Extensional fault cores in micritic carbonate – Case studies from the Gulf of Corinth, Greece

Abstract

The major Pisia and Doumena faults of the Corinth Rift, Greece, are both hosted by micritic carbonate rock. Their common fault elements are principal slip surfaces, layers of fault rocks, fault rock and host rock lenses, corrugations, and smaller shear and tension fractures. Along planar fault segments, a corrugated slip surface with an associated thin fault rock layer is formed. Well-developed down-dip corrugations indicate movement along the same surface over many fault increments. Bends/jogs in the faults are sites of complex structural relations, hosting frequent lenses, more porous fault rocks, and dense networks of fractures. Major jogs in the slip surfaces have both strike and dip-oriented undulating curvature that are associated with higher order fracture networks as well as frequent lenses. Fault core lens shapes of the Doumena fault show relationship of length vs. width of 3/2. Similarly, principal slip surfaces of the two faults show undulations with aspect ratios of amplitude vs. wavelength (1:19 and 1:14) in strike-direction, despite a prominent difference in down-dip geometry. The intrinsic deformation in fault cores of micritic carbonate supports a model in which fluids entered the core by damage zone fractures that are linked to the principal slip surface. Flow along the fault core was controlled by the fracture system of lenses, and thereby lens connectivity, but may have been hampered by flow-retarding fault rocks. The flow potential is especially well developed in fault bends and breached relays due to frequent lenses and well-developed fracture networks.