THE BOOK
Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
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Thursday, 17 October 2019

Caldey Island -- a till or not a till?




In the summer issue of Quaternary Newsletter Prof John Hiemstra and several colleagues published a short note on the "diamicton" at Ballum's Bay on Caldey Island, which I have referred to on a number of occasions on this blog.

https://brian-mountainman.blogspot.com/2011/08/devensian-till-at-bullums-bay-caldey.html

I have been convinced since 2011 that this deposit is a Late Devensian till, and I have not changed my mind.  Anyway, I encouraged John and others to go and have a look at it, which they duly did, and they decided that it is "probably" an old Anglian deposit which has been redistributed and redeposited under periglacial conditions in the Late Devensian -- some way from the nearest glacier.  Their article is available on Researchgate, where it can be scrutinised.

https://www.researchgate.net/publication/333998714_Caldey_%27Kald_ey%27_in_Old_Norse_was_literally_a_%27cold_island%27_but_was_it_under_Devensian_ice

I didn't like their line of reasoning, and say so in the new edition of QN, just published:

https://www.researchgate.net/publication/336614738_COMMENT_ON_CALDEY_'KALD_EY'_IN_OLD_NORSE_WAS_LITERALLY_A_'COLD_ISLAND'_BUT_WAS_IT_UNDER_DEVENSIAN_ICE_QUATERNARY_RESEARCH_FUND_REPORT_BY_JOHN_HIEMSTRA_ET_AL

I didn't expect them to row back on their earlier opinions, and of course they have responded to my published points by saying that they still think they are right -- and to give a proper picture of their arguments I have added their comments after my own.  All good fun.

Of course, it's easy for them to say that I am basing my conclusions on "basic" rather than intensive fieldwork and on my detailed knowledge of the Pembrokeshire coastal exposures -- and they are right that I have no detailed laboratory studies or dating results to back up what I am saying.  The joys of being old, retired and disreputable!

But I will maintain, until something strong comes along to prove me wrong, that the Caldey till exposure is unexceptional, and that there are many other similar till exposures along the south Pembrokeshire coast -- as itemised on this blog -- that show that the Late Devensian ice pressed far to the east.  I repeat -- their explanation of the deposit as a "redistributed ancient till" is more convoluted than it needs to be, and is unsupported by any convincing evidence.


Of course, none of us ever looks at an exposure in a completely impartial way, and I dare to suggest that John and his colleagues may be just a little influenced, in their attitude to the Ballum' Bay exposure, by their interpretation of some of the deposits on the Gower coast, and at Rotherslade in particular.  They claim that in the cliffs on the south Gower coast there are great thicknesses of "redistributed till" which were rearranged beyond the edge of Late Devensian ice.  On balance, I disagree with that too, since I consider that the authors have not demonstrated in their paper that the studied deposits were not simply deposited (and maybe rearranged) in a highly dynamic and changeable ice wastage environment at or near the peak of the Late Devensian glaciation.........

That paper is here:

https://www.academia.edu/11862453/Reinterpreting_Rotherslade_Gower_Peninsula_implications_for_Last_Glacial_ice_limits_and_Quaternary_stratigraphy_of_the_British_Isles?auto=download

Hiemstra, J. F., Rijsdijk, K. F., Shakesby, R. A. and McCarroll, D. Reinterpreting Rotherslade, Gower Peninsula: implications for Last Glacial ice limits and Quaternary stratigraphy of the British Isles.
J. Quaternary Sci., (2008). ISSN 0267-8179









Preseli -- glacial deposits


Copy of a map by WD Evans (Plate 4 of his QJGS article) -- designed to show where the areas of exposed rock are to be found, but if you concentrate instead on the "boulder clay" or till areas, you can see just how extensive they are, both to north and south of the upland ridge.


I have been digging up some ancient papers and doctorate theses from the 1940's -- and have turned up some quite useful information.  Two researchers had interesting things to say-- WD Evans and JC Griffiths -- both of whom submitted doctorate theses to the University of London.

