Pollen and macrofossil‐inferred palaeoclimate at the Ridge Site, Hudson Bay Lowlands, Canada: evidence for a dry climate and significant recession of the Laurentide Ice Sheet during Marine Isotope Stage 3
Bibliographic record
Abstract
We examine pollen, macrofossils and sedimentological proxies from the Ridge Site, an 18‐m sequence of glacial and non‐glacial sediments exposed along the bank of the Ridge River in the southern Hudson Bay Lowlands (HBL), Canada. As the HBL is located in the previously glaciated region of North America, palaeorecords from this region have important implications for understanding ice‐sheet palaeogeography and climate for the late Pleistocene. Two diamicton units were interpreted as subglacial till deposited by a glacier flowing toward the south‐southwest (lower diamicton) and west‐southwest (upper diamicton), respectively. Confined between these tills is a 6‐m non‐glacial unit, constrained to Marine Isotope Stage 3 (MIS 3; c. 57 000 to c. 29 000 a BP) by three radiocarbon dates. Quantitative analyses of the pollen record (dominated by Sphagnum, Cyperaceae, Pinus, Picea, Salix, Alnus and Betula) suggest that average summer temperature (June, July, August) was 14.6±1.51 °C, which is similar to that of the present day at the site. Total annual precipitation was 527±170 mm as compared to 705 mm present‐day. The macrofossil record confirmed the local presence of Betula, Salix and conifers. Our results, in combination with other records from the periphery of the Laurentide Ice Sheet, suggest that vast boreal forest‐type vegetation, along with a drier interstadial climate, existed in the region during MIS 3. We also compare pollen‐derived palaeoclimate reconstructions from the Ridge Site with reconstructions from a previously published site along the Nottaway River, HBL, which was dated to MIS 5a–d (c. 109 000 to c. 82 000 a BP). This comparison suggests that, with additional data, it may be possible to differentiate MIS 3 and MIS 5 deposits in the HBL on the basis of relative continentality, with MIS 3 characterized by lower total annual precipitation, and MIS 5 by values similar or greater than present‐day.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".