Assessing the role of anoxia as an extinction driver in shallow marine basins during the Permian–Triassic mass extinction.
Bibliographic record
Abstract
The Permian–Triassic mass extinction led to the loss of 80-90% of marine species making it the most catastrophic extinction of the Phanerozoic. The Permian-Triassic transition is characterized by a major clime warming event, major environmental upheaval and a high magnitude mass extinction event. The associated expansion of oxygen minimum zones, even into shallow waters, is commonly considered as a global driver of this extinction. However, while the intensification of deep-water anoxia has been demonstrated utilising U isotopes at multiple sites globally, recent studies have shown increasing evidence for spatial and temporal variability in shallow marine redox conditions across the Permian–Triassic transition. This highlights the need to constrain local redox conditions for shallow marine basins to determine if they were affected by anoxia and to link local redox changes, if any, back to the timing of the extinction event. Here, we present redox sensitive element (Re, V, U and Mo) and rare earth elements and yttrium (REY) data from three shallow marine basins, located in the western Paleotethys (Dolomites, Italy), Neotethys (Antalya, Türkiye), and the Barents Sea (Svalbard, Norway) to understand the role of oxygen availability as an extinction driver in different environmental and latitudinal settings. At all three sites, redox sensitive metal enrichments were observed before the onset of the extinction, suggesting deoxygenation, potentially creating anoxic conditions. However, these enrichments appear to be lithology- rather than redox-driven in the Svalbard section and are not persistent within the Dolomites sections, suggesting only episodic deoxygenation. Furthermore, the Dolomites and Antalya sections generally display lower metal enrichments starting at the extinction onset, suggesting lower oxygenation before the extinction than during it. Seawater-like REY patterns were not preserved at all sections, however, all three localities included sections characterized by negative Ce anomalies typical for oxic seawater conditions during the extinction. This suggests that anoxia was not a driving extinction factor in these shallow marine ecosystems, indicating other extinction mechanisms should be considered.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".