Mullions

Mullions developed in the Creston argillite near crest of an anticline in British Columbia. Mullions are fold-like features that develop during larger-scale folding of the contact between competent and incompetent layers. The hinge lines of the mullions define a lineation. Photo credit: Richard Stenstrom. Image from website: http://www.science.ubc.ca/~eoswr/slidesets/keck/keck.html