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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Thursday, 18 October 2018

Bedd yr Afanc -- the target for 2019?

Bedd yr Afanc is a passage grave on Brynberian Moor -- already much discussed on this blog. It is reputed to the the place where a terrible monster called an afanc was buried -- having become so bothersome to the locals that they at last slaughtered it and dragged it up onto the mountainside to be disposed of. A fitting parable, maybe........?

At the end of July, when MPP and the other archaeologists applied for permission to excavate at Waun Mawn, they also asked for consent -- and got it -- for the digging of three pits near Bedd yr Afanc.  But they didn't do any work there this year --my own guess is that they were so desperate to find something significant at Waun Mawn that they threw all their resources at that site instead.

But at Bedd yr Afanc they have done some surveying work and marked out assorted locations where they clearly want to dig.    Probably planned for 2019?  The marks are on the circumference of yet another putative circle which has the passage grave at its centre.  The diameter of the circle is approx 50m.  So they are clearly hypothesising that a stone circle was constructed around a pre-existing burial site, or that the burial site was built in the middle of a pre-existing stone circle.......

The circle stone circle obsession is as strong as ever........... but I wonder how long it will be before the funders of the work get fed up with all the hype and come to realise that they are constantly throwing good money after bad?  Eight years of hunting by the archaeologists, and nothing to show for it.


By the way, Bedd yr Afanc is built on a slight ridge that seems to be made of rhyolite, although the standing stones in the monument setting are all (from a cursory examination) made of the same dolerites, rhyolites and ashes as all of the other erratics littering the landscape.  Today I walked all the way across the moor to Hafod Tydfil, across many small mounds of moraine, and with till underfoot along the ancient trackway, but I didn't see a single cobble or boulder of spotted dolerite.  I am still working on the directions of erratic travel on the northern flank of the mountain.

Monday, 15 October 2018

Another biological process explains everything

Down goes a giant oak........

......... and up goes a 2-tonne monolith, ending up 2m above the ground surface

Well well, you could knock me over with a feather.  Just when I thought there was nothing much to say about extraction pits, bluestone monoliths, sockets and archaeological artifices, along comes a southerly gale, down goes a very large oak tree in the wood at the back of the house, and all is revealed.

What has happened is this.  In the Cilgwyn Valley there is an undulating surface of rocky outcrops and moraine, with large dolerite boulders and other erratics all over the place.  Over the millennia a mature woodland has developed, comprising oak, hazel, ash, holly, rowan, and sycamore for the most part.  The trees are safe as long as they do not get too tall, but if one tree has a crown above the rest of the canopy, it becomes vulnerable, and even top-heavy -- and eventually, in a gale, it will come down.

That's exactly what happened the other day. So what's all this got to do with archaeology?  Quite a lot, as it happens.  I have talked about biological processes before, in the context of the supposed "quarry" at Rhosyfelin.  Then, I was talking about the role of rocking trees and bushes, and expanding roots, in forcing slabs of bedrock to part company with the parent rock and to come crashing down, contributing the the accumulating mass of rockfall debris at the base of the slope.

Here, near the Cilgwyn Waterfall, we are talking not about monoliths falling, but being lifted into the air.

When the tree came down, the root mass, which was of course horizontal, embedded into the stony ground, was tilted through 90 degrees, ending up vertical.  It carried up with it a large quantity of stones and boulders, the biggest of which is this dolerite "triangular pillar" weighing about 2 tonnes.  It has all the features of a highly abraded and weathered glacial erratic.  The moss-covered area id the part that was previously exposed at the ground surface.  So there it sits, about 2m above the ground surface, supported on a tangled pedestal of roots, soil, leaf mould, cobbles and smaller boulders.  There is quite a lot of clay too.  At the ground surface there is a large pit that was previously occupied by the root mass.  It's about 50 cm deep, and 1m x 3m in extent.  It contains a lot of debris, including smaller stones which were in contact with the large boulder that has been lifted into the air.  In another context these might be referred to as "packing stones".........  and the sides of the pit are not vertical but damaged and degraded by the occurrence -- in this case -- of a rather catastrophic event.

So what happens next?  Assuming no human interference, the "bluestone monolith" could remain on its pedestal for weeks, months, years, decades, centuries or even millennia.  It's not all that solidly "gripped" by roots, so my guess is that it will come down sooner rather than later, as rain washes away the finer material in the pedestal.

And what will people find in a thousand or five thousand years' time?  Well, they will find the hollow from which the boulder was extracted, with these smaller stones more or less where we see them now, probably filled with a mixture of slope wash debris, leaf litter and the rotted remains of the oak tree root system.  The full rotting process could take many centuries, since this is an oak tree.   If this woodland should be set on fire at any stage, either as a result of a lightning strike or because it is burnt for clearance purposes, there could be ash, charred fragments and even charcoal incorporated.   When the monolith does eventually slide off its pedestal and find its "final resting place" it is most unlikely to end up where it started off -- it could even be a few metres away, with a completely new alignment.  Then the soil surface will gradually build up around it, eventually burying both the boulder and the sediments beneath it.

