Formation. Crenulations form when an early planar fabric is overprinted by a later planar fabric. ... The angular intersection of the two foliations causes a diagnostic texture called a crenulation, which may involve folding of the earlier mica foliations by the later foliation.

What causes metamorphic banding?

The banding is usually due to the presence of differing proportions of minerals in the various bands; dark and light bands may alternate because of the separation of mafic (dark) and felsic (light) minerals. Banding can also be caused by differing grain sizes of the same minerals.

What are crenulation folds?

Crenulation cleavages are zones of mineral differentiation that are coincident with the limbs of microfolds in crenulated fabrics. They consist of subplanar domains of highly oriented micaceous material that constitute preferred sites of parting in the rock.