THE BOOK
Some of the ideas discussed in this blog are published in my book called "The Bluestone Enigma" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
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Friday, 31 March 2017

Foel Drygarn fortified settlement



Here is another fabulous image from the Bing satellite coverage.  It shows the Foel Drygarn hillfort / fortified settlement at the eastern end off the Mynydd Preseli upland ridge.

You can see very clearly the three Bronze age burial mounds, the main Iron Age (?) fortified site enclosed by an embankment (with the pitted surface showing where the huts were located), the subsidiary embanked area to the north (with more hut circles), and the animal enclosure (?) on the NW flank of the inhabited area. 

"Foel Drygarn" means "the bare hill with three cairns".

Wednesday, 29 March 2017

The edge of the Preseli Ice Cap?




Wizard wheeze for today.  New theory for us to mull over.

For some time I have been intrigued by what has gone on in the past in the southern foothills of Mynydd Preseli, in the zone that includes Rosebush, Maenclochog, Llandilo, Llangolman, Efailwen and Llanfyrnach.  There is a line in the landscape -- irregular, but quite distinct.   The thing that puzzles me in particular is the fact that to the north of this line there are no deeply cut valleys or gorges, but to the south of it we see a string of deeply cut winding valleys with some interesting features including connecting valleys and blunt-headed small tributaries. I cannot see any geological or structural reason for this contrast.  Could it be that the line connecting these "valley heads" represents a stillstand along the edge of a small Preseli ice cap?  We know that there are meltwater gravels at Rosebush and Llangolman -- I shall check out whether there are any others........  watch this space.

The valleys do not seem to be similar to those of the Gwaun - Jordanston meltwater channel system, which displays two features indicative of subglacial meltwater flow: an anastomosing pattern and humped long profiles.  The channels between Rosebush and Efailwen appear to be subaerial ones, which carried large torrents of meltwater southwards into the Eastern Cleddau catchment.

The satellite image, by the way, is from the Bing satellite coverage, with a slightly distorted "landscape"view.  It shows up the river gorges very well.

Postscript:

Here is a superficial geology map of the area, from the Geology of Britain Viewer.  It shows the occurrence of patches of sands and gravels mostly inside the line drawn on the image above.  Significant, or not?  We shall see......


POSTSCRIPT

Adding here the model by Henry Patton and his colleagues showing the theoretical extent of the Preseli Ice Cap at 23,850 yrs BP -- at the time of its proposed maximum extent.  The southern margin is very similar indeed to that which I am now proposing on geomorphological grounds.  What will be much more difficult to work out is the relationship between this little ice cap and the powerful Irish Sea Glacier which came in from the N and NW.  When did the two ice masses make contact, and what happened in the contact zone?  Did that contact zone oscillate over space and time?


Carn Meini and the Stone River



I'm more and more impressed with the quality of the satellite imagery on Bing.  Take a look here:
https://www.bing.com/maps/

This is a wonderful image of the Carn Meini (Carn Menyn) area showing the tors and the nearby "Stone River" (to the left) which some people insist on interpreting as an ancient trackway, without ever going to check out what it looks like............

I interpret it as a stone stream -- partly a periglacial feature, also used as a stream bed -- with much of the finer material washed out, leaving a "boulder bed" behind.

The quality of these Bing images is amazing -- and the small details in the landscape are enhanced by the low sun, giving rise to long shadows.

Earthfast Neolithic tomb, St David's Head


The famous cromlech near the tip of St David's Head, found in close proximity to an Iron Age fortified settlement site.  Strictly, this should be referred to as an earthfast tomb, since one end of the capstone has been levered up and then propped, but the other end still rests on the ground.  As usual, the guiding principle seems to have been economy of effort -- this big flattish stone was simply used where it was found.

St David's Head -- ice-moulded terrain


Ice moulded terrain near the outer tip of St David's Head.  The moulding may not all be due to the effects of the Devensian Irish Sea Glacier moving in from the NW, but the "cleaning up" of the surface almost certainly is.......


More ice-moulded surfaces on the north coast near St David's Head, looking towards Carn Llidi


Ice-moulded surface (glaciated slabs) near Carn Llidi


More ice moulding, on the summit of Carn Llidi 

The above images are all from the Google Streetview coverage of the Pembrokeshire Coast Path  -- the definition is a bit fuzzy, but the main features of the landscape are pretty well portrayed.

Pembrokeshire Coast Path on Google Streetview



An image taken from the Google Streetview sequence, showing the classic raised beach platform at Broad Haven South, on the south coast of Pembrokeshire

 Well done to the Pembs Coast National Park Authority!  Google Streetview arrives.....

This reminds me of the time when I slogged all the way round the Pembs Coast Path / National Trail, having been commissioned by HMSO and Aurum Press to write the definitive trail guide.  I did it in the winter -- which was less than ideal.  200 miles or more, exploring every nook and cranny, braving high winds, pouring rain and even snowstorms.  By Jove, it was Hell out there, as they used to say on the Goon Show.   Actually, it was rather a lot of fun, prior to sitting down and writing it all up.

Anyway, two brave souls have now flogged their way around the coast path on another crucial expedition, lugging the Google Trekker camera so as to provide all of us with a Streetview version.  Mostly, it is useful for walkers and armchair explorers, but it is actually very valuable for geomorphologists, geologists and botanists too, since we can examine minutely every step of the way.  At long last, all those places to which I have referred over the years on this blog can now be examined or "interrogated" by anybody who is interested.  I anticipate that I will use it a lot..........

(By the way, the coast path is 186 miles long, and the coast is 200 miles long, more or less.  The path cuts off quite a few peninsulas.)

https://www.google.com/streetview/#pembrokeshire-coast-path

Press release:

Panoramic views of the Pembrokeshire Coast Path just a click away

You can now view the Pembrokeshire Coast Path National Trail from your computer, mobile or tablet as the world-famous walking route has been added to Google Street View.
Google loaned the National Park Authority one of its back-pack mounted Google Trekker cameras last spring, making it possible to film the spectacular coastal scenery of the Pembrokeshire Coast National Park.
The task required filmmakers that were physically fit as the camera and equipment weighed 25kg, about the same as a sack of potatoes. Luckily two of the Park Authority’s Wardens were up to the task, with Alex Payne and Ainsley Corp swapping their mowers and strimmers for the Trekker to film the Coast Path.
National Park Authority Access and Rights of Way Manager, Anthony Richards said: “One of the main challenges was finding enough dry, bright and sunny days to film. We all had to be flexible and jump in at short notice, seizing every fine day to film. In the end it took 28 days, between April and June, but it’s worth it as it shows the National Park at its absolute best.
“The Coast Path provides a spine for dozens of circular walks, which are promoted on the National Park website; it will allow people to preview a walk to work out if it will be suitable for them in terms of its terrain and cliffs. You can also now just scroll along and enjoy the views of iconic landmarks such as the Green Bridge of Wales, or some of the more remote and lesser known stretches of coastline.”
The online footage of the Pembrokeshire Coast now joins iconic landscapes such as the Grand Canyon and it is hoped it will help promote Pembrokeshire as a destination for visitors from all over the globe.
The 186-mile Pembrokeshire Coast Path, which is part of the Wales Coast Path and International Appalachian Trail, is managed by the Pembrokeshire Coast National Park Authority with funding from Natural Resources Wales.

For more information or to view the Pembrokeshire Coast Path National Trail on Google Street View visit

 www.pembrokeshirecoast.wales/trekker.

Sunday, 26 March 2017

Poulnabrone dolmen, Ireland


Thought I'd share this -- from my one and only visit to Poulnabrone, many years ago.  Nice dolmen -- sorry about my lack of respect, for those who are appalled at such behaviour.......

Tuesday, 21 March 2017

The South Pembrokeshire LGM - again

 Reddish Devensian till exposed in the wall of the Fopston Farm drainage reservoir, near Marloes. The cemented layer, stained with manganese oxide and iron oxide, may represent the position of the Holocene water table.

