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Friday, 6 July 2012

How many bluestone quarries are needed to make an archaeologist happy?

 Carn Meini.  When is a quarry not a quarry?

On several occasions on this blog I have tried to publish a comprehensive list of all of the erratic or foreign stone types found at Stonehenge and in the immediate environs.  I came up with a list of more than 30 rock types, which means more than 30 different provenances.....

Myris has recently reminded us that MPP is off hunting for Neolithic quarries again, and that he has had detailed discussions with the geologists as to where these might be.  I would argue that that is a total waste of time and taxpayer's money, but I doubt that he will be deterred.  So how many quarries are needed to satisfy an archaeologist who lives with the utter conviction that glacier ice had nothing to do with Stonehenge?  I would say that we need at least 30 of them, since we do not just have to explain the presence of orthostats but also the presence of "debitage" (such as the debitage traced to Rhosyfelin) and other lumps of stone of various shapes and sizes.  Rob would argue that we should dismiss all of this ancillary or incidental material and concentrate on the orthostats -- and he argues on that basis that all we need to find would be about ten quarries.  I part company with him on that -- debris and foreign stones MUST be accounted for, whether they have been carried into the area by glacier ice, human beings or even machines involved in road-building works.  (I have the same problem on Pembrokeshire beaches, trying to work out what might have been carried by ice and what might be dumped ship's ballast from the grand old days of sail.....)

So -- ten quarries, or thirty, or somewhere in between?  And what are the features on the ground that we need to be able to identify in order to call a rocky outcrop a Neolithic quarry?  We have had much discussion on this site about THE bluestone quarry at Carn Meini -- now, from what Rob is suggesting, Rhosyfelin is likely to be given similar star treatment.  First will come a picnic site on the river bank -- then how about an interpretation panel and maybe a tasteful snack bar?

Here is the bluestone list published on this blog in 2010.  It is as reliable as I can make it -- it it has any errors, please let me know.  I will adapt and add notes as necessary.  With a suitable input for geologists, I hope it can be refined to the point of becoming reliable and maybe even definitive.

Known Stonehenge Bluestone Types

1.  Unspotted dolerite ---- monoliths  45 and 62.  Carn Ddafad-las?

2,  Spotted dolerite -- densely spotted.  Monolith 42  -- Carnbreseb? 43?

3.  Boles Barrow dolerite -- spotted?  But similar to stones 44 and 45? From Carnmeini / Carngyfrwy area?

4.  Rhyolite  -- stones 38, 40, ignimbrite character.  Ash-flow tuffs (dacitic). Not Carnalw ? May be from different sources?

5.  Rhyolite --  stones 46 and 48, rhyolitic ash-flow tuffs.  Carnalw area?  Same source?

6.  Rhyolite fragment from a different source from the above types

7.  Laminated calcareous ash -- stumps 40c, 33f,  41d

8.  Altered volcanic ash -- stump 32c, 33e?

9.  Rhyolite -- another type -- stump 32e.  Related to Pont Saeson samples? (Note added: This is the foliated rhyolite described from Rhosyfelin by Ixer and Bevins -- but the link with stump 32e is speculative, being based on photographic rather than rock sampling evidence.)

10.  Micaceous sandstone -- stumps 42c, 40g (Palaeozoic -- South Wales origin?)

11.  Rhyolite -- lava -- stone 46

12.  Rhyolite -- flinty blue -- different lava?  stone 48

13.  Spotted dolerite with whitish spots --stones 33, 65, 68, stump 70a?, stump 71?, 72

14.  Spotted dolerite with few spots -- stone 31, 66?

15.  Spotted dolerite with pinkish spots -- stones 150, 32, 34, 35A, 35B (one stone), 39 (?), 47, 49, 64, 67, 69, 70

16. Spotted dolerite -- moderate spots -- stone 37, 61, 61a?

17.  Unspotted dolerite -- stone 44 -- different from stones 45 and 62

18.  Very fine-grained unspotted dolerite -- stone 62

19.  Silurian sandstone -- Cursus -- fragments

20.  Devonian sandstone -- Altar Stone -- Devonian Senni Beds -- Carmarthenshire or Powys

21.  Sarsen sandstones -- various types -- packing stones and mauls

22.  Jurassic oolitic ragstone -- Chilmark?

23.  Jurassic glauconitic sandstone -- Upper Greensand?

24.  Gritstone unspecified fragments (Maskelyne, Judd)

25.  Quartzite unspecified fragments (Maskelyne, Judd)

26.  Greywacke unspecified fragments (Maskelyne, Judd)

27.  Granidiorite -- Amesbury long barrow 39

28.  Quartz diorite -- ditto

29.  Hornblende diorite -- ditto

30  Flinty rhyolite -- fragments from Pont Saeson (Note:  different from the Rhosyfelin samples?)

31.  Rhyolite fragments -- with titanite-albite intergrowths (source unknown)

30 comments:

chris johnson said...

