The stable isotope (C, O, S) record of Paleoproterozoic marbles, Scotland
Bibliographic record
Abstract
Paleoproterozoic marbles occur widely in NW Scotland. The isotopically heavy carbonate carbon ( δ 13 C >3‰) in marbles that characterizes the worldwide Lomagundi–Jatuli Event (2.3–2.05 Ga) is recognized in the Laurentian Foreland, the Moine Nappe and the Sgurr Beag Nappe, over a 150 km transect across the Caledonian thrust belt. A light oxygen isotope composition distinguishes marbles that have been sheared and retrogressed by ingress of meteoric water, possibly during both Laxfordian and Caledonian orogenesis. The shearing of marbles also contributed to graphite formation (mean δ 13 C −7.2‰). Pyrite in the marbles contains isotopically heavy sulfur, typical of Paleoproterozoic diagenetic sulfides precipitated from low-sulfate seawater. These data show that the c. 2 Ga marbles in Scotland are a high-quality archive of information on their depositional and post-depositional history. The data emphasize a continuum of a Paleoproterozoic marble–graphite–sulfide-bearing assemblage from eastern Canada and Greenland through Scotland to Scandinavia.
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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) | 0.002 | 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".