Scottish erratics and the Irish Sea Ice Stream

 

Map of the northern British Isles, showing the main ice shed (ice divide) area which separated glacier ice flowing NW and W into the Atlantic and ice flowing broadly southwards in the Irish Sea Ice Stream.    Almost all of the reconstructions relate to the Late Devensian Glaciation.......

The traditional map of iceflow directions, based on Wright (1914)

The BRITICE-CHRONO map for 27,000 yrs BP -- ie near the peak of the Late Devensian Glaciation

Now this is interesting.  Geomorphological dilemmas are always interesting -- but they all get sorted out in the end........

It's all got to do with ice sheet summits and the positions of ice sheds.  I say "positions" because they are never static.  Shifts in snow accumulation patterns and drainage route efficiency happen all the time in modern ice sheets, as they did in the past. So during the course of a single glacial episode you may find that an ice shed (between diverging flowlines) may shift by 100 km or more.  And an initial  northward shift (for example) may be replaced later on by a similar or even greater southward shift.

See this article too:  "Flow pattern evolution of the last British Ice Sheet" by Anna L.C. Hughes, Chris D. Clark, Colm J. Jordan

https://nora.nerc.ac.uk/id/eprint/507185/1/Flow%20pattern%20evolution%20QSR.pdf

Hughes, A. L. C., Clark, C. D., & Jordan, C. J. (2014). Flow-pattern evolution of the last British Ice Sheet. Quaternary Science Reviews, 89, 148-168. 

https://doi.org/10.1016/j.quascirev.2014.02.002

The dilemma of current interest relates to the presence of erratics presumed to come from the western isles of Scotland found along the coasts of Devon and Cornwall.  Paul Berry tells is that the famous pink granite erratic at Saunton has probably come from Gruinard Bay in Wester Ross.  That's north of the Isle of Skye and at the same latitude as the Isle of Harris -- on the eastern shore of the Minch, which was (according to current wisdom) one of the great northwards ice discharge routes in the Late Devensian Glaciation.  That's 200 km north of the assumed Late Devensian ice shed position.  I have been reminded of this dilemma by a recent suggestion from Prof Peter Kokelaar that he has seen a number of glacial erratics on the Gower that have come from the Western Isles -- well to the north of the supposed ice divide.

Almost all of the ice shed positions described in the literature show that they lay on a line approximately joining Belfast to Glasgow -- across the North Channel and running NNE --SSW.  Some reconstructions show an ice shed running NE-SW along the Southern Uplands of Scotland, and some show an ice divide approximately on the southern part of the Isle of Arran and running across the tip of Kintyre -- but always the assumption is that the ice from the ice shed flowed across Islay and the Malin Shelf and westwards out into the Atlantic.  I have seen no Devensian reconstructions showing a broadly southward flow of ice through the North Channel.  

Some interesting work on erratic distributions, from Veness et al, shows us that erratic dispersal tracks can be quite different during the advance and retreat stages of the same glacial episode.  This shows up in the maps of Shap erratic distributions and the complex distributions from the Loch Fyne source.  It's clear that the Irish Sea Ice Stream can have carried Shap granite erratics and erratics from the northern end of Loch Fyne hundreds of kilometres to the south.  We should not be surprised by this, in view of the relative abundance of Ailsa Craig erratics in Pembrokeshire and Gower.

See this:
Modelling erratic dispersal accounting for shifting ice flow geometries: A new method and explanations of erratic dispersal of the British–Irish Ice Sheet
R. L. Veness, C. D. Clark, J. C. Ely, J. L. Knight, A. Igneczi, S. L. Bradley,  15 May 2025

https://doi.org/10.1002/jqs.3720

https://onlinelibrary.wiley.com/doi/epdf/10.1002/jqs.3720

See also:  https://brian-mountainman.blogspot.com/2023/01/the-distribution-of-shap-granite.html

Bearing in mind that most far-travelled erratics will have followed zig-zag routes over the course of several glacial episodes, how far to the north might the ice divide have been located during Wolstonian and Anglian glaciations, and possibly even further back in time?

Well, if we look at landscapes rather than glacial deposits, it's clear that southward-flowing ice has played a powerful role in landscape formation in the southern part of the Western Isles.  Loch Fyne itself occupies a long and well defined glacial trough cut by ice flowing broadly southwards.  The Sound of Jura was also probably a glacial transport route.  So too the Firth of Clyde.  So too Loch Awe.  The Firth of Lorn and Loch Linnhe, following roughly the route of the Great Glen Fault and separating the North West Highlands from the Grampian Highlands, are more difficult to interpret because of the powerful structural influences at play; but it does look as if this elongated deep trough once carried ice flowing south-westwards.

So maybe, in trying to explain how erratics from the Western Isles found their way into the path of the Irish Sea Ice Stream -- and were then carried away far to the south -- we have to look at a very long history of glacial episodes, with some entrainment and transport related to local glaciations of the Scottish Highlands (involving local valley glaciers and outlet glaciers from the Scottish Ice cap, and other episodes of erratic transport related to glacial maxima and the work of the British and Irish Ice Sheet.  Sequence of events still to be worked out.......

There are two further matters to be considered:  isostatic and eustatic interactions, and changes in oceanic circulation which can be related to glacier expansion and contraction. These are important if we are to get to the bottom of the "ice rafting" issue.

