Tectonic architecture of an arc-arc collision zone, Newfoundland Appalachians
Bibliographic record
Abstract
The Appalachian-Caledonian orogen records a complex history of the closure of the Cambrian-Ordovician Iapetus Ocean. The Dunnage Zone of Newfoundland preserves evidence of an Ordovician arc-arc collision between the Red Indian Lake Arc, which forms part of the peri-Laurentian Annieopsquotch accretionary tract (ca. 480–460 Ma), and the peri-Gondwanan Victoria Arc (ca. 473–453 Ma). Despite the similarity in age, the coeval arc systems can be differentiated on the basis of the contrasts that are apparent across the suture zone, the Red Indian Line. These contrasts include structural and tectonic history, stratigraphy, basement characteristics, radiogenic lead in mineral deposits, and fauna. The arc-arc collision is considered in terms of modern analogues (Molucca and Solomon Seas) in the southwest Pacific, and the timing is constrained by stratigraphic relations in the two arc systems. The Victoria Arc occupied a lower-plate setting during the collision and underwent subsidence during the collision, similar to the Australian active margin and Halmahera arcs in the southwest Pacific. The timing of the subsidence is constrained by three new ages of volcanic rocks in the Victoria Arc (457 ± 2; 456.8 ± 3.1; 457 ± 3.6 Ma) that immediately predate or are coeval with deposition of the Caradoc black shale. In contrast the Red Indian Lake Arc contains a sub-Silurian unconformity and a distinct lack of Caradoc black shale, suggesting uplift during the collision. The emergent peri-Laurentian terranes provided detritus into the newly created basin above the Victoria Arc. The evidence of this basin is preserved in the Badger Group, which stratigraphically overlies the peri-Gondwanan Victoria Arc but incorporated peri-Laurentian detritus. Thus the Badger Group forms a successor basin(s) over the Red Indian Line. Following the collision, subduction stepped back into an outboard basin, the Exploits-Tetagouche backarc, closing the Iapetus Ocean along the Dog Bay Line in the Silurian. Correlative tracts in the Northern Appalachians and British Caledonides support the Ordovician arc-arc collision; however, the evidence is less obvious than in Newfoundland.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".