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Friday, 30 September 2011

Alice in the rain



So there we are then.  Geoff and Tim have been digging for Britain, in the pouring rain, in that old Neolithic tomb on the slope beneath Carn Meini.  One has to admire their fortitude, and I hope they didn't catch their death of cold in all that horrible weather........

What Alice Roberts (or her producer) did was to turn this into a Stonehenge story, whereas the burial mound and whatever might lie beneath it has nothing whatsoever to do with Stonehenge.  But so solidly embedded is the myth of the bluestone quarry at Carnmeini, and the idea that there are sacred springs in the area, and that somehow anything elongated means that it must have been headed for Stonehenge, that all we got was a rather feeble non-story.  The "twin standing stones" were so small that I could have used them to prize off a muddy pair of wellington boots -- how on earth they were supposed to provide a link with Stonehenge, only Prof GW will ever understand.  I think that the BBC might have edited out the bit about the tomb possibly being the place where the architect of Stonehenge was buried........  so maybe they are starting to get a wee bit embarrassed by all this nonsense?

This is from the BBC web site:
http://www.bbc.co.uk/news/uk-14733535

Prof Wainwright said: "The important thing is that we have a ceremonial monument here that is earlier than the passage grave.
"We have obviously got a very important person who may have been responsible for the impetus for these stones to be transported.
"It can be compared directly with the first Stonehenge, so for the first time we have a direct link between Carn Menyn - where the bluestones came from - and Stonehenge, in the form of this ceremonial monument."

That last sentence (about a "direct link") is supported by no evidence whatsoever  -- how come that Prof GW is allowed to get away with this sort of stuff in an interview, and how come the BBC is prepared to paste it up on its web sites?   So a message for Alice -- next time you talk to these eminent gentlemen, try at least to question some of their assumptions, and PLEASE ask them what they have in the way of evidence to support their fantastical stories.

The Angian ice margin



My thanks to Lionel Jackson for bringing this to my attention.  In a chapter on Pleistocene Glacial Limits in Great Britain, Phil Gibbard and Chris Clark assemble as much information as possible from published sources to suggest where the glacial limits of the last three British glaciations might be drawn.  The map is somewhat crude and generalised, and in detail it is demonstrably wrong.  For example, the glacial limit of the Devensian in Pembrokeshire is demonstrably incorrect, since Devensian till is found at a number of locations (including Caldey Island) well outside the line as they have drawn it.  Also, the Anglian limit is wrong in Somerset, since glacial deposits are found at least as far to the east as Bathampton, to the east of Bath.

However, this does represent progress, and it will be nice if somebody could bring this map (and the quote below) to the attention of Professors GW, TD and MPP, since they seem to be quite determined to pay no attention at all to anything I might say!


"............At the same time, this (Anglian) glaciation extended across the Bristol Channel as far as the northern coast of the English South-West Peninsula (Bowen et al., 19 8 6 ), although there is some dispute over precisely how far it reached. There seems to be doubt whether it reached Cornwall or the Scilly Isles, where deposits previously thought to be Anglian are now assigned to the Devensian (Campbell et al., 19 9 9 ). If the ice did indeed cross the Bristol Channel during this phase, it would have blocked the River Severn drainage potentially causing a proglacial lake to form in the valley."

Pleistocene Glaciation Limits in Great Britain
Philip L. Gibbard, and Chris D. Clark
Developments in Quaternary Science. Vol.15.

A few centuries of glacial action....


This image, from one of the modelling experiments reported, shows the percentage of time that the ice was present at any particular point. Note that the ice was present for a very short time indeed (centuries, not millennia) when it affected SW England.

Another look at the Hubbard et al paper from 2009. The authors of that article were reporting on the computer modelling experiments which gave a good indication of the behaviour of the British and Irish Ice Sheet during the Devensian (most recent) glacial episode.They argue that according to the best models available, feeding all all relevant climate and glaciological data, and incorporating ground evidence too, they see the ice sheet extending across parts of SW England as recently as 20,000 years ago -- maybe for no longer than a few centuries. That is a very short-lived incursion. Not many people accept that, arguing that the evidence on the ground just does not support such an incursion as far east as Salisbury Plain. I have my doubts too -- but I prefer to think of this as a model that might also have applied in the Anglian Glaciation, with a wet-based ice sheet advancing very rapidly eastwards, incorporating the small detached icefields over the uplands of Dartmoor, Exmoor etc before reaching its position of maximum extend -- and before melting away very rapidly.

Interestingly, they argue that it was a slight WARMING of the climate that caused this apparent surge behaviour, since increased water at the glacier bed would have led to accelerated forward movement.


"Another phase of warming at 20.8ka prompts a widespread mobilisation of wet-bedded ice across extensive lowland and shallow marine sectors yielding maximal ice cover across the domain at 20.1–19.9ka. Large, mobile, surge lobes dominate the southern sectors of the Irish Sea and North Sea, and the Atlantic coast and extend to the north coast of SW England, Norfolk and to the continental shelf edge, respectively." (p 767)

"The experiments presented also indicate significant excursions of wet-based ice into areas of southern England, where little evidence of recent glaciation has been found, This may not present such a major problem given that our model indicates ice was at this extended limit for less than 1 ka. The experiments also provide support for a possible glacial mechanism for the movement of Preseli erratics as a transport trajectory which overrides parts of northern Pembrokeshire and was subsequently deflected south-eastwards across the Bristol Channel into SW England, cannot be completely discounted."

'Dynamic cycles, ice streams and their impact on the extent, chronology and deglaciation of the British–Irish ice sheet.'
Alun Hubbard, Tom Bradwell, Nicholas Golledge, Adrian Hall, Henry Patton, David Sugden, Rhys Cooper, Martyn Stoker
Quaternary Science Reviews 28 (2009) 759–777

Look at the last sentence in that quotation.  That is interesting, coming from a group of glacial geomorphologists and glaciologists.  You will recall that  James Scourse and Christopher Green HAVE completely discounted the idea of glacial transport of the bluestones, and have even (ill-advisedly, in my view) used the word "impossible." 

The Boles Barrow Bluestone


Somebody sent me this picture -- I think it is the Boles barrow bluestone up against the wall on the left hand side. Can anybody confirm that? I have not seen it in person, and a friend who once went to the Salisbury Museum and tried to take a picture of it was told to put his camera away! (Is the stone covered by the Official Secrets Act?)

I got this comment the other day from somebody who knows the stone: "Boles/Bowls Barrow: - the Heytesbury stone I'd call a truncated pillar - parallel sided, rear face plane, unweathered, where plucked from outcrop, front has rounded off edges, looked deeply weathered to me, thought I could see the odd shallow thermal (?) pit. Couldn't see any signs of working. How old is the truncation? Not recent. I must dig out my large scale drawing and notes. Obviously if the truncation is really old it becomes absurd to think that anyone would select it to transport, but then the bluestone saga is an act in the theatre of the absurd."

That's an interesting point. This is a boulder, not a pillar or standing stone. If it was a pillar at some stage, probably two thirds of it are missing. Where is the rest of it? As Aubrey Burl and others have argued, it just looks like an erratic boulder -- nothing more complicated than that.

Wednesday, 28 September 2011

Scott, Mallory and Stonehenge



In some earlier posts I have discussed the "mood of the times" of the years immediately following the First World War, during which HH Thomas proposed his theory of the human transport of the Stonehenge bluestones -- without anybody subjecting the theory to rigorous scrutiny. When one considers the reasons for this apparent reluctance, among the earth science community of the day, to press Thomas on his evidence and to examine his assumptions (several of which were fundamentally flawed) one has to conclude that there was a sort of national contract to sign up for anything that made the nation feel good about itself.

