Erratic dispersal modelling -- the Irish Sea Ice Stream

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. BradleyVersion of Record online: 15 May 2025

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

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

ABSTRACT: Glacial erratics are geologically distinctive rocks transported away from their source area by ice sheets and deposited in lithologically different bedrock areas. They have attracted much scientific curiosity with >24 000 observations across the British Isles. A common misinterpretation is that they took a nearly direct line of transport from source to resting position, neglecting to change ice flow directions during ice sheet growth and decay. To rectify this, we sequentially modelled erratic time‐space trajectories at 1000‐year timesteps using ice flowlines in an empirically constrained ice sheet model simulation to predict erratic deposition areas. We addressed the processes of entrainment and deposition by combining all potential trajectories into a single footprint of possible locations. Erratic dispersal is predicted for three geologically distinctive lithologies; Shap Granite of Northern England, Galway Granite of Ireland and the Glen Fyne igneous complex from Scotland. The footprint of predicted trajectories compared against 1883 observations of erratic locations was found to successfully explain 77% of the observed erratics. Most erratics were explained by flow directions during ice retreat; however, some required earlier ice divide shifts to produce potentially long‐duration, multiphase pathways. Our analysis demonstrates the possibility of explaining many erratics without explicitly modelling the complex processes of entrainment and deposition.

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This is an interesting paper in which the authors test a modelling exercise agtainst "ground truthing" for the distribution of erratics from three different bedrock sources -- one in Ireland, one in northern England, and one in western Scotland.   Figure 4 (at the head of this post) shows the latest version of the streamlines of the Irish Sea Ice Stream as far south as the Bristol Channel, predicting where distinctive erratics from the Loch Fyne igneous complex might be found.

See this post:

https://brian-mountainman.blogspot.com/2024/08/possible-altar-stone-sources.html

and this:

https://brian-mountainman.blogspot.com/2024/08/in-praise-of-ailsa-craig.html

This new work has a bearing on the Altar Stone debate -- including the possibility that it might have come from one of the ORS sandstone outcrops in the Midland Valley of Scotland or the Southern Uplands.   We already know a lot about the distribution of Ailsa Craig erratics -- this new work suggests that other erratics from much further north -- around Loch Fyne -- might also have found their way into the Bristol Channel and onto the coasts of SW England.

The joy of quartz

An old wall on Parrog, Newport, topped with heavily abraded quartz boulders

A new wall on the other side of the road, also topped with abraded boulders -- in this case probably recycled........

On one of our walks on the Parrog in Newport, the other day, I was reminded of the fact that people just love quartz boulders and cobbles. In and around Newport they are used all over the place, mostly as wall toppings.  They are for the most part not "fresh" and angular, with sharp edges, but rounded or sub-rounded.  They have been for the most part collected from either beaches in the vicinity ( to the west of Parrog) or from old glacial and fluvio-glacial deposits.  Before the days of effective field clearance, the ground surface was littered with quartz boulders...............   

These boulders have not been used for ritual or religious purposes, or even for the enhancement of status  -- they have been used simply because they are ornamental and nice to look at.  They have not been "fetched" from quartz quarries or sacred places.  It's all about aesthetics...............

This brings to mind our discussions on this blog about the famous (infamous) quartz "facade" at Newgrange, made of boulders and cobbles rescued from the spoil when the work of "restoration" was under way.  Whether or not there was originally a quartz facade, most authorities seem to accept that the white boulders (some with cream colouration, some greyish, and some reddish) were used simply to enhance the appearance of the mound.  As I have argued before, the argument that the boulders were quarried from 60 miles away, in the Wicklow Hills, has never been supported by convincing evidence.  It;s much more likely that the boulders were simply collected up in the local landscape around the Newgrange site.

http://www.carrowkeel.com/sites/boyne/newgrange2a.html

Work in progress on the Newgrange site.  A perfect quarry.  Whitish quartz boulders were picked out specifically for the purpose of creating the white facade.

Fluidity and viscosity

 I came across this image of flowing lava in an eruption on Hawaii in 2010.  Lava is extremely hot, becoming more viscous as it cools down.  The fun thing is that ice behaves in a similar fashion when it is flowing at an optimal rate -- but then it ceases to flow when the temperature rises, so that melting, and the conversion to water, destroys the flow structures which are not dissimilar to those of flowing lava.

Lava flows, and glaciers, tend to seek out depressions and fill  them -- subsequently overflowing via cols or low points in the depression rims.

Most of the movement of ice occurs through internal deformation and basal sliding -- but there is also brittle fracture which results in crevasse formation, and the creation of shear fractures and thrust planes partucularly in cold or polar ice.

Here are a few images of flowing glacier ice in Arctic Canada and Alaska:

I have seen similar ephemeral features on small glaciers in East Greenland.

On smooth igneous rock surfaces

 This is one of my favourite photos, taken on the granite coast of Brittany, not far from Roscoff.  Look at the lovely smooth rock surfaces. This reminds us that not all smooth surfaces are glaciated or wave washed. Here we are about 20m above sea level, on a coastline that was not (as far as we know) ever affected by glacier ice during the Quaternary.

It is sometimes difficult to be sure of the origin of "glaciated slabs" unless there are striae or glacial grooves present.  On rock surfaces that have been exposed for thousands or even millions of years, a multitude of processes can operate in smoothing off sharp edges, rounding corners and eliminating rocky projections.   The age of a rock surface has a great deal to do with how it looks, as any desert geomorphology textbook will tell you........

