Pseudofaults resulting from compartmentalized Liesegang bands: update

Liesegang bands with apparent offset along fractures are common in some calcisiltite beds. Thin sections show, however, that primary laminations are not offset along the fractures. Following the development of fracture sets in the calcisiltite, the fractures were cemented by calcite. This formed polyhedral compartments of low-permeability calcisiltite bounded by impermeable walls of calcite. Liesegang bands formed when oxygen in ground water diffused into polyhedra containing soluble ferrous iron in pore water. Each joint-bounded polyhedral compartment behaved as an independent diffusion cell. Liesegang bands with nearly the same pattern and thickness tended to develop in adjacent compartments, but not at the same stratigraphic level; this resulted in the formation of pseudofaults.