I have come back to this because of new books on Scott of the Antarctic and George Mallory, who died on Everest in 1924. Reviews of these books make constant reference to the British "heroic myth" and the idea that all obstacles could be overcome through "sheer force of Britishness." We may find this slightly ludicrous nowadays, but we have to remember that the years before, during and after the First World War of 1914-1918 were very strange, involving not only idiotic politics and incompetent leadership, but also self-sacrifice and heroism on a gigantic scale. This was the period in which Scott and his companions died on their return from the South Pole; during which Shackleton became a national hero after extricating every single member of his "Endurance" expedition in which -- according to all the rules -- they all should have perished.

A couple of reviewers of the new books have both remarked on the special penchant of the British for becoming totally absorbed in tasks of "heroic futility." At the time when HH Thomas presented his famous lecture about the bluestones (in 1921) another great exercise in heroic futility was being planned. The Mount Everest Committee had just been formed -- with the specific objective of getting a British citizen onto the top of Mount Everest before anybody else managed to do it. We were jolly well not going to allow another unfortunate episode to occur, such as that in which Amundsen beat Scott to the South Pole......... So massive diplomatic and financial resources were thrown into the Everest Project, and in 1921 Mallory was involved in the British Reconnaissance Expedition, tasked with finding the best route up the mountain.

Thomas, as a member of the London scientific elite, must have known about the expedition; and he probably knew at least some of the members of the Mount Everest Committee. He was after all Secretary of the Geological Society of London at the time.

 Herbert Thomas, the man who was largely responsible for the promotion of the famous "human transport" theory

So in an atmosphere of nationalist fervour and a growing feeling that "we won the war; we can do anything" conditions were just perfect for the amiable reception of Thomas's theory, when he made his lecture to the Society of Antiquaries in 1921. His lecture matched perfectly the mood of the time, and indeed those who sat in his audience and suppressed any instincts they might have had to ask any serious questions may themselves have been greatly taken with the thought that our Neolithic ancestors were just as clever at undertaking "acts of heroic futility" as those of their own generation who become obsessed with reaching the South Pole or the top of Mount Everest.

Mallory died on Everest in 1924, the year after Thomas's paper was published. Again, that death became a national news story, once again confirming a sort of "mystic patriotism" which led men to their deaths in pursuit of heroic objectives. In that sort of environment of national jingoism and pride, who was seriously going to question the ability of our heroic Neolithic ancestors to shift 82 puny little bluestones from there to here?

Tuesday, 27 September 2011

Stonehenge Unhinged

For those who have started following my blog recently, and who may not have seen this...........

Now that some archaeologists are beginning to accept that Stonehenge's "empty quarter" was never built on, that the ancient monument was never finished, and that the same stones were used over and again in various settings by people who could apparently not make up their minds what they wanted,  here is a reminder of my little YouTube video.  It was deemed very subversive a couple of years ago, but now it seems mild and almost run-of-the-mill.  I wonder how long it will be before this becomes the accepted wisdom?


Castell Mawr -- Neolithic, Iron Age, or both?

Found this superb high-quality image of Castell Mawr -- the site now being mooted by MPP and colleagues as the HQ of the Neolithic tribe responsible for all that quarrying and transporting.......  they think there are signs of Neolithic influence in the arrangement of banks and ditches, and the entrances too.  Maybe they see a "causewayed enclosure" here?  Anyway, I suppose they may do some work here next summer.

Click to enlarge the image.

More on the Rhosyfelin outcrops

With reference to the recent dig at Craig Rhosyfelin, conducted by MPP and his team,  where did that big slab of rhyolite actually come from?  All will be revealed in due course by the geologists, but in looking back at my photos I am struck by the fact that there are teetering pinnacles and precarious slabs all over the place on this rocky spur.  Just look at these pics:

Slabs like the one discovered in the hole are probably littered around all over the place, around all of the flanks of the spur, incorporated to a greater or lesser degree into scree and rockfall debris.    The top photo above was taken on the "back" side of the spur (ie the south side)  -- note that the rock slabs are almost overhanging here, because there is a steep dip of the rock layers towards the NW.  You can see that reasonably clearly on the bottom photo, and ever more clearly here, on the photo taken by Dylan Moore:

Dylan's photo was taken from a bit higher up, in the little channel that runs up towards the bend in the road -- and indeed past it, towards the SW.  This little channel is a couple of hundred metres long, and I would guess that the big slab could have slipped down from the overlooking crags almost anywhere along its length, and might even have slid down a snowslope before ending up in its present position.

As far as the nature (or precise "fabric" and "provenance") of the rock is concerned, note that the strike of the rhyolite slabs runs straight out across the valley here -- on the alignment shown on my previous post. 


If you take the second black line from the top, one might expect to find fairly consistent fabric along that line, because the rhyolites as they cooled might have all experienced the same conditions.  In the same way, the fabric along lines 1, 3 and 4 might have experienced consistent conditions too, but different from those along line 2 to a greater or lesser degree.  The only thing that might screw up this situation would be later metamorphism in which heat and pressure came from a quite different direction that had nothing to do with the strike of the rocks.  Complicated?  Quite possibly......

But I still think we need to know what the rocks are like on the other side of the valley, in the top right corner of the photo.  Straight question to the geologists:  Have you guys sampled the rocks on that side of the valley?  And if so, what have you found?

Erratics and deposits in the Vale of Glamorgan

 Source:  Bevins and Donnelly 1992

The lowland Vale of Glamorgan -- the southernmost part of Wales -- is rather like South Pembrokeshire in that it does not have widespread deposits of till, either from the Irish Sea Glacier or from the glaciers which came down, several times, from the valleys of the South Wales Coalfield.  Indeed, some authors have suggested that there are so few traces of glaciation that the Vale was unglaciated.  But there are SOME glacial deposits, and SOME erratics, and geomorphologists do now accept that at least once the Irish Sea Glacier flowed across this area, travelling from west to east.  One of the key indicators is an erratic of pyroxenic keratophyre from the New Inn (north of Haverfordwest) found at Cardiff.  Other erratics have been found from Scotland and North Wales.  Heavy minerals in the lower soil horizons, shell fragments in the till, and "Irish Sea pebbles" from Cardigan Bay and west Wales also show that the ice came from the west and extended some way to the east of Cardiff.  This of course matches up with the evidence that ice crossed the Bristol Channel and extended eastwards as far as Bathampton near Bath -- and maybe even further.

The Storrie Collection

At Pencoed, near Bridgend, there are thick deposits of clay, sands and gravels and coarser deposits containing erratics.  Some of the clays -- at Ewenny and elsewhere -- have been used in the local pottery industry. The deposits are spread across an area at least 10 km x 10 km.  There are lake deposits and tills here -- and it's been known for more than a century that the erratic suite sampled by John Storrie contained at least eight different types of rock traced back to outcrops in west Pembrokeshire (Strahan and Cantrill, 1904).  Some of the erratics appear to be in their "original" positions -- others appear to have come from the reworking of older glacial deposits.  In a detailed reexamination of the erratic boulders from the Storrie Collection, Bevins and Donnelly (1992) described more than 20 which had come from the west, including ash flow tuff (Fishguard Volcanics?), basalt from the Skomer Volcanics,  rhyolite, Precambrian rhyolitic tuff, gabbro from near St David's Head, ignimbrite from Skomer, volcanic debris flow deposit from Ramsey Island, various sandstones and siltstones from South and West Wales, Carboniferous Limestone, ORS sandstones etc.  No less than 8 of the examined clasts had striations on them, confirming a glacial origin.

The interesting thing about this work by Bevins and Donnelly is that it shows a considerable mixing of erratics from the west and erratics from the north, which have come down from the valleys of the South Wales Coalfield.  (This is important when we consider how the Altar Stone, thought to have come from the Senni Beds, might have found its way into a suite of erratics being transported by the Irish Sea Glacier.)

Even more interesting is the incorporation of erratic material from the Lake District or Snowdonia.  And even more interesting still is the apparent exclusion -- in this area at the edge of the Vale of Glamorgan) -- of erratics from the eastern end of the Preseli upland ridge.  The Pembrokeshire erratics here are all from western Pembrokeshire -- and this means that if we reconstruct a simple ice flow pattern, it comes out as suggested in a 1965 paper by CB Crampton:


In fact, since there are erratics in the collection which have apparently come from Skomer and Ramsey Islands, we could push the arrow ever further towards the west in Pembrokeshire.

