the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Aug 2025
Geological investigations of the Lizard District, Cornwall, England: 1818–1883
Abstract. A suite of lower Paleozoic slab of oceanic lithosphere was obducted onto the southern margin of Avalonia during the Variscan orogeny is now exposed throughout the Lizard District of Cornwall, England. This complexly faulted and metamorphosed region of mafic and ultramafic rocks has been the subject of geological investigation for over two hundred years. Herein the most significant scientific contributions made over a sixty-five-year interval from 1818 to 1883 are reviewed. Early workers, including Ashurst Majendie, Adam Sedgwick, John Rodgers, and Henry De la Beche, conducted field-based studies of the region, making lithologic observations and mapping contacts between the major rock units. Subsequently, an intense phase of investigation into the processes and products of contact and regional metamorphism among primarily British geologists informed and inspired the field and microscopical studies of Thomas G. Bonney. Detailed consideration of the pioneering work of these 19th century geologists provides insights into their methodologies as well as their evolving understanding of the complex and enigmatic rocks of the Lizard.
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AC1: 'Comment on hgss-2025-5', Carl Drummond, 13 Aug 2025
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RC1: 'Reply on AC1', William Brice, 05 Sep 2025
REVIEWER COMMENTS Reviewed by: William R. Brice (wbrice@pitt.edu). 27 August 2025
Article Reviewed: Geological investigations of the Lizard District, Cornwall, England: 1818-1883 by Carl N Drummond https://doi.org/10.5194/hgss-2025-5.
GENERAL: Very nice analysis and well organized.
SUGGESTIONS AND COMMENTS:
- When quoting from another publication it is my understanding (based on the Chicago Manual of Style, 13th edition, sections 10.36 to 10.49) ellipses are used to indicate omitted material. I think it would make the quotes in the text clearer if ellipses were used, e.g. pages 3 and 4 with the quote from Majendie – ellipses added in red:
In 1818 Ashurst Majendie, a founding member of the Geological Society of London, conducted a study in which he hoped “…to offer to the Society an account of the boundaries and position of the serpentine formation, occurring in the vicinity of the Lizard Promontory…” (Majendie, 1818, p. 32).
Also, shouldn’t the et al. when used in a citation be in italics? Same for e.g.? That is not the case in the paper.
SPECIFIC QUESTIONS/SUGGESTIONS:
- Page 9, line 262 – mention of the work of T. Sterry Hunt (the first of several), but no reference is given. It would be nice for the readers to have a reference or two to Dr. Hunt’s work related to the subject under discussion.
- Page 9, line 279 – reference to a figure in the work of King and Rowney 1876 – would it be possible to add that figure to this article so the readers can see the “..surrealistic qualities.”?
- Page 11, line 328 – part of a quotation with ( ) in it. I assume the ( ) is in the original, but it would be clearer to the reader if it was stated in the reference that the ( ) is in the original, and not added by the author of the article. Just keeps things clearer.
- Page 12, caption for Figure 3 – is the citation 1877a or 1877b? There are two Bonney 1877 references from which to choose.
- Page 13 – caption for Figure 4 – same as number 4 above; is the citation for 1877a or 1877b?
- Page 15 – caption for Figure 5 – same as numbers 4 and 5 above; is the citation for 1877a or 1877b?
- Page 16, lines 466 and 474 – citations for “Bonney 1887.” There is no “Bonney 1887” listed in the references. If this is not a typo and should be Bonney 1883, then the reference for Bonney 1887 should be added to the reference list.
- Page 17, line 491 – citation for “Bonney 1833.” There is no Bonney 1833 listed in the reference list. If this is not a typo and should be Bonney 1883, then the reference for Bonney 1833 should be listed in the reference list.
- Page 18, line 545 – possible typo; “…abundant enstatie and augite.” Should that mineral be enstatite?
10. Page 19, lines 555 and 556 – “…undertaken in the early 19th 555 century. During the from 1818 to 1883 the methods and sophistication…” Seems like a word is missing from the sentence beginning with “During.” Perhaps it would read more smoothly like this: “During the time from 1818 to 1883…” or “During the period from 1818 to 1883…”
- Page 20, line 599 – where is the Walter E. Helmke Library located? Is it at Purdue or in England?
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AC2: 'Reply on RC1', Carl Drummond, 08 Sep 2025
Professor Brice
Thank you so much for such a kind and complete review. I will address all the questions and suggestions you have provided.
All the best!
