Peer reviewing John 2025

(I am happy to share without comment an independent peer review of John 2025 - it is not by me or anyone involved in the debate.)

An expanded review of "Response: The Provenance of the Limeslade Igneous Erratic: A Matter of No Importance?" by Brian John, (Quaternary Newsletter Vol. 164, February 2025), and the previous "interim report" John, B.S. (2024). An Igneous Erratic at Limeslade, Gower & the Glaciation of the Bristol Channel. Quaternary Newsletter 162, 4 - 14

### Overview 

1. **Interim Report**:

   - Describes a large dolerite erratic at Limeslade Bay, Gower Peninsula, suggesting transport by the Irish Sea glacier. It posits implications for Stonehenge bluestone transport, favoring glacial over human mechanisms.

   - Key points include the erratic’s size (over 2m, ~5 tons), its non-local dolerite composition, and its position in the intertidal zone, with ongoing provenancing work noted.

2. **Response Article (Quaternary Newsletter Vol. 164)**:

   - A rebuttal to Pearce et al.’s (2024) critique in QN 163 of John’s earlier note (QN 162). It defends the interim findings, addresses criticisms of methodology and interpretation, and expands on the erratic’s significance for Bristol Channel glaciation and Stonehenge debates.

   - Emphasizes the erratic’s size and context (e.g., associated smaller erratics), refuting claims of its insignificance and challenging ice-rafting hypotheses.

Both of John's documents argue for glacial transport, but the response escalates the debate, engaging directly with critics and reinforcing the erratic’s relevance.

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### Failures of Logic

#### 1. Interim Report

- **Assumption of Irish Sea Glacier Transport**:

  - Logic: The report assumes the erratic was transported by the Irish Sea glacier without fully exploring alternatives (e.g., Welsh ice or fluvial processes). This is a potential oversight, as the Gower Peninsula’s proximity to Welsh ice sources isn’t adequately discounted.

  - Issue: While supported by the erratic’s non-local dolerite nature, the lack of discussion on competing ice flows weakens the argument.

- **Stonehenge Bluestone Link**:

  - Logic: The connection to Stonehenge bluestones relies on the erratic’s glacial transport as a parallel, but the distances (50-60 km vs. 150-200 km) and timing (Anglian glaciation vs. Neolithic construction) aren’t reconciled.

  - Issue: This leap assumes bluestones were glacial deposits later moved by humans, but the report doesn’t clarify this intermediate step, risking overgeneralization.

- **Limited Data Acknowledgment**:

  - Logic: The report admits the pXRF data’s limitations (three readings) but proceeds to draw implications, potentially overstating preliminary findings.

  - Issue: This tension undermines confidence in conclusions without stronger caveats.

#### 2. Response Article (Quaternary Newsletter Vol. 164)

- **Terminology Debate (Irish Sea Glacier vs. Ice Stream)**:

  - Logic: John dismisses Pearce et al.’s critique of “Irish Sea Glacier” vs. “Irish Sea Ice Stream” as pedantic, citing interchangeable usage in literature (e.g., John, 1968a, 2018). However, he doesn’t justify why this distinction lacks substantive impact on his argument.

  - Issue: If ice stream dynamics (e.g., faster flow, specific paths) differ from a broader glacier, this could affect transport feasibility, and John’s casual dismissal avoids engaging with potential implications.

- **Rejection of Ice Rafting**:

  - Logic: John argues against Pearce et al.’s ice-rafting hypothesis (Scourse, 2024), asserting that coastal erratics result from in situ glacial deposits eroded by waves, not floating ice. He cites examples like Whitesands and Rödloga Storskär but generalizes without addressing site-specific evidence for Limeslade.

  - Issue: This risks a hasty generalization. Ice rafting could explain some erratics and dismissing it outright without Limeslade-specific counterevidence weakens the rebuttal.

- **Stonehenge Transport Polemic**:

  - Logic: John denies a polemic against human transport advocates (e.g., Parker Pearson et al., 2021), claiming a neutral review, yet his tone and selective focus on their “retreats” (e.g., Waun Mawn) suggest bias.

  - Issue: This contradiction undermines his claim of objectivity, as the response prioritizes refuting human transport over balanced discussion.