So if this ice stream was entraining erratics from the eastern end of Mynydd Preseli at the same time, where are the spotted dolerite and rhyolite erratics which we all know and love?   Was this part of the ice stream somehow "blocked off" by ice coming down from the uplands of Mid and South Wales?

I think the answer to this apparent dilemma is that there must have been many different episodes of erratic entrainment and ice flow in the West Wales - South Wales arena.  This is what is coming out of the recent work on the Devensian British and Irish Ice Sheet -- asynchronous behaviour around the fringes, with one part advancing while another part is retreating, and with swings in ice movement directions too.  As I have said before, individual erratics -- or even assemblages of erratics -- may well have followed zig-zag courses, over very long periods of time. 

I'm sure that in this area of conflict between ice from the west and ice from the north, we are only just beginning to unravel the history of what happened maybe 450,000 years ago, given that most of the evidence has been obliterated by what happened in the Devensian......

Monday, 26 September 2011

Now for some media management....


Next Friday our posh friend Alice will be on the telly, Digging for Britain near Carn Meini, in the company of two rugged fellows, namely Profs GW and TD.  We have seen the Youtube clip -- now for the real thing!

What's the betting that the programme will be accompanied by a flurry of press releases from the BBC and the two professors?  I look forward to that with fear and trepidation.....

What's the betting, too, that there may well be a preemptive strike by the MPP tribe, who will not want to be upstaged, just when they have all been having such fun in that deep hole at Craig Rhosyfelin?  So watch out for some press releases from that quarter too.......

Outcrops and sampling

Excuse the rather crude lines drawn on this map, but you get the message!  The grain of the country here, around Craig Rhosyfelin, is roughly SW-NE.  I think that somewhere on the blog an unnamed geologist said that much of the rhyolite debitage at Stonehenge could be fixed to within an accuracy of 2m -- to the NE tip of that rocky ridge of Craig Rhosyfelin.  That assumes that the very special rhyolite texture identified isn't found anywhere else.  I did ask whether the density of sampling points in the neighbourhood allows a statement like that to be made with any degree of certainty.

So here is my question to any geologists who might read this:  are you sure that rocks with precisely these special characteristics are not also found on the other side of the valley?  -- in other words -- in the top right-hand corner of this photo?  And might they also be found in other areas to the SW, ie off the bottom left edge of the photo?

Can we please see a geological map of the area?  This isn't just an awkward question -- this is fundamental for an understanding of the mechanics of glacial entrainment.

Saturday, 24 September 2011

Now the botanists get in on the act...


In May Julie made one of the finds of the year when she discovered a new inland colony of Pale Dog-violet (Viola lactea) in the north of the county at Craig Rhosyfelin, Crosswell on a steep south-east facing slope of gorse and heather at SN116360. There were about a 100 plants present in the heath, which was regularly burnt and grazed by ponies.

Actually this report is a few years old, but it certainly looks like a very pretty violet!

The morning after the night before....

A nice pic from Dylan Moore (acknowledged with thanks) of what the dig site looked like after the departure of the diggers:


Was this an "interim" tidying up job?  I hope they didn't all go off back to England, leaving all this mess behind them........

The dig site

In case anybody wondered, the MPP dig site at Craig Rhosyfelin is located where the circle has been placed on the photo -- just to the right of the tight bend in the road, and on the northern flank of the rhyolite ridge.

Click to enlarge -- this is quite a spectacular image!

From top to bottom of this photo the distance is about 500m -- note that there are many rhyolite outcrops.  Some of these have been sampled by Richard Bevins, and he and Rob Ixer are working to complete an accurate "geological picture" of the valley sides.  They are now quite convinced that a good proportion of the "rhyolite debitage" at Stonehenge and in the Stonehenge area has come from this valley.  The "dolerite debitage" makes up the bulk of this debris -- and there are other rock types in it as well.  The origins of much of this material are currently unknown.

The Quarryman's tale



I forgot to give an account of Josh Pollard's interpretaton of the Craig Rhosyfelin dig -- he was one of the three presenters at the Newport lecture session on 15 September.

Josh was in no doubt whatsoever that the site of the dig was indeed a Neolithic quarrying site.  (I think he even suggested that quarrying might have been going on here since the Mesolithic.....)  He suggested that the big stone -- assumed to be a "proto-orthostat" or a big stone intended to be placed upright in the ground -- was levered from the quarrying face above and fell onto the ground, where it was then prepared to be taken away on a sledge.  He suggested that its resting angle on the ground was "unnatural" and that it had been levered round to a position where it could be taken away more easily.  I'm not sure whether he thought this big stone had been shaped or modified in any way, but he certainly suggested that the excavation pit was full of man-made debris -- sharp-edged fragments and also rounded hammerstones brought from elsewhere -- he suggested that some of them were so round in shape that they probably came from the beach at Newport.

We were shown a couple of photos of the "hammerstones" -- and he claimed that one at least was a "waisted hammerstone".  One of them was certainly very well rounded, but the others didn't look very convincing to me -- and we didn't see pictures of any of them in situ.  As I said in a previous post, I wouldn't mind betting that there are fluvioglacial gravels -- incorporating well rounded stones -- under the jumbled rockfall debris exposed at the bottom of the excavation pit.  So how many "hammerstones" were collected, and where were they in the stratigraphy?  That's an interesting question, since if they were found lower down in the sequence than the big stone, or higher up, then logic dictates that they can't have anything to do with the claimed "quarrying" of the stone...........

Josh also said that the big stone was "propped up" on two big supporting stones that had been inserted beneath it to take its weight and make it ready for placing on a sledge.  I searched for these stones, and have to admit that I didn't see anything that looked as if it was in an "unnatural" position.

So why, according to the MPP / JP / CR story, was the stone left there instead of being carted away?  I got a bit lost at this point, although Colin Richards came in on this too -- there was something about the site being magical or sacred, but not necessarily the stones.  So the act of quarrying was the sacred duty, investing the quarrymen with great power -- but the stone itself, once taken from the rock face, was then deemed to be less sacred.  There was something, too, about stones starting off as coming from the abode of the ancestors, then becoming female, and then becoming male. (Or was it the other way round?)   The stones were intended for use in sacred stone circles -- but the circles were the sacred features, and not the stones of which they were composed.  I think there was a hint that the stones were intended for the Waun Mawn "circle"  -- but no evidence was provided to support that contention.  So why was this stone -- if it was deemed so splendidly magical -- left here instead of being taken away to wherever it was supposed to be used?  Still no answer to that........... in spite of lots of fine words about duty, honour, ancestors and symbolism.

I suggest we take this whole story with a pinch of salt, for the following reasons:

1.  There appears to be nowhere on the rock face above the big stone from which it might have been levered. (One might expect some less weathered rock surface, if not a "gap" in the face, if there had been quarrying here.)

2.  There don't appear to be enough hammerstones -- at the right level in the stratigraphy -- to demonstrate that quarrying went on here.

3.  Any rounded stones found in the excavated debris are more likely to have come from neighbouring fluvio-glacial or morainic deposits than from human intervention.

4.  There don't appear to be any arrow heads, axe heads, antler picks or organic materials, or even pottery fragments, which might give an independent "fix" on what went on here, and when.

5.  The sharp rock fragments which are supposed to be fragments "split off the rock by the quarrymen" look to me like perfectly normal bits and pieces of frost-shattered debris and rockfall scree.

6.  The rocky debris exposed in the bottom of the pit seems to me to be perfectly natural, as you would expect beneath a series of rocky crags.  There doesn't seem to be any trace of a hard-packed "working floor" such as you might expect if many men were working here over a long period of time.

Somebody's looking.....

