Why the "human agency" thesis cannot be the default preference

A stone with a mind of its own.......

I have many discussions with experts off the record, and in one recent exchange of opinions with a senior geomorphologist we have agreed to differ on what the "default hypothesis" should be, given that there is no "smoking gun" or "killer fact" in the glaciers versus humans debate.  His view is essentially that of Prof James Scourse, who said many years ago that since there is no firm evidence of glaciation on Salisbury Plain we must therefore assume that glacial entrainment and transport of the bluestones was effectively "impossible" -- and that no matter how unlikely it might seem, the human agency thesis has to be the one to go for.  (The reason for that is that we know that Neolithic people were rather clever, and if they were clever enough to know quite a lot, they probably knew how to carry large stones over long distances........)

I disagree fundamentally with that.  Nobody should ever say that the glaciation of Salisbury Plain was impossible, especially since modelling shows that it was indeed possible, and since there are glacial deposits in the SW counties including Somerset.  The Stonehenge bluestones themselves look like a glacial erratic assemblage, and if they look like erratics they may well be erratics!  We must also remind ourselves that there is no physical evidence of any sort which supports the idea of either Neolithic quarrying in Pembrokeshire or long-distance human transport of the bluestones, and which withstands scrutiny.

In those circumstances the balance of probability must lie with the glacial entrainment and glacial transport thesis.  Some evidence trumps no evidence, any time.   In summary:

Ten fundamental problems with the human quarrying & transport thesis


1. There is no sound evidence from anywhere in the British Neolithic / Bronze Age record of large stones being hauled over long distances (more than 5 km or so) for incorporation in a megalithic monument. The builders of Neolithic monuments across the UK simply used whatever large stones were at hand.

2. If ancestor or tribute stones were being transported to Stonehenge, why have all of the known bluestones come from the west, and not from any other points of the compass? Were belief systems and "local politics" quite different to the north, east and south?

3. There is no evidence either from West Wales or from anywhere else of bluestones (or spotted dolerite or Rhosyfelin rhyolite in particular) being used preferentially in megalithic monuments, or revered in any way. The builders always used whatever was available to them in the vicinity, and it can be argued that stone availability was a prime locational determinant for stone settings.

4. If long-distance stone haulage was "the great thing" for the builders of Stonehenge, why is there no evidence of the development of the appropriate haulage technology leading up to the late Neolithic, and a decline afterwards? It is a complete technological aberration.

5. The evidence for Neolithic quarrying activity in key locations is questionable. No physical evidence has ever been found of ropes, rollers, trackways, sledges, abandoned stones, quarrymen's camps, or anything else that might bolster the hypothesis. The so-called “engineering features” are entirely natural.

6. The sheer variety of bluestone types (near 30 when one includes packing stones and debris) argues against selection and human transport. There cannot possibly have been ten or more "bluestone quarries" scattered across West Wales.

7. Bits and pieces of experimental archaeology on stone haulage techniques (normally in "ideal" conditions) have done nothing to show that our ancestors could cope with the sheer physical difficulty of stone haulage across the heavily-wooded Neolithic terrain of West Wales (characterised by bogs, cataracts, steep slopes and very few clearings) or around the rocky coast. The one reasonably "authentic" project (the moving of the "Millennium Stone" in the year 2000) was a shambles and a disaster.

8. Neither has it been shown that the Stonehenge builders had the geographical awareness and navigational ability to undertake long and highly complex journeys with very heavy loads.

9. And if there was a "proto-Stonehenge" somewhere, built of assorted local stones and then dismantled and taken off to Stonehenge, where was it? The mooted "Preselite" axe factory has never been found, and neither has the mythical Stonehenge precursor.

10. Analyses of bluestone monolith stone shapes does not suggest that elongated “pillars” were preferred. Slabs, stumps and boulders of all shapes and sizes are highly suggestive of a glacial erratic assemblage.

Bluestones 34 and 35a

Bluestone 35a, exposed in the pit opened by Darvill and Wainwright in 2008.  (Source: Tim Darvill)

I'm happy to draw attention to the 2009 report by Darvill and Wainwright -- dealing with the main findings from the 2008 Stonehenge dig.  Interesting material, written in a lively and accessible style.

https://www.researchgate.net/publication/231972157_Stonehenge_excavations_2008

• DOI: 
• 10.1017/S000358150900002X

Much of the report is about the Stonehenge Layer, but this is what the authors say about the two bluestones which they encountered.

Let us move hastily along to the next period of Stonehenge, where three sockets relate to stones that are still visible above the ground surface. Stone 35a and Stone 34 are both part of the Bluestone Circle that is such a striking part of all the later phases of the monument. Both stones are still above ground. Stone 35a is a massive block, but projects only a few centimetres above ground level (fig 9). Petrologically speaking, this one is very close to the material from Carn Menyn to which Geoff referred earlier. I think that you can see straightaway that this is the natural patina on the rock and it has been smashed up in relatively recent times, sufficient that no new patina has developed on the exposed faces. As we shall see a little later, that is not surprising. But there it is in its place, going down the best part of a metre into the ground.

The next one along is Stone 34. It is a beautiful stone that extends into the ground more than a metre, so that less than one-third of it is sticking up above the ground and the rest is now under the ground. You can also just make out a massive hole next to the stone, which is partly filled with concrete, put there when Atkinson refilled the trench, probably to give it support. It is fairly certain that when Atkinson was digging here Stone 34 was loose and you could move it, and, given the size of the hole, there is no question that material could get into the ground alongside that stone.

Stone 35a is particularly spectacular, showing a very complex history.  It has a flattish base, and sits on the chalk bedrock in quite a stable fashion.  The side facing the camera is clearly a fracture plane which is heavily weathered.   How did the breakage occur, and when did it happen?  We can see several other fractures within the rock, so it is in a dodgy state, and presumably always has been.   The relatively fresh and unweathered upper surfaces show the spotted dolerite in all its glory; these appear to be fresh fractures, and I think Darvill and Wainwright are right in their conclusion that these breakages are relatively recent in the life of the stone -- maybe dating from the "destruction of the bluestone circle."  They say that two - thirds of the bluestone circle has been smashed up, carted away and incorporated into the Stonehenge Layer -- but I think that is an unsupportable statement, since nobody knows how many bluestones were in the circle when it was at its most complete --  and there is no evidence to support the contention that it ever was "complete" as shown in all the Stonehenge publicity material.  I have argued many times that the whole monument was abandoned in an incomplete state, because the builders ran out of stone........

