A Possible Upper Eocene-Oligocene Impact Spherule Layer in the North Alpine Foreland Basin, Upper Bavaria, Germany?
Bibliographic record
Abstract
Introduction: Layers of distal impact ejecta have been reported from various sites on Earth through geologic time [1]. Two ejecta layers are known from Late Eocene-Oligocene sections: first, the so-called clinopyroxene microkrystite layer that is derived from the ~100 km and 35.7 ± 0.2 Ma Popigai crater, Russia; second, the slightly younger North American mircotektite layer linked to the ~90 km and 35.5 ± 0.3 Ma Chesapeake Bay crater, Virginia, USA [1-3]. No spherule layers associated with the smaller impact structures of Lake Mistastin (Labrador, Canada; 28 km and 36.4 ± 4 Ma) and Lake Wanapitei (Ontario, Canada; 8 km and 37.2 ± 1.2 Ma) have been described. Apart from the Massignano stratotype section for the Eocene/Oligocene boundary, Marche, Italy, which is known to contain altered spherules of the clinopyroxene (Popigai) layer [4], no EoceneOligocene impact ejecta are known in Europe. Here we report a possible spherule layer in uppermost Eocene to Oligocene sediments of the North Alpine Foreland Basin of Upper Bavaria (Southern Germany). Samples, Geological Setting, and Methods: Samples were obtained from two Upper Eocene to Oligocene sedimentary sections: first, a natural outcrop of parautochthonous, medium-grained marine sandstones at the Katzenlochgraben near the village of Hammer (within a sedimentary suite regionally known as the “Katzenlochschichten” [5]); second, from the top of red algae-bearig biohermal limestones (regionally known as the “Lithothamnienkalke” [6]) that outcrop in the active cement quarry at Rohrdorf operated by the Rohrdorfer Zement TM enterprise. Both sample locations are ~40 km apart (Fig. 1). Preliminary petrographic and geochemical studies were carried out using optical microscopy (magnifiers and polarization microscopes) and SEM-EDX (energy dispersive X-ray analysis).
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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 | 0.001 | 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) | 0.003 | 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".