The Mystery of the Ramson Cliff Boulder

Chapter One: A Curious Find on Baggy Point

It was a splendid summer holiday and the Famous Five—Julian, Dick, George, Anne, and Timmy the dog—were staying in the charming village of Croyde, on the rugged North Devon coast. The Bristol Channel sparkled under the sun, and the cliffs of Baggy Point beckoned for adventure. One morning, as they rambled along the crest above Ramson Cliff, Timmy bounded ahead, sniffing furiously at a large, angular boulder on the coast path.

The "high level" epidiorite erratic on Ramson Cliff (photo: Paul Madgett)

 

“Gosh, what’s this?” exclaimed George, running her hand over the rough epidiorite surface. “It’s not like the smooth stones on the beach below!”

Julian, ever the leader, examined it closely. “It’s jolly odd for such a big rock to be up here, all alone. It’s the only one high above sea level on this coast, I’d wager!”

Anne, peering over his shoulder, wondered if the boulder once stood upright, as if placed deliberately. “I think it has been recently moved here. It looks like it was once upright, like a beacon or a rubbing stone. Maybe it was an ancient standing stone. I must find out all about it.”

Dick, always ready for a mystery, grinned. “I bet it’s a clue to something! Let’s call it the Ramson Cliff Boulder. Perhaps it’s a forgotten treasure marker!”

Julian stood up deep in thought. “In my detective books it is always important that the evidence is not moved before it is examined. I’m reading a jolly good story now where a handkerchief was taken to the police station and it couldn’t be used as evidence to show that the missing lady had been on the bus because it wasn’t recorded in its original position. I bet it’s the same for this stone.”

Timmy barked in agreement, and the Five decided to investigate.

Chapter Two: Clues from the Past

The Five headed to the village library, where they met Mrs. Madgett, a kind geologist who, with her husband Paul, had recorded the boulder in 1969 for the Quaternary Newsletter (Vol. 14, November 1974).

She explained that there was an old man in Wales who was convinced that this boulder showed that there was a glacier in the last ice age and if it reached up over the cliff to drop the rock it then went onto to Stonehenge and dropped more rocks there.

“Gosh,” said Anne, “if he thinks this one rock proves all that, it is really important we get to the bottom of this mystery.”

 Mrs Madgett pulled out an old piece of paper which was the report of the discovery:

 

“It was hidden from the coast path and by a stone wall to the south,” Mrs. Madgett explained. “But in the early 1970s, Farmer Tregellis ploughed the field, dislodged it, and dragged it to the edge by the Coast Path. Now it’s half-hidden by gorse bushes!”  The boulder had “always been there,” (*) and he hadn’t moved it before because it felt like part of the land.

But the Five were puzzled. Why had there been this boulder, unlike any other, in the middle of an eight-acre arable field called Ramson, where stones had been cleared to build walls?

George used her Ordnance Survey map to work out where it was spotted in the field, she was a whizz with maps. To help the others she then marked it on an aerial photo.

 Julian frowned. “If it was moved, how do we know where it really came from? Could it be a prehistoric standing stone, like the one near Putsborough?”

Mrs. Madgett nodded. “That’s one idea. The Putsborough stone is local sandstone, but this boulder’s rough and angular, not wave-worn like the erratics at Saunton Down End or under Saunton Cliffs. Perhaps it was raised upright long ago,  dragged up from the shore, and the rough bits ae where it got damaged when it was moved.”

Dick’s eyes lit up. “What if it’s a beacon marker? I found an old map in Early Devon Maps (Ravenhill & Rowe, 2000, pp. 52–53) that marks ‘Cride Beacon’ right near this spot!”

Anne shivered with excitement. “A beacon for pirates or smugglers, maybe?”

George, practical as ever, wasn’t convinced. “Let’s check proper records. If it’s important, it should be on Ordnance Survey maps or old photos! It should show up if it was in the middle of the field all those years ago.”

Chapter Three: The Missing Map Marks

The Five pored over Ordnance Survey maps (National Library of Scotland) but found no trace of the boulder. They examined a 1940s aerial photo (Historic England) and another from the North Devon AONB NMP Project (Knight et al., English Heritage Project 6083).  Nothing!