South Pembrokeshire really is a tough nut to crack.  I just wish that I had been around to keep an eye on all those elongated trenches that were dug across the area when they were installing the oil and LNG pipelines between the Milford Haven installations and the English Midlands.  Much will have been revealed..........  ah well, too late now......

When I looked at all the info from West Angle Bay over the past few weeks, I was reminded forcefully that there is abundant evidence of Devensian ice pressing into the mouth of Milford Haven from the west or north-west.  Along the coast to the north there are glacial and fluvioglacial deposits at Westdale Bay,  Mullock Bridge, Fopston (801096) and Fold near Marloes.   The Geological Survey field workers identified a sheet of "boulder clay" on the western side of the Dale Peninsula, and we are familiar with the evidence of Devensian ice affecting all of the coasts of St Bride's Bay.    We have mentioned Druidston and Sleek Stone (Broad Haven) on more than one occasion.  The surveyors identified strong evidence of glaciation on both Skokholm and Skomer Islands.  HH Thomas thought that there was a considerable expanse of "yellow loamy drift" with many foreign erratics to the west of Roch -- but very few patches to the east of the castle.  Cantrill said that the sheet of boulder clay on the coast between Nolton and Druidston extends "some little way inland."  He said there are good exposures of till at Madoc's Haven and Druidston, but that the drift keeps to the top of the cliff and thins out at Druidston Villa.  He said that to the east and north of the Villa there is a "small sheet of gravel" -- could this be a pro-glacial fluvioglacial deposit, laid down just beyond a static ice front?

Another spread of till with igneous erratics is described from the Talbenny area, and there is a giant erratic near the cliff edge at Mill Haven.  Small patches of gravel and sand occur at Rickeston Bridge and in the Walwyn's Castle Valley, and the surveyors seem to have thought that there was some glacial river diversion associated with a feature called "The Rock" c 300 yds NE of Rickeston Bridge.  Might this represent the maximum inland extent of Devensian ice in the SE corner of St Bride's Bay?  This might also be supported by the presence of a "conspicuous mound" of fine yellow sand, about 200 yds in diameter, to the NW of Orlandon, about 6 km to the west; this is linked to another smaller mound, and to exposures of gravel containing much ORS material observed to be about 15 ft thick.  OT Jones thought that these deposits might be linked with the kame terrace at Mullock Bridge (which I studied intensively during my doctorate fieldwork in 1962-65).   There is another patch of gravel on the edge of the cliff west of Ripperston Farm, with rounded ORS pebbles "probably picked up on the sea bottom".

The surveyors noted various small patches of reddish-yellow boulder clay (with striated pebbles) and also gravelly patches around Milford, Thornton and St Botolph's; but from the published descriptions it appears that these patches are well weathered and eroded, and that they lie stratigraphically beneath head.  Might they be the last remnants of a pre-Devensian cover of glacial and fluvioglacial deposits?  Much fresher ice-related deposits appear around the Dale Estuary, especially on the western flank.  On the eastern side of Gann Flat, almost a metre of gravelly and sandy head is seen in the cliff; this material seems to have originated in fluvioglacial sands and gravels like those at Mullock Bridge, but there has been "paraglacial rearrangement" similar to that at Westdale Bay.

My current impression is that the ice that came in from the NW across St Bride's Bay was not very thick, and that it found it very difficult to surmount the rampart of cliffs (which were of course at that time not sea cliffs, since sea-level was around 120m lower than it is now) between Newgale and the mouth of Milford Haven.  In many places these old cliffs or steep coastal slopes were in excess of 60 m high, and in places up to 80 m above present OD.  Beneath present sea-level the coastal slope continues to drop quite sharply down to -15m along most of the southern shore of the bay -- so incoming ice had to surmount an obstacle generally between 75 m and 100 m high between Little Haven and the western end of Skomer Island.  The stretch of territory to the north of Talbenny must have been a particularly prominent obstacle.  Lobes of ice may well have pushed inland both to the east of this rampart (towards Walwyn's Castle) and to the west (towards Orlandon and Mullock Bridge).  My impression is now that all of the land to the west of the St Bride's - Dale Estuary through valley was inundated by Devensian Irish Sea ice.



 Field sketch of the exposures at Westdale Bay, as recorded by Gillian Groom in 1957.  Note the till at the base of the exposure and the pseudo-stratified materials above.

Devensian glacier ice pressed into the mouth of Milford Haven, but what happened on the west and south coasts of the Castlemartin Peninsula?  There appear to be traces of massive clay till  beneath the beach at Freshwater West, and most of the coast between Frainslake and Broad Haven (South) is difficult to examine because of the presence of the Castlemartin Firing Range. Risking life and limb (there are unexploded objects lying around), I have looked at some of  the terrain and have seen scattered erratics but no expanses of fresh till.  


Dixon and his colleagues were sure of the presence of till in a "pipe" in the limestone at Catshole Quarry, Pembroke, capped by head and other deposits.  From the published description, it appears that this may be a very old deposit.  A fresher till may be present in the St Florence and West Jordanston area, and the GS field mappers recorded a thickness of 7 ft of gravelly reddish clay, with occasional igneous erratics.  They observed till overlying the Tertiary gravels and conglomerates in the Flimston clay-pits, and remarked on the presence of scratched and facetted stones and igneous fragments as well as large angular fragments of chert.  On page 199-200 of the 1921 Pembroke and Tenby GS Memoir there are abundant references to erratic boulders, many of which are derived from the St David's Peninsula and Ramsey Island.  Sandy reddish till with igneous erratics is also recorded in a deep fissure or pipe in the NE corner of Sandtop Bay on Caldey Island -- but when I visited this bay a couple of years ago no exposure could be seen.  On the other hand, I have observed fresh till at the other end of the island, in Ballum's Bay, which has to be of Devensian Age (it rests in a Carboniferous Limestone fissure, and if it was older it would certainly be solidly cemented....




Some of the faceted and rounded erratic stones taken from the fresh till in Ballum's Bay, 
Caldey Island.

The coast between Tenby and Pendine appears not to have been affected by Devensian ice, and DQ Bowen has presented evidence from Marros to support this contention. In my own research at Marros I did not observe any till or related deposits either.

The most parsimonious explanation of the distribution of ice-related deposits on the Dale Peninsula and Castlemartin Peninsula is that there are three zones:

1.  A zone close to the cliffline and a little way inland which appears to have been affected by Devensian ice pressing onshore.

2.  A zone further inland where erratic boulders are abundant but where glacial deposits appear to be scarce, heavily weathered and eroded, and mostly restricted to interfluves.

3.  A coastal strip running from Tenby to Pendine which appears to have escaped from any direct Devensian glacial effects.

As suggested by the GS surveyors in 1921 and by JC Griffiths in 1940, the last incursion by Irish Sea Glacier appears to have been by ice that was thin and not powerful enough to overcome the coastal slope and to push far inland.  My current thinking is portrayed on the map below.  I wonder how long this map will survive before it needs to be modified?  What was I saying the other day about falsification......? 


An attempt to portray the Devensian (LGM) limit for Pembrokeshire.  The ice from the north was powerful enough to progress inland as far as Mynydd Preseli, Wolfscastle and Roch; but further south it was nowhere powerful enough to progress far inland after encountering the coastal slope / old cliffline.









Saturday, 18 March 2017

The Last Glacial Maximum (LGM) on the Isles of Scilly


I've just done this new map of the proposed LGM (Last Glacial Maximum) limit on the isles of Scilly.  The map (with grateful thanks) is from James Scourse 1991 and 1998.  The solid black line is the limit as accepted by James and most other recent researchers.  The dashed line, showing the extent of the Hell Bay Gravel, does not in my view have any significance.  My ice limit for the Devensian, based upon observations in April 2016, is shown by the red line.

