Late Quaternary Sr-Nd-Pb isotope composition of the siliciclastic sediment fraction of the marine sediment core PS72/287-3 from Barrow Strait, Canadian Arctic Archipelago
Bibliographic record
Abstract
The Sr-Nd-Pb isotope composition of siliciclastic sediments from the marine sediment core PS72/287-3 from Barrow Strait was analyzed to identify changing sediment provenances during the last deglaciation and the Holocene. Barrow Strait was blocked by the confluent Laurentide and Innuitian ice sheets during the last glacial period and is hence very interesting to study deglaciation processes in the Canadian Arctic. Varying Sr and Nd isotope ratios during the deglacial period suggest changing sediment sources probably related to ice sheet dynamics and sediment transport processes. After the deglacial period, radiogenic isotope ratios evolved less variable, indicating just slight changes in sediment provenance related to more stable environmental conditions during the Holocene. Sample preparation and radiogenic isotope analysis were conducted in the laboratories of the Isotope Geochemistry Group at MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany. Sediment samples were leached using a NaOH-buffered solution of hydroxylamine hydrochloride and 15% acetic acid in order to separate the siliciclastic sediment fraction (adapted from Gutjahr et al. 2007, https://doi.org/10.1016/j.chemgeo.2007.03.021). Using a Thermo-Fisher Scientific TRITON Plus thermal ionization mass spectrometer (TIMS), the isotope ratios were determined after the elements had been separated by column chemistry.
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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 | 0.004 | 0.004 |
| Science and technology studies | 0.002 | 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".