Relict seawater as a source of stratified groundwater in glaciated estuarine valleys: an example from Fredericton Junction, New Brunswick
Bibliographic record
Abstract
Recent investigations of the local geology and hydrogeological environment for the Village of Fredericton Junction, New Brunswick, identified a lower bedrock aquifer as the main water supply aquifer for both municipal and domestic wells. Within the aquifer, potable water overlies brackish water that increases in salinity at depth. The aquifer is overlain mostly by fine-grained glacial sediments that limit recharge to the lower bedrock aquifer. Recharge to the bedrock aquifer primarily occurs at outcrops along local rivers and from deeper regional groundwater systems. While nearby rivers receive run-off from local roads and municipal areas, geochemistry of the brackish water does not support this water as a source of the saline contamination. Examination of drill records from groundwater exploration within the Carboniferous sedimentary bedrock of New Brunswick indicates that groundwater is commonly stratified, forming a surface zone of fresh water overlying a zone of saline water at depth. While saline intrusion of aquifers is known to be a hazard for coastal communities from disturbance to the freshwater/saltwater interface, drilling records indicate that glaciated estuarine valleys may be especially at risk to salinization exacerbated by unrestricted exploitation. Drilling data demonstrate that saline water is most frequently encountered along valleys that were estuaries during the Late Wisconsinan glaciation, approximately 14 000– 12 000 years ago. During that time, many inland valleys were open to the ocean and surrounded by masses of melting ice. It is proposed that saline water from that time has remained preferentially in pockets within the bedrock underlying these valleys.
 
 RÉSUMÉ
 
 De récentes études de la géologie régionale et du milieu hydrogéologique du village de Fredericton Junction, au Nouveau-Brunswick, ont permis de repérer une formation aquifère du substratum rocheux inférieur, qui est la principale source d'eau du réseau d'aqueduc municipal et des puits résidentiels environnants. Dans cette formation aquifère, l'eau potable est sus-jacente à l'eau saumâtre, laquelle gagne en salinité en profondeur. La formation aquifère est recouverte essentiellement par des sédiments glaciaires à grain fin qui limite la recharge à la formation aquifère du substratum rocheux inférieur. La recharge de la formation aquifère du substratum rocheux survient principalement par des affleurements rocheux observés en bordure des cours d'eau de la région et de réseaux hydriques souterrains régionaux plus profonds. Les rivières environnantes reçoivent les eaux de ruissellement des chemins et des approches de la municipalité, mais les propriétés géochimiques de l'eau saumâtre ne permettent pas de désigner cette eau comme la source de la contamination saline. L'examen des travaux de forage d'exploration d'eau souterraine dans le substratum rocheux du Carbonifère du Nouveau-Brunswick, indique que l'eau souterraine se présente souvent sous forme de nappes et forme un horizon d'eau douce qui se superpose à une zone d'eau salée située en profondeur. L'infiltration de l'eau salée dans une formation aquifère est certes un danger pour les collectivités habitant une zone côtière, eu égard à la perturbation causée par le mélange de l'eau douce et de l'eau salée, mais les données de forage indiquent que les vallées glaciaires estuariennes peuvent être particulièrement exposées à une contamination par l'eau salée, une situation que peut aggraver une exploitation non balisée des ressources en eau. Les données de forage indiquent par ailleurs que la présence de l'eau salée est surtout observée en bordure de vallées qui formaient des estuaires à l'époque de la glaciation du Wisconsin supérieur, il y a environ entre 14 000 et 12 000 ans. Au cours de cette période, un grand nombre de vallées à l'intérieur des terres donnaient sur l'océan et étaient entourées de masses de glace fondante. Il est suggéré que l'eau salée datant de cette époque a été confinée selon toute vraisemblance dans des poches du substratum rocheux sous-jacent de ces vallées.
 
 [Traduit par la rédaction]
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How this classification was reachedexpand
Direct model labels (unvalidated)
Per-model category and study-design labels from the labeling rounds. They are machine output, unvalidated, and the disagreement between models ships as data. No study design here is MEDLINE-validated yet.
| Model arm | Categories | Study design | Confidence |
|---|---|---|---|
| gemma | no category Domain: not available · Genre: Empirical About the Canadian research system: no · About a Canadian topic: yes | Observational | low |
| gpt | no category Domain: not available · Genre: Empirical About the Canadian research system: no · About a Canadian topic: yes | Observational | high |
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.008 | 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, unvalidatedLabeled directly by 2 models reading the full record.
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".