One would be a nice start. MPP points towards Carn Goedog and Rhos y felin.

Anonymous said...

Brian,

Thank you for that long list of bluestone types found at SH. These make a convincing argument against human quarrying of so many different types of bluestones from Wales. Only glaciers can account for this!

But where in that list are the “foliated rhyolite fragments” from Rhosyfelin we have discussed in your blog last year? Since so much reference has been made to these before, these should be perhaps highlighted in your list.

Kostas

BRIAN JOHN said...

Chris -- yes, Carn Goedog is where MPP and his colleagues did a spot of digging last year. Maybe they are back there this year as well. He would like to think of Carn Goedog as an important Neolithic settlement site -- and maybe he harbours notions that it was a quarrying site, providing facilities (cafe, dormitories, prostitutes etc) for the rough quarrymen? I feel another story coming on...

chris johnson said...

Wonder what m thinks about this list? It seems we are further on with provenancing every day. His list must be the master document.

BRIAN JOHN said...

Myris -- there we are -- an invitation from Chris for your little list! (Actually, Chris, I disagree that Myris's list will be the master document, since he and I do not agree on what should be included on the list. I want ALL foreign stone types to be included and given due weight -- and Myris wants only the bluestone orthostats to be included in the list.
According to the latter criteria, the foliated rhyolites from Rhosyfelin should not be included on the list, since no orthostat of that particular rock type has been identified at Stonehenge.....

BRIAN JOHN said...

Kostas -- the foliated rhyolites are number 9 on my list. Pont Saeson and Rhosyfelin are very close to each other on the ground. Actually stump 38e is only SUSPECTED of being made of the Rhosyfelin foliated rhyolite. No sample from that stump has been examined recently, and it is currently buried.

Tony H said...

Brian's suggestion is that Mike PP and his fellow Wild Rovers have really been on a wild goose chase (should that be 'gneiss chase'? - oh no, that would just be a load of unwanted schist in the present, Stonehenge/ Preseli context).

Seriously though, folks, I think that all Mike, Josh and Colin need for their [eventual] documentary on "The Fab Quarrymen who Beatled About All those Years Ago", will be a voice-over by that LOVELY romantic - sounding gardener Alan Titchmarsh. Luvely. Or am I expecting too much?

Myris of Alexandria said...

No the definition in Ixer and Bevins 2010-possibly the earliest recent, redefinition- of bluestone is “any non-local, non-sarsen stone that belongs or MAY have belonged to an orthostat” (read the original lit!).

So Pont Saeson/Rhos “rhyolites with fabric” (Groups A-D but not E in Ix and B 2011b) including the distinctive Jovian, sub-Jovian, Snowflake and Grévy are believed to be from one or more orthostats -32e is the best candidate- so are bluestones.
The final (for now) classification is in Ix and B 2013 ferret club magazine.
The original 30+ classes of rhyolite have been grouped into just 4 but with sub-groups see above. Snowflake and Grévy may be an orientation effect and not a true lithological distinction.
Now that is just for one, albeit major, class of debitage. This has taken 3 to 4 years to do.

To produce a definitive list would take a few days of concentrated thought and it is doubtful that it would help.
Total number of bluestone lithologies between 10 and 20. Is that the number of quarries who knows?
A polemical piece by Ixer on his website in ‘on-line publications’ (so NO excuse for not reading this bit of primary-ish lit.) is informative background reading. Called
“Founded or foundered on Rock” ….Welsh rocks.

What are excluded are the little bits of Mesozoic sandstone, bits of Axe Groups I-III etc. bits of West Midlands roadstone sent by bizarre members of the public thrusting their hands into molehills, 18th cent antiquarians emptying their pockets onto the grass etc etc.
New Age rock crystal pendants (though pedants are welcome and indeed embraced).

So once again I shall resist the Siren call to produce this year’s list only to dash myself upon the rocks. It would contain fewer entries than Brian’s.
M

BRIAN JOHN said...

