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Abstract:
Different mechanisms of crustal shortening act in the foreland of the central Andes in northern Argentina and southern Bolivia, resulting in two distinct deformation styles. The foreland of the Altiplano Plateau is characterised by a thin-skinned tectonic deformation style, involving deformation and accommodation of shortening within the sediments. In contrast, the style of deformation in the foreland of the Puna Plateau is dominated by thick-skinned tectonics where shortening is accommodated by uplift of crystalline basement blocks. Results from thermomechanical modelling indicated that variations in temperature and strength of the crystalline crust may be responsible for these distinct styles. The lithosphere of the Altiplano foreland is thought to be cold and strong, forcing deformation to be concentrated in
the weak sedimentary layer. In contrast, the Puna foreland should be characterised by warm lithosphere and a strong crystalline crust, facilitating the uplift of the basement blocks. We aim to test this hypothesis by means of data-driven 3D lithospheric-scale modelling. Therefore, we integrated data on the main density interfaces within the lithosphere into a consistent model and validated this model using the observed Bouguer gravity field. The input data contain sediment isopachs, Moho-depths from receiver functions and tomographic inversion, as well as mantle density variations that we obtained from the conversion of shear wave velocities from a regional tomographic model. The final density model was used to assess the 3D steady state conductive thermal field, which finally allowed us for the quantification of lithospheric strength.
