Development and Petrophysical Properties of Faults in Carbonate Grainstones (San Vito Lo Capo Peninsula, Sicily)

Detailed field mapping and microstructural and textural analyses carried out in the San Vito Lo Capo peninsula (in north-western Sicily) allowed us to document failure modes and fault development in porous carbonate grainstones. We show that individual compactive shear bands represent the simplest fundamental shear structures, and that pressure solution processes often localize within previously developed compactive shear bands. In the Lower-Pleistocene carbonate grainstones of San Vito Lo Capo peninsula, composed of eroded carbonate and marl fragments, pressure solution processes localize mostly grain-to-grain, hence leading to the formation of zones of weakness which facilitate slip and the development of larger displacement. Finally, laboratory analyses of representative fault rock samples, also show that the structures described above have sealing capacity with respect to the host rock, and may compartmentalize any geofluid reservoir.