The ice shed area shown on the map at the top of this post was (at least in the Late Devensian) the area of thickest ice and therefore the area of greatest post-glacial isostatic recovery.  Raised beach ridges occur in many locations (for example near Loch Tarbert of the Isle of Jura) up to altitudes of c 40m.  The raised beaches on Rum and Muck occur up to c 30m, and the highest beach is found at Arisaig in Lochaber, at 45m asl. 

Raised beach ridges at Loch Tarbert on Jura

Another raised beach sequence on Jura

Isolated raised beach remnants resting on an old rock platform near Glenbatrick on the south shore of Loch Tarbert, Jura.  (Oblique satellite image from Google Earth)

The most prominent raised beach ridges may coincide with short-lived RSL stillstands and minor advances of glaciers feeding from the Scottish Ice Cap -- but this sequence of events has still to be worked out.  It's believed that someof the glacier advances involved floating glacier snouts and short-lived calving episodes -- so there might have been some "ice rafting" of erratics as envisaged by some geomorphologists.  Sea level at the time was approxinately at -60m m -- so any erratics transported southwards cannot have been dropped on modern shorelines far to the south.

In any case, extensive southwards iceberg drift seems very unlikely, since the prevailing oceanic  current direction on the western coasts of Britain -- driven by the Gulf Stream and the North Atlantic Drift -- was broady northwards, not southwards.  Even if there was a weakening of the North Atlantic Drift and a reduction in the force of the westerly winds at the time of the Loch Lomond Stadial, it is most likely that any icebergs carrying erratics into Scottish tidal waters will have melted and dropped their loads quite close to their places of origin, as happens today in the Greenland fjords.

We now know quite a bit about the Younger Dryas (Zone III) or Loch Lomond readvance, and we can assume that similar conditions prevailed at times in the Early and/or Middle Devensian prior to the massive expansion of the BIIS and the development of the Irish Sea Ice Stream. 

The blue area on this map indicates the extent of the Loch Lomond Stadial in Scotland

Bickerdike, H.L., Evans, D.J.A., Stokes, C.R. and Ó Cofaigh, C. (2018), The glacial geomorphology of the Loch Lomond (Younger Dryas) Stadial in Britain: a review. J. Quaternary Sci., 33: 1-54.

https://doi.org/10.1002/jqs.3010

This brings us back to the matter of ice rafting and the Devon and Cornwall coastal erratics.  Could ice floes have carried some of them all the way from the Western Isles, through the North Channel and across Cardigan Bay at a time when relative sea level was more or less as it is today?  As indicated above, I can see no set of circumstances in which that was possible.  There are abundant dropstones and sand and gravel layers in the glacio-marine sediments on the bed of the Celtic Sea, but all are connected to the the advance of the Irish Sea Ice Stream ice front prior to 26,000 years ago and to its retreat between 26,000 and 20,000 years ago -- at a time when relative sea level was probaly around -130m.  Towards its outer edge the ice front was afloat, but that was at least 200km away from the tip of Cornwall.

The ice rafting hypothesis really is a non-starter.  So the "western Scottish" erratics must have been derived from very ancient glacial deposits, and they must all have had very complex histories of glacial entrainment and transport.

 

The bluestones and their "quarries" -- some forthright views from Peter Kokelaar

One of the figures from Peter's blog.

I have been following up some very interesting material relating to the glaciation of the Gower, and have looked again at Prof Peter Kokelaar's blog.  

https://kokelaargower.com/

It's a treasurehouse of field observations and new data, summarising the contents of his book called "All our own Water" and adding much new material.  There are two blog posts that are of particular interest:

https://kokelaargower.com/stonehenge/

https://kokelaargower.com/towards-stonehenge-the-anglian-glaciation-of-gower/

Many of the points made in Peter's posts are very similar to the points I have made repeatedly on this blog and in my published papers  -- but I had forgotten how forthright some of his language is! 

Quote: 

"Many people will be aware of a long-running, media-fuelled ‘debate’ regarding the delivery to Stonehenge of a suite of rocks – the so-called bluestones – most of which certainly originated in Pembrokeshire. I shall not engage with the negative elements of that ‘debate’, which rather uncompromisingly set human transport against glacial (erratic) explanations. I do, however, briefly explain what seems reasonable to believe and might just nudge the reader towards a possible half-way house....."

Most of Peter's critical scrutiny of the literature occurs in the article entitled "Stonehenge" -- and in spite of attempting great restraint, he cannot resist (and who can blame him?) some choice phraseology! On the bluestone debate he refers to "a jumble of confusing claims, counterclaims and manifest nonsense, with a good measure of misleading media hype thrown in....."

Quotes:
"..........the ‘debate’ has involved somewhat alarming instances of serious subjectivity and media hype unlikely to promote the lay person’s trust in ‘expert opinions and methods’, probably to the contrary."

".........when all of the claims for human transport are stripped away for being without any foundation, ice is the only obvious agent, even if the last reach of it is not obviously or unequivocally recorded. Largely because of the media hype, which persistently favours the “extraordinary human endeavour”, ice transport currently gets practically no mention (e.g., the BBC Countryfile on Stonehenge of 14th December 2025 and the Channel 5 “Stonehenge: Secrets of the new stone” of 3rd March 2026), but that is misleading. Ice transport warrants the light of reasonable consideration."

