Holocene palaeoenvironmental reconstruction in norteastern Brazi inferred from polen,, charcoal and carboon isotope records
Bibliographic record
Abstract
Soils in the Barreirinhas region, Maranhao State, were sampled for 613 C analysis and buried charcoal fragments in the soils were radiocarbon dated. Three soil profiles collected in forested areas around the Lagoa do Caqö and one in a woody savanna (mixture of non-arboreal and arboreal species) located approximately 10 km southeast of the Lagoa were studied. A high-resolution pollen record was obtained from lake sediments, showing that forest vegetation was predominant in the area in the early Holocene. From approximately 10 000 14C yr BP the pollen spectrum gradually changed, suggesting the dominance of open savanna communities, these were transformed to a more forested landscape (woody savanna) from approximately 7500 yr BP. The lake sediments also record evidence of fire (indicated by buried charcoal particles at several soil depths) during the Holocene. The 613 C analysis of soil organic matter (SOM) indicates that from between approximately IO0000 yr BP and 9000 yr BP to -4000 yr BP, a woody savanna prevailed at two sites around the lake, probably reflecting a drier climate. From -4000-3000 yr BP to the present, the results indicate a moderate and progressive increase in arboreal vegetation around the lake as a result of the return to more humid climate conditions probably similar to the present-day. The carbon isotope results from the site located 10 km from the lake indicate the presence of an open vegetation from the early Holocene. In general, there is agreernent between the palaeovegetation patterns inferred from the pollen and carbon isotope data. However, a much less uniform landscape, with a mosaic of different ecosystems at any given time, is inferred from the carbon isotope record.
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How this classification was reachedexpand
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) | 0.002 | 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 teacher head, 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".