So we end up with an extraction pit containing smaller stones and assorted sediments easily differentiated from those in the sides of the pit, dateable organic sediments, and a measurable gap between the extraction of the boulder and its eventual repositioning following the removal of its supporting pedestal.

This process is a perfectly valid one if we seek to explain what has been uncovered in the excavations at Waun Mawn.  But surely the Cilgwyn Valley contains a sheltered and prolific woodland, whereas Waun Mawn is a wild and windy -- and treeless -- moorland?  Not so fast, dear reader.  It was not always thus.

Not far away is the famous tor called "Carn Goedog", where MPP and his merry gang have been excavating.  That means "woodland carn", and the presence of bluebells around the crag is a pretty good indicator of mature woodland not so long ago.  The windswept appearance of the moorlands today is largely down to management -- and several centuries of grazing by sheep and other animals.    Gorse clearance by burning has played its part too.  Not far away from Carn Goedog, at the enclosed "summer settlement" of Hafod Tydfil, there are healthy mature trees growing in abundance, simply because they have been protected from animal grazing.  And at Waun Mawn itself, we know that it was once designated as a "deer park" and was used as such in the Middle Ages.  Deer parks did not exist on wild moorlands; on the contrary, they were densely wooded, so that deer, wild boar and other animals could be hunted with the help of abundant cover  by the lord of the manor and his cronies.

So there we are then.  The features at Waun Mawn which have excited certain archaeologists and left the rest of us rather unimpressed can all be explained by natural processes.  All we need are some dolerite boulders or monoliths littering the landscape, some mature trees and the occasional gale.

Sunday, 14 October 2018

Waun Mawn 2018 dig -- and some very naughty boys and girls

One of the pits after restoration

Part of the biggest pit -- covering an area of 198 sq m -- when it was open

It will be obvious to readers of this blog that I -- and many others -- are rather fond of the Waun Mawn and Tafarn y Bwlch neighbourhood, given that it is wild and beautiful up there, and it also contains something of a treasure-house of archaeological features.

When I saw the sheer extent of the 2018 Waun Mawn dig, I was immediately concerned about its impact on a specially protected area -- inside a National Park, inside an SSSI and inside a Special Area of Conservation too. That all represents -- in theory -- the highest level of protection possible under British law.  I wondered what the consent process was for archaeological digs of this type -- who does the applying, to whom, and how are consents issued?  Are there any inputs into the process from other interested parties like Wildlife Trusts or CPRW?  What judgments are made on costs versus benefits?  (In other words, does somebody make a judgment on whether the environmental damage is acceptable when set against the potential scientific or cultural value likely to come out of the dig?)  Further, what conditions are attached to consents, what monitoring is there, and what sanctions are there if the terms of the consent are breached?

Another view of "big pit" when open

I did a post on this topic back in September:
and published a few photos of the open pits.

First, I asked the National Park whether they had issued a consent.  No, they said, the whole process is handled by Natural Resources Wales (NRW).  There is no input at all from Cadw, RCAHMW or the Dyfed Archaeological Trust -- and that's interesting in itself.  It doesn't appear that other bodies are even asked for their opinions.  Nobody apparently asked what the purpose of the dig was, or what the chances were of making significant finds.  I checked on the NRW web site for any trace of a consent, but there is no searchable database.  That means there is no role in the process for interested parties or the general public -- unlike the situation with regard to planning applications.  There is no public record that can be searched.  The only way to get information is to write in with a specific request.  So I banged in a letter.  After 20 days or so I got a reply, and it was very interesting indeed..............

It appears that the application to NRW was made on 30th July via the Barony of Cemais -- the landowner of the Preseli commons. That means that the Barony received the request from Prof MPP
and his team, approved it, and passed it on to NRW on his behalf. The application was in the form of a simple letter, asking for consent for "archaeological excavations" involving six trenches, each one no larger than 90 sq m, with a maximum area excavated totalling 540 sq m. The work was due to start on 2nd September, lasting for 3 weeks. There was no mention of the proposed depth of the trenches. The applicant stated: "Trenches will be excavated by hand. On restoration, they will be backfilled by hand with their soil, stones and turf so as to leave them in the condition in which they were found." Prof MPP also said on the application: "Vehicle use will be restricted to an ATV (all-terrain vehicle) provided by the National Park authority and driven by one of its staff, warden Richard Vaughan. The archaeological team will carry all equipment to and from the excavations on foot. They will park at recognised parking spaces and walk to the sites each day."
Consent for the operations was given on 8th August. (Consent Ref No: 2278324)  No conditions or monitoring requirements were added at the consent stage, and so it was a straightforward "rubber stamping operation" taking just a week and involving minimal scrutiny.

