Fault gouge

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Fault gouge is an unconsolidated tectonite (a rock formed by tectonic forces) with a very small grain size. Fault gouge has no cohesion, it is normally an unconsolidated rock type, unless cementation took place at a later stage. Fault gouge forms in the same way as fault breccia, the latter also having larger clasts.^[1]

[edit] Origin

Fault gouge forms by tectonic movement along a localized zone of brittle deformation (a fault zone) in a rock. The grinding and mealing that results when the two sides of the fault zone move along each other results in a material that is made of loose fragments. First a fault breccia will form, but if the grinding continues the rock becomes fault gouge.