Reconstructing Quaternary ice sheet erosion and dynamics across Baffin Island, Arctic Canada
Bibliographic record
Abstract
Evidence is poorly preserved in the geologic record for the evolution of Laurentide Ice Sheet (LIS) erosion, dynamics, and basal thermal regime patterns. It has been hypothesized that changes in LIS subglacial conditions and erosional efficiency drove the enigmatic mid-Pleistocene transition (MPT) from 41- to 100-ka climate cyclicity. In this dissertation, a variety of archives and tools are used to explore the 2.7+ Ma history of ice-sheet erosion on Baffin Island in the eastern Canadian Arctic and the possible role of the LIS in the MPT.\nWe compile till geochemistry and cosmogenic radionuclide data to identify a coherent spatial pattern of fresh till and older, more weathered till on the landscape. We interpret the presence of such weathered till to be the result of an expansion in cold-based ice cover prior to 1 Ma, and by that time the fiorded Baffin Island coastline must have developed close to its modern configuration.\nSubglacially precipitated calcite crusts preserved at several sites on the interior plateaux of Baffin Island provide unique insight into LIS erosion during the last glaciation. U-series dating and O, C, and Sr isotope analyses reveal that the majority of erosion during the last glaciation must have occurred prior to 25-15 ka, and the extent of cold-based ice expanded during deglaciation.\nThe Clyde Foreland Formation (CFF) records at least seven Plio-Pleistocene glaciations. Combining amino acid racemization and 10Be-26Al isochron burial dating, we construct the first absolute chronological framework for the CFF. The oldest sediments are Early Pleistocene or latest Pliocene and contain an exceptionally high meteoric 10Be inventory consistent with regolith erosion. Younger tills both pre- and post-dating the MPT contain no detectable geochemical or mineralogical evidence of regolith erosion.\nRegolith was most likely removed from beneath the Foxe Dome of the LIS prior to the MPT, and the subglacial deformation of such sediment was not responsible for any regional changes in ice sheet dynamics related to the MPT. However, changes in the LIS basal thermal regime on Baffin Island occurred coincident with or prior to the MPT and may have contributed to the MPT.
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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 | 0.003 | 0.003 |
| 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) | 0.001 | 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".