The pic of stone 34 is a nice one too.  This one is apparently complete -- although its base was not fully excavated by Darvill and Wainwright.  As fine a weathered and battered glacial erratic as one is ever likely to see.

Blogger infuriates the bloggers

There is a huge row going on in the blogging community about recent changes made by Blogger / Blogspot by Google, the owner.  I had a few glitsches earlier on, when I could not see incoming comments and received no notifications of them by Email.   I was accused of selecting comments and blocking off those whose comments I did not want to acknowledge, as some will recall.........

I thought the problem had been sorted out, but now the "Email notification" process has been stopped completely, and on the Blogger discussion forum this is by far the biggest cause of anger.  I have complained, as have thousands of other bloggers.  Blogger is not even bothering to respond, which does not do them a lot of good.......

I have a feeling that this is all part of a strategy towards increased "monetisation" by Blogger and Google -- they have "modernised" the way that Blogger works, placing much more emphasis on adverts and the sale of products and services.  Blogger wants every blog to bring with it a revenue stream.  I have steadfastly resisted the pressure to place paid adverts on my site, and will continue to do so.

But in the meantime, apologies to those who want to comment on my posts -- I may or may not see your comments, and they may just get tangled up in the spam which is removed from my mailbox by my preference settings.

We await developments -- at the moment nobody knows whether Blogger will respond to the anger being expressed by most of their blogging clients.

The conversion of Richard Atkinson

Prof Richard Atkinson in the AP film, dated 1990

 Olwen Williams-Thorpe, one of the leading researchers in the OU study

We learn something new every day.  I have been looking at this old Associated Press film (about 5 mins) produced in May 1990, in association with the big OU study undertaken by Richard Thorpe,  Olwen Williams-Thorpe and others;  and in it I discover that towards the end of Prof Richard Atkinson's life he accepted that he had been wrong for 40 years in arguing vociferously for the human transport thesis and against the glacial option.  So there was a miraculous conversion on the road to Stonehenge.  It appears that in my new book I should have been kinder in my assessment of his work and his contribution to the transport debate -- so I owe him a posthumous apology...........

Atkinson died in 1994, four years after this film was made -- so it must have had his approval.  

http://www.aparchive.com/metadata/UK-SQUARING-THE-STONE-CIRCLE/117b76a27438c30e3e9e5c45e8238253?

I particularly love the little clip of the late Geoffrey Wainwright, who says (in a roundabout sort of way) "Forget these geologists.  They know nothing.  We archaeologists are the experts -- trust us and believe what we say....."    Sadly, Geoffrey died not so long ago, but that complacent and patronising attitude is very much alive in the archaeological community.

New book duly launched

There was a good audience for my book launch and talk last night in Newport.  My talk was entitled "Neolithic bluestone quarries:  the facts and the fantasies."  There were several archaeologists in the hall, and interestingly enough, not one of them spoke up in defence of the archaeologists who have been working with Prof MPP, or in defence of the good professor's narrative.  After that, we enjoyed a good discussion on a range of topics, including some quite detailed glaciology and on the usual question of erratic distributions.

One of the most intriguing questions -- for which nobody had a satisfactory answer -- was this: "How do they get away with it?"  In other words, where is the scrutiny from the archaeology establishment?  Why does funding continue to flow into the Pembrokeshire digs even though over seven years they have told us NOTHING new about either the Neolithic or the Bronze Age in this part of the world?  They have told us nothing new about Stonehenge either.

Anyway, a pleasant evening, and the tea and rock cakes went down well.  (Red wine accompanied by nibbles is so old hat........)

Readers of this blog will be intrigued to know that following the Fox News coverage of the publication of the new book, the story has made the pages of many of the regional newspapers in Australia.  There has also been good coverage in Romania, Croatia, the Arab world, Spain, Italy and many other countries.  The "new and revolutionary" glacial transport angle is the one they have picked up on -- and as one might expect some of the write ups have consisted of garbled nonsense.

I'm rather intrigued by the thought of a press report in the WaggaWagga Courier (if there is such a thing) in the Australian outback, describing how a Welsh scientist claims that a glacier built Stonehenge, immediately following a report of a dingo chasing half as dozen sheep near the local water hole.

Late Pleistocene environments

Thanks to Chris for sending the PDF of an interesting lecture in the Netherlands about the evolution of the rivers and the landscapes.Rather difficult for non-Dutch speakers to follow, but Chris wondered if there was anything radical in there relating to ice edges etc.  The short answer is "No" -- the above map, which is almost too fuzzy to interpret properly, shows the widely accepted Late Devensian (Weichselian) ice edge for Northern Europe -- which is somewhat redundant in that there are many tweaks around the edges, not least in Western Britain.  This is a point made by Prof Danny McCarroll in his recent review of my new book.

Chris wondered whether the area coloured yellow shows a more extensive glaciated area, incorporating much of southern England including Kent.  No -- that area is the area assumed to have been effected by permafrost, with tundra vegetation.  I think the map actually shows current thinking on the ecology / vegetation patterns of Europe around 20,000 years ago.

This is another interesting diagram, showing climate change in western Europe since the wastage of the last glaciation ice in the Alps, the British Isles and Northern Europe.

Most of what is on the diagram is fairly obvious, even to a non-Dutch speaker.  Note the gradual improvement of climate between 18,000 and 15,000 BP, the complex oscillations between 15,000 and 12,000 with the Older Dryas and Younger Dryas (Zone III) phases, and the relatively stable climate since then.  This time scale does not quite coincide with others that have been published -- I wonder if the author is using BC/AD as his timescale, rather than BP?

