Mechanics and erosion of basement‐cored uplift provinces

Abstract

Basement‐cored uplift provinces are often characterized by high‐angle reverse faulting along preexisting crustal heterogeneities, which may greatly affect the mechanics of deformation and the coupling between erosion and orogenic structure. Herein we construct a coupled deformation‐erosion model to understand the mechanics and erosion of mountain belts in which the spatial distribution of deformation is largely influenced by the presence of preexisting high‐angle faults. In this case, deformation is accommodated along, and topography is built above, these structures. This topographic loading leads to increasing lithostatic stresses beneath these regions. As a result, active deformation may migrate to frictionally stronger structures in adjacent regions where lithostatic loading is lower. The migration of deformation to such nearby structures depends on the Hubbert‐Rubey pore fluid pressure ratio of the crust (λ), the orientations of the frictionally weaker and stronger preexisting faults (β1 and β2, respectively), the friction coefficients (μb1 and μb2) and Hubbert‐Rubey fluid‐pressure ratios (λb1 and λb2) of these faults, and the surface slope of the topography above the frictionally weaker structure (α), assuming zero surface slope above the frictionally stronger structure. In general, we found that for a given α and β1, as μb1 increases λ = λb1 = λb2 increases, and β2 decreases, the value of μb2 required to force deformation to migrate increases. However, as erosional processes lead to decreasing surface slopes, deformation will be inhibited from migrating to frictionally stronger structures in adjacent regions. Our model results may help to explain some aspects of the deformation observed and the possible correlation between precipitation and the migration of deformation within these tectonic provinces.