Bibliographic record
Abstract
The Devonian to Carboniferous (DC) transition is marked globally by carbonate factories turnover, anoxia, profound unconformities and mass extinctions. Various authors have proposed global mechanisms such as meteorite impact, global climate cooling, anoxia, intensification of upwelling, etc. The DC boundary in western Canada and western United States has recorded this major Earth Systems change. Yet, a holistic study of this subject is non-existent. Sixteen sections across the DC boundary from Famennian to Viséan strata, in Alberta, Montana and Nevada were measured, sampled and analyzed. The DC sequence stratigraphy of western Laurentia was revisited based on microfacies analysis and field observations performed in these sections. The DC anoxia was also studied from five outcrop sections, providing the first coherent understanding of environmental changes along the continental margin of western Laurentia. Sediment provenance was examined based on detrital zircon analysis. Carbonate factories turnover and a depositional change from a Devonian warm-water carbonate ramp to a Carboniferous cool-water carbonate distally-steepened ramp were documented. Microfacies distribution in time was compared with geochemical proxies to emphasize the interaction between the biosphere, oceanography and palaeoclimate at the onset of the Permian-Carboniferous ice-house climatic mode. Two low-order T-R sequences were correlated from Alberta to Nevada. Results from this work provide clarification of the spatial-temporal extent of environmental changes and anoxia across Laurentia. This work demonstrates that these events are unrelated to the Hangenberg event recorded in Europe, as commonly suggested by various authors. Carbonate factories shut down and turnover, influx of westerly-derived sediments that are sourced from the Antler terranes, with northern affinities suggest that the Antler Orogeny, and associated plate tectonic reorganization, were the main contributors to the DC Earth Systems change in western Laurentia, rather than being part of a global event. This study demonstrates that the simple global-event paradigm across the D-C boundary does not adequately explain regional changes in the rock record.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".