Strain localization during compression of a laterally heterogeneous lithosphere

Deformation pattern and topography development characterizing mountain building in intra-plate settings as a function of the presence of lateral rheological heterogeneities are studied by lithospheric-scale analogue models. Three layers models characterized by the presence of a “disturbance zone” (DZ) located either in the ductile mantle or in both ductile crust and mantle and striking perpendicular to the compression direction were deformed under normal gravity conditions. Lithospheric thickness, width of the DZ and relative lateral strength contrasts have been the main investigated parameters. Experimental results show that in the absence of a DZ the deformation of a relatively weak lithosphere is characterized by pop-ups and pop-downs in the central part of the model. A small strength contrast at the DZ margins is sufficient to localize deformation. The width of the DZ determines the wavelength of upper crustal deformation. Previous conducted models shows that a stronger strength contrast between converging plates and an intervening weak zone results in a doubly vergent fold and thrust belt flanking the weak zone deformed into a broad slightly asymmetric antiformal structure. Our modelling results provide valuable insight in favourable rheological conditions for the transfer of strain in intra-plate settings and are applicable to natural laboratories.