Just got my site meter report -- 51,400 page views so far, and 26,000 site visits.  This all started as a bit of fun -- but it looks as if a lot of people are now following the blog.  Hope you are enjoying it, folks -- and thanks for your interest.  I'll do my best to bring a non-archaeological dimension to all of this bluestone / Stonehenge stuff, and to explain the geomorphology and glaciology as best I can.

The Times Atlas and the Greenland ice edge

Many of us will have followed one of this week's big stories -- about the Times Atlas misrepresenting the extent of ice wastage around the edges of the Greenland ice sheet.  Part of the reason for their misunderstanding seems to be the misapprehension that ice sheets have nice simple edges that move forwards during the waxing phases of glaciations and then move back when a glaciation comes to an end.  So the simple idea is that you can just draw a line on a map, and that's sorted.......

But this is not what happens, except where you have a gently undulating plain under the ice, as in parts of SW Greenland today.  Elsewhere, as the ice thins, the edges of the ice sheet tend to break up into scores or hundreds of smaller ice sheet fragments or ice caps, on plateau surfaces and mountains, while the valleys between them are deglaciated and become green.  Troughs that were under the ice are also exposed -- to become fjords near the coastline.  Look at these pics from Google Earth:

 The top image is of Nordvestfjord near the coast of east Greenland; I defy anybody to draw a line on a map showing where the ice sheet edge is today -- plateau ice caps, glaciated uplands, and outlet glaciers and valley glaciers everywhere.  Many of these ice masses are in a relatively healthy state -- we cannot just assume that they are wasting away at a catastrophic rate.

The lower pic gives a very different impression.  Here in SW Greenland the ice edge is retreating across a deeply scoured lowland, and as the ice thins the edge does indeed retreat in the classical sense. 

So -- generalisations are bound to lead to trouble.......

This pattern of ice sheet growth and ice sheet breakup is very close to what Henry Patten and others are finding in their models for the last (Devensian) glaciation.  If you run Henry's model of the expansion and contraction of the Welsh ice cap you will see a sort of flickering effect, with little ice caps (including one on Preseli) coming and going in step with climatic oscillations, eventually being "gobbled up" by the main ice cap, and then becoming independent and isolated again as the glacial episode draws to a close. 

And the relevance for the South-west of England and Stonehenge?  Well, I am increasingly convinced that there WERE small independent snowfields (and maybe actual glacier ice, frozen to the bed) in the upland areas including the Mendips, Exmoor, Dartmoor and Bodmin.  As the ice thickened in the Bristol Channel and as the Irish Sea Glacier started to move in, these independent areas of ice became incorporated, or coalesced together, to create a very complex area on the "ice sheet periphery" -- with some areas of flowing or moving ice and other areas where the ice may have been stagnant, playing a protective rather than erosional role.  We need to get this picture into the heads of all those who take part in this debate, because too many people see the Irish Sea Glacier as something which had a sharp and definable edge to it.  Visions of vertical ice cliffs trundling in from the west......   I myself plead guilty to portraying the ice front as such, in an attempt to simplify and explain.  Maybe it's time to make things more complicated and more realistic.....

Friday, 23 September 2011

On timid geomorphologists



In previous posts I have complained (ever so gently) about geomorphologists who refuse to intervene and tell it as it is, when eminent professors in another discipline (archaeology) trot out utter nonsense about the extent of glaciation in SW Britain.  I have even exchanged messages with one eminent geomorphology professor who insists that even if the ice of the Irish Sea Glacier did reach Somerset (which it did) that it is of no relevance whatsoever to the Stonehenge bluestone debate.  "Irrelevant?" I hear you cry.  Yes indeed -- I am reporting his words very accurately.

Well, I was reminded the other day that not all academic geomorphologists and glaciologists are so timid or so complacent.  Here is a quote from the big paper (which I have talked about before) which seeks to model the behaviour of the last British and Irish ice sheet:

"The experiments presented also indicate significant excursions of wet-based ice into areas of southern England, where little evidence of recent glaciation has been found. This may not present such a major problem given that our model indicates ice was at this extended limit for less than 1 ka. The experiments also provide support for a possible glacial mechanism for the movement of Preseli erratics as a transport trajectory which overrides parts of northern Pembrokeshire and was subsequently deflected south- eastwards across the Bristol Channel into SW England, cannot be completely discounted."

"Dynamic cycles, ice streams and their impact on the extent, chronology and deglaciation of the British–Irish ice sheet"
Alun Hubbard, Tom Bradwell, Nicholas Golledge, Adrian Hall, Henry Patton, David Sugden, Rhys Cooper, Martyn Stoker

Quaternary Science Reviews 28 (2009) 759–777

These guys know what they are talking about -- and they support many of the things I have been saying in previous posts about the entrainment and transport of erratics from North Pembrokeshire.  Their wording is of course quite cautious, but that's fine by me -- and their conclusions are very different indeed from those of certain academics (who should know better) who have stated on the record that the glacial transport of the bluestones was "impossible."

We are not necessarily talking about good and evil here, but the famous paragraph from Edmund Burke comes to mind:
"It is not enough in a situation of trust in the commonwealth, that a man means well to his country; it is not enough that in his single person he never did an evil act, but always voted according to his conscience, and even harangued against every design which he apprehended to be prejudicial to the interests of his country. This innoxious and ineffectual character, that seems formed upon a plan of apology and disculpation, falls miserably short of the mark of public duty. That duty demands and requires that what is right should not only be made known, but made prevalent; that what is evil should not only be detected, but defeated. When the public man omits to put himself in a situation of doing his duty with effect it is an omission that frustrates the purposes of his trust almost as much as if he had formally betrayed it. It is surely no very rational account of a man's life, that he has always acted right but has taken special care to act in such a manner that his endeavours could not possibly be productive of any consequence."

This is the famous paraphrase:   "Always remember, that the only thing necessary for evil to triumph is for good men to do nothing."

If we can agree that the perpetration of lies and the deliberate misleading of gullible people is closer to evil than it is to good, we have a point worth making......

Thursday, 22 September 2011

The HQ of the Nevern Valley tribe?



If you have read my bedtime story you will be aware of the MPP theory that the Nevern Valley was home to a very powerful tribal grouping of peoples who were astute in the use of stone and the creation of magalithic structures maybe around 4500 BC.  These were, according to MPP and his colleagues, not just burial chambers -- they speculate that they were built as acts of bravado or as monuments, not meant to be enclosed or buried beneath long barrows.  That will all be debated by the archaeologists -- but I suppose one of the things driving the theory is the idea that there is a distinct Nevern Valley grouping of megalithic structures, supposedly distinct from other groups.  NP Figgis refers to this group as "The Newport Group" of six burial chambers / monuments.  Not sure that is enough evidence for talking about a whole culture which was distinctive from its neighbours, but we'll let that pass......

Anyway, in looking for confirmation that this area was home to a powerful tribe with a penchant for innovation and stone working, MPP and his colleagues have homed in on Castell Mawr (shown above) -- a very spectacular and large hillfort on a rounded summit (not far from Castell Henllys), always assumed to be from the Iron Age.  They now say that they can see signs of  a Neolithic defended village under the ramparts -- and it looks as if they plan to examine it next year to see if that can be confirmed.  Fine, as far as it goes -- but as I'm getting rather fed up of saying, this has nothing at all to do with Stonehenge.

Even if there is a nice old Neolithic village buried here, what that shows us is that Neolithic people lived here in this area -- which we knew already.  It appears that Neolithic settlement sites -- previously largely unknown in Wales -- are now popping up here, there and everywhere.  That's fine, and it shows that the archaeologists are doing a good job of pushing our knowledge of communities further and further back in time -- but I wouldn't mind betting that when the press releases from this summer's dig appear,  this will be flagged up as having more than a little to do with the Craig Rhosyfelin "bluestone quarry" and the old monument on Salisbury Plain................

Ulster white limestone at Kenn

Ulster White Limestone -- Murlough Bay, Northern Ireland.  Here the limestone overlies Trias.

