Early–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides
Bibliographic record
Abstract
Abstract The late Neoproterozoic–Paleozoic Iapetus Ocean developed between Laurentia, Baltica, Siberia and Gondwana. Its Paleozoic closure history is recorded by volcano-sedimentary successions within the Caledonian orogen of Scandinavia, the British Isles and Newfoundland. We present new lithological, geochemical and geochronological data relevant for the Iapetan closure history from the hitherto poorly known Trollhøtta–Kinna Basin (central Norwegian Caledonides). This basin consists of alternating siliciclastic rocks, mid-ocean ridge basalts (MORBs), and felsic volcanic rocks highly enriched in, for example, Th, U and light REEs. Rhyolites from the stratigraphically upper part are dated by zircon U–Pb thermal ionization mass spectrometry to 473.3 ± 1.0 and 472.4 ± 0.7 Ma. Detrital zircon spectra indicate deposition after c. 480 Ma, with sediments derived from composite Cambro-Ordovician and Archean–Neoproterozoic landmass(es), possibly the Laurentian margin or a related microcontinent. The peculiar bimodal volcanic association is interpreted as an intermittent phase of marginal basin rifting, derived from a heterogeneous mantle source previously metasomatized by continental material. The tectonic mechanisms behind rifting could be slab retreat and/or break-off, or far-field tectonic forces within the Iapetan realm. Comparison of this basin with other Iapetus-related, similarly-aged volcano-sedimentary successions along the Caledonian–Appalachian orogen indicate that the bimodal MORBs and highly enriched rocks reflect a palaeotectonic setting hitherto unknown in the orogen.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".