So to the dig itself.  It appears that the vehicle use restrictions were adhered to, and the dig was indeed completed without the use of mechanical diggers.  A lot of human labour went into it!   But this is what happened.......

Since NRW is clearly not very interested in checking that the terms of its consent have been adhered to, I offer it some assistance. In some cases it is quite difficult to determine where the boundaries are between the 2017 and  2018 excavations ("trenches" is the wrong word, because they are actually all quite shallow), and some parts of the 2017 digs have been re-opened.  But as far as I can see there are 15 new excavations (not 6), ranged around the circumference of the putative giant stone circle.   The total surface area involved in actual digs seems to be about 500 sq m, with approx the same area disturbed by soil and turf dumps, working traffic and vegetation clearance.  Most of the work has been done in the NE and NW quadrants, and the biggest areas stripped of turf are in the south, where one excavation covered 60 sq m, and in the SW, where one covered 198 sq m.  In the report sent to me by NRW, this is what their field officer said:

**  Following completion of the works the applicant contacted me to state that they had accidentally gone over the consented 540m sq. He calculated that they had in fact excavated 700m sq. The applicant apologised for this accidental event.
**  Unexpectedly dry weather this year will have undoubtedly hampered the reestablishment of the turves. I have not visited the site yet but will do so to assess if anything further needs to be done in terms of restoration.
**  A letter will be sent to the applicant informing them that, should any consents be issued in the future for similar work, they must ensure that the works adhere strictly to the terms of that consent.

MPP has been quite honest in admitting that the area excavated in Sept 2018 (probably including the reopening of some 2017 pits) is about 700 sq m.   I wouldn't argue with that, although one does wonder about how an area of 160 sq m could have been excavated "accidentally."   But what worries me more is that one of the pits -- at c 198 sq m -- is far in excess of the maximum size allowed under the consent; that the replacing of turves has been for the most part pretty slapdash; and that some excavated areas (including one area of about 8 sq m near the eastern limit of the investigated area) have not been reinstated at all.  All pegs, markers etc have been taken away, and the site was left clear of any litter -- so that's something to be thankful for.

All in all, I think the diggers have made a reasonable effort to tidy up after themselves, given that they had some pretty inclement weather to cope with in the last few days of the dig, when they were doing the reinstatement work.  But the fact of the matter is that they have not left the area as they found it, they have breached the conditions both in respect of the total surface area excavated, the maximum size of excavated pits,  and the number of new pits opened (15 instead of the requested 6).  They have also left some areas devoid of turf altogether.  I shall refer this back to NRW with a request that they should make a proper post-excavation site survey and require additional reinstatement work to bring it up to an acceptable level.

I shall also ask NRW whether they are satisfied that their "due process" has provided an adequate level of protection to this sensitive area,  given the requirements placed upon them in law.

Am I making a fuss about nothing here?  I think not.  Some of us have thought from the beginning that the environmental costs of this sort of work, within an area theoretically afforded the highest level of protection, always were far too high, given that this always was a wild goose chase.

A chaotic mess left adjacent to one of the recumbent stones at the north end of the excavation site

One of the areas where no reinstatement work has been done

Friday, 12 October 2018

Waun Mawn and the great spotted dolerite hunt

The diggers have gone -- but in the aftermath there are plenty of stones which can be examined

This is from the 2017 Report and funding application from MPP, on behalf of the project called
"The Welsh origins of Stonehenge" [RFF-2017-23]
Principal Investigator: Michael Parker Pearson
Professor, University College London, Institute of Archaeology

"The main discovery was that four standing stones in an arc at Waun Mawn, above a source of the River Nevern, are the likely remains of a prehistoric stone circle, most of which was dismantled and removed in prehistory (fig.6). Its 80m-long arc suggests a former diameter of c.115m, which would make it the largest stone circle in Britain except for the outer ring of Avebury. Although excavations in 2017 failed to obtain a date for the stone circle’s erection or dismantling, its stone sockets were emptied and the stones removed before the onset of peat growth. We are currently awaiting radiocarbon dates from the base of the peat, though it is likely to have started forming in the Bronze Age."

This was of course a considerable over-egging of the pudding as far as the significance of the 2017 work was concerned, but when applying for research grants a man has to do what a man has to do.........

As we have mentioned before, one of the main assumptions built into the "proto-Stonehenge" hypothesis is the supposed link between Waun Mawn and the "monolith quarries" at Carn Goedog and Rhosyfelin.  The map showing the links has been widely used.  In his lectures MPP has taken it for granted that multiple monoliths were transferred from the quarries to Waun Mawn and used there in a vast stone circle which existed for c 400 years before being dismantled and moved, lock, stock and barrel, to Stonehenge. Further, it is widely assumed that around 80 bluestone monoliths were used at Stonehenge -- and further assumed by MPP that some of them might have been used temporarily at "Bluestonehenge" as well. 

