Lithological influence on bedrock incision and transience: Insights from the Aparados da Serra Escarpment, southeast Brazil
Bibliographic record
Abstract
Bedrock strength is widely regarded to exert major control over fluvial incision and landscape evolution. Despite that, quantifying lithological effects on natural landscapes has been extremely difficult due to limited continuous exposure at a watershed scale, especially in vegetated environments. Recent numerical models emphasize the pivotal role of rock strength in steering long-term landscape evolution, causing deviations from steady-state conditions, the formation of knickpoints, and biased erosion records. Situated along the southeast coast of Brazil, the Aparados da Serra Escarpment (lat. 28–29°S) represents a prominent geomorphological feature (>1,500 m asl) in the passive margin section of South America. Marked by a sequence of relatively weak sedimentary units overlain by relatively strong volcanic rocks, the escarpment exhibits gradual changes in the strong/weak ratio along its length due to a regional south-dipping contact. The well-constrained stratigraphy (stacked sedimentary and volcanic rocks), climatic conditions (uniform rainfall and temperature), and tectonic setting (regionally uniform and low uplift rates) make this region an ideal laboratory for investigating the influence of rock strength on river profiles. This study conducts a comprehensive series of in-situ rock strength measurements at closely spaced intervals (15 m vertical intervals between each site) along three sections across the escarpment (Rocinha at 28.8°S, Rio do Rastro at 28.4°S, and Corvo Branco at 28.0°S), covering a total escarpment segment > 100 km along strike and providing near-continuous exposure from sea level to 1,500 m asl. To this end, we perform detailed mapping along each section and use a Schmidt hammer type N to record the compressive strength of each lithological unit in the area. In addition, we also record the weathering state and fracture spacing for each site, allowing us to build the first continuous rock strength suite for a major geomorphological feature. Our resulting dataset (> 200 sites with > 30 measurements for each site) allows us to examine a long-postulated but rarely documented relationship between rock strength and bedrock channel steepness. Comparative analysis of normalized river steepness (Ksn) from adjacent watersheds (
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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 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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; both teacher heads agree on what is shown here.
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".