- **Extrapolation to Somerset**:

  - Logic: John posits an ice margin 50 km inland from Somerset based on erratics up to 80m asl and modeling (e.g., Boulton & Hagdom, 2006), challenging Pearce et al.’s reluctance to accept widespread glaciation. However, he doesn’t reconcile this with patchy till evidence or alternative explanations (e.g., periglacial processes).

  - Issue: Overreliance on modeling and selective high-altitude erratics risks overstating glacial extent without addressing gaps in field evidence.

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### Missing References

#### 1. Interim Report

- **Rock Provenancing**:

  - Missing: Detailed citations for dolerite identification beyond preliminary pXRF (Parry & Darvill). Geological surveys or petrological studies (e.g., akin to Bevins et al., 2014) are needed for North Pembrokeshire linkage.

  - Impact: Ongoing work is noted, but the lack of interim references limits credibility.

- **Glacial History**:

  - Missing: Citations for Irish Sea glacier extent and flow (e.g., Scourse et al., 2019, 2021, though later referenced in the response). Regional glacial studies are assumed but not specified.

  - Impact: This leaves the transport mechanism’s foundation vague.

- **Stonehenge Context**:

  - Missing: References to bluestone composition or glacial evidence near Stonehenge (e.g., Kellaway, 1971, though debated). Comparative erratic studies are absent.

  - Impact: The analogy to Stonehenge lacks grounding without these.

#### 2. Response Article

- **pXRF Critique Defense**:

  - Missing: Specific studies validating pXRF as a preliminary tool (e.g., Potts et al., 2006, is cited but not tied directly to methodology defense). John counters Pearce et al.’s hostility but lacks methodological benchmarks.

  - Impact: This weakens his rebuttal of their geochemical critique.

- **Carn Meini Variations**:

  - Missing: Additional references beyond Bevins et al. (2014) and Kokelaar et al. (1984) to support John’s claim of lateral variations in Preseli tors, contra Pearce et al.’s consistency argument.

  - Impact: The disagreement rests on interpretation without exhaustive citations, limiting persuasiveness.

- **Ice Rafting Counterevidence**:

  - Missing: Direct studies on Limeslade’s depositional context to refute Scourse (2024). General examples (e.g., St. Lawrence River, Guillaume, 2022) are cited, but site-specific data is absent.

  - Impact: The rejection of ice rafting lacks localized support, relying on broader analogies.

- **Somerset Glacial Extent**:

  - Missing: Field studies beyond Hunt (2006) and Kellaway (1971, 2002) to confirm inland ice margins. Modeling citations (e.g., Hubbard et al., 2009) are broad but not tied to specific Somerset evidence.

  - Impact: The extrapolation to Stonehenge’s vicinity needs more robust regional data.

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### Comparative Analysis and Broader Implications

- **Logical Consistency Across Documents**:

  - The interim report cautiously suggests glacial transport, while the response doubles down, aggressively defending against Pearce et al.’s critique. This shift from tentative to assertive may reflect reaction to criticism rather than new evidence, risking logical overreach (e.g., Somerset ice margin).

- **Reference Gaps**:

  - The interim report’s brevity excuses some omissions, but the response, despite a long reference list, selectively engages with critics’ work (e.g., citing Bevins et al., 2022, but not fully countering their data). This mirrors John’s accusation of Pearce et al. ignoring “inconvenient literature,” suggesting mutual gaps.

- **Debate Context**:

  - The documents fuel a polarized debate—glacial (John) vs. human transport (Pearce et al., Parker Pearson et al.). The Limeslade erratic’s size and location bolster John’s case, but logical leaps and missing field data hinder definitive resolution.

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### Conclusion

The interim report presents a plausible glacial transport hypothesis for the Limeslade erratic but falters in assuming a single mechanism and linking to Stonehenge without robust data. The response strengthens this stance but introduces new logical flaws (e.g., dismissing ice rafting broadly, overstating Somerset glaciation) and fails to fill reference gaps with site-specific evidence. Both documents reflect an ongoing, contentious scientific exchange, where logical rigor and comprehensive citation are sacrificed to interim constraints and rebuttal fervor. Future work, as John notes, requires detailed provenancing and field studies to resolve these issues.