The biggest changes are the tongues of ice which I believe to have penetrated along the sounds between St Martin's and Tresco and Tresco and Bryher, and a much bigger lobe that pushed in from the west across St Mary's Road right up to the west coast of St Mary's.  St Agnes was certainly affected by Devensian ice, but I am uncertain about Annet, Samson and the Eastern Isles.  Maybe somebody else can gather evidence from those, over the coming summer season.........

It's interesting that the latest dating suggests that the maximum ice extent here was around 25,000 - 23,000 years ago -- earlier than previously supposed.

Thursday, 16 March 2017

Falsification rules, OK?





Much to my surprise, one of the most popular posts on this blog is this one, featuring the very eminent Prof Danny McCarroll, with almost a thousand page views:

The joy of being falsified

https://brian-mountainman.blogspot.co.uk/2016/11/the-joy-of-being-falsified.html

Falsification is obviously popular.............

Those eminent people......





Here is another choice extract from the Darvill / Wainwright chapter in the new Pembrokeshire County History, Vol 1:

Re the bluestones transport mechanism:  "In 1971, Kellaway revived an earlier suggestion that they were carried on glaciers which spread south before they melted and neatly deposited their bluestone burden on Salisbury Plain (Kellaway 1971)."  Kellaway did not say the stones were carried "on" glaciers -- he said they were probably carried in the body of the Irish Sea Glacier which was already known to have crossed Preseli and to have flowed up the Bristol Channel at least as far as the Somerset coast and probably some way inland from there.  The addition of the word "neatly" is a nice cynical touch, but we'll let that pass........ but Kellaway was not just dreaming up some mad idea, as is implied, but was making a statement well supported by a great deal of hard evidence on the ground.

To continue:  "Superficially attractive, the glacial theory flounders because of the lack of any evidence for glacial activity on Salisbury Plain, and no suitable blocks of bluestone have yet been found along the route they would have taken across south-east Wales."   Agreed that there is no unequivocal evidence of glaciation on Salisbury Plain, unless we count the presence of a great deal of debitage from a great range of sources, and a large assortment of bluestone boulders that are clearly not pillars and clearly not quarried.  But why would we expect to find suitable blocks of bluestone scattered  along some unknown route across south-east Wales?  Even if there really was a route (which there wasn't), and even if we know it (which we don't), why would we expect to find suitable lumps of bluestone along it?  Suitable for what?  I really don't know what the authors are talking about. I should have thought that a lack of dropped blocks along some hypothetical route would militate against a human transport hypothesis, and be completely irrelevant as far as the glacial transport hypothesis is concerned.

To continue:  "Although it still has vocal supporters, eminent geologists and glaciologists have dismissed the glacial theory (Bowen 2005; Green 1997; Scourse 1997) and concur with Thomas's original suggestion that the stones "were transported by human agency, in all probability by an overland route (Thomas, 1923, 259)."  So who are these eminent geologists and glaciologists?  David Bowen, Chris Green and James Scourse are not geologists and they are not glaciologists; they are geomorphologists, no more brilliant or eminent than those of us who believe that the glacial transport hypothesis is eminently reasonable.  I don't actually care very much about Messrs Bowen, Green and Scourse concurring with HH Thomas -- and I have argued many times on this blog that their arguments are deeply flawed.  I place much greater value on other papers (written by assorted specialists including real glaciologists) who have argued that the glacial transport hypothesis is a perfectly reasonable one.

It would have been helpful if Darvill and Wainwright had done some more careful research on this issue before going into print here and repeating the same points they have made many times before.......

If "lack of evidence" is the sticking point with respect to the glacial transport thesis, would somebody please present to me the evidence thus far accumulated which shows that human transport of the bluestones might have happened?  I wait breathlessly for a flood of responses.


Wednesday, 15 March 2017

Pembrokeshire megalithic culture and the erratic supply chain


 Carreg Samson, an erratic architectural statement.........

I have been reading the huge chapter (167 pp) by Tim Darvill and Geoff Wainwright in Volume 1 of the Pembrokeshire County History.  That chapter is almost a book in its own right, superbly illustrated and nicely laid out -- and packed with detail.  I'll leave a more considered review till a little later, since I still haven't quite finished the text.  But as I suspected, it really could have done with proper peer review (including scrutiny from the geologists!) and with some effective editing and pruning.......

But the thing that really strikes me, having now read the bulk of the text that deals with stones (monoliths, standing stones, stone circles, cromlechs, tools, weapons, etc) is the extraordinary lengths that the authors go to in order to avoid stating the obvious -- namely that the users of stone in the Mesolithic, Neolithic and Bronze Age were operating in a landscape littered with stone blocks or glacial erratics.  There is a mention somewhere of glacial till spread across the landscape, but I have only seen two fleeting mentions of glacial erratics in more than a hundred pages of analytical text.  This is quite extraordinary, given that the authors were perfectly familiar with my work on the glaciation of Pembrokeshire and with the work of Kellaway, Richard Thorpe, Olwen Williams-Thorpe and others:

https://brian-mountainman.blogspot.co.uk/2016/11/one-of-classic-stonehenge-papers.html

Even archaeologist Steve Burrow, in his book called "The Tomb Builders", argues that all of the cromlechs in Wales were simply built from glacial erratics or from loose bedrock slabs collected in the immediate vicinity:

http://brian-mountainman.blogspot.co.uk/2011/01/inside-neolithic-mind.html

http://brian-mountainman.blogspot.co.uk/2016/01/neolithic-bluestone-quarries-why-would.html

The authors of this big chapter discuss literally hundreds of megalithic structures in Pembrokeshire, and not one of them was built of stones transported from anywhere else by the builders.  Where there were glacial erratics, they used them by levering them up, wedging them and propping them, or sliding them into sockets.   They arranged them by lining them up or moving them into circles or ovals.  But in no case can it be shown that big stones have been moved a kilometre or more from a place or origin to a place of use.  Small stones were gathered from a radius of 100m or more in some instances, but I know of no large stone weighing a tonne or more being moved even 50m.  In fact, I would argue that we can forget about astronomical alignments, spring head locations, ley lines, auspicious positions and pretty views in the matter of monolith placements -- stone location was the prime determinant in deciding where the Pembrokeshire monoliths were put into the ground.

So why have Darvill and Wainwright apparently existed in a state of denial about this perfectly simple matter?  Well, we don't have to search too far for reasons.  For a start, one of their central theses is that big stones of particular lithologies (especially spotted dolerite) were inherently valuable, either because of their supposed healing properties (TD and GW) or because they were deemed to contain within them the spirits of the ancestors (MPP).  So if they were valuable, they had to be worth fetching and carrying.  That means they had to be worth quarrying.  And it also means they had to be worth carting all the way from Pembrokeshire to Stonehenge. So the Darvill / Wainwright text is full of references to quarrying, stone transport, stone veneration and so forth, as fantasy is built on fantasy.  What is completely lacking is evidence that withstands scrutiny.

So let's repeat the following points.

1.  There are abundant assertions, but there is no hard evidence in this long text of  any particular stone type being valued, or being accorded veneration, over and above any other stone type in prehistoric Pembrokeshire.  Stones of all lithologies, shapes and sizes were used wherever it was handy to use them. (That, by the way, is exactly the case at Stonehenge as well.)  If more spotted dolerite pillars and slabs appear to have been used in north Pembrokeshire, it is because there were simply more of them lying around as glacial erratics.

2.  There is no hard evidence, as far as I know, of any large stone in a Pembrokeshire monolithic setting being transported more than a few metres from its place of origin to its place of use.

3.  Because of the abundance of glacial erratics littered across the landscape, there was no need for any quarrying of stone from "bluestone quarries."  So there are no bluestone quarries, and the obsession with searching for them and "finding" them them is nothing more than a rather charming fantasy.

