A reexamination of Pleistocene tunnel valley distribution on the central Scotian Shelf
Bibliographic record
Abstract
Tunnel valleys are an erosional channel characterized by anastomosing, steep-sided channel systems formed by subglacial, confined meltwater flow. Our study uses two-dimensional (2D) industry reflection seismic on the Scotian Shelf near Sable Island to better constrain the geometry of tunnel valleys in the area. Here, U- to V-shaped buried channels north and west of Sable Island extensively branch, reconnect, and meander. They average 2–5 km wide and 150–700 m deep (below sea level) and have a dominantly north–south orientation. Immediately to the south and southwest of Sable Island, the channels become narrower (1–1.5 km), shallower (300–400 m maximum) and more widely spaced. Multiple tunnel valley generations may be present, but could not be separately mapped. There is a notable gap of 20–30 km between the ends of the detectable tunnel valleys and the shelf edge south of Sable Island. An exception is erosive features at the shelf edge at the head of Logan Canyon, but these channels are disconnected from the tunnel valley network further north and may not be tunnel valleys. The reason for the gap south of Sable Island is not clear; however, we do not believe it is due to data coverage or resolution issues. If the tunnel valleys genuinely end south of Sable Island, then the gap between them and the shelf edge means that between The Gully and Logan Canyon these subglacial meltwater channels did not empty directly at the shelf edge. This implies direct meltwater and sediment delivery by tunnel valleys to the Scotian Slope during the Pleistocene may have been limited in this area.
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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 | 0.001 | 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".