"........we will recall some of the media’s misdirected presentations of the human transport view as if it was well supported by archaeological or scientific facts. This has been a bizarre distraction at least, if not damaging."

"There has been a strong tendency to interpret all fragments of monolith stone types as reflecting ‘dressing’ and accidental distribution by human hands and thus to refer to them as ‘debitage’. This might be justified in the vicinity of the monuments, but the interpretation potentially involves circular reasoning."

"Motivation for the “stupendous feat” in human transport has always been a problematic weakness in the case, earlier attributing fantastic reasons like magical powers or sonic properties to the stones, or later mistakenly claiming reverence for them in sites of previous circles that then acted as sources for removal and transport (e.g., Parker Pearson et al. 2021). Fantastic claims, including inference of active quarrying to produce the stones at rock outcrops that are actually typical of natural jointing, weathering and collapse, are now, with sensible geology and geomorphology, and with robust geochemical evidence, thoroughly debunked. So, no quarries and no uprooting of former monuments (Bevins et al. 2022; John et al. 2015; John 2025)."

On the Boles Barrow spotted dolerite boulder: "However, the range of convoluted and contradictory claims made through time, not helped by the boulder being temporarily ‘lost’ and including the suggestion that it was transported to Stonehenge and then stolen for a garden ornament (subsequently refuted), is astonishing and mind-numbing."

"There is not a shred of evidence that humans transported any ‘bluestones’ all the way from Pembrokeshire to Stonehenge. The human-transport view was initiated with HH Thomas (1923) and thereafter centred on the lack of spotted dolerites in the erratic trail beyond Pembrokeshire, plus the seeming absence of evidence of ice movement onto Salisbury Plain. The supposed quarries and previous-monument sources have been disproved and the bizarre embellishment concerning the transport by cattle similarly is unwarranted."

On the so-called bluestone quarries: "........nothing about those virtually pristine igneous rock outcrops could lead a field geologist to consider them anything other than naturally formed, including their aprons of fragmental debris. .......... To ‘inform’ the BBC-viewing public that quarrying by humans broke out the pillars ready for transport at the very summit of a perfectly natural outcrop, is ridiculous "

"There are hundreds of perfectly natural outcrops of jointed dolerite like this dotted throughout upland Britain, some quite nearby too, and of course also abroad. Surely many thousands of years of freeze-thaw mechanical break-up cannot be overlooked? From this nonsense, ignoring simple natural processes and geology and by implication suggesting ancient quarry sites all over the country, there apparently can have been no scientific-editorial oversight and advice for the archaeologist(s). Gross mis-pleading like this, on a television channel that prides itself in distinguishing the truth, surely undermines simple enquiry and learning, undermines the credibility of actual experts, and, given the n-fold repetition of the BBC programme, is effectively misleading a host of people. Thankfully numerous sensible people have taken issue with the programme and the ‘quarries’ have been debunked and abandoned amongst aficionados, although the BBC continues the promotion."

"Despite objections made regarding the ‘quarries’ (e.g., John et al. 2015), there was no retraction while the focus shifted to removal and transport to Stonehenge of stones from pre-existing monuments (Parker Pearson et al. 2021)."

Regarding "The Lost Circle" TV programme: "...........the whole programme, with its intense and dramatic revelations of quarrying and removal from a former stone circle, proved to be spectacularly wrong. One might say that hindsight is a wonderful thing, but contemporary expert advice was always available and ignored, and the media show on what is known to be a topic of wide interest was an information disaster."

"The nonsense carried on. After the Altar Stone saga in 2024, in 2025..... there came another remarkable gem of mis-information." Regarding the claims made about a cattle tooth: ".......nothing supports these contentions, which are false and are sheer hype."

"The claim that the cow-tooth findings add to confirmation of the “theory” that cattle were involved in transport of the megaliths is udderly ridiculous. Apart from confusing theory and hypothesis in this media hype, the unjustified claims were disturbing as they came from the Press Office of the British Geological Survey; no sane geologist would support them. Actually, the original scientific report of the cow-tooth findings, in contrast to the hype, was quite reserved, acknowledging limitations to interpretations that should be borne in mind. What is it then, really, that causes decent science to be so compromised in the media? There certainly is cavalier ignorance on the part of media producers, whose driver seems to be promotion of viewing figures or sales… Honesty about the issues might have been more interesting and more stimulating of genuine interest… Some of the media nonsense is arrogant and insulting."

So there we are then......... I am clearly not alone in expressing concern about the pseudo-science being fed to the world by the the most vociferous part of the Stonehenge establishment.

Revisiting the GBG (Greatest British Glaciation) of western Britain

Suddenly everybody seems to be interested in the erratics on the shores of the Bristol Channel, which is great.  The above map, which I think I first published in 2017, becomes very relevant indeed.  There are of course many similarities between what I refer to as the GBG and the LGM (Last Glacial Maximum -- Late Devensian):

I'm dithering on the precise dating of the GBG  it might have been the Anglian (MIS 12) or it might have been one of the phases of the Wolstonian (MIS 6).  Then again, the maximum ice extent might  not be represented by a single ice edge -- if such a thing might indeed have been discernible on the ground surface.  The outer limit of this glaciation might have occured in different sectors at different times -- in other words there might have been asynchronous oscillations.

