Paleoproterozoic tectonics of Fennoscandia and the birth of Baltica
Bibliographic record
Abstract
Baltica, in the core of the supercontinent Nuna, comprises Fennoscandia, Sarmatia and Volgo-Uralia. We develop a tectonic model of Paleoproterozoic Fennoscandia based on stratigraphic correlations of 2.5–2.0 Ga cover sequences and a shield-wide recognition of the main 1.93–1.70 Ga D1–D6 deformation events. Rifting of the combined proto-Karelia–Kola continent is recorded by the 2.51–2.49 Ga Mistassini and ca. 2.44 Ga Matachewan LIP systems, and a 2.35–2.15 Ga post-rift epeiric sea stage. The 2.15–1.95 Ga age period encompasses continental breakup along the western margin of Karelia at 2.10–2.05 Ga, between Kola and Karelia at 2.0 Ga, and the 2.0–1.95 Ga opening of a marginal basin. 2.03–1.92 Ga subduction occurred along the western margin of Volgo-Sarmatia and in Fennoscandia followed by collisional, accretionary and oroclinal deformation events. Fennoscandia–Volgo-Sarmatia collision at 1.93–1.92 Ga provided voluminous 2.03–1.96 Ga clastic detritus that collected on the western margin of the Karelia continent and which was multiply recycled at 1.91–1.82 Ga across Fennoscandia. Orogen-perpendicular NE–SW and the orogen-parallel NW–SE shortening events at 1.93–1.70 Ga can be correlated to Laurentia. Paleomagnetic data indicate post-1.76–1.74 Ga 29° clockwise rotation of Sarmatia relative to Fennoscandia. Rotation caused bending of the WNW–ESE trending accretionary belts of southern Fennoscandia and crustal stretching in central Fennoscandia, finalizing the birth of Baltica at ca. 1.70 Ga. Orogen parallel shortening by orocline formation and block rotations played a major role in producing the present complex internal configuration of Baltica and similar processes likely played a role in the formation of other continents.
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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) | 0.002 | 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".