A New Framework for the Pleistocene Stratigraphy of the Central St. Lawrence Lowland, Southern Québec
Bibliographic record
Abstract
For three decades, a stratigraphic framework involving one glaciation with two major ice advances (represented by the Bécancour Till and Gentilly Till), separated by one brief interstade (represented by the St. Pierre Sediments), has been invoked to explain the lithostratigraphic succession of Pleistocene sediments exposed in the St. Lawrence Lowland of southern Québec. New exposures found along the bluffs of the St. Lawrence River and recent borehole data provide evidence that the Pleistocene depositional sequence is the result of three glacial advances and two nonglacial events, each represented by organic-bearing units. Two lithostratigraphic units (Lotbinière Sand and Lévrard Till) and three climatostratigraphic units (St. Lawrence Stade, Grondines Interstade and Les Becquets Interstade) are introduced in the stratigraphie nomenclature. No definite age can be assigned to the lowermost till (Bécancour?) but it is now believed to be pre-Sangamonian. Field observations and geochronological data suggest the lower and upper interstadial sediments, and an intervening glacial unit represent brief but severe environmental changes that occurred at the beginning of the Wisconsin Glaciation, ca. 90-70 ka BP. This sequence may correlate with marine isotope stage 5a, stage 4, and the earliest part of stage 3. The age of the onset of the last glacial advance (Gentilly Till) is problematic, possibly ranging from 60 to 30 ka BP.
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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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".