`Molar‐tooth microspar': a chemical explanation for its disappearance ∼ 750 Ma
Bibliographic record
Abstract
Molar‐tooth structures are intricately crumpled, microsparry calcite fissure fills that formed during the Precambrian. Strontium isotope stratigraphy constrains the last occurrence of volumetrically significant molar‐tooth structure (MT) in the geological record to ∼ 750 Ma. Although the disappearance of MT is commonly ascribed to the influence of metazoans on sediment cohesion, this now seems less plausible because there is no evidence for significant sediment disruption by metazoans before ∼ 550 Ma. It is proposed here that the most likely alternative explanation for MT disappearance is a change in ocean chemistry. A decrease in CaCO3saturation and/or an increase in the concentration of precipitation inhibitors in mid‐Neoproterozoic seawater may have contributed to MT disappearance, and might also help to explain the approximately contemporaneous decline in stromatolite diversity.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".