4.   Although I am a geographer who quite enjoys looking for patterns and arrangements in the landscape, I can see no "siting preferences" with respect to monolithic settings based on proximity to springs, views of the mountains or the sea, alignments, transition zones between boggy and and rocky land, or anything else.  The only thing I would concede is that some fortified sites and burial sites are located on hill summits.

5.  Through frequent mentions of other parts of Wales, the Irish Sea arena and Ireland, this chapter reinforces my view that the cultural associations in Mesolithic, Neolithic and early Bronze Age times were predominantly with other parts of the "Atlantic Fringe" and NOT with Salisbury Plain and the Stonehenge area.  There does not seem to be any cultural context for a situation in which people would suddenly want to start gathering up 80 bluestones and carting them off to Stonehenge.

6.  I know it's unromantic and unfashionable to say so, but I think that the prehistoric inhabitants of Pembrokeshire were a pretty pragmatic bunch.  They clearly had their reasons for making "statements" in stone, but they were also driven by utilitarian principles, and always used whichever handy stones were fit for purpose.  They may have been simple folk, but they were smart enough to know about cost / benefit analysis. 

Sunday, 12 March 2017

Prof Geoff Wainwright


I was sad to hear of the death of Prof Geoff Wainwright on 6th March 2017.  He had been seriously ill for some time.  Sincere condolences to his family.

This is a photo taken on the summit of Carningli, just a couple of weeks before he died.

Friday, 10 March 2017

Cilgwyn Cromlech


The photo above shows the site of the Cilgwyn Cromlech, according to the grid reference cited in the "Neolithic and Bronze Age Pembrokeshire" chapter in Vol 1 of the new County History.  The grid ref is SN 088362.   The site is due west of the southernmost of the rocks of Carnedd Meibion Owen.   There doesn't seem to be anything there -- so we must assume that it has been destroyed.

Thanks to Mark for drawing this to my attention.

On p 108 of the chapter, we see a pestle macehead made of 'preselite" (Group Xlll) from the late third and early second millennium BC -- apparently collected from a site c 100m east of the cromlech, in the ploughed field next door.  The reference is Burrow 2003, p 229 -- that's a catalogue of collections in the National Museum.

There is no Coflein record for this site.

Thursday, 9 March 2017

Trellyffaint -- a good place for strange tales



Since we are talking about Trellyffaint and strange tales, here is a gentle reminder of the most famous tale from that locality-- told originally by Giraldus Cambrensis almost a thousand years ago:

Once upon a time, a strange young fellow called Cecil Longshanks lived at Trellyffaint, not far from Nevern.  He was frightened by lots of different things, and he was especially scared of toads, because they were black and had warts on their skin and moved very slowly.  He thought that they were poisonous and that they lived for hundreds of years.......    One day Cecil fell ill, and straight away toads started to move into his house.  At first there were just a few, and then there were scores of them, and then hundreds, and then thousands.  Nobody had ever seen such a pestilence.  Cecil was angry, and his friends gathered up the toads and threw them out of the house, but they kept on coming and after a few days they were everywhere, in the cupboards, all over the kitchen floor, and under the beds and tables.  By now Cecil was terrified, and became quite certain that the toads were intent on eating him up.  His friends did not know what to do, and in the end Cecil pleaded with them to put him inside a big leather bag, and to hang the bag by a rope from a tall tree in the yard.  They all thought that was a very strange request, but they did as they were asked, and when it got dark they all went home, leaving Cecil fast asleep in the bag, hanging from the tree.  In the morning they returned, planning to take Cecil down and give him some breakfast.  But what did they find?  They found that the toads had climbed the tree and eaten every single leaf and most of the bark as well.  And hanging from a branch of the tree was a leather bag full of white bones, which rattled as the bag swung back and forth in the warm summer breeze.  

By the way, Trellyffaint means "Toad Hall" --- in the vicinity there is much wind but not many willows.

Tuesday, 7 March 2017

Yet another proto-proto Stonehenge -- well, sort of........



 Trellyffaint collapsed cromlech.  Image: Paul Call

Oh dear --here we go again.  Yet another university press release which cannot resist talking up the latest piece of archaeological research in Pembs.  This time the object of attention is the collapsed cromlech of Trellyffaint, not far from Newport, which has been examined by George Nash and his colleagues, who are rather keen on cup marks and other markings on monoliths.  In their investigations they have found traces of "circular anomalies" and other sub-surface features -- and on the basis of this rather flimsy evidence they immediately start talking about "....a complex ritualised landscape that includes the precursor to a Stonehenge-type earthwork monument."  Hang on a bit, chaps, that's a bit rich, if I may say so...........   does everything circular have to be connected in some way to Stonehenge?  Isn't it just as likely to be structurally related to a circle of magic mushrooms?

Even if there are "buried anomalies" including alignments and circular patterns,  it seems to me entirely reasonable to assume that those might be related to other Neolithic / Bronze Age enclosures, walls and causeways (such as those at Rhos y Clegyr, Clegyr Boia or even Carningli) rather than making a gigantic leap of faith and assuming some sort of link with Stonehenge.

Anyway, let's see what transpires.  Apparently there will be a good number of people digging at Trellyffaint in late April.

 ===================

Complex prehistoric patterns discovered around site of ancient Welsh burial chamber

Press release issued: 24 February 2017
http://www.bristol.ac.uk/news/2017/february/trellyffaint.html

A team of archaeologists, led by a researcher from the University of Bristol, has uncovered the remains of a possible Stonehenge-type prehistoric earthwork monument in a field in Pembrokeshire.

Members of the Welsh Rock art Organisation have been investigating the area around the Neolithic burial chamber known as Trellyffaint – one of a handful of sites in western Britain that has examples of prehistoric rock art.

The site of Trellyffaint dates back at least 6,000 years and has been designated a Scheduled Monument. It is in the care of Welsh heritage agency Cadw.

The site comprises two stone chambers – one of which is relatively intact. Each chamber is set within the remains of an earthen cairn or mound which, due to ploughing regimes over the centuries, have been slowly uncovered.

On the capstone that covers the south-eastern chamber are at least 50 engraved cupmarks (one of the most common forms of later prehistoric engraving in Western Europe), the meaning of which has been long forgotten but probably represented some sort of pictorial message.

Before now, it is thought that the site has never been fully investigated.

Dr George Nash, lead project director from the Department of Archaeology and Anthropology at the University of Bristol and his team, which includes former Bristol students, have conducted a series of non-intrusive surveys in and around the monument.

The fieldwork element of the project started in December 2016 following the acceptance of a project design by Cadw.

This phase included a magnetometry study which covered 80 square metres around the monument and a detailed earthwork survey of the monument itself.

The geophysical survey uncovered a number of anomalies which are considered to be more than likely buried prehistoric features.

Dr Nash said: "To the south and southwest of the stone chamber and appearing to run underneath the southern section of the Trellyffaint mound are two clear circular anomalies.

"It is regarded that this feature may possibly be a henge (otherwise referred to as a hengiform) measuring around 12 metres in diameter.

"It is not clear if this feature possesses an accompanying ditch, however, a circular anomaly extends around this feature, again we are unclear of the relationship (if any) with the smaller circle – only excavation will tell."

Further subsurface features of a probable later prehistoric date occur to the north-east, north and west of the Trellyffaint monument.

Although the precise depth of these features is, for the moment unknown, the team were interested to note that 2-3000-years’ worth of accumulated soil has not created any visible earthworks. This phenomenon though is not uncommon in coastal areas where soil deposition and accumulation can be rapid.

Dr Nash added: "This site, one of only nine Neolithic burial-ritual monuments in Wales with prehistoric rock art - or what I would term aptly 'a visual communication system'."

So far, the results of the geophysical survey have yielded a set of subsurface anomalies that reveal a complex ritualised landscape that includes the precursor to a Stonehenge-type earthwork monument and is similar to the six or more features that were found using similar geo-prospection methods at the nearby Neolithic site, Trefael, in 2012.

