A useful theoretical model for studying some aspects of stratigraphical correlation is that of deposition in mosaic environments. The model is readily implemented using computer simulations based on the Voronoi diagram and produces lithosome geometries that are broadly comparable to those commonly seen in the field and on seismic sections. This model is restricted here to two-phase mosaics (e.g. sand/shale) and the lateral persistence of either phase can readily be determined from the computer simulations. This leads directly to measures of the lateral traceability of units of either phase in discontinuous surface outcrop and of reflector persistence in the subsurface. Because these measures are ultimately scaled in terms of the inherent length scale of the mosaic, they can be simply applied to real surface and subsurface data.