Julian found a really old map in a dusty drawer. “Look, even the 1839 Georgeham Tithe Map  doesn’t show a boulder.”

“That’s dashed queer,” said Julian. “A boulder this big should’ve been noticed!”

Dick scratched his head. “Unless it was moved there later. Maybe it’s a boundary stone, like the one in Mearlands field nearby!

The Five checked the Devon and Dartmoor Historic Environment Record (Heritage Gateway), which listed a boundary stone (HER number MDV61368) in Mearlands, a field named from the Anglo-Saxon gemoere (boundary). The tithe map showed strips marked by “mearstones.” Could their boulder have been dragged from Croyde Bay, as suggested by Stephens et al. (1998) in The Quaternary History of North Devon and West Somerset (JNCC), It is possible, however, that this boulder was dragged up from Croyde Bay to act as a boundary marker”?

Chapter Four: A Wartime Twist

The Five’s investigation took a thrilling turn when they met old Mr. Penrose, who remembered Baggy Point during World War II. “The American Army took over in 1943,” he said, sipping his tea. “They turned it into an Assault Training Centre for D-Day, bulldozing hedges and walls for company-sized exercises with live ammunition!” (The American).

George’s eyes widened. “Gosh, they might’ve moved the boulder or disturbed the field!”

Anne nodded. “Maybe that explains why it’s not in old records. If it was moved during the war or later, it’s not in its natural spot!”

Julian summed up wisely, “We must remember that sometimes, things moved by hands or history can fool even the keenest detectives. It’s why original position and context matter so very much.”

Timmy woofed, as if agreeing. The Five realised the boulder’s history was muddled by human activity—farming, boundaries, and wartime changes.

Chapter Five: Solving the Mystery

Back at Ramson Cliff, the Five sat by the boulder, now near the Coast Path, and pieced together their clues. Julian summed up: “It’s not on maps or photos, so it wasn’t always here. The field was cleared for farming, and there’s a boundary stone nearby. The war disturbed the area, and the boulder was moved in the 1970s. It’s not a glacial erratic with a clear geological story.”

Dick added, “It might’ve been a standing stone or beacon marker, but we can’t prove it. It’s more like an artefact of human meddling! That’s the answer.”

George patted Timmy. “Well, we’ve solved it, even if it’s not pirate treasure. It’s a jolly good mystery!”

Anne smiled. “Let’s have a picnic to celebrate—ginger beer and all!”

As the sun set over Baggy Point, the Five enjoyed their picnic, content that the Ramson Cliff Boulder, though not a glacial clue, was a splendid adventure.

 

The latest on Stonehenge Sarsen Sources - July 2025

In 2020, a landmark geochemical study by Nash et al. proposed that most Stonehenge’s sarsen stones, came from West Woods, about 25 km to the north in the Marlborough Downs. Using portable X-ray fluorescence (pXRF) and Bayesian PCA of trace elements such as zirconium and niobium, they tied 50 of the 52 stones to a geochemical signature matching this source. Among the most carefully matched was Stone #58, part of a central trilithon, sampled in 1958 via the now-famous “Phillips Core.”

The latest of a series of papers in the journal Archaeometry, debating the interpretation of geochemical data and its implications for the monument has just been published. This exchange highlights the nuances of scientific provenancing: data can be reanalysed differently, leading to conflicting conclusions. To clarify the sequence of claims and counterclaims chronologically, based on the provided documents and the broader context.

The Original Claim: Nash et al. (2020)

• In a landmark study, David Nash and colleagues used portable X-ray fluorescence (pXRF) to analyse 52 sarsen stones at Stonehenge, taking multiple readings per stone. For Stone #58 they also analysed the sample of it, the pXRF matched the stone to 49 other stones so they could use the sample as being representative of them.
• They also sampled sarsen outcrops from 20 potential source areas across southern England.
• Using Bayesian principal component analysis (BPCA) on immobile trace elements (e.g., normalised to zirconium to account for silica dilution during rock formation), they concluded that 50 of the 52 stones share a common chemistry, likely originating from a single source: West Woods.  A variant of PCA that incorporates prior information, BPCA is beneficial in geological provenancing because it handles missing data and reduces dimensionality while preserving meaningful geochemical trends.
• Two outlier stones had different signatures, suggesting multiple sources overall.
• This implied organised transport from a concentrated area rather than scattered local boulders.