Dr Nash said: "The next stage of the project is to apply for Scheduled Monument Consent (SMC) which will include targeted excavation over recognised anomalies identified from the magnetometry survey.

"Before we do this, we will be widening the geophysics area and apply resistivity as well further magnetometry over a wider area."

This fieldwork will take place between April 21 and 23. For details on how to get involved, visit the Welsh Rock Art Organisation’s Facebook page.

West Angle Gallery


The southern end of the West Angle Bay section.  The undisturbed sediments of the interglacial silt and clay series are now lost beneath the thick vegetation right of centre in the photo.  The prominent exposure in the centre of the image shows dark red Devensian till.  The erosional contact between this till and the older silts and clays is no longer visible. 




The famous "swells" in the Main Limestone exposed in the centre of the second north cove at West Angle.  There are several beautifully exposed small synclines and anticlines. (These pics are for geologists who are bored by Pleistocene sediments.  We try to keep everybody happy.....)

Monday, 6 March 2017

West Angle Bay -- the classic coastal section -- going, going, and almost gone.......


I went down to West Angle Bay today, to see how it might have changed since my last visit.  Sadly (since this is one of the classic British Pleistocene localities) marine erosion has been doing its work, and I suspect that within the next five years the last remnants of the "rampart" between the coast and the old clay-pit will be whittled away, leaving a mess of brambles, scrub and made ground.  Once that happens, bits and pieces of the sediment sequence will still be visible, but it will be very hard indeed to work out what the Pleistocene history actually is.  I estimate that the coast has retreated about 10m since I first researched this site in 1965.

Parts of the old clay-pit are already visible, in a 30m stretch at the southern end of the section, and in the middle of the section to the north of a prominent "plug" of reddish Irish Sea till (seen in the photo above with a "cap" of dark green vegetation).

The "plug" of dark red gravelly Irish Sea till, approximately in the centre of the current exposure.  To the left we can see the breach which has exposed the floor of the old clay-pit.  At this point the silt and clay series of Ipswichian sediments have been cut out by overriding and eroding ice flowing in from the north-west.

The left edge of the above photo is approx at position D on my original surveyed profile of the cliff exposure of the 1960's.   For the next 20m northwards, the cliff exposure has been completely transformed, and there has been large-scale sediment removal.    What we now see is a "melange" of dark red till and exposures of black, blue-grey and orange-coloured silts and clays.  As glacier ice has come in from the north-west it is clear that it has over-ridden the fine-grained interglacial sediments and incorporated plugs or rafts of it into the dark red gravelly till. This is one of the smaller rafts, about 1m long, with dark red till above and beneath it:


About 10m further north, we see an exposure where interglacial silts and clays apparently overlie the dark red till, as in this photo:


The dark red till is full of Devonian sandstone erratics which have probably not travelled very far.  The interglacial clay is in the top right corner of the photo.

A further 5 m north we see this -- an almost vertical contact between dark red or black clay to the north (left) and dark red Irish Sea till to the south (right):


There has clearly been shearing, thrusting and sediment incorporation into basal ice layers on a substantial scale, and it appears that some "rafts" of over-ridden sediment are in excess of 10m long and 4m thick.

Then again we see this -- a layer-cake effect, with two slabs of blackish clay separated by layers of gravelly dark red till:


Again, till is seen beneath members of the silt and clay series.  Note that the till colour in this photo has been masked by a brownish-grey layer of sediment-rich water flowing down the cliff face.

There is now no doubt in my mind that glacier tectonics have played a vary significant role in determining the appearance of this cliff face of 2017 --  and probably all earlier exposures, all the way back to 1916.  The presence of large rafts of interglacial silt and clay sediments have confused some researchers (including Leach, Dixon, Bowen and Morey) who observed silts and clays ABOVE dark red till and who erroneously concluded that the till was of pre-Ipswichian age.  A mistake easily made.............

The northernmost part of the drift cliff of 2017 shows an exposure of a low rock platform and a cliff face about 30 m long and 3 m high exposing severely rotted Lower Limestone Shales  (occasionally reduced to a clay-like consistency) capped by patchy dark red till and silty soil and made ground:

The northern part of the West Angle coastal section, showing the low raised beach platform cut across Lower Limestone Shales, rotten bedrock in the cliff face and a thin cap of dark red till.

 I cannot for the life of me understand why anybody should doubt that the dark red till at West Angle is actually a till, and actually Devensian in age. There are many exposures of it in this cliff face.  Some are shown above, and here is another:


To the north of the main beach at West Angle, the same red till is seen in the three coves greatly beloved of geologists looking at structures in the Carboniferous Limestone.  Dixon refers to this one in Cove No 2 as a "pipe of drift":


In the above photo a "plug" of dark red Devensian till is exposed in the cliff face.  It is about 12 m long and 4m thick, and rests on rotted bedrock, silts and clays.  The till is capped by colluvium which has moved downslope from the higher land near West Pill Farm.  This colluvium occupies the same position as the "Upper Head" elsewhere around the Pembrokeshire coast.
 

Conclusions

My observations today have confirmed the essential correctness of my conclusions in the three earlier posts, namely that:

1.  The interglacial silts and clays (of various colours) are all older than the dark red till exposed in the cliff face.

2.  The till is quite fresh, containing striated pebbles of Old Red Sandstone and also igneous erratics presumably from the St David's area.  Some of these erratics are over 50 cms in diameter.

3.  In the middle part of the section there are clear erosional contacts / unconformities which show that substantial amounts of older fine-grained sediments have been sheared away from their places of origin and incorporated into the glacial deposits as slabs or rafts.  The scale of glacial tectonic activity is clearer now than it has been in the past.

4.  There is no reason to believe that any till exists here beneath the Ipswichian interglacial sediments.

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

Here is an oblique aerial shot of the sediment cliff, taken in summertime.  Maybe a year or two old?  The main features as seen today are all present. Click to enlarge.


Saturday, 4 March 2017

The West Angle Enigma (3): two tills, or one?

 As indicated in the first post on West Angle, there is a considerable dispute about whether there is one till, or two, at West Angle.  In my own work, in spite of extensive excavations using a JCB and several drill-holes in the vicinity of the old brick-pit, no trace was found of a "basal till" underneath the raised beach cobbles and gravels.  Even in summer, waterlogging in the sandy layer beneath the beach frustrated attempts to expose any deeper sediments.  David Unwin also failed to see anything beneath these sands.

D.Q.Bowen


On the other hand, DQ Bowen has asserted, on many occasions, that he has encountered this basal till.  In the Quaternary of Wales GCR volume, edited by Campbell and Bowen, there are no less than eight DQB references cited in support of this assertion, including these which appear to be the "primary" references:

BOWEN, D. Q. (1973a) The Pleistocene history of Wales and the border-land. Geol. J. 8, 207­224.
BOWEN, D. Q. (1973b) The Pleistocene succession of the Irish Sea. Proc. Geol. Ass. 84, 249­272.
BOWEN, D. Q. (1974) The Quaternary of Wales. Chapter 17 in T. R. Owen (Editor), The Upper Palaeozoic and post-Palaeozoic rocks of Wales. Cardiff. 373-426.

But as I recall not one of them actually contains the detailed stratigraphic and other field evidence that we need to see.  Each one of the articles cited makes the same assertion, and cites lots of other DQB articles,  but fails to show us the evidence.  In 1977 Bowen promised an article by "Ribbon and Bowen et al" arising from work in progress, but as far as I can see this was never published.

