Growth rates for freshwater ferromanganese concretions indicate regional climate change in eastern Canada at the Northgrippian-Meghalayan boundary
Bibliographic record
Abstract
The existence of freshwater ferromanganese concretions has been known for decades, but we are not aware of a generally accepted explanation for their formation, and there has been little research into their potential use as records of Holocene climate and paleohydrology. A conceptual model is presented to describe the environmental and geochemical processes which result in the formation and growth of freshwater ferromanganese concretions. In order to evaluate their potential as historical geochemical records, a concretion from Magaguadavic Lake, New Brunswick, Canada is the focus of a detailed geochronological and geochemical investigation. The radiocarbon data provide a coherent growth curve and a maximum age for the concretion of 8448 ± 43 years, consistent with the establishment of Magaguadavic Lake as a stable post-glacial lacustrine system. The data suggest accretion rates of 1.5 and 3.4 mm per 1000 years during the Northgrippian and Meghalayan stages of the Holocene, respectively. The abrupt change in growth rate observed at the stage boundary may be an indicator of Holocene climate change. These features are consistent with inferences from previous research that warmer climate in the Northgrippian led to eutrophication in some lakes in eastern North America. The results confirm that freshwater Fe-Mn concretions may yield important information about past climatic and environmental conditions.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".