Origin of shore‐normal channels from the shoreface of Sable Island, Canada
Bibliographic record
Abstract
A suite of modern, shore‐normal channels was discovered on the southern shoreface of Sable Island, Canada. Repetitive multibeam and side scan surveys of these features, as well as box coring and sampling, showed that the depressions were perennial features of the shoreface. They occurred in fine and medium sand and were most abundant in‐depths less than 20 m. They were up to 1 m deep and 50 m wide, increased in size seawards, and generally followed the seabed slope. The channels dominated the inner shoreface becoming wider and deeper seawards to depths in excess of 40 m. There is a continuum of scales in width and depth of these channels, the smallest of which are equated with gutters preserved in the geological record. The internal structure of the shoreface sediments where the gutters are found is characterized by normally graded tempestites composed of cut‐and‐fill structures overlying an erosion surface. Thus, the environmental setting, internal structure, and scale are similar to ancient counterparts. Gutters have been interpreted to result from downwelling over palaeo‐shorefaces during ancient storms [ Myrow , 1992b ]. The composition of gutter infill, as well as the stability, evolution, associated bed forms, and hydrodynamic conditions under which they formed, were examined to verify genetic interpretations of the ancient counterparts. The multisensor benthic lander RALPH was deployed within a field of shore normal channels for 17 days during late winter 1998. RALPH burst‐sampled flow at hourly intervals while imaging the seabed. Resulting sequential imagery revealed the genesis of a group of five gutters during storm spin‐down that was coincident with the formation of large‐scale wave ripples. This was followed by infilling of the gutters and wave ripple destruction within 20 hours by longshore sand transport. The gutters were located within, and parallel to, a larger channel (50 m wide and 0.50 m deep). They were formed by coastal set‐up and subsequent downwelling that was triggered by the rotation of storm winds from seawards (onshore wind) to landwards (offshore wind). The gutters formed within 2–3 hours during spin‐down of a winter storm under “live‐bed” conditions of sand transport. Wave height and mean tidal flows were well below those of the storm peak and so they were not directly responsible for creating the gutters. The mechanism we propose for the evolution of gutters supports the geological interpretations; that is, a storm‐driven, downwelling event as described by Swift and Niedoroda [1985] . However, the downwelling event appeared to take place suddenly (rapid acceleration in flow), briefly (few hours duration), and within narrow corridors guided by wider and deeper channels of the shoreface. High turbidity during the time of gutter formation leads us to believe that the phenomenon of inner shelf turbidity currents [as suggested by Walker , 1985 ] exists and may be instrumental in channel formation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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 teacher head, 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".