I have been reminded several times in the last few days about the erratic boulders (some weighing several tonnes -- which makes them as big as the Stonehenge bluestones) in the area around Kenn and Court Hill in western Somerset.  At Kenn Pier David Gilbertson found till with a large striated boulder of Carboniferous Limestone (origin unknown) and also other striated boulders, including one which was over half a tonne in weight.  In the body of the till at Court Hill there are boulders (up to .5m in diameter) which have been identified as Carboniferous Limestone, Pennant Sandstone, Mercia Mudstone, Old Red Sandstone, Greensand chert and flint, and Carboniferous chert.    It's difficult to know where some of these have come from,  but the authors who have described these deposits infer that they have come from the west.

Now then -- how on earth did an erratic of undoubted Ulster White Limestone (a variety of chalk) get from Ulster to Somerset?  If ever you wanted evidence of ice crossing Pembrokeshire and reaching this Somerset coast, this is it.  From everything we know about ice streams and erratic transport, there is no way that glacier ice can have flowed from Ulster across the uplands of mid-Wales, because these uplands were occupied by the Welsh ice cap -- so if you reconstruct flowlines the ice has to have crossed Pembrokeshire.  This does not mean to say that there will be Pembrokeshirec erratics here -- the entrainment of erratics, and their onward transport, depends upon so many factors that the ice that transported this erratic (and there must be other erratics like it, as yet undiscovered) might have flowed across Pembrokeshire far above the present land surface, underlain by a great thickness of either stagnant or sluggish ice.  We still have to work all of that out.....

Monday, 19 September 2011

Are you sitting comfortably?


Then I'll begin.  Once upon a time, a long time ago, before people knew how to make things out of metal, there were two great tribes living in the land called Britain.  One great tribe lived on the chalklands of England, with their headquarters in a village called Durrington Walls, and the other great tribe lived in the Nevern Valley in West Wales.  The tribe living on the chalklands of Salisbury Plain enjoyed having barbeques, partying and feasting at every opportunity, and rock concerts were often held in their favourite concert venues including Stonehenge and Bluestonehenge.    People would travel from far and wide to these concerts, even from Scotland, Wales and the distant lands to the east.  But when they were not partying they were very fierce, and in enforcing their rule over weaker tribes they insisted on the periodic payment of tributes in the form of cattle for their triple Big Macs.  They also quite liked to get ancestor stones and other things as presents.


The tribe that lived in West Wales was also a very powerful one, and its rulers lived on a hilltop in a large village called Castell Mawr.  The members of this tribe were not so much into BBQs, but they were very spiritual people who were skilled in the working of stone.  They had to be, because there were bloody stones everywhere, just getting in the way.  So they moved stones about, and somebody had the idea, once upon a time, to raise big flat stones up onto standing stones or pillars, thereby creating wacky megalithic follies.  After a few generations their priests got into the habit of looking on these stones (which were now old and venerable) as sacred objects, and a cult emerged which believed that big stones in the ground were either male or female, or else contained the spirits of their dead ancestors.  Soon there were all sorts of rituals going on, which we still do not understand, but which probably involved virgins and sacrifices.


Some rocks were, in their eyes, more sacred than others, and in all the special sites where these rocks could be found, the people opened up quarries, took away the most auspicious stones, and built them into great circles of standing stones.  Their most favourite circle was at a place called Waun Mawn, on the lower slopes of the Preseli Mountains, a couple of miles from their favourite quarry in the valley of the Afon Brynberian, and maybe three miles from their village.  That circle had 59 standing stones in it, and truly MIGHTY rituals went on there whenever they felt inclined.  


But all was not well between the Salisbury Plain Gang and the Nevern Valley Gang.  The former coveted the splendid stones that were available to the latter in abundance,  and the latter were quite envious of the nice weather further east, and all the great gigs that were organized over there.  So the gang leaders had a big conference  on neutral territory -- probably in a nice conference centre somewhere near Bristol, and they agreed a deal.  The SPG agreed that the NVG could come and take part in their gigs and raves, so long as they brought with them as a peace offering and token of esteem their absolutely most favourite stone circle.  The NVG dithered a bit, because they were really rather fond of it themselves, but then they thought of all the good parties they might miss at Durrington Walls, and so they finally agreed.  They went home and started to dismantle the great stone circle, and managed to take 56 of the stones away on rollers and sledges -- but they ran out of steam, and never managed to take away the last three stones.  At any rate, off they went eastwards, over hill and vale, through jungle and swamp, and thirty years later they arrived at Stonehenge, older and wiser but still looking forward to a few good parties.  They put up the stones in a great circle as a token of their esteem, and gave the SPG some lessons on how to put up big stones and how to put other stones on top of them.  Then, bearing in mind that all their stones had names and were, in their eyes, the embodied spirits of their ancestors, they all did a jolly fine ritual.  That over and done with, they all started to have a great BBQ which went on for a year and a day, with vast numbers of cattle consumed and bones scattered all over the place.  (Their table manners left a bit to be desired, since they were all drunk at the time.)


Then a great peace treaty was signed -- or it would have been, if only they had been able to write.  This was later to be known as THE GREAT NEOLITHIC UNIFICATION, and it was the first time that there had ever been a unification between two of the great tribes of Britain, one from the west and one from the east.  And so they lived happily ever after.  

The end.

=======================
With grateful acknowledgement to Mike Parker Pearson.  I have recorded the story as accurately as I could, when I first heard it, given that there was a lot of unnecessary material included, which I thought it best to exclude in case any of my listeners is of a sensitive disposition.

Where is the GBG limit in SW England?

As my faithful fellow-bloggers know, I have spent a lot of time on this blog trying to work out where the GBG limit may be in SW England.  (Are we talking here about one big glaciation?  Or maybe we are talking about several glacial episodes, spread over hundreds of thousands of years, and reaching different parts of the Bristol Channel coastline at different times?)

This has all come into focus again because my dear friend MPP has repeated what my other dear friend GW has said several times on the record -- namely that glacier ice has never affected the coasts of Devon, Cornwall, Somerset and the SW generally.

Interestingly enough, academic geomorphologists, whom we would expect to know about these things, have chosen by and large to stay well clear of the discussion, for reasons that I find hard to understand.  (Are they actually SCARED of Profs GW and MPP?  That would surprise me, since they both seem to me to be perfect gentlemen.)  But if you press them, of course they know that the ice DID reach these coasts on the shores of the Bristol Channel.  It's just that they don't want to say so, for fear of being knee-capped or something. 

In exchanging messages with various colleagues whom I respect, I got this reply from one of them.  He says there are "..........very clear signs of glaciation further north at Kenn in what was Avon and in the Bristol-Bath area.  There are some amazing landforms such as the Court Hill col-gully, infilled with fluvioglacials, including enormous boulders until they put the M5 through.  Some of the infill deposits are still visible in the wood beside the motorway.  At Kenn, till-like material, which includes striated boulders weighing several tons, is overlaid by marine and non-marine interglacial deposits. Amongst the erratics recovered were a piece of Ulster White Limestone, which contained the usual characteristic foraminiferal fauna of this unit. See the many papers of Dave Gilbertson's work in the area, and his PhD thesis, summarised and updated in the GCR volume.   Aminostratigraphy suggests several ages for the interglacial deposits - some are as old as OIS 15 (although there should be a considerable health warning on all these very old aminostratigraphic 'dates', as Kirsty Penkman has demonstrated!)  I spent some time working on the issue of glaciation in this area, with follow-up investigation in the Kenn area, in Gordano and in the Bath/Bristol Avon valley.  There is no doubt in my mind about a glacial incursion in that area, as far upstream as Bathampton, but no further. There are plenty of erratics recycled in the river gravels at Bathampton and elsewhere through the valley, mostly derived from the Bristol District and/or the S Wales coalfield, but I never saw any bluestone fragments, in any of my pebble counts."

