The Pliensbachian-Toarcian (Early Jurassic) extinction: A North American perspective.
Bibliographic record
Abstract
Currently, it is believed that volcanogenic outgassing of CO2 during Karoo-Ferrar igneous province eruptions caused prolonged global warming and a multiphased extinction event during the Pliensbachian–Toarcian interval of the Early Jurassic. Warmer water temperatures are thought to have caused a release from the methane hydrate reservoir and global marine anoxia in the Early Toarcian (dubbed the Toarcian oceanic anoxic event). Recently, the timing and geographic extent of these events have been questioned, with emphasis placed on regional conditions in the Tethys Ocean area rather than global controls. Our study compares paleontological and geochemical data from western North America with previously established correlative data in Europe to provide a perspective on the duration, extent, and controlling mechanisms of this Early Jurassic extinction event. Our data indicate that during Pliensbachian–Toarcian time, concurrent with Karoo-Ferrar magmatism: (1) there were six globally correlative intervals of taxonomic diversity decline that constitute evidence of a multiphased extinction event; (2) there was a major disruption in the long-term δ13C profile (~3‰–7‰), suggesting volcanogenic CO2 outgassing as a preeminent factor driving global warming and mass extinction; (3) there was a large negative excursion in the Early Toarcian δ13C profile in two successions on Haida Gwaii (formerly known as Queen Charlotte Islands), Canada, suggesting global methane release; and (4) the northeast Panthalassa Ocean did not contain anoxic water during the Early Toarcian. Although the Toarcian oceanic anoxic event does not appear to have globally affected every marine environment in the same manner, it is possible that local anoxic water masses occurred in restricted basins outside the Tethys Ocean area.
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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 | 0.001 |
| 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".