Equatorial cold-water tongue in the Late Ordovician
Bibliographic record
Abstract
The eastern equatorial Pacific cold tongue (EEP-CT) today asserts a vital influence on ocean-atmosphere CO2 exchange and global climate patterns. Here, we report a similar equatorial cold tongue in the Late Ordovician peri-Gondwana region during drastic greenhouse-icehouse climate swings and the first mass extinction. Paleontological, sedimentological, and new stable-oxygen-isotope data from conodont apatite point to a change from warm-water to cool-water tropical depositional environments in the South China plate from Early to Late Ordovician. This apparently contradicts the current paleogeographic reconstructions of a coeval northward drift of South China from subtropical peri-Gondwana to the equator. The trend of climate cooling coincided with the origin and diversification of the Foliomena fauna in South China during the Late Ordovician, and the absence of reef-building sponges and corals. This was in sharp contrast with the Calathium calcareous sponge reefs in Early Ordovician warm-water settings. In this study, we compare the paleogeographic setting of the South China plate in the Late Ordovician with the EEP-CT today where cool-water depositional environments prevail because of cold upwelling and westerly currents.
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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".