Late Quaternary deglaciation pattern of Lancaster Sound and Barrow Strait traced by radiogenic isotope records in marine sediments
Bibliographic record
Abstract
The retreat of the Laurentide and Innuitian Ice Sheets in the Canadian Arctic Archipelago (CAA) during the late Quaternary led to the opening of Arctic gateways and the inflow of low salinity Arctic waters into Baffin Bay. Studies on marine sediments focusing on the timing and deglaciation pattern of Canadian Archipelago straits mainly concentrated on the Holocene. Here we present two marine radiogenic isotope records from the mouth of Lancaster Sound (GeoB22336-4) and from Barrow Strait (PS72/287) that cover the last ~14.5 ka BP, thus encompass the earlier deglaciation stage. The radiogenic isotope composition (Nd, Sr, Pb) of the detrital sediment fraction serves as provenance tracer and provides information on changing position of the ice margin and oceanographic conditions. Data from both sediment cores show contributions from highly variable source areas during deglaciation in response to the dynamics of the glacier termini involved. However, a strong influence of detrital carbonates, likely eroded from carbonate outcrops of the CAA and northern Baffin Island, by retreating ice, constitutes a dominant feature. Later, the post-glacial deposits recorded more uniform radiogenic isotope signatures until the mid/late Holocene transition, indicating relatively stable environmental conditions. In addition to local sources, isotope compositions in Lancaster Sound illustrate an increasing influence of sediments from Barrow Strait and thus the setting of oceanographic conditions enabling sediment transport from the central CAA towards the NW Baffin Bay. According to these observations and based on a preliminary age model, complete deglaciation with subsequent flushing of major channels is assumed to have occurred at approximately 10 ka BP. During the late Holocene, slightly changing Sr, Pb, and Nd isotope signatures in both cores probably indicate renewed regional ice advances in response to the neoglacial cooling.
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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 | 0.001 | 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".