two planes forms an intersection lineation. This intersection lineation, L1-2 may approximate the plunge of F2 interference folds. The initial impact of a crenulation foliation may be cryptic, microscopic growth of new minerals at an angle to previous foliations. This may occur only in certain compositions of the rocks which favor growth of minerals under the P-T conditions at that time. In more brittle conditions, especially in highly micaceous rocks, a crenulation may appear as 'kink bands, where S1 foliations are kinked by the S2 foliation so that the original minerals are broken or deformed. This may not result in new mineral growth. Eventually, the crenulation foliation overprints the S1 foliation. In extreme cases, the S2 foliation will obliterate the previous foliation, especially in wet rocks which have compositions amenable to growth of minerals at that time. In this case, porphyroblasts may be the only means in which to observe earlier foliations, assuming they have inclusion trails of the S1 foliation. See also List of rock textures Metamorphism Rock microstructure Structural geology Shear (geology) References Vernon, Ron H., 2004, A Practical Guide to Rock Microstructure, Oxford University Press, Oxford. Structural geology Metamorphic rocks