On the origin of molecular compositions in the Proterozoic extractable organic matter from the Jixian section, Northern China
Bibliographic record
Abstract
Mesoproterozoic shales of low metamorphic grade from the Jixian section, northern China, were geochemically analyzed for bulk organic contents, molecular and isotopic compositions.One organic-rich sample from the Hongshuizhuang Formation is characterized by high total organic carbon and extractable organic material contents, high hydrocarbon generation potential, while four other organic-lean samples have almost no hydrocarbon generation potentials.Molecular compositions differ greatly between the organic-rich and lean samples.n-Alkanes in the organic-rich sample consist mainly of low molecular weight components with a maximum at n-C 12 , while the organic-lean samples are enriched in medium molecular weight n-alkanes with the maximum around n-C 16 .The monomethylalkanes and cyclic alkanes in the organicrich sample are much more abundant than in the organic-lean counterparts, while acyclic isoprenoid alkanes are enriched in the organic-lean samples.Almost no steranes can be detected in the organic-rich sample, while a reasonable amount of steranes, dominated by pregnanes, occurs in the organic-lean samples.Bicyclic sesquiterpanes and pentacyclic terpanes are relatively concentrated in the organic-rich sample, while tricyclic terpanes are the major terpane compounds identified from the organic-lean samples.Alkylphenanthrenes are the major compound class in the aromatic hydrocarbon fractions.The ratios of parent to methylated aromatic homologues are higher in the organic-rich sample than in the organic-lean samples.All these provide convincing evidence for the existence of cyanobacteria organisms in the organic-rich Hongshuizhuang Formation.While both prokaryotes and eukaryotic organisms are likely contributors in the organic-lean samples, contamination from the Phanerozoic biomass cannot be ruled out.
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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 | 0.003 | 0.002 |
| 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) | 0.001 | 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".