Re-evaluating the Paleogeography of the River-dominated and Wave-influenced Ferron Notom Delta, Southern Central Utah: an Integration of Detailed Facies-architecture and Paleocurrent Analysis
Bibliographic record
Abstract
Abstract This study re-evaluates the paleogeography of a river-dominated and wave-influenced deltaic system in a single parasequence (6a) of the Cretaceous Ferron Sandstone, south-central Utah, which was previously interpreted as a typical asymmetric delta. The conceptual asymmetric-delta model of Bhattacharya and Giosan (2003) has been widely applied to interpret ancient deltaic systems. However, reconstructed paleogeographies relying on this conceptual model are commonly not scaled to the architectural elements, which could possibly lead to inaccurate interpretations, especially when data are relatively sparse. The extensively exposed Ferron Sandstone outcrops provide an opportunity to demonstrate how detailed facies-architecture work can be integrated with regional facies relationships to elucidate a properly scaled paleogeography. Seven facies associations (FA) are identified in parasequence 6a and are arranged into two distinctively different successions. The river-dominated succession consists of prodelta, distal delta-front, proximal delta-front, and terminal-distributary-channel FA, while the wave- and storm-dominated succession comprises offshore-shelf, lower-shoreface, and upper-shoreface FA. The river-dominated succession is muddier and less bioturbated than the wave- and storm-dominated succession. Facies-architecture analysis shows that the river-dominated proximal delta-front facies consists of mouth-bar and terminal distributary-channel elements that are not seen in the wave- and storm-dominated facies. The scales of mouth bars and terminal distributary channels suggest that they are rather small features compared with the river-dominated delta lobe, which is incompatible with the simple bar-elongation asymmetric-delta model presented by Li et al. (2011). Instead, parasequence 6a is interpreted to be a valley-fed, river-dominated symmetric delta protected from waves by an updrift barrier system, which is analogous to the modern Mongky river delta on the west coast of Madagascar. The progressive change in orientation of west-directed mouth bars, to north-directed and east-directed lobes around the periphery of the river-dominated delta, indicates a highly radial Lafourche-type delta. Moving away from the protection of the barrier system, there is a gradual change from highly river-dominated facies to increasingly wave- and storm-influenced facies toward the southeast. Due to the entrenched nature of the feeder river associated with an incised-valley system, the parasequence 6a delta was bifurcation-dominated rather than avulsion-dominated. This study shows that it is critical to integrate detailed facies-architecture analysis in order to reconstruct properly scaled paleogeographies and hypothesizes that stable bifurcation-dominated deltas should be more common than avulsion-dominated deltas in a lowstand delta system due to the entrenched nature of the feeding trunk river, which inhibits avulsion.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".