"Oh! what a tangled web we weave, When first we practise to deceive!" 

Enough of poetry -- the main point, if one has scientific inclinations, is that it is incumbent upon MPP and his colleagues to prove that maybe 50 spotted dolerite monoliths and maybe 30 foliated rhyolite monoliths were present at one time at Waun Mawn.  They carry the burden of proof, and they have to deliver.

On two separate occasions I have hunted across the dig site (which I now think involved  c 2000 sq m of excavations), looking for chips, packing stones or even "forgotten monoliths"  made of either spotted dolerite or foliated rhyolite.   I cannot be 100% certain, because I cannot know what has been found by the diggers and sent off for geological identification -- but I have not found a trace of either rock type.  (Spotted dolerite is fairly easy to spot, in the field,  since the whitish crystal clusters are more resistant to weathering then the "matrix" of the rock, making them stand proud.  So the rock surface tends to be lumpy or knobbly..... unlike the smooth surface of stones made from unspotted dolerite.)  There are plenty of  unspotted dolerite boulders,  slabs,  and pillars all over the place, and many dolerite cobbles and smaller pebbles too -- but they are all local.  There are no rhyolite pillars or monoliths, standing or recumbent.  There are some rhyolite and volcanic ash cobbles and stones, but they do not seem to be identical to those outcropping at Rhosyfelin.  In this area the ice has come in from the west and north-west; so "erratic material" from either Rhosyfelin and Carn Goedog would be a good indicator of human transport.  But there is nothing.

I'm not sure why this little pile of stones was left on the turf.  I assume that they have been gathered up and interpreted as "packing stones" from one of the supposed stone sockets?  They are made of dolerite, volcanic ash, rhyolite and meta-mudstone -- all quite local.

On this geological test alone, the proto-Stonehenge hypothesis is rejected.

One final thought.  Dave mentioned to me that one idea being bounced around is that bluestone monoliths might have been stored at Waun Mawn without actually being planted into the ground.  I love it!  I have this picture in my head of lovely rows of elongated bluestone monoliths on the open moorland, with 50 neatly arranged spotted dolerite monoliths over by here, and 30 foliated rhyolite monoliths over by there, with a  sales rep offering them (with free delivery, of course) to the highest bidder..........

Once these fantasies get a hold of you, there is no knowing where they will lead you.

Thursday, 11 October 2018

Abermawr -- the new Quaternary stratigraphy

This is a gorgeous photo showing the raised beach sitting on its rock bench and sealed beneath pseudo-stratified brecciated slope deposits (we used to call that  layer "the lower head"........  courtesy Pembs Coastal Photography, whose pictures are far better than mine!  The bit in the box is the enlarged section of the upper part of the parent photo.

As we can see, when we examine this image carefully, there is a wide range of rock types in the raised beach.  That almost certainly signals the incorporation into the beach of pre-Ipswichian glacially derived materials.  How else would they have got here?  From the Anglian glaciation?

So let's examine the rest of the modern stratigraphy. The full sequence looks like this:

8.  Blown sand, loess and colluvium, incorporating modern soil (c 1m)
7.  Upper brecciated slope deposits (c 2m)
6.  Reddish stained colluvium -- a pro-glacial redeposited layer (c 2m)
5.  Glaciofluvial sands and gravels incorporating flowtills (c 2m)
4  Mobile meltout till and flowtill (c 3m)
3.  Irish Sea till -- massive, with shells and carbonized wood (c 4m)
2.  Brecciated slope deposits with rockfall detritus close to broken-up cliff face (c 3m)
1.  Raised storm beach on rock bench (c 1m)

Thicknesses are approximate -- no part of the cliff shows the full stratigraphic sequence.  In general, the lower part of the sequence is in the north and the  upper (younger) deposits are best preserved in the south.  The upper brecciated slope deposits are, however, best preserved near the top of the highest cliffs, close to a convenient bedrock source.  They appear to be approximately equivalent to the reddish stained colluvium.  Together, deposits 6 and 7 used to be referred to as "the Abermawr rubble drift".

The raised beach (1) appears to be around 1m thick, but exposures are intermittent and sometimes masked by debris falls from above.  It's in a very risky position.  I tried to climb up to it once, and had to give it up, fearing for life and limb.

The lower brecciated slope deposit (2)  is clearly just a jumble of rockfall debris close to the rock outcrops, but further away there are signs of rough stratification, as seen in the exposures 50 years ago.  Now, as then, we can assume that these rough stratifications within the unit do represent some climatic oscillations, maybe over a very long period of time.

