Buried valleys and till in the Canadian Prairies: geology, hydrogeology, and origin
Bibliographic record
Abstract
We review over 100 years of literature on Prairie buried valleys and till to provide a platform for future research and policy development. Buried-valley aquifers in the Prairies commonly yield abundant groundwater. They have distinct geologies and distinct stratigraphic settings, which impart them with distinct hydrogeological properties and give clues as to how they formed and filled. Prairie buried-valley aquifers are commonly encased in low-permeability strata: Cretaceous shale tends to underlie them and thick (10-300 m) low-permeability Quaternary till tends to overlie them. This reduces recharge, in rare cases nearly completely, while protecting groundwater resources from contamination and drought. It also tends to lead to highly mineralized groundwater chemistries. The stratigraphic positions of Prairie buried valleys also speak to their origin: those that subtend ('hang') from the bedrock unconformity were likely eroded by preglacial fluvial systems during late Tertiary uplift of the Rocky Mountains, whereas those that subtend from surfaces within the till package are likely glaciofluvial valleys eroded in proglacial spillway or tunnel-valley settings. Another key trait of Prairie buried valleys is that their fills tend to be heterogeneous and architecturally complex. Sand, gravel, mud, and diamicton are common; any one can dominate the fill at a given location. This heterogeneity, in conjunction with irregularity common to buried-valley bedrock floors, commonly causes aquifer compartmentalization and makes prediction of aquifer potential difficult prior to drilling. It also suggests that most Prairie buried valleys filled over time, and possibly over multiple glaciations, in multiple deposition environments.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.006 | 0.013 |
| Science and technology studies | 0.003 | 0.003 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".