We examine the influence of the migration of chemical constituents, driven by gradients in normal stress, upon the evolution of fold geometry in anisotropic, linearly-viscous, multi-layered materials. The layering consists of an alternating sequence of high viscosity, chemically mobile rock and lower viscosity, chemically immobile rock. In a natural analogue, the high viscosity, chemically mobile layers could be quartz rich whilst the low viscosity, chemically immobile layers could be mica rich The deformation is assumed to be incompressible, with temporarily and spatially evolving volume fractions of the mobile and immobile constituents. We present a large deformation formulation for a layered, viscous material.. The particle-in-cell finite element method combines many of the advantages of traditional finite elements with the geometrical flexibility of pure particle methods. The method is particularly suitable for problems involving very large deformation without the need for re-meshing.