Microfacies and microstructures of subglacial and deglacial sediments from the Pingualuit Crater Lake (Ungava Peninsula, Canada)
Bibliographic record
Abstract
The Pingualuit Crater (Ungava Peninsula, Canada) hosts a freshwater basin in which a subglacial lake subsisted under the Laurentide Ice Sheet during the last glacial period. Microfacies and microstructures of a 9 m long sediment core are presented to discuss the depositional environment of deformed glacigenic and postglacial sequences deposited in the deep basin of the lake. Five distinct lithofacies are characterized. The range of glacial microstructures observed in the lower facies (Facies IV) reveals that high stress level occurred outside the crater during the formation of this diamicton released by the ablation of debris-rich basal glacier ice in an ice contact subglacial–proglacial lacustrine environment. The overlying subaqueous and glacigenic sediment gravity flow (Facies IIIb) is associated with a temporary absence of ice cover over the coring site, and likely results from the efflux plume and the associated suspension sedimentation produced during the retreat of the ice margin. Then, the finely laminated (<1–2 mm) and normally graded meltout silts (Facies IIIa) containing dropstones and load cast features suggest underflows in an unstable ice marginal lacustrine environment hydrologically separated from the retreating glacier but containing floating glacial ice blocks. Microstructures within occasional diamictic layers indicate sudden meltout deposits from these drifting ice blocks. The above finer-grained sediments (Facies Ib) lack typical glacial microstructures, marking the onset of postglacial organic sedimentation. These postglacial sediments are affected by post-depositional deformations due to an overlying rotational slide (Facies II) that may have perturbed the associated environmental record.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 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".