I won't mention his name, for fear that medics in white coats or heavies in dark coats will come calling on him, but that sounds pretty unequivocal to me.   He also says:  "My work with erratic palynomorphs suggests that the ice sheet that was responsible for the deposition of the Fremington Clays was coming pretty well southeastwards and the ice coming onshore at Fremington would probably have 'missed' Pembrokeshire".

I think I'm right in saying that everybody who knows anything about glacial deposits accepts that we have a true glacial till at Fremington, and more till on Lundy Island, and more till on the north coasts of the Scilly Isles.  There is a lot of debate about other deposits, like the Trebetherick Boulder Bed, but that's enough evidence to be going on with, and if we have a number of sites where glacial deposits are widely accepted (Kenn, Court Hill, Nightingale valley, Bathampton, Lundy, Fremington, and the Scillies, to name just some) then only an idiot would say that the ice did not cross the Bristol Channel.

But the idiots keep on saying it, and those who should put them right just keep on saying nothing.  This is a very strange and even bizarre sociological and psychological phenomenon, and even a hoary old ex-academic like me (having seen most things in my time) finds that very strange.  This is actually nothing to do with academic etiquette.  That requires the experts in a particular field to assess the evidence and speak out, and the non-experts to keep quiet or to defer to the experts.  But here we have the non-experts pontificating and the experts shrinking away into the undergrowth on the grounds that they "don't know enough about the subject."  Oh my God.....  whatever happened to academic integrity?

Pont Saeson rhyolite at Stonehenge?

The Scarlet Pimpernel (or whatever he currently calls himself) asked if I would put up a post with the pic of stone 32e at Stonehenge alongside a pic of the "bluestone" found in the pit at Craig Rhosyfelin.
Happy to oblige.  Note that the recently uncovered stone has a rather flaky structure, revealing flattish faces when the flakes peel off.  In the Atkinson picture from Stonehenge the stump on the left is vertical, and the stone is smaller, but the structure does look rather similar.  We don't know whether the rock types are identical, because as far as we know the Stonehenge stump has never been sampled in recent times, so at the moment all is speculation.  All we know is that stone 32e is made of rhyolite.  Many rhyolites have this sort of flaky structure, as I know from living in this area.

Not that I mind at all where it's come from.  If the geologists have found the source of stone 32e at Craig Rhosyfelin, then that's great.

A prophecy fulfilled



Remember my post of about a week ago relating to the three stones at Waun Mawn, near Tafarn y Bwlch?  Well I speculated that the MPP team would interpret that as the remains of a dissembled stone circle, with the same diameter as one of the key circles at Stonehenge.  I was assuming it would be the Aubrey Circle, with a diameter of 86m, on the basis that the Aubrey Holes might at one time have contained stones. 

And so it transpired.  The speakers at the Newport lecture didn't devote a lot of time to this, but MPP did say that the Aubrey Holes did contain stones, and that the pits or sockets that held them had "exactly the same dimensions" as the known bluestone sockets at Stonehenge and the sockets at "Bluestonehenge" that were also assumed (without any evidence, as far as I can see) to have contained bluestones.  That's all a bit strange, because the bluestone orthostats and stumps come in many different shapes and sizes -- but we'll let that pass.  What's a little generalisation or two among friends?

So the story is this.  A gigantic stone circle was set up at Waun Mawn -- with 59 bluestones in it.  It became a great centre of ritual activities, and then for some reason it was shifted lock, stock and barrel, from here to Stonehenge.  For some reason the engineering teams left three stones behind -- but no doubt the sockets are still there, in the ground, waiting to be discovered in the 2012 digging season.  When they got to Stonehenge with the stones, having taken them overland (MPP doesn't like the maritime transport hypothesis) they didn't have enough stones to make up the whole bluestone circle -- they needed 82, and they only had 56.  No problem.  Just down the road was Bluestonehenge, with all these lovely stones in a circle.  So they took  26 bluestones from there and hey presto! they had made up the numbers.

Here endeth part one of the story.  If you think that's terribly exciting, just wait until I tell you the rest of the story...

Craig Rhosyfelin -- Hammer Stones galore

At the lecture in Newport the other evening, great stress was placed on the discovery of so-called hammerstones in the "bluestone quarry."  Our learned lecturers showed us some pictures of the hammerstones, but they did not seem to be in situ in the deposits of broken scree -- and the precise stratigraphic relationships of these stones remains to be revealed.  Surely they didn't pick them up from the river, did they?  No no -- perish the thought -- that would have been too naughty.

The river is only about 20m away from the dig site.  I wandered down there and took a look, and within a couple of minutes I found a veritable assemblage of beautifully rounded stones in the river gravels.  I wasn't surprised -- that is what one finds in river gravels.  The pics above show some of these.  The blackish stones in the top photo are very nice -- the smaller ones are slightly flattened, but with well rounded edges.  You could, I suppose, use them as hammer stones if you wanted to.  The one on the left is too large to be called a hammer stone -- you would need two hands to use that for knocking or shaping a larger stone.  So you would -- if you were so inclined -- call it a "maul." 

The stone in the lower two photos is a perfect hammer-stone shape -- but again I picked this one up in the river.  It's certainly not local -- goodness knows where it came from.

Back to the geomorphology.  I'm pretty sure, as I said in an earlier post, that the floor of the valley  -- under the veneer of modern sediments -- is covered with fluvio-glacial accumulations.  There will be hundreds if not thousands of stones shaped like the ones in these pictures.  I wouldn't mine betting a few coppers that if the digging team in the quarry had gone down a bit further, they would have come to fluvio-glacial sediments full of flattened sub-rounded stones of rather local origin and a few well rounded stones from far-away places.

Maybe all will be revealed if they carry on with the dig in the 2012 field season.  In the meantime, scepticism is entirely in order....

Friday, 16 September 2011

Credit where credit is due.....

In spite of my hearty criticisms of the people involved in the latest archaeology researches in Pembs, I really don't want to frighten them away!  The natives are not all that hostile......... and it's great that some attention is being paid to our very rich heritage of features across North Pembs in particular.

And there were some very interesting things coming out of the talk last evening.  Here are some snippets:

1.  MPP suggests there are no less than nine rectangular dwellings on the slopes beneath the Carn Meini outcrops.  He suggests that they are probably Neolithic, because Bronze Age and Iron Age dwellings tended to be circular.  Sounds reasonable to me -- more info eagerly awaited.  (Mind you, not sure I'd go along with the aside that this was probably a "quarryman's village".........)

 If you zoom in hard on this Google image of Carn Goedog, you can see some faint rectangular patterns at the top left corner.  Maybe these are the "Neolithic" dwellings?

2.  There was some very interesting work reported by Colin Richards on the cromlechs / dolmens of the area.  There has been a big dig at Garn Turne (the one with the enormous capstone) -- and he reckons that here, as at Pentre Ifan and Carreg Samson the stones that have been used as capstones were originally embedded in the ground and have been lifted up onto supporting pillars without being moved very far, if at all.  He thinks they may not have been at the centre of earth or stone mounds at all, but that they were megalithic monuments in the true sense of the word, in the same sense that the trilithons at Stonehenge are "monuments".  He also thinks that they are very old -- maybe as old as the dolmens of Brittany, some of which go back to 4,500 BC.  I like the "use what's on the spot" idea -- and that of course is exactly what Steve Burrow says in his book.  But a little bit of me thinks that he's got another ruling hypothesis going here -- namely that these monuments like Pentre Ifan were the precursors or the "models" for what came a bit later art Stonehenge.....

3.  MPP reported on some recent geophysics (as yet unpublished) that suggests that the empty quarter at Stonehenge was indeed an empty quarter, and that the monument was never finished.  Well well, never thought I'd hear him saying that.....  Dave Field must be pleased, as I am pleased.

4.  To my unpracticed eye, it seems to me that the digs at Garn Turne and Craig Rhosyfelin have been conducted with great professionalism, carefully marked and meticulously recorded.  I look forward to seeing the info when it is all written up, and hope that the papers will tell it like it is, and just spare us the fantasising.