In any case I am increasingly convinced that the ice reached the Fremington / Croyde / Saunton area on at least two occasions.

Interestingly enough, in my map for the GBG I show local icecaps on Dartmoor, Exmoor and Bodmin Moor as being incorporated into a landscape dominated by glacier ice, permanent snowfields and intermittent snow-covered terrain.  And on my model glacier ice could have carried the Ramson Cliff erratic broadly northwards from a "Cornubian outcrop" as suggested by Daw, Madgett and Ixer......

The main problem with that is that it implies a dynamic northward flow of ice from the Dartmoor ice cap as envisaged by Prof David Evans and others at a time when there was no competing ice flow from the N or NW.  See this:

https://brian-mountainman.blogspot.com/2012/06/dartmoor-ice-cap.html

The glaciation of Dartmoor: the southernmost independent Pleistocene ice cap in the British Isles
David J.A. Evans, Stephan Harrison, Andreas Vieli, Ed Anderson
Quaternary Science Reviews 45 (2012) 31-53

https://www.researchgate.net/publication/258707211_The_glaciation_of_Dartmoor_The_southernmost_independent_Pleistocene_ice_cap_in_the_British_Isles

https://www.torsofdartmoor.co.uk/tor-page.php?tor=slipper-stones

David and his colleagues suggest that the ice cap was thin and sluggish, and probably incapable (even at the time of its maximum extent) of deep erosion and significant erratic transport.  The northward known extent of the ice cap was at c 460m asl, near the Slipper Stones in the West Okement Valley --  roughly halfway between Meldon Reservoir and the high peaks of Yes Tor and High Willhays.  That's almost 50 km from the Croyde-Saunton area.  And therein lies the problem.........  at the time of the GBG, the intervening area would have supported extensive connected snowfields, some of them permanent (in that they survived during the summer months) and some melting intermittently.  But we can see no glaciological scenario suitable for the transport of big epidiorite boulders.......  On the other hand David and his colleagues were referring to a Late Devensian ice cap on Dartmoor.  Might there have been a much larger, earlier glacier about which we currently know virtually nothing?  We have to admit that this is quite possible......

The other question which deserves attention is that of the parallel ice streams.  Geoffrey Kellaway suggested many years ago that there were several confluent  ice streams flowing into the Bristol Channel, including one carrying Scottish erratics and one carrying Welsh erratics.  I also explored this idea with Lionel Jackson in a 2009 journal article:

https://brian-mountainman.blogspot.com/2020/09/stonehenges-mysterious-stones.html

Nowadays I think I prefer the idea of a zig-zag movement of erratics over several glaciations. but we have not heard the last of this!

Could the Ramson Cliff erratic have come from Rosslare in SE Ireland?

In the discussion by Daw et al (2026) on the possible origins of the Ramson Cliff Boulder, there is a brief consideration of possible Welsh or Scottish sources, but no mention at all of the possibility that the erratic might have come from the coast of SE Ireland -- more specifically, near Wexford or Rosslare. That is a very peculiar omission, given that the petrological match between the boulder and the 'Rosslare Complex' appears to be far more convincing than the match between the boulder and the Cornubian Batholith rocks.

https://gsi.geodata.gov.ie/downloads/Bedrock/Books/Understanding_Earth_Processes_Rocks_and_Geology_Ireland/Chapter_02.pdf

THE ROSSLARE COMPLEX

The Rosslare Complex is divided into two major units; a group of grey gneisses, coarsely crystalline metamorphic rocks that are well exposed at Kilmore Quay, and a group of dark-green metamorphosed igneous rocks called amphibolites that are seen around Rosslare Harbour and Greenore Point.

(Note: the modern term "amphibolite" is applied to the rocks that are otherwise known as "epidiorite")

The gneisses typically have a banded appearance, in which pale-grey bands of the minerals quartz and feldspar are separated by darker bands rich in mica. These rocks are interpreted as originating as sediments, deposited as a succession of greywacke sandstones and interbedded mudstones. Several periods of metamorphism, under high temperature and pressure conditions deep in the crust, produced the present-day gneisses. In places, thin sheets of granitic composition were injected parallel to the banding in the gneisses. These suggest that particularly high temperatures caused partial melting of the sediments and re-injection of the melted rock as granite.

The metamorphosed igneous rocks are rich in a dark-green mineral called amphibole. They are the metamorphosed equivalents of gabbro and diorite. Although the relationship is not clear, these igneous rocks probably intruded the sedimentary rocks that later became gneisses.

Deformation and metamorphism of the Rosslare Complex were caused by the Cadomian Orogeny of Late Precambrian age, which also affected rocks in southern Britain and northern France. New minerals that grew in the rocks during metamorphism have been dated as 620 million years old, but the gneisses and amphibolites were both already in existence before this time and so were produced by an even earlier metamorphism.

A literature search throws up the point that there are significant greenstone and altered basic complexes in the Wicklow or Wexford areas that align with the path of the Irish Sea Glacier.  Other suggested possibilities are the St David’s area or part of the Gwaun Valley, both of which have basic igneous bodies, though their specific petrography would need to be matched to the erratic. The Bristol Channel Floor has known submerged outcrops of older Variscan basement which might also provide a match, though these are harder to sample.  But for the moment, let's go with Ireland..........

