Thanks to Rob Ixer for forwarding this article, published in Mineral Planning magazine -- a journal presumably read by mining and quarrying engineers and such like. It's an interesting and brief introduction to the recent geological research relating to the bluestones, and all credit to Rob for that, but I have to say that some of its central assumptions and assertions are very poorly supported. The strap line under the main title is not encouraging -- it refers to "the discovery of the first secure Stonehenge-related quarry." As Rob and other readers of this blog will know, I think that is nonsense, and will continue to think do until somebody comes up with some decent evidence that there really is a QUARRY at Rhosyfelin. On the basis of the evidence thus far placed in the public domain, the evidence is just not there -- and I am more than a little surprised that a serious geologist should go along with a rather fanciful story trotted out by archaeologists who seem to know little about geology and even less about geomorphology ..........
Some thoughts on the article:
1. I don't agree with the definition of a bluestone as a Stonehenge foreign stone once used as an orthostat. I have always defined a bluestone as ANY foreign or non-sarsen rock found in the Stonehenge environs, and I suspect that most geologists and geomorphologists would agree with me on that. To limit the bluestone debate to orthostats is to allow the archaeologists to dictate the agenda; if one is really seeking to understand how the environment has evolved, and what processes have worked upon it, we MUST consider the contents of the regolith and the debitage. Indeed, in a recent message Prof Danny McCarroll suggested to me that the REALLY interesting stones at Stonehenge are not the othostats but the smaller stones, fragments, chips and flakes -- since they are much more likely to have arrived in the Stonehenge area by natural rather than human agency. (After all, even if our Neolithic ancestors were intent upon moving stones about, would they have bothered to cart about baskets or bags full of rather nondescript stones and pebbles, over great distances? Answer: probably not.)
2. With respect to Preselite, "A number of possible quarry sites are being sought along the northern edge of those hills". Now why on earth was that remark added to the article? It may be true, but it is actually counter to the thrust of the article, which strongly suggests multiple sites and sources -- and hence glaciation, erratic transport and deposition.
3. Orthostat 48 -- what do we know about that? Most recently it is described as a rhyolitic crystal-vitric-lithic ash-flow tuff from an unknown source, with no known matching material in the Stonehenge debitage (or at least, in that part of the debitage that has been investigated.) It's an interesting recent development that one of Stone's collected stones from the Cursus Field matches the orthostat.
4. With respect to the rhyolite debitage at Stonehenge with the distinctive "Jovian" structure, allowing an "almost impossible provenance of ten squares metres" to near point 9 at Rhosyfelin, I do not think that statement is justified by the evidence thus far presented in print. I have said that before, and I will say it again. If I had refereed the paper I would have pointed that out, and asked for more information. So in turn the statement "The archaeologists were told where to dig" is a sort of self-fulfilling prophecy. If you have a sample from an accurately located sampling point, and then tell somebody to go digging adjacent to it, of course you are going to find more or less the same rock type. That should be a surprise to nobody. (By the way, I am confused -- on the photo above, point 9 is a long way from the Rhosyfelin dig site, and point 8 is adjacent to it ......)
5. And what did the MPP team find when they dug as instructed? "They found, just a few metres from site 9, a large proto-orthostat, a large joint block set for its journey to Salisbury Plain". Sorry Rob, but that is a thoroughly unscientific comment, and you should not have made it. It doesn't matter what your objectives might have been in writing this article, or what sort of readership you were expecting, slapdash comments like that do no good to anybody. What those guys found was a large elongated slab of rhyolite embedded in a mass of broken scree and other debris typical of the debris to be found under almost any rocky outcrop in Pembrokeshire --- I suspect that neither you nor I have seen any evidence to justify saying any more than that. If there is more evidence, it should long since have been placed in the public domain. I say to you what I would say to any scientist: "Show me the evidence, and I might start to believe you -- if you do not show it, I am not prepared to accept your assurances about anything."
6. The article refers to ".... the first secure Stonehenge-related quarry site, confirming that man moved the bluestones." Rubbish. Rob, did you really write that? I don't believe a word of it, until you show me the colour of the evidence.
7. Re the final paragraph, I agree that "there remains a degree of lithological randomness inherent in the presence of the other types of rhyolitic tuff and sandstone bluestones" at Stonehenge. OK, one thinks, now the author is getting to grips with the problem. But then he says: "Could it be that the monoliths are a mixture of quarried stone augmented by randomly chosen rocks just to make up the numbers, so making Stonehenge among England’s earliest jerry-built public buildings?" Why this strange obsession with quarries and quarrying? And why should a geologist seem to have a problem with coming to the obvious conclusion -- namely that the strange assemblage of orthostats and stony debris is most easily explained as a consequence of natural processes (ie glacial processes) operating during the Pleistocene? I think I might just about go along with the statement about the "degree of lithological randomness", but since glaciers obey the laws of physics no less than rivers or winds, the randomness may be more apparent than real, in that we have not got round to finding satisfactory explanations for the presence of stones that currently appear to us to be disorganized and scattered about. Never fear -- enlightenment will come..... and as far as I can see, there are perfectly rational glaciological explanations for the presence of almost all of the bluestones so far identified at Stonehenge.
