Redox conditions across the Upper Cambrian in \nWestern Newfoundland, Canada
Bibliographic record
Abstract
The lower part of the Martin Point section (~ 110 m - rhythmites) spans the uppermost \nShallow Bay and lowermost Green Point formations (uppermost Franconian‒ \nlowermost Trempealeauan) of the Cow Head Group (western Newfoundland, \nCanada). It records two post-SPICE events (SPICE – Steptoean Positive Carbon \nIsotope Excursion) marked by negative δ¹³Ccarb excursions (NL1 and NL2) that were \nalso documented in South China. The petrographic and chemical screening of the \ninvestigated carbonate samples proves the preservation of at least near-primary \ngeochemical signatures. The proxies of weathering (e.g., Mn, Fe, Al, and ΣREE), \nbioproductivity (e.g., δ¹³Corg, TOC, P, Ni, Zn, and Cu), and paleoredox (e.g., Cr, \nTh/U, Ce/Ce*) have been utilized to reconstruct the paleoenvironmental conditions \nduring the post-SPICE events. The TOC, P, Ni, Cu, Cr, ΣREE, Mn, Fe, and U \nenrichment-factor profiles exhibit a positive pulse at the base of NL2 (upper negative \nδ¹³Ccarb excursion), followed by a drop. This might have resulted from shoaling \norganic-rich anoxic waters into an oxygenated shallow environment during \ntransgression, which led to a negative shift in the δ¹³Ccarb and a decrease in TOC \ncontents as well as an increase in the δ¹³Corg. The correlated enrichment in Zn and \nδ¹⁵Norg values and the Ce/Ce* around unity are consistent with the shoaling scenario. \nA similar scenario seems to be consistent with NL1 (lower negative δ¹³Ccarb \nexcursion) although the lower resolution of correlated proxy variations makes the \ninterpretations based on a few points and to be therefore taken with caution. \nThe upper part of the Martin Point section spans the upper Martin Point \nMember (upper Furongian, ~90 m) of the Green Point Formation of the Cow Head \nGroup. It records the HERB event (HERB - Hellnmaria-Red Tops Boundary) marked \nby a negative δ¹³Ccarb excursion at the base of the Econodontus notchpakensis \nconodont Zone. The HERB paleoenvironmental proxy enrichment profiles exhibit \ncomparable patterns to those of the post-SPICE, which suggests that the HERB event \nstarted with a similar scenario of transgression and shoaling of organic-rich anoxic \nwater into the water settings. However, the TOC profile shows a small gradual \nenrichment (~1 %), above the peak of the excursion, correlated with a broad negative \nδ¹³Corg shift (~2 ‰), and a positive Al/Ti shift. This may suggest possible minor \ninterruptions by sealevel drop and/or an episode/pulse of enhanced wind-blown inputs \nof weathered terrigenous material.
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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 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".