Sadly, it is not always easy to get at old papers -- the QJGS articles are still trapped behind paywalls, including this one:

The Geology of the Prescelly Hills, North Pembrokeshire
William David Evans
Quarterly Journal of the Geological Society, 101, 89-110, 1 October 1945, https://doi.org/10.1144/GSL.JGS.1945.101.01-04.04

Evans did not have much to say about glaciation, but Griffiths's thesis was titled "The Glacial Deposits west of the Taff, South Wales" (1940), and although in many ways it is a rather poor piece of research, he was convinced that there was at one time a Preseli ice cap, and that it may well have existed before the mountains were "overwhelmed" by Irish Sea ice.

This is an interesting map, from a 1984 NERC report on drainage in the Preseli Hills:


The stippled area covers all the land above 200m -- so this might give an indication of the extent of the intermittent ice-cap, which we have referred to on many past occasions.

Griffiths also mentioned blue clay till at Llangolman -- again I have described this before:

https://brian-mountainman.blogspot.com/2014/10/pre-devensian-glacial-deposits-south-of.html

In 1904 TJ Jehu, one of my great heroes, described a clay pit at Llyn (Grid ref SN112274) or Fagwyr Owen, to the NW of Llangolman.  This was in open country, just above the 600 ft contour.  Jehu described the clay pit as containing "boulder clay" and of being 20 ft deep -- so deep that ladders had to be used to get in and out.  The clay is bluish and very tough, and was referred to back in 1904 as "india-rubber clay."  From the map and written evidence, there may have been more than one clay pit in the vicinity.


One thing that is very confusing, on the Geology of Britain viewer, is that on a small scale, the deposits both to the north and the south of the Preseli upland are labelled as "till", whereas when you zoom in the deposits to the south change from blue to a muddy sort of colour, with a different label.

The blue area is described thus:
Till (Irish Sea Ice) - Diamicton. Superficial Deposits formed up to 3 million years ago in the Quaternary Period. Local environment previously dominated by ice age conditions (U).

On the other hand, the area to the south has these words attached:
Head - Diamicton, Gravel, Sand And Silt. Superficial Deposits formed up to 3 million years ago in the Quaternary Period. Local environment previously dominated by subaerial slopes (U).
So on the one hand the till is deemed to be fresh, and on the other it is deemed to be mixed up with brecciated slope deposits and other materials.  I don't know that this distinction is based on any hard evidence -- I suspect that there is simply an assumption (based on the presumptions of Dai Bowen and others) that the till to the north of Preseli is Devensian and the till to the south is Anglian -- belonging to the mythical "Penfro Till Formation."

In other words, nobody knows what is going on, and somebody needs to sort it out.

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

Where did this till on the south side of Preseli come from?  How old is it?  I have assumed in the past that it is very old -- and therefore Pre-Devensian.  Now I am not so sure.

Wednesday, 16 October 2019

HH Thomas and his glacial blind spot

Fig 20 from the Haverfordwest Memoir, showing the distribution of erratic boulders discovered by the field surveyors.  No ice limit is shown -- they knew that the ice flowed well to the east of Pembrokeshire.  The stippled areas represent areas of sands and gravels.

I have been looking again at the Geological Survey's Memoir No 228, published in 1914 and covering "The Country around Haverfordwest."  It also covers a large swathe of country eastward of the county town, as far as the border with Carmarthenshire.  It's noteworthy that the authors were Strahan, Cantrill, Dixon, Jones and -- here is the important name -- HH Thomas.

In the section of the memoir on Glacial Deposits, the "local details" are attributed to each of the key field researchers, and the section relating to the stretch from Whitland through to Haverfordwest was written by Cantrill and by HHT himself.  Thomas was clearly the man tasked with describing the fluvioglacial deposits of this stretch.  Like the others, he knew that glacier ice had covered the whole of the area and that it had flowed from Pembrokeshire out into Carmarthen Bay and well to the east.

