I came across an intriguing claim about glacial erratics on the shores of the Bristol Channel that underpins a Stonehenge creation theory.
"Further, of the scores of known glacial erratics on the shores of the Bristol Channel, many are found at altitudes in excess of 100m, indicating that during at least one glacial episode the ice of the Irish Sea Ice Stream was thick enough and dynamic enough to press inland across the coasts of Devon and Cornwall. It is therefore probable that glacier ice also reached Salisbury Plain, and that the bluestone boulders and smaller fragments at Stonehenge — from more than 30 different sources — were glacially transported. "
The claim is that many glacial erratics are found at altitudes in excess of 100m, and that this fact would indicate all sorts of stuff. And that this is the "abstract" of a paper that has presumably had some sort of review.
So let's look at the paper: An Igneous Erratic at Limeslade, Gower & the Glaciation of the Bristol Channel linked from https://www.qra.org.uk/quaternary-newsletter/qn-162-archive/
What does it say?
Not what the author's abstract says.
The references are Harmer's Erratic Map of 1928: Here's the extract, click to embiggen.
Nope.
For the Ilfracombe-Berrynarbour reference see below.
Paul Berry - https://devongeography.wordpress.com/2021/10/27/coastal-walk-at-baggy-point-north-devon/ has some good photos of the Baggy Point erratics - 46, 60 and 80m in altitude. So they aren't part of the many at over 100m. More about them later.
The author of the claim has elsewhere provided a useful table of the erratics he knows of:
Here are some of the recorded altitudes of erratics on or near the coasts of Cornwall, Devon and Somerset:
Lundy 138m
Shebbear 150m
Westonzoyland 10m
Baggy Point 80m, 60m and 45m
Ilfracombe 150m - 175m
Kenn 7m
Court Hill 68m (ice surface was above 85m)
Nightingale Valley / Portishead Down 85m
Let's look at them in turn:
Lundy - the most comprehensive report is https://eprints.soton.ac.uk/380559/1/LFS_Journal_2014-Rolfe_et_al.pdf They are local rocks that have been pushed around on the island, not relevant.
"The lack of a glacial imprint on these boulders, minimal transport distance and lack of periglacial modification undermines the glacial transport model proposed by Rolfe et al. (2012); an origin as residual boulders derived from two-stage weathering is far more likely." https://insight.cumbria.ac.uk/id/eprint/4557/1/Carr_LandscapeEvolution.pdf
Shebbear - A sarsen stone not a glacial erratic https://sarsen.substack.com/p/the-shebbear-erratic-sarsenhtml
Westonzoyland - 10m - basically within tidal range.
Baggy Point 80m, 60m and 45m -
Yes - under 100m. But the author has repeatedly written about them:
https://brian-mountainman.blogspot.com/2023/10/pink-tuff-erratics-from-baggy-point.html
In 1969 this boulder was in the middle of a pasture field, right on the crest-line of Baggy Point above Ramson Cliff, though in a low-point of that crest-line. It was standing upright, part-buried in the thin soil.... in the early 1970s this same farmer decided to plough those fields, initially simply resulting in the boulder being dislodged and lying prone; then shortly afterwards he dragged it to the edge of the field, where it has been ever since, adjacent to the Coast Path,...Some have suggested that this erratic (in its 1969 context) represents a prehistoric Standing Stone - quite feasible, and there is another standing stone nearer to Putsborough, though that one is a local slabby sandstone. Because of the occurrence of erratic boulders on the southern shore of Baggy, at Saunton Down End, and under Saunton cliffs, it was then suggested that the boulder might have been dragged up from such a location. Against this is the shape of the boulder - which is rather angular and rough-surfaced - not at all like those on the foreshore,
What? It is a standing stone that the farmer has moved to the edge of his field. And the others are so small they wouldn't even fill a wheelbarrow, and seem to be moved about at will. The lack of reliable context makes them irrelevant.
Ilfracombe: again we can go back to the blogger behind the claim:
https://brian-mountainman.blogspot.com/2022/03/ilfracombe-erratic-spread.html
"there is some evidence provided by erratic material that ice extended to about 150-175 m OD on the western plateau behind Ilfracombe and Berrynarbour."
Pretty thin gruel to base a theory on as I can find no other supporting sources. Certainly there are no erratic boulders recorded.
Kenn - 7m - hardly high-level. The best reference is: https://geoguide.scottishgeologytrust.org/p/gcr/gcr14/gcr14_kennchurch.pdf and put in context in: https://www.thebritishacademy.ac.uk/documents/3923/92p271.pdf as is,
Court Hill 68m - https://geoguide.scottishgeologytrust.org/p/gcr/gcr14/gcr14_courthill No relevant erratic boulders
Nightingale Valley / Portishead Down 85m -https://geoguide.scottishgeologytrust.org/p/gcr/gcr14/gcr14_nightingalevalley No relevant erratic boulders.
So that list was a wash.
What about the erratics found in the Fremington Clay Pits near Barnstable?
Claypits Cover lies between 20 - 30 m - the erratics were found in the clay some metres below ground.
Oh dear, not a single reliable reference to a "high-level erratics", let alone many of them. The still magisterial JNCC report says it best: And is worth a read for details of the evidence across the region.
Dr John - Ice Age - Enjoy
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