Record of climatic fluctuations and high pH weathering conditions in a thick Ordovician palaeosol developed in rhyolite of the Dunn Point Formation, Arisaig, Nova Scotia, Canada
Bibliographic record
Abstract
Abstract A thick Ordovician intra-rhyolitic palaeosol was studied to investigate the peculiarities of early Palaeozoic continental environments, shortly before the development of vascular plants, and to compare its pedogenic patterns with those of previously studied intra-basaltic profiles from the same succession. Well-defined K-eluviation from the top of the palaeosol is proportionally met by K-illuviation at the base of the profile, a pedogenic behaviour that was masked in the underlying intra-basaltic profiles due to subsequent eodiagenetic K-enrichment associated with rhyolite emplacement. Greater stability of K (and eventually Mg) than Si in the intra-rhyolitic profile suggests high pH soil water at the time of pedogenesis despite the low base contents of the acidic host rock, and despite evidence for humid weathering conditions. We also observe that, at the base and at the top of the profile, Al2O3/Zr ratios are substantially lower than those of the host rock, suggesting Al-leaching and therefore extreme weathering conditions, whereas the middle portion of the profile shows Al2O3/Zr ratios that are similar to those of the host rock, suggesting Al stability and therefore less extreme conditions. We interpret these variations in Al2O3/Zr ratios as signatures of a cyclic change from sub-humid periods during which Al was stable throughout the profile, to more humid periods with a well-defined seasonality, during which only the juvenile zone of weathering at the base of the profile could have developed sufficiently high pH during dry seasons for Al to be leached, leaving the Al2O3/Zr signatures from previous stages untouched higher in the profile.
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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 | 0.000 |
| 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".