Quaternary exhumation history of the NE Tibetan Plateau revealed by peculiar distributions of polycyclic aromatic hydrocarbons in core extracts from the Sanhu depression, eastern Qaidam basin
Bibliographic record
Abstract
ABSTRACT Reworked organic matter (ROM) has been frequently encountered in fresh organic matter (FOM) in young sedimentary basins. Our study reports an ROM‐dominated sequence from 21 borehole cores of the Late Pliocene–Quaternary strata in the Sanhu depression of the eastern Qaidam basin in northwestern China. Reworked organic matter occurrence is confirmed by Rock‐Eval pyrolysis results, high Ro values, and reversed polyaromatic hydrocarbon (PAH) maturity trends showing elevated maturities. Rock–source correlation using molecular fingerprints of biomarkers shows ROM was derived from Jurassic freshwater lacustrine source rocks dominated by terrestrial input, contrasting the immature Quaternary FOM developed in anoxic, saline lacustrine facies. The ROM provenance is traced northward to the southern Qilian Mountains. Maximum burial depths of ROM prior to erosion have been inferred by a burial depth–Rc (calculated vitrinite reflectance) correlation. Two chronological boundaries (1.83 Ma and 3.12 Ma) displaying distinct biomarker fingerprints are obtained from a previously reported chronological framework in the study area. Accordingly, an eroded thickness of 1214 m and an average erosion rate of 94 cm/ka of the ROM provenance areas during this temporal interval are derived. Our study has illustrated the potential value of geochemical compositions of ROM with constrained provenances in investigating the exhumation history of a mountain.
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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 | 0.000 | 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".