The Challenge: Hancock et al. (2024)

• R.G.V. Hancock and team reinterpreted the same dataset from Nash et al. (2020), focusing narrowly on Stone #58.
• They used absolute elemental concentrations (not normalised) and selected different discriminating elements (e.g., Ga, Fe₂O₃, Hf).
• Their analysis suggested the data do not definitively match Stone #58 to West Woods. Instead, they argued: “as a minimum, the Wiltshire sites of Clatford Bottom and Piggledene with West Woods a distant third, appear as potential sources of stone #58. None of these locations, however, has elemental concentrations from one up to three samples that would geochemically merge with those of the Phillips core samples.”
• They criticised Nash's choice of elements (e.g., Hf's correlation with Zr making it less useful) and highlighted issues like detection limits and data quality variability in the original dataset.
• Key point: They aimed to "replicate" Nash's findings but ended up questioning the certainty, emphasising that sarsen geochemistry can vary even within a single outcrop due to formation processes.

The Comment: Nash and Ciborowski (2025)

• Nash and T.J.R. Ciborowski respond directly to Hancock et al. (2024). They identify three main "problems" with Hancock's approach:
1. Use of absolute concentrations: Sarsens form through silica cementation, which dilutes trace elements. Nash argues for normalising data (e.g., to Zr, an immobile element) to correct for this; Hancock's raw data ignores dilution effects, potentially leading to misleading comparisons.
2. Selection of discriminating elements: Hancock used elements like Fe and Ga, which can be mobile during weathering or silicification, making them unreliable for sourcing. Nash prefers immobile ones (e.g., Zr, Nb, Th) that better reflect the parent sediment's signature.
3. Single-sample comparisons: Hancock compared single samples from outcrops to the Phillips' Core, ignoring intra-site variability. Nash used multi-sample ranges and statistical envelopes to account for heterogeneity in silcretes.
• They defend West Woods as the probable source, noting that Hancock's reanalysis overlooks petrological (rock structure) evidence and wider silcrete literature. They include figures showing how dilution affects concentrations and petrographic images of zircon grains.

The Response: Hancock et al. (2025)

• In the “Archaeometry - 2025 - Hancock - On Sourcing Stonehenge Sarsen Stone #58...", Hancock and colleagues counter Nash's criticisms.
• On absolute concentrations: They argue silica dilution has minimal practical impact in this dataset, as most samples are 97–100% SiO₂. They point to examples where lower-SiO₂ samples (silicified sandstones) show extreme variations unrelated to dilution.
• On element selection: Minor differences exist (e.g., Nash used Rb, Th, U; Hancock used Ga, Fe₂O₃), but Hancock claims these don't explain the divergent conclusions. They question Nash's use of Hf (due to its correlation with Zr) and Fe₂O₃ (not significantly different across high-SiO₂ samples).
• On single samples: Hancock clarifies they didn't rely on single samples for their own analysis but used Nash's provided data. They note anomalies in some Nash samples (e.g., from Monkton Down and Totterdown Wood) that don't fit neatly.
• They reiterate that the source of Stone #58 remains uncertain and call for re-examination of Nash's claims. They also touch on potential glacial transport of sarsens, adding another layer to the debate.

Further Support from Recent Studies: Harding et al. (2025)

A recent paper by Harding et al. (published online January 2025 in Proceedings of the Prehistoric Society) applies the same pXRF geochemical techniques to two outlier sarsens in the Stonehenge landscape: the Cuckoo Stone and Tor Stone, located on opposite banks of the River Avon.

Key findings:

• Both stones exhibit geochemical signatures statistically indistinguishable from the majority of Stonehenge sarsens, pointing to West Woods as their likely origin.
• They were probably transported and erected in the early Late Neolithic (early 3rd millennium BCE), contemporary with Stonehenge Phase 1 and about 400-500 years before the main sarsen structures.
• Visibility analysis shows the stones were intervisible and positioned to form a "planned portal" across the River Avon, integrating into the broader Neolithic landscape.