Digging then and digging now

Two photos from the album, one from 1913 and the other from 2015.  The black and white one is from an old post-card.

Ah -- how times have changed -- or have they?

My nice little dykes -- and the geological map

Cataract where the River Clydach cuts through one of the dykes in a narrow gorge

The smaller of the two dykes outcropping above the river

The larger of the two dykes which forms a distinct cliff  above the river

I live in Cilgwyn, not far from the Bluestone Brewery which is much patronised by the archaeologists every September, and on my land there is a very beautiful river valley.  The river cuts through two dolerite dykes which have a major influence on both valley shape and gradient.  Elsewhere we find Abermawr shales and mudstones, and meta-mudstones adjacent to the dykes where there has been a moderate degree of metamorphism or alteration due to baking.  Where the hard rock outcrops, the valley sides are very steep indeed, and the river tumbles down through a series of cataracts.Above and below the dykes, the valley is much more open, with grassy meadows on the floodplain, more gentle sides and a river which is much more placid in appearance.  All good standard geomorphology -- and exactly what one one would expect.

The point of this pleasant little tale (apart from the fact that I am rather chuffed to be the proud owner of two dykes) is that the geology map is highly generalised, and misses out on multiple details of rock distributions and outcrops.   I know of other dykes in the neighbourhood which are not shown at all on the geological maps, as well as other outcrops of volcanic ashes and rhyolites.  And there is great variation within outcrops which are shown as being relatively uniform on the maps.   I have flagged up mapping inaccuracies  on Waun Mawn, on Brynberian Moor and in the Brynberian Valley as well.  I am not criticising the BGS surveyors who have produced fantastic maps over the years -- just pointing out that if the maps are not to appear too complex, there has to be an "appearance" of uniformity if the map is to be of any practical use to farmers, planners and the general public.

Against this background, I have always been critical of the claim from Ixer and Bevins that they have provenanced some of the foliated rhyolite fragments found at Stonehenge to "within a few square metres" on the rock face at Rhosyfelin.  For a start, I have pointed out that none of the thin sections featured in the publications provides an exact match.  And secondly, we have never seen an adequate rebuttal of the point made by me and many others --  namely that if a particular foliated rhyolite petrography is seen at point 8, it must also be observable at multiple other locations where that particular foliated layer outcrops at the ground surface.  Even if rock samples have been taken from 30 sampling points within the Brynberian Valley, we simply do not know enough about the real and complex local geological map to justify what is really rather a wild and exaggerated claim about provenancing accuracy.

Quote of the day

Thanks to Tony for this one:  "The human transport theory is looking increasingly far-fetched."  Nice one!  I wish I had thought of it myself........

While the debate has concentrated on the bluestones for many years, I get a sense that it is now moving to a consideration of where the sarsens came from too.  As I suggest in my book, it's reasonable to assume that ALL of the stones used in the stone settings at Stonehenge were collected from the neighbourhood.

I suspect that as more and more senior academics pour scorn on the so-called "quarrying evidence" from Rhosyfelin and Carn Goedog, as they surely will, the archaeologists will be pushed further and further into a corner, from which there may be no escape.

Another quarrying sceptic

This is from another pre-publication review of the book from a senior academic whose specialism is geomorphology.  He hasn't given me permission to use his name, but this is word-for-word!

First of all, I enjoyed reading the book. Thanks for the opportunity to do so. Your passion for the subject shines through! I also read The Bluestone Enigma. I can see why you wanted to produce an updated version of the story, in particular because of the excavations at Rhos-y-felin. I agree with you that the archaeologists have over-interpreted the flimsiest of evidence and invented an imagined Neolithic mindset based on very little (if any!) in the way of facts. They damage rather than enhance the transport origin hypothesis as a result. The Rhos-y-felin site itself is unconvincing as a Neolithic quarry, and so far no forthcoming convincing evidence of human industry there has appeared in print as far as I am concerned. You convince me that the Bluestones are actually a rag-bag of rocks of South Wales provenance and not rocks only from one or two locations in the Presell Hills. This does need to be emphasized and is not what most people would have in mind.

I must be honest and state that the above para is followed by an expression of doubt about the glacial transport thesis too, and my reviewer reiterates that there is no "killer fact" which demonstrated that glacier ice might have reached Salisbury Plain.  I agree with that -- and of course, in the book I refer to the balance of probabilitiy.  He cites a number of examples where the evidence of ancient till and ancient erratics is open to interpretation, and refers to assorted technical matters relating to glacier mechanics etc.  I'll do another post on these comments, and those from other reviewers, before too long -- there are many perfectly valid points that deserve to be debated.

That having been said, if one is unconvinced by quarrying and human transport, and unconvinced by the glacial transport theses, what is left?  Merlin the Wizard, or the activities of aliens?

Fossil ice wedge, Manorbier

This is a very fine fossil ice wedge, seen in the cliff face at Manorbier, overlooking the beach.   There's broken bedrock at the base, then about 1.5 m of pseudo-stratified ORS head, and about 50 - 75 cm of sandy loam and modern soil.  The wedge fill consists of sandy loam and small fragments of soliflucted ORS debris, with one or two larger fragments as well.  Note how many of the fill fragments are arranged vertically.  There is no till exposed here.    But clearly permafrost was present after the formation of the head horizon, at the time of sandy loam / colluvium accumulation.

Were features such as this formed at the peak of the Late Devensian Glaciation -- around 20,000 years ago, or much later, in the Zone III / Younger Dryas cold snap around 10,500 years ago?

New book causes much head-shaking....

The other day I had a very long conversation with Laura Geggel from Live Science in the USA, as a result of which she has now published a piece on the web:

https://www.livescience.com/62619-did-glaciers-carry-stonehenge-bluestones.html

Well, it's more carefully written than the piece in the Daily Mail!  As one might expect with science journalists, they get some things right and some things wrong, and then, having tried to present the views of the main protagonist (in this case, me) they have to balance it with the views of some outraged archaeologists.  So she has spoken to Josh Pollard (who is of course a leading proponent of Neolithic quarrying) and Barney Harris from UCL, who was involved in that lovely little stone-hauling experiment in a London Park, and they have given her all the reasons why glacial transport was impossible.