Broken rockfall debris within layer 2 -- note the heavily weathered igneous erratic boulder embedded within it.

Close-up of another heavily weathered igneous erratic in the lower slope breccia.

Lower slope breccia above the bedrock contact.  Here there is a rough stratification and the deposit is matrix-supported.

The Irish Sea till (3) has been well described in earlier posts and in the literature.  It is now known to be a lodgment till consisting for the most part of old sea-floor material from Cardigan Bay, dredged up and mixed with far-travelled materials as the Irish Sea Glacier came in from the north-west.  There are complex thrusting, folding and other internal structures.

The base of the Irish Sea till layer -- stained reddish by oxidation associated with water penetration from the  brecciated layer below. The upper part of the breccia has been churned by overriding ice and now incorporates some erratics carried by the glacier in its basal layer.

Massive Irish Sea till with an oxidised layer above, grading into flowtill (?) and mixed sediments with a lower clay content.

Above the lodgment till layer, which is grey or blue in colour when fresh, there is a complex layer with a foxy red or brown colour (the result of iron-staining) in which patches of flowtill and some detached masses of lodgment till exist in a complex relationship (4).  This can only represent the ice watage phase of the Irish Sea Glacier.

Above this, layer (5) consists mostly of water-lain materials, although some masses of flowtill are incorporated.  Collapse features and other structures indicate the existence of wasting ice masses at the time of deposition.

The junctions between layers 3, 4 and 5 are in places difficult to discern.  They must be very closely related in age.

Glaciofluvial deposits incorporating masses of assumed flowtill -- stratigraphically above the Irish Sea till layer.  Above the lighter coloured sandy layer in the centre of the photo, we can see the junction with the overlying foxy-red colluvium and redeposited till layer.

Redeposited glacial and glaciofluvial sediments towards the southern end of the exposure.  The greater the distance from the Irish Sea till exposure, the smaller the number of erratic clasts contained in the reddish silty and sandy matrix 

Colluvium with very few large erratics, near the southernmost part of the cliff exposure.  Note the rough stratification.

Recent exposures near the southern end of the cliff section reveal that the reddish stained colluvium (6)  is made for the most part from the material originating in layers 4 and 5.  The clay content is low, and this indicates that water has been of great importance in the deposition of the layer.  Sands, gravels and blown sand may all be incorporated; but the greater the distance from the Irish Sea exposure, the lower the content of large boulders and cobbles.  As one approaches the rocky crag which has recently emerged in the storm beach, the material exposed is best interpreted as a colluvial layer incorporating redeposited till and glaciofluvial materials.  As we have remarked in another post, this is remarkably similar in appearance to the "redeposited till" seen on the south Pembrokeshire cliffs, on Caldey Island, and in numerous exposures on the coasts of the Isles of Scilly.  At Westdale Bay there is a great thickness of this material, with marked pseudo-stratification.

Layer 7 (upper brecciated slope deposit) is only obvious to the untrained eye near the top of the highest part of the cliff, with signs of incorporated material from the glacial deposits below.  Most of the angular bedrock fragments have come from exposures upslope.  On the southern part of the exposure there was no adequate supply of frost-shattered or rockfall material, and so the slope breccia is not present at all.  It seems to be equivalent in age to the "redeposited till" and colluvium allocated to layer 6.  Together, these two layers comprise the "rubble drift" of earlier studies.

Layer 8, made up of blown sand, loess and colluvium, appears to be rather modern, and the modern soil has developed within it.

Blown sand and organic-rich soil horizon at the top of the cliff section.

In terms of the age of the deposits seen here, no evidence has emerged which casts doubt on the sequence which I proposed in 1965.  The raised beach is assumed to be Ipswichian or Eemian in age. The lower rockfall and slope breccia layer must span the early and middle Devensian, with subtle changes in stratification, texture and colour maybe representing environmental or climatic oscillations.  The flowtills and glaciofluvial deposits must represent the ice wastage phase, maybe over just a few centuries.  A cold episode following that (and maybe involving permafrost conditions) was responsible for the formation of the uppermost slope breccia.  This appears to be approximately equivalent in age to the redeposited till and colluvium.  The blown sand must have accumulated during the Holocene And the surface soil layer is still forming today.  

Where does the submerged forest come in this sequence?  It must rest upon the redeposited till and colluvium, and it must be approximately equivalent in age to the blown sand; maybe the sand dunes and the forest co-existed in close proximity.

Remnant of the submerged forest exposed in the sandy beach at low tide.

Sorry this is a rather protracted description!  I wanted to get it recorded while I still have the energy to do it!  It is, after all, one of the top 50 Quaternary sites in the UK, and possibly the most important in Wales, in that it holds a record of a complete glacial - interglacial cycle over a period of well over 100,000 years.