Thanks Rob -- very interesting. We are still not going to agree to a definition. Yours is "“any non-local, non-sarsen stone that belongs or MAY have belonged to an orthostat” -- that may be fine for you as a geologist, but it's not fine for me as a geomorphologist, since I am also interested in smaller stones that may never have been incorporated into the bluestone circle or otherwise used for standing stones. It seems to me to be counterproductive to dismiss these smaller stones as irrelevant. So we will agree to differ.

Thanks for the reminder of your old article on provenancing. Would you be happy for me to do a post quoting a bit of it and giving the URL?

Myris of Alexandria said...

Please do.
Like you I wish that the small pebbles in Salisbury Plain were more diverse or thatwe could see the complete data set.
The BGS Salisbury Plain Memoir what does that say??
M

chris johnson said...

Myris, very interesting article. I hope the central database is now supported.

Is the ferret club magazine you refer to available for non-ferrets?

chris johnson said...

Brian, I understand your broader interest and the reasons for it but it seems to extend the term "Bluestone" beyond usefulness when it is to include any erratic however transported. Perhaps the word "erratic" would be more useful and generally understood to describe your interest? "The Stonehenge Erratic Enigma" has a definite appeal.

Ixer and Bevins definition better reflects common understanding although it is too broad for my taste because it includes Altar stones and suchlike. Not that the Altar stone is uninteresting of course. I think they make their definition to define their scope.

It is frequent in my field to argue about definitions. Some people make the definition so broad that any question no longer makes sense. Others narrow a definition to suit their purpose, often obscuring the question again.

My first question, that your list does not answer, is where the non-sarsen orthostats in Stonehenge came from. It is useful to include the Rhos-y-felin debris as it is a reasonable presumption that they might have been orthostats once. So I would appreciate a simple table of orthostats with what we know or our best guess about provenance - so Carn Menyn, Carn Goedog, Carn Breseb, Carn Ddafad-las, Rhos-y-felin, etc. Maybe such a list is secret but MPP implies that a lot more detail is known than I can access in an orderly way - e.g. via a list.

BRIAN JOHN said...

Chris -- you highlight the confusion! You cannot possibly exclude the Altar Stone -- it is far too important for that. And we are even on dodgy ground when we take the Ixer / Bevins definition including the words "MAY have belonged to an orthostat." Who decides what MAY have belonged to an orthostat? The geologists? The archaeologists? The geomorphologists? I could argue, quite plausibly, that almost all of the cobble-sized debris and most of the flakes MAY have come from past orthostats that aren't there any longer. There are stumps and gaps and pits that MAY have held stones -- even relatively local sandstones or limestones -- that were subsequently removed or broken up. Nobody could prove me wrong, except by referring to the dubious concept that somehow the builders of Stonehenge "preferred" bluestones from Wales. Pure speculation. Round and round in circles.

No -- if you don't mind, I'll stick with my conviction that all of the foreign stones at Stonehenge are important.

Myris of Alexandria said...

Ah we are but in Lilliput already.
I supect that Ixer might include Carn Menyn (it is the only site to be properly sampled and fully described and he now uses the term 'SH orthostat XX is consistent with' but feels the other dolerite localities are yet to be proved (this despite his earlier brasher published work).I know he feels that to distinguish between spotted and unspotted may be a hare too many.
Some archies would only want Carn Menyn
Some do not want Carn Menyn but only the northern slope Preseli outcrops.
Some want them all.
I think everyone wants at least one of them.
You cannot go wrong with Rhosyfelin unless you do not think it came from an orthostat in which case strike it out.
So be a big bold boy and make up your own list-the fun is justifying it. We do.
The Altar Stone is the classical bluestone and the definition was fitted to include it.
M

Myris of Alexandria said...

The official name for the ferret club is 'Wiltshire Studies' the old
Wilts Arch and Nat Hist Magazine.
aka the Wilts Gardening and Ferret Club Mag, aka the ferret club mag.
It has to be the source for many things SH and is well worth reading.
Everyone and their dog has published there.
M

chris johnson said...

Brian, you did not answer my first question but never mind. I think you do not have the list.

You are right of course that we cannot ignore the Altar stone. Yet, in terms of problem solving it is helpful to divide the problems into addressable chunks. I tend to do this according the rule of threes because 3 seems to be most comfortable for most human brains, including mine. Dividing an issue into 10 or 40 sub-issues is too difficult.

Basic problem: there are foreign stones in the monument. Many came from Presceli (Bluestones) and some came from elsewhere (e.g. Altar Stone). The inner circle seems to be predominantly spotted dolerite from Presceli and much debris has a Presceli origin so Presceli versus others versus sarsen does not seem an inappropriate way to differentiate the issue on top level.

