Lithosphere Removal in the Sierra Nevada de Santa Marta, Colombia
Bibliographic record
Abstract
The Sierra Nevada de Santa Marta (SNSM) in northwestern Colombia is one of the world’s highest coastal mountains, with an elevation above 5.7 km. Gravity measurements show that the SNSM has a high Bouguer anomaly (>+130 mGal), indicating that the mountain lacks a crustal root. In this work, we test the hypothesis that these observa- tions can be explained by gravitational removal of the dense lower lithosphere. We use 2D numerical models to examine the dynamics of lithosphere removal and its effect on surface elevation, gravity and heat flow. The models consist of continental lithosphere that includes a pre-thickened crustal region, representing the SNSM. In our preferred model, the dense mantle lithosphere instability and crustal root are gravitationally unstable and undergo removal as local drips within ∼10 Ma from the onset of foundering. This cre- ates an area of thinned crust (∼38 km) underlain by a buoyant sublithospheric mantle where melting and low seismic velocities are predicted. Subsequent non-isostatic forces maintain a topography of 3.3 km with a Bouguer gravity anomaly of +103 mGal. Pa- rameter tests show that a strong lower-crustal rheology provides greater support for the high topography and that a weak mantle lithosphere rheology produces faster removal. The models demonstrate that local lithosphere dynamics can explain the first-order ob- servations in the SNSM. We propose that lithosphere removal could have occurred at 40- 50 Ma, possibly inducing anomalous short-lived Eocene magmatism, or more recently (∼2 Ma), explaining the localized low seismic velocity zone below the SNSM.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".