Cretaceous to Miocene exhumation of the Purcell Mountains, southeastern British Columbia
Bibliographic record
Abstract
The southeastern Canadian Cordillera records post-orogenic extension and core complex formation west of the Rocky Mountains. Geochronology and emplacement depth estimates of intrusions revealed that the Purcell Mountains, located on the interface between the Rocky Mountains and core complexes in the in the Selkirk and Monashee Mountains, underwent >10 km of exhumation since the latest Cretaceous. We investigate the Cenozoic exhumation history of the Purcell Mountains by combining metamorphic petrology and low-temperature thermochronology. We first determine the emplacement depths of two intrusions that span most of the width of the Purcell Mountains. Observed mineral assemblages along six transects through the contact aureoles range from cordierite + andalusite-bearing assemblages in the eastern White Creek aureole to staurolite + andalusite-bearing assemblages in the western Fry Creek aureole, suggesting emplacement depths that range from 8.3–13.6 to 10.5–14.7 km, respectively. The post-emplacement cooling history is assessed using zircon and apatite (U–Th)/He and apatite fission track thermochronology. These data indicate that 6–8 km of exhumation occurred in the Purcell Mountains between 66 and 30 Ma with accelerated rates between 40 and 30 Ma. An additional 3–6 km of exhumation is recorded between 30 and 0 Ma on the western flank of the Purcell Mountains suggesting reactivation along the Gallagher fault zone. In contrast, an intrusion in the western Rocky Mountains records 2–4 km of exhumation in the Late Cretaceous (108–66 Ma), <2 km between 66 and 40 Ma, and 2–3 km during the 40–30 Ma accelerated phase.
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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 | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 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) | 0.004 | 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".