You have noted that I have made yet another definition of "Bluestone" = stones coming from Presceli region. So I imply three categories 1) sarsen 2) bluestone from presceli 3) stones that are neither sarsen or from presceli. From this top-level we can derive sub-categories. Dr Ixer is well on the way with regard to 2).

There are perhaps other ways to define the problem that needs to be worked but my way seems logical and appropriate for now - at least to me.

So my working definition of "bluestone" would be "stones in and around Stonehenge that come from the Presceli region". I think this is how many ordinary people and journos look at it and so it might helps communication.

What I miss is the next level of categorization around "bluestone from prescelli".

chris johnson said...

Dear Myris,
Quick reaction because I have/want to go for a walk in our July sun. You made me chuckle but as usual I will have to read your post more intensively to discern your meaning.

The notion of my making a list is too preposterous. Nobody would take me seriously, not even my close family, and rightly so. My wife would think that I have finally lost the plot and disconnect my internet in our mutual interest - fate preferred above death but only slightly.

I'll try and find your Wiltshire links later - I might even pay - but on past experience with Wiltshire you have to go on foot or by horse with two weeks notice and cash in hand. Me, I am a simple guy with a volatile life while slowly attuning to the modern era with a wish to download right now and credit card handy. Not someone the Devizes museum is able to accommodate.

Perhaps you could just mail me the relevant info?

Anonymous said...

Myris you write,

“You cannot go wrong with Rhosyfelin unless you do not think it came from an orthostat in which case strike it out.”


But why “strike it out”? It seems to me if the many foliated rhyolite fragments found in the SH landscape did not come from any SH orthostats (present or past) that presents a problem for archeologists and begs answers from geologists (like you) and geomorphologists (like Brian).

So when you argue “strike it out” aren't you embracing the archeologists agenda?

I am becoming concerned again!

Kostas

BRIAN JOHN said...

I don't agree with Kostas very often, but I agree with him on this one. What would be the logic of "striking out" all of the Rhosyfelin debitage? If it's there it needs to be identified -- and then we have to think of how it got there. The identification of the source of that material is a fascinating piece of geology -- and the find is important, whether or not it eventually turns out that stump 32e is made of identical material.

Anonymous said...

On my bimbling across the Preseli's this afternoon I came across two archaeologists one oldish grey beard, red hat (face familiar from dig at Pont Saeson?)and the other connected to Bournemouth Uni, in a hole just below Carn Menyn.

I was informed that their hole was the site of a quarry and they were extracting mud stone which they said had been used as tools?

Their hole has a shallow channel that led up to a broken slab which they told me was a bone fide discarded bluestone!

I remained sceptical, the hole looked like the usual collection of shattered rock that you would normally find on a hillside underneath rocky outcrops.

Anyway they appear to be there for a while yet as there work has been delayed this last week because of the weather.

They can be found directly underneath the main crag at Carn Menyn in a line to the track / footpath that starts at the fields below.

Tony H said...

Chris

Regarding Myris' [surely The Chief Barker? Certainly some might suspect the definition to be valid] mention of the ferret club mag etc.

This term I admit baffled me at first and it took personal communication with said Fount of All Geological Knowledge before realising he was referring to the WANHS Magazine.
For your information, you can probably sit in many learned libraries and read WANHS for free. You certainly can see every one of the volumes from c. 1850 at the English Heritage offices [formerly NMR] in Swindon (somewhat closer to Wales - where I believe you reside - than Devizes in that it is accessible within a couple of minutes from the Welsh-English M4). The English Heritage library staff may well be prepared to photocopy articles you requeat.

But since Wales, for instance, has University Archaeology Departments at Cardiff and Lampeter at least, you may find it worth contacting them as they most likely possess back-runs of WANHS, since some of their staff take an interest in things t'other side of 't'Severn Estuary. Bristol Uni Archaey Dept will have them too, just over the toll bridge, if you have the loose coinage (but no Euros).

BRIAN JOHN said...

Thanks, Anon, for the intelligence regarding strange archaeologists in the mist and rain. Those will be Profs GW and TD, doing their SPACES 2012 fieldwork. Carn Meini is of course on their patch, whereas the other tribe, led by Prof MPP and colleagues, will be working beneath Carn Goedog and probably (again) at Rhosyfelin later in the summer.

Your scepticism does you credit -- there is no way you would use mudstone as a tool for doing anything. Ah - another discarded bluestone. Certain people seem to find them everwhere......

