Origin, age, and paleoenvironmental significance of carbonate precipitates from a granitic environment, Akshayuk Pass, southern Baffin Island, Canada
Bibliographic record
Abstract
This study documents the discovery of calcite crusts on the upper surface of clasts within morainic complexes in Akshayuk Pass, southern Cumberland Peninsula (Baffin Island), a region underlain by granitic and gneissic rocks of the Precambrian Canadian Shield. Strontium isotope ratios (87Sr/86Sr) indicate that the major source of calcium is derived from the local dissolution of fracture-filling calcite and a minor source is derived from silicate weathering. The calcite crusts have δ13C values between 1.6 and 12.0 and δ18O values in the –13.0 and –7.9 range. These values are highly enriched over the predicted isotopic values based on the δ13CDIC and δ18O of the local water and temperature at which calcite precipitation occurred. The isotopic enrichments are attributed to a combination of both equilibrium and kinetic evaporation and were verified experimentally. The series of evaporative experiments indicate that kinetic evaporation produces a far-from-equilibrium isotope effect on both the δ13C and δ18O composition of the precipitating calcite (13CKIE CaCO3–CO2 between 20.2 and 40.5 VPDB; 18OKIE averaging 34.9% ± 3.7% VSMOW). Based on these results, the formation of the calcite crusts is ascribed to the evaporation of stagnating ephemeral lakes and streams following the retreat of valley glaciers. Given the >1500 m difference in heights between the highland and the valley, the katabatic winds originating from the Penny Ice Cap can act as a catalyst to increase the rate of evaporation. In addition, radiocarbon dating of ten of these crusts yielded Holocene ages (7640 cal (calibrated) BP to modern). These results suggest that the maximum expansion of Holocene valley glacier in Akshayuk Pass, previously thought to have occurred during the Little Ice Age, is probably much older.
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 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| 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".