40AR-39AR AND U-PB AGE CONSTRAINTS ON THE TRIASSIC-JURASSIC AND NORIAN-RHAETIAN BOUNDARIES, NORTHERN VANCOUVER ISLAND, CANADA
Bibliographic record
Abstract
40Ar-39Ar and U-Pb dating of Late Triassic-Early Jurassic sedimentary and intrusive rocks in the Wrangellia Terrane, northern Vancouver Island, has placed constraints on the absolute age of the Triassic-Jurassic (Tr-J) and Norian-Rhaetian (N-R) boundaries. Classic Wrangellian stratigraphy (Jones et al., 1977) is represented on Vancouver Island by mid- to Late Triassic rocks of the Vancouver Group, comprising Karmutsen flood basalts (Ladinian-Carnian) and platformal Quatsino limestone (Carnian-Early Norian), succeeded by latest Triassic (Carnian-Rhaetian) volcanic-sedimentary sequences of the Parson Bay Formation at the base of the Late Triassic-Middle Jurassic Bonanza Group (Nixon and Orr, 2006). A stratigraphic section (327 m) through strata of the Parson Bay Formation was measured west of Kathleen Lake (92L/6) where the succession is affected by localized, distal skarn alteration associated with nearby intrusions of the Early to Middle Jurassic Island Plutonic Suite (Nixon et al., 2006). Parson Bay strata in the measured section comprise thin to medium bedded, impure limestone, calcareous mudstone, siltstone and minor shale interbedded with hornblende- and augite-bearing feldspathic wacke, crystal-lithic tuff and reworked equivalents, and minor volcaniclastic debris-flow deposits. The top of the section is overlain by a thick sequence (>1 km) of poorly bedded, waterlain volcanic breccias, lithic wackes and subaerial basaltic to andesitic flows; the latter represent the main phase of Bonanza arc volcanism. Bivalves and conodont faunas collected from Parson Bay sedimentary lithologies indicate an age range of (late)
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.003 |
| Science and technology studies | 0.004 | 0.001 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".