This study, co-authored by Nash and Ciborowski, reinforces the West Woods sourcing hypothesis and extends the timeline of sarsen movement into the Stonehenge area. It also counters ideas of local sarsen abundance by arguing geological conditions on Salisbury Plain were unsuitable for forming large boulders like those at West Woods.

• Unresolved Issues: Methodological debates persist, but glacial claims are a red herring. Future work might use advanced zircon dating or quarry surveys to confirm West Woods.
• Implications for Stonehenge: Human transport from West Woods implies Neolithic ingenuity. Dismissing glaciation strengthens this narrative, avoiding unproven shortcuts.

 

What to Make of It All?

This back-and-forth is classic academic discourse: science thrives on scrutiny, and geochemical sourcing is inherently tricky for materials like sarsen, which form in variable groundwater environments. Here's a hopefully balanced take:

• Strengths of Nash's Position: Their original study is comprehensive, using non-destructive methods on the actual monument and statistical rigour to handle variability. Normalising for dilution is standard in geochemistry, and West Woods fits archaeologically (it's a dense sarsen field, suitable for quarrying multiple stones).
• Strengths of Hancock's Position: Reanalysing existing data is valid and cost-effective. They highlight real issues like data quality (e.g., detection limits) and question over-reliance on certain elements. If dilution effects are overstated, absolute concentrations might suffice for this specific dataset.
• Points of Agreement: Both sides acknowledge sarsen heterogeneity and the limitations of single-sample data. They agree the dataset is valuable but interpret its nuances differently.
• Unresolved Issues: The debate centres on methodology rather than new evidence. Stone #58 might be from West Woods, but Hancock's work introduces doubt. Were all sarsens from one source? Future work could involve more sampling, advanced techniques (e.g., laser ablation ICP-MS for precise zircon analysis), or integrating geophysical surveys of potential quarries.
• Implications for Stonehenge: If West Woods is confirmed, it suggests sophisticated Neolithic logistics over 25 km. If not, it opens doors to multi-source models, perhaps involving local boulders. This doesn't upend Stonehenge's story but refines it, science is iterative.

The geochemical back-and-forth remains a healthy academic exercise, with Nash's normalised, multi-sample approach appearing more robust for silcretes, while Hancock highlights valid data limitations. West Woods still leads as the probable source for most sarsens, supported by archaeological fit (dense boulder fields for quarrying).

However, Hancock's invocation of glacial transport based on John (2009), positing that ice sheets might have naturally deposited sarsens near Stonehenge, reducing the need for human effort, warrants particular scepticism. This idea, echoed in fringe theories for Stonehenge's bluestones (smaller Welsh stones), lacks empirical support and contradicts established geology. During the Last Glacial Maximum (LGM, ~27–19 ka ago), the British-Irish Ice Sheet (BIIS) covered Scotland, Ireland, most of Wales, and northern England, but stopped well north of Wiltshire's Marlborough Downs and Salisbury Plain. Southern England was periglacial, cold tundra with permafrost, but ice-free, as glaciers flowed from highlands without extending south. No glacial erratics (transported boulders) of any kind, let alone sarsens, have been found on Salisbury Plain.

Recent studies (2024–2025) further debunk glacial theories for Stonehenge stones. A July 2025 analysis of the "Newall boulder" (a bluestone fragment) found "no evidence to support an interpretation that it is a glacial erratic. Nash's dismissal, that glacial ideas have "no basis in fact”, is thus justified; invoking them risks pseudoscience, as sarsens form from local Palaeogene sands, not distant bedrock.

• Unresolved Issues: Methodological debates persist, but glacial claims are a red herring. Future work might use advanced zircon dating or quarry surveys to confirm West Woods.
• Implications for Stonehenge: Human transport from West Woods implies Neolithic ingenuity. Dismissing glaciation strengthens this narrative, avoiding unproven shortcuts.

In summary, the debate refines provenancing without resolution yet, but glacial transport is soundly refuted.

References: 

Ciborowski, T. J. R., D. J. Nash, T. Darvill, et al. 2024. “Local and Exotic Sources of Sarsen Debitage at Stonehenge Revealed by Geochemical Provenancing.” Journal of Archaeological Science: Reports 53: 104406. https://doi.org/10.1016/j.jasrep.2024.104406.