The unconsidered Rosslare case (~600 Ma): The Rosslare Complex (Wexford) is dominated by Cadomian/Avalonian zircon ages, with major peaks around 600–620 Ma. These zircons frequently show metamorphic "resets" or rims from the Ordovician (~480 Ma), reflecting the complex tectonic "squeezing" this region underwent.

The preferred Cornubian case (~290 Ma): Local greenstones associated with the Cornubian Batholith were formed or heavily influenced by the Variscan Orogeny. Their zircon populations are dominated by Early Permian ages.

The petrological match between the Wexford (Rosslare Complex) rocks and the Ramson Cliff erratic is much superior to the Cornubian match because it provides a complete explanation for the rock's ancient, stressed, and complex history—features that are largely absent or localized in the Devon greenstones.
While Daw et al  (2026) favour a local source to support a human-transport theory, the following four petrological reasons demonstrate rather convincingly why Wexford should be considered as a likely provenance:

1. High-Grade Metamorphic Fabric
The Ramson Cliff erratic is a foliated epidiorite/amphibolite, indicating a rock that has been completely structurally reorganized.  In Wexford, the Rosslare Complex is defined by its high-grade, ancient metamorphic rocks. Units like the Greenore Point Group (very close to Rosslare Harbour) consist of strongly foliated amphibolites that were "squeezed" during multiple major mountain-building events. This explains the deep-seated gneissose texture of the rock.  In Cornubia, most Devon "greenstones" are lower-grade greenschists. They are typically massive (lacking a strong fabric) or only weakly sheared. Finding a highly foliated amphibolite in Devon requires searching for very narrow, specific contact zones.

2. The Polyphase Tectonic Story
The erratic shows signs of multiple metamorphic events, with relict minerals overprinted by secondary ones. In Wexford, the Rosslare Complex shows a "polyphase" evolution. It underwent high-grade metamorphism in the Precambrian (~620 Ma), was overprinted in the Ordovician (~480 Ma), and was stressed again in the Variscan. This "messy" internal mineralogy seems to give a match for the erratic’s apparently complex history.  In Cornubia, the Devon greenstones generally show a single, clear Variscan metamorphic event related to the intrusion of the granites. They lack the "deep time" complexity and multiple layers of history found in the Irish basement.

3. Zircon Age Heritage
Petrological identification includes the age and condition of the mineral grains. In Wexford the Rosslare rocks provide a Precambrian (~600–620 Ma) signature. These zircons are often rounded and pitted, matching the "battered" appearance of the crystals in the erratic.   In Cornubia the rocks in question are primarily Variscan (~290 Ma). Even when they contain older cores, their primary "internal clock" is significantly younger.   The degree of recrystallization in the erratic appears more consistent with a rock that has survived 600 million years of history.

4. Geochemical Deep Fingerprints.

Trace element plots are used to identify the original tectonic setting of the parent magma.  In Wexford, the geochemistry of Rosslare's dark gneisses shows tholeiitic signatures consistent with ancient rifting or back-arc basins. This provides a distinct "DNA" that matches the erratic's trace element ratios.  In Cornubia, in contrast, while also tholeiitic in part, the Devon greenstones  show a stronger "continental arc" or "within-plate" alkaline influence, which creates a subtly different slope on
discrimination diagrams.

But, I hear you say, what about the lack of epidote in the Ramson Cliff Boulder, which Daw et al use as a key part of their analysis?  They say that if the boulder had epidote then a western British source would be feasible, but because it is apparently lacking in the one thin section analysed, then the Cornubian source is the only realistic alternative.

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

Quote from Daw et al, p 15-16:  Other than possible very fine-grained clinozoisite epidote group minerals are absent as are other distinctive secondary minerals including quartz, serpentine minerals, analcime and calcite. Their absence eliminates many altered basic rocks that crop out in western Britain.

.................The alteration of this rock,  notably the lack of epidote, is incompatible with it coming from South Wales (including the Preseli Hills altered dolerites), hence it cannot be a South Welsh 
glacial erratic. Similarly, the absence of analcime and  calcite eliminates other more northern Welsh localities. 

In addition, the petrography and metamorphic grade eliminate it from having a Scottish origin within the British Tertiary Igneous Province despite glacial erratics from that province (but only from the nearby Lundy Granite) being present on nearby Devon beaches. The known Scottish erratics found in  more southern English sites are all petrographically highly distinctive rocks (hence their recognition) 
with characteristic primary and secondary mineral assemblages not recognised in the boulder.

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

This is all very technical, and I am checking it out with Irish geologists.  Ixer (who wrote the petrographic description) seems to claim that epidote is always found in the altered basic rocks of South Wales, and that if the erratic hade come from North Wales it would have contained analcime and calcite.  He says that "petrography and metamorphic grade" rule out a Scottich origin -- but that is a very vague statement unsupported by hard evidence. If there is evidence, it should have been cited.   Also, I gather from Prof Peter Kokelaar that epidode is NOT ubiquitous in Caledonian Palaeozoic meta-basic rocks -- so to rule out Scotland as a possible source area on that particulat line of evidence would be unwise.  We are told by Ixer that the known Scottish erratics found in southern England are all "petrographically highly distinctive" -- but we are given no information to back up that claim.  The jury is still out.