Dem crem bones -- CA overwhelmed, and BA underwhelmed......

There is more journal coverage relating to that infamous Nature article about strontium isotope dating of cremated bone fragments from Stonehenge.  But are we beginning -- not before time -- to see some signs of careful scrutiny and independent thought?

In the latest issue of Current Archaeology there is an article by Kathryn Krakowka,  accessible here:

The longer, fuller article, is behind a paywall, and if it says anything interesting, somebody will no doubt enlighten us.  But  the author is clearly not inclined to delve too deeply, and what she says is based  largely on that infamous OU press release which we have already discussed.  Lots of nice free publicity for Christophe Snoeck and his colleagues.

Then we turn to British Archaeology.  The headline (on p 7 of the Nov / Dec issue) is "Stonehenge drew visitors from the very start."  Well, we knew that anyway -- almost everywhere in Britain drew visitors from the very start, some more than others.  But the author of this piece seems to have read the article, rather than just the press release, and a degree of scepticism is apparent.  Mind you, he was not so sceptical as to have ignored the "Nature" article altogether -- but maybe that would have been a step too far.  On the supposed links -- for one individual -- between Stonehenge and West Wales, he is circumspect, to say the least.  He says:  "..... prompting some archaeologists to link the people (ie those with higher isotope "signatures" ) with  the transport of the bluestones before 2500 BC...."  Later in the article he says "The data are complex to interpret, and are affected by unknown factors........"

The killer item in the piece is the map which illustrates the article.  It's supposed to show the links between three individuals and likely home areas.  The caption should have been "If anybody can see a link here between Preseli and Stonehenge, he or she has a much more vivid imagination than I do."

The author of the piece was clearly completely underwhelmed.

Abermawr, Flimston, Caldey, Carnew and Popplestones -- five of a kind

When I was at Abermawr the other day, I was struck by the similarity between the deposits near the outer end of the northern "drift cliff" and the deposits found at Flimston and Caldey in South Pembrokeshire,  at Popplestones on Bryher (Scilly Isles) and at Carnew Point, St Agnes (Scilly Isles).    Many other sites too -- but that list is enough to be going on with.  Some of these sites are inside the currently accepted Devensian glacial limit, and others are outside. That limit is going to have to be modified, as I have suggested many times on this blog.  

So what are the characteristics that these deposits have in common?  Here are some images:


Ballums Bay, Caldey

Flimston, South Pembrokeshire

Popplestones, Bryher, Isles of Scilly

Near Carnew Point, St Agnes, Isles of Scilly

We need to get a bit technical.  First the deposits are matrix-supported diamictons -- where cobbles and pebbles of many different lithologies, shapes and sizes are supported in a matrix of finer material.  Second, the matrix does not have very much clay in it -- unlike, for example, the Irish Sea till at Abermawr and the massive "Celtic Sea till" at Chad Girt on St Martin's in the Scillies.  Third, many of the contained stones are faceted, fractured and even striated -- good indicators of a glacial origin.  Fourth, there is a reddish or rich brown colour, indicative of oxidation and iron-staining.  As many have noticed, that characteristic is often associated with colluvium or hillwash, and with windblown deposits -- and these deposits are associated particularly with relatively vegetation-free environments in proximity to glacier fronts.

There are local variations of course.  At Ballum's Bay the deposit has the reddish colour associated with the Old Red Sandstone, across which the incoming ice passed before reaching the Carboniferous Limestone at the eastern end of the island.  At Carnew Point on St Agnes, the matrix comprises a mixture of windblown silt and colluvium and "grus" which is the product of granite weathering.  At Popplestones the reddish colluvium is ubiquitous.  At Flimston there are many beautifully rounded quartz pebbles derived from patches of Oligocene "gravels" and pebble beds which have been destroyed by overriding ice and incorporated into till.  At Abermawr there is a real mess, with the same mix of stones as in the underlying Irish Sea till and with patches of flowtill, glaciofluvial sands and gravels, colluvium and periglacial slope deposits all scrambled together.

My conclusion is that all these deposits are clear indicators of glacial activity in the neighbourhood.  But they are probably not primary tills in the positions where they were originally emplaced.  They have been mobilized in very wet (ice wastage) conditions -- moved downslope either on dead ice surfaces or on ground slopes, and redeposited a little distance away.  How far?  My estimate, in all cases, is somewhere between 10m and 50m. From what I know of ice wastage environments, transport of a deposit that still contains many of the characteristics of a primary till is unlikely to have been maintained for a greater distance except in exceptional circumstances -- for example in a catastrophic liquidised debris blow in a long gully.

So I think we are looking here at "paraglacially redeposited tills" in the modern phraseology.  

I'll do another post on the current exposure at Abermawr, which has led me to this conclusion.