Mind you, if a lump of rock in West Wales (or for that matter on Salisbury Plain) is genuinely derived from a Neolithic quarry, around 5,000 - 5,500 years ago, it sure as eggs would not look like this:

Stone 37, courtesy Simon Banton

The increasingly bizarre defence of Bluestone Orthodoxy

Our old friend Tim Daw continues his one-man defence of the bluestone quarrymen, mostly on his blog, which I ignore for most of the time.  He clearly likes to follow my utterances and writings, and posts rather frequent and very aggressive ripostes, while  in some cases being very reluctant indeed to mention me by name.  Weird, that.  Maybe he is afraid I might sue him..........  he need have no concerns on that score, since (unlike some of his cronies) I actually believe in the merits of open academic debate.

But the one-man hit squad is now behaving in a way which can only be described as bizarre.  First, back in March he hired an anonymous "referee" to review my two papers on the Limeslade erratic, and published it on his blog, here:

https://www.sarsen.org/2025/03/peer-reviewing-john-2025.html

Anonymous peer reviews in circumstances such as these are of course completely worthless, and I refuse to engage with this one.  If a reviewer does not wish to publish his / her name alongside disparaging and insulting comments, why should anybody take them seriously?   Shame on him / her for taking part in this grubby little stunt.  Maybe Tim wrote the review himself in spite of denying that he had anything to do with it?  Maybe it was written by a committee of aggrieved academics (Ixer, Bevins and Parker Pearson come to mind) and then put in the public domain with the pretence that it represented the opinion of somebody who is an "independent expert" in the field?  Who knows what goes on in the shadows..........

Then in April 2025 Tim published an anonymous rant entitled:  "A Critical Review of "Carn Goedog on Mynydd Preseli Was Not the Site of a Bluestone Megalith Quarry": Another Glacial Fantasy Masquerading as Scholarship."

https://www.sarsen.org/2025/04/a-critical-review-of-carn-goedog-on.html

Again there was no mention as to the name of the author, who spat out a great deal of  bile beneath a cloak of anonymity.

Then Tim wrote a riposte on the matter of far-travelled Bristol Channel coastal erratics, referring to my Limeslade erratic paper published in QN 162 (June 2024).   Tim's piece was clearly designed to show that the "high level erratics" cannot have been carried by glacier ice but must have been transported on ice floes and carried uphill by human beings.  (The ice floe transport idea is of course also promoted by James Scourse and others in previous publications.)  The latest blog post is here:

https://www.sarsen.org/search?updated-max=2025-04-21T13:49:00%2B01:00&max-results=7&start=7&by-date=false

and it refers to an "important article" -- written modestly by himself -- on the Researchgate web site:

https://www.researchgate.net/publication/390953838_Critical_Analysis_of_Claims_Regarding_High-Level_Glacial_Erratics_in_the_Bristol_Channel_and_the_Implication_for_the_Glacial_Transport_Theory_of_Stonehenge_Bluestones?channel=doi&linkId=6804ba5cdf0e3f544f42e7c7&showFulltext=true

This is referred to as a "preprint", which means of course that it has not been reviewed or assessed for quality.   Suffice to say that it is a very strange piece of work, filled with misunderstandings and unwarranted assumptions and obsessed with the 100m contour.  Boulders and erratic fragments found over that altitude are deemed to be worthy of consideration, and erratics beneath it are discounted as irrelevant.  The important work of Madgett, Inglis and others is cited but effectively discounted, as is my article in QN 164 (February 2025).  The reference list is strongly biased and selective.  There is no mention of the work of Bennett et al (2024), who are in no doubt that the ice of the Irish Sea Ice Stream did affect the coasts on the southern shore of the Bristol Channel.

 I just cannot understand what Tim is on about here;  why is he so obsessed with demonstrating that flowing glacier ice did not affect the Bristol Channel coasts, when everybody knows that the evidence demonstrates otherwise?

Then, also in April,  Tim published three further reviews of my papers on Rhosyfelin, Carn Goedog and Waun Mawn:

https://www.sarsen.org/2025/04/a-review-of-brian-johns-2015-paper.html

https://www.sarsen.org/2025/04/a-review-of-brian-johns-2024-paper.html

https://www.sarsen.org/2025/04/a-review-of-carn-goedog-on-mynydd.html

No authorship is revealed for any of these weird critiques, and so they can be dismissed without further ado.  They might of course have beern generated through some AI programme, but that does mot make them any more meaningful, since we do not have any idea what prompts and editing adjustments there might have been, and we have no sight of any of the reviews that might have been commissioned from the same AI source for articles written by MPP and his team.  Now THAT would be an interesting exercise...........

The AI question comes up again in a very strange article published in Researchgate with the joint authors shown as Tim Daw and "Groc":

https://www.researchgate.net/publication/390662999_A_Review_of_Brian_John's_Three_Papers_on_Bluestone_Quarrying_Sites

It turns out that Groc is an AI bot, and that his (???)  contribution was prompted and edited by Tim. In other words, it is a meaningless exercise which has no value as a piece of independent and unbiased research.

What on earth is this article doing on the Researchgate web site?  I am contacting the moderators to check out what their policy on AI might be, and to ask for the removal of something that makes no pretence at all to represent original scientific thought or process.

So there we are then.  Tim's mission of character assassination continues at an accelerating pace, but at least he has the good grace to use his own name.  But it's sad to see that he now has to resort to AI to do his thinking for him.  As for those who use Tim's blog site to  publish abusive rants directed at me personally while sheltering beneath a cloak of anonymity, they are beneath contempt.  And shame on Tim for allowing it to happen. 

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Another top Pembrokeshire erratic

 

 

This is one I forgot about -- at Martin's Haven, on the lane leading down to the departure point for the Skomer boats. 

It's an inscribed stone,  and it looks to me like an Ordovician dolerite erratic from the St David's Peninsula.  It may be water worn, but to me it looks like just another glacial erratic.........

Newport lecture, May 22nd