Reconstructing Early Phanerozoic intertidal ecosystems: ichnology of the Cambrian Campanario Formation in northwest Argentina
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Bibliographic record
Abstract
The Campanario Formation is the middle unit of the upper Lower to Middle Cambrian Mesón Group of northwest Argentina. This formation is interpreted as having accumulated in macrotidal shallow-marine environments with extensive tidal-flat areas flanked seawards by subtidal sandbar complexes. Shallow subtidal and intertidal sand-flat deposits are dominated by vertical domiciles of suspension feeders and passive predators of the Skolithos ichnofacies (Skolithos, Arenicolites, Diplocraterion). The ichnogenus Syringomorphaz also occurs in sand-flat facies, commonly forming high-density, monospecific assemblages. Mixed-flat deposits contain hurizontal feeding, locomotion and resting traces as diagnostic components. A relatively low-diversity Cruziana ichnofacies is present in these lower-energy deposits. This ichnofauna includes presurned trilobite trace fossils (Cruziana, Rusophycus, Diplichnites), structures produced by sessile cnidarians (Bergaueria cf. B. perata) and shallow burrows and trails of vermiform organisms (Planolites, Palaeophycus, Helminthoidichnites). Tiering in these tidal-flat deposits is relatively simple. Six ichnoguilds (Cruziana problematica, Palaeophycus, Bergaueria, Rusophycus leifeirikssoni, Syringomorpha and Skolithos) have been defined. These ichnoguilds show a preferential palaeoenvironmental distribution following proximal-distal trends. Modern tidal flats are characterised by an abundant food supply derived from multiple sources, including nutrients brought in by the sea, terrestrially derived organic detritus and autochthonous food productian (e.g. primary production, faecal pellets). The inhabitants of modern intertidal areas are exposed to a double set of predators. During submergence they are preyed on by marine organisms and during emergence they are visited by enemies from the land and air. Contrastingly, the Cambrian intertidal environments functioned as refugia in the absence of continental (i.e. air and land) predators. Despite the physical stress, Cambrian tidal flats must have been protected areas where abundant food was available at almost no risk. Due to the paucity of land vegetation (and land-derived detritus), Cambrian intertidal trophic webs were almost entirely based on the organically rich marine source and most likely a significant autochthonous production. Although the picture that emerges from the Cambrian is qualitatively different, Cambrian tidal flats may have resembled modern ones in their ecological role as sites of reproductian and protection. The depth and extent of bioturbation reveal colonisation of a relatively deep in faunal ecospace by coelomate metazoans. Arthropod incursions in Cambrian tidal flats support an early colonisation of intertidal environments and indicate that representatives of the Cambrian evolutionary fauna were able to colonise very shallow-water environments, thus suggesting a significant landward expansion of the Cambrian explosion and the "Agronomic Revolution".
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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 it