Stratigraphy, palaeogeography and evolution of the lower Nanaimo Group (Cretaceous), Georgia Basin, Canada
Bibliographic record
Abstract
Abstract The Cretaceous lower Nanaimo Group in the Georgia Basin, Canada comprises multiple depositional phases with distinct depocentres that accumulated in a tectonically active forearc basin setting. Basal coarse‐clastic strata are preserved in paleotopographic depressions and grade upwards into coal‐bearing coastal plains and shallow‐marine deposits. Coal‐bearing and shallow‐marine strata grade laterally into and are overlain by, regionally extensive mudstones and turbidites deposited in deep water. A glauconitic sandstone bed within the deep‐water strata is interpreted as a condensed section and underlies a major disconformity that developed during a pause in the deposition of the lower Nanaimo Group. A second major coarse‐clastic succession occurs hundreds of metres above the glauconite bed in the central Georgia Basin and comprises conglomerate, sandstone, mudstone and coal deposited in continental depositional environments. The shift in sedimentation from the northern Georgia Basin to the central Georgia Basin is interpreted to record the emergence of an island (Nanoose Uplift) in the central Georgia Basin that acted as a major sediment source to the adjacent depocentres. The stratigraphic break between the coal‐bearing coarse‐clastic strata in the northern Georgia Basin and the significantly younger coal‐bearing coarse‐clastic strata in the central Georgia Basin indicates that the lower Nanaimo Group was deposited in distinct depocentres. Between the older, coarse‐clastic strata in the north and younger, coarse‐clastic strata in the central Georgia Basin, we hypothesize that a major deepwater canyon system (Qualicum Canyon) existed and transferred sediment from the semi‐restricted Georgia Basin to the Pacific Ocean to the west. Development of the Qualicum Canyon and exposure of the Nanoose Uplift during deposition of the younger, central coarse‐clastic strata suggests that syntectonic activity drove basin uplift and erosion and this occurred throughout the deposition of the lower Nanaimo Group.
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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 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".