Surface Roughening and the Fractal Nature of Rocks

Abstract

The microstructure of sedimentary rocks is studied by small-angle neutron scattering for length scales between 5 and 500 \AA{}. In limestones and dolomites, we find that the pore surfaces are effectively smooth above 50 \AA{}, but there is evidence for roughening on shorter length scales. In sandstones and shales, the pore surfaces show fractal character due to the presence of clay. The fractal dimension is nonuniversal. We attribute these observations to impurity effects, which can lower the surface tension and maximize the surface area.