A Late Jurassic to Early Cretaceous record of orogenic wedge evolution in the Western Interior basin, USA and Canada
Bibliographic record
Abstract
The Late Jurassic to Early Cretaceous fill of the Western Interior foreland basin is characterized using geochronological data in order to assess the stratigraphic expression of wedge-top geomorphology, as controlled by sediment cover and denudation. In northern Montana, USA, and Alberta, Canada, wedge-top deposits are poorly preserved; however, their former presence may be inferred from the detrital record in the foreland basin. We present new U/Pb detrital zircon data from nine samples collected near Great Falls, Montana, augmented with field data. The stratigraphy at Great Falls is characterized by Late Jurassic marine and nonmarine deposits, which are truncated by a basinwide sub-Cretaceous unconformity. Aptian and lower Albian strata overlying the unconformity are dominated by nonmarine deposits, which transition up-section into a predominantly marine succession related to a major transgression of the Boreal Seaway in the Albian. Detrital zircon grains from Great Falls strata yield age spectra that can be subdivided into three groups using multidimensional scaling. Group 1 is characterized by diverse zircon populations, which are interpreted to record recycling of pre-Cordilleran sedimentary strata transported via foreland basin-axial river systems with headwaters in the southwestern United States. Group 2 is characterized by the dominance of Mesozoic detrital zircon grains, which are interpreted to record sediment dispersal by fluvial systems with headwaters in the Cordillera. Group 3 is intermediate between groups 1 and 2, based on its proportion of Mesozoic zircon grains. This group records a diversification of the provenance from one dominated by Cordilleran igneous rocks to include recycled sedimentary strata.
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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 | 0.002 |
| 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) | 0.001 | 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".