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Structure And Metamorphism Of The Magic Mountain – Johannesburg Mountain Area, North Cascades, Washington, Bernard E. Dougan

WWU Graduate School Collection

The orogenic history of the Cascades Crystalline Core is addressed in the study of a small, central region that straddles the Entiat fault on the southwest flank of the Skagit Gneiss. This region contains an arc-derived terrane with a preserved stratigraphy of volcanic, clastic and pelitic petrofacies of the Cascade River unit on a basement of sub-arc plutonics, the Marblemount Meta-Quartz Diorite. The Magic Mountain Gneiss, derived from the Marblemount arc, is inferred to have formed as a sub-volcanic sill-like pluton that intruded the protolith of the Cascade River unit In contact with the Cascade River unit is the Napeequa …