In a previous post, I wrote this:

In the Pembroke and Tenby Memoir, as in the others relating to West Wales, a vast amount of evidence (collected by Thomas, Cantrill, Strahan, Dixon and Jones) is presented which shows that glacial deposits are widespread, and that erratic transport was not just possible but well documented. In the memoir, there is reference to erratics transported from Pembrokeshire to the Swansea area and to Pencoed in Glamorgan. Thomas knew that boulders could be carried by ice for at least two hundred miles -- and indeed he was perfectly familiar with big erratics of Scottish origin in Pembrokeshire -- and yet he deemed the transport of Stonehenge bluestones to have been impossible. 

I am struck yet again by the sheer illogicality of Thomas's position on the transport of the bluestones, since the human transport hypothesis with regard to the Stonehenge bluestone boulders flew in the face of all the evidence that he and his Geological Survey colleagues had so painstakingly collected over the years of fieldwork.  They deduced that ice carried spotted dolerite (diabase) and other igneous erratics from Pembrokeshire and Scotland at least as far east as Glamorgan -- but without any solid evidence to support him, Thomas argued that the glacier responsible could not have progressed any further towards Somerset and Wiltshire.  Weird.........

I'm forced to the conclusion -- yet again -- that Thomas was motivated not by good science but by the desire for notoriety, when he gave that famous lecture in 1921.

Tuesday, 15 October 2019

The South Pembrokeshire "ice-free enclave" -- just a fantasy?


Gradually my confidence in the Late Devensian "ice free enclave" in South Pembrokeshire is slipping away, in the face of evidence building up by the day.   There's work in progress, but here are some enlarged sections from the Geology of Britain viewer:

Daugleddau confluence

Gravel terrace remnants (?) north of Haverfordwest

Sands and gravels and till patches around Clynderwen

Extensive patches of till around Ludchurch and Templeton

Till patches and sands and gravels in the Dale area

Till spreads and sands and gravels inland of the St Bride's Bay coast

Waun Mawn -- what next?


Quote from the 2018 Waun Mawn Report:

Ongoing plans

The Waun Mawn results are extremely encouraging, confirming the existence of a bluestone circle dismantled in prehistory, very likely to be one of the monuments from which Stonehenge was built. When the full analyses of scientific dating and geological analysis are completed, we plan an interim publication on these exciting results in the international journal Antiquity.

No further excavations are planned in 2019 but we hope to return for another season of excavation in 2020. In 2019 the project’s archaeo-astronomer, Prof. Clive Ruggles will analyse the stone circle’s astronomical attributes to establish whether it was oriented towards midsummer solstice sunrise or northern major moonrise.

Acknowledgements

We thank the Gerda Henkel Stiftung and the Rust Family Foundation for their financial support as well as UCL and the University of Southampton for their fieldwork contributions. Raw-Cut TV have also supported the project in recent years. The NERC Radiocarbon Panel awarded a grant for dating of 39 radiocarbon samples from Waun Mawn. Richard Bevins, Rob Ixer and Nick Pearce provided geological identifications.

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

This, of course, is nonsense:  "......confirming the existence of a bluestone circle dismantled in prehistory, very likely to be one of the monuments from which Stonehenge was built."   But we'll move swiftly on.

I'm intrigued by the sponsorship by Raw Cut TV -- so there is, as we thought, a documentary in the making.  The company says this about itself:  "we are the industry leader in crime documentary ‘blue light’ programmes."  Wow -- is Waun Mawn now confirmed as a crime site?  The biggest archaeological hoax of all time?  Remember, folks, you heard it from me first......

The only thing that might have happened this year?  Maybe Clive Ruggles checking on the archaeo-astronomy of the supposed standing stone circle?  Apparently he was planning to check whether the circle was oriented towards midsummer solstice or northern major moonrise -- I am greatly intrigued by the concept that a circle can be oriented towards anything at all, but there you go.......  but if you try hard enough, I suppose you can always find a stone or a slight depression that you might wish to call a stone socket aligned with something or other.  The search for significance is a wonderful thing, and can become an obsession.


