No Exploits back-arc basin in the Iapetus suture zone of Ireland
Bibliographic record
Abstract
A controversial aspect of the closure history of the Iapetus Ocean concerns the existence of the Exploits basin in Ireland and Britain. The Exploits–Tetagouche back-arc basin of the Canadian Appalachians opened during the Middle Ordovician as the Popelogan–Victoria volcanic arc migrated northwards from the Ganderian margin. The Bellewstown Terrane, within the Iapetus suture zone of Ireland, lies between the Ganderian–Avalonian Leinster Terrane and the Laurentian Grangegeeth Terrane. An early Ordovician ‘Celtic’ shelly fauna is hosted in volcanogenic breccia that we demonstrate is stratigraphically overlain by shales with no volcanic horizons. The lower 24 m of shale are unfossiliferous, but shale above this stratigraphic level has yielded a new graptolite fauna consistent with the upper part of the artus Biozone (Darriwilian, c . 464 Ma). U–Pb zircon dating of the volcanic horizon yields an age of c . 474 Ma. The shale, therefore, appears to represent c . 10 myr of deposition and a significant gap in volcanism. This, together with a Sandbian Anglo-Welsh fauna, suggests that the Bellewstown Terrane remained in a peri-Gondwanan position throughout the Ordovician. Hence, Exploits back-arc basin opening and Ganderian arc migration did not occur in the Irish sector of Iapetus. Supplementary materials: The table of U–Pb zircon data, CL images of zircon grains, concordia plot of all U–Pb zircon analyses, and additional drawings and notes on the graptolite fauna are available at www.geolsoc.org.uk/SUP18858 .
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.002 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".