Testing the Use of Anisotropy of Magnetic Susceptibility (AMS) in Determining Genetic Origins of Paleoproterozoic Diamictites
Bibliographic record
Abstract
The Huronian Supergroup (2.4-2.1 Ga) in Ontario, Canada is widely accepted as an important stratigraphic interval for interpreting Paleoproterozoic climate. This is because it contains some of the oldest glaciogenic rocks on the planet. However, massive and poorly-stratified diamictites in the Gowganda Formation of the Huronian Supergroup have varying depositional interpretations among sedimentologists (subglacial, rainout, sediment gravity flow etc.). Diamictites can occur from a variety of processes and, therefore, proper depositional interpretation is essential for unraveling detailed environmental conditions at the time of deposition. Anisotropy of magnetic susceptibility (AMS) looks at the orientation of magnetic particles within a rock and coupled with sedimentary investigation, can help interpret depositional processes. Rock magnetic data show that magnetism is carried by multi-vortex (titano)magnetite in fine-grained facies and includes the addition of a higher- coercivity contribution (potentially diagenetic goethite) in some sandstone facies. Most magnetic fabrics iii are oblate in shape and oriented transverse to flow, although vertical fabrics were found in sites that exhibited substantial deformation or dewatering. Results and observations from this project suggest that Gowganda sedimentation was dominated by sediment gravity flows, deposited on a marine post-glacial slope with a southwestern transport direction. Interpretation of depositional processes through a combination of AMS and sedimentologic observation provide a more comprehensive understanding of the environmental conditions controlling deposition, and in this case, painting a more elaborate picture of Paleoproterozoic climate transitions. In contrast with subglacially derived diamictites, which are deposited directly under glacial ice, those produced by sediment gravity flows suggest a more glacially distal to non- glacial environment. The presence of bedded diamictites, water escape structures, quarter structures around clasts, a general lack of shear horizons and striated/faceted clasts as well as an abundance of flow-transvers magnetic fabrics observed in most Gowganda facies suggest this more distal environment. However, subglacial deformation and deposition cannot be entirely ruled out for one oriented and striated boulder bed horizon producing flow-aligned magnetic fabrics; both characteristics of subglacial processes.
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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 | 0.001 | 0.002 |
| 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".