Detrital zircon signatures of the southern Brooks Range: Implications for the Paleozoic assembly of Arctic Alaska and the Mesozoic opening of the Amerasia Basin
Bibliographic record
Abstract
Abstract Models for the assembly of the Arctic Alaska–Chukotka microplate suggest the juxtaposition of Laurentia- and Baltica-affinity terranes in the mid-Paleozoic. Subsequently, the Arctic Alaska–Chukotka microplate moved southward during the Mesozoic opening of the Amerasia Basin, approaching its present position. To refine these models, this study presents data on the provenance of rocks from the metamorphic core of the southern Brooks Range, elucidating the location of the Arctic Alaska–Chukotka microplate and its composite pre-Mississippian terranes during periods of Arctic tectonic reorganization. The recycling of Tonian–Ediacaran sedimentary and igneous rocks from the southern Arctic Alaska–Chukotka terrane and Arctic Russia across an Ediacaran to Cambrian unconformity, which developed after the Timanian orogeny, restores the southern Arctic Alaska–Chukotka terrane to the northern margin of Baltica during the Precambrian–Cambrian. A pre–Middle Devonian unconformity across Arctic Alaska is recorded in rift-related Middle Devonian to Mississippian(?) sediments. Erosion of genetically unrelated pre–Middle Devonian basement units and mixing of their detritus into localized Middle Devonian and younger rift basins confirm the presence of a major Paleozoic suture in the Arctic Alaska–Chukotka microplate, related to the Caledonain-aged deformation, that juxtaposed Laurentian, Baltican, and isolated intra-Iapetan magmatic arc–affinity terranes. Similar age spectra in Late Devonian sedimentary rocks from Arctic Alaska and Arctic Canada support models proposing that the Arctic Alaska segment of the Arctic Alaska–Chukotka microplate restores to the northern margin of Laurentia prior to the opening of the Amerasia Basin. The contact of pre-Mississippian terranes in Arctic Alaska supports a two-part opening model for the Amerasia Basin, restoring Arctic Alaska to an along-strike position with a correlative suture exposed in northernmost Ellesmere Island, Canada, by a rotational component linked to the opening of the Canada Basin together with a phase of opening perpendicular to the Lomonosov Ridge to restore the Chukotka portion of the Arctic Alaska–Chukotka microplate to the Lomonosov Ridge and northern margin of Baltica.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".