One of the major formations of the Northwest Cascades is the Darrington Phyllite. This unit is a former ocean floor mud that has been metamorphosed. The fine layers of silt and sand are highly contorted and folded.
But more than the folding and contortions of the original sediment, the Darrington Phyllite has more than sedimentary layering. The rock contains multiple metamorphic fabrics from its past deep burial and strain.