Hancock, R. G. V., M. P. Gorton, W. C. Mahaney, S. Aufreiter, and K. Michelaki. 2024. “Stonehenge Revisited: A Geochemical Approach to Interpreting the Geographical Source of Sarcen Stone #58.” Archaeometry 67, no. 1: 1–19. https://doi.org/10.1111/arcm.12999.

Hancock, R. G. V., M. P. Gorton, W. C. Mahaney, S. Aufreiter, and K. Michelaki. 2025. “ On Sourcing Stonehenge Sarsen Stone #58: A Response to Nash and Ciborowski's Comments.” Archaeometry 1–3. https://doi.org/10.1111/arcm.70028.

Harding, P. et al. (2024) ‘Earliest Movement of Sarsen Into the Stonehenge Landscape: New Insights from Geochemical and Visibility Analysis of the Cuckoo Stone and Tor Stone’, Proceedings of the Prehistoric Society, 90, pp. 229–251. doi:10.1017/ppr.2024.13.

John, B. S., & Jackson, L. Jr. (2009). Stonehenge's Mysterious Stones. Earth, 54(1), 36–42 https://www.researchgate.net/publication/270162075_Stonehenge's_mysterious_stones

Nash, D. J., and T. J. R. Ciborowski. 2025. “Comment on: Stonehenge Revisited: A Geochemical Approach to Interpreting the Geographical Source of Sarsen Stone #58.” Archaeometry 1–14. https://onlinelibrary.wiley.com/doi/10.1111/arcm.13105.

Nash, D. J., T. J. R. Ciborowski, J. S. Ullyott, et al. 2020. “Origins of the Sarsen Megaliths at Stonehenge.” Science Advances 6, no. 31: 1–8. https://doi.org/10.1126/sciadv.abc0133.

Correcting the Record - A rebel without a cause.

Dear old Dr John rants: "Twitter (now X) which I can't get at since Mr Musk has decided that I am not a bona fide follower or disciple. Something about the new paper "refuting any glacial transport"..........."

What a rebel, sticking it to the man, standing up against Musk. We are all with you bro on the picket line.

Except he hasn't been banned - https://x.com/Bluestone4 - The account exists and appears active, with no visible indication of a ban or suspension—no "Account suspended" message or blank profile. I expect he has just forgotten his password. 

The Newall Boulder Excavation Report

With the publication of the definitive report on what is known as the "Newall Boulder" - Bevins et al (2025) - and the subsequent publicity as the Glacial Transport theory is given its coup de grâce, I thought it worthwhile revisiting an earlier post of mine from 2022. https://www.sarsen.org/2022/06/an-erratic-source.html

This identified the excavation report, and what appears to be a photo of it in situ. 

In Hawley's 6th Report Jan 1926 Vol V1 No.1 The Antiquaries Journal which is of his 1924 excavations he describes finding a foreign stone and also a photo of the excavation.

I think the stone pictured in the middle of the very left hand side of the excavations around stone 8, judging by the scale, is about the right depth and size to be the foreign stone he mentions. This provides the original context for the stone.  (Click to embiggen)

Kellaway's description seems to match it very well:

Reference: Bevins, R.E. et al (2025) (The enigmatic ‘Newall boulder’ excavated at Stonehenge in 1924: new data and correcting the record
(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)
Journal of Archaeological Science: Reports, Volume 66, 2025, 105303, ISSN 2352-409X,
https://doi.org/10.1016/j.jasrep.2025.105303.
(https://www.sciencedirect.com/science/article/pii/S2352409X25003360)

Revealing Lichen Covered Rock Carvings At Stonehenge

Another paper on the fascinating and innovative discovery methods of identifying rock art at Stonehenge that is hidden under the lichen has been released;

Gavin Leong , Matthew Brolly , David J. Nash , Novel lichen simulation and laser scan modelling to reveal lichen-covered carvings at Stonehenge, Results in Engineering (2025), doi: https://doi.org/10.1016/j.rineng.2025.106377 

This follows the pre-print released earlier this year:

