Seismic Imaging of Heterogeneous Lithosphere Beneath the Unusually Broad Turkana Depression, East Africa
Bibliographic record
Abstract
Continental rifting is currently active in East Africa, where breakup of the African continent is generally occurring in relatively focused rift zones within two uplifted plateaus, with magma intrusions the primary mechanism for strain accommodation throughout the crust and mantle lithosphere. Linking the two narrow rift valleys is the low-lying, and as-yet poorly studied Turkana Depression - an unusually broad 300km-wide region of diffuse faulting, seismicity and magmatism. How the East African Rift has developed here remains elusive and is complicated by the fact the Depression was variably stretched by several superposed episodes of failed rifting since the Mesozoic. Utilising data from the NSF-NERC-funded TRAILS seismic network, we produce the first detailed crustal and uppermost-mantle shear-wave velocity model below the Turkana Depression, illuminating Moho and lithosphere-asthenosphere boundary topography that ultimately shed light on rift development in a multiply-rifted region. We find Turkana’s lithosphere is relatively melt-poor, unlike the Ethiopian rift and Plateau further north, which have undergone extensive lithospheric modification by voluminous Cenozoic flood-basalt magmatism and magma-assisted rifting. The lower crust below rift zones in Turkana is not associated with markedly slow (melt) or fast (cooled gabbroic intrusions) wavespeeds suggesting magmatic extension has not dominated rift development in Turkana. Throughout the Depression, the thinnest crust resides within failed Mesozoic rift zones which the present-day East African Rift appears to circumnavigate, not exploit. Fast uppermost mantle wavespeeds below the thinnest crustal regions indicate post-Mesozoic rifting, re-equilibrated and possibly melt-depleted mantle lithosphere, which now renders the plate stronger and more refractory than regions not previously rifted. Refractory Proterozoic lithosphere also present in southern Ethiopia may have influenced strain localisation and the broad, complex rift zone between Ethiopia and Kenya.
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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 | 0.001 | 0.001 |
| 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".