Tony H said...

Anon, no sign of a fawning [Professor] Alice Roberts (late of "Coast") then? She was with these two gentlemen at Carn Meini when she excitedly accepted all they told her about healing springs, stones,and human transportation last year. And it was chucking it down with rain then, too. Geoffrey was wearing a fetching bright yellow day-glo number, rather like those old porridge adverts.

Myris of Alexandria said...

Boys, boys, boys we must try to keep our rugs on.
I like Rhosyfelin as an echte site for the origin of orthostat material aka bluestone. There is too much of it and it is too widespread to be Sunday afternoon knapping (now like that pun and it came unsearched for) so ‘must’ be orthostat-related.
I was allowing free choice,I am a child of the 60s and believe in the inalienable right of everyone to make a little Stonehenge list.
Most will be wrong.
I Do like the soubrette ‘Chief Barker’ whilst I hope my bite is far worse than my bark, it suggests Canis Major and so allows me to say that
"I am constant as the northern star,
Of whose true-fix'd and resting quality
There is no fellow in the firmament."
Of course it could be because I am the archies poodle!!
Good to hear of the brave Profs in the Mist. I looked at the mudstones for them in 2006/7/8 (whenhe’fer) and failed to see what they could be used for. Certainly no use for axe-heads-they have been trying give them some relevance for years now.
Mr Johnson send Dr Ixer a little gift -something amusing and unexpected –his tastes are Catholic to Orthodox- and he will (I am pretty sure) send you the pdfs privately-indeed he has made this offer a couple of times but seemingly too discretely!
Anyway boys lets gird ourselves for an exciting few months.
Do read Cavarfy’s poem ‘The Ides of March’. Perhaps the greatest piece of poetic irony ever written? Caeser so reminds me, in a hazy sort of way, of ‘our’ great and good.
M

BRIAN JOHN said...

The idea of a list is very fine, but in practice I suppose we all want different lists, because we can't actually agree on what the list should contain. Not sure I have ever seen a full list of every standing or fallen bluestone and stump with geologoical identifications added alongside. The nearest thing I can think of is the table published by the OU team in that big paper in 1991 -- Thorpe et al, including Rob.

When I can find the time, I might annotate my own list by adding references to show who has given the suggested provenances....

Myris of Alexandria said...

Yes that (Thorpe et al) is an excellent place to start but the geological attributions have been disproved somewhat in Bevins et al 2012.
There is Ixer's Dolerite list of the mid 1990s
But Thorpe et al is where I would start from.
There is Howard's list in Pitts 1982? (Thorpe et al is partly based on this)
I think there is a list in Darvill's recentish SH book
and finally the one carved in (French)on my heart.
M

Phil Morgan said...

Brian,
There was an anon post recently regarding a current excavation on Carn Meini which read as follows:

"I was informed that their hole was the site of a quarry and they were extracting mud stone which they said had been used as tools?

Their hole has a shallow channel that led up to a broken slab which they told me was a bone fide discarded bluestone!

I remained sceptical, the hole looked like the usual collection of shattered rock that you would normally find on a hillside underneath rocky outcrops.

Anyway they appear to be there for a while yet as there work has been delayed this last week because of the weather."

Having spent some time in the rain on CM I can confirm that Anon was spot on with the reference to the weather.
However, I am confused by the reference to mudstone for I understood the quarry pit was for the extraction of metamorphosed mudstone which is a very hard flakable stone, ideal for tool making and much sought after. Meta-mudstone axes have been identified, and I seem to recall that some of the bluestones at Stonehenge are made of this material. Interesting.

BRIAN JOHN said...

Thanks Phil -- not sure what is meant here by metamorphosed mudstone. In my understanding, metamorphosed mudstone is slate, which is very nice for building stone walls with, or putting on roofs, or cutting up bits of flesh, maybe, but probably not much use for anything else. There is certainly plenty of slate up on Preseli -- since the igneous intrusions were intruded into mudstones, there will have been a lot of metamorphic alteration around every molten mass. But I cannot imagine what Profs GW and TD will have been reading into it in terms of archaeological significance. Any suggestions?

chris johnson said...

The reference to mudstone seems quite casual. I am starting to appreciate that lay people can quickly confuse mudstone, slate, and rhyolites.

Could be this depends on who was telling what to who, and with the volume of anons on this board this is tricky.

BRIAN JOHN said...

Quite agree, Chris. This may be just a piece of second-hand nonsense or a wild goose chase -- so no point in getting too worked up about it.