Leong, Gavin and Brolly, Matthew and Anderson-Whymark, Hugo and Nash, David and Bedford, Jon, Novel Approaches for Enhanced Visualisation and Recognition of Rock Carvings at Stonehenge. Available at SSRN: https://ssrn.com/abstract=5126093 or http://dx.doi.org/10.2139/ssrn.5126093

and Gavin Leong's thesis:

Leong, G. (2024) Revealing lichen-covered rock art at Stonehenge: where terahertz imaging and photogrammetry meet machine learning, lichen simulation, and image analysis algorithms. PhD thesis, University of Brighton. Available at: https://research.brighton.ac.uk/files/49055416/PhD_Thesis_Gavin_Leong.pdf

Gavin Leong's PhD thesis, titled "Revealing Lichen-Covered Rock Art at Stonehenge: Where Terahertz Imaging and Photogrammetry Meet Machine Learning, Lichen Simulation, and Image Enhancement" and submitted in May 2024, serves as the foundational bedrock for the subsequent research outputs, including the February 2025 preprint on enhanced visualisation and recognition of exposed rock carvings and the July 2025 journal pre-proof on lichen simulation for detecting obscured carvings, both of which he led as the primary author. Drawing from extensive fieldwork at Stonehenge and innovative interdisciplinary approaches, Leong's thesis meticulously developed key methodologies such as the difference of Gaussians (DoG) and pseudo-depth mapping (PDM) techniques for visualising faint carvings on non-lichenised surfaces, achieving the discovery of new axe-head motifs on Stone 53, while pioneering the application of MeshNet—a 3D shape classification neural network—for semi-automated carving recognition with 90.7% accuracy on photogrammetry-derived meshes; these elements directly underpin the visualisation-focused preprint, providing the baseline tools and empirical discoveries that were refined and cited therein. Furthermore, the thesis introduced the groundbreaking Ramalina siliquosa diffusion-limited aggregation (RDLA) simulation, informed by laser-scanned lichen thickness data from Stone 30, to digitally replicate lichen occlusion on carving meshes, enabling denoising strategies that reduced visual noise by 70.7% and facilitating MeshNet retraining for 73.3% accuracy on simulated lichen-covered surfaces—innovations that form the core of the later journal article, extending the thesis's non-invasive ethos to address the 23% lichen-covered areas at Stonehenge without physical removal. Leong's comprehensive exploration of terahertz time-domain spectroscopy (THz-TDS) in laboratory and fieldwork settings, including partial least squares regression for substrate recovery beneath lichen layers up to 35 mm thick and at water contents below 18%, not only validated subsurface imaging as a complementary tool but also highlighted ethical conservation challenges, laying the groundwork for broader applications in global rock art sites and related fields like forest canopy modelling. Through rigorous experimentation, detailed appendices on code implementations, and a synthesis of machine learning with heritage science, Leong's doctoral work not only anticipated the challenges of lichen obscuration but also provided the theoretical, methodological, and empirical foundations that enabled the two papers to advance the field, deserving full credit for his pioneering contributions that bridge archaeology, remote sensing, and computational simulation in a manner that promises lasting impact on cultural heritage preservation.

The February 2025 preprint, titled "Novel approaches for enhanced visualisation and recognition of rock carvings at Stonehenge," introduced innovative visualisation techniques such as difference of Gaussians (DoG) and pseudo-depth mapping (PDM) to enhance the detection of faded carvings on exposed surfaces, leading to the discovery of four new carvings, ten potential carving areas, and nine alternative interpretations on Stone 53, while also demonstrating the efficacy of the MeshNet neural network for semi-automated carving recognition with 90.7% accuracy on non-lichen-covered meshes derived from photogrammetric data; it further suggested future extensions to lichen-obscured regions.

