An important paper in the Stonehenge Bluestone Transport Debate:
Critical Analysis of Claims Regarding High-Level Glacial Erratics in the Bristol Channel and the Implication for the Glacial Transport Theory of Stonehenge Bluestones
April 2025
License: CC BY-SA 4.0
- For convenience I reproduce it here-
Abstract
This paper critically examines the claim that many glacial
erratics at altitudes exceeding 100 meters along the Bristol Channel coast
indicate significant glacial activity capable of transporting bluestone
boulders to Salisbury Plain, supporting a glacial transport theory for
Stonehenge’s bluestones. The analysis evaluates erratics cited in the primary
source, An Igneous Erratic at Limeslade, Gower & the Glaciation of the
Bristol Channel (Quaternary Newsletter, 2024), its referenced studies, and
additional geological reports. The investigation reveals that no robustly
documented high-level erratics (>100 m) are substantiated, undermining the
proposed glacial transport model. A discrepancy between the abstract posted on
ResearchGate and the published paper highlights unsupported claims regarding
the prevalence of high-level erratics.
Introduction
The hypothesis that glacial erratics along the Bristol
Channel, found at elevations above 100 meters, indicate a thick and dynamic
Irish Sea Ice Stream capable of reaching Salisbury Plain has been proposed to
explain the origin of Stonehenge’s bluestones [1]. Glacial erratics are
boulders transported and deposited by glaciers, distinct from local bedrock.
The Irish Sea Ice Stream refers to a major glacial flow during the Quaternary
period, proposed to have influenced the Bristol Channel region. This claim, articulated
in the abstract of An Igneous Erratic at Limeslade, Gower & the
Glaciation of the Bristol Channel [1], suggests that glacial ice
transported bluestones from diverse geological origins to the Stonehenge site.
This paper systematically reviews the evidence for high-level erratics cited in
the original claim, including a table of erratics and referenced studies, to
assess the validity of the glacial transport theory. It also evaluates the
geographical focus on the south and east coasts of the Bristol Channel,
critical for the proposed glacial pathway.
Figure 1: Map of the proposed Irish Sea Ice Stream pathway
towards Salisbury Plain, showing south and east coast erratic locations
Methodology
The analysis focuses on the primary source [1], its cited
references (e.g., Harmer, 1928 [Figure 4] [2]; Madgett and Ingliss, 1987 [3]),
and additional geological reports [5–12]. A related blog post [4] by the
primary source author, cited for its list of claimed erratic locations, was
cross-checked against peer-reviewed sources. Each erratic was assessed based on
documented altitude, geological composition, evidence of glacial transport, and
relevance to the proposed glacial pathway towards Salisbury Plain. Supporting
documents, such as geological reports [5–10], were cross-referenced to verify
claims. The Fremington Clay Pits erratics [11] and the Joint Nature
Conservation Committee (JNCC) report [12] provided regional context. The
discrepancy between the ResearchGate abstract and the published paper was
examined to highlight inconsistencies. A map (Figure 1) illustrating the
proposed Irish Sea Ice Stream pathway towards Salisbury Plain, highlighting key
erratic locations, was used to clarify the geographical focus.
Discrepancy in the Primary Source
A critical issue with the primary source [1] is the mismatch
between the abstract posted on ResearchGate and the content of the published
paper in Quaternary Newsletter (2024). The ResearchGate abstract claims,
“Many glacial erratics are found at altitudes exceeding 100 meters,” implying
widespread high-level glacial activity sufficient to support bluestone
transport to Salisbury Plain. However, the published paper provides no specific
examples of erratics above 100 meters, relying instead on vague references to
historical sources [2, 3]. This discrepancy suggests an overstatement of
evidence in the abstract, potentially affecting interpretations of the glacial
transport hypothesis.
Figure 2: Screenshot taken in December 2024 of ResearchGate
article abstract.
Figure 3: Extract from the published paper in *Quaternary
Newsletter* (2024).
Geographical Relevance of Erratics
The glacial transport theory for Stonehenge’s bluestones
relies on ice movement from the Irish Sea Ice Stream pressing inland across the
south and east coasts of the Bristol Channel towards Salisbury Plain, as
illustrated in Figure 1. This map shows the ice flow direction, highlighting
south and east coast locations like Baggy Point and Ilfracombe as critical to
the transport theory. While proponents may cite north coast erratics (e.g.,
Gower) as evidence of regional glaciation, their misalignment with the proposed
pathway to Salisbury Plain limits their relevance. Thus, the focus on south and
east coast erratics is critical for evaluating the theory.
Analysis of Cited Erratics
The following sections evaluate each cited erratic location
for altitude, geological context, and relevance to the glacial transport claim.
