Formation of gneiss domes in Okanogan Highlands. Maximum crustal deformation with faulting and folding. Strike-slip faults translate large portions of the Cascades, jumbling geologic units. Cascade magmatic arc initiated. North half of the state uplifted.
Geologic record consists of one small area of continental sediments.
Minor acidic intrusives. Marine sedimentary rocks in northern Puget Lowland. Chert-rich marine sandstones, mudstones, shales, and greenstone in central Cascades. Grabens with terrestrial clastic sedimentary rocks. Intermediate to silicic intrusive rocks.