Paleoenvironmental fluctuations across the Jurassic–Cretaceous boundary, Scotian margin, Canada
Bibliographic record
Abstract
Two wells, Thebaud C-74 and South Desbarres O-76, were investigated to evaluate paleoenvironmental changes across the Jurassic–Cretaceous boundary on the Scotian margin, offshore Nova Scotia, Canada. A multi-technique approach using proxies of paleoredox (total organic carbon, total organic nitrogen, U, V, Mo, Cr, Fe, Mn, Th/U), productivity (δ13Corg, δ15Nair, Ni, Cu, P, Zn), terrigenous input (Al, Ti, Al/Ti, K/Al, total rare earth elements), and paleosalinity (B/Ga) was employed to identify a geochemical anomaly in both wells associated with the boundary. A shift to more reducing conditions and elevated productivity correlates with low terrigenous input at the start of the anomaly, followed by a shift of redox and productivity proxies to background levels and elevated terrigenous input and paleosalinity at the top of the anomaly. These correlative relationships are consistent in both wells, reflecting a transition to anoxic conditions at the start of the anomaly, predominantly driven by the consumption of oxidative agents due to a higher abundance of decomposing organic matter. Lack of correlation between productivity and terrigenous input proxies indicates that the increase in micronutrients driving elevated productivity is not related to an influx of terrigenous input, but rather upwelling. The positive correlation between terrigenous input and paleosalinity proxies suggests limited fluvial input. Results of this study were compared to other published studies through the same time interval and agree with the global paleoclimate and sealevel variations during the Late Jurassic and Early Cretaceous, suggesting reflection of global changes associated with the Jurassic–Cretaceous boundary.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| 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".