Abstract: The depositional regime of Early Triassic sedimentation in the Bjorne Formation on the eastern margin of the Sverdrup Basin, Ellesmere Island, Nunavut, Canada
Bibliographic record
Abstract
The Bjorne Formation of the Canadian Arctic is a poorly understood, dominantly sandstone unit that occurs in the Sverdrup sedimentary basin in the northern part of the Arctic Islands. The aim of researching this formation is to unravel an important part of Sverdrup Basin evolution. The thickness of the Bjorne Formation nears 2000 m in the depocentres and 1000 m along the margins. The outcrop on Ellesmere Island was deposited on the eastern margin of the basin during three phases in the Early Triassic. Three sandstone members are separated by mudstone members. These mudstones are tongues of the stratigraphically equivalent Blind Fiord Formation in the deep basin that represent basin-wide transgression. The sediment was derived from the east and south of the basin and was sourced mainly from Devonian siliciclastic strata that flanked the basin and extended over the craton. Lithological and sedimentological features were observed and correlated to create facies associations for the lower member. Facies associations help create a depositional model for the entirety of the Bjorne Formation. This enables the understanding of the shifting basinal environment and dominant depositional regime during rapid sedimentation during the Early Triassic. In the lower member, there are hundreds of metres of stacked sandstones with red siltstone interbeds with planar stratification and primary current lineation. Shallow scours and mud rip-up clasts are present with potential antidune deposits. The red siltstone beds have climbing ripples, desiccation cracks, and slight bioturbation. These associations of sedimentary features give an indication of episodic and rapid sedimentation similar to a fluvial environment within the spectrum of braided rivers. There is also a marine association with interbedded sandstone and siltstone with hummocky cross stratification and intensive bioturbation. Deposition took place immediately following the PermianTriassic boundary. Extinction of many vegetational taxa at that boundary could have influenced fluvial styles because vegetation helps stabilize banks. The lack of meandering river deposits in the marine/non-marine transitional zone of the Bjorne Formation in the early Triassic could be in part the result of the extinction event. Petrographic information will be used to formulate a model for burial history by looking at compaction, cementation and
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 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".