Precambrian snapshots: Morphodynamics of Torridonian fluvial braid bars revealed by three‐dimensional photogrammetry and outcrop sedimentology
Bibliographic record
Abstract
Abstract Pre‐vegetation fluvial channels have long been considered predominantly sheet‐like in geometry, owing to hydraulic sections that rapidly widened rather than incise during floods. This motif has been paralleled to that of modern dryland rivers subject to sharp discharge fluctuations during ephemeral floods. However, a number of Precambrian fluvial successions have been recently appraised as the product of deep‐channelled systems characterized by relatively stable – probably perennial – discharge regimes. One such example is the ca 1·0 Ga Applecross Formation, part of the well‐studied Torridon Group of Scotland. To contribute to this debate and to provide refined morphodynamic models for the Applecross Formation, this article presents an integration of three‐dimensional photogrammetry and outcrop sedimentology applied to key exposures at Stoer Peninsula, north‐western Scottish Highlands. Analysis of selected sandbodies reveals that high‐relief fluvial sand bars, both mid‐channel and bank‐attached, evolved within deep, braided‐channel belts. These bars grew through complex mechanisms of accretion and reactivation related to different flood stages: upstream and downstream accretion probably occurred during waning‐flood stages characterized by high hydrograph levels and abundant sediment availability; lateral accretion took place during later waning‐flood stages, and it was associated in some cases with helical recirculation and increase in bend sinuosity. Overall, the depicted morphodynamics are consistent with prolonged flood events that cannot be reconciled with sharply fluctuating discharge regimes. Critical comparisons between the internal geometry of the studied bars and modern counterparts corroborate the findings herein. Thus, this study recommends stricter comparisons between the products of modern braided channels and Precambrian fluvial rock records featuring thick and well‐developed bar forms.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".