Abstract: Sedimentology, detrital petrology, and regional linkages of the Lower Cretaceous Bjarni Formation, Labrador Shelf
Bibliographic record
Abstract
The Barremian–Early Cenomanian Bjarni Formation on the Labrador Shelf overlies rift-related volcanic rocks of the Alexis Formation or Paleozoic or Precambrian basement. Seismic sections show that it accumulated in tectonically deforming rift basins trending NW-SE. We sedimentologically logged all available conventional core from 9 wells, assessed sediment sources by point counting and bulk geochemistry of sandstones, and examined diagenetic features. Most sediments are lacustrine, fluvial or alluvial fan, or at the top of the formation, marginal marine. Some of the marginal marine facies appear tidal, others show dominance of river flood supply. Sandstones are arkosic, but show differences in petrology and geochemistry from south to north. As in correlative rocks of the Scotian basin, Ti is unusually abundant and Ca particularly low. Sediments appear to have been supplied locally. Diagenetic kaolinite is present in places. Diagenetic siderite is concentrated at abrupt changes in sedimentation rate. In Bjarni O-82, sandstones assigned to the top of the Bjarni Formation are of Turonian–Coniacian age and include tuff beds alternating with silicified shales. The Bjarni Formation is of similar age to the Chaswood Formation of Nova Scotia, which is also a terrestrial unit deposited in syn-tectonic basins. Major offsets in basin trends on the Labrador Shelf are associated with sinistral wrench faults. Sinistral strike-slip faults appear important in localising the Chaswood Formation and were also important in the Lower Cretaceous of Orphan Basin. The sedimentology and diagenesis of the Bjarni Formation is, however, quite different from that of the Chaswood Formation, as a result of the generally continuous subsidence of the Bjarni Formation basins compared with episodic uplift of the Chaswood Formation. The same NE-trending fault trend may be responsible for uplift on the inner Scotian Shelf in the Early Cretaceous.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.004 | 0.001 |
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".