Molybdenum isotopic evidence for oxic marine conditions during the latest Permian extinction
Bibliographic record
Abstract
The latest Permian extinction (LPE), ca. 252 Ma, represents the most severe extinctionevent in Earth’s history. The cause is still debated, but widespread marine anoxicto euxinic (H2S rich) conditions, from deep to shallow water environments, are commonlysuggested. As a proxy for marine oxygen levels, we analyzed d98/95Mo of two LPEsections that represent a gradient in water depth on the northwest margin of Pangea.Results from deep-water slope environments show a large shift in d98/95Mo values from–2.02‰ to +2.23‰ at the extinction horizon, consistent with onset of euxinic conditions. Incontrast, sub-storm wave base shelf environments show little change in the molybdenum isotopic composition (–1.34‰ to +0.05‰), indicating ongoing oxic conditions across the LPE.These results indicate that areas of the continental shelf of northwest Pangea underwent massextinction under oxic conditions throughout the LPE event, and that shallow-water anoxiawas therefore not a global phenomenon.
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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 | 0.001 | 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) | 0.002 | 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".