Sinistral shear zones along the central and southern portions of coastal British Columbia, Canada
Bibliographic record
Abstract
ABSTRACT Large-scale (>600–1100 km) left-lateral offsets during Late Jurassic–Early Cretaceous time have long been inferred to explain the distribution of terranes in the Canadian portion of the North American Cordillera, but identification of structures with the correct age, location, and magnitude to accommodate such large displacements remains a significant challenge. Previous studies along the coast of British Columbia identified an ~250-km-long system of orogen-parallel intra-arc sinistral shear zones that may have accommodated some of these predicted motions, but crosscutting relationships could only constrain an ~20-m.y.-long period of motion in the late Early Cretaceous at the end of shear zone activity (ca. 125–100 Ma). In this chapter, we present new mapping from the same region that more than doubles the documented extent of sinistral shear zones recognized by previous workers. Complementary structural analysis and U-Pb (zircon) geochronology on synkinematic and postkinematic intrusions confirm that most shear zones were active during Early Cretaceous time (ca. 112 Ma) and demonstrate that some were active during Late Jurassic to earliest Cretaceous time (ca. 165–143 Ma). This extended time of motion supports the hypothesis that large-scale (~800 km) sinistral motion occurred along the northern Cordilleran margin.
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How this classification was reachedexpand
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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| 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, unvalidatedMachine predicted; a candidate call from one teacher head, 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".