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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Wednesday 1 June 2022

The Stonehenge Bluestones -- we still do not know where any of them came from

The other day a rather academic visitor to my Bluestone Museum asked:  "But don't we now know exactly where all the bluestones came from?"   So I patiently explained for him what the reality is when you ignore the media hype and look at the evidence..........

Over the last decade or so, the intrepid geologists Richard Bevins and Rob Ixer have published scores of learned papers and popular articles relating to the provenencing of the Stonehenge bluestones and the bluestone components of the ”debitage” in the Stonehenge landscape. Their work, highly professional and technical though it is, has been underpinned by two very dodgy assumptions:

1. That the glacial transport of the bluestones broadly from west to east could not have happened.

2. Therefore the monoliths (and the fragments in the ground) must have been transported by Neolithic or Bronze Age tribesmen from sites (quarries) which it must be possible to locate on the ground.

These assumptions date all the way back to HH Thomas in 1921, and are essentially unchanged over the course of a century in the minds of some academics — although it should be pointed out that among earth scientists the consensus has always favoured the glacial transport hypothesis. The assumptions of course also underpin the "great British myth"  of our heroic Neolithic ancestors struggling, against all the odds, to shift 80 or so special stones from West Wales all the way to Salisbury Plain, all for a reason that nobody has quite worked out.  

Part of the problem with the Ixer / Bevins work is that it has been very closely tied in with the work of certain archaeologists (and in particular Mike Parker Pearson) who have been intent, for the last decade or so, in proving their ruling hypothesis that there are Neolithic bluestone quarries out there, waiting to be discovered.  Ixer and Bevins have accepted this ruling hypothesis, which means that they have lost objectivity and have compromised their own integrity and reputations -- as pointed out to me by several professional geologists who have read their papers.  Some of those papers are published in peer-reviewed geological journals,  but the great majority are in archaeological journals, some of which are colourful and glossy "popular science" magazines that are not peer reviewed.  And it is statement of the obvious that the referees for archaeological journals will not know very much about geology and will allow assorted outrageous pieces of geological over-interpretation to pass unnoticed.

The other big issue is that of joint authorship.  Much of the Ixer / Bevins work is published in papers co-authored with up to a dozen of the archaeologists in the MPP team.  That means that the papers are probably written by MPP himself. with certain sections contributed in draft form by colleagues and then incorporated into the finished article by the lead author himself.  So many of the discussions, interpretations and conclusions in the final printed product may or may have been written or approved by our heroic geologists -- but they are stuck with them because the principle of "corporate responsibility" applies. 

Another problem that the geologists have had is that for reasons not entirely of their own making they have done very little fresh fieldwork in North Pembrokeshire, apart from some visits to "targetted" locations to collect some additional rock samples.  So they have concentrated their efforts on existing collections of rock samples from the Stonehenge bluestones, or on thin sections in existing collections.  Sometimes they have used thin sections found in dusty boxes in assorted museums and private collections, but which have previously not been described or interpreted in the literature.  Not all of these samples have been adequately labelled.  One might say that the historic bluestone sample collections have now been worked to death........... and that it is high time to move on.

In the absence of a systematic new Stonehenge sampling programme (for which EH and the site authorities are to blame), there is a powerful bias in the geological work, with results assumed by Ixer and Bevins to be of "Stonehenge significance" which may actually be local aberrations, dependent upon a specific excavation some time in the past.  Over and again I have had to point out to the geologists that they cannot talk about the relative abundance of certain rock types at Stonehenge, because less than 50% of the surface area of the stone monument has ever been excavated.  In the scramble to find spectacular results, there has been far too much over-interpretation.

So what about the "detailed provenancing work" which has so excited the archaeologists and the media?  Well, it just does not stack up.  Let's look at the key sites:

Carn Meini, with its litter of spotted dolerite monoliths and slabs.  on nthe right, the local "Altar Stone"......

1.  Carn Meini (Carn Menyn).   This was considered by HH Thomas and many other early workers to be the most likely source of the spotted dolerite monoliths at Stonehenge.  This was accepted by Darvill and Wainwright, who claimed that there was a Neolithic quarry there.  I have always disputed that, but with regard to the petrology of the rocks, Ixer and Bevins claim to have shown that the spotted dolerites at Stonehenge did NOT come from Carn Meini.  Tim Darvill has refused to accept that judgment, and I must say that I have sympathy with him since the Carn Meini - Carn Gyfrwy igneous intrusion is a very large one with a great range of dolerite types contained within it.  Some of the dolerites are very spotted and some seem to have virtually no spots.  Until the intrusion has been sampled much more systematically and comprehensively, the jury is still out.  In any case, there is no quarry. 

 Rhosyfelin -- lots of quarrying and very selective stone removal -- all done by the archaeologists.