1. Lundy (138 m)
- Altitude:
138 m
- Citation:
[4]
- Evidence:
Rolfe et al. (2014) [5] indicate these are local rocks with minimal
transport distance and no glacial imprint. Carr (2019) [6] argues for a
residual boulder origin due to two-stage weathering.
- Relevance:
These erratics are not relevant to the high-level glacial claim due to
their non-glacial origin.
2. Shebbear (150 m)
- Altitude:
150 m
- Citation:
[4]
- Evidence:
The Shebbear erratic is a sarsen stone [7], a sedimentary rock not
typically transported by the Irish Sea Ice Stream.
- Relevance:
As a non-glacial erratic, this site is irrelevant to the claim.
3. Westonzoyland (10 m)
- Altitude:
10 m
- Citation:
[4]
- Evidence:
At 10 meters, within tidal range, this erratic does not qualify as
high-level.
- Relevance:
Irrelevant due to low altitude.
4. Baggy Point (45 m, 60 m, 80 m)
- Altitude:
45, 60, and 80 m
- Citation:
[4, 8]
- Evidence:
The highest, the Ramson Cliff erratic, was originally a standing stone in
a pasture field, later moved by a farmer [9, 10]. Its angular, rough
surface distinguishes it from foreshore erratics, and its movement raises
questions about its glacial origin. Other Baggy Point erratics are small
and lack reliable glacial context.
- Relevance:
Below 100 meters and with potential anthropogenic influence, these
erratics are insignificant for the high-level claim.
5. Ilfracombe-Berrynarbour (150–175 m)
- Altitude:
150–175 m
- Citation:
[4, 13]
- Evidence:
The JNCC report P.202 [13] mentions “erratic material” at 150–175 m but
provides no descriptions of specific boulders, their composition, or
primary data, rendering the claim uncorroborated by geological evidence.
- Relevance:
The vague and uncorroborated evidence weakens its support for the
high-level claim.
6. Kenn (7 m)
- Altitude:
7 m
- Citation:
[4, 14]
- Evidence:
At 7 meters, this erratic is not high-level. Contextual analysis [15]
confirms its irrelevance.
- Relevance:
Irrelevant due to low altitude.
7. Court Hill (68 m)
- Altitude:
68 m
- Citation:
[4, 16]
- Evidence:
Lacks documented erratic boulders relevant to glacial transport.
- Relevance:
Irrelevant due to lack of evidence.
8. Nightingale Valley / Portishead Down (85 m)
- Altitude:
85 m
- Citation:
[4, 17]
- Evidence:
No recorded erratic boulders.
- Relevance:
Irrelevant due to lack of evidence.
9. Fremington Clay Pits (20–30 m)
- Altitude:
20–30 m
- Citation:
[11]
- Evidence:
Erratics are embedded in clay below ground level, disqualifying them as
high-level.
- Relevance:
Irrelevant due to low altitude.
Discussion
The claim that many glacial erratics exceed 100 meters in
altitude [1] is unsupported by evidence. No robust evidence supports high-level
erratics. This undermines the hypothesis that the Irish Sea Ice Stream was
thick and dynamic enough to reach Salisbury Plain. Only Ilfracombe-Berrynarbour
suggests elevations above 100 meters, but the evidence is vague and
uncorroborated [13]. Other sites either fall below 100 meters, lack glacial
context, or are not erratics (e.g., Shebbear sarsen). The Baggy Point erratics,
while notable, are below 100 meters and include a potentially anthropogenic
standing stone.
The bluestones’ diverse origins, spanning over 30 geological
sources, suggest multiple quarries, which is inconsistent with a single glacial
pathway capable of transporting such varied material to Salisbury Plain.
Reviewed historical references, including Harmer’s 1928 erratic map [Figure 4] [2]
and Madgett and Ingliss (1987) [3], do not document specific high-level
erratics above 100 meters. The JNCC report [12] finds no evidence for extensive
high-level glacial deposits, stating that glacial limits are poorly constrained
in the Bristol Channel.
Figure 4: Extract from Harmer’s 1928 map of erratics.
The geographical focus on south and east coast erratics
limits the relevance of north coast erratics. The glacial transport theory
persists due to historical arguments and the appeal of natural explanations,
but the lack of high-level erratic evidence shifts focus to human transport.
Human transport is supported by archaeological evidence of quarrying at sites
like Preseli Hills and the feasibility of moving bluestones via sledges or
water routes, as demonstrated in experimental archaeology.
Conclusion
The claim that high-level glacial erratics (>100 m) along
the Bristol Channel support a glacial transport model for Stonehenge’s
bluestones is not substantiated. The cited sources and erratic locations fail
to provide reliable evidence of erratics above 100 meters, and many are
irrelevant due to non-glacial origins, low altitudes, or geographical
misalignment with the proposed glacial pathway. The lack of evidence for
high-level erratics challenges the glacial transport theory, supporting further
investigation into human transport mechanisms
Figures
- Figure
1: Map of the proposed Irish Sea Ice Stream pathway towards Salisbury
Plain, showing south and east coast erratic locations (e.g., Baggy Point,
Ilfracombe) and high ground.
