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Pacific NW Geologic Mapping Project

Geologic maps of the North Cascades

TKns-1. The southwest side of Elija Ridge, viewed from helicopter near Red Mountain [MBse] to the south, reveals a stack of fault plates. Late Cretaceous and early Tertiary Skagit orthogneiss (TKso) is overlain by probable Napeequa Schist (TKns?) along a low-angle normal fault. A second low-angle normal fault above the schist separates it from metamorphosed rocks of the Methow onlap assemblage (Pasayten Group, TKm), which is overlain by gneissic tonalite (TKto?). Textures within the gneissic tonalite indicate top-to-the south translation. The gneissic tonalite is probably bound by low-angle normal faults. Above the gneissic tonalite is more Napeequa Schist (TKns?), including an ultramafic body (TKnu). At right, a younger high-angle fault juxtaposes these rocks with structurally higher TKm and light-colored metatonalite (TKmo). The anomalous intrusive age of the metatonalite at 103 Ma is discussed in the technical pamphlet. The exposed face is about 3,000 ft (900 m) high. Faults dashed where approximately located. View image with annotation
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Photo Indices: Captions (Additional photos home) | Map | Young rocks and deposits | Older rocks west | Older rocks east