Holocene carbonate precipitates on precambrian bedrock in the high arctic: age and potential for palaeoclimatic information
Bibliographic record
Abstract
. Crusts of white carbonate precipitate occur commonly on the upper surfaces of glacially sculptured Precambrian granites and gneisses in east‐central Ellesmere Island. Radiocarbon dating of 21 such carbonate precipitates, from elevations between 50 m and 1050 m a.s.l., has yielded only Holocene ages. Two samples from Ellesmere Island, plus one from Inglefield Land, Greenland, have calibrated ages over 5000 years, the rest are younger. The formation of these deposits, mainly calcite and characterized by unusually heavy δ13C ratios (+3.36 to +15.18‰), has apparently been aided in some cases by the presence of bacteria, and some crusts seem to have developed where Ca‐bearing minerals are more prevalent. In the case of Bache Peninsula and Cape Herschel, where the carbonate crusts are particularly abundant, the presence of calcareous till may have played a role as well. The carbonate crusts may be related to the presence of small, thin carapace ice caps, when such features formed at lower elevations than those at which they exist today. The more extensive cover of ice and snow is postulated to have existed during the latter, cooler part of the Holocene, especially during the period from 2500 to 100 years ago, deduced as a period of low melt from ice core studies on the Agassiz Ice Cap, 200 km to the north. The existence of carapace ice caps at lower elevations also agrees with the radiocarbon evidence for outlet glacier advances during the last 2000 years on both east and west margins of the Prince of Wales Icefield. Alternatively, the white carbonate crusts may be, to a large degree, the result of weathering processes. In either case they provide minimum ages for the exposed, ice‐sculptured rock surfaces on which they occur.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".