Crustal geometry and tectonic evolution of the Archean crystalline basement beneath the southern Alberta Plains, from new seismic reflection and potential-field studies
Bibliographic record
Abstract
Deep seismic reflection profiling of the southern Alberta crystalline basement, namely the Archean Medicine Hat block (MHB), has revealed that the crust is characterized by west- and southwest-dipping reflection fabrics, a layered lower crust, and geometric cutoffs that are interpreted to be remnants of a complex tectonic history. Upper to middle crustal dipping reflections are interpreted to be associated with Archean rocks drilled below the Western Canada Sedimentary Basin and their geometry is consistent with east- and northeast-verging imbrication. Layered lower crustal reflections of the MHB are interpreted as Early Proterozoic delaminated Loverna block crust and injected mafic material, based on geometric relationships, xenolith dating, and gravity modelling. The reflection Moho is diffuse below the MHB at ~15 s two-way time (~47 km). This is similar to estimates based on adjacent seismic refraction data and is up to ~8 km deeper than regions north of the MHB. The MHB crust is interpreted to have undergone two episodes of crustal deformation in the Precambrian: (1) Late Archean formation of the MHB crust by continental collision of two Archean domains along a crustal-scale ramp; and (2) Early Proterozoic crustal shortening associated with the formation of the Vulcan structure, the delamination of the Loverna block crust, and postcollisional injection of mafic melts beneath the MHB crust. Radiometric dating of lower crustal xenoliths suggests a significant Early Proterozoic thermal event in the deep crust beneath the MHB that is coeval with orogenic activity in the Trans-Hudson Orogen and the East Alberta Orogen.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".