts or slung between boats, paddled up the Bristol Channel and along the Bristol Avon to Salisbury Plain.
Dr Rob Ixer, from University College London, who co-authored the study published in the Journal of Archaeological Science, said: ‘This totally destroys the raft theory, it blows it out of the water.
‘This is our second re-examination of the bluestones, but it is our first major finding.’

The Altar Stone may NOT have come from Wales

ORS outcrops and (marked by triangles) the locations of ORS beds sampled and used for comparative purposes with the Altar Stone surfaces and with associated debitage fragments at Stonehenge.

A friend attended a talk by Richard Bevins the other day, at which he highlighted this latest piece of research on the Altar Stone:

"Linking derived debitage to the Stonehenge Altar Stone using portable X-ray fluorescence analysis."
Richard E. Bevins, Nick J.G. Pearce, Rob A. Ixer, Stephen Hillier, Duncan Pirrie and Peter Turner
Mineralogical Magazine (2022), 1–13
doi:10.1180/mgm.2022.22
Published online by Cambridge University Press: 22 March 2022


https://www.cambridge.org/core/journals/mineralogical-magazine/article/linking-derived-debitage-to-the-stonehenge-altar-stone-using-portable-xray-fluorescence-analysis/23E9A00C0C2B9FAC0BC74AC11AAE5B2D

Abstract

The Altar Stone at Stonehenge in Wiltshire, UK, is enigmatic in that it differs markedly from the other bluestones. It is a grey–green, micaceous sandstone and has been considered to be derived from the Old Red Sandstone sequences of South Wales. Previous studies, however, have been based on presumed derived fragments (debitage) that have been identified visually as coming from the Altar Stone. Portable X-ray fluorescence (pXRF) analyses were conducted on these fragments (ex situ) as well as on the Altar Stone (in situ). Light elements (Z<37) in the Altar Stone analyses, performed after a night of heavy rain, were affected by surface and pore water that attenuate low energy X-rays, however the dry analyses of debitage fragments produced data for a full suite of elements. High Z elements, including Zr, Nb, Sr, Pb, Th and U, all occupy the same compositional space in the Altar Stone and debitage fragments, and are statistically indistinguishable, indicating the fragments are derived from the Altar Stone.  Barium compares very closely between the debitage and Altar Stone, with differences being related to variable baryte distribution in the Altar Stone, limited accessibility of its surface for analysis, and probably to surface weathering.

A notable feature of the Altar Stone sandstone is the presence of baryte (up to 0.8 modal%), manifest as relatively high Ba in both the debitage and the Altar Stone. These high Ba contents are in marked contrast with those in a small set of Old Red Sandstone field samples, analysed alongside the Altar Stone and debitage fragments, raising the possibility that the Altar Stone may not have been sourced from the Old Red Sandstone sequences of Wales. This high Ba ‘fingerprint’, related to the presence of baryte, may provide a rapid test using pXRF in the search for the source of the Stonehenge Altar Stone.

Conclusions

We tested the potential link between debitage fragments from excavations at Stonehenge identified visually as being derived from the Stonehenge Altar Stone by pXRF to ascertain if the vis-ual link was valid. The Altar Stone was analysed in situ on a wet morning following a night of rain, contrasting with the ex situ, dry setting for the debitage fragments. Accordingly, the surface of the Altar Stone at the time of analysis was wet. This caused attenu- ation of the signal for light elements (below Z=37). However, strong correlations for elements above Z = 37 leads us to conclude that the fragments were indeed derived from the Altar Stone. This shows that even though there are widely publicised concerns over the pXRF technique, in this case it did provide a credible geochemical comparison between the derived fragments and source monolith and highlights the value of the technique in this particular archaeological context. In addition, being a non-destructive technique, it does not compromise the integrity of the ancient monument.

Having matched the derived fragments to the Altar Stone we are now in a position to interpret with confidence the data obtained to date on the derived fragments in the search for the source of the Altar Stone. The pXRF results showed the Altar Stone to have high Ba contents which is in agreement with the high modal % baryte identified previously using automated SEM-EDS analysis. This rather unusual mineralogy will be a key element in our search for the origin of the Altar Stone.

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

We have known about this research for some time -- and indeed it has been obvious for years that pXRF analyses had to be done on the Altar Stone exposed surfaces.  So it's good to see the research published at last.  Thankfully, this is a straight geology paper unsullied by any archaeological speculation about stone transport mechanisms or haulage routes.  

I need to read the paper more carefully, but for me the stand-out features are as follows:

1.  It now seems probable that the fragments at Stonehenge assumed to have come from the Altar Stone did indeed come from it -- but as far as the specialists are concerned, I suspect that the jury is still out.  The researchers had a problem in that their sampling work on the exposed surfaces of the Altar Stone was done in extremely wet conditions, whereas the fragments were studied dry.  To the untrained eye (such as mine) there seem to be substantial differences between the mineralogy of the fragments and the stone surfaces (Figure 3) -- and I was not all that convinced by the convoluted arguments in the text which put the differences down largely down to wet / dry sampling errors.

2.  Having promoted very heavily the idea that the Altar Stone came from the Senni Beds somewhere in mid Wales or the Welsh Borders, Bevins, Ixer and their colleagues now seem to have abandoned that idea altogether. That's quite a lesson for them and for everybody else as well -- the provenencing of erratic boulders (or Stonehenge bluestone monoliths) is only as good as your sampling density allows it to be.  As I have agued over and again, there is no way that Bevins and Ixer have provenanced spotted dolerite monoliths to Carn Goedog or foiliated rhyolite fragments to Rhosyfelin, because they still do not know where all the outcrops are.