It will be a waste of time to get too involved in analysing everything that Pollard and Harris are reported as having said, but here are a few thoughts:

1. Pollard says that there are no moraines with big chunks of bluestone in them on Salisbury Plain.  I have never claimed that there are -- and indeed it would be vanishingly unlikely that depositional landforms with a strong surface expression could have survived half a million years of denudation.  Neither he nor I know whether there are patches of denuded or degraded till on Salisbury Plain, from which larger erratics (and maybe smaller ones too) have been collected.

2.  Pollard claims that there are artifacts including stone tools at Rhosyfelin and Carn Goedog which indicate that quarrying took place there.  Which stone tools?  Which artefacts?  He knows perfectly well that all of their "evidence" has been examined and disputed.

3. Are the bluestones pillar-like blocks, as Pollard claims? Some of them are, but the great majority are not. He says that smaller rounded boulders would be more likely to come from moraine, while pretending to be ignorant of the fact that most of the 43 bluestones are indeed smaller, rounded, faceted and heavily abraded.  In other words, they are typical glacial erratics.

4. Yes, dolerite is not very likely to preserve striations, but are rhyolites and sandstones more likely to hold striations if transported by ice? Maybe, but can somebody please show me a rhyolite or sandstone monolith at Stonehenge that does not carry striations?

5. "I would think [the rhyolite] would just disintegrate, to be honest, if it was in glacial deposits," said Josh.  Well, since there are no rhyolite monoliths at Stonehenge, maybe that is exactly what happened to them.

6.  "We know where the rocks started from, and we can see the extraction points?"  Excuse me, Josh -- but that is all fantasy.

7.  It's a bit disingenuous of Josh Pollard to claim that Newgrange and the Ring of Brodgar show evidence of long-distance stone transport. At Newgrange we are talking about small bits of quartz for the facing of the mound, and at Ring of Brodgar it is much more likely that the standing stones were for the most part glacial erratics.  The Vestra Fiold "Neolithic Quarry" has NOT been shown to have provided the stones used, as I have pointed out on this blog.

https://brian-mountainman.blogspot.co.uk/2014/01/ring-of-brodgar-and-its-quarry.html

8.  Barney's point is a valid one -- when he says that if there were bluestones on Salisbury Plain at the time of the earliest stone settings, why were they not used?   Well, maybe they were.  Kellaway and many others have suggested that long barrows were robbed of larger stones when stone settings became all the rage -- but I thought it was now assumed that before Stonehenge was built there was no great interest in using large stones?  In the Early Neolithic, if stones had littered the landscape, they might well have been ignored.

9.  Let's forget about the "experiment in the park".  It was very jolly, but did nothing whatsoever to enhance our ideas about what happened in the Neolithic.  

All in all, the argument of the archaeologists seems to be this:  "Neolithic people were very clever.  If they had wanted to transport lots of bluestones from Wales to Stonehenge, they would have done it.  Therefore they probably did it...."

Sorry chaps, but that's not science.  It's fantasy, or something akin to religious belief......

Seymour thesis on vegetation development in Holocene Preseli

I had not realised that this thesis from Philip Seymour had been digitised.  Anyway, it is a useful resource in that it describes environmental change since the last "cold snap", as recorded in the pollen record.  It's very tightly focussed, and I would have like to see a bit more awareness of the wider context; my sense is that there was a concentration at the time on working out what anthropogenic changes there were -- still a reaction, maybe, to the old ideas of environmental determinism......

Some of the sites examined were in the eastern Preseli area -- referred to by the author as the "Bluestone Area".  One interesting thing is the author's unswerving allegiance to the human transport thesis; he says there is so much evidence of human occupation and activity in the area around Foel Drygarn and Caen Meini that Kellaway's glacial transport thesis becomes "unnecessary" !!  Hmmm.... It was a long time ago, and we'll let that pass.

But a useful document nonetheless......

The environmental history of the preseli region of South-West Wales over the past 12,000 years

Seymour, W. Philip

URI: http://hdl.handle.net/2160/3307

Date: 1985

Citation:
Seymour, W. P. (1985) 'The environmental history of the preseli region of South-West Wales over the past 12,000 years', Institute of Geography and Earth Sciences, Aberystwyth University

Abstract:
The project involves a detailed palynological investigation into the environmental changes that took place during the Late-Devensian Lateglacial and Flandrian periods in the Preseli district of northern Pembrokeshire, south-west Wales. The approach adopted specifically takes into account the considerable diversity in terms of subenvironments and ecological habitats within the field area, with representative sites on the northern coastal plain, the exposed ridges of the Preseli Hills, sheltered valleys which dissect the uplands, and the flanking plateaux. In this manner and through definition of local pollen assemblages, unrepresentative extrapolations are minimised and an unbiased regional chronology has been produced. Results indicate that the distinctive climatic character of Pembrokeshire was probably manifest throughout the entire period under discussion. Thus, Corylus was locally present during the Late-Devensian Lateglacial Interstadial as it expanded from refugia to the south and west, and its extension very early during the Flandrian is also recognised. Conversely, Betula was relatively subdued during the Lateglacial and Early Flandrian, therefore suggesting that migration across the Cambrian uplands to the east was inhibited, particularly with the prolonged influences of the Loch Lomond (Younger Dryas) stadial on the high ground. The early establishment of mixed oak forest on the coastal plain is also recognised, although with some variation in its distribution within the field area. Apart from iiilocalised occurrences of carr woodland, however, the main Alnus rise did not occur until c. 6800 BP, when it is suggested that the rising sea-level may have been largely instrumental in creating suitable habitats on the littoral lowlands. During the later part of the period in particular, the variable activities of prehistoric populations are evident. Especially notable is the centre of activity during the Late Neolithic - Early Bronze Age near the site associated with the origins of the Stonehenge Bluestones. During the post-Roman period several cycles of increased exploitation and abandonment are recognised and these correlate well with historical evidence.

