Age and composition of the Ruisseau Isabelle Mélange along the Shickshock Sud fault zone: constraints on the timing of mélanges formation in the Gaspé Appalachians
Bibliographic record
Abstract
Mélanges are common in the Humber and Dunnage zones of the Quebec Appalachians. Humber Zone mélanges are spatially associated with Taconian nappes and believed to be of tectonic origin. Dunnage Zone mélanges are interpreted as relicts of an Ordovician accretionary prism. The Ruisseau Isabelle Mélange (RIM) in the Gaspé Appalachians was first interpreted as a Dunnage Zone mélange, because of its tectonic position along the Baie Verte Brompton Line and lithological components, such as dark mudstone, blocks of ultramafic rocks, and greenish chromite-bearing sandstone. The RIM comprises sedimentary rock assemblages (Composite Shale, Black Shale, and Chromite-Bearing Sandstone assemblages), an Exotic Block, a Pebbly Mudstone Assemblage and slivers of Serpentinized Peridotite, and Metamorphic Tectonite. Most mélanges of the Dunnage Zone in the Quebec Appalachians contain partly similar rocks, but their age is not well constrained. Recent work on the RIM and Cap-Chat Mélange of the Humber Zone and new fossil finds in the RIM rock assemblages allow us to conclude that previous distinction between mélanges of the Dunnage and Humber zones on the basis of rock-type associations is not valid. According to the age of the RIM rock assemblages, mélanges in the northern Gaspé Appalachians continued forming after the mid-Caradocian, later than the Dunnage Zone mélanges of southern Gaspé Appalachians. The juxtaposition and structural features of the RIM rock assemblages result from repeated faulting along the Shickshock Sud fault from Late Ordovician to Middle Devonian.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".