The enigmatic Tintina-Rocky Mountain Trench fault: A hidden solution to the BajaBC controversy?
Bibliographic record
Abstract
Paleomagnetic studies revealed that most Upper Cretaceous paleopoles in the North American Cordillera are anomalously shallow relative to those obtained from equivalent-age rocks of cratonic North America. This was interpreted to signify >1000km of terrane migration along the north-trending paleomargin, yet geologists were unable to find the faults along which such migration might have taken place. This led to the BajaBC controversy, which has now bedeviled Cordilleran geologists for 50 years without a solution. The >3000 km-long Tintina–Rocky Mountain Trench is one of the longest continental valleys in the world and in the north it contains the large-magnitude Tintina fault, yet in the south is widely believed to only contain normal faults. I use structural, stratigraphic, and temporal data to show that as it passes southward, the strike-slip fault, active from about 70-58 Ma, was progressively overrun by NNW-trending NE-vergent Eocene thrust faults, which buried the strike-slip fault. After thrusting the area was exhumed 7-9 km, and eroded, shedding coarse debris eastward into the Western Interior basin, which left the older, dead trench variously filled. Farther south, the Rocky Mountain Trench vanishes near the Lewis and Clark lineament where it runs into the Basin and Range province, yet paleomagnetism and offset units suggest that it continues cryptically southward. Palinspastically restoring seven matching features, including two bands of Upper Cretaceous–Paleocene slab-failure magmatism, into a single zone, obviates the need for Laramide flat-slab subduction. Campanian shortening was generally E-W, orthogonal to the margin, but during the Maastrichtian-Paleocene, migration was dominantly transpressional, which led to emplacement of the allochthons, and distorted the Rocky Mountain foreland into a series of basement-cored uplifts
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.003 | 0.010 |
| Scholarly communication | 0.005 | 0.004 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.003 | 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".