Was there a Bristol Channel Ice Stream?

 

The revised model from Ely et al.  The white areas show thin ice and sluggish or non-existent ice movement. The purple areas show ice streams or zones of relatively rapid ice flow.  Note the big Irish Sea ice stream and the much smaller but associated Bristol Channel ice stream heading east and pushing onto the Somerset Levels.

Thanks to Bevins et al (2025) for pointing me towards this article:

J.C. Ely, C.D. Clark, S.L. Bradley, L. Gregoire, N. Gandy, E.Gasson, R.L.J. Veness, R. Archer
Early View. Behavioural tendencies of the last British-Irish Ice Sheet revealed by data-model comparison
Journal of Quaternary Science. (2024)

It's a comprehensive and very specialised study of the hundreds of computer models of the behaviour of the British and Irish Ice Sheet (which also goes by several other names)  -- most of them relating the the Devensian glaciation.  They range from maximal to minimalist models and from extreme ones to ultra cautious ones.  Many of the older models can be rejected because the parameters used in their creation are now inadequate -- but the work of the BRITICE project has stimulated a new generation of models with much greater and more careful ground truthing used to check on their viability and accuracy.

Anyway, in tying everything up at the end of an extensive analysis, the authors produced a map for the southern part of the Ice Sheet which showed that (a) the ice sheet must have crossed the coastal barrier of Devon and Cornwall and impinged upon the small local ice caps of ther SW Peninsula (Dartmoor and Exmoor in particular) and (b) that there might well have been an eastwards flowing ice stream in the Bristol Channel.

I must admit that the latter suggestion (it is no more than that) came as a surprise to me, since previoius models have almost always suggested that the Bristol Channel was largely ice free at the times of extensive glaciation.  Partly, as I have pointed out many times on this blog, this defect arose from the assumption of an ice-free enclave in South Pembrokeshire, which makes no sense from a glaciological perspective.  So now we have a modern and apparently reliable model that agrees substantially with the situation portrayed in these mapped reconstructions:

After Kellaway, Williams-Thorpe and others

After Gilbertson and Hawkins

My own suggestion

Note that the latest modelled reconstruction shows ice pressing across the whole of Cornwall, and that the model does not show the greatest extent of Devensian ice in the Celtic  Sea.  Here the modelled outer edge of the Celtic Sea piedmont glacier is shown around the position of the Isles  of Scilly.  But as Scourse and others have pointed out, the extreme position was much further to the south, at the shelf edge.  At that time the ice must have been thicker and more extensive in the Bristol Channel, with accelerated streaming and a progression well inland of the Somerset coast.

Gradually, it all comes together............

The Stonehenge Lynch Mob marches out............

 

Well, this is fun.  The Stonehenge Lynch Mob has assembled all its forces and has marched out in the light of the midsummer moon, determined to string me up from the nearest trilithon.........

Their latest paper, a long and rambling (and in places repetitive) attack published in the Journal of Artchaeological Sciences, has no less than 11 authors, including MPP, Mike Pitts, geologists Bevins and Ixer, geomorphologist Jim Scourse, and archaeologist David Field.  Our old friend Tim Daw is in there as well.  

We have been waiting for this paper for some time, since it was prematurely cited by MPP et al towards the end of last year.   It was clearly rejected by the Journal of Quaternary Science in January 2025,  and later accepted (with revisions) by the Journal of Archaeological Science.  Make of that what you will.........

https://brian-mountainman.blogspot.com/2025/02/myths-fantasies-and-now-phantom-articles.html

There is a wonderful irony in the fact that the defenders of the establishment narrative have here written a long and detailed paper designed to destroy the "glacial transport hypothesis" and the credibility of my 2024 paper, having for the greater part of a decade refused to cite any of my publications or acknowledge that their bluestone narrative is disputed by anybody.  Indeed, I have complained on many occasions of their academic malpractice in this regard.  Suddenly, I find myself cited, not just once or twice, but in paragraph after paragraph of this new paper, with multiple quotations added in italics!  So I am very flattered.......

Who would have thought that a little boulder found in a cardboard box could have attracted so much attention?  Newall would have been delighted.

Don't you just love the title of the article?  ".... correcting the record."  The authors clearly think that they have replaced something dodgy with something authoritative and utterly reliable.  Hmmm.  Their arrogance knows no bounds.  Maybe I should now write something called "The Stonehenge Bluestones:  the truth" ??  What they have actually done, in this new paper, is to present a string of assertions and speculations as facts, as I shall demonstrate when I publish my detailed scrutiny.  Their over-interpretation of questionable evidence is par for the course; they do it all the time.

Watch this space..........

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Richard E. Bevins, Nick J.G. Pearce, Rob A. Ixer, James Scourse, Tim Daw, Mike Parker Pearson, Mike Pitts, David Field, Duncan Pirrie, Ian Saunders, Matthew Power, The enigmatic ‘Newall boulder’ excavated at Stonehenge in 1924: New data and correcting the record, 

Journal of Archaeological Science: Reports, Volume 66, 2025, 105303, 

ISSN 2352-409X, 

https://doi.org/10.1016/j.jasrep.2025.105303.

Plumstone Rock

Somehow or other, Plumstone rock has escaped our attention.  It is a prominent rhyolite tor located on the ridge of Ordovician volcanic  rocks that runs between Roch Castle in the west (near Newgale)  and Trefgarn Gorge in the east.  The most prominent crags on the ridge are Poll Carn (Lion Rock) and nearby Maiden Castke (called by the locals the "family of lions" for obvious reasons).   

The rocks are for the most part flinty bluish rholotes, with considerable internal variation, including welded tuffs and agglomerates.  In certain light conditions the rocks appear to be pinkish or orange in colour.  The age of these rocks was disputed for many years, having been originally labelled as Precambrian -- but they now seem to be accepted as Ordovician.