But from the point of view of glacial geomorphology, a SE Ireland origin for the Ramson Cliff erratic makes perfectly good sense.  I know of only one other positively identified Irish erratic in the Bristol Channel arena -- namely the very hard 'white limestone' boulder found in glacial deposits at Court Hill which is widely assumed to have come from the Ulster White Limestone of County Antrim in Northern Ireland (Gilbertson and Hawkins 1978).  That provenance is entirey reasonable, given what we know about the ice movement directions of the Irish Sea Ice Stream during several glacial episodes.

Could ice have carried Irish erratics from the Rosslare coast out into St George's Channel for incorporation in the Irish Sea Ice Stream, and for transport up the Bristol Channel and onto the Devon coast?  The answer is YES.  That would not involve any provenancing gymnastics -- and is a much more likely scenario than that proposed in the latest article by Daw, Ixer and Madgett.

A provenancing link between the Baggy Point area and Northern Ireland would of course be supported by the biological content and geochemistry of the Fremington Clays and till exposures.  As reported by Gilbertson and Hawkins, Kidson, Stephens and many others, there are strong biological, geochemical and petrological 'markers' in the Fremington clay and till series that indicate that the deposits are not locally originated or derived, but are made of sediments brought in from the N, NW and W -- pointing to one or more incursions of Irish Sea glacier ice.  

Here are some of the maps with reconstructed ice directions in the Celtic Sea arena and the Bristol Channel.  Needless to say, the details are still being worked out -- not just for the older glaciations (Anglian and Wolstonian) but for the LGM as well.

One of my very old maps.  I have been playing with the idea of the Celtic Sea Piedmont Glacier for 60 years or more, and I still think it might explain a few features........

One of my more recent attempts to define the limits of the LGM in this area and the likely directions of ice movement at the time of  'peak glaciation'

One of the BRITICE maps, showing that at one LGM stage (or, more probably. during many stages) ice from the Irish Ice Cap flowed across Wexford and into the St George's Channel.  (Note that this map shows an ice-free corridor over most of Pembrokeshire -- a strange idea which is unsupported by hard evidence and which defies the laws of glaciology.)

POSTSCRIPT

No doubt we will hear more about the geological similarities / differences with regard to the Ramson Cliff amphibolite erratic and the metamorphosed gabbros and diorites of the Rosslare Complex.  But here is another useful contribution to the debate.  Paul Madgett has very kindly sent me through a photo of a large rounded boulder in a difficult location near Down End.  He says: 

 "..........it's on my listing of the larger local erratics in the 2nd edition of his "Cliffs of Saunton" booklet. As far as I am aware few others have even seen it, as it is very difficult of access and only at low spring tides - even then, for safety you need one of the more extreme low tides. Apart from the mention above, and in my 1987 paper, nothing has been published on it.  However, I was immediately struck by the tight folding of the gneissose banding, and thought of Carnsore Point.........."

As mentioned above, there are two rock "groups" in the Rosslare Complex -- the banded gneissses and the metamorphosed igneous rocks.  Could it be that we now see representative erratics of both types in the Croyde - Saunton area?

To repeat my earlier point -- we should not be surprised by the presence of erratics from eastern and south-eastern Ireland in the Bristol Channel arena.  Irish ice (ie ice from the Irish Ice Cap) flowed eastwards and south-eastwards on the western flank of the Irish Sea Ice Stream and added to its bulk. I would expect to find Irish erratics mixed with erratics from western Scotland, the Lake District, North Wales and West Wales on the Gower coast, the coasts of south Glamorgan, and the coasts of Cornwall, Devon and Somerset. 

See also: 

https://brian-mountainman.blogspot.com/2015/01/the-erratics-at-baggy-point-croyde-and_18.html

Six million views

 

An erratic boulder is a large stone that should preferably have

 been somewhere else.........

I have not kept my eye on the ball, but we have sailed through the six million mark.......  as I said when we went through the 5 million mark, a lot of hits nowadays come from AI bots.  But with AI, as with many otherc things, popularity breeds even more popularity, and the blog is now so well established that it is scanned all the time by bots looking for answers to a wide range of different questions -- ranging from glaciers to bluestones, and Stonehenge to Pembrokeshire and East Greenland to Iceland.   So I'll keep going as before, commenting on Stonehenge matters, scrutinising new publications, and contributing original new science on a range of landscape and Ice Age related themes.

Pythagoras Klippe -- one of the "great cliffs" of the world

 

Google Earth 3D image of the 4,500 ft Pythagoras Cliff, located on the outside of the final bend in the fjord before it opens out into Hall Bredning.  The fjord water here is about 4,000 feet deep, and the fjord wall passes downward beneath the surface without much change of gradient.  So this is not a true sea cliff cut by the processes of coastal erosion.  It should be compared with other great cliffs formed by glacial erosion.

I have been working on a new video about our kayak trip on Nordvestfjord in 1962, and I am increasingly concerned that the massive coastal cliff that towered above us on part of the journey has not got the recognition it deserves!  The cliff is almost 4,500 feet high  -- more than ten times the height of the highest cliffs in Pembrokeshire.

