 They fall into the category of cataclastic rocks which are formed through faulting or fracturing in the upper crust.Cataclasites are distinguished from fault gouge, which is incohesive, and fault breccia, which contains coarser fragments.Cataclasites are composed of fragments of the pre-existing wall rock as well as a matrix consisting of crushed microfragments, which cohesively holds the rock together.