Cretaceous strike–slip displacement along the Porcupine fault system and potential links to the opening of the Canada Basin
Bibliographic record
Abstract
Tectonic models for the evolution of the Canada Basin of the Arctic Ocean posit Jurassic–Cretaceous counterclockwise rotation of the Arctic Alaska terrane away from the Canadian Arctic Islands, translation along a strike–slip fault system, or some hybrid combination of the two. Here, we present evidence for post-Devonian deformation within the Porcupine fault system of northern Yukon and Alaska, which forms the southeastern boundary of the Arctic Alaska terrane. Neoproterozoic–Cretaceous strata exposed within the fault zone record polyphase deformation related to strike–slip displacement. Muscovite 40 Ar/ 39 Ar data from two samples collected north of the Porcupine River produced plateau or plateau-like segments at ca. 342–367 Ma and younger steps at ca. 105 Ma, consistent with initial cooling after emplacement of the Upper Devonian Old Crow plutonic suite and later Cretaceous–Cenozoic partial resetting. In contrast, samples from within the main strand of the fault system yield complex spectra with single steps as old as ca. 1779 Ma, highlighting contrasting thermal histories across it and post-Late Devonian truncation of the Old Crow plutonic suite. The timing of Mesozoic deformation is better constrained by U/Pb dating of calcite veins within the fault system, which yield an age of ca. 121 Ma. Coupled with field observations of unambiguous strike–slip related deformation within the Porcupine fault system, these geochronological data are consistent with translational or hybrid models for the opening of the Canada Basin.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".