Blanket peat on Waun Mawn

Exposure in the side of one of the drainage channels on Waun Mawn, on a gentle south-facing slope.  Here we see about 30 cm of iron-stained / gleyed regolith made of broken meta-mudstone debris with signs of cryoturbation.  Above that there is a thin layer with streaks of organic material, and above that about 10 cm of "blanket peat" containing a network of roots from the present-day turf layer at the surface, which is only 5 cm thick.  This is quite typical of the moorland hereabouts.  There is no sign of Devensian till at this location.

I have been taking another look at the "progress report" written by Prof MPP for the Rust Family Foundation:

http://www.rfamfound1.org/proj23find.html

In the section on Waun Mawn some stress is placed on "the date of peat formation" as a guide to the age of the sockets and the speculations surrounding stone removal.

As far as the biggest recumbent stone in the putative "proto-Stonehenge" circle is concerned, MPP says this: Its former stone socket is lined with many packing stones, and the peat fills of this socket indicate that the stone fell after the onset of peat growth."

On the other hand, "The smaller recumbent stone excavated in 2017 is on the east end of the arc and is just under 1m long (fig.4). The fill of the stone socket contains only brown loam and no peat, indicating that it filled before the growth of peat. Thus this stone came down before peat growth."

Then again:  "Emptied stone sockets with stone packing (but no surviving monolith) were identified beyond both ends of the arc of monoliths. The socket on the west side was a circular pit (0.85 m- diameter and 0.3 m-deep) containing large packing stones set vertically. The emptied socket had filled with brown soil before any peat formation. Deformation of the edge of the pit showed that its former standing stone had been removed towards the north."
"We discovered two empty stone sockets on each end of the arc, suggesting that these stones may well be the remains of a dismantled stone circle (figs.5,6). Megaliths were removed from these sockets before the onset of peat growth on this site, indicating that the stone
circle was dismantled in the distant past."

Tying things up and seeking to demonstrate (even at this very early stage) that there WAS indeed a stone circle here, on the basis of very scanty evidence, MPP concludes:  "It can be assumed that the lack of peat in three of the stone sockets indicates that their standing stones were removed before the growth of blanket bog. This is likely to have started growing around 3,000 years ago, which would indicate that the stones came down in the Neolithic or earlier Bronze Age."

This is all seriously confusing.  MPP suggests that blanket peat formation here did not start until 3,000 years ago, which would place it in the Sub-Atlantic climate phase (pollen zone VIII), well after the elm decline and 3,000 years later that the date normally assumed for blanket peat development in the uplands of Wales.  In most of the texts and in Gallego-Sala et al (2015) it is suggested that in upland Wales blanket peat development probably started early -- maybe as early as 7,000 years ago --  during the Atlantic "climatic optimum" when it was warm and wet.  It's also suggested that around 3,000 years ago, at a time of lower rainfall totals, and an increase in ash and birch cover, blanket peat development might actually have slowed.  After 3,000 years ago, blanket peat initiation occurred only in a smallish number of "less favoured" locations. 

In the Preseli uplands, we can reasonably assume that blanket peat development will have started at the same time as in the other uplands of Wales where there were acid soils and high precipitation rates.

Nothing seems to fit.  So we have a problem........

Could it be that the things being called "stone sockets" are not stone sockets at all, but are simply surface depressions or irregularities that have nothing whatsoever to do with standing stones?

================

Gallego­-Sala, A. V., Charman, D. J., Harrison, S. P., Li, G. and Prentice, I. C. (2015) Climate­-driven expansion of blanket bogs in Britain during the Holocene. Climate of the Past Discussions, 11 (5). pp. 4811­-4832.

ISSN 1814­9359 

doi: https://doi.org/10.5194/cpd­11­4811­2015 

Available at http://centaur.reading.ac.uk/48736/

PS.  The only detailed work on the development of vegetation in the Preseli - North Pembrokeshire area is a thesis by Philip Seymour, completed in 1985.  It can be seen here:
http://cadair.aber.ac.uk/dspace/handle/2160/3307

It's essentially a pollen analysis study based on a variety of upland and lowland suites, recording changes in pollen frequencies in sediment sequences.  It makes the point that the development of blanket peat bogs was never very great in this area, partly because of the lack of extensive plateau surfaces where waterlogging could occur.  So drainage -- mostly on gentle slopes -- was generally sufficient to prevent blanket peat development.  This is borne out by the generally thin peat layers which we find across most of the landscape -- 10 cm is a rather typical thickness.  Did all of the peat start to develop at about the same time?  And was that time associated with the Neolithic / Bronze Age increase in land clearance associated with forest burning and increased grazing activity?  Seymour suggests that this was the case, and that peat development before the Neolithic was not very marked, especially on fairly well-drained slopes.  He takes a rather anthropogenic approach, suggesting that peat and soil development was very much influenced by settlement and land use practices.  But there is a danger of circular reasoning -- was the environment causing man to make certain land-use decisions, or were cultural decisions shaping the environment?  Walker and McCarroll (in the QRA Field Guide for West Wales, 2001) take a more nuanced approach, agreeing that periods of peat development are associated with periods of increased rainfall, leaching, iron pan creation and waterlogging  -- while admitting that there is such a wide range of dates for the "onset of peat development" in West Wales that land use practices and settlement pressure must have some role to play.

It will be interesting to see what turns up when Waun Mawn is examined in greater detail.....

The raised beach platform at Lydstep Point

Looking east

Looking west

This is probably the most spectacular raised beach platform in Pembrokeshire -- it's about 100m long,  and up to 25m wide, and is tucked into the little bay between Lydstep Point and Whitesheet Rock.   It cuts across near-vertical strata, and appears to have nothing to do with any faults or fractures in the Carboniferous Limestone.  It's difficult to photograph because it is so extensive -- but everywhere it has quite a gentle gradient down from a distinct notch cut into the cliff slope, and at its outer edge there is a sharp drop down into the sea.

