Sediment transport and deglacial incision of the upper Mississippi River inferred from luminescence dating
Bibliographic record
Abstract
As rivers sculpt their valleys and floodplains, they transport sediments – primarily quartz and feldspar – from source regions to the sea. These complex sediment-transport processes, difficult to study even over short time scales, can eventually build systems of river terraces, which in turn can record the impacts of past climate on Earth-surface systems. To study both sediment-transport and landform-building processes, we focus on the deglacial fluvial record stored in the upper Mississippi valley.We collected terrace sediment samples for luminescence dating along a 1000 km long section of the upper Mississippi River. The two minerals most commonly targeted for optically stimulated luminescence dating, quartz and feldspar, show different responses to sunlight bleaching, with quartz resetting much faster than feldspar. Furthermore, different grain sizes in fluvial deposits would have likely been transported at different water depths, likely resulting in varying sunlight exposure. However, the latter has not yet been fully explored. We combine luminescence measurement results from two grain sizes for quartz (fine silt and fine to medium sand) on the multi-grain aliquot level with single grain luminescence measurements of sand-sized feldspar to inform on bleaching processes during sediment transport and refine the age of late Pleistocene Mississippi River incision.We combine our two-mineral-luminescence approach with 14C ages obtained from organic matter and a new cosmogenic 10Be profile within Savanna Terrace fill. Based on 14C and luminescence ages, aggradation continued until ~23–17 ka. Following this, the Mississippi River incised below the Savanna Terrace tread ~14–12 ka, corresponding to outburst floods from Lakes Agassiz and Superior, with timing provided by luminescence ages and the 10Be profile. The pattern of bleaching with distance downstream suggests spatially variable dominant sediment sources.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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".