“Sudbury Breccia” and “Huronian Breccia”: spatial, sedimentological, and structural evidence for separate distinct breccia-forming events
Bibliographic record
Abstract
Rounded argillite clasts within the lower Gowganda Formation of the Huronian Supergroup near Whitefish Falls, Ontario, have been historically mapped as Sudbury Breccia, implying that their formation was initiated by the Sudbury meteorite impact event. Alternative genetic models proposed to explain the breccia at Whitefish Falls include formation through intrusion of diabase into wet sediment accompanied by soft-sediment deformation events. Outcrops in the Whitefish Falls area contain clear evidence for early post-depositional fracturing: flow of argillites into brittle fractured sandstones. Linking these geological processes suggests that the formation of the breccia at Whitefish Falls was generated by faulting of the Huronian sedimentary basin during the sedimentation of the Gowganda argillites. Using a GIS approach to compare the distribution of known breccia bodies with mapped lithology and structure, it is apparent that the term Sudbury Breccia has been applied to two types of breccias. First, true Sudbury Breccia, which is characterised by rounded heterogeneous clasts in an aphanitic matrix, is only found in proximity to the Sudbury Impact crater. The distribution of the second, primarily sediment derived, type of breccia, as seen at Whitefish Falls, is strongly associated with mapped faults and regional-scale basement discontinuities, as defined by gravity and magnetic data. Since this type of breccia is present throughout the entire Huronian sedimentary sequence, the term “Huronian Breccia” is more appropriate. This breccia is not the result of a single geological event but rather episodes of fault activity, as the geometry of the Huronian basin evolved over time.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| 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".