Flat-Slab Bulldozing of Basal Continental Mantle Lithosphere: 2D Numerical Models and Application to the Laramide Orogeny
Bibliographic record
Abstract
Flat-slab (horizontal) subduction occurs along ~10% of subduction margins, forms magmatic gaps, causes upper-plate deformation to migrate inland, and is thought to have caused the Laramide Orogeny. We investigate bulldozing of basal continental mantle lithosphere (CML) by the flat Farallon slab, using 2D numerical thermal-mechanical models. We vary CML density and strength to understand controls on the bulldozing process. Flat-slab subduction begins when an oceanic plateau, which makes the slab buoyant, enters the trench. The dense slab ahead of the plateau detaches and continues to sink, and subduction erosion of the continental margin begins. A slab hinge is quickly re-established at the front of the flat slab. The advancing flat slab erodes (bulldozes) the basal ~25-50 km of continental mantle lithosphere (CML), thinning it. Buoyant (depleted) bulldozed CML can accumulate ahead of the slab hinge, in a growing, migrating wedge up to ~200 km thick, that is wider (up to ~700 km) if bulldozed CML is weak, or narrower if CML is strong. We suggest that bulldozed wedges transmit contact stress into the upper plate, driving crustal deformation ahead of the flat slab itself. Dense bulldozed CML, especially if also strong, is entrained with the sinking slab, so would be imaged with it in seismic tomography. It is probable that bulldozed CML also may accumulate along one or both sides of the contact zone between slab and upper plate. Whether buoyant or dense, bulldozed CML fills the asthenospheric wedge, which would end arc-type melting during flat-slab advance. Flat-slab rollback reopens the asthenospheric wedge, renews melting, and leaves a step and/or a thickened keel in the CML at/ahead of the farthest slab extent.
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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 | 0.001 | 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".