The later paper from July 2025, titled "Novel lichen simulation and laser scan modelling to reveal lichen-covered carvings at Stonehenge," explicitly builds upon the foundational preprint from February 2025 by addressing a key limitation identified in the earlier work—namely, the inability to analyse approximately 23% of Stonehenge's stone surfaces due to coverage by the fruticose lichen Ramalina siliquosa, which potentially obscures additional Early Bronze Age axe-head and dagger carvings. In contrast, the later paper extends this by developing a novel species-specific lichen simulation called Ramalina siliquosa diffusion-limited aggregation (RDLA), which modifies base diffusion-limited aggregation (DLA) with cone-based attachment (CBA) modes, logistic functions for branching behaviour, and efficiency improvements informed by new laser scan data from Stone 30 to capture real-world lichen thickness distributions (up to 37.5 mm, far exceeding typical carving depths of less than 1 mm). This simulation is applied to the photogrammetry-derived carving meshes from the earlier study (referred to as seed meshes), creating a database of digitally lichen-covered surfaces; subsequent denoising techniques, including cloth simulation sheathing and distance mapping, reduce lichen-induced visual noise by 70.7% as quantified by probability of superiority metrics, enabling clearer visualisation of underlying carvings via depth maps without physical lichen removal. A standout new result is the retraining and testing of MeshNet on these simulated lichen-obscured meshes, achieving 73.3% accuracy in distinguishing carvings from non-carvings (with high recall at 86.0% but lower precision at 68.5%), demonstrating that laser scanning combined with denoising and MeshNet remains viable for non-invasive detection even under shrubby lichen cover, albeit with reduced performance compared to the 90.7% baseline on clean data from the preprint. Additionally, the paper provides empirical data on lichen thicknesses from multiple species at Stonehenge, highlighting R. siliquosa's unique obscuring potential, and discusses broader applications, such as adapting RDLA for other fruticose lichens, subsurface imaging alternatives like XRF or terahertz, and extensions to global rock art sites or even unrelated fields like forest canopy modelling and virtual environment ageing effects, thereby advancing ethical conservation practices and opening avenues for further discoveries at Stonehenge and beyond.

Correcting the Record on the Ice Rafted Erratics of the Bristol Channel.

Ice Rafting Reconsidered — The Case for Floating Boulders in the Bristol Channel

In a recent blog post, Brian John reiterates his long-held skepticism toward the idea that the giant boulders scattered along the southern coastlines of the Bristol Channel were transported by floating ice. He argues that such a mechanism is “implausible” given glacial sea-level depression, and suggests that invoking isostatic rebound as a counterpoint is "special pleading."

However, three new peer-reviewed studies published in 2024 present compelling evidence that fundamentally contradicts this view and establish a well-supported case for ice-rafted boulder emplacement during the Middle to Late Pleistocene.

🧊 Gibson & Gibbard (2024): Stratigraphic Evidence for Ice-Rafted Boulders

This comprehensive review of Wolstonian Stage glaciation shows that large erratic boulders, including far-travelled lithologies from Scotland and northern England, are found resting on wave-cut rock platforms around the Bristol Channel and south coast. Crucially, these boulders are:

• Stratigraphically overlain by raised Ipswichian beach deposits, dated to 130–90 ka, showing they pre-date the last interglacial highstand.
• Interpreted as being ice-rafted, not dropped by grounded glacier ice — based on their scattered, isolated distribution and lack of associated till.

This directly challenges the notion that ice rafting is geologically implausible at these elevations.

🌊 Scourse (2024): Glacio-Isostatic Adjustment Enabled High Sea Levels

In a recent review of British–Irish Ice Sheet (BIIS) dynamics from MIS 5d to 2, Scourse provides strong evidence for:

• High relative sea levels during MIS 4 and MIS 3, caused by glacial isostatic loading as the BIIS expanded.
• Coincident ice margins calving into marine waters, which allowed icebergs and sea ice to transport and deposit debris onto present-day coastal sites.

This directly refutes Brian John’s claim that isostatic rebound cannot explain the present elevations of erratics — and shows that conditions were suitable for ice rafting in the Bristol Channel.

🪨 Bennett et al. (2024): New Mapping of Devon and Cornwall Boulders

Using LIDAR and field survey, Bennett and colleagues have documented discrete concentrations of far-travelled giant erratics along the coasts of south Devon and Cornwall. Their findings show:

• These boulders sit in intertidal and raised marine settings, not within glacial tills.
• Their distribution and lithologies are consistent with ice-rafting melt-out — not glacial pushing or dumping.

This further weakens the grounded glacier-only hypothesis and supports episodic marine deposition.