The Craig Rhosyfelin dig





Since you asked .... here are some pics of the dig at Craig Rhosyfelin. As you will see, we are looking at a craggy outcrop of rhyolite on the flank of a gorge cut by glacial meltwater and now occupied by a relatively small stream (Afon Brynberian).  Adjacent to the jointed and sloping surface of the rhyolite, there is a big bank of blocky scree -- this is obvious from the photos.  Many of the angular blocks have been left in situ by the diggers.  Some of the blocks have rounded-off edges, suggesting to me that there has been meltwater erosion at some stage, with a stream maybe flowing over and through the scree bank. This would not be surprising, since the dig site is at the point where a little tributary valley comes down into the main valley.  The big block, which is causing so much excitement, is incorporated into this scree and lying on top of it.  There is another big block beneath a tree stump which the diggers have left in place.  On top of the scree there is an accumulation of slope deposits rich in organic material  -- no doubt the dig team will send some of that for radiocarbon dating.

On the rock face, there is another large slab of rock which is still in place -- but it would not take much in the way of pressure from roots -- and maybe frost shattering - to prize it off and send it crashing down.  No human involvement needed.  This is the slab:

So what can we say about the history of the site?  Well, the gorge may be very old, but it will certainly have carried meltwater torrents during the ice wastage phase of the Devensian glaciation.  That means that on the floor of the valley there will be abundant fluvio-glacial deposits containing rounded and sub-rounded pebbles of all shapes and sizes. (In the dig, the archaeologists have not got down deep enough to find these fluvio-glacial materials -- sands and gravels -- but I would put a few quid on the fact that they are there all right.)  When the ice retreated from this area around 20,000 years ago, there were a further 10,000 years or so of periglacial conditions during which rocky outcrops all over West Wales were subjected to frost shattering processes, with steep slopes partly covered by accumulations of scree.  There would also have been considerable snowmelt from snow-patches, in deep valleys such as the Afon Brynberian gorge.  Then the climate ameliorated in the Holocene -- after the final cold snap of the Younger Dryas.  The slope deposits shown in these photos have accumulated over that period -- there are some quite clear layers, and it will be interesting to see how these are interpreted with reference to Holocene climate changes during the Mesolithic and Neolithic -- and more recently as well.   So that's my bit of geomorphology, in which I have considerable confidence.

The upshot of all of this is that I don't see the slightest sign of any quarry here -- but I am always open to whatever evidence the archaeologists might wish to bring forward in support of their thesis.

I would have been only too happy to look at the dig in the presence of the archaeologists, and to help them in their interpretations, but two Email offers to MPP that we might meet for a chat were ignored, and I would have been only too happy to make a site visit in their company.  The Dyfed Archaeology team also know my views well, and if I had been asked, I would have been only too keen to help.  Then last night I arranged to meet the dig leaders at the site at 9 am -- and found, when I got there, that they were nowhere to be seen.  A few friends and I pottered about a bit, and took some photos, and Felix did some sort of ritual, in his bare feet.  Then when it started to rain we wandered off, patience exhausted.

Not sure what the etiquette is relating to photos of other people's digs, but in the circumstances I have no qualms.  After all, I helped to pay for it.  Anyway, so many people have visited the dig over the past two weeks that there are probably hundreds of photos of it on the web already.....

An evening of fairy tales

Craig Rhosyfelin, a magical place -- with fairies lurking among the rocks.  The dig site is just behind this crag, at the junction between the rock outcrops and the valley floor
 The dig site, showing the "big bluestone" and its relation to the rock outcrop and the slope deposits that have come down from the right, towards the valley floor.

Patience, dear reader.  This may take a little time.  I am still trying to adjust to the real world again, after an evening of fairy tales in the presence of three (no, there may have been 20) learned archaeologists.  The occasion was in Newport Memorial Hall, last evening, and the talk was free to allcomers, hosted by the Dyfed Archaeological Trust and paid for by the taxpayer.  ("Is that relevant?" I hear you cry?........ Well yes, actually it is......)

The coffee and biscuits were very nice, the displays were impressive, and members of the audience were welcomed to scan through images from the latest digs on the laptop computer set up specially for that purpose.  That was very considerate of the organizers, given that not everybody has been able to visit the dig site at Craig Rhosyfelin.  After a friendly welcome from a lady from the Trust, we were treated to a talk split into three parts. 

Prof Mike Parker Pearson talked about Stonehenge, Bluestonehenge, Durrington Walls and other things, and about the work over the last couple of weeks at the "Carn Goedog Quarry"and the "Rhosyfelin Quarry".  Some of the things he said had me hopping up and down in anguish, but I am very good at pain control.  Then Josh Pollard took over, and talked in detail about the big dig during which they have found the stone shown above.  There was not a moment of doubt in anything he said -- and every piece of "evidence" uncovered was neatly slotted in as supporting the story of the heroic excavation of the site by Neolithic people who were connected in some way with local stone circle building and with Stonehenge.  Having established to their own satisfaction that the area was of huge significance during the Neolithic, Colin Richards took the baton and sought to answer the question: "Why was this area so important?"  He assembled information from Indonesia, Madagascar and Easter Island to emphasise the sacredness of stone and the mighty efforts made by societies -- then and now -- to move stones over long distances for ritual purposes.

What interested me was the absolute certainty of the three speakers regarding their central thesis, and the utter conviction that because they are learned gentlemen with high academic positions, we just have to believe what they say and all will be well with the world.  At no point was there any attempt to assemble field evidence, present it impartially, examine a number of explanations for whatever had been found, and then propose a reasonable hypothesis for future testing.  Don't archaeologists do that any more?

I was also struck by the fact that there was no mention during the evening of the glaciation of Pembrokeshire and the presence everywhere of glacial, fluvio-glacial and periglacial deposits -- and the influence that glacial events might have had on their findings on the ground.  They had clearly taken no advice at all from a geomorphologist -- and had nobody on their team capable of pointing out to them the simplest facts about Ice Age deposits and how they are distributed across the landscape.

At any rate, after the talks there were a number of polite questions and comments from those who did not know enough about the subject to challenge anything very much, and then I managed to catch the chairperson's eye and had a go at the three presenters.  I have to admit to being a bit worked up, so I have no clear recollection of what I said, but I did accuse them of abandoning the scientific method and of twisting everything into a central ruling hypothesis that was unsupportable.  I also said that nothing I had heard during the evening seemed to have any relevance at all to Stonehenge, in spite of their continuous assertions to the contrary.  I also accused MPP of either misunderstanding or deliberately misrepresenting the views of those he has consulted (and especially Prof Chris Clark) relating to the extent of British glaciations -- and of repeating the nonsense that glacier ice never affected the shores of Somerset, Devon and Cornwall.

Afterwards, MPP spluttered a bit, but refused to answer any of my points.  Maybe he spends too much time surrounded by sycophants and students and not enough time actually discussing things with earth scientists?

So there we are -- fairy tales is what I expected, and fairy tales is what I got.  Don't know whether to laugh or cry.......

Thursday, 15 September 2011

On big stones in rocky places

A little bird who flew over the other day tells me that the MPP team has found a big elongated stone in their latest dig, at the tip of the rhyolite outcrop of Craig Rhosyfelin.    No idea how big it is, or how deep beneath the surface it was found.  All will revealed.....

A big stone in a rocky place?  No big deal for a geomorphologist, since we see such things every day in the field. (I could fill up an album of photos of big elongated stones embedded in the turf all over the Preseli region.)  But obviously such a "find" is a very big deal for an archaeologist, especially if you are hunting for quarries and bluestone orthostats, and have to justify your latest research grant!

