Bibliographic record
Abstract
Marine muds deposited on the French Guiana coast mostly originate in the Amazon. Recent sediments are composed of (a) illite (33 %) and chlorite (13 %) of Andean mountain origin; and (b) kaolinite (28 %) and smectite (26 %), principally from the Amazonian lowlands but also from the Guiana Shield. In the coastal mud prism, high-resolution seismic profiles, together with sedimentological, micropaleontological and soil engineering studies, supplemented by C-14 dates, permitted a stratigraphic interpretation of eight cores. Three episodes have been determined on the basis of clay-mineral variations related to Amazonian lowland, Andean and Guiana shield sources. The older episodes 3 (3000-1700 y BP) and 2 (1700-1000 y BP) are predominantly characterized by lowland-derived clays (smectite = 43 %, kaolinite = 26 %) from Amazonian and local sources. The most important event is a reduction of the Andean source, due to successive dry phases which occurred in western Amazonia about 2200 and 1200 y BP, confirming that regional decreases in rainfall, water discharge and erosion were associated with climatic fluctuations. It is suggested that these dry phases (within the last 3000 years) are the consequence of several protracted (10-100 years) periods, during which atmospheric conditions mimicked the present-day ''El Nino Southern Oscillation'' (ENSO) phenomenon. As a result, particulate flux from the ocean decreased, leading to reduced silting of the Guiana coast, In the past 1000 years (episode 1), illite and chlorite have increased, indicating a stronger Andean contribution to the Amazonian continental flux that reaches the ocean. This is the first demonstration that the nature of the coastal marine muds of northern South America reflects climatic changes in the Amazon basin.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.004 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.003 |
| Bibliometrics | 0.004 | 0.003 |
| Science and technology studies | 0.002 | 0.003 |
| Scholarly communication | 0.005 | 0.008 |
| Open science | 0.006 | 0.005 |
| Research integrity | 0.009 | 0.003 |
| Insufficient payload (model declined to judge) | 0.993 | 0.995 |
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; the direct Gemma label and the distilled Codex classifier agree on what is shown here.
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".