The most fascinating thing about this platform is that it is incredibly chopped up -- criss-crossed with fissures and chasms and undermined by caves.  It is actually quite difficult to walk across it because of these surface irregularities.  This, to me, indicates very great age --  the chasms, pits and collapsed caves are all signs of marine processes currently destroying something formed a long tome ago, at a time when sea level was rather stable, around 15-20 m above its present level.  I think that this raised beach platform is at a higher level than that of Broad Haven -- which is also cut into a limestone coast.

In spite of a thorough search, I found no traces of a raised beach here (cemented or loose) and no trace of any till.  But there is an area of about 10m x 10m where cemented limestone breccia rests on the platform and has survived subsequent erosion -- storm waves certainly get onto this platform when there is a southerly gale combined with a high tide.

Here the breccia is about 1m thick, and about 2m  thick in a few places -- and it has to be related to the limestone breccia on the neck of the small peninsula just 450m to the west.  The other interesting feature of the platform is the presence of a number of widened fissures and "slit caves" cut into the face of the old cliffline at the bach edge of the platform.  These are perfect locations in which animal remains and maybe other organic materials might be found.  These would be invaluable in working out the chronology of this site.

My instinct is that there might be raised beach cobbles -- and maybe ancient till -- beneath the cemented limestone breccia, waiting to be discovered.  The rock platform itself may even predate the Anglian glacial episode -- but it could of course be a composite feature, freshened up during several interglacial high stillstands of the sea.

Hut circle on Waun Mawn

The hut circle on Waun Mawn -- some stones visible, and others buried in the turf.  Too small to be a stone circle, and too big to be the remains of a cromlech, I suspect......

I went over to Waun Mawn to see if I could find the little hut circle shown on some of the old maps.  I found it all right --- it's very small indeed, less than 5m across, so if it was a hut it must have been very cosy.......

It's located about 200m from the single standing stone to the north of the Gernos Fach track.  Go directly upslope from the standing stone, and you'll see the small grassy mounds and the stones towards the eastern edge of a grassy area surrounded by low gorse bushes.

The single standing stone on Waun Mawr, on the north side of the farm track

Lydstep ancient till site confirmed

National Trust map of Lydstep headland, showing key Pleistocene sites

Further to my earlier note about the suggested ancient till at Lydstep, I have been back there today to check it out -- and it is very impressive indeed.

https://brian-mountainman.blogspot.co.uk/search?q=+Lydstep

https://brian-mountainman.blogspot.co.uk/2014/03/classic-pembrokeshire-pleistocene.html

The first record of an ancient till at this site is from Arthur Leach, in his papers and manuscripts held in Tenby Museum:

The full grid reference for the ancient till site is SS 08802 97473.

I also visited the site and published a brief record of it in 1974.  The key location is a little peninsula that extends southwards from the "heel" of the big peninsula.  Here, by a freak of nature, a vast expanse of cemented limestone breccia has been protected from extensive marine erosion.  An area of at least 30m x 20m supports a most unusual -- and slightly surreal- -- landscape of concreted ridges and hummocks of limestone debris (mostly sharp-edged fragments which are partly frost-shattered and partly natural scree slope accumulations) on an undulating rock platform about 20m above sea-level.  I agree with Leach that this is not a wave-cut platform -- it is too high, and it does not have a wave-cut notch against an old cliffline.  I have struggled a bit to work out where on earth all this shattered scree has come from, and  have come to the view that it cannot all have come from the cliff slope to the north.  I think this is the floor of an old karst dry valley like the one that runs northwards from the western edge of Lydstep Headland today.  The southern side of this valley has, I think, been completely lost to marine erosion.  This is an indication of the great age of the breccia and everything that lies beneath it.

Cemented limestone breccia about 2m thick on the little peninsula at Lydstep, with the karst coast beyond (looking west)

Cemented limestone breccia about 3 m thick, at the foot of the northern valley slope.  There is no till exposure at this location.

Cemented limestone breccia sheet about 2m thick, resting on broken limestone bedrock.  To the left of centre is a chasm that falls straight down to the sea below.  

Looking straight down through another gaping hole in the sheet of limestone breccia.  The breccia now forms the roof of a gigantic cave, and eventually it will all collapse into  the sea........

At the eastern edge of the breccia exposures, there is a spectacular overhang or projection of the breccia sheet, sticking out eastwards by about 2m -- and beneath is is the classic exposure of ancient till.  The grid ref is approx SN 088975.  

The spectacular overhang beneath which the ancient till deposit has been protected.

The till exposure is about 10m long, and the till is about 1 m thick.  It is solidly cemented, like the breccia above it.  It rests directly on an undulating bedrock surface that has the appearance of ice moulding -- but no striations could be seen because of heavy manganese oxide staining. 

Cemented till (here containing mostly broken limestone fragments) resting directly on a stained bedrock surface

Approx 1 m of cemented till exposed beneath the overhang.

Large erratic block and smaller cobbles in a sandy till matrix, beneath the overhang.

Erratics in the cemented till, including ORS, buff sandstones, mudstone and shale fragments, as well as many local limestone fragments.

Here and there above the till is a cemented deposit of sandrock or sandy loam, foxy red in colour and full of interesting holes.  Animal burrows, or root holes, created when the sediment was fresh and soft?

I have a full record of the site, and the Pleistocene sequence seems to be:

4.  Up to 3m of cemented limestone breccia, in places blocky from catastrophic rockfalls, and in places full of smaller (frost-shattered?) fragments.  No clear stratification.

3.  Cemented sandrock containing some till and limestone fragments -- up to 20 cms thick.

2.  Cemented ancient till up to 1 m thick, containing abundant foreign erratics.

1.  Bedrock floor of old valley, apparently smoothed beneath glacial deposits.

There are no raised beach deposits here, and no fluvioglacial deposits either.  The best guess must be that the till dates from the Anglian glaciation, that the brickearth represents a climatic amelioration (interglacial?), and that the thick cap of limestone breccia has accumulated during the whole span of the Devensian glacial episode.  There is no fresh Devensian till here, but it is found a short distance away (about 200m) at the head of the creek leading into the dry valley.

As far as I am aware, this is the most extensive and most accessible ancient till deposit in Wales.