Here is a definition from Olav Slaymaker: 

"..........It is argued that the term ‘paraglacial’ defined as ‘non-glacial processes conditioned by glaciation’ describes landscapes that are adjusted neither to Last Glacial Maximum nor to contemporary geomorphic processes. Where a landscape is paraglacial it can be characterized in terms of rate of change and trajectory of that change. It cannot be defined in relation to glaciers (as in proglacial) or by cold-climate processes (as in periglacial). Almost all paraglacial landforms and all paraglacial landscapes are transient and transitional. An interesting challenge of paraglacial landscapes is then to determine their rates of change; how far they have advanced along the trajectory from glacial to non-glacial; and how to recognize empirically the temporal and spatial relationships between proglacial, periglacial, paraglacial and fluvial landscapes.

Wednesday, 10 October 2018

The Cnwc yr Hydd quarries -- early nineteenth century?

I have been looking at these quarries again today -- and I have found another one, on the eastern flank of Banc Du, to the north of Gernos Fach Farm.  Like the others, this is a meta-mudstone quarry.

When I put up a post a few weeks ago, suggesting that the quarries are modern, opened up to provide meta-mudstone slabs for building purposes, I was challenged on another Facebook site as follows:  "Your hypothesis.  You carry the burden of proof. Now prove it!"  Perfectly fair and reasonable, since that's what I say to our friend MPP and to various others!

I gave some supporting evidence in my earlier post:

So we have slabs used in abundance at the ruined cottage called Ffos-felen.  Today I looked at the ruined farmhouse at Tafarn y Bwlch, and this is what I found:

As at Ffos Felen, the slabs -- of many different sizes -- are used to level off the courses, given the rough shapes of the erratic igneous boulders used for much of the building.

Then I went off to the top Garfeth Cottage, adjacent to a free-flowing spring, and this is that I saw:

Some of the cottage walls, like the walls at Tafarn y Bwlch, were made of a mixture of dolerite boulders and meta-mudstone slabs, but the wall in the photo above is almost exclusively made of the sedimentary slabs.  There used to be mortar, but most of it has crumbled away. (Interestingly enough, this cottage was still occupied in 1946.  Our old postman was born in it.)

So there is no point in arguing or speculating any further.   The quarries are relatively modern, probably about 200 years old.  Maybe some of them were used earlier, maybe back to the Middle Ages, for the building of cottage walls -- and I suppose there is a possibility that there was some exploitation in prehistoric times as well -- given that the slabs are very easy to extract from the ground and to carry away. Another factor is the relatively dry nature of the ground underfoot -- this is dry heath and not peat bog, so the going is pretty good, even in the middle of winter.  All of the quarries are easily accessible with horse-drawn carts and sledges, and many of these wide tracks can still be traced on the ground and on satellite images. And a final factor -- all of the quarries are located high up on the hillsides and near the hill summits, so transport of the stone slabs from quarry to building site was always downhill.  Easy!

Since the last great phase of building in this area, around the fringes of the commons, was after the Napoleonic Wars, I would date the creation of most of these quarries to the period 1810-1830.

M'Lud, I rest my case........

Waun Mawn / Tafarn y Bwlch standing stone gallery

Today I was up on the mountain in positively balmy weather.  Our (no doubt short-lived) Indian Summer.  But the sunlight was perfect for pics, and here is my collection.

This is the standing stone on the perimeter of the putative stone arc or circle -- left alone by the diggers in both 2017 and 2018 

This is the most impressive stone on the moor. Standing on its own to the north of the Gernos Fach track.

This is the pair of smallish leaning stones to the south of the Gernos Fach farm track

This stone is embedded in an embankment at the side of the B4329 road a few hundred metres uphill from the cattle grid

This is the recumbent stone which  is assumed to be a part of the putative stone circle.

This is a semi-recumbent stone alongside the entrance to the 27m ring cairn (?) not far from Gernos Fach Farm

This is a small fallen stone (socket alongside) on the ridge to the west of the Cnwc yr Hydd summit

This is quite an impressive gallery, incorporating three standing stones, three leaning (all of which can be referred to as slabs), and two recumbent.  I know that MPP and his digging team think there are other recumbent or fallen stones in the arc of the putative circle, but I am not convinced by those.

But there was certainly a lot going on here.  The "stone circle" is, I think, the least convincing and least interesting feature on the moor.  There is at least one beautiful 27m embanked ring cairn, what appears to be a round house, at least a dozen old sockets or extraction pits, traces of embankments and stone walls, and something that looks as if it might be a destroyed cromlech incorporating a large quartz boulder and an infill of smaller stones between fallen supports.  The capstone has gone -- if it ever was there.  Dave Maynard thinks there is a trace of a rectangular building on the moor as well, but I have not been able to find that........

