Character and origin of thick sandstone bodies in the Middle Triassic Doig Formation of Western Canada
Bibliographic record
Abstract
Within the Middle Triassic Doig Formation of western Canada there are thick sandstone bodies encased in muddier sediment, for which the name "anomalously thick sandstone bodies" (ATSBs) has been coined. Twenty years of investigating these thick sandstone bodies has not resulted in a consensus but there are a number of common points between the various studies that may help formulate a reasonable hypothesis for their origin. Many authors have interpreted the facies within the sandstone bodies to be shoreface deposits, although incised-valley fills (estuarine) and deltaic deposits also have been cited. Another common element is that the thick sandstone bodies were deposited during a transgressive-regressive period. The main point of contention is how these ATSBs relate to the adjacent strata, were they deposited contemporaneously or are they younger? Abrupt basal contacts, apparently abrupt lateral contacts, and stratigraphic relationships favour the sandstone bodies to be post-mudstone deposits, formed during late regression. If they are post-mudstone deposits how can an isolated, thick sandstone body be produced? A number of authors have suggested that the ATSBs were deposited in structurally created depressions (slumps or growth fault grabens), accounting for the thickness, isolation, abrupt appearance, and variable shapes and sizes. Based on the data produced to date the most probable explanation for the origin of the ATSBs is that during late regression slumps and/or growth fault grabens formed on a muddy, pre-existing shelf and were filled by sandy sediment. Initial deposits are commonly debris-flow and/or slump deposits that filled in the deeper parts of the depression. As the depression filled, sediment entered wave and current influenced water depths and more typical shoreface deposits began to form. As regression proceeded some of these sandstone bodies were truncated by a regressive surface of marine erosion curtailing deposition within the depressions. Finally, base-level rise initiated transgression and all ATSBs and adjacent sediment are capped by a thin veneer of transgressive sediment.
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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 | 0.003 | 0.003 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".