In my narrative I describe the cliff like this:

On the western flank of this upland plateau is the Pythagoras Klippe — at 4,500 ft, one of the world’s great cliffs. It was cut by the Nordvestfjord Glacier, and dominates the outer end of the fjord. The enormous cliff is so high that if you were to plonk Ben Nevis, Britain’s highest mountain, out in the fjord, you could stand on the clifftop and look down at the summit. It’s more than three times as high as the Empire State Building, and twice as high as the famous Pulpit Rock cliff in Norway. It’s also far taller than the famous El Capitan rock wall in America. The geology is similar to that of the Staunings Alps, with granite and other crystalline rocks.  But there are no clean climbing walls here — the cliff face is broken up by great chasms and fractures, and rockfalls are frequent. This giant, forbidding, lethal cliff stretches for about 4 miles, running almost north-south — and as we shall see, it plays a central role in our narrative.

To fully appreciate the scale of this cliff, we can compare it with some of the famous and spectacular cliffs in NW Iceland:

Haelavikurbjarg cliff in Hornstrandir is just 846 ft (257m) high -- so the Pythagoras Klippe is about 5 times as tall

The Latrabjarg cliff in Vestfirdir is just 441m high -- so the Pythagoras Klippe is more than three times as high

Because this wonderful cliff has been formed by glacial erosional processes (where the rate of downcutting and sediment removal vastly outstrips the periglacial and proglacial processes of cliff degradation) we need to see it as belonging in the same league as the high mountain climbing cliffs of the Alps, Himalayas and Andes.  Mount Thor on Baffin Island has a drop of 4,100 feet.  Mount Asgard also has a vertical drop of about 4,000 feet. Then we can think of Cerro Torre and Torres del Paine in  South America (about 900m or c 3,000 ft ).  In South Greenland there are several hugely impressive rock cliffs in Tasermiut Fjord.  There are endless lists of the "highest cliffs in the world" or "the most dangerous climbs in the world" ----but we won't get involved in those discussions.

Suffice to say that Pythagoras Klippe is one of the select group of coastal cliffs in the world that is more than 3,000 feet high.  I don't think it has been climbed, because it is too dangerous, with too many crumbling rock faces and rockfalls..... but who knows?  There are some crazy guys out there.......

Mount Thule

Mount Asgard

In the inner reches of Nordvestfjord is the Ingmikortilaq cliff (3,750 ft), first climbed by Alex Honnold and Hazel Findley in 2022.  Pythagoras Klippe is higher, and probably far more dangerous.......

Ingmikortilaq

By the way, the name "Pythagoras Klippe" is a strictly informal one, so it will not appear on any map.  The people of Greenland may already have a name for this cliff, and if so I hope it will be used to promote it as a place of wonder......

Daw's miraculous statistics are worthless

Two small igneous erratics found near the higher path on Baggy Point.  Altitudes c 45m and c 60m. These were in the view of Daw too high to be counted as low, and too low to be counted as high.  They were "rejected" becausee they have been moved at least once, and because they do not have "a secure geological context."   But does any free glacial erratic have a secure context?  They are called "erratics" for a perfectly good reason, and almost all of those on farmland will have been moved by farmers at some stage..........  (Photos:  courtesy Paul Madgett)

In the context of ongoing attacks on my integrity and competence, ex-Stonehenge tour guide Tim Daw likes to portray himself as a feisty defender of the truth. But in the welter of his recent publications dealing with the Devon coast he has become increasingly dependent upon AI bots. He has also corrupted statistical methods to make inconvenient erratics disappear and has invented more than 30 “phantom erratics” (all, purely by chance, at 5m OD) so as to boost his shoreline data set and to achieve his desired results.

It’s amazing what lengths some people will go to in order to create pseudo-scientific “proofs” for their rather wacky hypotheses. And it's also amazing — and more than a little sad — that they often get away with it…….

In the recent article by Daw, Ixer and Madgett much emphasis is placed on the supposed existence of just one “high level erratic” in the Baggy Point - Barnstaple area, referred to as the Ramson Cliff erratic. It’s seen as an outlier or an anomaly, with all other documented erratics lying on or around the altitude of the shore platform. That is a false representation of the situation, since there are abundant recorded erratics between 30m and 80m showing that glacier ice affected much of the local coastal environment. Undeterred, Daw asked Grok for “an independent analysis” of his own paper, and for a “Bayesian analysis” of the likelihood of human transport over glacial transport.” As ever with AI bots, Grok faithfully delivered what was expected by its master……...

Some other examples from Daw, who is currently on a mission to demonstrate to the world that active glacial ice cannot possibly have had anything to do with the erratics scattered along the coastal zone of Devon and Cornwall.

The Myth of Bristol Channel High-level Glacial Erratics (December 2024): Considers the lack of a "glacial imprint" on boulders and argues their placement is more likely due to residual weathering than glacial action. This is not a statistical study, but in supposedly analysing a list of “cited erratics” Daw simply decides that each of them is irrelevant because they are too low, or of the wrong rock type, or “non-glacial”, or lacking in cited evidence, or lacking in geological context. That’s absurd. The process is entirely subjective and lacking in any appreciation of glacial environments or processes.

Analysis of Claims Regarding High-Level Glacial Erratics (April 2025): Uses a quantitative list of erratics and their altitudes to disqualify them as evidence of an ice-sheet override. This is essentially the same article, but here published on Researchgate without any peer review. See the above comments.

ChatGPT on competing transport hypotheses (August 2025) Monthly Archive (specifically the AIC section): Includes a section where ChatGPT was reportedly used to put competing transport hypotheses into a statistical model comparison (AIC) to show that a non-glacial model better explains the body of evidence. This is a nonsensical exercise, based on biased data sets and observations fed into the AI model. Rubbish in, rubbish out.

