Figure 3

Overall view of model 1 (total erosion; half upper plate advance) after 6 Myr modelling time. (a–e) Second invariant of strain rate shown in 3D view (panels “a” and “b”), vertical cross-sections parallel to the X-axis (panels “c” and “d”), and plan view (panel “e”). (f) Top view of rock uplift rates at the surface. Panels “b” to “e” combine the strain rates with the motion streamlines. Panel “b” denotes the part of the model domain characterized by high strain rates (> 5·10⁻¹⁵ s⁻¹), with colors corresponding to material layers as in Fig. 2. In panels “c” and “d”, the pro- and retro- shear zones are marked with “P” and “R” (solid pink lines in panel “c”) and “p” and “r” (dashed pink lines in panel “d”) for structures on lithospheric and crustal scales, respectively. The shallow retro-decollement is labelled by “D” (solid pink line in panel “d”). The shadowy continuations of the lithospheric-scale (pro- and retro-) shear zones into the central part of the model are interpreted by dashed pink lines in panel “d”. The positions of the vertical cross-sections shown in panels “c” and “d” are indicated by the black lines in panel “f”. The map view in panel “e” corresponds to strain rates at 5 km depth, while the particle trajectories (streamlines) shown there originate at 10 and 30 km depth. In the vertical cross-sections, the corresponding relatively shallow motion streamlines show exhumation of upper and lower crustal material, that increases from both sides towards the model center and accelerates dramatically at the main shear zones (panels “c” and “d”). In the horizontal plane, these flow lines generally demonstrate a nearly parallel influx of material, while in the front portion of the model they pass around the indenter, deflecting slightly in the negative Y-direction (panel “e”).