So my default position has to be that Bowen and his colleagues saw a stony grey Irish Sea till at West Angle ABOVE the raised beach, and mistakenly assumed it to have been stratigraphically lower. The reason for this can be seen in this part of my surveyed section:

The critical cutting here is numbered B.  At this point a "classic" Irish Sea till is exposed, reddish in colour, with many ORS clasts and other striated cobbles included -- and even lignite and shell fragments.  There are thrust structures in the underlying sediments.  As we can see, no raised beach can be seen in the vicinity, and we can see from the adjacent cutting C that the raised beach there is at a very low altitude -- only at about 2m OD.  It may therefore dip northwards and disappear somewhere between cuttings B and C.  Because the exposed Irish Sea till in the gully is at a relatively low altitude (just over 5 m OD) Bowen might have assumed that the raised beach was above the till, since the raised beach is indeed at about this level in cutting H.

Another possibility is that Bowen identified raised beach cobbles in the sediments above the till and mistakenly interpreted this finding.  Where ice moves inshore across an old coastline it incorporates older sediments -- including raised beach cobbles -- which are then redeposited in lodgement till or in flowtill or fluvioglacial gravels.  We see evidence of this in the Isles of Scilly, and also in other coastal districts of West Wales. 

If I am wrong, and if Bowen has indeed observed raised beach deposits above his supposed lower till, I will be very happy to publish the evidence and revise this opinion.  If any reader is in possession of such evidence, please get in touch.

E.E.L. Dixon


So we are left with the evidence from Leach and Dixon, collected in the early 1900's.  Now it gets even more interesting.  This is the original source:

The geology of the south Wales coalfield. Part XIII, the country around Pembroke and Tenby, being an account of the region comprised in sheets 244 and 245
Author: E E L Dixon; Geological Survey of Great Britain
London : H.M.S.O., 1921.
Series: Memoirs of the Geological Survey of Great Britain. England and Wales.
Chapter 14, pp 189-203

 This original source has been cited, over and again, by Bowen and other researchers in support of the assertion that there is Irish Sea till BENEATH the raised beach at West Angle, and that this was seen by both Leach and Dixon prior to the publication of the Memoir in 1921.  But when you go back to source, as I did last night, you see that this is nothing better than a myth.  Geologists and geomorphologists are just as susceptible to mythology as archaeologists are!

A careful reading of the Memoir chapter reveals the following:

1.  In his introductory remarks Dixon says: "Stiff "till" has been found only at West Angle Bay.  It is overlain by gravels and loams with drifted plant-remains, which may include a representative of the raised beach....." (p 195)  It is true that the till is at a low level in the northern part of the section and that silts with plant remains are at a higher level in the southern part of the section -- but that does not mean that the latter are stratigraphically higher than the former.  The till lies in a gully or channel cut into older sediments.

2.  On page 197 Dixon says that he looked at the drift cliff section in the company of Arthur Leach and that they could not decide which gravels were of glacial origin and which were related to the raised beach.  Quote:  "No agreement was reached, however, as to which, if any, of the beds might be taken as a representative of the raised beach." (p 197).  It is clear that the two did not undertake any excavations, and that they simply tried to sort out the stratigraphy from glimpses of it here and there -- since the bulk of the section then, as now, was obscured by slumping.  I think that like David Bowen, they were misled by the presence of glacially recycled raised beach cobbles in the glacial suite of sediments.

3.  Dixon says (p 198) that the boulder clay was seen in just one location, "in the bottom of the cliff".

4.  It is also clear that he and Leach did not see the genuine raised beach at all, since it is at or below the level of the current pebble beach and is only very rarely exposed.  If they had seen it, they would have recognized it immediately, since it is very different in appearance from all of the other gravelly deposits in the West Angle sequence.

The main drift cliff exposure as described by Dixon is as follows:

7.  Shingle of limestone pebbles - less than 1 ft (modern)
6.  Gravel and sand - 6 ft
5.  Buff fine loam -- up to 2 ft
4.  Grey fine loam with plant remains - more than 5 ft thick but thins northwards
3.  Gravel and shingle, up to 4 ft, thins northwards
2.  Sand, up to 3 ft, thins northwards
1.  Boulder clay with scratched stones (including igneous), in stiff purplish clay, 6 ft max
x.  Black clay with debris of silicified Carb shells, at least 5 ft

Dixon says that the loams are "cut out for some distance by the overlying gravel, which appears to fill a channel in them", so it is clear that he did see the same slip face / erosional contact as others have seen half a century later:



To the north of this point, Dixon also describes a sequence in the cliff face, as follows:

Stony soil, some pebbles
Buff loam with weathered bedrock debris (= 5 above) - 5 ft
Grey loam, with stony sand below (= 4 above) - 2 ft
Current-bedded buff sand up to 1.5 ft thick
Coarse gravel, stones, some well-rounded, of all sizes, including igneous rocks, sandy matrix - up to 1 ft
Lower limestone shales, forming a platform c 13 ft above HWM

This is very confusing, since there is no high rock platform at the northern end of the drift cliff -- and I think that Dixon is  interpolating or trying to make sense of a complex situation.

Inside the brick-pit, Dixon found the following sequence (p 197):

8.  Angular stony loam - head?  3 ft
7.  Sand with abundant rounded bedrock flakes (?!!) plus erratics (including one from N Pembs) -- 4 ft
6.  Well bedded gravel and sand -- 2 ft
5.  Buff laminated loam including erratics -- 5 ft
4.  Dark blue loamy clay with wood and plant fragments -- 5 ft
3.  Irregular loam, sand and fine gravel  - 3 ft
2.  Grey clay or loam -- 1.5 ft
1.  Clean buff sand -- 1 ft

Conclusions


Dixon's recorded sequence has been mis-reported by Bowen and others, and it is now apparent that the gully or channel which was cut into the sequence of interglacial silts and clays at West Angle, and its filling by periglacial, glacial and fluvioglacial deposits, has caused great confusion about the stratigraphy both inside the clay-pit and on the cliff section facing the beach.  Old and new deposits are not exactly inverted, but to the south of the gully it appears that Ipswichian interglacial silts and clays (probably more than 70,000 years old) are found about 8 m above OD while Late Devensian glacial deposits (around 20,000 years old) are found  below 5 m OD to the north of point E in my surveyed section.  We do not know how this gully was formed;  but I suspect that a substantial quantity of pre-existing sediments (including raised beach cobbles and shingle) were removed by the ice of the Devensian Irish Sea Glacier as it moved onshore from the NW, and that these sediments were incorporated into the rather complex reddish "gully fill" deposits that we see today in the northern part of the cliff section.

So my conclusion is this.  Much as I would love to see a pre-Ipswichian Irish Sea till at West Angle, I don't think Dixon and Leach saw one, and neither did David Unwin or myself.  Neither, I suspect, did David Bowen and his colleagues -- which might explain why the promised paper by Ribbon and Bowen never did appear in print.

So -- there is just one set of glacial deposits at West Angle, associated (like all the others around the coasts of Pembrokeshire) with the Late Devensian glaciation.


The outer (northern) end of the drift cliff at West Angle.  Here, overriding ice has removed the bulk of the interglacial sediments, and the bulk of the sediments exposed in the cliff face are related to the Devensian glaciation.  The raised beach is at considerable depth, or is absent.  The best exposures of Irish Sea till occur around point B.


The middle part of the surveyed section.  At E we can see the slip face / slump face / erosional contact, to the left (north) of which the bulk of interglacial sediments have been cut out.  At D the bulk of materials exposed are glacially related.  Between F and H the bulk of the exposed sediments are fine-grained interglacial silts and clays overlying the raised beach.



The southern part of the surveyed section, extending northwards from the bedrock slope.  The bulk of the deposits exposed are interglacial, resting on the raised beach.  Around J and K glacially-related materials sit on these deposits at the top of the section.


Friday, 3 March 2017

Paul's Myth-making machine goes into overdrive


 Castell Mawr, not far from Felindre Farchog -- the Welsh Stonehenge, and the Mecca of Mesolithic Wales?  Hmm -- maybe not......


What should one do when one knows something about something, and somebody else goes into overdrive in the promotion of what is, to put it mildly, somewhat unreliable?  Keep a dignified silence?  Look the other way?  It's a bit of a dilemma when somebody gives three talks in rapid succession in the community, and then writes two articles in a widely circulating magazine, leading to all sorts of people saying to me "Did you know that the Welsh Stonehenge has been discovered?"

