BOUDINAGE, FOLIATION

When compression acts layer normal on a laminated medium, internal boudinage may result. The boudinage results not from the differential stretching of a competent layer but from other inhomogeneities. This boudinage may also be en echelon if the compression departs from orthogonality to foliation. Asymmetric boudinage of foliation can also be used to determine sense of shear, and, in some rocks, important information about the P-T-deformation history can be learned from the minerals in the boudin necks.