Viscoelastic folding: Maxwell versus Kelvin rheology

Folding of a viscoelastic layer embedded in a viscous matrix is studied ana lytically using two viscoelastic theological models: The Maxi-veil and the Kelvin model. The layer deformation behaviour approximates the viscous or e lastic limits depending on the single parameter, R, which is proportional t o the viscosity contrast and the ratio of layer-parallel stress to shear mo dulus. A layer with Maxwell theology approximates this limit that generates the fastest amplification whereas a layer with Kelvin theology approximate s the slowest limit. For R < 1 the viscous limit is fastest whereas for R > 1 the elastic limit is fastest. The Kelvin theology is suitable to describ e the effective flexural response of a lithospheric plate consisting of an elastic layer overlying a viscous layer, since the Kelvin rheology yields a n identical bending moment. A critical elastic layer thickness, (RH)-H-2/3 (H = lithospheric thickness), is derived at which the deformation behaviour of the lithospheric plate changes from quasi-viscous to quasi-elastic.