- Figure
2: Screenshot taken in December 2024 of ResearchGate article abstract.
- Figure
3: Extract from the published paper in Quaternary Newsletter
(2024).
- Figure
4: Extract from Harmer’s 1928 map of erratics.
References
1. John, B. (2024). An Igneous Erratic at Limeslade, Gower
and the Glaciation of the Bristol Channel. *Quaternary Newsletter*. Available: https://www.researchgate.net/publication/381775577.
2. Harmer, F. W. (1928). England and Wales: Distribution of
Glacial Erratics and Drift. Available: https://www.antiquemapsandprints.com.
3. Madgett, P. A., & Ingliss, J. D. (1987). A
Reappraisal of the Glacial Deposits in North Devon. *Transactions of the
Devonshire Association*, 119, 1–20. Available: https://devonassoc.org.uk/wp-content/uploads/2018/11/A-Reappraisal-MadgettTDA-1987.pdf.
4. John, B. (2024). The Myth of Shoreline Erratics.
Available: https://brianmountainman.blogspot.com/2024/09/the-myth-of-shoreline-erratics.html.
5. Rolfe, C. J., et al. (2014). Lundy Island Geological
Report. *Lundy Field Society Journal*. Available: https://eprints.soton.ac.uk/380559/1/LFS_Journal_2014-Rolfe_et_al.pdf.
6. Carr, S. J. (2019). Landscape Evolution and Glacial
Geomorphology. *Cumbria Research Repository*. Available: https://insight.cumbria.ac.uk/id/eprint/4557/1/Carr_LandscapeEvolution.pdf.
7. Daw, T. (2025). The Shebbear Erratic Sarsen. *Sarsen
Substack*. Available: https://sarsen.substack.com/p/theshebbear-erratic-sarsenhtml.
8. Green, C. P. (1992). The Geomorphology of Baggy Point,
North Devon. *Geological Survey Report
9. Ordnance Survey Explorer (1:25,000): No. 139 Bideford,
Ilfracombe and Barnstaple.
10. John, B. (2015) The
Erratics at Baggy Point, Croyde and Saunton (1) Available: https://brian-mountainman.blogspot.com/2015/01/the-erratics-at-baggy-point-croyde-and.html
11. Arber, M.A. (1964) ‘Erratic Boulders within the
Fremington Clay of North Devon’, Geological Magazine, 101(3), pp.
282–283. doi:10.1017/S0016756800049517.
12. Campbell, S., Scourse, J.D., Hunt, C.O., Keen, D.H.
& Stephens, N. 1998. Quaternary of South-West England. Geological
Conservation Review Series No. 14, JNCC, Peterborough, ISBN 0 412 78930 2. Available: https://hub.jncc.gov.uk/assets/965f9190-c00b-4a6b-aa9f-8e3855492404
13. Campbell, S., Scourse, J.D., Hunt, C.O., Keen, D.H.
& Stephens, N. 1998. Quaternary of South-West England. Geological
Conservation Review Series No. 14, JNCC, Peterborough, ISBN 0 412 78930 2 Available: https://data.jncc.gov.uk/data/965f9190-c00b-4a6b-aa9f-8e3855492404/gcr-v14-quaternary-of-south-west-england-c7.pdf
14. Campbell, S., Scourse, J.D., Hunt, C.O., Keen, D.H.
& Stephens, N. 1998. Quaternary of South-West England. Geological
Conservation Review Series No. 14, JNCC, Peterborough, ISBN 0 412 78930 2.
Available: https://geoguide.scottishgeologytrust.org/p/gcr/gcr14/gcr14_kennchurch.pdf
15. Scourse, J.D. Proceedings of the British Academy, 92,
271—314 Transport of the Stonehenge Bluestones: Testing the Glacial Hypothesis Available: https://www.thebritishacademy.ac.uk/documents/3923/92p271.pdf
16. Campbell, S., Scourse, J.D., Hunt, C.O., Keen, D.H.
& Stephens, N. 1998. Quaternary of South-West England. Geological
Conservation Review Series No. 14, JNCC, Peterborough, ISBN 0 412 78930 2.
Available: https://geoguide.scottishgeologytrust.org/p/gcr/gcr14/gcr14_courthill
17. Campbell, S., Scourse, J.D., Hunt, C.O., Keen, D.H.
& Stephens, N. 1998. Quaternary of South-West England. Geological
Conservation Review Series No. 14, JNCC, Peterborough, ISBN 0 412 78930 2.
Available: https://geoguide.scottishgeologytrust.org/p/gcr/gcr14/gcr14_nightingalevalley
