Formation and growth of normal faults in carbonates within a compressive environment

Abstract

Normal faults were initiated and grew through hierarchical formation of pressure-solution structures and their subsequent shearing in Cretaceous carbonates in the leading thrust front of Maiella Mountain, Italy. Through mapping in the field, we have documented the detailed architecture of faults with increasing slip values from a few millimeters to ∼50 m and have identified pretilting structural elements and four stages of fault development, each stage representing addition of a new structural element. The result is a conceptual model that begins with pretilting structures (bed-parallel and bed-perpendicular solution surfaces) that were reactivated in shear upon tilting of the beds at the frontal limb of the Maiella anticline. Slip on mechanical-layer boundaries and on bed-perpendicular solution surfaces resulted in oblique solution surfaces, linkage of solution surfaces, and fragmentation of rock. Oblique zones of fragmented rock in adjacent mechanical layers linked to form a continuous breccia and facilitated fault growth. These normal faults formed through mechanical processes strictly in a compressional regime.