Detailed measured sections, bedrock aquifer/aquitard facies and potential bedrock aquifer systems of the Upper Cretaceous Nanaimo Group, Nanaimo Lowland, eastern Vancouver Island, British Columbia, Canada
Notice bibliographique
Résumé
Rapid population growth and expanding commercial developments are, and will continue to, put pressure on the limited groundwater resources of the Nanaimo Lowland. This study focused on the characterization of the bedrock aquifer potential of the Upper Cretaceous Nanaimo Group as a likely target of importance. This unit is a thick succession of 11 intertonguing sandstone-dominated and shaledominated formations, of which only the lower 8 are present in the defined study area. The field study on eastern Vancouver Island incorporated observations from 61 surface outcrops and 1 subsurface core, comprising a total of 2480 m of measured section from all 8 formations in order to qualitatively evaluate the aquifer potential of these rocks. The Nanaimo Group displays a prominent regional-scale stratigraphic architecture of alternating coarse-grained (potential regional aquifer zones) and fine-grained (potential regional aquitard zones) units. The irregular basal unconformity surface, with fracturing, high relief and weathered regolith forms a significantly-enhanced regional aquifer zone in the subsurface, and a recharge zone at surface. The overlying sandstone-and conglomerate-dominated formations (Comox, Extension, Protection, De Courcy) each represent regional aquifer zones with significant groundwater potential, whereas the intertonguing shale-dominated formations (Haslam, Pender, Cedar District, Northumberland) each represent regional aquitard zones with significant sealing potential. These alternating units are interpreted to compose a series of 3 stacked regional Bedrock Aquifer Systems. The Lower Aquifer System (up to 200 m thick and heavily fractured) comprises the extensive basal unconformity plus the lower Comox coarse-grained sandstone and conglomerate fluvial facies plus the upper Comox fine- to medium-grained sandstone shoreline facies. These deposits are overlain by the Haslam Formation shale, up to 200 m thick, which forms a Regional Aquitard Zone and renders this System the highest potential for both subsurface aquifer storage which underlies the entire field area, and for surface recharge where it outcrops in the west. The Medial Aquifer System (up to 600 m thick) comprises a combination of Extension Formation conglomerate and coarse sandstone facies plus Pender Formation interbedded sandstone and siltstone plus Protection Formation medium- to coarse-grained sandstone. These units are overlain by the Cedar District shale, up to 300 m thick, which forms a Regional Aquitard Zone that seals this very thick, but heterogeneous, significant Aquifer System which underlies most of the eastern part of the study area. The Upper Aquifer System (up to 300 m thick) encompasses the De Courcy Formation coarse-grained sandstone which is locally overlain by the Northumberland shale (only 50-100 m thick in the study area) and forms a local potential aquifer zone in one specific area. However, the De Courcy is the only aquifer unit for which we have actual subsurface core data (sandstone secondary porosity ranges 2-10%, av. 6.8%, permeability ranges 3-105 mD, av. 24 mD) and therefore provides a crucial analogy for the likely characteristics of the others. Additionally, fracture-related porosity and permeability are undoubtedly important in the subsurface setting, but have not yet been adequately studied.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».