U–Pb and Hf isotopic data from Franklinian Basin strata: insights into the nature of Crockerland and the timing of accretion, Canadian Arctic Islands
Bibliographic record
Abstract
New detrital zircon uranium–lead (U–Pb) ages and initial epsilon hafnium (εHf(i)) data from the Devonian clastic succession of the Canadian Arctic Islands refines the provenance of strata within the Franklinian Basin and provides constraints on the geologic evolution of the landmass responsible for the Ellesmerian Orogen. This study contributes more than 500 U–Pb ages and 32 εHf(i) values from the Blackley Formation and the Parry Islands Formation. The Middle Devonian Blackley Formation represents the onset of clastic sedimentation into the Franklinian Basin during the Devonian period. Detrital zircon from two samples yield U–Pb age populations of 380–470, 500–700, 900–2100, and 2550–3000 Ma. The population of 500–700 Ma U–Pb ages indicates a source exotic to the northern Laurentian margin and is attributed to a continental landmass located north of the present Canadian Arctic Islands (often referred to as Crockerland). This is some of the earliest evidence of 500–700 Ma detrital zircon deposition onto the northern Laurentian margin and indicates this northern landmass is at least partially accreted to Laurentia by early-Eifelian time. The Late Devonian Parry Islands Formation is the uppermost succession of Ellesmerian Orogen foreland basin sedimentation in the Franklinian Basin. Detrital zircon from four samples yield U–Pb age populations of 370–450, 470–750, 930–2100, and 2300–3200 Ma. The U–Pb ages suggest the Parry Islands Formation is derived from the northern source terrane (Crockerland) and indicate this landmass contains rocks similar to that of the east Greenland Caledonides, Pearya, and northeastern Baltica. Rim and core U–Pb double dates from the 500–700 Ma detrital zircon population and εHf(i) values from the 380–450, 520–550, and 650–710 Ma detrital zircon populations help constrain magma generation processes within Crockerland and suggest the zircons are derived from a juvenile lithosphere.
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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) | 0.001 | 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".