I groan inwardly and suppose that I have to respond, just to protect the community of people who are interested in Stonehenge but who do not necessarily know much of the detail.

Paul Sanday, of whom In have written before, is hoofing about giving his talks, and in this month's Pembrokeshire Life Magazine he has an article called "The Day I found the Welsh Stonehenge".  Paul calls himself a geologist, and I leave it to other geologists to assess his credentials.  Where are you, Myris?

Anyway, I'll try to be quick. Paul's starting premise seems to be that there is some sort of conspiracy to keep the truth hidden away, and he argues that there are in the north Pembrokeshire area "three hidden things." This is all rather in the style of the Welsh Triads -- you know how it goes -- involving the three immortal drunkards of Wales, the three wise birds, the three one-legged heroes and so forth.  Is there a triad celebrating the three jolly geologists, I wonder?

The first hidden truth, according to Paul, is that the rectangular bluestone numbered 36 at Stonehenge (the one with the mortise holes) was actually shaped and used originally in a bluestone trilithon in the Welsh Stonehenge and then reburied at Stonehenge by Atkinson to keep it from public view.  Oh, dastardly deed!  The second hidden truth is that the Welsh Stonehenge is actually at Castell Mawr, near Castell Henllys, which we have discussed many times on this blog.  Paul describes breathlessly  the manner in which he and his dog "stumbled upon it", apparently quite ignorant of its size and characteristics and unaware of the fact that it is perfectly obvious on Google Earth imagery, heavily studied and perfectly well described in the literature.......  Paul says he went hunting for it, and found it in more or less the "right" place in relation to the position of the "mines" used for the extraction of dolerite, spotted dolerite and unspotted dolerite monoliths.  Amazing!  And the third hidden truth is a pillar of spotted dolerite which he found in a hedge somewhere between the Welsh Stonehenge and the spotted dolerite "mine".  Apparently Paul has failed to notice that there are hundreds of spotted dolerite gateposts and monoliths scattered across the countryside of north Pembrokeshire, perfectly visible for all to see.  Chris and I visited and photographed just a few of them a few months ago, and I put some photos onto the blog.

Other things?  Where do I start and stop? Paul reproduces in his article something referred to as an "early plan" of Stonehenge, rather in the style of rough sketch map leading treasure seekers to a chest of gold coins on Treasure Island.  Actually it is not an early plan at all -- it is certainly not a copy of the John Wood plan of 1740, and since it has the Petrie numbering system on it, and refers to "blue stones" and "sarsens" it must be rather recent!  Is it a map made for a school project by some enthusiastic young person?

Paul refers to the "River Avon bluestone circle" as if it is established fact.  As we know, it is nothing but speculation, with no evidence for any bluestone use close to the river.  Paul refers to the arrival at Stonehenge of 75 bluestone "uprights" around 2800 yrs BC, and clearly thinks that at some stage thereafter the monument was "immaculate", with all assumed sarsens and bluestones tidily in place.  As we all know, that is nothing but an assumption.

Paul refers to a "rhyolite mine" identified by geologists Ixer and Bevins at Rhosyfelin, and "spotted dolerite mines" at Carn Menyn, Carn Goedog and Cerrigmarchogion.  If he has ever visited any of these places, he will know that there are not even quarries to be seen, let alone mines.  There is a photo accompanying the article which Paul claims to have been taken at a "rhyolite outcrop below Carn Goedog" -- but it sure wasn't taken anywhere near Carn Goedog, since there is a well-wooded slope in the background.

On referring to previous visits to the "Welsh Stonehenge" site at Castell Mawr, Paul reports that over the past few years one archaeologist, one archaeoastrologer and one astronomer had visited it.  Is it really possible for anybody in this neighbourhood to NOT know that the MPP team was digging there in 2012, and that they found nothing of any value?  They looked for stone sockets but failed to find any.   Does he not know that Mytum and Webster have described the site in detail?  There has been speculation that there might be a henge monument buried beneath the Iron Age defensive features, but there is no evidence (as far as I know) in support of this idea.

Paul claims that the amount of rock excavated from the ditch at Castell Mawr is exactly the same as the amount of rock excavated from the Stonehenge ditch; apparently he has "developed a formula" for doing the calculation........  The fact that the Stonehenge ditch was cut around 5,000 years ago and the Castell Mawr ditch was cut during the Iron Age (around 3,500 years later) is apparently immaterial.  In fact, Paul thinks all the dating is wrong, anyway.  In his view the Welsh Stonehenge was built at Castell Mawr in the Mesolithic, and that this all had something to do "changing sexual relationships between men and women......"  The mind boggles.

Now Paul is thinking of starting a Kickstarter campaign to raise £10,000 so that he can protect and preserve Castell Mawr and open it to the public with an attached research centre for "like-minded people".......

He claims that Prof Geoff Wainwright has given him great support and encouragement -- I am not sure that I believe that!

Oh dear -- I think I need to lie down in a darkened room for a while.

Thursday, 2 March 2017

Pembrokeshire County History, Vol 1


This volume, which has been in the pipeline for at least 20years, is at last published, and I have my copy.  It's not cheap, at £35 per copy, but it is beautifully presented on glossy paper, with abundant illustrations (many of them in colour) and 552 pages.

Volumes 2, 3 and 4 of the series were published some time ago, and the only volume to come is the Atlas, for which I have been asked to contribute four maps.  This volume deals with Prehistoric, Roman and Early Medieval Pembrokeshire.  It's been written by Tim Darvill, Heather James, Ken Murphy, Geoff Wainwright and Elizabeth Walker, and four of those are also the editors.  I always get rather worried about books published in this rather incestuous fashion, with contributors in effect doing their own editing.  There are lots of acknowledgements on the back of each chapter, of course, but this does not disguise the fact that books like this can go into print without any effective peer-review and with all sorts of biases built into them.

Anyway, I won't presume to do reviews of the chapters concerning the Iron Age, Roman period or early Medieval Pembs -- but I will do a review of the chapter called "Neolithic and Bronze Age Pembrokeshire" by Tim Darvill and Geoff Wainwright.  As ever, of course, I will subject it to careful scrutiny and will be scrupulously fair at all times.  Now I must get down to some serious reading..........

Wednesday, 1 March 2017

The West Angle Enigma (2): the silt and clay series


 West Angle Bay, near the mouth of Milford Haven.  The main exposure is at the back of the beach, between the car park and the sharp bend in the cliffline near the bottom edge of the photo.  The position of the old brick pit is now very difficult to discern from the air.

The "ridge" of interglacial and glacial sediments exposed in the southern part of West Angle Bay.  The beach is to the left and the brick-pit is to the right.


The sands, silts and clays which overlie the raised beach at West Angle, and which lie beneath the reddish till, are so unusual that they have caused intense (and sometimes acrimonious!) debate among geomorphologists and geologists.  Dixon (1921) referred to them as "loams" but that term is misleading since it is conventionally used for a sandy or silty soil, which implies a period of subaerial evolution beneath a plant cover.  There is certainly some evidence (in the form of a peat bed) of vegetation accumulating and growing -- but it would be a mistake to simply assume that all of the sediments in this sequence were accumulating at the ground surface.  They are very fine-grained, and many researchers have concluded that some of sediment accumulation was beneath water, either in a lacustrine, marshy or estuarine environment. So let's simply refer to this sequence of quite variable sediments as the "silt and clay series".

