The Neoproterozoic glacial broom
Bibliographic record
Abstract
Abstract Neoproterozoic snowball Earth events reflect globally frigid conditions thought to have stimulated changes in geochemical cycling with planetary biotic response. We investigated the impact of these events on sediment dynamics, focusing on the detrital zircon record within the Dalradian Supergroup of Scotland and Ireland. Utilizing U-Pb detrital zircon ages, we analyzed changes in sediment provenance throughout the stratigraphy via bootstrapped variance metrics. The coefficient of variance for the detrital zircon load exhibits a first-order increase stratigraphically upward, with marked changes at glaciogenic layers. Points of increased variance align with inputs of older detritus compared to lower, preglacial stratigraphic levels, suggesting intensified erosion and downcutting linked to wet-based glacial activity, with postglacial sediment redistribution. Average detrital zircon apparent density also changes through the stratigraphy, with implications for uranium cycling from the continents into the oceans. While early Ediacaran shale geochemistry implies postglacial oceanic oxygenation, loss of proportionally more uranium-rich detrital zircon across glaciogenic layers suggests that modification to continental weathering also fundamentally contributed to Neoproterozoic geochemical shifts.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".