3.   All this throws the provenencing of the Altar Stone up into the air again, with the intriguing possibility that it might actually be rather local -- having come, quite possibly, from no further away than Frome............

Waun Mawn and the de-stoning of pasture land

 

I was looking at some old posts, and came across a comment by Paul Sambrook to the effect that the "pits" at Waun Mawn (which are deemed by MPP and his merry gang to be bluestone monolith sockets) look to him and other archaeologists to be hollows from which inconvenient stones have been removed during pasture clearance work.

That interpretation looks more and more attractive.  For a start, the depths and widths of the "sockets"  are all wrong, as pointed out by Mike Pitts last year.   See the above diagram published originally on Twitter.   The hollows are of all shapes and sizes -- and indeed they are very difficult to measure at all, since they are not at all clearly defined.  They are not neatly spaced, or located accurately on the circumference of the putative "lost circle of Waun Mawn."  And the radiocarbon dating is chaotic, suggesting to me that if any stones have been removed they have been taken away at different times -- which is exactly what you would expect of pasture land clearance work.

Well, MPP has of course admitted that there probably never was a "lost stone circle" at Waun Mawn, even though there may have been an intention to build one.  So that's all right then...........

The tragedy is that so many people still believe the nonsense trotted out in that appalling Alice Roberts TV show.   Nice story -- who needs evidence anyway?

https://brian-mountainman.blogspot.com/2022/01/lost-bluestone-circle-did-not-exist.html

https://brian-mountainman.blogspot.com/2021/09/the-glorification-of-waun-mawn-with.html

https://brian-mountainman.blogspot.com/2022/02/more-waun-mawn-sceptics.html

Part of the excavation at Waun Mawn. If you are keen enough, you can say that there are two "bluestone monolith sockets" here, but they are shallow, irregular and in the wrong places.  The hollows are much more likely to be natural features exaggerated by the selective removal of sediments by the archaeologists -- as has also happened at Rhosyfelin and Carn Goedog.  The pits may also have been formed when inconvenient stones were removed during the ongoing process of improving pasture land.

Another of the hollows at Waun Mawn described as a bluestone socket.  It's too shallow, too small, and  appears to be an "excavation artefact"..........

Thought for the day

When I was a college student, my tutor Paul Padget (a self-effacing man with a brilliant mind) said to me one day:  "If you become a teacher, remember that your function is to ensure that your students become more knowledgeable, and wiser, than you are yourself."  

I rather liked that....... and once a teacher, always a teacher.........

I have always tried to hold fast to that ambition -- and that's what drives me to put  hard info, critical scrutiny and developing hypotheses onto this blog..........

Irish Sea till at West Angle

 

On going through my notes from a few years ago, I discovered a reference to a "wonderful exposure" of clay-rich Irish Sea till immediately to the right of cutting B as shown on the above diagram.   Most of the till exposed at West Angle is reddish in colour and has a sandy and even gravelly matrix, but in the chance discovery of this exposure in the gully that runs down to the beach, I saw "classic" Irish Sea till with a high clay content, reminiscent of the tills at Druidston and Abermawr.  There were many fragments of ORS incorporated, including striated pebbles, and there were also lignite and shell fragments as at Abermawr.  Unfortunately I had no time to collect samples.

This reinforces the view that this till is of Late Devensian age.  It's the southernmost exposure of the Irish Sea till on mainland Pembrokeshire, but there are other exposures further south, on the foreshore at Amroth and Freshwater West.  

Porthmelgan Irish Sea till exposure

 

The discontinuous exposures of glacial and other deposits at the head of Porthmelgan bay.  They are difficult to interpret because of slumping.

Porthmelgan is a small bay between Whitesands and St David's Head.  I spent a lot of time here in the course of my doctorate research in 1963 and 1964, and I was intrigued by the somewhat unusual "boulder bed" interbedded in the Irish Sea till.  Others might have interpreted it as representing an interval between two glacial phases, but I cannot see any weathering horizon or other unconformity, and conclude that it is simply made of a broken mass of bedrock (from the gabbro exposures on the headland) which has been incorporated into the basal layers of the ice and hence into the sticky clay till layers accumulated by lodgement.  The boulders are mostly sub-angular, so they appear not to be related to the boulder bed above the raised beach in Whitesands Bay.  I would describe them as typical glacial erratics that have not travelled very far.

There are some far-travelled erratics in the till, claimed by Cox to have come from Scotland and Antrim.

I plan to go back and take another look.......

Gower Society: the Limeslade Erratic

 

I have just received this from the latest edition of the Gower Society Newsletter.  There is considerable interest among members in Phil's discovery.

We are a bit frustrated because the samples from the erratic are still in the queue waiting to be analysed -- the lab has a lot of work in hand at the moment.  Eventually all will be revealed. Actually, I am sublimely unconcerned about the provenance of the erratic -- I don't really care where it has come from.  The most important things are already established -- namely that large erratic blocks were transported up the Bristol Channel during at least one glacial episode, and that the Irish Sea Ice stream was powerful enough to impinge upon the Gower coast in spite of the conflicting pressure from Welsh ice which flowed down the valleys of the Neath, Tawe etc from the western Coalfield and the Black Mountains.  If the Irish Sea ice stream was capable of doing that, it was certainly also capable of reaching Somerset and even Wiltshire.