Porosity and permeability changes in Pleistocene corals are controlled either directly or indirectly by marine and fresh-water diagenetic processes. These diagenetic events create as well as destroy pore space.
The transition of aragonite to calcite and accompanying precipitation of sparry calcite in voids are the major factors influencing porosity and permeability of the corals in the vadose zone. Porosity decreases primarily because of the growth of sparry calcite in pores, whereas permeability increases because of changes in pore aperture size that result from a fabric change associated with recrystallization. Mercury-injection-capillary-pressure data indicate that calcitic corals have larger and better sorted pore apertures than do aragonitic corals.