In some texts the site is recorded as follows: The rough looking headland "Black Mixen"  is covered with angular Limestone Fragments , cemented together - a Gash Breccia rock type , formed possibly by a Debris slide in the Triassic period ( 200 - 250 million years ago ) , when a Wadi was infilled.  This is way off the mark.  There is no reason to think this is a gash breccia --although gash breccias are common in the area in fissures, associated with fault movement and with reddish staining.  I like the idea that the dip between the outer peninsula and the main slope of the headland might be all that is left of an old valley floor -- but the fact that there is till beneath the breccia means that it cannot possibly be Triassic, and it cannot possibly have anything to do with a warm and arid climate.

PS.  (added 31st August 2018)    This little peninsula is referred to in the Pembroke and Tenby Geological Memoir (1921) as "Black Mixen" (p 192).   I am not sure whether Dixon or any of the other surveyors actually visited this site -- but they refer to the platform as a part of the raised beach platform (I agree with Leach that it is too high for that) and while they mention the great expanse of cemented limestone head, they make no mention at all of the underlying cemented ancient till.  Strangely, they do mention a deposit of current-bedded sand and gravel in a fault fissure at the back of the cave then runs under the neck of the peninsula "at about the height of the raised beach."  They speculate that this might be glacial........  it needs to be investigated.

Devensian till at Lydstep

While out on o bookselling trip today I was inspired by the gorgeous summer weather to take a small diversion to Lydstep, where I wanted to check out an old record of mine regarding an ancient till deposit.  More of that in another post.

What I also discovered, on descending to the beach (which you can only do at low tide), was a splendid exposure of fresh till which has to be Devensian.  It's located in the stream gully where one has to scramble down from the grassy floor of the dry valley to the boulder-strewn beach.  The grid reference is SN 087976.

The exposure reveals at least 2m of fresh till, with a sandy and gravelly matrix and a wide assortment of striated, faceted and worn cobbles and smaller stones of many different lithologies -- including ORS, grey and buff sandstones and quartzites, blackish mudstones, shales, flints and quartz pebbles.   There's very little rounded material, suggesting that no raised beach or Pliocene pebble beds have been incorporated here.

The till is exposed almost up to the ground surface, and is capped only by the thin soil layer.  There is a lot of slumping on the exposure, but the till appears to be  underlain by a foxy red clay-rich deposit (at least 1 m thick) that appears to be relatively stone-free.  I could not determine whether this was a basal clay-rich till layer or a locally-derived gash breccia such as we see in many fissures along the limestone coast.

Anyway, this is one of the most coherent and easily accessible fresh till exposures on the South Pembrokeshire coast,  and there can be little doubt about its age, since it is completely uncemented (in an environment dominated by calcium carbonate) and has no scree or slope deposits on top of it.  It has to be Late Devensian in age.

As a matter of interest, this boulder rests on the beach just a few metres away, in a jumble of other large boulders.  It looks to me like gabbro -- similar to the gabbro that outcrops near St David's Head.  But that's just an educated guess......

Heavily abraded boulder of gabbro (?) not far from the till exposure at Lydstep.  It's one of the largest erratics seen thus far along the south Pembrokeshire coast.

As a matter of interest, the other posts describing Devensian till on the South Pembrokeshire coast are here:

https://brian-mountainman.blogspot.co.uk/2018/04/even-more-south-pembrokeshire-till.html

https://brian-mountainman.blogspot.co.uk/2011/08/glaciation-of-south-pembrokeshire.html

https://brian-mountainman.blogspot.co.uk/2018/04/strange-till-near-stackpole-head.html

https://brian-mountainman.blogspot.co.uk/2018/04/the-devensian-ice-limit-in.html

https://brian-mountainman.blogspot.co.uk/2011/08/glaciation-of-caldey.html

https://brian-mountainman.blogspot.co.uk/2018/04/erratic-boulders-on-south-pembrokeshire.html

Glaciation of the Bristol - Gloucester region

This is an interesting summary from the Earthwise (BGS) web site.  Found here:

http://earthwise.bgs.ac.uk/index.php/Glacial_deposits,_Quaternary,_Bristol_and_Gloucester_region

It's bang up-to-date, having been revised in January 2018.  As the authors say:  "Evidence in Somerset and Avon, combined with that from South Wales, for an Anglian glacier moving up the Bristol Channel has been accumulating in the last decade or so."

Show this to anybody who suggests that ice never flows eastwards, or that the Irish Sea Glacier never crossed the Bristol Channel and penetrated far into Somerset.........

There is no assessment here of the likely easternmost limit of the Anglian ice.

----------------------------------------

Glacial deposits, Quaternary, Bristol and Gloucester region


based on Green, G W. 1992. British regional geology: Bristol and Gloucester region (Third edition). (London: HMSO for the British Geological Survey.)

Glacial deposits

The glacial deposits of the region are mostly scattered remnants and provide difficult problems of interpretation. The earliest drift deposits are represented by remanié patches of erratic pebbles of quartz, ‘Bunter’ quartzite and, less abundant, strongly patinated flint lying on the surface of or within fissures in the Cotswold plateau up to a height of 300 m above OD. On the eastern boundary of the present region and in adjacent areas to the east, there are scattered patches of sandy and clayey drift with similar erratics, which are now known collectively as the ‘Northern Drift’. The general opinion is that the deposits are heavily decalcified and probably include both tills and the fluviatile deposits derived from them. They predate organic Cromerian deposits in the Oxford area and thus provide evidence for pre-Cromerian glaciation (see summary in Bowen et al., 1986)[1].

High-level plateau deposits in the Bath-Bristol area comprise poorly sorted, loamy gravels with abundant Cretaceous flints and cherts and have been correlated with the ‘Northern Drift’.

