Pressure solution seams, once initiated as Intergranular Pressure Solution (IPS) at grain contacts, thicken through transverse growth (Figue 1a). A significant jump in PSS thickness occurs where remnants of grains in between neighboring sub-parallel IPS (Figure 1b) dissolve resulting in merging or coalescing of the PSSs (Figure 1c). Please see the link, 'Growth of Pressure Solution Seams.'

Figure 1. Thickening of Pressure Solution Seams. (a) Idealized Intergranular Pressure Solution Seams (PSSs) within a rock subjected to high enough normal stress. (b) Transverse and lateral growth of the individual seams. (c) Coalescing of neighboring sub-parallel PSS through disolving of the remnants of grains in between them resulting in a considerable jump in the thickness of the compound zone or cluster. From Nenna and Aydin (2011).