Ultracataclasite is a type of fault rock formed by intense mechanical grinding and crushing of rocks along a fault zone, resulting in a very fine-grained, cohesive rock. This material is significant in structural geology for understanding fault mechanics, earthquake processes, and the evolution of fault zones.
Source Sibson, R. H. (1977). “Fault Rocks and Fault Mechanisms.” Journal of the Geological Society, 133(3), 191-213.