The efficiency of pressure solution depends on the grain size of the rock and is most intense in fine-grained materials. Fine-grained materials, corresponding to large total contact area, generally favor pressure solution because they host better diffusion. Based on theoretical considerations by Rutter (1983, Equation 1), the strain rate accommodated by pressure solution is inversely proportional to the cube of the grain diameter.

Equation 1. Governing equation of the strain rate of pressure solution. e is the strain rate in the direction of the applied stress; A is a dimensionless constant; L(alpha) is the phenomenology coefficient; sigma is the applied uniaxial stress; V(alpha) is the volume of the stressed solid; w is the effective thickness of the inter-granular diffusion window; and d is the grain diameter. From Rutter (1983).

Peacock and Azzam (2006) reported from a core in the Khuff Formation of Upper Permian and Lower Triassic carbonates in Abu Dhabi that stylolite in boundstones is of lower density (Figure 1a) and lower amplitudes (Figure 1b) than the finer rocks in the same formation. However, other than the boundstones, there is no tendency for more pressure solution in finer rocks, as seen in grainstone, packstone, wackestone, and mudstone.

Figure 1. Stylolite characteristics in different texture carbonates from a well log in Khuff Formation of Upper Permian and Lower Triassic age in Abu Dhabi, from Peacock and Azzam (2006). (a) Numbers of stylolites per meter. There is a tendency for more stylolites in finer rocks, so boundstones have fewer stylolites than wackestones. (b) Stylolite amplitudes (millimeters per meter of core). There is a tendency for more pressure solution in finer rocks, so pressure solution seams in the boundstones have suppressed amplitudes. From Peacock and Azzam (2006).