Characterizing the transient geomorphic response to base‐level fall in the northeastern Tibetan Plateau
Bibliographic record
Abstract
Abstract Analysis of hillslope gradient, landscape relief, and channel steepness in the Daxia River basin provides evidence of a transient geomorphic response to base‐level fall on the northeastern Tibetan Plateau. Low‐gradient channels and gentle hillslopes of the upper watershed are separated from a steeper, high‐relief landscape by a series of convex knickzones along channel longitudinal profiles. Downstream projection of the “relict” portions of the profiles implies ~800–850 m of incision, consistent with geologic and geomorphic records of post ~1.7 Ma incision in the lower watershed. We combine optically stimulated luminescence dating of fluvial terrace deposits to constrain incision rates downstream of knickpoints with catchment‐averaged 10Be concentrations in modern sediment to estimate erosion rates in tributary basins both above and below knickpoints. Both sources of data imply landscape lowering rates of ~300 m Ma−1 below the knickpoint and ~50–100 m Ma−1 above. Field measurements of channel width (n = 48) and calculations of bankfull discharge (n = 9) allow determination of scaling relations among channel hydraulic geometry, discharge, and contributing area that we employ to estimate the patterns of basal shear stress, unit stream power, and bed load transport rate throughout the channel network. Our results imply a clear downstream increase of incision potential; this result would appear to be consistent with a detachment‐limited response to imposed base‐level fall, in which steepening of channels drives an increase in erosion rates. In contrast, however, we do not observe apparent narrowing of channels across the transition from slowly eroding to rapidly eroding portions of the watershed. Rather, the present‐day channel morphology as well as its scaling of hydraulic geometry imply that the river is primarily adjusted to transport its sediment load and suggest that channel morphology may not always reflect the presence of knickpoints and differences in landscape relief.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".