I'm reminded of all the lovely people who take pictures of the setting or rising sun shining brightly beneath the capstone of Pentre Ifan (or some other cromlech) and between the supporting pillars, and then saying "Ah yes -- this was clearly the intention of the builders, and explains why the cromlech was built just here."  They never do get round to explaining what is significant about 8.39 pm on August 13th -- or whatever -- which was the time at which the "perfect" photo was obtained.  There's nowt so queer as folk.

It reminds me too of the Robin Heath school of number-crunching, circles, lines and triangles, in which he seems to suggest that all archaeological monuments (or rather, the ones he chooses to select) were built at precise points according to strict geometrical patterns -- although the "points" were hundreds of miles apart and although the Neolithic builders were not in possession of GPS positioning devices.  His suggestion seems to be that our Neolithic ancestors were such brilliant readers of the stars that they were able to precisely position their "meaningful megalithic structures" to within a few metres, and that the inhabitants of communities widely separated across these islands were all somehow tuned in to the same cunning plan devised by the God of Mathematics or some such deity.  Wonderful stuff.  "Sacred geometry" is the term Robin uses, claiming some sort of ancestry involving Prof Fred Hoyle.   But it doesn't do anybody any harm, and I suppose it keeps people out of mischief......








Robin recently ran a two-day course in North Pembs (£315 pp) on "sacred geometry" and his particular version of "proto-Stonehenge" -- I hope those attending got their money's worth!

A favourite post of mine relates to the position of Woolworths Stores, as mapped by Matt Parker.


Quote: ".........in any sufficiently large set of random data it is possible to find meaningless patterns of any required accuracy.”

In any set of points plotted on a map (such as a map of Neolithic or megalithic sites in the UK) you can simply skip over the vast majority of the sites that happen to be inconvenient, and home in on the few that happen to coincide with the lines or corners of whatever triangle or other shape that you choose to demonstrate as "meaningful." The more data or plotted points you have, the greater is your ability to pull meaningless patterns from them.
Matt Parker had the locations of 800 Woolworth stores to work with. He was still able to find close "fits" with his chosen lines, distances, and geometric shapes, just as Robin Heath and others have done with their maps. The more random or precisely positioned points you have on the map, the greater the chance of finding "meaningful" patterns. If you just plot standing stones, or Neolithic henges, on a map, some geometric patterns will be found; but if you then add long barrows, round barrows, causeways, etc, your data set is greatly enlarged, and more and more "patterns" can be "discovered." If you want to increase your prospects of finding patterns even further, you can add in ALL prehistoric features, or "meaningful points in the landscape", such as Carn Meini, Glastonbury Tor, Lundy Island, Bardsey island, Caldey Island, or the tips of peninsulas or river mouths. You end up with hundreds if not thousands of points in the landscape, enabling you to find patterns everywhere, with close matches for triangles of various shapes and sizes, circles, straight lines, and curves.

You can play little games, just as they do in Playgroups and primary schools with very small children, by creating predetermined shapes (such as triangles of circles) and moving them around on your map with thousands of random points in it, and finding "fits." If the points of your triangle do not EXACTLY coincide with the "meaningful places" on your map, you can explain this away by using some pseudo-scientific phrase relating to degrees of confidence, or by saying "the fit is accurate to within 0.5%" or "the fit is almost perfect" -- or even by saying that the map itself is inaccurate, or that coastal erosion since the Neolithic has moved your crucial point from A to B. This is quite wonderful! You can do almost anything, and find "meaning" and "ancient wisdom" or "sacred geometry" in almost anything, as Matt Parker has pointed out.

This is not science. It is pseudo-science, pure and simple. Put another way, it is a little game that one might play with one's grandchildren. What is amazing is that some people actually write books about this sort of stuff, and that people buy them and read them, and are apparently swept away into a state of wonderment. What does it tell us about the human condition? Well, it tells us, I suppose, that the yearning for a rediscovery of "ancient wisdom" is still as strong as ever, that people have a strong sense of spatial awareness, and want to find patterns or "sacred geometry" in landscapes, or order where there is chaos. It also tells us that people are remarkably poorly educated and that they are just as gullible as our ancestors were in the Middle Ages.

