Deformation of Upper Carboniferous coal measures in the Sydney Basin: evidence for late Alleghanian tectonism in Atlantic Canada
Bibliographic record
Abstract
Upper Carboniferous (Stephanian) coal measures of the Sydney Basin are deformed by reverse faults and folds with dips of up to 50° on the limbs. These structures represent compressional or transpressional events (Donkin Episode) of unknown sequence and timing. Offshore swath-bathymetry data indicate that northwest-striking reverse faults are folded by prominent northeast-trending folds. Vitrinite reflectance patterns of oriented coal samples from the fold limbs are uniaxial negative, with minimum reflectance axes (Rmin) near-normal to bedding and fanning across fold axes. This pattern implies that the bulk of coalification took place through burial compaction without directed horizontal stress, prior to the deformation that produced the folds. Slight divergence between Rminaxes and poles to bedding may reflect slight tilting, associated with differential subsidence or early reverse faulting, before or during coalification, or may lie within analytical error. One moderately biaxial sample suggests that some deformation accompanied coalification locally. Available apatite fission-track data for the Sydney Basin indicate that cooling of the coal measures to below 100 ± 20°C was underway by the Middle to Late Triassic or earlier. Because cooling implies that coalification was largely complete, the fission-track results are compatible with latest Paleozoic or early Mesozoic deformation. We infer that the Donkin Episode represents late Alleghanian (Permian?) compression within the Appalachian Orogen. If so, the Sydney structures are manifestations of a little-known tectonic episode in Atlantic Canada. However, MesozoicCenozoic deformation cannot be ruled out.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".