How often have we seen this wild excitement before?  Quite often, and every now and then the excitement is stoked up again, especially if there happen to be some TV cameras in the vicinity.  Many years ago Roger Worsley and Robert Kennedy got very excited over the "bluestone that got left behind" at Carn Meini.  This one:


Then in 2009, Profs GW and TD got very excited (cheered on by the Royal Commission) about the "broken bluestone that was left behind when somebody carelessly dropped it" .... This one:


And I remember vividly the great pleasure everybody had more than 30 years ago when somebody found a lump of something hard and bluish on the bed of Milford Haven, and people spent good taxpayers money diving to the bed of the Haven and grovelling about in the mud, looking for the "bluestone that fell off the raft and was lost."  I told them at the time that the bed of Milford Haven is littered with erratics -- mostly from the St David's Peninsula -- but they were not inclined to listen, because they were fixated on the bluestone transport myth and were hell bent on confirming its correctness.

Has anything changed?  I doubt it.....

Tuesday, 13 September 2011

Did the Irish Sea Glacier reach the English Channel?



 




Long, long ago, BMPPTDGW (before MPP, TD and GW) our old friend Geoffrey Kellaway suggested that glacier ice had reached the English Channel.  He was, of course, laughed out of court ... although I hope I gave his ideas some degree of respect in my discussions on this blog concerning the "giant erratics" on the coasts of Southern England.

Well now, time to think again.  Thanks to Henry for drawing this to my attention -- a presentation by Daniel Praeg which has recently been made at specialist conferences.  No doubt there is a considerable stir, because what these guys are showing from their work in the Celtic Sea is an extraordinary series of parallel or "fanning out" ridges which run right out to the edge of the shelf, at c -200m.   That is far beyond the maximum ice limit as assumed by Chris Clark, myself, and everybody else.

These ridges are not of any great amplitude, and on top of them are smaller transverse ridges, but the authors are quite convinced that they are not marine bedforms or anything to do with currents, tidal streams or sea bed slumps etc.  They appear to me made of glacial or glacio-marine sediments, but it remains to be seen whether these sediments run right through the ridges, or whether we are looking at a surface veneer that might have been dropped from floating ice.  No doubt this will all be published in due course, and we will then be able to examine the detailed evidence.

The "accepted limit of glacial till" (the white line on the map) is wrong anyway, as we know from our discussions on the Bristol Channel, but if we reconstruct an ice margin based on the existence of these submarine ridges -- either in the Devensian or in some earlier glaciation, we have the intriguing possibility that glacier ice did indeed push well into the English Channel, maybe even to the east of a line drawn between Land's End and Finisterre.

See this earlier post:
http://brian-mountainman.blogspot.com/2010/06/sea-ice-and-giant-erratics.html 

Reference:  GLAMARous RIDGES : exploring glacial landscapes in the Celtic Sea
Daniel Praeg1, Stephen McCarron2, Paul Goldsberry2, Martyn Stoker3
(Powerpoint presentation -- available as a PDF)

Bluestone Quarries and Occam's Razor



We currently have the rather interesting sight of teams of archaeologists rushing about in West Wales and looking for bluestone quarries.  They have been encouraged into this by the recent geological discoveries which now indicate that the Stonehenge "bluestone assemblage" contains at least 30 "foreign" non-sarsen rock types, some of which are still unidentified.  The list is in my book.  Apparently, as far as we know, all of those stones have come from the west or north-west. (Why are there none from the east?  Answers on a post-card please...)

Let us imagine for a moment that HH Thomas had never invented the human transport myth.  In that case, there would not be a moment's hesitation in saying -- with the full agreement of the archaeological and geological experts involved -- that the stones are probably glacial erratics, dumped somewhere to the west of Stonehenge and collected for use in the building of the monument.  No other theory or explanation would be necessary, since that accords with the facts on the ground relating to ice movements and glacial history. These facts have been known for decades, and indeed the old geologists knew about the broad pattern of ice movements more than a century ago. The ice moved across Pembrokeshire from NW towards SE and continued to flow in that direction until it skidded to a halt somewhere in SW England.  That much is indisputable, and is supported by the evidence of glacial deposits on the ground. (What we still don't know is precisely where the ice edge lay at the time of its maximum extent.)

But we are stuck with the HHT theory, and we are stuck with a generation of archaeologists obsessed with the task of proving it correct.  So we are also stuck with a bluestone quarry hunt, no matter how absurd and illogical that might seem to rational human beings.  It's interesting that it's not just MPP and his team who are involved in this hunt -- Dyfed Archaeology and Cadw also seem to be backing it enthusiastically, as does the National Museum of Wales and the Pembs Coast National Park Authority.  Why?  Well, they will all bask in the glory of joint press releases and media coverage, and see "success" in the bluestone quarry hunt as bringing them extra publicity and extra tourist income for Wales.  Maybe a few staff members will even get a few seconds on the telly!  A nice win / win scenario............. with rational thought processes conveniently kicked into the long grass.

Let us suppose that the quarry hunters find some large stones in the places where they go digging.  What will that tell us?  That there are lots of large stones lying around in the vicinity of rocky crags and other outcrops.  Big deal.   That is precisely what you would expect anyway.  What if they find some smaller stones as well, in the vicinity of the big ones?  Big deal.  Again, that is precisely what you would expect in a landscape littered with scree and morainic debris.  What if some of these smaller stones look rounded enough to be called mauls of hammer stones?  Big deal. Boulders of all shapes and sizes, in glaciated areas, have their sharp edges knocked off and smoothed by ice and water action.  What if you find actual physical traces of tooling and working on a rock face?  Big deal.  That might mean that at some stage somebody has levered out some handy building stones for use in building a barn or a stone wall -- just as country folk have always done when they are building things. 

What if some arrow heads or Neolithic artifacts are discovered in the ground adjacent to a big elongated stone?  Now that becomes a bot more interesting, since it shows that people might have been collecting stones from here for a very long time -- either for building purposes, or in the gathering of material suitable for axe manufacture.  But this is still no big deal, since we have absolutely no reason to assume any link with Stonehenge or anywhere else, on the basis of the evidence in front of us.

What if the rock type of the nice elongated boulder found in your pit is shown by geologists to be the same as that of certain fragments found at Stonehenge?  That again is no big deal.  We know that already, and have known it for years.  In fact it was that identification (in the case of Pont Saeson) that brought you out quarry hunting in the first place.   Without that, you would never dream of digging a hole here or anywhere near here.   So we are into circular reasoning territory, with a vengeance......

In an earlier post, I wrote:   

As far as the science of landscape is concerned, our principle is this:  If a past phenomenon can be understood as the result of a process now acting in time and space, do not invent or invoke an extinct or unknown or supernatural  cause as its explanation.  By the same token, if a landscape can be understood by reference to known physical processes, even if they have varied through space and time because of climate change or crustal movements, do not bring in "invented" processes which are unverifiable through observation.


Stephen Gould said in 1987:  “We should try to explain the past by causes now in operation without inventing extra, fancy, or unknown causes, however plausible in logic, if available processes suffice.”


This is known as the scientific principle of parsimony or Occam's Razor.  This is a good definition: "Of two equivalent theories or explanations, all other things being equal, the simpler one is to be preferred". 

So why have these enthusiastic quarry hunters refused to take on board a simple and natural explanation for the Stonehenge bluestones, and have gone for something that involves circular reasoning and wild fantasies instead?  Corporate amnesia?  Mass hysteria?  Money?  Don't ask me -- ask them....

Monday, 12 September 2011

The latest "bluestone quarry"

This is the site which MPP and his colleagues have labelled a "bluestone quarry"  -- before even visiting the site to check it out.  If they want to find a quarry badly enough, they will no doubt find a convenient stone or two lying about near the crag, and a few smaller stones that will do nicely as hammer stones, and announce that they have confirmed that Neolithic quarrying was carried out here, and that stones were taken from here to Stonehenge.  Such is the way with ruling hypotheses.....

This is a nice aerial shot of the site, from Google Earth, showing the elongated craggy ridge (made of rhyolite) on the flank of the river gorge of the Afon Brynberian (which is a tributary of the River Nevern).