First, the base of the series.  According to my observations, and those of David Unwin, there are ferruginous cross-bedded sands and gravels above the raised beach.  These are generally less than 1 m thick, but Unwin interpreted them as "dune sands" and I am now inclined to agree with him.  (I originally thought that they might be beach sands laid down on top of the pebble beach during the course of a marine transgression, but I now think that evidence in support of this hypothesis is in short supply.......)  Another interesting fact is that stony grey silts up to 40 cms thick seem to be associated with these sands and with the upper part of the raised beach facies.  This suggests that at the end of the raised beach episode (the Ipswichian interglacial?) sea-level might have dropped slightly, or else there was some other environmental change.  This led to the accumulation of slope deposits or rockfall materials and pre-existing sediments on the valley side, with colluviation extending as much as 30 m from the valley side out onto the valley floor.  Possibly a sand dune system developed on top of the raised beach with a dune slack behind it.  Colluvial materials (incorporating angular rock fragments and also raised beach pebbles and shingle) were then interdigitated with sandy dune materials and with peats, silts and clays in a freshwater environment.


Two examples of flooded dune slacks in England.  In each case, the wetland is trapped behind a sand dune belt at the back of the shoreline.  In West Angle the dry valley has probably existed for hundreds of thousands of years, so without a river to breach the dune belt there are perfect conditions for semi-permanent lakes to exist during interglacial periods, so long as the water table remains high.  There may well have been intermittent tree cover -- this is suggested by the pollen and plant remains in the sediments.
The exposed section at point H, about 25 m away from the rocky valley side at West Angle. Here the top of the raised beach is slightly above the level of the present-day pebble beach.  Above it there is a layer of ferruginous cross-bedded sand, then a thin gravel layer, and then about 30 cms of grey colluvium with angular fragments, and then a peat layer shown with cross-hatching. This has a maximum thickness of c 45 cms.  Above that is the grey silt and clay series, followed by the orange silt and clay series.  At this point the reddish till, sands and gravels are not represented.

Now to the peat and peaty silt layer.  Since this was first discovered it has caused great excitement, since interglacial peat beds in Wales are exceedingly rare.  It has always been assumed that it is linked in some way with the raised beach and with the silt and clay series, which also contains abundant plant remains.

 A more detailed section near cutting H, transposed from a photograph.  The main stratigraphic junctions are shown, together with the peaty silt and peat layer.

 The Silt and Clay Series.  Fragments of well-preserved oakwood, rootlets and leaves are found here and there, and Dixon (1921) referred to "plant fragments and occasional large pieces of wood."   In "Nature" journal in 1968 I reported the conclusions of Dr Ian Simmons and other Durham colleagues regarding samples taken from the sandy and silty layers just above the raised beach.   Ian showed that the pollen and plant remains are fully representative of an interglacial environment.  Quercus (35% of total tree pollen), Alnus (43%) and Corylus (42%) were the dominant constituents, with Pinus only moderately represented (13% of tree pollen).  Non-tree pollen accounted for 85 of the 343 pollen grains counted, with Gramineae, Cyperaceae and Filicales moderately well represented.  Other lesser plant pollen (eg Chenopodiaceae and Armeria) suggesting proximity to littoral conditions.  The vegetation was thus a mixed oak and alder forest with pine and hazel, with salt-tolerant plants close to the water's edge.  Carex, Juncus and other water plants point to an environment that included small open pools with patches of marsh and fen and carr vegetation.    Botanists who have examined my own evidence incline to the view that this was a fresh-water rather then a salt-water (estuarine) environment.

Other researchers tend to agree with this interpretation.  For example,  Bowen (1974) found Alnus tree stumps in a growth position on the surface of the "loam" and dated one of them to >35.5 ka.  This would suggest an Early or Middle Devensian (and possibly an Ipswichian) age for the silt and clay series.   Morey (1997) drew on the research of Stevenson and Moore (1982) and wrote as follows:

"..........Stevenson and Moore (1982) recorded the aquatic taxa, Sparganium, Potamogeton, Typha, Nuphar, Nymphaea and Polygonum amphibium together with Valeriana officinalis, indicating the presence of areas of open, fresh, water bordered by a tall herb- marsh community. Their data also indicate a regional flora with the trees and woodland species characteristic of a temperate (interglacial) environment........... Since estuarine muds deposited in a temperate environment typically contain a substantial fauna with forams, ostracods and small gastropods, as well as larger bivalves etc. the lack of marine fossils makes an estuarine origin for this unit appear unlikely and the earlier interpretations should be questioned. It seems more reasonable to interpret Unit 3 as an alluvial deposit characterised by pools of fresh water. Other taxa present, Hippophae, and Plantago maritima, could be derived from a surrounding dune community.  Stevenson and Moore (1982) also noted a record of Ruppia maritima by Turner, but the presence of a species which is usually associated with brackish pools does not conflict with this interpretation as a marshy valley among coastal dunes."

In 1973 Stevenson and Moore found the following sediment sequence:

Head deposits overlying:

Yellow/orange sandy silt
Grey/yellow sandy clay
Yellow/orange clay with abundant pebbles.
Apparently sharp hiatus
Stiff blue/grey clay with sandy bands at 106 cm. Organic sediments, laterally variable in nature were found within this unit, as was evidence of current bedding in the inorganic sediments.
Grey—brown silty clay. (with included Alnus wood layer). Organic remains become more abundant towards its base; especially obvious are wood fragments
Pebbles in a grey, sandy-clay matrix. Larger pebbles (up to 5 cm diameter) were concentrated in the lower layers.
Very fine white sand, cross-bedded
Very fine yellow sand with an iron-rich layer
Fine yellow and white sands, particles of larger size evident towards the base
Iron concreted, yellow and red sands
Coarse-grained yellow sands with hard bands of ferruginous, cemented material
Pebbly, raised beach deposits

Stevensen and Moore (1982) found four pollen assemblage zones in the silt and clay sequence, all dominated by temperate forest taxa -- so they were convinced that the climate throughout the whole sedimentary episode was temperate rather than glacial or periglacial.  They were inclined to suggest a Hoxnian interglacial age for this episode, but others (such as Campbell and Bowen in 1989) preferred an Ipswichian or Last Interglacial interpretation.

One interesting feature of the work by Stevenson and Moore is the presence of a "hiatus" in the pollen sequence in their Zone WA-2.  They suggest that there was an episode of extensive forest destruction, followed by secondary succession and woodland recovery, but resulting in a changed floristic composition. Such destruction could have resulted from flooding or erosion. The possibility of habitat disturbance as a result of factors associated with local fluviatile conditions is very real in this swamp-carr site. Marine incursion is also possible.

Another suggestion (and it is no more than that) is that towards the top of the sequence there is an increase in Pinus pollen and a decline in some other species -- possibly indicative of a "post-temperate" plant assemblage taking over from a truly interglacial one.  Does this represent the end of the interglacial and the onset of colder -- and eventually periglacial -- conditions?

 Stevenson and Moore pollen diagram for the silt and clay series.  Note that near the junction between the blue clay and the yellow clay there is a sharp decline in oak pollen and a corresponding increase in pinus pollen.  Does this indicate a cooling of temperature at the end of the interglacial episode?

In the absence of accurate dating for the sediments and their plant remains,  all we can say for the moment is that they seem to be linked with the raised beach, that they were probably laid down in a largely freshwater environment of pools and marshy patches, and that the accumulating sediments might have been protected from the open coast by a barrier of sand dunes.  The environment is an unusual one, in that the Angle Valley runs right across the peninsula  as a limestone "dry valley" containing no substantial stream.  This may explain why the circumstances for sediment accumulation here were not at all similar to those which prevailed in other valley mouth situations such as Abermawr, the Nevern Estuary, Newgale, and Goodwick.  But it's reasonable to assume that when the silt and clay series of sediments was accumulating, sea-level was not very much below that of the present day; if it had been, I assume that the water table on the valley floor would have been much lower, and that pools of standing water would not have survived in this vicinity for prolonged periods.  The suggestion of a sudden marine incursion (a tsunami?) high in the sediment sequence also indicates that the sand dune barrier might not have been very strong, and that through most of this chapter in the story, sea-level was at its "interglacial" or high-stand level.