🧠 Common Sense Revisited

Brian John invokes the boulder-strewn Baltic coastlines as an example of wave-modified glacial sediments rather than ice-rafted material. But this comparison overlooks key differences:

• The Baltic has no tides and experienced greater isostatic uplift than southern Britain.
• Its glacial history and hydrodynamics differ greatly from the open Atlantic-fed Bristol Channel.

Context matters. The conditions in SW Britain during MIS 6 to 3 allowed for calving margins and floating ice — and the evidence now supports this interpretation.

✅ Conclusion: Floating Ice Delivered Boulders to the Bristol Channel

The 2024 studies converge on a new, evidence-based understanding:

• The southern coasts of Britain experienced periods of high relative sea level and iceberg activity during the Late Middle and Early Late Pleistocene.
• This created conditions suitable for the deposition of ice-rafted erratics.
• The hypothesis is no longer speculative — it's now robustly grounded in stratigraphy, dating, and geomorphology.

It’s time to update the narrative. Rather than dismiss the ice-rafting model, the latest science shows that it played a real role in shaping these iconic coastal landscapes.

---

References:

• Gibson, S. M. & Gibbard, P. L. 2024 (October): Late Middle Pleistocene Wolstonian Stage (MIS 6) glaciation in lowland Britain and its North Sea regional equivalents – a review. Boreas, Vol. 53, pp. 543–561. https://doi.org/10.1111/bor.12674. ISSN 0300-9483
Scourse, J.D. (2024), The timing and magnitude of the British–Irish Ice Sheet between Marine Isotope Stages 5d and 2: implications for glacio-isostatic adjustment, high relative sea levels and ‘giant erratic’ emplacement. J. Quaternary Sci., 39: 505-514. https://doi.org/10.1002/jqs.3611
• Bennett, M. R. et al. (2024). Evidence for Middle Pleistocene ice-rafted debris in south-west England: A GIS and field-based reassessment. https://ussher.org.uk/wp-content/uploads/benettetal1584130v2.pdf.

Still no evidence for an ice flow over the Somerset levels.

Correcting the record with regards to an embarrassing flight of fancy that there is evidence in the latest research for a glacial ice flow towards Stonehenge. 

“The paper by Ely et al. (2024) provides no basis for asserting that ice flowed over the Somerset Levels, as this region is not mentioned in connection with any ice advance. The simulation extending furthest south into the Celtic Sea, covering parts of Cornwall and Devon, is explicitly noted as lacking empirical support (Page 23). "In the simulation which reaches the furthest south in the Celtic Sea, an ice extent for which there is currently no evidence occurs over south‐west England (Cornwall and Devon), with ice advanced over the present‐day coastline." The claim of ice flowing over the Somerset Levels would thus be an overreach beyond the paper’s findings. In the broader Celtic Sea and Irish Sea regions, ice flow is generally inferred to be southwards or south-westwards, particularly associated with the Irish Sea Ice Stream, with no evidence presented for a south-easterly flow in the Bristol Channel. Figure 21, which addresses ice extent and fast-flowing regions, does not depict specific flow directions in the Bristol Channel but highlights model-data mismatches in the Celtic Sea.”

Ely, J.C., Clark, C.D., Bradley, S.L., Gregoire, L., Gandy, N., Gasson, E., Veness, R.L.J. and Archer, R. (2024), Behavioural tendencies of the last British–Irish Ice Sheet revealed by data–model comparison. J. Quaternary Sci, 39: 839-871. https://doi.org/10.1002/jqs.3628

Figure 21. The location and persistence of fast flow. Fast flow was defined as regions of ice flowing above 100m a−1. Values reflect the number of NROY simulations (likelihood) that produce ice stream flow for over 100 years (persistence), once the differing durations of ice cover each NROY produces are accounted for. (a) Overall persistence of ice stream conditions map. (b) and (c) show the locations of trimlines (Clark et al., 2018) in relation to ice streams. Note how many are co‐located with regions of low ice stream persistence and likelihood. Overall, this map could be viewed as a proxy for glaciation‐scaled erosivity and compared with the distribution and type of landforms such as tors, roches moutonnées, U‐shaped valleys, bedforms, etc. Modern‐day coastline is shown for orientation. [Color figure can be viewed at wileyonlinelibrary.com]