2. Craig Rhosyfelin.  Ixer and Bevins claim to have matched some of the foliated rhyolite samples from Stonehenge (but NOT any of the monoliths) to "within a few square metres" on the basis of the peculiar "Jovian fabric" displayed.  I have always disputed that assertion, since there are no identical sample matches.  One of the Stonehenge samples is similar to one of the Rhosyfelin samples -- but it is not identical, and Ixer and Bevins have no idea what the extent of the characterised Rhosyfelin layer actually is across the local landscape.  The samples taken from Stonehenge might have come from the Rhosyfelin crag, or it might have come from another site one or two kilometres away.  The pure geological assessment has clearly been coloured by the conviction that there is a Neolithic bluestone quarry here, and it is thus devalued.  There is no quarry.  (The additional and extravagant assertion by Parker Pearson that he has identified the "extraction point" from which one of the Stonehenge rhyolite monoliths was taken makes no sense at all when one looks at the morphology of the rock face, and it should be ignored.)

Carn Goedog -- a classic Pembrokeshire site for viewing glacial and periglacial phenomena

3.  Carn Goedog.  The spotted dolerites are the most abundant of the bluestone rock types represented in the Stonehenge bluestone monolith assemblage.  Following studies of a number of samples from the tor, and spotted dolerite samples from Stonehenge, Ixer and Bevins have declared that Carn Goedog is the "most likely source" of the materials found in the ancient monument.  But the petrology and the geochemistry of the examined samples show considerable variations, and again there are no perfect matches.  Carn Goedog is a big tor, and most of it is still not sampled -- and the parent intrusion stretches over a wide tract of countryside.  The dolerites within it vary considerably.  I am still convinced that there are unmapped spotted dolerite outcrops on the north flank of Preseli.  So no matter what archaeologists may claim about Carn Goedog being the definitive source of the Stonehenge spotted dolerites, that is not what the geology shows. The conclusions about spotted dolerite provenancing are all underpinned by the faulty presumption that this is the site of a Neolithic quarry.

Cerrig Marchogion -- the petrified remains of the fallen Knights of King Arthur. Some spotted dolerite and some unspotted.
4.  Cerrig Marchogion.  This set of small outcrops on the Mynydd Preseli upland ridge has come into the frame recently with claims by Parker Pearson and his colleagues that the unspotted dolerites on Waun Mawn have probably come from here.  I am mystified by this, since no geological provenancing evidence has been presented in the literature, and since there are other unspotted dolerite outcrops far closer to Waun Mawn which the geologists appear to have been ignorant of.  A little fieldwork would have come in handy.  More confusion is added when in some articles Carrig Marchogion is shown as an unspotted dolerite source and in others it is shown as a spotted dolerite outcrop.  In fact, as in all other cases, there is considerable lithological variation within thye Cerrig Marchogion intrusion.  There is no firm evidence in the literature that any of the Stonehenge monoliths -- or any of those on Waun Mawn -- have come from here. And there is certainly nothing that might be construed as a quarry.

The Altar Stone -- much photographed but never properly examined.

5.  Altar Stone.  As we all know, for many years it was assumed that the Altar Stone had come from the Cosheston Beds (ORS) in Mill Bay, on the south shore of Milford Haven.  A large band complex narrative has grown up around it!  But then Ixer and Bevins, basing their research on fragments and thin sections assumed to have come from it, claimed that it was not from Mill Bay at all, but from the Senni Beds, possibly in the Brecon Beacons or the Welsh borders.  But then, in the most recent research (based on pXRF work) just published, they have thrown doubt on that earlier assertion -- and it looks as if Mill Bay is back in the frame.  Or maybe the Altar Stone has not come from Wales at all.........  There are a number of serious problems with the ongoing research.  The main one is that we still do not know whether the fragments assumed to have come from the Altar Stone are actually linked with it in any way.  That is because EH has steadfastly refused permission for the Altar Stone to be physically sampled. Secondly, the Mill Bay sequence of strata has not been adequately sampled and examined -- and neither have the abundant Senni Beds outcrops in SE Wales.  The mystery persists.......

All in all, there is a broad consensus that most of the Stonehenge bluestones have come from West Wales, and that most of the igneous materials have come from the rocks of the Fishguard Volcanics.  But when we talk about detailed provenancing, we are really no further forward than we were when the OU team published its research in 1991.  And the more work that Ixer and Bevins do, the more they demonstrate that within their broad rock-type categories every sample is unique and every sample has come from a different place.  There are around 30 different rock types in the bluestone assemblage, and this inconvenient fact is routinely ignored by MPP and his jolly band of quarry hunters.

PS.  This is a very useful map of the stone monument at Stonehenge, with acknowledgement to Julian Richards and the authors and publisher of "Stonehenge for the Ancestors" (Sidestone Press).

As we can see, there are five basic categories of bluestone, defined by rock type; but within each category there are great variations in  lithology / petrology between one stone and another.  They have clearly come from very many different locations in West Wales -- and maybe elsewhere.  

Part 1 of this title is already available free on the web, and Part 2 will be published in 2022.

When other stones and fragments in the Stonehenge landscape are included in the assemblage, we see that there are rocks from around 30 different localities.

This is quite a conservative list:  some recent additions need to be added......


Tony Hinchliffe said...

Well stated! Duly shared on Facebook.

Mavis Maximus said...

Yep, all points agreed with, but they would do well to look in the correct Mill Bay!