USGS home Scientific Investigations Map 2940 

Pacific NW Geologic Mapping Project

Geologic maps of the North Cascades

TKcs-3. View south from east ridge of Mount Formidable [SRne]. Rocks of the Chelan Mountains terrane, including Cascade River Schist (TKcs), form foreground cliffs. Underlying metamorphosed Marblemount pluton (TKmd) in Old Guard Peak extends along jagged ridge into middle foreground. Sentinel Peak formed of Napeequa Schist (Kns) is cut by the Entiat Fault. These deep-seated metamorphic rocks were partly uplifted, and overlying rocks were eroded, before they were intruded by the Cloudy Pass batholith, a Miocene Cascade Arc pluton (Tcas) that forms Dome Peak and Spire Point in middle background. Further uplift and erosion, especially glacial erosion, preceded eruption of Glacier Peak volcano (Qcav) of the Cascade Magmatic Arc. Contacts (thin lines) and faults (heavy lines) dashed where approximately located and dotted where hidden in this view. This photo is figure 7 in the accompanying report (sheet 2). Photographed in 1958. View image without annotation
Other photos that show unit TKcs:

Previous Photo        Next Photo   

Photo Indices: Captions (Additional photos home) | Map | Young rocks and deposits | Older rocks west | Older rocks east