Constraining mantle density structure using geological evidence of surface uplift rates: The case of the African Superplume
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
We explore the hypothesis that southern Africa is actively being uplifted by a large‐scale, positively buoyant structure within the mid‐lower mantle. Using a new formulation in which dynamic topography and uplift rate are jointly used, we place constraints on mantle density and viscosity. The solution of the momentum equation is coupled with the advection of the density field to solve for the surface uplift rate in both an axisymmetric and fully spherical geometry. We demonstrate how dynamic topography and its rate of change depend on density and lateral and radial variations in viscosity. In the full spherical models the geometry of mantle density is derived by scaling a tomographic shear velocity model. Using a variety of geologic observations, we estimate residual topography (i.e., the topography remaining after shallow sources of density are removed) and an average Cenozoic uplift rate to be 300–600 m and 5–30 m/Myr, respectively, for southern Africa. We are able to satisfy these constraints with a mantle model in which the mid‐lower mantle beneath southern Africa is 0.2% less dense and has a viscosity of ∼ 10 22 Pa s. In addition, if the continental lithosphere is thick beneath southern Africa, as suspected from seismic inversions, and has a high effective viscosity, then we find that southern Africa can be further elevated owing to increased coupling between the deep mantle and surface. We show that recent estimates of mantle density, suggesting that the lowest parts of the African anomaly may be anomalously dense are compatible with geologic constraints. We conclude that uplift rate, when combined with estimates of present‐day dynamic topography, provides a powerful tool to constrain the properties of the deep mantle.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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 it