The south-verging Isortoq Nappe of Baffin Island, Canada: implications on the framework of the northeastern Trans-Hudson Orogen
Bibliographic record
Abstract
The Isortoq Shear Zone (ISZ), a 100km-scale structure in northern Baffin Island, was originally identified through the interpretation of regional geophysical surveys. In the field the ISZ is cryptic, and its significance ambiguous with respect to the regional structural framework of northern Baffin Island. Mapping along the ISZ and within the spatially associated Archean Isortoq and Eqe Bay greenstone belts shows that the two belts form one continuous folded supracrustal package deformed by nappe tectonics likely during the early Paleoproterozoic Trans-Hudson Orogeny. The northern NE-striking, moderately SE-dipping Isortoq belt is structurally thinned, metamorphosed, sheared (by the ISZ) and overturned, with strata younging down-section to the NW. In contrast, the southern NE-striking, steeply dipping Eqe Bay belt is structurally thickened, comparatively less metamorphosed, exhibits weaker deformation, and stratigraphically youngs to the SE. New mapping and available geophysical data show that the two belts are folded around a hinge zone located offshore to the SW, and together form an asymmetric synformal anticline. Structural and stratigraphic relationships are consistent with the fold forming part of the lower limb of a map-scale southeast-verging nappe, with the ISZ formed at the base of this nappe as a consequence of horizontal transport. The Isortoq Nappe occurs along strike with SW-verging Rinkian nappes exposed >200 km to the NE, on Baffin Island and in Greenland. This implies that south-verging tectonics during the THO, opposed to and predating the dominant N-verging nappes of the Foxe Fold Belt, are more important in spatial extent than previously considered.
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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 | 0.002 |
| Science and technology studies | 0.003 | 0.003 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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".