Origin and paleoenvironmental significance of Fe Mn nodules in the Holocene perialpine sediments of Geneva Basin, western Switzerland
Why this work is in the frame
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Bibliographic record
Abstract
Perialpine areas of central Europe have undergone significant changes following the last Alpine glaciation and especially through the Holocene time. This study relies on geochronological, mineralogical and geochemical clues to explain the formation and paleoenvironmental significance of FeMn nodules reported from the young soils (~4.5 ka BCE) of Geneva Basin in western Switzerland. Having on average 2 mm in diameter, the nodules usually possess an onion-like and quasi-layered internal architecture defined by selective enrichments in Fe and Mn. Fe-rich mica is largely present in soil matrix and has served as a main source of Fe and Mn. Susceptible to favourable Eh-pH conditions several steps in mica weathering were recognised leading to the formation of nodules – vermiculitization, microcracking, FeMn segregation and re-precipitation. Mineral alterations were boosted by long periods of summer warm climate during Boreal and Atlantic times as suggested by the increasing illite-smectite content and a disappearance of hydroxyl-interlayered clays from analysed colluvium. Moreover, archaeological ages and radiocarbon dating of charcoal yielded coherent FeMn encrustation ages (4.8–4.3 ka BCE and 4.5–4.4 ka BCE, respectively) that coincide with the Holocene temperature maximum (~4 ka BCE) in Central Europe. Terrain morphology that led to better water retention formed earlier than ~8 ka BCE ago, during undefined Late Glacial time, promoting seasonal changes in redox conditions, thus facilitating the mobilization, distribution and re-precipitation of Fe and Mn. Established conditions lasted until Late Neolithic (3.4–2.2 ka BCE) when different agricultural practices changed favourable hydromorphic environment effectively putting an end to further nodule formation.
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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 | 0.001 | 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 | 0.001 |
| 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 it