Bibliographic record
Abstract
Mud-dominated point bars are widely accepted as recording deposition by tidal influence, bar tails or counter point bars. Less understood are muddy point bars that lack these depositional origins and otherwise have the geometry of more traditional sandy point bars. This study seeks the cause of these ‘muddy-normal’ point bars by field examination of a point bar with features and architecture consistent with sandy deposits but containing mud-dominated internal lithofacies. This study examines a point bar in Late Cretaceous fluvial strata of the Dinosaur Park Formation in the Steveville badlands of Dinosaur Provincial Park, Alberta. Strikes and dips, palaeocurrents, photo panoramas and stratigraphic columns are used to determine accretion trajectories and lithologic trends throughout the bar with a focus on sand vs. mud accretion and its relation to accretion trajectory. The point bar alternates between sand-dominated and mud-dominated accretion sets, with mud comprising over 50% of the point bar by volume. Accretion sets are defined by consistency in accretion dips. Both mud and sand beds within accretion sets have current ripples and cross sets indicative of deposition by transport. This suggests that the mud layers were deposited by active accretion events and are not simple drapes. Muddy accretion sets consistently have orientations reflecting bar translation (parallel with palaeodip) and sandy accretion sets consistently have orientations consistent with bar expansion (normal to palaeodip). These data suggest that the muddy vs. sandy accretion sets record toggling between sand-favouring bar expansion and mud-favouring translational growth vectors. This bar toggle explains how to generate a mud-dominate point bar with general lobate geometry without imposing tidal drivers, bar abandonment, or asserting a fully counter-point-bar interpretation. This toggling between expansion and translation records periodic upstream to downstream shift in the point of attachment for flow momentum to the cutbank that is probably caused by unstable flood discharge trends over the life of the bar. Bar toggle should be considered a growth vector option for point bars along with more established translation and expansion. The point bar also has a strong palaeoseismic imprint in the form of liquefaction features and a large lateral spread near the tip that is contemporary with late bar growth. The source of this earthquake is uncertain but could record a currently unrecognised intraplate earthquake source or, intriguingly, could be associated with the nearby Bow City impact structure which occurred in the same time frame.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".