Northward sediment transport from the late Carboniferous Variscan Mountains: zircon evidence from the Oslo Rift, Norway
Bibliographic record
Abstract
Proto-rift, late Carboniferous fluvial and deltaic sandstones from the Asker Group are locally preserved in the upper Palaeozoic Oslo Rift. High-precision U–Pb ages of single detrital zircon grains from a Moscovian (late Westphalian to early Stephanian) sandstone and overlying tuffaceous sediments, that predated initial basaltic volcanism, have been used to study the provenance of the detritus and to evaluate the tectonic significance of the deposits. We find late Neoproterozoic (of Avalonian affinity), Cambro-Ordovician and early Carboniferous detrital zircons requiring that one of the source regions was located along, or south of, the axis between southern England and northeastern Germany and implying sediment transport from the south, probably as a consequence of uplift during the Asturic compressional phase of the Variscan Orogeny. Other age groups reflect typical Baltic sources, possibly from the Ringkøbing–Fyn High. Detrital zircons (and monazite) from underlying Silurian sandstone (Wenlock–Ludlow) yield Svecofennian to Sveconorwegian as well as late Ordovician ages but lack late Neopoterozoic (Avalonian) ages. It is thus unlikely that the bulk of the Carboniferous detritus could have been derived by recycling of preexisting Silurian sandstones. These data imply that the rivers feeding the Asker Group originated in the Variscan mountains and entered the Oslo proto-rift from the south, possibly via the Horn Graben or along the Sorgenfrei–Tornquist Zone.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 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 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".