Carl
Citation: https://doi.org/10.5194/hgss-2025-5-AC2
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RC1: 'Reply on AC1', William Brice, 05 Sep 2025
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AC3: 'Request for formal review', Carl Drummond, 09 Oct 2025
Hi everyone, I have noticed there have been around 30 downloads of my draft manuscript on the Lizard. I would love to have some more formal reviews done so the editors can move forward with the review process.
Thanks so much!
Carl
Citation: https://doi.org/10.5194/hgss-2025-5-AC3 -
RC2: 'Comment on hgss-2025-5', Anonymous Referee #2, 20 Oct 2025
First, I want to sincerely apologize for the unacceptably long delay in completing this review. I fully understand how frustrating this must have been. Although changes in my personal circumstances contributed to the delay, I take full responsibility and apologize for the inconvenience caused.
I have thoroughly read this study and greatly enjoyed it. The writing is good, and the arguments are easy to follow. I think the writer has used jargon sparingly, such that the paper should be relatively easy to follow regardless of background. Please find below some minor comments to improve the manuscript.
I have two comments that I would like to see addressed before publication:
- The manuscript places significant emphasis on Thomas Bonney. It should be made clearer what insights or broader understanding this focus provides.
- I would like to see the observations and interpretations of the early workers placed more fully in the context of their contemporaries. For example, what did others make of ophiolites and metamorphic rocks at this time? How did people interpret thrust tectonics more broadly? This is done effectively in the section discussing serpentinization, but similar contextualization should be incorporated more thoroughly throughout the paper.
Abstract:
Lines 1-2: grammatical issue. “and is”
Give a little context to Thomas Bonney. Did he work on the Lizard?
Introduction
Clear and useful overview.
Fig 1: Please add a larger map and co-ordinates so people can locate the study area. Misspelling of Traboe Cumulate Complex. I would make thrust arrows on moho much smaller, as these aren’t large scale thrusts but rather indicate a locally variable shear zone.
Lizard district is sometimes capitalized and sometimes not.
2.1 Majendie
Can you please give references for Loe Pool and Helford (e.g., 10 km west of XX). They are not marked on the map, so I cannot judge the extent of the traverse. Perhaps mark Helford estuary on the map, as it is referred to multiple times.
Please give an example of some of his observations which are “congruent with modern surveys”.
2.3. Rogers 1822
It seems Rogers was the first to draw clear distinctions between these four groups? If so, that is worth acknowledging. If not, perhaps the first person to do this could be named.
2.4 De la Breche, 1839
It seems he was the first to note the structural relationship between the serpentine and the amphibolites (i.e., serpentine atop amphibolites). Although he did not invoke thrust tectonics, it is a correct observation. Perhaps worth highlighting more clearly.
2.5 King & Rowney, 1876
Line 275: misspelling of Kynance Cove
Would it be possible to reproduce this composite image (Line 278), given its historical significance?
3.1 Survey of the west and east coasts
Line 323: Misspelling of Pentreath.
For this section, it would be helpful to give a brief overview of the modern interpretation so we can compare it with the views of Bonney. E.g., please outline what modern interpretations include at Pentreath.
Fig. 3: Misspelling of Landewednack.
Table 4: How does the black trap dyke relate to the lithologies outlined in Fig. 3?
3.3. Temporal relationships
Lines 395-397: This petrographic analysis appears to be considerably more advanced than those that preceded it, which is worth emphasizing. It would also be valuable to understand how it compared with other studies of the period—was Bonney ahead of his contemporaries in terms of petrographic technique and interpretation?
What is a “trap dyke”?
3.4. Microscopic examinations
Line 419: “wa” to “was”.
Line 420: “such an interpretation is not at all aligned”
Fig. 5: “light regions”?
4.1. Field and microscopic survey of the schists
It is interesting that Bonney repeatedly interpreted the Landewednack amphibolites as metasedimentary. How did geologists at the time distinguish between metasediments and metaigneous rocks? How does that relate to the invention of geochemical analysis?
Citation: https://doi.org/10.5194/hgss-2025-5-RC2 -
AC4: 'Reply on RC2', Carl Drummond, 20 Oct 2025
Thank you so much for this comprehensive review. I greatly appreciate the suggestions and actionable steps for enhancement.
Carl
Citation: https://doi.org/10.5194/hgss-2025-5-AC4
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I realized the final edit failed to remove two spurious words from the first sentence of the abstract. I apologize. The sentence should read:
A lower Paleozoic slab of oceanic lithosphere was obducted onto the southern margin of Avalonia during the Variscan orogeny is now exposed throughout the Lizard District of Cornwall, England.
Thank you.
Carl