Stasis coupled to transgressive surfaces in a Silurian sand-rich tide-dominated deltaic succession (Balcarce Formation, Argentina)
Bibliographic record
Abstract
Stratigraphic and ichnological evidence of synoptic surfaces developed during stasis periods from deltaic successions is poorly reported. Synoptic surfaces representative of prolonged stasis are typically highly bioturbated. A combined sedimentological and ichnological analysis undertaken along a down-dip-oriented transect of the Balcarce Formation allows the identification of true substrates within a Silurian tide-dominated deltaic succession. The lower interval comprises regressive packages of prodelta fines grading to sand-rich compound-dune or tidal-bar-dominated delta-front facies. True substrates developed during prolonged stasis are recorded along two types of transgressive surfaces (S1 and S2). S1 separates thicker packages (5–15 m thick) and is correlated seaward over longer distances (up to 20 km) than S2, showing that S1 is of a higher order of magnitude than S2. Synoptic surfaces with suites illustrating the Phycosiphon ichnofacies are best preserved seaward, at the top of regressive cycles bounded by S1. Velocity fluctuations of tidal currents and the deactivation of migrating tidal bedforms during transgressions might have favoured stasis followed by hemipelagic sedimentation without erosion, and the development of true substrates. Although prolonged stasis mostly corresponds to transgressions (i.e. allogenic), some bioturbated layers may reflect short colonization windows opened at brief pauses in sedimentation during delta progradation (i.e. autogenic).
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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 | 0.001 | 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".