Facies and architecture of river-dominated to tide-influenced mouth bars in the lower Lajas Formation (Jurassic), Argentina
Bibliographic record
Abstract
ABSTRACT The Middle Jurassic Lajas Formation in the Neuquén Basin of Argentina has been considered an ideal analog for tide-dominated deposits because of the widespread presence of tidal sedimentary structures and its heterolithic nature. Outcrops of the Lajas in the Los Molles area provide excellent exposures allowing both sedimentary structures and large-scale architectural information to be documented in detail. The extensive event bed stratification that characterizes the delta front and interdistributary bay deposits is interpreted to be the result of river floods because of the sharp base, fining-upward grain size trend, and seaward-directed paleocurrent indicators within each bed. The absence of wave-generated structures precludes a storm wave origin for these beds. Interflood deposits have two forms. The first is fine-grained sandstone and siltstone that is highly bioturbated with no tidal structures and is indicative of an overall river-dominated system. The second is also finer grained than the river flood beds but shows distinctive tidal features, indicative of a tide-influenced system during times when river influence was least. Mouth bars can be classified as purely river-dominated or river-dominated with tidal influence, depending on the type of interflood beds present. Tide-influenced mouth bars tend to be muddier, with more internal flow baffles or barriers and a lower-angle dip than their river-dominated counterparts. This study suggests that heterolithic successions containing pervasive tidal structures need not be tide-dominated because not all tidal structures are of equal importance in environmental interpretations. Their location (in river flood layers versus interflood layers) can be used as a methodology for determining the dominant and subordinate processes responsible for shaping the delta.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| 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".