8. "....... are there further, undiscovered, quarries silently hiding among the Welsh bracken and flowering foxgloves, feint (sic) echoes of carefully organised stone and social structures?" Hmmm -- no comment.
Here is the article, with full acknowledgement to the magazine:
Digging into Stonehenge’s past
Mineral Planning, issue 143 / October 2012, p 13
The provenance of Stonehenge’s rocks has been a subject of heated
debate for many years. Rob Ixer explains how the
contents of a small box led to the discovery of the first secure Stonehenge-related quarry
The precise number, identity, geological provenance and pre-historical significance of
the various Stonehenge bluestones (any non-sarsen rock-type that was used as a
Stonehenge orthostat) have been, and will always remain, contentious. This has been especially
true in the past couple of years.
Although these 4-6-tonne bluestones are overshadowed by the larger, sandy-coloured
and locally derived sarsens (a type of indurated sandstone) that make up the
photogenic trilithons and arches of the outer circle and inner horseshoe, they have more to
tell us about Stonehenge’s origin and history. These rocks are once again the centre of
much debate about how they reached Salisbury Plain; even those who believe they
were man-hauled to Wessex, rather than carried by glaciers, are now arguing about the
route they took.
Small grey box
The cause is a recent re-examination of the contents of a little box of stones collected by
JF Stone in 1947 from plough soil close to the Stonehenge Greater Cursus and donated to
the Salisbury and South Wiltshire Museum. Many of the ten or so stones – none of which
are bigger than a fist – were found to be texturally and mineralogically distinctive.
Initial investigations showed none of these matched any of the standing bluestones:
*The Altar Stone, the largest at Stonehenge, is a possibly fallen, calcareous sandstone from
somewhere between the Brecon Beacons and south-west Wales, but not from Milford
Haven as previously thought.
* ‘Preselite’, the local name for altered spotted/unspotted dolerites, are the most
abundant Stonehenge bluestones and are very similar to outcrops on the high Preseli
Hills in south-west Wales. A number of possible quarry sites are being sought along
the northern edge of those hills.
*Rhyolitic lavas and volcanic tuffs, including the distinctive orthostat 48 (SH48) with its
pumice fragments and visible feldspar crystals. Only four volcanic lava bluestone
orthostats survive and earlier suggested origins are incorrect; their source is
probably from close to the Preseli Hills.
*In addition, there are a number of buried orthostats, including rare hard sandstones
and calcareous tuffs. There are also tens of thousands of bits of debris lying just below
the surface of Stonehenge and its immediate surroundings, ranging from 10kg to less
than a gram. This debris had only been subject to two small lithological studies.
All of these Stonehenge rocks had been described on a few occasions in the 20th
century, notably in the 1980s and later by the Open University (and colleagues) in 1990. They
were rigorously re-described initially by Dr Rob Ixer, of the University of Leicester,
accompanied after 2009 by Dr Richard Bevins, keeper of geology at Amgueddfa Cymru,
National Museum of Wales, to provide a standard set of descriptions.
A large and systematic study was set up to build on this work. This included detailed
petrography, complementary whole rock and detailed mineral geochemistry of Stone’s
stones by Ixer and Bevins, in partnership with colleagues from Aberystwyth and the Open
Universities, together with lithic assemblages found within Stonehenge and its immediate
environs, collected over the last two centuries, plus all the debitage from 21st century
excavations, as well as dedicated geological in situ collecting from south-west Wales.
New in situ sampling, down from the northern slopes of the Preseli Hills, showed
some of Stone’s stones and Stonehenge rhyolitic debitage could be matched to highly
unusual rocks from the Pont Saeson area and in particular to a 70m rocky outcrop called
Craig Rhos-y-felin. Stonehenge material was being provenanced to an area of less than a
square kilometre. Subsequently 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.
So the contents of a 60-year-old box led to the discovery of the first secure Stonehenge-
related quarry site, confirming that man moved the bluestones. But the initial
assessment of Stone’s stones was wrong, because in June 2012, one of the rocks was
recognised as coming from bluestone SH48, making it only the fourth piece of debitage
from thousands investigated that could be matched to a specific bluestone orthostat.
However, even if many of the bluestones come from a couple of outcrops on the top and
northern slopes of the Preseli Hills and even from a very small area within those outcrops
(as has been shown for Craig Rhos-y-felin and strongly suggesting they were quarried) there
remains a degree of lithological randomness inherent in the presence of the other types of
rhyolitic tuff and sandstone bluestones. Could it be that the monoliths are a
mixture of quarried stone augmented by randomly chosen rocks just to make up the
numbers, so making Stonehenge among England’s earliest jerry-built public buildings?
Or are there further, undiscovered, quarries silently hiding among the Welsh bracken and
flowering foxgloves, feint echoes of carefully organised stone and social structures?
Dr Rob Ixer is a geologist at the University of Leicester