Shallow, old and hydrologically inactive fault zones in the Appalachian orogen
Bibliographic record
Abstract
Understanding and quantifying fluid flow patterns and the permeability architecture of fault zones is crucial for petroleum development, the safety of nuclear waste repositories, and water resource management. Fault zones have complex permeability patterns that lead to faults acting as hydraulic barriers, conduits, or combined conduit-barriers. How faults affect groundwater flow at a regional scale (1-10km) is especially uncertain. The objective of this work is to determine whether faults affect regional patterns of groundwater discharge to lakes. We use naturally occurring geochemical tracers to quantify the groundwater discharge to lakes underlain by faults and not underlain by faults, and used groundwater discharge as a proxy for permeability. We sampled 54 lakes overlying the Paleozoic Appalachian fold and thrust belt in the Eastern Townships in Québec, and compared results to a previous study of lakes with low groundwater discharge in a crystalline watershed in the Canadian Shield not overlying regional fault zones. About half of the lakes sampled overly regional-scale thrust faults and the remaining lakes are not underlain by a fault. Lake water, inlet water and nearby groundwater were sampled in fall 2011 for radon-222 and chloride. Groundwater and surface water inflows have been quantified for each lake using a steady-state analytical mixing model of mass balance for both tracers, considering tracer input from precipitation, surface water and groundwater inflow, and loss through evaporation, gas exchange, radioactive decay, and surface water outflow. The uncertainty and physical plausibility of the analytical model results were examined using Monte Carlo analysis and numerical modeling, respectively. While the analytical model indicates non-negligible groundwater discharge for most of the lakes, the difference between the discharge rate into the lakes located on faults and the other lakes is not statistically significant. Numerical modeling suggests that fault zone permeability parameters are insignificant compared to watershed parameters such as lake or watershed area. However, the groundwater discharge rate in the Paleozoic fold-belt is significantly higher than lakes overlain crystalline bedrock. Thus, the rate of groundwater discharge is not significantly enhanced or diminished around the thrust fault zones, suggesting that in a regional scale, permeability of fault zones is not significantly different from the bedrock permeability at shallow depth in this old, tectonically-inactive sedimentary fold and thrust belt.
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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 | 0.001 | 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) | 0.000 | 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".