Long-lived topography along rifted margins: Insights from Aparados da Serra escarpment, Southeast Brazil
Bibliographic record
Abstract
The Brazilian margin is one of the longest elevated passive margins (EPMs) in the world. However, both the timing of uplift and the long-term evolution of this EPM remain highly debated. In this study, we present a new suite of apatite (U-Th-Sm)/He (AHe) and fission track (AFT) ages for the southern end of the Brazilian EPM, in the Aparados da Serra plateau. Combined with literature data, our results reveal that mean AHe ages range from 43 to 112 Ma, while AFT ages range from 46 to 222 Ma. Thermal history models suggest monotonic exhumation rates in the Aparados da Serra, with post-rifting rates <50 m Myr−1 in the coastal plain and < 25 m Myr−1 in the volcanic plateau. Collectively, our results imply a total erosion of 2–4 km of material from the coast and < 2 km from the plateau since rifting ca. 120–100 Ma. AHe and AFT data indicate no detectable accelerated phase of exhumation during the Cenozoic, implying that recent uplift along the margin was either absent or minimal, and that the relief observed in the Aparados da Serra is likely a consequence of sustained rift topography. Based on the absence of major recent tectonic events, we argue that Cenozoic exhumation patterns in the Aparados da Serra were largely controlled by geomorphologic processes (e.g., differential erosion). Lastly, the equivalence between long (AFT and AHe) and short-term (catchment-averaged) erosion rates argues for sustained stability of the margin over geological timescales.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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".