The Anglian glaciation is better represented in the district. In the Vale of Moreton there is a three-fold sequence. At the base lies the Stretton Sand, a fluviatile, cross-bedded quartz sand, which has yielded a temperate fauna including straight-tusked elephant and red deer. This was formerly dated as Hoxnian in age but now must be considered to be older. The Stretton Sand is similar to the supposedly younger Campden Tunnel Drift (see below), and it has been suggested that the temperate fauna in it is derived from an earlier interglacial deposit. The overlying Paxford Gravel, which comprises local Jurassic limestone material, has yielded mammoth remains and has an irregular erosive contact with the Stretton Sand. At the top, up to several metres of ‘Chalky Boulder Clay’ with derived ‘Bunter’ pebbles may be present. Thin red clay is locally present immediately beneath the till, possibly representing a feather-edge remnant of the glacial lake deposits of Lake Harrison.

At the northern end of the Cotswolds, in the gap between Ebrington Hill and Dovers Hill, the Campden Tunnel Drift consists of well-bedded sand and gravel with ‘Bunter’ pebbles and Welsh igneous rocks, and two beds of red clay with boulders, probably a till. The deposits occupy a glacial overflow channel, up to 23 m deep, caused by the ponding of the Avon and Severn valleys by the Welsh glacier farther downstream.

Evidence in Somerset and Avon, combined with that from South Wales, for an Anglian glacier moving up the Bristol Channel has been accumulating in the last decade or so. The construction of the M5 motorway through the Court Hill Col on the Clevedon–Failand ridge led to the discovery in the bottom of the col of a buried channel, 25 m deep and filled with glacial outwash deposits and till. Drilling has since proved similar drift-filled channels in the Swiss and Tickenham valleys crossing the same ridge. South of the ridge, and rising from beneath the Flandrian alluvium of Kenn Moor, marine, brackish and freshwater interglacial sand and silt overlying red stony and gravelly till and poorly sorted cobbly outwash material were disclosed in drainage trenches and other works. AAR results indicate that whilst the bulk of the interglacial deposits are Ipswichian in age, samples of Corbicula fluminalis from fluvial deposits directly overlying the glacial deposits give a much earlier date and suggest that the latter are Anglian in age (Andrews et al., 1984[2]). Similar local occurrences of possible till have been reported beneath the Burtle Beds of the Somerset levels. In the light of these and other discoveries, the glacial overflow hypothesis of Harmer (1907)[3] for the cutting of the Bristol Avon and Trym gorges has been revived to explain why these rivers cut through hard rock barriers in apparent preference to easier ways through adjacent soft rocks.


References


Bowen, D Q, Rose, J, McCabe, A M, and Sutherland, D G. 1986. Correlation of Quaternary Glaciations in England, Ireland, Scotland and Wales. Quaternary Science Reviews, Vol. 5, 299–340.
Andrews, J T, Gilbertson, D D, and Hawkins, A B. 1984. The Pleistocene succession of the Severn Estuary: a revised model based upon amino acid racemization studies. Journal of the Geological Society of London, Vol. 141, 967–974.
Harmer, F W. 1907. On the origin of certain canon-like valleys associated with lake-like areas of depression. Quarterly Journal of the Geological Society of London, Vol. 63, 470–514.

This page was last modified on 30 January 2018

Biological processes at Rhosyfelin

I'm increasingly convinced that biological processes are -- and have been for a long time -- of great importance in the evolution of the landforms at Rhosyfelin.

If one looks back at the Devensian, and at the history of other crags and rock faces (for example, on the coast) one sees the effects of frost shattering over a period of around 70,000 years -- during which there must have been continuous or discontinuous permafrost and an ongoing process of rock breakage at the surface.  Many fracture patterns must have been exploited, with fractures opened or widened by freeze-thaw processes.  Then, in the intervals when scrub or woodland vegetation was able to take hold, the expansion of root systems must have continued the work, forcing fractures to widen even further, until failures occurred, accompanied by large and small rock fragments crashing down and accumulating on the flank of the crag.  This is what we see in all the photos -- interpreted as quarrying waste by the archaeologists and as natural rockfall or slope accumulations by geomorphologists.  

The process continues to this day -- maybe at a faster rate now than in the past, given the nature of the present climate and the occupation of the upper part of the crag by  gorse, hazel, willow and other bushes and small trees.  Root expansion does part of the work, the the rocking of trees and shrubs in the wind is another very active process.  I'm planning more work on this -- watch this space.........

Ramsey Island

This is a fabulous false-colour laser image of Ramsey Island, showing  what incredible detail can now be picked up on the land surface with modern technology.    This was created as part of a survey of archaeological features, but topographical features are also fascinating -- the two hill masses are heavily ice-moulded, and during the Devensian (and earlier glaciations) the island took the brunt of the weight of the Irish Sea Glacier as it came in from the NW.

We have already wondered, on this blog, about the link between the giant erratics at Broad Haven and the island of Ramsey, and we have strong suspicions that at least some of the material on Flat Holm has come from here too.

The northern hill mass is made of microtonalite, and the southern one has a varied geology, with rhyolitic pyroclastic rocks, some sandstones and conglomerates, and in the south, other rhyolites in a complex relationship with Ordovician sedimentary rocks.

The old and the new at Stonehenge

Somebody posted this on another Stonehenge blog site, showing what good company I keep in the Stonehenge Visitor Centre.  A batch of the new book is winging its way to Stonehenge as I speak -- so I suppose that for a little while (until old stocks are sold out) the visitors will be able to buy the cheaper old book alongside the more expensive and more up-to-date new one.   You get what you pay for in this world.........

By the way, all credit to EH for selling my books, which might be considered by some to be subversive if not downright disruptive!  Maybe the archaeologists do not speak to the shop staff, who may be rather more concerned with running their operation at a profit than with toeing the party line on interpretations.

Anonymous posts will be treated as spam

Please note:  I still get up to 20 anonymous posts every day, most of which are nonsense posts which are correctly identified  as spam, sent by people to random Blogger sites when they have nothing better to do.  Every now and then, I notice in the trash can that there is something that is relevant to a discussion -- but it will still get filtered out and treated as spam because of the preference settings on the site.  Normally I do not even get to see these messages -- they are dumped straight away.  So if you have anything to say, please use your correct identity when you submit a comment, or at the very least, use a pseudonym which can act as your "handle".  That way, your voice might be heard......