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

This is all part of a continuum -- and, I suppose, part of the human condition.  When faced with features in the landscape some people will always look for significance, and go to enormous lengths to find it, assuming that there was, long ago, an ancient wisdom that we must try to identify or unravel.  I suspect that in reality many of the monuments that we like to call "sacred" were actually rather utilitarian, built not out of reverence for the heavens and the starry alignments but just because that was where Grandfather Dafydd lived, or liked to sit in the sun, or where some large stones happened to be lying around.




Thursday, 10 October 2019

New Atlas Chapter now available




Superficial deposits and ecology / habitats in Pembrokeshire

As I never tire of saying, we will never fully understand the enigma of Stonehenge unless we also understand what happened "upstream" with regard to the ice stream that is suspected of entraining and transporting all those lumps of bluestone. We are referring to an hypothesis here -- and we must always accept that this may not be the truth -- but currently the evidence looks strong, and far stronger than anything brought forward in support of other hypotheses.

When I was asked to write the introductory chapter of the new Historical Atlas of Pembrokeshire I was happy to oblige -- and as I have mentioned before, it was published quite recently.  It's an awkward volume to get extracts from, because the book is a large-format square -- but I have now done some tweaking of my own copyright manuscript material, and have added the excellent maps drawn from my roughs by Anna Ratcliffe.

I'm very happy to give the Atlas some more publicity! Details:

Howell, D.W. (ed) 2019. An Historical Atlas of Pembrokeshire (Volume 5 of the Pembrokeshire County History). Haverfordwest, Pembrokeshire County History Trust, 205 pp, £30.00.


Monday, 7 October 2019

Confusion reigns -- Late Devensian ice limits


This map of Late Devensian ("Newer Drift")  ice limits in South Wales was published in the GCR volume in 1989, and since then, many other limits have been proposed.   Confusion reigns.  I have been  involved in this chaos myself -- most recently in this blog.

In northern and western Pembrokeshire the evidence of relatively recent glaciation is now very strong, and it has been demonstrated that the old lines drawn by researchers prior to 1960 are fundamentally incorrect.    But the really big problem is that the  evidence of glaciation in the "south Pembrokeshire" is very subtle.  There are glacial deposits, and fluvioglacial deposits too -- but they are thin and patchy, and the consensus over the years is that they belong to the "Older Drift."  The Geological Survey still records them on the Geology of Britain viewer as Mid-Quaternary -- ie belonging to the Anglian Glaciation, or maybe even older.  in 1971 I proposed that most of mid-Pembrokeshire was glaciated in the Late Devensian, and that only the Castlemartin Peninsula and the southern coastal strip remained ice-free.  David Bowen, mindful of the considerable expanse of fluvioglacial gravels in the valley of the Western Cleddau as far south as Haverfordwest and Landshipping, suggested an ice spur projecting southwards from the Roch-Trefgarn ridge -- but this proposal has not had much support from anybody else.    But now I'm coming round to it, and I think DQB may be close to the truth.

The other thing that has happened is that I have been back to the southern and western coasts of Pembrokeshire, and am now convinced that all of them, at least as far east as Tenby, were affected by Late Devensian ice.  But how far inland did this ice actually push?

Well, the geology map shows patchy glacial and fluvioglacial sediments all over the place -- no part of Pembrokeshire is "peculiarly free" of these materials.


Above: The geological map of the mid west of Pembrokeshire.  This shows the extent of the sands and gravels on the flanks of the Western Cleddau valley -- while leaving open the possibility that they are all very ancient river terrace remnants that have nothing to do with glacial ice in the vicinity.  They may have been built up during past episodes of large-scale meltwater flow through the Trefgarn Gorge and thence southwards towards Milford Haven.  Work is needed on this.

The map shows that the tills described in my recent posts for the Nolton- Druidston coastal strip extend inland for maybe 500m or so, but no further.  But then another extensive area of till is shown further inland, and another to the NE of the A487 road.  Are these deposits related in age, or could they be much older?  And how many patches of till have been missed completely?

Never fear, dear reader.  I am on the case, and will report back shortly.


I am less and less convinced by the idea of a Late Devensian ice-free enclave........