Life in the Late Paleozoic ice age: trace fossils from glacially influenced deposits in a Late Carboniferous fjord of western Argentina
Bibliographic record
Abstract
The early Late Carboniferous rocks of the Guandacol Formation in western Argentina preserve the glacial to postglacial transition. In the study area, this unit has been divided in three intervals: 1) a lower diamictitic interval; 2) a middle interval chiefly composed of mudstone, and 3) an upper sandstone-dominated interval. The lower interval records infill of a fjord incised into the underlying Ordovician limestone. The middle and upper intervals reflect postglacial sedimentation. Four ichnotaxa, occurring as both discrete and compound trace fossils, are documented from the lower and middle intervals of the Guandacol Formation.Diplopodichnus biformisandCruziana diplopodan. isp. occur in the thinly bedded stratified diamictite in the upper section of the lower interval. These deposits record sedimentation from debris flows with dropstones reflecting overprinting of ice-rafting and rain-out processes.Cruzianacf.problematicaandRusophycus carbonariusare present in very-fine to fine-grained sandstone layers interbedded with dropstone-bearing mudstone in the lower section of the middle interval. These deposits record the interplay of suspension fall-out sedimentation, ice-rafting, rain-out processes, and storm waves. The presence of linguliformean brachiopods in coeval beds nearby strongly suggests marine influence and that brackish-water conditions prevailed during the early phase of the transgression. Harsh paleoenvironmental conditions may explain the small size of the trace fossils and the low ichnodiversity in comparison to that expected in fully marine environments. The morphology of the trace fossils as bilobate ridges and furrows ornamented with scratch marks indicates that the structures were produced by arthropods, most likely trilobites and/or notostracans. Although the possibility that different ichnotaxa have resulted from changes in burrowing behaviors can not be completely disregarded, the fact that distinctCruzianaichnospecies display non-overlapping facies distribution may suggest their production by different arthropods.
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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 | 0.001 | 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) | 0.002 | 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".