Diverse products of near‐surface sediment mobilization in an ancient eolianite: outcrop features of the early Jurassic Navajo Sandstone
Bibliographic record
Abstract
ABSTRACT The Navajo Sandstone of the Colorado Plateau, USA, displays a wide range of soft‐sediment deformation (SSD) features, including decametre‐scale features that have not been found in any modern desert environment. Laboratory simulations and partial analogues from other depositional environments suggest that these features derived from episodic liquefaction and fluidization of unconsolidated dune deposits. Outcrop details at many locations preserve the effects of fluid‐escape dynamics through porous, permeable, well‐sorted sand, which was partitioned by subtle textural changes at depositional boundaries between successive dune deposits and, less commonly, by distinct lithofacies changes marking the interface between wet and dry depositional environments. Extreme deformation and turbulent sediment flow have effaced primary structures in some zones of deformation; but other sites preserve the ductile modification of primary structures. Some outcrops preserve evidence of dramatic alterations in topography and sedimentation patterns due to localized compaction and large, subsurface, sediment displacements. Particularly notable among these extraordinary features are those representing the foundering of active dunes, sediment eruptions, and the subsidence of interdune surfaces in the ancient erg. The distinctive patterns of deformation in the Navajo Sandstone, interpreted in the context of its primary sedimentary architecture, provide unique insights into environmental conditions in the region during the Early Jurassic. Widespread ductile deformation in the Navajo indicates extraordinarily wet conditions for an active dune environment. The truncation of successive deformation features by deflation surfaces establishes the episodic nature of deformation in the unit and also suggests climatic variability. The widespread, episodic occurrence of SSD features, viewed within the seismic context provided by palaeotectonic reconstructions, strongly suggests that earthquake triggering of localized liquefaction controlled the distribution of deformation in this unit.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| 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) | 0.001 | 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".