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....
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Friday, 20 May 2022

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.

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.......

Thursday, 19 May 2022

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.

Tuesday, 17 May 2022

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.

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?

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........

Monday, 16 May 2022

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."

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.

Wednesday, 11 May 2022

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


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.

Friday, 6 May 2022

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........