Detrital zircon characteristics of the Lower Cretaceous Isachsen Formation, Sverdrup Basin: source constraints from age and Hf isotope data
Bibliographic record
Abstract
Detrital zircons from the Lower Cretaceous Isachsen Formation of the Sverdrup Basin, Canadian Arctic Archipelago, have been dated by the U–Pb method and analyzed for Hf isotopes by laser ablation microprobe – inductively coupled plasma – mass spectrometry (LAM–ICP–MS). Five samples from four locations on Ellesmere and Axel Heiberg islands display similar ranges of U–Pb ages, with significant zircon populations at 2.8–2.6, 1.9–1.8, 1.7–1.6, and 1.2–1.0 Ga. Major hiatuses occur between 2.4 and 2.0 Ga and from 0.96 to 0.5 Ga. Low initial εHfvalues indicating recycled crust components are significant in Palaeoproterozoic (1.9–1.8 Ga) and Neoarchaean (2.8–2.6 Ga) zircon populations. Other U–Pb age populations in the studied samples are dominated by zircon with positive εHfvalues, indicating a significant contribution from mantle-derived protoliths. The εHfvalues seen within a given U–Pb age population are generally consistent, with only minor scatter among the different samples. U–Pb and Hf data closely resemble previously published data from Lower Cretaceous rocks in northern Greenland, suggesting they have the same origin. The data are also largely consistent with the East Greenland Caledonides and the Precambrian basement of Greenland and northern Canada as predominant sources of zircon for the studied sandstones. However, based on the level of similarity between data from the Wandel Sea Basin and Sverdrup Basin sediments and on previous Nd isotope work in the Sverdrup Basin, it is likely that the sediments represent redeposited lower and middle Palaeozoic sediments.
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 | 0.002 | 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".