All in all, abundant signs of occupation in the Neolithic and Bronze Age.  I can see no great reason to refer to this prehistoric landscape as a "ritual landscape"  -- I reckon that people just lived here, and did whatever they had to do to survive, in those good old days.


PS.  One interesting point about these and other standing stones in Pembrokeshire.  It's true that some of them are slim and elongated pillars.  But the majority are not.  Slabs, stumpy pillars and elongated boulders seem to be preferred.  Conical and triangular shapes occur as well.   For a start, these irregular shaped stones could be picked up almost anywhere, and secondly, they were probably more stable when placed securely in the ground.

PPS.  I'm pretty sure this is a standing stone too, on the roadside near Ffos Felen ruined cottage.  It's actually just 400m to the east of the proposed stone circle site.  It's  been built into a hedge at the side of the road -- and it seems much too chunky and heavy to have been brought in by a farmer in recent times just to serve as a gatepost.  Anyway, there is no hole drilled into it.......

Monday, 8 October 2018

Glacial geomorphology for archaeologists

Today I needed to scan in some of the jackets of my old books for the Society of Authors.  It occurred to me that they might be useful for archaeologists in that they are nice and simple to read -- and free of much of the technical stuff that has preoccupied glacial geomorphologists in recent years.  There is quite enough glaciology in these texts to be going on with, too.  Since all 3 books are out of print, you might be able to pick them up somewhere for a very modest price!

The one written by David Sugden and myself remained in print as the standard university text for almost 30 years, and was reprinted many times.  The other two are more popular texts.  I edited "Winters of the World" for David and Charles and Wiley,  and since the deadline was very tight I actually ended up writing several of the chapters for which the contracted authors had not delivered their texts.  Advice to future editors:  don't do it!!  Anyway, the book was very popular, and sold out quickly.  Sadly, it was never reprinted.

The one called "The Ice Age" was published by Collins and then pinched, translated and republished by a Russian publisher, and the first thing I knew about it was when somebody found a copy somewhere and told me about it.  Needless to say, they never paid me a penny -- or a ruble.......

Saturday, 6 October 2018

On the significance of Mendip for Quaternary studies

The Mendip Hills (or plateau, if we want to call it that) have been somewhat neglected by the Quaternary science community, in spite of the huge amount of work by those interested in karst landscapes and cave science.  For example, there is hardly any mention of the Mendips in the big GCR Review volume published in 1998.  The QRA Somerset Field Guide, published in 2006, gave more attention to the Mendips, but the greatest emphasis was given to the glacial and related deposits at Court Hill, Yew Tree Farm, Kenn, the Gordano Valley, Nightingale Valley and a few other locations to the west.  There are still statements in the literature to the effect that "Somerset was not glaciated" in spite of the proved existence of till at Greylake, about 12 miles inland on the Somerset Levels.

And yet, as I have suggested many times on this blog, there are abundant features that point to periglacial and glacial "interference" during the Quaternary.    There is an extensive plateau that must have supported extensive snowfields, if not glacier ice, during the known glacial episodes.  There are impressive gorges (at Cheddar, Burrington Coombe and elsewhere) which are difficult to explain except by reference to vast volumes of  water that might have a snowmelt or glacial melt origin.  There are karst landscapes and limestone pavements which can be examined in detail.  There are caves and cave deposits which contain clues to Quaternary events and to human occupation history.  There are somewhat mysterious deposits around the flanks of Mendip which have not been adequately examined.  Dry valleys at Rickford and elsewhere are really quite peculiar.  And there are anomalously large valleys to the east of Mendip which are difficult to explain by normal fluvial processes -- even if operating over a long period of time.  Lake overspills and drainage directed southwards by ice?  Quite possible.

I'm intrigued that Gilbertson and Hawkins postulated a big ice lobe pushing eastwards all the way to the chalk escarpment, as suggested on the above map.  But they did not think that ice overrode the Mendips.  That conclusion needs to be tested..........

One thing is certain -- Mendip must bear the scars of the Quaternary, and they must be far easier to interpret here than in the Quantocks, Cotswolds, Brendon Hills etc, where there are no substantial cave systems, gorges, or extensive rock outcrops.

There are glacially derived deposits to the east of Mendip and the SE of Bath; Geoffrey Kellaway and others drew attention to these many years ago, and the BGS now assigns them to the "Kenn Formation" -- thus linking them with one of the key locations near the Bristol Channel coast. (Thanks to Alex for pointing that out to me.......)  If ice reached that far east, it is inconceivable that the Mendips were NOT affected by both periglacial and glacial processes.

My own instinct is that if Dartmoor was glaciated -- and that now looks pretty convincing -- then Mendip -- further north and close to the large Welsh Ice Cep -- must also have been glaciated.  And it needs to be examined if we are ever to find out where the Anglian ice edge may have been located.

Watch this space.......