Impact of Maturation on the Validity of Paleoenvironmental Indicators: Implication for Discrimination of Oil Genetic Types in Lacustrine Shale Systems
Bibliographic record
Abstract
Organic geochemistry analyses were carried out on twenty-two shale samples from the Eocene Shahejie (E s ) Formation in two wells at the Dongying Depression, East China, aiming to investigate the evolution of the gammacerane index (GI) and oleanane index (OI) and the impact of maturation on the validity of these paleoenvironment indicators. While high GI and OI ratio values in some samples do indicate the occurrence of a hypersaline interval and higher contribution of a terrigenous organic matter input, respectively, a positive correlation between both molecular markers and known maturity level suggests dual controls from the source and maturation. A component concentration profile in a maturation sequence offers mechanism interpretation for effectiveness of these commonly used molecular parameters. The invalidity as geochemical diagnosis for paleoenvironment indicators in some highly mature samples is attributed to faster depletion of C 30 17α(H), 21β(H)-hopane against gammacerane and oleanane in the main oil generation window when the vitrinite reflectance value reaches about 0.7%. The present study sheds light on potential risks for discrimination of oil genetic types by those indicators in the complex orogenic region. Hence, with limited validity of these indicators in high maturity regime, caution must be taken while conducting geochemical interpretation on source rocks and crude oils.
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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 | 0.001 | 0.001 |
| 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".