Chronostratigraphy of the Beaufort Formation, western Canadian Arctic Archipelago
Bibliographic record
Abstract
The Beaufort Formation (BF) braided river deposit contains exceptionally well-preserved logs, leaves, peat, insects, and vertebrate fossils that provide key evidence for Arctic environmental conditions during the Pliocene. Its wide geographic range along the western edge of the Canadian Arctic Archipelago suggests that its deposition and incision history were dictated by regional drivers of sediment transport (e.g., eustatic sea-level, permafrost thaw, ice sheet erosion, and dynamic topography). Hence, the BF provides clues about both environmental and depositional conditions, but available chronology in the last few decades has not been able to identify these as having occurred either 1) during the polar amplification of global warming (Pliocene Climate Optimum, 3.3-3.0 Ma) or 2) during the onset of northern hemisphere glaciations (Plio-Pleistocene transition, 2.6 Ma). We use cosmogenic nuclide burial dating at the southernmost BF locality (Ballast Brook on Banks Is.) to obtain: a) a minimum age of 2.72 (+0.34)⁄(-0.24) (1 σ) Ma, and b) a maximum catchment-wide paleo-erosion rate of 49-86 ± 2 cm/ka. The description of a previously unreported glaciofluvial gravel (which occurs at the same stratigraphic level as a potential ice-wedge pseudomorph and coincides with the base of a previously-mapped 3-km wide cut-and-fill channel) dates the earliest evidence of CAA glaciation, at 2.72 Ma. The presence of a large channel that runs parallel to the northern coast of Banks Is. also suggests that M’Clure Strait (and the Northwest Passage) was not open at that time. Furthermore, such a large (correlative with part of the 3-km Iperk Formation offshore) and quick (49-86 ± 2 cm/ka) deposition event must have required the stripping of unconsolidated material (e.g, part of the Eureka Sound Group or Hassel and Isachsen Formations). The deposition system was likely a transport-limited system, and like the White Channel Gravels of the Yukon (Hidy et al. 2013), may have been controlled by changing climate in the Pliocene (e.g., melting permafrost, increased precipitation).
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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 | 0.005 | 0.005 |
| Science and technology studies | 0.004 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".