The rock is hugely impressive and intimidating -- but  it is easily accessible from the Haverfordwest - Hayscastle road, and there is an easy short walk to the tor from the car parking area on the common.

It does not have the fragility of  Maiden Castle, and while the bulk of the tor is solid bedrock, on its flanks there are numerous massive detached blocks.  It is -- naturally enough -- a facvourite place for "bouldering".  I have not seen any striated surfaces on the tor, but there are some forms that are suggestive of ice moulding.  The big question is this -- what do the four tors on this ridge tell us about the history of glaciation across Pembrokeshire?

Newgrange: too much mythology and not enough facts

In this rather interesting article there is a timely assessment of some of the mythology surrounding Newgrange -- probably the most iconic prehistoric site in Ireland. The authors point out that many of the assumptions about Newgrange being a "special" place built by a powerful ruling clan as a tribute or homage to a "king" or powerful ruler are based on very little evidence -- or no evidence at all. They suggest that Newgrange was built over a very long period in many different phases, and that those buried there were not necessarily related, or people of high status within a ruling elite. They prefer a simpler story, devoid of heavy symbolism and romanticism -- indeed, somehat utilitarian and somewhat boring.

There are lessons here for all of us -- especially those who have developed the fanciful West Wales narrative of sacred and special places, magical stones, heroic quarrying activities and even more heroic long-distance stone haulage expeditions........

The post-processual obsession with fanciful narratives has a lot to answer for.

It might just be a good idea for the archaeologists working in West Wales to go back to basics and work out just what evidence there is on the ground, as suggested by quite a few of us from other disciplines over the years.




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Smyth J, Carlin N, Hofmann D, et al. The ‘king’ of Newgrange? A critical analysis of a Neolithic petrous fragment from the passage tomb chamber. Antiquity. 2025;99(405):672-688. doi:10.15184/aqy.2025.63

ABSTRACT

Recent genomic analysis of a skull fragment from Newgrange, Ireland, revealed a rare case of incest. Together with a wider network of distantly related passage tomb interments, this has bolstered claims of a social elite in later Neolithic Ireland. Here, the authors evaluate this social evolutionary interpretation, drawing on insecurities in context and the relative rarity of engendered status or resource restrictions in the archaeological record of prehistoric Ireland to argue that the status of individuals during this period is better understood through unstable identity negotiations. Inclusion in a passage tomb, while ‘special’, need not equate to a perpetual elite.

Carn Fran summit

 

Many years ago (about 63, to be more precise) Francis Synge pointed out to me that the rhyolite hills between Fishguard and Dinas were rather interesting.  He pointed out how smooth and rounded they were, in contrast to the craggy uplant tors found at higher altitudes on Mynydd Dinas, Carningli and Mynydd Preseli.  The main summits are Carn Fran and Carn Gelli, and there are half a dozen minor summits as well.  They are all "clean" and relatively smooth, and a number of geomorphologists in the past have suggested that they were glaciated quite recently while the other higher summits were above the upper glaciation limit.  

Nowadays it is accepted that that interpretation is rather simplistic, and that changes of landscape characteristics may be related to changes in glacier bed conditions.  Thin ice on rounded upland terrain may have been frozen to its bed -- ant therefore incapable of intensive erosion -- while thicker ice in the lowlands may have been above the pressure melting point, flowing faster and with greater erosive capacity........

In the past I have never managed to get up onto the summits of these hills because of thick vegetation -- gorse, brambles, heather and bracken.  But in recent years a "permissive path" has been opened, and this gives easy access to Carn Fran.  We have been doing some work up there -- more of which in due course......

 

The Foel Drygarn quarries

 

I have done a number of posts on the Bronze Age and Iron Age quarries near the summit of Foel Drygarn.  I was up there a couple of weeks ago, and this is one of them.

  I am quite convinced that the quarrymen were quite disinterested in large blocks of stone, and targetted rubble and small stones that could be used in the 3 spectacular burial mounds on the summit and in the defensive embankments around the settlement site.  In most cases all they had to do was to take loose stones from banks of scree -- but in some cases they have clearly taken loose stones from the degraded flanks of the rhyolite and micro gabbro tors.

Nothing much was needed in the way of technology, although I would guess that wooden levers might have been used in order to extract the stones from the ground.

A Foeldrygarn puzzle

This is a photo of one of the microgabbro outcrops near the summit of Foeldrygarn.  The outcrop is a small one, surrounded by grassy banks.  It's a degraded small tor, but here the focus of interest is the semi-circular arrangement of stones set in the turf.  This is quite unlike anything I have seen elsewhere in Preseli.  There are plenty of semi-circular stone banks set against small cliffs in the uplands of Preseli, but these are characteristically composed of curving lines of boulders or low ridges up to 2 m wide.  Some appear to have been low walls that maybe supported roof timbers -- with the upper ends of the timbers supported against the rock face.

Here on Foeldrygarn we see a "band" of large boulders or slabs, many of which seem to have been placed end to end...........

The site lies within the summit hillfort and not far from the triple Bronze Age burial mounds -- all made with locally quarried stones which were carried short distances uphill.  The stones were all small enough to carried by one man -- or sometimes two men working together.  Large boulders and slabs were rejected on the grounds that they were unmanageable -- and maybe this holds the clue to what was going on.  Maybe the "band" of large stones was made entirely of rejected stones, pushed aside while the smaller stones and finer debris fragments were carried away for the construction of bural mounds and later for the fortified mounds that are prominent features of the site?

Has anybody seen anything like this elsewhere?  Any other theories about what was going on here?