Pennsylvanian–Permian Aragonite to Calcite Sea Transitions in the Sverdrup Basin (Arctic Canada) and Cantabrian Basin (northern Spain)
Bibliographic record
Abstract
Detailed facies analysis of Carboniferous–Permian strata in the Sverdrup Basin (Arctic Canada) and Cantabrian Basin (northern Spain) has led to the recognition of short-lived calcite seas within a first-order aragonite sea. The first return to calcitic conditions is documented in Lower Pennsylvanian carbonate rocks and lasted approximately 4–6 Myrs based on the replacement of aragonitic algae and tangential ooids by calcitic algae and radial ooids in shallow water facies. A second return to calcite sea immediately after the Carboniferous–Permian boundary is documented within an individual cyclothem, ~400,000 years in duration, through a similar shift to calcitic biotic and abiotic elements. These findings indicate higher-order calcite-aragonite episodes may occur during first-order oscillations and are likely influenced by a variety of mechanisms such as magnesium to calcium ratio (Mg:Ca), pCO2, temperature, and carbonate saturation among others. In this study, both the Early Pennsylvanian and Early Permian returns to calcite seas are attributed to increases in atmospheric CO2 due to contemporaneous volcanic activity. As a result, excess CO2 was buffered through the shoaling of saturation horizons in the ocean resulting in the non-precipitation and/or dissolution of the more soluble mineral phases such as aragonite and high-Mg calcite. A very shallow aragonitic zone is inferred in the Sverdrup Basin compared to a slightly deeper interval in the Cantabrian Basin, which is due to the higher paleolatitude of the Sverdrup Basin. Shoaling of aragonite and HMC saturation horizons is currently occurring in modern oceans due to the increased uptake of CO2 accelerating the rate of ocean acidification. Therefore, one of the long-term consequences of continued increases in anthropogenic CO2 could be the establishment of oceanic conditions like those of a calcite sea.
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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 | 0.000 |
| 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".