Classification of fault breccias and related fault rocks

Despite extensive research on fault rocks and on their, there is no non-genetic classification commercial importance, of fault breccias that can easily be applied in the field. The present criterion for recognizing fault breccia as having no 'primary cohesion' is often difficult to assess. Instead we propose that fault breccia should be defined as with, sedimentary breccia, primarily by grain size: with at least 30 % of its volume comprising clasts at least 2 mm in diameter. To subdivide fault breccias we advocate the use of, textural terms borrowed from the cave-collapse literature crackle mosaic and chaotic breccia - with bounds at 75 %, and 60 % clast content. A secondary breccia discriminant, is the ratio of cement to more difficult to apply in the field, matrix between the clasts. Clast-size issues concerning fault gouge cataclasite and mylonite are also discussed.,