CAMBRIAN CHRONOSTRATIGAPHIC UNITS IN NORTH AMERICA
Bibliographic record
Abstract
GSSPs of Cambrian chronostratigraphic units have focused on “FADs” (best termed LOs, Lowest Occurrences). The system’s top and bottom GSSPs are defined in North America (NAm). LOs of the eurytopic trace T. pedum are in the basal Cambrian transition globally. A GSSP modification (Landing et al., 2013) at disappearance of large Ediacaran taxa in the lower T. pedum range in Avalonian Newfoundland maintains the GSSP. The Ordovician GSSP (conodont Iapetognathus fluctivagus LO, W Newfoundland) is appropriate; a report that the form was not later recovered at the GSSP is at odds with early thorough documentation. This GSSP is somewhat “irrelevant;” the Ordovician base across most of Laurentia is an unconformity that truncates the C–O boundary interval. Subdivision of the Terreneuvian Series includes a proposed Stage 2 base at the rostroconch? Watsonella crosbyi LO in the I’ Excursion that is appropriate in Avalonian NAm (Laolingian Stage of Landing et al., 2013). Defining the Series 2 (Lenaldanian of Landing et al., 2013) and Stage 3 base at the “FAD of trilobites” is inappropriate: the group appeared 5+ m.y. earlier and has a globally diachronous LO. A Series 2 GSSP at onset of a d13C excursion (IV) in the lower range of Siberian trilobites brings the oldest Laurentian trilobites (California–Nevada) into Series 2. Little progress exists on a Series 2, Stage 4, GSSP, but assigning NAm Laurentian & Avalonian Calodiscus-Triangulaspis assemblages to Stage 4 is appropriate. High provinciality and definition in dysoxic facies mean imprecise correlation of higher Cambrian GSSPs into the Laurentian platform. The inadequate Wuliuan Stage GSSP, based on LO of distorted, facies-controlled (dysoxic) I. indicus in a chaotic (slumped) succession correlates above the Laurentian highest Olenellus Zone s.l. The basal Drumian (GSSP in Utah) and Guzhangian stages are best recognized in marginal (west) Laurentian successions. Correlation of the Paibian Stage into Laurentia is assisted by SPICE, and lower Jiangshanian Stage correlation into the Elvinia Z. is suggested by I. angustifolius. The Stage 10 GSSP alternatives are the LO of a dysoxic agnostoid with problematical taxonomy (“L. americanus”) and is unknown in Laurentia vs proposal of the LO of the eurytopic conodont E. notchpeakensis below the HERB Excursion onset (Landing et al., 2010).
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.004 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
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".