The Statistical Improbability of a Ramson Cliff Glacial Erratic (October 2025): This post uses a table of "high-level" erratics to argue that their scarcity at specific altitudes makes a glacial origin statistically unlikely. The data set is completely unacceptable — Daw seems to have chosen some erratics from the literature and to have ignored others that were deemed inconvenient. He added several inland erratics from the Fremington area — all at 25m — while completely ignoring the records of other erratics in the sediments near Eastacombe up to 90m. Then he added “approximately 30 other foreshore erratics at 5m OD ”for statistical purposes” in order to bulk up his shore platform group! So he ended up with a synthetic data set. Malpractice. As far as we know, these additional erratics might not even exist. His graph of the elevations of 14 chosen erratics is also nonsensical.

Caution in Attributing the Fremington Clay Series (October 2025): Daw argues that the abundance of local Devon and Cornish erratics over far-travelled ones is "statistically consistent" with a local origin rather than a distant glacial source. Revised and expanded on 4 April 2026.   Daw gets into a frightful tangle over the altitude of the ice dam that held up a lake in the Fremington area, and seems to assume, bizarrely, that the surface of the lake was at the same altitude as the varved lake deposits that are known in the literature, up to 35m OD. That implies a lake surface level at 65m, or even higher. He goes out of his way to avoid referring to any of the Fremington deposits as glacially deposited, and misrepresents the views of those who have described the Fremington till in detail. He mentions fluvioglacial deposits at c 55m OD and still insists that the Ramson Cliff erratic, at c 85m OD had nothing to do with glaciation.

In these articles, and others, Tim Daw seeks to use statistics to “prove” that the coastal erratics around Croyde and Saunton are ice-rafted, and that the Ramson Cliff erratic, at about 85 m above sea level, is an outlier that cannot possibly have been transported by ice. It all looks terribly impressive and scientific, until you realise that his methods are the stuff of statistical nightmares……...

I’m no statistician, but I’m not stupid, and it is obvious from the outset that Daw's methods are corrupt. What we see is a classic case of selection bias (called “data scrubbing” in the trade) to achieve a predetermined result.

For example, in his convoluted attempts to prove that the Ramson Cliff boulder is an outlier, these are the statistical red flags:

1. Sampling Bias (Cherry-Picking)
Daw chooses to ignore or exclude the 45m and 60m erratics near Baggy Point (recorded by Berry and Madgett) on the grounds that they may have been moved and that they do not have “a secure geological context”. That immediately introduces subjectivity and selection bias. You could argue that every erratic in a farmed landscape has probably been moved at some stage, and that every isolated boulder on the shore platform has also been moved by the waves — and that they should all be eliminated from the study on that basis………) Daw also chooses to ignore the 90m till at Eastacombe, although it is recorded by the BGS and is known from borehole records to contain erratics. So Daw is deliberately "truncating the distribution” by eliminating all boulders that he deems to refer to as “contested” and including all those that he deems to be “uncontested”. That is, to put it mildly, completely unprofessional. Further, if you consciously remove all data points between 25m and 75m, the 80m point will mathematically appear to be an extreme outlier. This is not a discovery; it is a result of the filtering or sampling process itself.

2. Circular Reasoning (Begging the Question)
Daw labels all high-level stones as "contested" or "anthropogenic" because they don't fit the low-level ice rafting model, and then uses that "cleaned" model to prove high-level glacial erratics don't exist. This is a "Self-Fulfilling Prophecy." You cannot use a model to validate the exclusion of the very data that would disprove the model.

3. Arbitrary Binning
Creating a “shoreline group” (clustered around 5–25m) and a “high level group" based on some arbitrary altitude, rather than assuming the presence of a continuous gradient, is known to statisticians as “arbitrary binning."  This creates a false dichotomy. In nature, glacial deposition follows strict principles (not yet fully understood) but apparently random within a range. By forcing the data into two bins and ignoring the middle, Daw is guilty of manufacturing a "gap" that does not exist in the raw geological or geomorphological record.

4. Small Sample Size & Power
By using a small pool of "verified” or “uncontested” surface boulders of certain dimensions and shapes, while ignoring the presence of inconvenient boulders and cobbles found in exposures and sub-surface boreholes at Fremington and elsewhere, Daw reduces the “statistical power" of the study. A study that ignores the most robust institutional data (BGS) in favor of a curated or self-selected list of surface stones is prone to a fundamental error—falsely identifying a natural or expected occurrence as an anomaly or outlier.

5. Confirmation Bias in Bayesian Analysis
Daw uses Bayesian Inference to claim a high probability of human transport in the case of the Ramson Cliff erratic. Bayesian outcomes are highly sensitive to initial assumptions. If your starting assumption is that ice never reached 80m in the Baggy Point area, the mathematics will always tell you an 80m stone is an anomaly. “Rubbish in, rubbish out…………." 

Terribly impressive, until you realise that it's all manipulated nonsense.......

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

In short, Daw is misrepresenting his selection criteria, and pretending that he is telling us something important about the natural population of erratics in the Baggy Point - Barnstaple area. It all looks terribly impressive and very scientific, but it is essentially garbage.